Download Summary of Human systems Human Body Systems Overview

Summary of Human Systems
Background Information
Levels of Organization/Structure (p. 587): cell, tissue, organ, organ system, organism
Tissue Types (p. 590): epithelial, nervous, connective, muscle
Homeostasis (p. 593): our systems maintain a ‘steady state’ so that they can all work at their highest level of functioning
to promote the health and survival of the organism
Feedback loops (p. 698): how our systems maintain homeostasis
The Integumentary System (Ch. 27.3)
Function The major functions of the integumentary system include: protection, vitamin D production, and temperature
regulation. It is also a sensory organ.
Structure
The integumentary system consists of hair, skin, and nails. The skin consists of the epidermis, the dermis, and the
subcutaneous layers. In addition, there is a top layer of dead skin cells for added protection. Sebaceous glands, sweat
glands, melanocytes (that produce melanin) are all located in the dermal layer, along with nerves and hair follicles. The
subcutaneous layer consists mostly of nerves and adipose (fat) cells.
The Muscular System (Ch. 27.5)
Function The major job of the muscular system is movement and it is also involved in temperature regulation
Structure
Muscle cells are called muscle fibers due to their elongated shape. They contain special fibrils call actin and myosin,
which are responsible for muscle contraction. The sliding filament theory describes how a muscle contracts—actin slides
past myosin when ATP and Ca bind to them. Muscle contraction is triggered by the nervous system.
The major classes of muscles include: smooth, skeletal, and cardiac. Smooth and cardiac muscles are involuntary,
meaning you do not control their contraction. Skeletal and cardiac muscle have stripes known as striations. Cardiac
muscle refers to the heart, an example of a smooth muscle can be found in the digestive tract and the female reproductive
tract, and skeletal muscles include the triceps and biceps.
Major muscles in the muscular system include: bicep, tricep, pectoralis major, deltoid, quadriceps, rectus
abdominus, external obliques
The Skeletal System (Ch. 27. 4)
Function The skeletal systems main jobs include structure/support, movement, the production of blood cells, and
protection.
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Structure
Bone is made up of minerals and collagen fibers and comes in two forms: compact bone and spongy bone. Marrow in the
middle of the bone is the site of blood cell production. A thin layer called the periosteum covers the bone and the bone
contains Haversian canals in the middle of each Haversian system (circular component of bone) that contain blood vessels
and nerves. Our skeletal first starts out as cartilage, which is then replaced by bone producing cells (osteoblasts) that
produce osteocytes, mature bone cells. Osteoclasts are cells that break down bone, and their activity increases with age.
If the osteoclasts and osteoblasts are not in synch, you can wind up with too much bone being broken down without being
replaced, leading to “brittle bones,” also known as osteoporosis.
The skeleton can be broken down into two main parts, the axial skeleton and appendicular skeleton. Joints are places
where two bones meet and can come in various forms: fixed, gliding, pivot, ball and socket, and hinge.
Major bones of the skeleton include: cranium, spine, ribs, pelvis, humerus, radius, ulna, clavicle, femur, tibia, fibia,
carpals, and tarsals.
The Nervous System (Ch. 28)
Function This system directs and coordinates the activity of all the other systems in response to changing environmental
conditions/needs
Structure
The brain is divided into many different regions, called lobes, with each one responsible for various activities/functions.
The brain stem, cerebrum, cerebellum are the three major divisions of the brain. Electrochemical impulses and chemicals
known as neurotransmitters are responsible for signal transmission throughout the nervous system.
Brain cells are called neurons and consist of a cell body, axon, and many branching dendrites. The axon is covered with a
myelin sheath that allows the chemical pulses to travel quickly from one neuron to the next.
Major organs of this system include the brain, spinal cord, nerves
Feedback loops are a large part of the nervous system. Sensory receptors send messages to the central and/or peripheral
nervous system which then send a signal back through a motor neuron which causes a muscle movement (think of a
reflex). You have many sensory receptors all over your body that relay messages to the brain based on temperature,
pain, touch/stretch, light or the presence of chemicals.
The Endocrine System (Ch. 32.4)
Function This system uses chemical messengers to coordinate activities of the various systems
Structure
The endocrine system consists of different glands that produce and secrete chemicals that influence the output of target
cells. A hormone can have very different effects on different cells of the body and these influences can be enormous
(puberty!). Many hormones are steroids, meaning they are a type of lipid, which allows them to go directly through the
cell membrane (also a lipid) and go straight into the nucleus of a cell to direct protein synthesis.
The major organs of the endocrine system include the hypothalamus, the anterior and posterior pituitary gland,
thyroid, the parathyroids, adrenal glands, the pancreas, and the gonads (male: testes or female: ovaries).
The Circulatory System (Ch. 30.1)
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Function This system transports nutrients, gases, and wastes in/out/around the body. It is also involved in temperature
regulation.
Structure
The circulatory system consists of blood vessels called arteries, veins, and capillaries that transport materials to/from the
body cells. Blood itself is a mixture of erythrocytes (RBCs), leukocytes (WBCs), platelets, proteins, nutrients, gases,
wastes, and water. The heart pumps the blood throughout the body and to the lungs, where waste gases can be expelled
and oxygen inhaled. The structure of the heart includes two ventricles, two atria, a septum, and a connection to
pulmonary arteries/veins and the aorta and vena cava. The heart itself is controlled by pacemaker cells, but can be
affected by input from the nervous/endocrine systems.
Arteries have layers of muscle around them while veins do not. Veins contain valves to help push blood back up to the
heart. Capillaries are only one cell thick to allow body cells to exchange materials easily.
The major organs of the circulatory system include: the heart, arteries, veins, and capillaries
The Immune (Lymphatic) System (Ch. 31)
Function The major function of this system is to recognize and destroy foreign invaders and abnormal self cells.
