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)

RespirationThe 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 InformationInfants 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

RespirationWhen 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

• 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:

• 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

• 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:

• 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