A

Absorption: Uptake. In the biomedical sciences, absorption has diverse specific meanings.

Albuginea: Tough white fibrous tissue. The tunica albuginea of the testis, for example, is the layer of dense whitish inelastic tissue that surrounds the testis.

Artery: A vessel that carries blood high in oxygen content away from the heart to the farthest reaches of the body. Since blood in arteries is usually full of oxygen, the hemoglobin in the red blood cells is oxygenated. The resultant form of hemoglobin (oxyhemoglobin) is what makes arterial blood look bright red.

Atherosclerosis: Deposition of lipids and plaque formation in arteries, leading to hardening and decrease in size of arterial lumen 

Autonomic nerve: A nerve with involuntary neural function, such as vasodilation  

B

Blue vision: Distortion of color perception that results in increased blue tinting  

Body (of the penis): The main segment of the penis. It contains the erectile tissues that fill up with blood during sexual excitement. 

C

Corpora cavernosa: Two chambers in the penis which run the length of the organ and are filled with spongy tissue. Blood flows in and fills the open spaces in the spongy tissue to create an erection.

Corpus spongiosum: Midventral mass of erectile tissue that encloses the penile portion of the urethra.  

Cyclic guanosine monophosphate (cGMP): A substance whose formation is catalyzed by nitric oxide during sexual stimulation; cGMP causes smooth muscle relaxation that allows blood to flow into the erectile tissue (corpus cavernosum) of the penis. 

D

Dysfunction: Difficult function or abnormal function.

Dyspepsia: Dyspepsia refers to a condition (sometimes a disease) in which there are upper abdominal symptoms which may include upper abdominal pain, bloating (a feeling of abdominal fullness without objective abdominal distention), early satiety (a feeling of unusual fullness with very little intake of food), nausea or belching. The symptoms often are provoked by eating.

E

Erectile dysfunction: A common men's health problem characterized by the consistent inability to sustain an erection sufficient for sexual intercourse or the inability to achieve ejaculation, or both. Impotence can vary. It can involve a total inability to achieve an erection or ejaculation, an inconsistent ability to do so, or a tendency to sustain only very brief erections. Erectile dysfunction is also called impotence. 

Erectile bodies: Erectile tissue of the penis to become erect by filling with blood   

Erection: A penile condition characterized by enlargement and filling of erectile tissue with blood. 

F

FDA: The Food and Drug Administration, an agency within the U.S. Public Health Service, which is a part of the Department of Health and Human Services.

Flaccid: Referring to the non-erect, flabby state of the penis when a man is not sexually aroused 

G

Gene: The basic biological unit of heredity. A segment of deoxyribonucleic acid (DNA) needed to contribute to a function.

Glans penis: The distal end of the penis where the corpus spongiosum enlarges to form an acorn-shaped region 

H

Health: As officially defined by the World Health Organization, a state of complete physical, mental and social well-being, not merely the absence of disease or infirmity.

High blood pressure: Also known as hypertension, high blood pressure is, by definition, a repeatedly elevated blood pressure exceeding 140 over 90 mmHg – a systolic pressure above 140 with a diastolic pressure above 90.

Hormone: A chemical substance produced in the body that controls and regulates the activity of certain cells or organs.

Hypertension: High blood pressure, defined as a repeatedly elevated blood pressure exceeding 140 over 90 mmHg – a systolic pressure above 140 with a diastolic pressure above 90.

Hypotension: Any blood pressure that is below the normal expected for an individual in a given environment. Hypotension is the opposite of hypertension (abnormally high blood pressure).

I

Impotence: A common problem among men characterized by the consistent inability to sustain an erection sufficient for sexual intercourse or the inability to achieve ejaculation, or both. Impotence can vary. It can involve a total inability to achieve an erection or ejaculation, an inconsistent ability to do so, or a tendency to sustain only very brief erections. 

L

Libido: 1. Sexual drive. 2. In psychoanalysis, the psychic energy from all instinctive biological drives.

M

Medication: 1. A drug or medicine. 2. The administration of a drug or medicine. (Note that "medication" does not have the dangerous double meaning of "drug.")

Membrane: A very thin layer of tissue that covers a surface

Muscle: Muscle is the tissue of the body which primarily functions as a source of power. There are three types of muscle in the body. Muscle which is responsible for moving extremities and external areas of the body is called "skeletal muscle." Heart muscle is called "cardiac muscle." Muscle that is in the walls of arteries and bowel is called "smooth muscle."

N

Nerve: A bundle of fibers that uses chemical and electrical signals to transmit sensory and motor information from one body part to another.  Neurogenic: Originating in the nervous system   

Neurological: Having to do with the nerves or the nervous system

Neurotransmitter: A chemical messenger used by nerve cells to transmit nerve impulses from one nerve cell to another  

NIH: The National Institutes of Health. The NIH is an important U.S. health agency. It is devoted to medical research. Administratively under the Department of Health and Human Services (HHS), the NIH consists of 20-some separate Institutes and Centers. NIH's program activities are represented by these Institutes and Centers.

