Physiology of urinary bladder and urethra, normal and pathological

Abstract

Urinary bladder. The urinary bladder is a musculo-membranous hollow organ that acts as a reservoir for the urine. In the newborn it is ovoid and lies chiefly in the abdomen, adjacent to the ventral abdominal wall. Its base is located behind the symphysis pubis. With growth and development it assumes a lower position. In the adult, when empty, it lies wholly within the pelvis; when distended it extends above the symphysis pubis and becomes in part an abdominal organ. Its form and relationships, consequently, vary according to the volume of liquid it contains. When empty, it has the form of a flattened tetrahedron, with its vertex directed toward the upper border of the symphysis pubis. From the vertex the middle umbilical ligament extends upward to the umbilicus. This ligament is covered by a fold of peritoneum, the middle umbilical fold. The fundus is directed downward and backward. It is triangular in shape and separated from the rectum by the rectovesical fascia, the seminal vesicles and the terminal portions of the ductus deferentes. The triangular superior surface is bounded on either side by a lateral border which separates it from the inferior surface. Posteriorly the superior surface is separated from the fundus by a line joining the two ureters. From the lateral borders, which extend from the ureters to the vertex, the peritoneum is reflected to the walls of the pelvis. A depression of the peritoneum on either side of the bladder is called the paravesical fossa. When the bladder is moderately full it assumes an oval form, the long diameter of which measures about 12 cm. and is directed upward and forward. In this condition it exhibits a ventro-caudal, a dorso-rostral, and two lateral surfaces, a summit and a fundus. The fundus is more or less fixed; consequently, it is only slightly depressed, as the viscus fills, but the rostral surface gradually rises into the abdominal cavity carrying with it the peritoneal covering.