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HLTAP301A Recognise healthy body systems in a health care context Reading 1: Apply knowledge of the basic structure of the healthy human body 1 © NSW DET 2007 2 © NSW DET 2007 Contents HLTAP301A Recognise healthy body systems in a health care context 1 Reading 1: Apply knowledge of the basic structure of the healthy human body 1 Contents 3 Introduction 4 Use accepted health terminology to describe the normal structure, function and location of the major body systems Health terminology 4 4 Apply a basic understanding of the fundamental principles of maintaining a healthy body Organisation of the body Internal cavities Body regions 9 9 14 15 Work with knowledge of the major components of each body system and their location in relationship to other structures Cardiovascular system Respiratory system Musculoskeletal system Nervous system Sensory system Integumentary (skin) system Gastrointestinal (digestive) system Urinary system Reproductive system Endocrine system Lymphatic and immune system 16 18 26 28 34 39 41 43 47 49 53 55 3 © NSW DET 2007 Introduction The human body is an amazing feat of biological architecture. It is designed to not only ensure its own survival, but the survival of the human species. The study of the human body is divided into two sections called anatomy and physiology. Anatomy is the study of the structure or parts that make up the body, whilst the physiology is concerned with their function. Working with human beings whether young or old, you need a basic understanding of the structure (anatomy) of the human body and how the body works (physiology). Understanding the human body’s normal functions, from the smallest cell in the body to the body as a whole, allows you to start to comprehend what happens to the person’s body through the ageing process as well as during illness. This knowledge can then be used to promote comfort, support and care of older people in their activities of daily living (ADLs). It will also assist you to understand signs, symptoms and the reasons for care and procedures Use accepted health terminology to describe the normal structure, function and location of the major body systems Communication skills are crucial to the delivery of quality care in the health and aged care setting. Understanding health/medical terminology is important in your work as an aged care worker. As you gain more knowledge and experience you will become familiar with and use health/medical terms when communicating with other health team members. You will also medical terms in your documentation. Health terminology Although health terminology can be sometimes hard to read and understand if you break the word down you can work out what it means. Many medical terms are a combination of smaller parts of words elements. Terminology is easier to understand when larger words can be broken up into smaller parts and elements. These elements are called prefixes, roots and suffixes 4 © NSW DET 2007 Some examples of common medical terms combing these different word elements are explained below The word hyperglycaemia means higher than normal glucose in the blood. Similarly, hypoglycaemia means lower than normal glucose in the blood. Common medical terms and their word elements Prefix hyper Root Suffix glyc + (high) + (glucose) aemia (blood) Hyperglycaemia (higher than normal glucose in the blood) Prefix hypo Root Suffix glyc + (high) + (glucose) aemia (blood) Hypoglycaemia (lower than normal glucose in the blood) When larger words are broken down into smaller parts it is easier to work out the meaning of a word. Learning these word elements will help you work out the meanings of difficult medical terms. Definitions of prefix, root and suffix Word element Description Prefix Can be added to the beginning of root words to add further meaning Root word The essential meaning of the term Suffix Can be added to the ending of root words to add further meaning Some common health terminology Word root, prefix or suffix Meaning aathro- joint adip- fat -algia pain angio- vessel anterior toward the front- ventral 5 © NSW DET 2007 cardi-, cardio-, cardia- heart cephal- head cerebr-, cerebro- brain cut- skin dent- teeth derm- skin distal away from point of attachment -ectomy excission gastr- stomach genio- chin glosso-, -glossus tongue gyne-, gyno- woman hepato- liver histo- tissue homeo-, homo- same hyper- above hypo- under hyster- uterus inferior lowermost or below -itis inflammation lateral toward the side of the body lip-, lipo- fat mast-, masto- breast medial nearest to the centre of the body myo- muscle nas- nose nephr- kidney oculo- eye ophthalm- eye -opia eye -osis state osteon-, osteo- bone oto- ear patho-, -path, -pathy disease -phasia speech 6 © NSW DET 2007 Phleb- vein Podo- foot posterior toward the back or dorsal proximal closest point of attachment rhin- nose spino- spine superior uppermost or above -stomy opening thorac- chest -tomy cut uro-, -uria urine vas- vessel Abbreviations There are many abbreviations related to working in the health and aged care environment become familiar with some of these. The following tables (insert table numbers) provide a list of common abbreviations, symbols and acronyms as well as their meanings. This list is not exhaustive but shows those most frequently used. Commonly used abbreviations Abbreviation Meaning abdo abdomen Ht height lab laboratory NAD nil abnormalities detected Neg or -ve negative obs observations Pos or +ve positive Wt weight Common symbols Symbol Meaning ♂ male ♀ female # fracture 7 © NSW DET 2007 < less than > more than Δ disease or disorder . /l one . /ll twice . /c with Px treatment Common acronyms Acronym Meaning ADK activities of daily living BD twice a day BGL blood glucose level BKA below knee amputation BNO bowels not opened BO bowels opened BP blood pressure CCF congestive cardiac failure CVA cerebral vascular accident CXR chest x-ray DNR or NFR do not resuscitate or not for resuscitation ECG electrocardiogram EEG electroencephalogram GIT gastrointestinal tract HRS hours IDC indwelling catheter IV intravenous MI mycardial infarcation MS multiple sclerosis NBM nil by mouth PAC pressure area care PEG percutaneous endoscopic gastrostomy PRN as required PVD peripheral vascular disease 8 © NSW DET 2007 ROM range of motion SOB shortness of breath SPC supra-pubic catheter TDS three times per day THR total hip replacement TIA transient ischaemic attack TPR temperature, pulse and respiration UA urinalysis UTI urinary tract infection The main purpose of documentation is to successfully communicate information, it is important that everyone can read and understand what is written. Using abbreviations that not all workers are familiar with can lead to the omission of care or incorrect care being given to an older person. If unfamiliar abbreviations are found in the workplace documentation, the acceptable abbreviations list should be checked. If the abbreviation does not appear on the list, the supervisor should be contacted for further clarification. Apply a basic understanding of the fundamental principles of maintaining a healthy body The human body is an extremely complex organism. The body is made up of many different systems that work together to keep us healthy. All body systems start from simple chemicals which combine to make the basic units of life, cells. Organisation of the body The human body is organised into various levels that begin at the very small and basic and come together to form the complete body whose different parts work in unison. This can be seen as a kind of ‘ladder’ going from the basic (simple chemicals, atoms) to the very complex. At the simplest level, the body is comprised of atoms. As seen in the flowchart following atoms combine to form molecules to form cells, to form tissues, to form organs, to form body systems, to form the human body. 9 © NSW DET 2007 From atoms to the human body The human body is built from tiny atoms to major organ systems Organisation of the body from chemical level to cellular level, to tissue level, to organ level, to system level, to the human body Cells The basic unit of body structure is the cell. All cells need food, water, and