Structure
Immune cells are made in the bone marrow and mature either in the bone marrow (B cells) or in the thymus gland (T
cells). These cells are very specialized, with each type capable of recognizing one specific antigen (cell identification
markers) and destroying that foreign cell. Other immune cells (macrophages) use phagocytosis to swallow any foreign
cell antigen they encounter (they are nonspecific). B cells release antibodies to fight foreign invaders while T cells can
attack the foreign invaders directly. T cells also look for self cells that display foreign or abnormal antigens, which would
indicate a viral infection or cancer.
The major organs of this system include the lymph nodes, lymphatic vessels, bone marrow, spleen and thymus.
The immune system reaction to invaders includes both nonspecific and specific defenses. Non specific defenses include
inflammation, fever, sweat, and tears. Specific defenses include the B and T cell actions listed above.
Vaccines are given to provide passive immunity to someone (it is called active immunity when you make your own
antibodies to fight disease). A vaccine is simply a cocktail of heat killed pathogens (a bacteria, etc.) that cannot cause
disease because it is dead but can be recognized as foreign by the body. The B cells will then make antibodies against that
pathogen which will circulate in the bloodstream for up to 10 or even 20 years (when you then get a ‘booster shot’).
Vaccines help prevent disease by having the antibodies ready to respond quickly to a pathogen. Without them, a person
could get very sick during the 10-12 days it would normally take for enough antibodies to be produced to actually kill the
pathogen (see p. 375)
Bacteria, fungus, and protists cause disease by invading tissues (living between/among cells) and releasing toxins.
Viruses actually enter cells, hide there away from immune system detection, and use the cell as a factory to make their
own viral proteins until they finally explode the cell with each newly made virus moving on to invade another cell (see p.
373).
HIV is the virus that causes AIDs. HIV can lay dormant inside a person’s cells for years until becoming active and
causing the disease symptoms we call AIDs. HIV is transferred through blood contact, the main ways are due to blood
contact from childbirth or other exposures, unsafe sexual practices and unsafe needle/injection practices (see p. 374).
The Respiratory System (Ch. 30.5)
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Function This system is responsible for gas exchange.
Structure
The respiratory system consists of two lungs (five lobes) that contain small sacs called alveoli, where oxygen and carbon
dioxide are exchanged. To take a breath, the body signals the diaphragm to contract, expanding the thoracic cavity and
pulling air into the lungs. To exhale, the diaphragm relaxes, pushing back up in the cavity and forcing air out of the lungs.
The major organs of the respiratory system include the lungs, trachea, bronchi, bronchioles, and diaphragm.
The Digestive System (Ch. 29.2)
Function The digestive system is involved in the physical and chemical breakdown of food and the absorption of nutrients
and fluids.
Structure
Many enzymes are involved in the breakdown of food, with each type breaking down a different type of food—protein,
lipid, or carbohydrate. Each of the organs involved either produces/secretes one of these enzyme (liver, pancreas) or is
involved in the physical breakdown of the food (stomach, mouth). Other areas (small and large intestines) are responsible
for the reabsorption of nutrients and fluids before the remaining waste is exported to the excretory system for removal.
The major organs of the digestive system include the mouth, epiglottis, esophagus, liver, stomach, pancreas, and the
small and large intestines.
The Excretory System (Ch. 32.2)
Function The function of this system is to collect, concentrate, and excrete metabolic wastes, and regulate
water/electrolyte concentrations
Structure
This system is critical for the health of the body—nephrons are responsible for the concentration of wastes and
reabsorption of water and minerals that occurs in the kidneys. Liquid wastes are then delivered to the urinary bladder to
be expelled while the water and minerals are returned to the blood flow.
The major organs of this system consist of the renal arteries and veins, the kidneys, ureter, urinary bladder, and
urethra.
The Female Reproductive System (Ch. 33)
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Function The function of this system is the production, maturation, and secretion of the female sex cell and the support of
the fetus until gestation
Structure
Egg cells mature in the ovaries and are released every month due to the influence of hormones produced by various
endocrine glands. These gonad released hormones are also responsible for primary and secondary sex characteristics
found in females.
The egg is released from a structure known as a follicle that fuses with the membrane of the ovary. Once released, the egg
is swept into the oviduct (Fallopian tube) and travels down the tube to the uterus. The sperm will unite with the egg in the
tube and the fertilized egg will then implant into the lining of the uterus known as the endometrium. At birth, the head of
the fetus will push against the cervix (the lower portion of the uterus) and once the cervix is dilated sufficiently, the baby
will travel headfirst down and out of the vagina.
The major internal organs of the female reproductive tract include the ovaries, fallopian tubes, uterus, cervix, vagina.
The Male Reproductive System (Ch. 33)
Function The primary function on this system is the genesis, maturation, and delivery of the male reproductive cell to the
female reproductive tract.
Structure
Sperm cells are created through meiosis in the testes, which are enclosed in a protective sac known as the scrotum. This
sac is outside of the main body cavity because sperm require a temperature lower than our normal body temp. After
genesis in the seminiferous tubules of the testes, the sperm mature in the epididymus (where flagella grow in length and
the sperm gain the ability to swim), and then are transported through the vas deferens past various accessory organs that
secret fluids that make up semen. The ingredients in semen include fructose (a sugar for energy), pH balancers (so the
sperm can survive in the highly acidic vagina), and a special chemical to help the sperm penetrate the egg (if it gets that
far!). The penis delivers the sperm into the female reproductive tract where they furiously swim up the vagina, through
the cervix and uterus, to the fallopian tubes where an egg might be located, depending on the timing.
The major internal organs of the male reproductive tract include testes, epididymis, prostate state, bulbourethral
gland, seminal vesicles.
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