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 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 Solid portion Plasma Red blood cells 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 Fractures are common. Collarbone (clavicle) Shoulder blade (scapula) Fractures are common.

Arm Bones (1 of 2) Upper arm Forearm Humerus Ulna Radius 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) Dermis (inner 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