oxygen to live and function. As cells use or metabolise food and oxygen 10 © NSW DET 2007 they give off carbon dioxide and other wastes. The cell is comprised of the cell membrane, which is the outer covering; it encloses the cell and helps it hold its shape. The nucleus is the control centre; it directs the cell’s activities. Cytoplasm surrounds the nucleus. Organelles are structures that are suspended in the cytoplasm. The protoplasm refers to all structures, substances and water within the cell. Chromosomes are threadlike structures within the nucleus. Each cell has 46 chromosomes. Chromosomes contain genes, which determine our physical and chemical makeup. Features of cells include: the cell is the most basic unit of life there are cells that are organisms themselves, such as bacteria cells there are cells that only function when part of a larger organism in the body, there are brain cells, skin cells, liver cells, blood cells and many more all of the cells have unique functions and features. Although cells may be very different and highly specialised, they all have the same basic structure. They all have: an outer covering called the membrane a main substance called the cytoplasm a control centre known as the nucleus organelles dispersed within their cytoplasm. The cell membrane protects the cell and regulates the passage of materials into and out of the cell. The nucleus is the control centre of the cell. DNA, which makes up the genes, is found within the chromatin granules and within the nucleolus is the RNA. Organelles, which are structures found in the cytoplasm, are the: mitochondria, the ‘powerhouse’ of the cell, function in cellular metabolism and respiration endoplasmic reticulum produces proteins and lipids and transports these substances within the cell lysosomes function in intracellular digestion and form the ‘selfdestruct’ system of the cell golgi complex concentrates some secretions, adds carbohydrates to some secretions and packages secretions for export from the cell 11 © NSW DET 2007 vacuoles are small cavities within the cell used to store secretions or waste products centrioles, cilia and flagella are composed of microtubules o centrioles are contained in the centrosome and are involved in mitosis (cell division) o cilia aid in the movement of materials outside the cell. For example, trapping of dust particles in the respiratory tract. o flagella are important in the locomotion of sperm cells. The functions of the cell include: 1. Respiration – all cells require oxygen to metabolise food. 2. Ingestion and assimilation – cells are able to select chemicals from the surrounding fluid for their structure. 3. Growth and repair – cells can synthesise new cytoplasm so that growth can occur and repair worn out parts. 4. Excretion – waste products are eliminated into surrounding tissue to be transported by the blood for elimination via organs. 5. Irritability and activity – cells are able to respond to stimuli. For example a stimulus causes a muscle to contract or relax. 6. Metabolism – cells are able to break down and use substances from food as fuel. 7. Reproduction – cells reproduce by simple division but some cells can never be replaced once destroyed. For example, central nervous system cells. Tissues Groups of cells form tissues and there are four main types. The structure of tissues reflects their function. Types Function Example Epithelial Protection Skin Connective Support Bones Muscular Movement Skeletal Nervous Communication Brain Epithelial tissue This tissue covers the body surfaces and lines its cavities. Some specialise to form glands. The functions of epithelial tissue include: protection 12 © NSW DET 2007 absorption secretion excretion surface transport reception of sensory information. A gland is one or more epithelial cells specialised to produce and discharge substances. Endocrine glands secrete have no ducts and secrete hormones directly into the bloodstream, for example pituitary gland. Exocrine glands release their secretions through ducts, for example salivary and sweat glands. Connective tissue This tissue joins other tissues of the body together, supports the body and protects underlying organs. Some main types are: ordinary connective tissue — subcutaneous tissue and collagen adipose tissue — stores fat cartilage — protects joints and supports soft tissues bone — rigid supporting tissue of the skeleton blood — lymph and lymphoid tissue—produce blood cells Muscular tissue Muscle is composed of cells specialised to contract. Skeletal muscle is striated (striped) and is under voluntary control. Cardiac muscle is present only in the walls of the heart, is striated and is controlled by involuntary nerve messages from the brain. Smooth muscle, also involuntary, is responsible for movement of food through the digestive tract, and changing the diameter of blood vessels. Nervous tissue Nervous tissue forms the brain, spinal cord and the nerves. The basic cell is called the neuron. Specialised to receive stimuli and send impulses from one part of the body to another. 13 © NSW DET 2007 Organs Groups of tissues come together to form organs. For example the heart is made up of cardiac muscle and nervous tissues, held together with connective tissues and lined with epithelium. Each organ has a specific function. Organ Function Heart Circulation Stomach Digestion Brain Communication/coordination Uterus Reproduction Body systems Several organs working together form a system. For example the urinary system is made up of the kidneys, bladder and ureters. System Organs Cardiovascular Heart, blood, vessels Respiratory Nose, pharynx, trachea, bronchus, bronchiole, lungs, alveoli Musculoskeletal Muscles, joints, bones Integumentary Skin Nervous Brain, spinal chord, nerves Gastrointestinal/Digestive Tongue, oesophagus, stomach, liver, pancreas, gall bladder, small intestine, large intestine, rectum, anus Urinary Kidneys, ureters, bladder, urethra Reproductive Male: Testes, scrotum, vas deferens, seminal vesicle, prostate, ejaculatory duct, urethra, penis, glans, perineum Female: Ovaries, fallopian tubes, uterus, cervix, vagina, labia, urethra, clitoris, perineum Endocrine Glands: pituitary, hypothalamus, pineal, parathyroid, thyroid, adrenals, pancreas, gonads: ovaries ♀; testes ♂, and their hormones. Lymphatic/Immune Lymph glands and vessels, lymph, lymphocytes, T and B cells. Internal cavities The body has two (2) sets of internal cavities that provide different degrees of protection to the organs that lie within them. These are the: 14 © NSW DET 2007 1. Dorsal cavity is divided into the cranial cavity, containing the brain, and the spinal cavity, containing the spinal cord. Organs in the dorsal cavity coordinate the body’s functions via the nervous system. 2. Ventral cavity which comprises the thorax (chest) – this encases the heart and the lungs and the abdominopelvic cavity which encases our abdominal organs and those of our reproductive system. Organs in the ventral cavity work to maintain a constant internal environment, or homeostasis. Body cavities Diagram of body cavities including cranial thoracic, abdominal, spinal and pelvic Body regions The body is also divided into regions. Examples of these include the: epigastric region — which lies below the bottom of the breastbone and above the umbilicus (belly button) inguinal region — which lies within the groin 15 © NSW DET 2007 cervical region — which lies at the back of the neck gluteal region — which lies in the area of the buttocks. Work with knowledge of the major components of each body system and their location in relationship to other structures There are 11 body systems, each performing specific tasks. They are: cardiovascular system respiratory system musculoskeletal system nervous system sensory system integumentary system gastrointestinal system urinary system immune system endocrine system reproductive system. 