Urinary Bladder of Animals
The urinary bladder is a musculo-membranous sac, differs in form, size and position according to the amount of its contents.
Urinary bladder of Ox
- When contracted, it is a dense pyriform mass about the size of a fist and lies on the ventral wall of the pelvic cavity at a variable distance behind the pelvic inlet
- When moderately full, it is oval in shape and extends into the abdominal floor. Its capacity is about 3 to 4 litres.
- The bladder has 3 parts-a vertex, a body and neck
- The cranial part or the vertex is a blind end and presents in its middle a rounded cul-de-sac called as cicatrix – the vestige of the urachus, which forms a connection between the bladder and the allantois in the fetus
- The middle part or body is rounded and somewhat flattened from above downwards
- It presents two surfaces- superior and inferior which are convex when full
- The caudal narrow extremity is the neck and it joins the urethra
Relations of Urinary Bladder
- They vary according to the amount of the contents and sex
- The ventral surface is related to the floor of the pelvis and extends into the abdomen as it distends
- The dorsal surface in the male is related to the rectum, the genital fold, and the terminal parts of the vas deferens, the seminal vesicle and the prostate
- In the female, it is related to the body of uterus and vagina. When the bladder is full, the vertex reaches the rumen and small intestine
Ligaments of Urinary Bladder
- The bladder is fixed in position by three peritoneal folds -the ligaments of the bladder
- The ventral or middle ligament is a median triangular fold extends from the ventral face of the bladder to the floor of the pelvis and abdomen
- In the newborn animal, it is extensive and reaches to the umbilicus
- The lateral ligaments are two and extend on either side of the lateral aspects of the bladder to the lateral wall of the pelvis. Each contains in its free edge a round cord the round ligament, which is the remnant of the fetal umbilical artery
- The caudal part of the bladder has no peritoneal covering and is attached to the surrounding parts by fat and connective tissue.
- The mucous membrane is pale, thin and is loosely attached to the submucous tissue
- It forms numerous folds when bladder is empty and contracted
- It is modified over a triangular area on its dorsal wall close to neck called the trigonum vesicae where the mucous membrane is firmly attached without any folds
- The two cranial angles of the trigonum vesicae present the openings of the two ureters and the caudal angle shows the opening of the bladder into the urethra -internal urethral orifice
- The two urethral orifices are placed near each other on either side of the median line. From each urethral orifice, a fold of mucous membrane passes backward and inward, uniting with its fellow to form a median urethral crest in the first part of urethra.
- The terminal part of ureter after piercing the muscular coat of the bladder and passes for a distance of about 2.5 cm between the muscular and mucous coats before piercing the latter
- This arrangement constitutes a valve, which prevents the return of urine from the bladder into ureter
- The internal urethral orifice lies at the apex of the trigonum
Urinary bladder of Sheep and Goat
Urinary bladder of Sheep and Goat is same as Ox.
Urinary bladder of Horse
Urinary bladder of horse is Shorter but wider. It does not extend into the abdomen as forward as in the ox. Caudal part of the bladder is retro peritoneal.
Urinary bladder of Pig
Urinary bladder of Pig is relatively very large. When full, it is abdominal in position.
Urinary bladder of Dog
When urinary bladder of dog is empty, it is pelvic in position and when full it is entirely abdominal in position.
Urinary bladder of Rabbit
Urinary bladder of Rabbit is little elongated. It is a thin walled sac supported by median ligament of the bladder ventrally, the remnant of the ventral mesentery.
Urinary bladder of Fowl
The ureters open into the urodeum of the cloaca. So there is no bladder in Fowl.