The tunica albuginea is the fibrous envelope that extends the length of the

corpus cavernosum penis A corpus cavernosum penis (singular) (from Latin, characterised by "cavities/ hollows" of the penis, : corpora cavernosa) is one of a pair of sponge-like regions of erectile tissue, which contain most of the blood in the penis of several animal ...

and

corpus spongiosum penis The corpus spongiosum is the mass of spongy tissue surrounding the male urethra within the penis. It is also called the corpus cavernosum urethrae in older texts. Structure The proximal part of the corpus spongiosum is expanded to form the ...

. It is a bi-layered structure that includes an outer longitudinal layer and an inner circular layer.

Structure

Microstructure

The

trabecula A trabecula (: trabeculae, from Latin for 'small beam') is a small, often microscopic, biological tissue, tissue element in the form of a small Beam (structure), beam, strut or rod that supports or anchors a framework of parts within a body or ...

e of the tunica albuginea are more delicate, nearly uniform in size, and the meshes between them smaller than in the corpora cavernosa penis: their long diameters, for the most part, corresponding with that of the

penis A penis (; : penises or penes) is a sex organ through which male and hermaphrodite animals expel semen during copulation (zoology), copulation, and through which male placental mammals and marsupials also Urination, urinate. The term ''pen ...

. The external envelope or outer coat of the corpus spongiosum is formed partly of unstriped muscular fibers, and a layer of the same tissue immediately surrounds the canal of the

urethra The urethra (: urethras or urethrae) is the tube that connects the urinary bladder to the urinary meatus, through which Placentalia, placental mammals Urination, urinate and Ejaculation, ejaculate. The external urethral sphincter is a striated ...

. It consists of approximately 5%

elastin Elastin is a protein encoded by the ''ELN'' gene in humans and several other animals. Elastin is a key component in the extracellular matrix of gnathostomes (jawed vertebrates). It is highly Elasticity (physics), elastic and present in connective ...

, with the remainder mostly consisting of

collagen Collagen () is the main structural protein in the extracellular matrix of the connective tissues of many animals. It is the most abundant protein in mammals, making up 25% to 35% of protein content. Amino acids are bound together to form a trip ...

Function

The tunica albuginea is directly involved in maintaining an erection; that is due to

Buck's fascia Buck's fascia (deep fascia of the penis, Gallaudet's fascia or fascia of the penis) is a layer of deep fascia covering the three erectile bodies of the penis. Structure Buck's fascia is continuous with the external spermatic fascia in the scro ...

constricting the erection veins of the penis, preventing blood from leaving and thus sustaining the erect state.

Additional images

File:Normal penis ultrasound.jpg,

Medical ultrasonography Medical ultrasound includes Medical diagnosis, diagnostic techniques (mainly medical imaging, imaging) using ultrasound, as well as therapeutic ultrasound, therapeutic applications of ultrasound. In diagnosis, it is used to create an image of ...

of a normal penis

References

External links

* - "The Male Perineum and the Penis: The Corpus Spongiosum and Corpora Cavernosa"
Image at downstate.edu

Image at downstate.edu
*
Encyclopedia of Reproduction
{{DEFAULTSORT:Tunica Albuginea (Penis) Mammal male reproductive system Human penis anatomy