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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.
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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.
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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.
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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).
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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
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