Prostate

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Prostate
Image:Prostatelead.jpg
Male Anatomy
Image:Gray1160.png
Prostate with seminal vesicles and seminal ducts, viewed from in front and above.
Latin	prostata
Gray's	subject #263 1251
Artery	internal pudendal artery, inferior vesical artery, and middle rectal artery
Vein	internal iliac vein
Nerve	inferior hypogastric plexus
Lymph	external iliac lymph nodes, internal iliac lymph nodes
Precursor	Wolffian duct
MeSH	Prostate
Dorlands/Elsevier	p_36/12671161

The prostate is an exocrine gland of the male mammalian reproductive system.

The prostate differs considerably between species anatomically, chemically, and physiologically.

1 Relations
2 Function
3 Secretions
4 Regulation
5 Development
6 Structure
- 6.1 Zones
- 6.2 Lobes
7 Disorders of the prostate
8 Additional images
9 See also
10 External links

[edit] Relations

Posterior: rectum
Superior: urinary bladder
Inferior: pubic symphysis

[edit] Function

The main function of the prostate is to store and secrete a clear, slightly basic fluid that constitutes up to one-third of the volume of semen. Semen is composed of sperm and seminal fluid; about 10-30% of the seminal fluid is produced by the prostate gland, the rest is produced by the two seminal vesicles.

The prostate also contains some smooth muscle that helps to expel semen during ejaculation.

[edit] Secretions

Prostatic secretions vary between species. They are generally composed of simple sugars, and are often slightly basic.

In human prostatic secretions, the protein content is less than 1% and includes proteolytic enzymes, acid phosphatase, and prostate-specific antigen. The secretions also contain zinc and citric acid.

[edit] Regulation

To work properly, the prostate needs male hormones (androgens), which are responsible for male sex characteristics.

The main male hormone is testosterone, which is produced mainly by the testicles. Some male hormones are produced in small amounts by the adrenal glands.

[edit] Development

The prostate gland represents the modified wall of the proximal portion of the male urethra and develops by the 9th week of embryonic life. Condensation of mesenchyme, urethra and Wolffian ducts gives rise to the adult prostate gland, a composite organ made up of several glandular and non-glandular components tightly fused within a common capsule.

Skene's glands found in many females are homologous to the prostate gland in males.

[edit] Structure

A healthy human prostate is slightly larger than a walnut. It surrounds the urethra just below the urinary bladder and can be felt during a rectal exam.

The ducts are lined with transitional epithelium.

Within the prostate, the urethra coming from the bladder is called the prostatic urethra and merges with the two ejaculatory ducts. (The male urethra has two functions: to carry urine from the bladder during urination and to carry semen during ejaculation.)

The prostate can be divided in two different ways: by zone, or by lobe.

[edit] Zones

The "zone" classification is more often used in pathology.

The prostate gland has four distinct glandular regions, two of which arise from different segments of the prostatic urethra:

Name	Percent	Description
The Peripheral Zone (PZ)	Comprises up to 70% of the normal prostate gland in young men	The sub-capsular portion of the posterior aspect of the prostate gland which surrounds the distal urethra. It is from this portion of the gland that more than 70% of prostatic cancers originate.
The Central Zone (CZ)	Constitutes approximately 25% of the normal prostate gland	This zone surrounds the ejaculatory ducts. Central zone tumours account for more than 25% of all prostate cancers.
The Transition Zone (TZ)	Responsible for 5% of the prostate volume	This zone is very rarely is associated with carcinoma. The transition zone surrounds the proximal urethra and is the region of the prostate gland which grows throughout life and is responsible for the disease of benign prostatic enlargement.
The Anterior Fibro-muscular zone (or stroma)	Accounts for approximately 5% of the prostatic weight	This zone is usually devoid of glandular components, and composed only, as its name suggests, of muscle and fibrous tissue.

[edit] Lobes

The "lobe" classification is more often used in gross anatomy.

anterior lobe (or isthmus)	roughly corresponds to part of Transitional Zone
posterior lobe	roughly corresponds to Peripheral Zone
lateral lobes	spans all zones
median lobe (or middle lobe)	roughly corresponds to part of Central Zone

[edit] Disorders of the prostate

Older men often have corpora amylacea (amyloid), dense accumulations of calcified proteinaceous material, in the ducts of their prostates. The corpora amylacea may obstruct the lumens of the prostatic ducts, and may underlie some cases of benign prostatic hyperplasia.

Inflammation of the prostate gland is known as prostatitis. If the prostate grows too large it may constrict the urethra and impede the flow of urine, making urination difficult and painful and in extreme cases completely impossible. Prostatitis is treated with antibiotics, prostate massage or surgery.

In older men, the prostate often enlarges to the point where urination becomes difficult. This is known as benign prostatic hyperplasia and can be treated with medication or with surgery that removes part of the prostate. The surgery most often used in such cases is called transurethral resection of the prostate (TURP or TUR). In TURP, an instrument is inserted through the urethra to remove prostate tissue that is pressing against the upper part of the urethra and restricting the flow of urine.

Prostate cancer is one of the most common cancers affecting elderly men in developed countries and a major cause of death. Regular rectal exams are recommended for older men to detect prostate cancer early.

[edit] Additional images

Urinary bladder	Structure of the penis	Lobes of prostate	Zones of prostate
Prostate	Prostate under a microscope This image shows the microscopic glands of the prostate	Male Anatomy	The deeper branches of the internal pudendal artery.
Lymphatics of the prostate.	Fundus of the bladder with the vesiculæ seminales.	Vesiculæ seminales and ampullæ of ductus deferentes, seen from the front.	Vertical section of bladder, penis, and urethra.