Nitric oxide: A compound that is toxic but which, paradoxically, plays a number of important roles in the body, including the following:

• It acts as a vasodilator (blood vessel relaxant).
• It therefore controls blood flow to tissues.
• It regulates the binding and release of oxygen to hemoglobin.
• It thereby controls the supply of oxygen to mitochondria (cell powerhouses that generate energy).
• It kills parasitic organisms, virus-infected cells, and tumor cells (by inactivating respiratory chain enzymes in their mitochondria).
• It stimulates the production of new mitochondria.

O

Orgasm: The climax of coitus, consisting of a series of involuntary muscle contractions in the anus, lower pelvic muscles, and sexual organs, accompanied by a sudden release of endorphins providing a feeling of euphoria 

P

Penile: Of or pertaining to the penis

Penis: The external male sex organ used to copulate and ejaculate semen and to convey urine outside the body. In Latin, the word "penis" originally meant "a tail ." The Latin "penis" is related to the verb pendere meaning "to hang down."

Peyronie's disease: A condition of unknown etiology in which there is a structural deformity of the erectile tissue of the penis 

Phosphodiesterase 5 (PDE5): Enzyme that breaks down cGMP during an erection, ultimately returning the penis to a flaccid state 

Priapism: Persistent, abnormal and painful erection of the penis. If this condition occurs for more than four hours, men are urged to seek immediate medical help due to the fact permanent damage to the penis may occur if left untreated. 

Prostate gland: An accessory reproductive gland, located under the urinary bladder and responsible for the secretion of a milky fluid that is important for the production and viability of sperm.  

Prostaglandin: One of a number of hormone-like substances that participate in a wide range of body functions such as the contraction and relaxation of smooth muscle, the dilation and constriction of blood vessels, control of blood pressure, and modulation of inflammation. Prostaglandins are derived from a chemical called arachidonic acid.

Psychogenic: Caused by the mind or emotions

S

Scrotum: A pouch of skin which contains the testes, epididymides, and lower portions of the spermatic cords

Sensation: In medicine and physiology, sensation refers to the registration of an incoming (afferent) nerve impulse in that part of the brain called the sensorium, which is capable of such perception. Therefore, the awareness of a stimulus as a result of its perception by sensory receptors. (Sensory is here synonymous with sensation.)

Sensory: Relating to sensation, to the perception of a stimulus and the voyage made by incoming (afferent) nerve impulses from the sense organs to the nerve centers

Side effects: Problems/symptoms that occur when treatment goes beyond the desired effect. Or problems/symptoms that occur in addition to the desired therapeutic effect.

Sildenafil (citrate): A drug, C22H30N6O4S, used to treat sexual dysfunction by increasing the level of cyclic GMP (cGMP or guanosine monophosphate), which increases blood flow to erectile tissues.

Smooth muscle: One of the three types of muscle tissue in the body (skeletal, smooth, cardiac). Generally forms the supporting tissue of blood vessels and hollow internal organs such as the stomach, intestine, and bladder. So named because of the absence of microscopic lines called "cross-striations" which are seen in the other two types.

T

Testes: The male sex glands. They are located behind the penis in a pouch of skin called the scrotum. The testes produce and store sperm, and are also the body's main source of male hormones, such as testosterone. These hormones control the development of the reproductive organs and other male characteristics, such as body and facial hair, low voice, and wide shoulders.

Testosterone: A "male hormone" -- a sex hormone produced by the testes that encourages the development of male sexual characteristics, stimulates the activity of the male secondary sex characteristics, and prevents changes in them following castration. Chemically, testosterone is 17-beta-hydroxy-4-androstene-3-one.

Tissue: A tissue in medicine is a broad term that is applied to any group of cells that perform specific functions. A tissue in medicine need not form a layer. Thus,

• Bone marrow is a tissue;
• Connective tissue consists of cells that make up fibers in the framework supporting other body tissues; and
• Lymphoid tissue is the part of the body's immune system that helps protect it from bacteria and other foreign entities. 

Tunica albuginea: The whitish membrane within the penis that surrounds the spongy chambers (corpora cavernosa) in the penis and which helps to trap the blood in the corpora cavernosa, thereby sustaining erection of the penis. The term comes straight from the Latin tunica (covering or coat) + albuginea (white) = a covering that is white, like the white (albumen) of an egg.

U

Urethra: The transport tube leading from the bladder to discharge urine outside the body. In males, the urethra travels through the penis, and carries semen as well as urine. In females, the urethra is shorter than in the male and emerges above the vaginal opening.

V

Vasodilator: An agent that causes dilation of blood vessels  

Vein: A blood vessel that carries blood toward the heart  

Venous plexus: A vascular network formed by numerous connections between veins