Tumescence is the quality or state of being tumescent or swollen. Tumescence usually refers to the normal engorgement with blood

Blood

Blood is a specialized bodily fluid in animals that delivers necessary substances such as nutrients and oxygen to the cells and transports metabolic waste products away from those same cells....

 (vascular congestion

Vascular congestion

Vascular congestion is the engorgement of an entity, such as the blood vessels of the erectile tissues, with blood. It is known to occur with deep venous thrombosis ....

) of the erectile tissue

Erectile tissue

Erectile tissue is tissue in the body that can become erect, usually by becoming engorged with blood.-Erectile tissue in the clitoris and penis:...

s, marking sexual excitation and possible readiness for sexual activity. The tumescent sexual organ in men is the penis

Penis

The penis is a biological feature of male animals including both vertebrates and invertebrates...

 and in women is the clitoris

Clitoris

The clitoris is a sexual organ that is present only in female mammals. In humans, the visible button-like portion is located near the anterior junction of the labia minora, above the opening of the urethra and vagina. Unlike the penis, which is homologous to the clitoris, the clitoris does not...

.

Regularly, men who experience erectile dysfunction

Erectile dysfunction

Erectile dysfunction is sexual dysfunction characterized by the inability to develop or maintain an erection of the penis during sexual performance....

 are given a nocturnal penile tumescence

Nocturnal penile tumescence

Nocturnal penile tumescence is the spontaneous occurrence of an erection of the penis during sleep. All men without physiological erectile dysfunction experience this phenomenon, usually three to five times during the night...

 (NPT) test, usually over a three day period. Such a test detects the presence of an erection

Erection

Penile erection is a physiological phenomenon where the penis becomes enlarged and firm. Penile erection is the result of a complex interaction of psychological, neural, vascular and endocrine factors, and is usually, though not exclusively, associated with sexual arousal...

 occurring during sleep

Sleep

Sleep is a naturally recurring state characterized by reduced or absent consciousness, relatively suspended sensory activity, and inactivity of nearly all voluntary muscles. It is distinguished from quiet wakefulness by a decreased ability to react to stimuli, and is more easily reversible than...

 using either (1) a small, portable computer

Computer

A computer is a programmable machine designed to sequentially and automatically carry out a sequence of arithmetic or logical operations. The particular sequence of operations can be changed readily, allowing the computer to solve more than one kind of problem...

 connected to two bands placed around the shaft of the penis

Penis

The penis is a biological feature of male animals including both vertebrates and invertebrates...

 which records penile tumescence, or (2) a band of paper tape with perforations (like postage stamp

Postage stamp

A postage stamp is a small piece of paper that is purchased and displayed on an item of mail as evidence of payment of postage. Typically, stamps are made from special paper, with a national designation and denomination on the face, and a gum adhesive on the reverse side...

s) that is fit snugly around the shaft of the penis and will break at the perforations during penile tumescence.

The goal of nocturnal penile tumescence testing is to determine whether a man can experience an erection

Erection

Penile erection is a physiological phenomenon where the penis becomes enlarged and firm. Penile erection is the result of a complex interaction of psychological, neural, vascular and endocrine factors, and is usually, though not exclusively, associated with sexual arousal...

 while sleeping after reporting he is unable to experience an erection while awake. If a man does obtain an erection while sleeping

Sleep

Sleep is a naturally recurring state characterized by reduced or absent consciousness, relatively suspended sensory activity, and inactivity of nearly all voluntary muscles. It is distinguished from quiet wakefulness by a decreased ability to react to stimuli, and is more easily reversible than...

, but cannot obtain one while awake, a psychological

Psychology

Psychology is the study of the mind and behavior. Its immediate goal is to understand individuals and groups by both establishing general principles and researching specific cases. For many, the ultimate goal of psychology is to benefit society...

 cause or a medication side effect is usually suspected. Otherwise, if a man does not obtain an erection in either state, a physiological

Physiology

Physiology is the science of the function of living systems. This includes how organisms, organ systems, organs, cells, and bio-molecules carry out the chemical or physical functions that exist in a living system. The highest honor awarded in physiology is the Nobel Prize in Physiology or...

 cause is usually suspected.

Detumescence

Detumescence is the reversal of this process, by which blood leaves the erectile tissue, returning to the flaccid state.

External links

• The Female Response – Humboldt Universität zu Berlin
  Berlin
  Berlin is the capital city of Germany and is one of the 16 states of Germany. With a population of 3.45 million people, Berlin is Germany's largest city. It is the second most populous city proper and the seventh most populous urban area in the European Union...
  
  
• The Male Response – Humboldt Universität zu Berlin
  Berlin
  Berlin is the capital city of Germany and is one of the 16 states of Germany. With a population of 3.45 million people, Berlin is Germany's largest city. It is the second most populous city proper and the seventh most populous urban area in the European Union...