Chapter 3The Human Body

The Human Body

• First aid providers must be familiar with the basic structure and functions of the human body.

• Using the proper medical terms allows you to communicate more effectively with the person and with medical care providers.

Directional Terms

• Right and left: the person’s right and left

• Anterior: front of body• Posterior: back of body• Superior: closer to

head• Inferior: closer to feet

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Directional Terms

• Lateral: farther from the middle• Medial: closer to the middle• Proximal: close to where the limb is

attached to the body• Distal: distant from the point of attachment• Superficial: closer to or on the skin• Deep: farther inside the body

Directional Terms

• Quadrant: section of the abdominal cavity divided by horizontal and vertical lines intersecting at the umbilicus; four equal areas. © Jones & Bartlett Learning.

The Body Systems

• Most life-threatening conditions affect the respiratory, circulatory, and nervous systems.

• Most important and sensitive organs:− Lungs− Heart− Brain− Spinal cord

The Respiratory System

• Death will result in about 4 to 6 minutes if the body’s oxygen supply is cut off.

• Oxygen from air is made available to the blood through the respiratory system.

The Respiratory System

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Mechanics of Breathing

• Respiration: The passage of air into and out of the lungs.− Inhalation is breathing in.− Exhalation is breathing out.

• Ventilation: A mechanical process that alternately increases and decreases the size of the chest cavity.

Mechanics of Breathing

• Infants and children− Smaller respiratory structures− Easily obstructed airways− Tongues take up more space in the mouth.− More flexible trachea− Primary cause of cardiac arrest is an

uncorrected respiratory problem.

Respiratory Rates

• Decreases at rest• Increases during

exercise• Controlled by the

brain

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Signs of Inadequate Breathing

• A rate outside the normal range• Cool or clammy skin that is pale or

cyanotic• Nasal flaring

The Circulatory System

• Blood• Heart• Blood vessels

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Heart

• Pumps blood through the vessels

• About the size of a man’s clenched fist

• Shaped like a pear• Located in the left

center of the chest

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Heart

• Divided by a wall to create the right and left compartments

• Compartments are divided into chambers:− Atrium above− Ventricle below

Heart

• During each contraction:− The heart pumps blood high in carbon dioxide

from the right ventricle to the lungs.− Oxygen-rich blood is returned to the left

atrium from the lungs.− Left ventricle pushes oxygen-rich blood to the

rest of the body.− Right atrium receives oxygen-poor blood.

Heart

• At each relaxation:− Blood flows into the left atrium from the lungs.− Blood flows into the right atrium from the rest

of the body.

Blood Vessels

• 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

• 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

• 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

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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

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Blood Pressure

• Blood pressure is a measure of the pressure exerted by the blood on the walls of the flexible arteries.

Blood

• Solid portion– Red blood cells

− Carry oxygen– White blood cells

− Defense against infection

– Platelets− Essential for blood

clot formation

• Liquid portion– Plasma

− 90% water− Carries food

materials− Carries waste

materials

Hypoperfusion (Shock)

• Inadequate blood circulation− Signs and symptoms include:

• Pale or cyanotic, cool, clammy skin • Rapid pulse and/or 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

• A complex collection of nerve cells that coordinate all parts of the human body

• Neurons− Receive stimuli− Transmit impulses− Produce nerve impulses− Cannot be regenerated

Nervous System Classifications

• Central nervous system (CNS)− Includes the brain and spinal cord

• Peripheral nervous system− Network of nerve cells− Divided into voluntary and autonomic

(involuntary) systems

Central Nervous System: The Brain

• Headquarters of the nervous system

• Three main subdivisions− Cerebrum− Cerebellum− Brainstem

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Central Nervous System: The Brain

• Cerebrospinal fluid− Similar to blood plasma− Circulates through the brain and spinal cord− Serves as a protective cushion− Exchanges food and waste materials

Central Nervous System: Spinal Cord

• Soft column of nerve tissue• Continuous with the lower part of the brain• Enclosed in the bony vertebral column• Thirty-one pairs of spinal nerves • Vulnerable to injury

Central Nervous System: Spinal Cord

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Peripheral Nervous System

• Made up of nerves that exit the spinal cord− Sensory nerves− Motor nerves

• If a nerve is seriously damaged, the body part will not work.

• Well protected against injury

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.

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Skull

• 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

• 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

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Spinal Column

• Consists of irregularly shaped bones called vertebrae− Form a strong, flexible

column− Bound together by

ligaments• Can be damaged by

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Thorax

• Also known as the rib cage• Made up of ribs and the sternum• Injuries to the thorax can puncture the

lungs and heart.

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

• Upper leg (thigh)− Femur

• Knee− Knee joint− Patella

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Leg Bones

• Lower leg− Tibia− Fibula

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Leg Bones

• Ankles• Feet• Toes

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Shoulder

• Shoulder girdle− Collarbone (clavicle)− Shoulder blade (scapula)

• Fractures are common.

Arm Bones

• Upper arm− Humerus

• Easily dislocated

• Forearm− Ulna− Radius

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Arm Bones

• Wrist, hand, fingers– Composed of eight

bones (carpals)– Five long bones of the

palm (metacarpals)– Fourteen bones of the

fingers (phalanges)– The thumb is the most

important digit.© Jones & Bartlett Learning.

Joints

• Where two or more bones meet or join• Allow movement• Layer of cartilage acts as a buffer• Ligaments hold the bones and act as

bands of flexible connective tissue.• A thick fluid protects the joint.

The Muscular System

• Voluntary muscles− Under control of

the person− Called skeletal

muscles− Can be injured in

many ways

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The Muscular System

• Smooth muscles− Very little control by the person− Line the walls of tube-like structures

• Cardiac muscle− Found only in the heart− Needs continuous oxygen and glucose

The Skin

• Covers entire body• Protects deep tissues from being injured,

drying out, or being invaded by bacteria • Helps regulate body temperature• Epidermis (outer layer)

− Dead cells are constantly worn off.

The Skin

• Dermis (inner layer)− Rich supply of blood vessels and nerve endings− Contains sweat and oil glands

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