16 © NSW DET 2007 Systems overview Diagram showing systems overview: cardiovascular system, respiratory system, skeletal system, muscular system, nervous system, integumentary system, gastrointestinal system, urinary system, lymphatic system, endocrine system, reproductive system 17 © NSW DET 2007 Cardiovascular system The cardiovascular system is one of the major body systems. It transports oxygen, carbon dioxide, waste products, nutrients and hormones to and from various parts of the body. The cardiovascular system is made up of the heart, the blood vessels (arteries and veins and capillaries) and blood. The heart has major vessels that return deoxygenated blood to the right side of the heart (travels back to the heart from the body), and major vessels that carry oxygenated blood away from the left side of the heart to all the parts of the body, including the heart itself. Heart The heart is a hollow organ about the size of a fist and is composed of special muscle tissue (cardiac muscle). It lies under the breast bone in the centre of the cardiothoracic cavity. In the average lifetime the heart beats 250 million times and pumps 340 million litres of blood. The heart is a sophisticated pump that is controlled by an electrical current that is initiated in the brain. Location of the heart and the major vessels that supply blood to the heart Drawing showing superior and inferior vena cava, aorta, heart, lungs The heart is divided into a left and right side by a muscular wall called the septum and has four chambers. Heart chambers and valves The chambers of the heart include the: 18 © NSW DET 2007 right atrium which receives deoxygenated blood (low in oxygen) from all over the body right ventricle receives blood from the right atrium and sends it to the lungs via the pulmonary artery to become oxygenated and get rid of carbon dioxide left atrium receives oxygenated blood from the lungs and sends it to the left ventricle left ventricle receives blood from the left atrium and sends it out to the body via the aorta. The heart wall consists of three layers—the endocardium is the inner lining, the myocardium is the muscle layer and the pericardium is the outer covering. The chambers of the heart are separated by valves: tricuspid valve is located between the right atrium and right ventricle bicuspid (mitral) valve is located between the left atrium and left ventricle pulmonary valve is between the right ventricle and the pulmonary artery aortic valve is between the left ventricle and the aorta The major vessels that carry blood to and from the heart are: inferior vena cava conveys deoxygenated blood (blood low in oxygen) from the lower extremities of the body to the heart superior vena cava coveys deoxygenated blood from the upper extremities of the body to the heart aorta conveys oxygenated blood (blood high in oxygen) away from the heart 19 © NSW DET 2007 Structures of the heart Illustration showing the position of the structures of the heart including the aorta, ventricles, valves Blood vessels The cardiovascular system consists of arteries and veins and capillaries. Arteries carry oxygenated blood to the cells of the body; veins carry deoxygenated blood away from the cells. Arteries Arteries are tubes that carry oxygenated blood (high in oxygen) away from the heart. Arteries have thick, muscular, elastic walls. They branch off forming arterioles with thinner walls that then become capillaries. Arteries carry blood rich in oxygen and nutrients. Blood that comes from a wound where there is damaged (due to action of heart pumping) is bright red and spurts. The aorta is the largest artery and as it leaves the heart it branches into smaller arteries, eventually they become capillaries. Veins Veins carry deoxygenated blood (low in oxygen) from the cells back to the heart where it is pumped to the lungs so that the blood can pick up more oxygen. The veins have one-way valves that help move the blood toward the heart. Veins have thinner muscular walls. They carry blood back to the heart that is low in oxygen and high in carbon dioxide, a waste product. Blood that comes from a wound where a vein is damaged (due to action of heart pumping) is dark red (deoxygenated) and oozes or runs out (does not spurt). 20 © NSW DET 2007 Arteries Veins Venous and arterial circulation Diagrams of veins and arteries throughout body Capillaries Capillaries are very small vessels that surround the cells of the body and facilitate the movement of oxygen and nutrients into the cells and carbon dioxide and waste products away from the cells. 21 © NSW DET 2007 Capillaries Diagram showing distribution of capillaries around veins and arteries Blood Blood is made up of a liquid (plasma) and cells. Blood is connective tissue, a red body fluid made up of liquid (plasma) and cells. The body contains five to six litres of blood. Fifty-five percent of the blood is plasma. Drawing of a tube with plasma in half of the tube, a small bit of white blood cells and platelets and the rest red blood cells Components of blood Plasma Plasma is a straw coloured watery fluid in which the blood cells are suspended. 22 © NSW DET 2007 It contains antibodies (gamma globulin) and antitoxins, plasma proteins, mineral salts, nutrients, waste products such as urea and creatinine, gases such as oxygen and carbon dioxide, hormones and enzymes. The blood cells float in the plasma. They are produced in the bone marrow and lymphatic tissues of the body. The bone marrow, liver and spleen destroy worn-out blood cells. Blood cells There are three types of blood cells. 1. Erythrocytes or red blood cells (RBC)—carry most of the oxygen and small amounts of carbon dioxide. Haemoglobin carries the oxygen molecule and gives blood its colour. There are approximately 5 million RBC per cubic millimetre of blood and the average life span is 100—120 days. Red blood cells Red blood cells 2. Leucocytes or white blood cells (WBC)—help fight infection as they can attack micro-organisms. There are 7,000—8,000 WBC per cubic millimetre. White blood cells White blood cells 3. Thrombocytes (platelets) — are parts of cells which plug small leaks in the walls of blood vessels and initiate blood clotting. There are 200,000 to 400,000 per cubic millimetre. 23 © NSW DET 2007 Platelets Diagram of platelets For more information on blood and blood products visit the Australian Red Cross Blood Service website at http://www.arcbs.redcross.org.au/ Flow of blood through the heart The correct term for contraction of the heart is systole. This is followed by relaxation of the heart called diastole. One systole and diastole form the cardiac cycle. A cardiac cycle takes only 0.8 seconds and during this time the following events occur. First, the upper chambers, or atria, of the heart relax and fill with blood as the lower ventricles contract, forcing out blood through the aorta and pulmonary arteries. Next the ventricles relax, allowing blood to flow into them from the contracting upper chambers. Then the cycle is repeated; this happens approximately 70 to 80 times per minute. The rate and rhythm of the heart is regulated by the conduction system that is made up of specialised neuromuscular tissue that sends out impulses. The impulses begin at the Sino-Atrial (SA) node in the right atrium and spread across the two atria. The atria then contract and the impulses from the S-A node reach the Atrio-Ventricular (AV) node in the right atrium. Messages from the A-V node then travel down the Bundle of His in the septum and continue through the Purkinje fibres to the walls of the ventricles. An electrocardiogram, or ECG, is a diagnostic test that records the electrical impulses of the heart. The blood flows around the body continuously due to the regular beat of the heart. Beginning at cells, the passage of blood is as follows: 24 © NSW DET 2007 Diagram of the flow of blood through arteries and veins Diagram of the flow of blood through arteries and veins As seen in the following diagram blood cell arrives deoxygenated into the right atrium and passes into the right ventricle through the tricuspid valve. The blood cell leaves the heart through the pulmonary valve into the pulmonary artery where it travels to the lungs to be oxygenated. Blood cells enter right atrium and pass into right ventricle, and leave through the pulmonary artery where it travels to the lung Diagram showing entry of blood cells into right atrium and passage into right ventricle, and leaving through the pulmonary artery where it travels to