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Lesson Outline Chapter 3 LESSON 3: The Human Body Lesson Objectives After completing this lesson, participants should be able to: Identify the systems of the body and their functions. Name the major bones of the body. Points The Human Body First aider must be familiar with the basic structure and functions of the human body. By using proper terms, you will be able to better communicate with medical care providers. The Respiratory System Death will result in about 4 to 6 minutes unless the oxygen intake is restored. Oxygen is made available to the blood through the respiratory system and then to the body cells by the circulatory system. Nose o Air normally enters the body during inhalation through the nostrils. o It is warmed, moistened, and filtered as it flows over the damp, mucous membrane of the nose. Pharynx and trachea o From the back of the nose or the mouth, the air enters the throat or pharynx. o The pharynx is a common passageway for food and air. o The trachea is also known as the windpipe and leads into the lungs. Lungs o Air sacs that occupy most of the chest cavity. Mechanics of Breathing Respiration o Passage of air into and out of the lungs Inhalation o The act of breathing in Exhalation o The act of breathing out Infants and Children Infants and children differ from adults. o Their respiratory structures are smaller and more easily obstructed. 1 of 5 Lesson Outline Chapter 3 o Their tongues take up more space in the mouth. o The trachea is more flexible. o The primary cause of cardiac arrest in children and infants is an uncorrected breathing problem. The Circulatory System Blood Heart Blood vessels Heart By contracting and relaxing, the heart pumps blood through the vessels. It is a powerful, hollow, muscular organ about as big as a man’s clenched fist, shaped like a pear, and located in the left center of the chest, behind the sternum (breastbone). Blood Vessels Arteries are elastic, muscular tubes that carry blood away from the heart. o Begin at the heart as two large tubes: the pulmonary artery, which carries blood to the lungs for the carbon dioxide-oxygen exchange and the aorta, which carried blood to all the other parts of the body. o The aorta divides and subdivides until it ends in networks of extremely fine vessels called capillaries. Each time that the heart contracts, the surge of blood can be felt as a pulse at any point where an artery lies close to the surface of the body. Major locations for feeling pulses include the following: o Carotid artery o Femoral artery o Radial artery o Brachial artery o Posterior tibial artery o Dorsalis pedis artery Blood pressure is a measure of the pressure exerted by the blood on the walls of the flexible arteries. Blood pressure might be high or low according to the resistance offered by the walls to the passage of blood. Blood Blood has liquid and solid portions. o The liquid portion is called plasma. o The solid portion includes disklike red blood cells; slightly larger, irregularly shaped white blood cells; and an immense number of smaller bodies called platelets. o Platelets are essential for the formation of blood clots. 2 of 5 Lesson Outline Chapter 3 The Nervous System A complex collection of nerve cells that coordinate the work of all parts of the human body. o It keeps the individual in touch with the outside world. Neurons receive stimuli from the environment and transmit impulses to nerve centers in the brain and spinal cord. Central Nervous System Brain o The headquarters of the human nervous system. o Divided into the cerebrum, cerebellum, and brain stem. Spinal cord o Soft column of nerve tissue continuous with the lower part of the brain. o Enclosed in the bony vertebral column. o It is vulnerable to injury. o Damage to the spinal cord is almost always irreversible. Peripheral Nervous System The peripheral nervous system consists of the sensory and motor nerves. It carries sensations such as smell, touch, heat, and sound from the body to the brain and the spinal cord. Autonomic Nervous System The autonomic nervous system consists of a group of nerves that controls heart rate, digestion, sweating, and other automatic body processes. These processes are not controlled by the conscious mind. The Skeletal System The human body is shaped by it bony frameworks. The adult skeleton has 206 bones. Bones are living cells surrounded by hard deposits of calcium. Skull The skull rests at the top of the spinal column. o It contains the brain, certain special-purpose glands, and the centers of special senses — sight, hearing, taste, and smell. o Although the skull is very tough, a blow can fracture it. o Even if there is no fracture, a sudden impact can tear or bruise the brain and cause it to swell, just as any soft tissue swells following an injury or a bruise. Spinal Column The spinal column is made up of irregularly shaped bones called vertebrae. Lying one on top of the other to form a strong, flexible column, the vertebrae are bound firmly together by strong ligaments. Between every two vertebrae is an intervertebral disk. 3 of 5 Lesson Outline Chapter 3 Thorax The thorax is also known as the rib cage. o It is made up of the ribs and the sternum. o The lowest portion of the sternum is the xiphoid process. Pelvis The two hipbones and the sacrum form the pelvis. Muscles help attach the pelvic bones, the trunk, the thighs, and the legs. The pelvis forms the floor of the abdominal cavity. Leg Bones Upper leg (thigh) o At the outer side of each hipbone is a deep socket into which the round head of the thighbone (femur) fits, forming a ball-and-socket joint. Knee o The knee joint is the largest joint in the body ands is a strong hinge joint. Lower leg o The lower leg refers to the portion of the lower extremity between the knee and the ankle. Tibia o Also known as the shin bone, it is located at the front and inner side of the leg. Ankles, feet, and toes o The ends of the tibia and fibula form the socket of the ankle joint. Shoulder The collar bone (clavicle) and the shoulder blade (scapula) form the shoulder girdle. Each clavicle is attached to the sternum at its inner end and to the scapula at its outer end. Fractures are common because the clavicle lies close to the surface and must absorb blows. Arm Bones Upper arm o The bone of the upper arm, the humerus, is the arm’s largest bone. o Its upper end is round; its lower end is flat. Forearm o The two bones of the forearm lie side by side. Wrist and Hand The palm of the hand has five long bones (metacarpals). 4 of 5 Lesson Outline Chapter 3 The 14 bones of the fingers (phalanges) give the hand its great flexibility. Joint A joint is where two or more bones meet or join. In a typical joint, a layer of cartilage acts as a buffer or a pad. Bones of the joint are held in place by ligaments. The Muscular System Skeletal muscles are attached by one or both ends to the skeleton by tendons. o Some muscles are attached to skin, cartilage, and special organs, or to other muscles. o Muscles help to shape the body and to form its walls. A person has little or no control over smooth muscles and usually is not conscious of them. Smooth muscles line the walls of tubelike structures. Cardiac muscle is a specialized form of muscle only found in the heart. The Skin Epidermis o The outer layer of the skin that varies in thickness in different parts of the body o Its dead cells are constantly worn off Dermis o The inner layer of skin that has a supply of blood vessels and nerve endings 5 of 5