Trigone
Encyclopedia
The trigone is a smooth triangular region of the internal urinary bladder
formed by the two ureteral orifices and the internal urethral orifice
.
The area is very sensitive to expansion and once stretched to a certain degree, the urinary bladder signals the brain
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, which is of mesodermal
origin (the rest of the bladder is endodermal
). In the female the mesonephric ducts regresses, causing the trigone to be less prominent, but still present.
s (trigonitis
) tend to persist in this region.
Urinary bladder
The urinary bladder is the organ that collects urine excreted by the kidneys before disposal by urination. A hollow muscular, and distensible organ, the bladder sits on the pelvic floor...
formed by the two ureteral orifices and the internal urethral orifice
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 immediately behind it presents a slight elevation in males,...
.
The area is very sensitive to expansion and once stretched to a certain degree, the urinary bladder signals the brain
Brain
The brain is the center of the nervous system in all vertebrate and most invertebrate animals—only a few primitive invertebrates such as sponges, jellyfish, sea squirts and starfishes do not have one. It is located in the head, usually close to primary sensory apparatus such as vision, hearing,...
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, which is of mesodermal
Mesoderm
In all bilaterian animals, the mesoderm is one of the three primary germ cell layers in the very early embryo. The other two layers are the ectoderm and endoderm , with the mesoderm as the middle layer between them.The mesoderm forms mesenchyme , mesothelium, non-epithelial blood corpuscles and...
origin (the rest of the bladder is endodermal
Endoderm
Endoderm is one of the three primary germ cell layers in the very early embryo. The other two layers are the ectoderm and mesoderm , with the endoderm as the intermost layer...
). In the female the mesonephric ducts regresses, causing the trigone to be less prominent, but still present.
Pathology
Clinically important because infectionInfection
An infection is the colonization of a host organism by parasite species. Infecting parasites seek to use the host's resources to reproduce, often resulting in disease...
s (trigonitis
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 yet known, and there is no solid treatment yet. Electrocautery is sometimes used, but is generally unreliable as a treatment, and typically does not have quick...
) tend to persist in this region.