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 To properly care for your patients, you must have a thorough understanding of human
anatomy and physiology so you can assess the patient’s condition and communicate
with hospital personnel and other health care providers.
 You must be able to identify superficial landmarks of the body and know what lies
underneath the skin so that you can perform an accurate patient assessment.
 The skeleton gives the body its recognizable human form through a collection of
bones, ligaments, tendons, and cartilage.
 The skeletal system provides protection for fragile organs, allows for movement, and
gives the body its shape.
 The contraction and relaxation of the musculoskeletal system gives the body its
ability to move.
 Smooth muscle is found within blood vessels and intestines, and controls involuntary
functions. Skeletal muscle, so named because it attaches to the bones of the skeleton,
forms the major muscle mass of the body. It is also called voluntary muscle, because
all skeletal muscle is under direct voluntary control.
 Cardiac muscle is different from skeletal and smooth muscle because it has the
property of “automaticity;” it can generate and conduct electricity without influence
from the brain.
 The respiratory system consists of all the structures of the body that contribute to the
process of breathing. It includes the nose, mouth, throat, larynx, trachea, bronchi, and
bronchioles.
 The primary function of the respiratory system is to conduct respiration. Oxygen is
essential for the body to function. Gas exchange of oxygen into the blood and carbon
dioxide out of the blood occurs at the lungs’ alveoli via diffusion.
 Ventilation is the process of moving air in and out of the lungs.
 The respiratory center in the brainstem controls breathing. Nerves in this area sense
the level of carbon dioxide in the blood and spinal fluid. The brain adjusts breathing
as needed if the level of carbon dioxide or oxygen in the arterial blood is too high or
too low.
 Increases in the level of carbon dioxide in the blood (PaCO2) cause decreased pH
levels in the respiratory center, which triggers an increase in ventilation. Decreases in
the PaCO2 result in increased pH levels in the respiratory center and a decrease in
ventilation.
 Hypoxic drive is a backup system the body uses to control respiration. Areas in the
brain, walls of the aorta, and carotid arteries act as oxygen sensors and stimulate
breathing if the oxygen level falls.
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range. pH is the most common expression of acidity. pH ranges from 0 (most acidic)
to 14 (most basic), with 7.0 being neutral. When pH is higher than this, the blood is
too basic, or alkalotic. When pH is lower, the blood is too acidic, or acidotic.
The circulatory system is a complex arrangement of connected tubes, including the
arteries, arterioles, capillaries, venules, and veins. The cardiac cycle begins with
myocardial contraction and concludes at the beginning of the next contraction. The
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heart’s contraction results in pressure changes within the cardiac chambers, resulting
in the movement of blood from areas of high pressure to areas of low pressure.
Blood pressure is noted as a fraction, with the systolic reading placed above the
diastolic reading (for example, 140/ 70 mm Hg).
The pressure in the aorta against which the left ventricle must pump blood is called
the afterload. The greater the afterload, the harder it is for the ventricle to eject blood
into the aorta. This reduces the stroke volume—the amount of blood ejected per
contraction.
Cardiac output is the amount of blood pumped through the circulatory system in 1
minute. Cardiac output is expressed in liters per minute (L /min). The cardiac output
equals the heart rate multiplied by the stroke volume.
Increased venous return to the heart stretches the ventricles, resulting in increased
cardiac contractility. This relationship is known as Starling’s law.
Cell transport mechanisms relate to fluid administration, an AEMT skill. The cell
membrane allows some substances to pass through it, but not others. Selective
permeability allows normal differences in concentrations between intracellular and
extracellular environments to be maintained.
Several mechanisms, such as diffusion, osmosis, facilitated diffusion, active transport,
endocytosis, and exocytosis allow material to pass through the cell wall.
Fluid balance in the body must be maintained (homeostasis). Fluid balance is the
process of maintaining homeostasis through equal intake and output of fluids. The
major mechanisms for maintaining homeostasis include antidiuretic hormone (ADH),
thirst, kidneys, and water shifts.
The nervous system is perhaps the most complex organ system within the human
body. It consists of the brain, spinal cord, and nerves.
The skin is divided into two parts: the superficial epidermis, which is composed of
several layers of cells, and the deeper dermis, which contains the specialized skin
structures.
The skin, the largest single organ in the body, serves three major functions: to protect
the body in the environment, to regulate the temperature of the body, and to transmit
information from the environment to the brain.
The digestive system is composed of the gastrointestinal tract (stomach and
intestines), mouth, salivary glands, pharynx, esophagus, liver, gallbladder, pancreas,
rectum, and anus.
Digestion of food, from the time it is taken into the mouth until essential compounds
are extracted and delivered by the circulatory system to nourish all of the cells in the
body, is a complicated chemical process.
The endocrine system is a complex message and control system that integrates many
body functions.
The urinary system controls the discharge of certain waste materials filtered from the
blood by the kidneys.
The genital system controls the reproductive processes by which life is created.
Pathophysiology is the study of how the body reacts to diseases.