Alimentary canal The tubular passage that extends from the mouth to the anus. It is also known as the digestive tract.
Alveoli Plural of alveolus.
Alveolus The tiny sacs at the ends of the bronchial tree of the lungs.
Antibodies Antibodies are produced in response to certain foreign particles and micro-organisms that enter your body.
Anus The opening at the lower end of the alimentary canal through which feces is eliminated from the body.
Aorta The body's largest blood vessel, the aorta, arches out of the heart and down toward the lower body. It has a diameter of about one inch and blood rushes through it at a speed of about eight inches per second.
Arteries Blood vessels which carry oxygenated blood from the heart throughout the body to nourish tissue cells. 
Arteriole A small blood vessel that branches off an artery to link it to a capillary.
Axon A nerve fiber that conducts nerve impulses away from the body of the nerve cell.
Bile A bitter, alkaline, brownish-yellow or greenish-yellow fluid that is secreted by the liver, stored in the gallbladder, and discharged into the small intestine and aids in the digestion of fats.
Bronchi The bronchi are the tubes which carry air from the trachea to the inner recesses of the lungs, where it can transfer oxygen to the blood in small air sacs called alveoli.
Bronchus Singular of Bronchi.
Capillaries These blood vessels form a complex network throughout the body for the interchange of various substances, such as oxygen and carbon dioxide, between blood and tissue cells.
Cerebellum Area of the brain responsible for the regulation and coordination of complex voluntary muscular movement as well as the maintenance of posture and balance.
Cerebrum The large, rounded structure of the brain occupying most of the cranial cavity. It controls and integrates motor, sensory, and higher mental functions, such as thought, reason, emotion, and memory.
Cilia Tiny hairs, as in the eyelashes, fallopian tubes, or in the nasal mucous layer. They work either to filter particulates or push material along a mucous lining in wave-like movements.
CNS Medical abbreviation for Central Nervous System which is the portion of the vertebrate nervous system consisting of the brain and spinal cord.
Constipation Difficulty in excreting feces waste due to compaction or hard, dry characteristics of feces. It can result from physiological disorders or poor diet.
Cranium The part of the skull that encloss the brain.
Dendrite Extension of a nerve cell that conducts impulses from adjacent cells inward toward the cell body. A single nerve may possess many dendrites.
Diarrhea The frequent passage of loose, watery stools, and usually is the symptom of some types of flu, food poisoning, and can even occur after eating spicy foods. Untreated, diarrhea can lead to dehydration.
Duodenum The beginning portion of the small intestine, starting at the lower end of the stomach.
Epiglottis The thin elastic cartilaginous over structure located at the root of the tongue that folds the glottis to prevent food and liquid from entering the trachea during the act of swallowing.
Esophagus The muscular, membranous tube for the passage of food from the pharynx to the stomach.
Feces The unused food mater“al excreted from the body via the anus as solid waste.
Gray matter The white, myelinated fibers of the nerve bundles within the brain and spine account for the white matter found there.
Hemoglobin The oxygen-transporting molecular constituent of blood.
Inferior vena cava It is larger than the superior vena cava. It returns blood from the lower half of the body to the right atrium of the heart.
Left atrium It is a small upper cavity of the heart. Oxygenated blood returns from the lungs through the pulmonary veins into the left atrium.
Left ventricle It is the large lower cavity of the heart. Its walls are three times thicker than those of the right ventricle, making it the most powerful chamber in the heart.
Medulla oblongata The lowermost portion of the brain, continuous with the spinal cord, responsible for the control of respiration, circulation, and certain other bodily functions.
Nasal cavity It is situated between the lachrymal sac (tear duct) and the inferior meatus of the nose. Cilia line the mucous membrane of the nasal cavity.
Nerve One or more bundles of signalcarrying fibers that connect the brain and the spinal cord with other parts of the body.
Pieristalsis The involuntary muscular contractions that occur in various tubular vessels of the body.
Pharynx It is the upper portion of the airway and the digestive tract. It connects with openings into four general areas the mouth cavity (at the back of the tongue), the nasal cavity, the larynx (which Ieads to the trachea), and the esophagus.
Plasma The watery, colorless fluid in lymph and blood in which the white and red blood cells and platelets are suspended.
Platelets Small disk-shaped bodies in blood that play an essential role in clot formation.
PNS PNS stands for peripheral nervous system which consists of the cranial nerves and spinal nerves leaving the CNS. They run out to every part of the body.
Pulmonary artery Carries blood from the right ventricle of the heart to the lungs.
Pulmonary vein Carries oxygenated blood from the lungs to the left artium of the heart.
Rectum One of the last portions of the large intestine. About five inches long, fecal wastes are stored in the rectum until they are expelled by passing them through the anal canal and out of the anus.
Septum The thin wall dividing two cavities, the left side and the right side of the heart.
Sinus A hole or cavity in a bone or organ. The facial bones, for example, feature a  number of sinus cavities within them.
Spinal cord The thick, whitish cord of nerve tissue that extends from the medulla oblongata down through the spinal column and from which the spinal nerves branch ofto various parts of the body. 
Spleen A large organ located to the left of the stomach below the diaphragm, serving to store blood, disintegrate old blood cells, filter foreign substances from the blood, and produce lymphocytes. 
Superior vena cava The second largest vein in the body. It returns the blood from the head, arms and upper body to the right atrium of the heart. 
Urine The colorless to yellowish liquid, slightly acidic waste material secreted by the kidneys.
Ureter The long, narrow duct that transports urine the kidneys to the urinary bladder.
Urethra The canal through which urine is discharged from the bladder. 
Vein Blood vessels which carry deoxygenated blood from the tissue cells to the heart. 
Villi Villi are fingerlike folds covering the surface of the small intestines. 
White blood cells The colorless or white cells in the blood that have a nucleus and cytoplasm and help protect the body from infection and disease.