the lung 25 © NSW DET 2007 The oxygenated blood cell returns to the heart through the pulmonary vein into the left atrium. The blood cell moves into the left ventricle through the mitral valve. The blood cell then moves from the heart into the body through the aorta passing through the aortic valve. Oxygenated blood cells return to the heart through the pulmonary vein into the left atrium and then move from the heart into the body through the aorta Diagram showing oxygenated blood cells return to the heart through the pulmonary vein into the left atrium and then moving from the heart into the body through the aorta Respiratory system The respiratory system is composed of various structures and organs that ensure that the body is able to maintain its internal environment through the exchange of air between the lungs and the atmosphere. In order to survive the body needs a constant supply of oxygen, which it obtains from the air. The body also needs to dispose of carbon dioxide, made as a waste product from the process of cell metabolism. The ingestion of oxygen and the discarding of carbon dioxide occurs through the process of respiration or breathing. Structure of respiratory system The respiratory system is comprised of the: nose 26 © NSW DET 2007 nasopharynx mouth sinuses larynx trachea bronchi lungs alveoli The respiratory system Diagram showing labelled parts of the respiratory system The respiratory system contains the upper and the lower respiratory tracts. The upper respiratory tract contains the respiratory organs located outside the chest cavity: the nose and the nasal cavities, pharynx, larynx and upper trachea. The lower respiratory tract consists of organs located in the chest cavity: the lower trachea, bronchi, bronchioles, alveoli and the lungs. The lungs have lobes 3 lobes in right lung and 2 lobes in left to accommodate the heart. The lower parts of the bronchi, the bronchioles and alveoli, are all located in the lungs. The alveoli are the point at which gas exchange takes place. The pleura are a membrane that covers the lungs. 27 © NSW DET 2007 The muscles that form the chest cavity are also part of the lower respiratory tract. The respiratory centre in the brain, which is located in the medulla oblongata, regulates breathing. Function of respiratory system The function of the respiratory system is to supply oxygen and to remove carbon dioxide from cells. Oxygen is needed by cells to produce heat and energy. In using oxygen, the cells produce carbon dioxide as waste. Inhaled air is moistened and warmed as it passes through the upper respiratory tract—the nose, the pharynx and the larynx. The clean air passes on through the lower respiratory tract—the trachea, bronchi, lungs and the alveoli where the exchange of gases takes place. Respiration Respiration involves the passage of air in and out of the lungs. Air passes from nose to the pharynx to the larynx to the trachea to the left and right bronchus to the bronchioles to the alveoli (where a gas exchange takes place and oxygen and carbon dioxide are exchanged in the pulmonary capillaries) Air enters the body via the nasal passages, where it is warmed, moistened and filtered. Air then passes down through the pharynx and into the larynx and trachea. The air continues into the right and left bronchi and then into the lungs. In the lungs the bronchi then branch into smaller bronchioles, that each has air sacs called alveoli, attached to them. The exchange of oxygen and carbon dioxide takes place at this level, between the alveoli and the blood capillaries. Through this process oxygen enters the bloodstream and can be transported around the body. Musculoskeletal system The musculoskeletal system consists of the bones, muscles, ligaments and tendons The skeletal system The skeletal system is comprised of bones and joints and provides the basic supporting structure of the body. It consists of the joined framework of bones called the skeleton. 28 © NSW DET 2007 Major bone structures of the body Diagram of the major bone structures of the body Structure of musculoskeletal system Bones There are 206 bones in the human body. Bone is a dry, dense tissue composed of a calcium-phosphorus mineral and organic matter and water. Bone is covered with a living membrane called the periosteum. The periosteum contains bone-forming cells, the osteoblasts. The centre of bone contains marrow where blood vessels, fat cells and tissue for manufacturing blood cells are all found. There are four main shapes of bones: flat, eg ribs irregular, eg vertebrae short, eg hand (carpals) long, eg upper arm (humerus). 29 © NSW DET 2007 Joints A joint is an area where two or more bones are in contact with each other. Joints allow movement. The bones forming the joint are held together by ligaments. There are three types of joints: 1. fibrous or immovable eg skull 2. cartilaginous or slightly moveable eg vertebrae 3. synovial or freely movable: ball and socket eg hip hinge eg elbow. gliding eg carpals at wrist pivot eg radius and ulna. There are certain terms that are used to describe the movement of bones: abduction—movement away from the body adduction—movement towards the body flexion—bending a limb towards the body extension—extending a limb away from the body rotation—movement around a central point. You have learnt the names of the various joints of the body, but there are also words that describe the various directions in which limbs move. 30 © NSW DET 2007 Movement of the joints Diagrams showing movements of the joints 31 © NSW DET 2007 The muscular system The muscular system allows us to move and you will need to learn about the muscles of the body in order to understand how this system contributes to the overall design of the human body. The human body is composed of over 500 muscles working together to facilitate movement. It is very important to understand the muscular system and how it works in conjunction with the skeletal system to allow us to move and maintain our posture. The major function of the muscular system is to produce movements of the body, to maintain the position of the body against the force of gravity and to produce movements of structures inside the body. Structure of musculoskeletal system Tendons attach muscle to bone. There are 3 types of muscles: 1 skeletal (voluntary) muscles are attached to bone by tendons 2 smooth (involuntary) muscles control the actions of our gut and blood vessels 3 cardiac muscle in the heart. Muscles contract (shorten) and relax in response to chemicals and the stimulation of a motor nerve. Movement occurs when muscles contract or shorten, pulling the bones with them. Muscles work in pairs; when one shortens, the corresponding muscle lengthens. Some examples of muscles are the triceps, deltoid and the biceps in the upper arm and the gluteal muscle, the hamstrings and the quadriceps in the buttocks and the top of the 32 © NSW DET 2007 Major muscles group — anterior view Diagram of major muscles group — anterior view 33 © NSW DET 2007 Major muscles group — posterior view Diagram of major muscles group — posterior view Function of musculoskeletal system The function of the musculoskeletal system is to: protect and support the internal structures and organs of the body allow movement give shape to the body produce blood cells store calcium and phosphorus. Nervous system The nervous system is responsible for coordinating all of the body’s activities. It controls not only the maintenance of normal functions but also the body’s ability to cope with emergency situations. Function of nervous system The nervous system has three general functions: a sensory function, an interpretative function and a motor function. 1. Sensory nerves gather information from inside the body and the outside environment. The nerves then carry the information to central nervous system (CNS). 2. Sensory information brought to the CNS is processed and interpreted. 