Chapter 3
The Human Body
The Human Body
• First aiders must be familiar with the
basic structure and functions of the
human body.
• The most important and sensitive
organs include:
• Lungs
• Heart
• Brain
• Spinal cord
The Respiratory System (1 of 2)
• Death will result in about 4 to 6
minutes if the body’s oxygen supply
is cut.
• Oxygen from air is made available
to the blood through the respiratory
system.
The Respiratory System (2 of 2)
Respiration
The Passage of Air Into and Out of the Lungs
• Mechanics of breathing:
• Inhalation is breathing in.
• Exhalation is breathing out.
• Ventilation is a mechanical process that
alternately increases and decreases the
size of the chest cavity.
Respiratory Information
Infants and Children
• Respiratory structures are smaller.
• Easily obstructed airways
• Tongues take up more space in the
mouth.
• Trachea is more flexible.
• Primary cause of cardiac arrest is an
uncorrected respiratory problem.
Respiratory Rates
• Decreases at rest
• Increases during
exercise
• Controlled by the
brain
Signs of Inadequate Breathing
• A rate outside the normal range
• Cool or clammy skin that is pale or
cyanotic
• Nasal flaring
Respiration
When Hard Muscular Work Is Performed
• Lungs cannot get rid of carbon dioxide.
• Lungs cannot take in oxygen fast
enough at the normal rate.
• As carbon dioxide increases, respiration
increases.
• Heart rate increases.
The Circulatory System (1 of 2)
• Blood
• Heart
• Blood vessels
The Circulatory System (2 of 2)
• Blood carries nutrients and other
products from the digestive tract.
• Blood carries oxygen from the lungs.
• Blood transports wastes.
Heart (1 of 4)
• Pumps blood through the
vessels
• A powerful, hollow,
muscular organ
• About the size of a man’s
clenched fist
• Shaped like a pear
• Located in the left center
of the chest
Heart (2 of 4)
• Divided by a wall to create the right and
left compartments
• Compartments are divided into two
chambers:
• Atrium above
• Ventricle below
Heart (3 of 4)
During each contraction:
• The heart pumps blood high in carbon dioxide
and low in oxygen from the right ventricle to
the lungs.
• Oxygen-rich blood is returned to the left
atrium of the heart from the lungs.
Heart (4 of 4)
• Left ventricle pushes oxygen-rich
blood to the rest of the body.
• Right atrium receives oxygen-poor
blood.
Blood Vessels (1 of 4)
• Arteries
• Elastic, muscular tubes that carry blood
away from the heart
• Begin at the heart as two large tubes
• Pulmonary artery: Carries blood to the lungs
• Aorta: Carries blood to other parts of the
body and divides into capillaries
Blood Vessels (2 of 4)
• Capillaries
• A network of extremely fine vessels
• Oxygen and nourishment pass out of the
bloodstream into the body’s cells.
• Cells discharge waste into the
bloodstream.
• In the lungs, carbon dioxide is released
and oxygen is absorbed.
Blood Vessels (3 of 4)
• Veins
• Become larger and larger
• Form major trunks that empty blood
returning from the body into the right atrium
• Blood returning from the lungs goes into
the left atrium.
Blood Vessels (4 of 4)
Pulse
• Surge of blood that occurs each
time the heart contracts
• Can be felt at any point where an
artery lies near the skin surface
• Blood from a cut artery spurts.
• Blood from a cut vein flows.
Locations for Feeling Pulses
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Carotid artery
Femoral artery
Radial artery
Brachial artery
Posterior tibial
artery
• Dorsalis pedis
artery
Blood Pressure
• Blood pressure is a measure of the
pressure exerted by the blood on the
walls of the flexible arteries.
Blood
• Liquid portion
• Plasma
• 90% water
• Carries food
materials
• Carries waste
materials
• Solid portion
• Red blood cells
• Give blood its color
• Carry oxygen
• White blood cells
• Defense against
infection
• Platelets
• Essential for blood
clot formation
Hypoperfusion (Shock)
• Inadequate circulation of blood through an
organ
• Signs and symptoms include:
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Pale or cyanotic, cool, clammy skin
Rapid pulse
Rapid breathing
Restlessness, anxiety, or mental dullness
Nausea and vomiting
Reduction in total blood volume
Low or decreasing blood pressure
Subnormal body temperature
The Nervous System
The nervous system is a complex
collection of nerve cells (neurons) that
coordinate the work of all parts of the
human body and keep the individual in
touch with the outside world.
Neurons
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Receive stimuli
Transmit impulses
Produce nerve impulses
Cannot be regenerated
Central Nervous System
The Brain (1 of 5)
• Headquarters of the
human nervous system
• Most highly specialized
organ
• Requires considerable
oxygen
• Three main subdivisions
• Cerebrum
• Cerebellum
• Brain stem
Central Nervous System
The Brain (2 of 5)
• Cerebrum
• Divided into two hemispheres
• Controls functions such as sensation,
thought, and associative memory
• The occipital lobe is the sight center.
