The trigone (a.k.a. vesical trigone)
is a smooth triangular region of the internal
urinary bladder
The urinary bladder, or simply bladder, is a hollow organ in humans and other vertebrates that stores urine from the kidneys before disposal by urination. In humans the bladder is a distensible organ that sits on the pelvic floor. Urine enters ...
formed by the two
ureteric orifice
The ureters are tubes made of smooth muscle that propel urine from the kidneys to the urinary bladder. In a human adult, the ureters are usually long and around in diameter. The ureter is lined by urothelial cells, a type of transitional epit ...
s and the
internal urethral orifice
The internal urethral orifice is the opening of the urinary bladder into the urethra. It is placed at the apex of the trigonum vesicae, in the most dependent part of the bladder, and is usually somewhat crescent-shaped; the mucous membrane immedi ...
.
The area is very sensitive to expansion and once stretched to a certain degree, the urinary bladder signals the
brain
A brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. It is located in the head, usually close to the sensory organs for senses such as vision. It is the most complex organ in a v ...
of its need to empty. The signals become stronger as the bladder continues to fill.
Embryologically, the trigone of the bladder is derived from the caudal end of
mesonephric ducts
The mesonephric duct (also known as the Wolffian duct, archinephric duct, Leydig's duct or nephric duct) is a paired organ that forms during the embryonic development of humans and other mammals and gives rise to male reproductive organs.
Stru ...
, which is of
mesoderm
The mesoderm is the middle layer of the three germ layers that develops during gastrulation in the very early development of the embryo of most animals. The outer layer is the ectoderm, and the inner layer is the endoderm.Langman's Medical E ...
al origin (the rest of the bladder is
endoderm
Endoderm is the innermost of the three primary germ layers in the very early embryo. The other two layers are the ectoderm (outside layer) and mesoderm (middle layer). Cells migrating inward along the archenteron form the inner layer of the gast ...
al). In the female the mesonephric ducts regress, causing the trigone to be less prominent, but still present.
Pathology
Clinically important because
infection
An infection is the invasion of tissues by pathogens, their multiplication, and the reaction of host tissues to the infectious agent and the toxins they produce. An infectious disease, also known as a transmissible disease or communicable dise ...
s (
trigonitis
Trigonitis is a condition of inflammation of the trigone region of the bladder. It is more common in women.
The cause of trigonitis is not known, and there is no solid treatment. Electrocautery is sometimes used, but is generally unreliable as a ...
) tend to persist in this region.
See also
*
Trigonitis
Trigonitis is a condition of inflammation of the trigone region of the bladder. It is more common in women.
The cause of trigonitis is not known, and there is no solid treatment. Electrocautery is sometimes used, but is generally unreliable as a ...
References
External links
* - "The Male Pelvis: The Urinary Bladder"
{{Authority control
Urinary system