3. Motor nerves convey information from the CNS to the muscles and the glands of the body. Structure of nervous system The nervous system is divided into two parts: 1. the central nervous system consisting of the brain and spinal cord. These structures are protected by bone and cushioned from injury by the cerebrospinal fluid (CSF) 2. the peripheral system which connects the central nervous system to the rest of the body. 34 © NSW DET 2007 The central nervous system Diagram of central nervous system Central nervous system These structures are protected by bone and cushioned from injury by the cerebrospinal fluid (CSF). Brain The brain is a mass of soft nerve tissue, which is encapsulated within the skull. It is made up of grey matter, mainly nerve cell bodies, and white matter which are the cell processes. The grey matter is found at the periphery of the brain and in the centre of the spinal cord. White matter is found deep within the brain, at the periphery of the spinal cord and as the peripheral nerves. The brain is divided into: Cerebrum – the largest part of the brain. It is the centre for thought and intelligence. It is divided into right and left hemispheres. The right controls movement and activities on the left side of the body. The left controls the right side of the body. Within the cerebrum are areas for speech, hearing, smell, sight, memory, learning and motor and sensory areas. Cerebral cortex – the outside of the cerebrum. Its function is learning, reasoning, language and memory. Cerebellum – lies below the cerebrum at the back of the skull. Its functions are to control voluntary muscles, balance and muscle tone. 35 © NSW DET 2007 Medulla – controls heart rate, breathing, swallowing, coughing and vomiting. Together with the pons and the midbrain, the medulla forms the brainstem that connects the cerebrum to the spinal chord. The different sections of the brain Diagram of different sections of the brain Lobes of the brain It is important to have an understanding of how the brain functions and which parts control our functioning and behaviour. For example, when a casualty suffers from a stroke, the part of the brain that is affected controls function. If it is the frontal lobe, speech, thought and movement may be affected. 36 © NSW DET 2007 The different quadrants of the brain Diagram of different quadrants of the brain The spinal cord The spinal cord is about 45 cms long, extending from the medulla down to the second lumbar vertebrae. It acts as a message pathway between the brain and the rest of the body. Nerves conveying impulses from the brain, otherwise known as efferent or motor nerves, travel through the spinal cord down to the various organs of the body. When the impulses reach the appropriate level they leave the cord to travel to the’ target organ. Sensory or afferent nerve impulses also use the spinal cord to travel from various parts of the body up to the brain. Parts of the spinal chord Diagram of the spinal chord system The peripheral system connects the central nervous system to the rest of the body. The main divisions of the Peripheral Nervous System are: The autonomic nervous system – which controls the automatic functions of the body: the heart, smooth muscle (organs) and glands. It is divided into the ‘fight-or-flight’ system and the ‘resting and digesting’ system. The somatic nervous system –which allows us to consciously or voluntarily control our skeletal muscles. The somatic system contains 12 cranial nerves and 31 spinal nerves. Nerves –which are made up of special cells called neurons. Neurons are comprised of a dendrite, a cell body and an axon. Impulses travel to the dendrite into the cell body and then onto the axon. A special 37 © NSW DET 2007 sheath called myelin, which increases the conductivity of the neuron, covers some nerves. As messages travel from one neuron to the next they move across a synapse. At each synapse there is a chemical called a neurotransmitter. At various parts of the body specific neurotransmitters facilitate communication, for example dopamine (motor function), serotonin (mood) and endorphins (painkillers). Sensory neurons carry messages from a receptor to the brain. The brain then interprets the message. Motor neurons then send the message to an affector in muscles and glands. Receptor (sensory organ) sends a signal to the sensory neuron which sends a signal to the brain/spinal chord which sends a signal to the motor neuron which sends a signal to the affector (muscle/gland). The neurone The basic unit of the nervous system is a specialised cell called the neurone. These nerve cells make up a massive network of specialised cells that transmit messages, very rapidly, from one part of the body to another. Information is transmitted via electrical impulses. The neurone is comprised of a nerve cell and its adjoining processes called an axon and dendrites. Every nerve cell has one or more processes attached to it. Electrical impulses enter the neurone via the dendrites and leave via the axon. The space between the axon of one cell and the dendrites of another is called a synapse. Specialised chemicals called neurotransmitters help conduct impulses through the synapse onto the next cell. Structures of the neurone Diagram showing structures of the neurone 38 © NSW DET 2007 Sensory system Our sensory system provides information about our internal and external environment and assists in communication. We have both special senses and general senses. The special senses are localised in a specific area of the body, whereas the general senses found throughout the body. Special senses include vision, hearing, equilibrium, smell and taste. General senses include pressure, temperature, pain, touch and a sense of position. Taste – the tongue The receptors for taste lie in the tongue and are able to identify four types of taste: sweet, salty, bitter, sour. These taste ‘pores’ are found on papillae on the tongue and when they are stimulated by chemicals in the saliva they send impulses to the brain to be interpreted by a specific area of the cortex. Smell – the nose The receptors for smell are located in the superior aspect of each nasal cavity. Sniffing helps bring more air (containing odours) over the olfactory mucosa. Olfactory neural pathways are closely linked to the limbic system: odours can vividly recall memories and arouse an emotional response. Note: Taste and appreciation of foods is influenced by the sense of smell and the temperature and texture of foods. Hearing and balance – the ear The ear is divided into three main areas: the external ear; the middle ear; and the inner ear. The outer and middle ear is involved in hearing only. The inner ear functions in both balance and hearing. The external ear is composed of the pinna and the external auditory canal. In the walls of the external auditory canal are glands that secrete earwax or cerumen. Sound waves entering the external auditory canal eventually hit the eardrum or the tympanic membrane and cause it to vibrate. The eardrum separates the outer and the middle ear. The middle ear is a small space containing the eustachian tube and three small bones called the ossicles. The eustachian tube connects the middle ear and the throat. The ossicles amplify sound received from the eardrum and transmit it to the inner ear. The inner ear consists of the semi-circular canals and the cochlea, which contains fluid. In the cochlea, fluid carries sound waves received from the middle ear to the auditory nerve. The auditory nerve carries the message to the brain. The semi-circular canals are involved in balance. They sense the head’s position and changes in position and send messages to the brain (Herlihy et al 2000). 39 © NSW DET 2007 The ear Diagram showing parts of outer (external), middle and inner ear Vision – the eye The eye is a hollow sphere. The accessory structures of the eye include the extrinsic eye muscles, the tear (lacrimal) glands and ducts, the eyelids, the eyelashes and the conjunctiva. Light rays from a distant object are nearly parallel as they reach the eye and can be focused without change to the shape of the lens (convex). Diverging light rays from close objects require that the lens bulge more to focus the image more sharply on the retina. This ability of the eye to focus specifically for close objects is called accommodation. The image formed on the retina as a result of the lightbending activity of the lens is a real image — that is, it is reversed, upsidedown and smaller than the object. 