Tunica vaginalis
Encyclopedia
The tunica vaginalis is the serous covering of the testis.
It is a pouch of serous membrane
, derived from the processus vaginalis
of the peritoneum
, which in the fetus
preceded the descent of the testis from the abdomen
into the scrotum
.
After its descent, that portion of the pouch which extends from the abdominal inguinal ring to near the upper part of the gland becomes obliterated; the lower portion remains as a shut sac, which invests the surface of the testis, and is reflected on to the internal surface of the scrotum; hence it may be described as consisting of a visceral and a parietal lamina.
, connecting the latter to the testis by means of a distinct fold.
From the posterior border of the gland it is reflected on to the internal surface of the scrotum.
The inner surface of the tunica vaginalis is smooth, and covered by a layer of simple cuboidal endothelial cells.
The interval between the visceral and parietal laminæ constitutes the cavity of the tunica vaginalis.
It is a pouch of serous membrane
Serous membrane
In anatomy, serous membrane is a smooth membrane consisting of a thin layer of cells which secrete serous fluid. Serous membranes line and enclose several body cavities, known as serous cavities, where they secrete a lubricating fluid which reduces friction from muscle movement...
, derived from the processus vaginalis
Processus vaginalis
The processus vaginalis is an embryonic developmental outpouching of the peritoneum.It is present from around the 12th week of gestation, and commences as a peritoneal outpouching.-Gender differences:...
of the peritoneum
Peritoneum
The peritoneum is the serous membrane that forms the lining of the abdominal cavity or the coelom — it covers most of the intra-abdominal organs — in amniotes and some invertebrates...
, which in the fetus
Fetus
A fetus is a developing mammal or other viviparous vertebrate after the embryonic stage and before birth.In humans, the fetal stage of prenatal development starts at the beginning of the 11th week in gestational age, which is the 9th week after fertilization.-Etymology and spelling variations:The...
preceded the descent of the testis from the abdomen
Abdomen
In vertebrates such as mammals the abdomen constitutes the part of the body between the thorax and pelvis. The region enclosed by the abdomen is termed the abdominal cavity...
into the scrotum
Scrotum
In some male mammals the scrotum is a dual-chambered protuberance of skin and muscle containing the testicles and divided by a septum. It is an extension of the perineum, and is located between the penis and anus. In humans and some other mammals, the base of the scrotum becomes covered with curly...
.
After its descent, that portion of the pouch which extends from the abdominal inguinal ring to near the upper part of the gland becomes obliterated; the lower portion remains as a shut sac, which invests the surface of the testis, and is reflected on to the internal surface of the scrotum; hence it may be described as consisting of a visceral and a parietal lamina.
Visceral lamina
The visceral lamina (lamina visceralis) covers the greater part of the testis and epididymisEpididymis
The epididymis is part of the male reproductive system and is present in all male amniotes. It is a narrow, tightly-coiled tube connecting the efferent ducts from the rear of each testicle to its vas deferens. A similar, but probably non-homologous, structure is found in cartilaginous...
, connecting the latter to the testis by means of a distinct fold.
From the posterior border of the gland it is reflected on to the internal surface of the scrotum.
Parietal lamina
The parietal lamina (lamina parietalis) is far more extensive than the visceral, extending upward for some distance in front and on the medial side of the cord, and reaching below the testis.The inner surface of the tunica vaginalis is smooth, and covered by a layer of simple cuboidal endothelial cells.
The interval between the visceral and parietal laminæ constitutes the cavity of the tunica vaginalis.
External links
- Diagram at aspiruslibrary.org - "Inguinal Region, Scrotum and Testes: Tunic"