• The temporal lobes direct smell and
hearing.
Central Nervous System
The Brain (3 of 5)
• Cerebellum
• Located at the back of the cranium, skull,
below the cerebrum
• Coordinates muscular activity and balance
Central Nervous System
The Brain (4 of 5)
• Brain stem
• Extends from the base of the cerebrum to
the foramen magnum
• Controls breathing and heart rate
Central Nervous System
The Brain (5 of 5)
• Cerebrospinal fluid
• Similar to blood plasma
• Circulates throughout the brain and spinal
cord
• Serves as a protective cushion
• Exchanges food and waste materials
Central Nervous System
Spinal Cord (1 of 2)
• Soft column of nerve
tissue
• Exits the brain
through the foramen
magnum
• Thirty-one pairs of
spinal nerves branch
from the spinal cord
Central Nervous System
Spinal Cord (2 of 2)
• Some fibers carry impulses in, others
carry impulses away.
• Spinal nerves at different levels regulate
activities of various parts of the body.
• Vulnerable to injury
• Damage is usually irreversible.
• Injury can cause paralysis.
Peripheral Nervous System
• Made up of nerves that exit the spinal
cord through an opening in the bony
canal
• Consists of the sensory and motor
nerves
• If a nerve is seriously damaged, the
body part will not work.
Autonomic Nervous System
Controls:
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Heart rate
Digestion
Sweating
Other automatic body processes
The Skeletal System
• Adult skeleton has
206 bones.
• Bones are made of
living cells
surrounded by hard
deposits of calcium.
Skull (1 of 3)
• Rests at the top of the spinal column
• Houses the brain, certain glands, and
the centers of special senses
• Two parts
• Brain case (cranium)
• Face
Skull (2 of 3)
• Blood vessels and nerve trunks pass
to and from the brain through openings
in the skull.
• Can be fractured
• Does not “give”
• The face extends from the eyebrows to
the chin.
Skull (3 of 3)
Spinal Column (1 of 2)
• Consists of irregularly shaped bones
called vertebrae
• Lie on top of each other to form a strong,
flexible column
• Bound together by ligaments
• Can be damaged by disease or injury
Spinal Column (2 of 2)
• Careless handling
of an injured
person can
further injure the
cord and possibly
the person.
• A person with a
back or neck
injury must be
handled with
extreme care.
Thorax
• Also known as the rib cage
• Made up of ribs and the sternum
• Injuries to the thorax can puncture
the lungs and heart.
• Lowest portion of the sternum is the
xiphoid process.
Pelvis
• Formed by two hipbones and the
sacrum
• Muscles help connect pelvic bones,
trunk, thighs, and legs.
• Forms the floor of the abdominal cavity
• Holds the bladder, rectum, and internal
parts of the reproductive organs
Leg Bones (1 of 3)
• Upper leg (thigh)
• Femur
• Knee
• Knee joint
• Patella
Leg Bones (2 of 3)
• Lower leg
• Tibia
• Fibula
Leg Bones (3 of 3)
• Ankles, feet, and
toes
Shoulder
• Shoulder girdle
• Collarbone (clavicle)
• Shoulder blade (scapula)
• Fractures are common.
Arm Bones (1 of 2)
• Upper arm
• Humerus
• Easily dislocated
• Forearm
• Ulna
• Radius
Arm Bones (2 of 2)
• Wrist, hand, and
fingers
• Composed of eight bones
(carpals)
• Tendons from forearm to
fingers
• The palm has five long
bones (metacarpals).
• Fourteen bones of the
fingers (phalanges)
• The thumb is the most
important digit.
Joints
• Where two or more bones meet or join
• Some allow little movement, others allow a
wide range.
• Layer of cartilage acts as a buffer.
• Ligaments hold the bones and act as bands of
flexible connective tissue.
• Enclosed in a capsule
• A thick fluid lubricates and protects the joint.
The Muscular System (1 of 2)
• Voluntary muscles
• Under control of the
person
• Make all deliberate
acts possible
• Called skeletal muscles
• Can be injured in many
ways
The Muscular System (2 of 2)
• Smooth muscles
• Very little control by the person
• Line the walls of tubelike structures
• Cardiac muscle
• Found only in the heart
• Needs continuous oxygen and glucose
The Skin (1 of 2)
• Covers entire body
• Protects deep tissues from being
injured, drying out, or being invaded by
bacteria and other foreign bodies
• Regulates body temperature
The Skin (2 of 2)
• Epidermis (outer layer)
• Varies in thickness
• Dead cells are constantly
worn off.
• Dermis (inner layer)
• Rich supply of blood
vessels and nerve endings
• Contains sweat glands and
oil glands
• Above the subcutaneous
layer