40 © NSW DET 2007 The eye Diagram showing interior and exterior view of the eye Integumentary (skin) system The skin (also known as the integumentary system) covers the body and is the body’s largest organ. Different parts of the body have a different thickness of skin. For example, the skin on the soles of your feet is thicker than the skin on your face. Structure of integumentary system The skin is made up of three layers – two of these are skin layers and one is composed of fatty tissue. The two skin layers are the epidermis and dermis (see figure below) 41 © NSW DET 2007 Structure of the skin Diagram showing structure of the skin Function of integumentary system The skin functions as a protective covering—the skin protects everything underneath it and plays a major role in homeostasis. Another function is in maintaining the internal body temperature. It is also a major means of communication through touch and sensation. Protection The skin surface provides a tight, waterproof barrier and prevents potentially harmful organisms from entering the body. It also protects internal organs from external injury. The skin helps fight infection and protects against infection as long as it remains intact. The waterproof quality of the outer layer prevents excessive water absorption and abnormal water loss from the body, reducing the risk of dehydration. Temperature regulation The skin plays a major role in maintaining the internal body temperature because blood vessels can dilate or constrict. When the body temperature starts to rise, the blood vessels respond by dilating and increasing blood flow to the body surface, bringing inner heat to the surface. The sweat glands secrete fluid onto the skin, and it is the evaporation of this fluid that cools the body. When the body temperature starts to falls, the blood vessels 42 © NSW DET 2007 respond by constricting and decreasing blood flow to the body surface, reducing heat loss through the skin. The sweat glands inhibit the release of fluid, and evaporation from the skin is reduced to help the body retain heat. Body temperature Body temperature is the balance between the amount of heat produced and the amount of heat lost by the body. Body temperature remains fairly stable. Factors affecting body temperature are age, weather, exercise, emotions, stress, pregnancy, the menstrual cycle and illness. The normal body temperature range for an adult is between 36.0. – 37.2 ºC. A subnormal temperature reading would be considered less than 36 ºC if measured at the oral or axillary site. Sensory input The skin contains nerve endings that are sensitive to touch, pressure, vibration, pain and temperature. These nerve endings respond to each of these sensations and send messages to the brain to alert us. For example, if you touch a hot object with your hand, your immediate and automatic reaction will be to remove your hand from the heat source to avoid injury. Fluid and electrolyte balance The skin helps regulate the fluid and electrolyte balance by eliminating water and small amounts of salts through the sweat glands. The skin, in the presence of sunlight, begins the process of forming vitamin D, a substance required to absorb calcium and phosphates from food. It is the cells in the epidermis (melanocytes) that are responsible for this process. Gastrointestinal (digestive) system The human body needs energy, to be able to perform all the vital functions that are part of living. The gastrointestinal or digestive system converts the food that we eat into a form that can be processed and used as energy for all the activities carried out by the body. The type of foods that we ingest has an effect on the way that it is processed in the body and the amount of energy that is produced. As food passes through the digestive tract it is broken down, both physically and chemically into a form that can be absorbed into the bloodstream and used by the body for energy. Those particles that are unable to be digested are excreted in the form of faeces. 43 © NSW DET 2007 Gastrointestinal system Graphic showing the position of the mouth, liver, gall bladder, small intestines, stomach, pancreas and large intestines Structure of gastrointestinal system There are two main groups of organs and these are: 1. Gastrointestinal tract (GIT) (also called the alimentary canal) extends from the mouth to the anus. 2. Accessory structures which assist in the mechanical and chemical breakdown of food—these include teeth, tongue and glands lining the GIT. Mouth The process of digestion begins in the mouth where food is chewed until it reaches a consistency whereby it can be swallowed. The following accessory structures aid this early stage of digestion: Tongue – a muscle that is covered by tastebuds. It assists the process of chewing and manoeuvres food to a position where it can be swallowed easily. Salivary glands – begin the process of chemical digestion through the secretion of the enzyme, salivary amylase. This enzyme begins the process of breaking down carbohydrates. Saliva also moistens food which helps it to be swallowed more easily. 44 © NSW DET 2007 Teeth – break food down mechanically into smaller particles that may be ingested more easily. Pharynx – allows the passage of both food and air. Oesophagus – tube that leads to the stomach. Oesophagus The oesophagus is the tube or gullet connecting the mouth to the stomach. It lies in front of the vertebral column and behind the trachea (breathing tube) and heart. Stomach Food remains in the stomach for 3 to 4 hours. During this time it is further broken down by the muscular churning action of the stomach. Powerful gastric juices are also secreted by the cells of the stomach, contributing to chemical digestion. The food ends up in a semi-liquid form that is called chyme. Intestines Digested material is moved through the intestine via a process of wavelike muscular contractions called peristalsis. The process of digestion is completed in the small intestine. At this stage the nutrients that the body needs are absorbed through the walls of the small intestine. The waste material then moves into the large intestine where water is reabsorbed; thereby changing it into a more solid form, ready to be excreted through the rectum. Liver The liver is a large gland that is divided into four lobes. It carries out many vital metabolic functions such as: manufacturing bile which breaks down fats helping to maintain normal blood glucose levels producing the blood proteins, prothrombin and fibrinogen which have a role in blood clotting storing iron derived from food or the by-product of the breakdown of worn out red blood cells storing vitamins A, D, E & K, that have been extracted from food ingested heat production due to the high amount of metabolic activity; the liver is the main heat procuring organ of the body. Gallbladder 45 © NSW DET 2007 The gallbladder concentrates and stores bile that is produced in the liver. It then releases the bile when it is needed for digestion after a fatty meal. Pancreas The pancreas is what is called both an endocrine and exocrine gland. It produces pancreatic juices, containing enzymes, which play an important role in the chemical digestion of food. The pancreas also produces the hormones insulin and glucagon directly into the bloodstream, which is termed an endocrine function. Function of gastrointestinal system The function of the gastrointestinal system is to break down food mechanically and chemically so it can be absorbed into the bloodstream and then used by all tissues and cells. This process is called digestion and absorption. Every cell in the body requires energy in order to carry out its normal function; however the food we swallow is too large to enter the cells, so it needs to be broken down to provide this energy. Another function of the gastrointestinal system is to remove solid waste products from the body. This process is called elimination. The gastrointestinal system performs the following vital activities: Ingestion which involves the taking in of food Digestion which may take two forms: o mechanical breakdown of food by chewing and the action of muscles within the digestive tract. o chemical breakdown of food by enzymes produced at various stages of the digestive tract. Absorption is where substances pass through the walls of parts of the digestive tract into the bloodstream. 90% of the absorption of all nutrients takes place in the small intestine. The other 10% take place in the stomach and large intestines. Elimination is the process by which undigested foods leave the body. Digestion is controlled by the autonomic nervous system. Food moves along the gastrointestinal system by a wave like motion called peristalsis that breaks down the food mechanically. Food is also broken down chemically by the action of enzymes and bacteria. In the duodenum, food is acted upon by bile that is secreted by the gall bladder, juices from the pancreas and secretions from the wall of the duodenum. Fats are changed to fatty acids and glycerol, carbohydrates to simple sugars and proteins to amino acids. 46 © NSW DET 2007 Most of the absorption of nutrients takes place in the ileum through small projections called villi. Any undigested food and water moves into the colon. Movement is slow in this section and it is anywhere from 16-24 hours before waste is evacuated. This evacuation is a reflex action and is called defecation. It occurs as the rectal sphincter responds to a filling of the colon and can be voluntarily inhibited by keeping the external sphincter contracted. Urinary system Wastes are removed from the body through 4 body systems, respiratory, gastrointestinal (digestive), integumentary (skin) as well as the urinary system. We will explore how the urinary system removes wastes from the body. Structure of urinary system The urinary system comprises the kidneys, bladder, ureters and urethra. Male urinary system Diagram showing structure of male urinary system 47 © NSW DET 2007 Female urinary system Diagram showing structure of female urinary system Kidneys One of a pair of organs found in the abdominal cavity. Located against the back muscles on either side of the spine. Ureters Two tubes that run from the kidney to the bladder. Urine is conveyed through the ureters by peristalsis and gravity. Urinary bladder The bladder is a hollow sac situated towards the front of the lower part of the abdomen. The bladder stores urine. Urethra Urine is conveyed from the bladder through the urethra. In the female the urethra is about 10cms long; in the male the urethra is about 20cms long and also conveys semen. The opening at the end of the urethra is called the urinary meatus. The nephron The nephron is the basic working unit of the kidney. Blood enters the nephron under pressure and passes through the structures of the nephron to be filtered. Most of the water and many substances that are needed by the body are returned to the circulation. The kidneys produce 1-1.5 litres of urine on average per 24 hrs. Many factors effect the production of urine. These include age, illness, the amount of and type of fluids ingested, the amount of salt in the diet, caffeine, alcohol and medications. 48 © NSW DET 2007 Function of urinary system The functions of the urinary system are to: filter and remove waste products from the blood maintain water balance within the body play a part in red blood cell formation. assists in the regulation of blood pressure. Excretion of urine Urination (also called ‘voiding’ or ‘micturition’) is the process of emptying the bladder. As the bladder fills with urine, nerve impulses carry the message to the spinal chord that the bladder is filling. The spinal chord then sends a message back to the bladder via the motor nerves causing the bladder to contract and the sphincter to relax. This is a ‘reflex’ that gives rise to the urge to urinate. Reproductive system The reproductive system does not become active until puberty, when organs mature in response to hormonal activity. The structures of the male and female reproductive systems are different. These differences allow for the process of reproduction. Female reproductive system The main features of the internal organs of the female reproductive system are: Vagina The vagina extends from the vulva to where it opens to form the vaginal opening. Functions of female reproductive system The main functions of the female reproductive system are: provides a passageway for the foetus to be expelled from the uterus receives the penis during coitus allows discharge of menstrual flow. Uterus 49 © NSW DET 2007 The uterus is a hollow pear-shaped muscular organ and it consists of a fundus, body and cervix. The layers are the: perimetrium myometrium endometrium. The functions of uterus are to: receives fertilised ovum (embeds in endometrium) or sheds superficial layer if fertilisation does not take place at menstruation. contains the foetus during pregnancy expels the foetus at the end of pregnancy. Fallopian tubes The uterine tubes arise from the uterus and fan out to a trumpet-like shape called fimbriae The functions of the fallopian tubes are to transport the ovum from the ovary to the uterus by means of peristalsis with the aid of ciliated cells in the lining. Fertilisation takes place in the distal third of the uterine tube. Ovaries The ovaries are two almond shaped organs, each are located either side of the uterus. The functions of ovaries are to: produce ova produces hormone oestrogen and progesterone, which begins a puberty. Breasts The breasts are mammary glands which in females increase in size a puberty due to hormonal changes. When a woman gives birth to a baby the breasts produce milk to nourish the newborn. 50 © NSW DET 2007 Female reproductive system Diagram showing female reproductive system The menstrual cycle The cycle of changes in the uterus in preparation for pregnancy. Between puberty and menopause, the lining of the uterus goes through a 28-day cycle of growth and discharge. Menstruation occurs if fertilisation does not take place and the tissue lining the uterus that has been prepared for a fertilised ovum is unused. This lining passes out through the vagina as menstruation. Male reproductive system The main features of the external and internal organs of the male reproductive system are: Penis The penis conveys urine and seminal fluid to outside the body through the urethra. It is the organ of coitus (sexual intercourse). The foreskin is retractable sheath of skin covering the glans penis. Scrotum The scrotum is a skin pouch that encloses and protects the testes. It hangs external to the body to maintain temperature control for the testes, which is essential for sperm survival. Testes The testes are two egg-shaped organs containing sperm. They also produce and secrete male sex hormones (testosterone). Testosterone production begins at puberty. 51 © NSW DET 2007 Epididymis and vas deferens The Epididymis is a six-metre coiled tube that stores, transports and matures sperm. The vas deferens is a duct that transfers the sperm to the urethra. Ejaculatory ducts The ejaculatory ducts receive sperm and additives to produce seminal fluid. Prostate Gland The prostate gland is the size of a walnut and surrounds the urethra. It secretes an alkaline fluid that helps neutralise acidic seminal fluid and enhances motility of sperm. Urethra A tube that serves as a dual purpose of conveying urine from the body and semen. Male reproductive system Diagram showing male reproductive system Functions of male reproductive system The main functions of the male reproductive system are: testes (or testicles) which make the male sex hormone and contain spem cells the tube structure on the outside of the mane body is the penius through which spem cells pass from the urethra the prostate and seminal vesicles inside the lower abdomen produce fluid for the sperm cells – the fluid and perm cells are called semen. 52 © NSW DET 2007 Endocrine system The endocrine system is a system of ductless glands that secrete chemicals called hormones. Each hormone has a specific function, which may include counteracting the effects of another hormone. The endocrine system works side by side with the nervous system, assisting with growth, metabolism, immunity and reproduction. Hormones are secreted by endocrine glands directly into the bloodstream. Hormones regulate growth, blood sugar, metabolism, reproduction as well as various other functions such as sleep. The body contains many different types of hormones that are designed to regulate the body’s activities. Each hormone is specialised to target certain types of cells, like a lock and key. The hormone will only work if it comes into contact with the target cells. Hormone levels circulating in the body are adjusted through a feedback to the glands. Major glands of the endocrine system are the pituitary (master gland), thyroid, parathyroid, adrenal, pancreas, ovaries and testes, thymus and pineal glands Endocrine system 53 © NSW DET 2007 Diagram of endocrine system Hormones Hormones are chemical substances secreted by endocrine glands directly into the blood. Hormones are classified as proteins and steroids. Hormones are aimed at the ‘receptors’ of target organs. These receptors are located on the outer surface of the cells of those organs. Hormone secretion is controlled by three mechanisms: negative feedback, biorhythms and the central nervous system. Glands Glands are located throughout the body. The pituitary gland is the master gland and is located in the brain behind the eyes at the base of the frontal lobe. It is divided into two parts—the anterior and the posterior pituitary. Each part secretes specific hormones that affect the action of other glands in the body. The hypothalamus lies above the pituitary. It releases hormones that either stimulate or inhibit the release of hormones by the anterior pituitary. The pineal gland is located near the hypothalamus and houses our biologic clock. The thyroid gland lies in the neck near the ‘Adams Apple’. It produces a hormone that regulates growth and general metabolism. The thymus lies in the chest above the xiphoid process and gets smaller after puberty, but plays a part in the body’s immune system. The parathyroids lie within the thyroid capsule. They produce a hormone that regulates, along with one of the hormones of the thyroid gland, the level of phosphorus and calcium in the blood. Calcium is important for many functions of the body, such as muscle contraction and conduction of nerve impulses. The pancreas produces insulin and glucagon, which help regulate blood glucose levels. Insulin acts to lower blood sugar level and glucagon acts to raise blood sugar level. The adrenal glands lie on top of the kidneys and secrete hormones that help the body grow and adapt to stress. The ovaries in the female secrete oestrogen and progesterone. The rise and fall of these hormones determine the menstrual cycle and are important in causing the release of the ovum (egg) and in the maintenance of pregnancy. They are also responsible for the development of secondary sex characteristics. 54 © NSW DET 2007 The testes in the male produce testosterone, which causes the production of sperm. Testosterone is also responsible for the development of secondary sex characteristics. Summary of glands and their hormones GLAND FUNCTION Adrenal Regulates salt and water in the blood assists body in coping with stress. Pancreas Regulates blood glucose levels. Ovaries Affect the formation of the ova and the development of the female sex characteristics. Parathyroid Regulates the metabolism of calcium and phosphates. Pituitary Master gland. Testes Affect the formation of sperm and development of male sex characteristics Thymus Aids in the formation of lymphocytes. Thyroid Controls rate of the body’s metabolism and influences growth and development. Lymphatic and immune system The lymphatic system is a collection of organs (spleen, thymus, tonsils and intestine), capillaries, lymph vessels, ducts and nodes which drain excess fluid from the body, assists with fat absorption and helps the body defend itself against disease. Structure of the lymphatic system The lymphatic system is comprised of lymphatic capillaries lymphatic vessels lymphatic nodes lymphatic tissue lymphatic ducts. Lymph nodes are found in the axilla (under the arm), in the neck and in the groin. Lymphatic tissue is found in the spleen, the tonsils and the thymus. It is in the lymphatic tissue the lymphocytes are formed. 55 © NSW DET 2007 The lymphatic system Diagram of lymphatic system Function of the lymphatic system The lymphatic system is closely connected to the circulatory system. It consists of an additional set of vessels. These lymphatic vessels return 56 © NSW DET 2007 excess fluid (lymph) from the tissues to the blood. There are thousands of lymph nodes clustered along these lymphatic vessels. These lymph nodes help protect the body from disease by removing foreign material, such as bacteria, virus as well as cancer cells. The function of the lymphatic system is to: remove foreign substances and waste products from blood and lymph, eg dead cells, bacteria, viruses, and cancer cells fight disease and to maintains the balance of fluid in the tissues. Working together with the lymphatic system is the immune system. The immune system is a complex set of defences that guard the body against harmful micro-organisms. The body has three key defence mechanisms to protect against disease, and these are called first-line, second-line and thirdline defences. Structure of the immune system Immunity is best understood as lines of defence against invaders. 57 © NSW DET 2007 The body’s lines of defence Diagram of body’s lines of defence The first line of defence is the body’s barriers, which include mechanical barriers, chemical barriers and reflex actions Mechanical barriers, for example, intact skin and mucous membrane, protect the body against invading micro-organisms. Chemical barriers. For example, saliva, tears, sweat, mucus and stomach acid, help to destroy micro-organisms. Reflexes, for example, coughing, sneezing, blinking and vomiting help stop micro-organisms entering the body. 58 © NSW DET 2007 The second line of defence is the body’s response to the invading microorganism. These response include the actions of phagocytosis, inflammation, fever, protective proteins and natural killer cells. Inflammation is the way the body responds to injury. Blood vessels around the injury dilate, promoting blood flow to the area. This brings phagocytes Fever, a rise in the body’s temperature, helps to speed up repair of tissues Protective proteins aid in the inflammatory response by binding to the invading micro- organism to prevent the spread of infection. Natural killer cells (lymphocytes) directly attack invading microorganisms. Phagocytosis means that white blood cells such as phagocytes ingest invading micro-organisms and destroy them. The third line of defence is the action of lymphocytes: T cells, B cells and antibodies. They act directly on the invading micro-organism and provide immunity against those that enter the body and are recognised as being foreign. Types of immunity Immunity can be describes as the ability of the body to defend itself against disease. There are two main types of immunity: inborn (natural) and acquired (active). Immunity can be either natural or active. Natural immunity is an individual’s ability to ward off pathogens and is influenced by the person’s state of health, their nutritional status and their emotional response to stress. Active immunity occurs as the body builds up a resistance to pathogens that have been introduced through exposure or by immunisation. 59 © NSW DET 2007 Types of immunity Diagram showing types of immunity Function of the immune system The immune system is a complex system of cells and responses that recognises something as foreign and acts to remove it. For example microorganisms, foreign tissue, body cells that have become defective, eg cancer In conclusion The human body is a fascinating, intricate organism consisting of multiple systems working together to keep the body in balance (homeostasis). The purpose of this reading is to provide a brief overview of the human body – how it is structured (anatomy) and it functions (physiology). The aim is to set the scene for the changes associated with ageing and the common conditions associated with ageing – this will be covered in Reading 2: Apply basic knowledge of factors that support healthy functioning of the body. 60 © NSW DET 2007