Urinary bladder: anatomy, location and function

The urinary bladder (Vesica) is a hollow muscular organ that stores urine before it leaves the body. In adults, it lies mainly in the pelvis, behind the pubic symphysis, the joint joining the pubic bones. As it fills, it expands upwards and may extend into the lower abdomen.

Where is the urinary bladder located?

The bladder belongs to the lower urinary tract, which includes the bladder and urethra. The urethra is the tube carrying urine from the bladder to the exterior. Within the urinary system, the ureters carry urine from the kidneys into the bladder.

When empty in adults, the bladder lies within the lesser pelvis, the space below the pelvic brim. Its position and shape change as it fills. Loose connective tissue between the bladder and the pubic symphysis allows expansion without fixing its front wall tightly to the bone.

In males, the bladder lies in front of the rectum, the terminal part of the large intestine, and above the prostate gland. The seminal vesicles, glands contributing fluid to semen, lie behind its base. In females, the bladder lies in front of the vagina, with the uterus above and behind it.

The peritoneum, the membrane lining the abdominal cavity and covering many abdominal organs, covers the bladder’s superior surface. Most of the remaining bladder lies outside this membrane. As the bladder enlarges, its upper surface rises and lifts the associated peritoneum.

What are the main parts of the urinary bladder?

The bladder is described in terms of its apex, body, fundus and neck. These names identify regions rather than separate compartments. An empty bladder has a superior surface and inferolateral surfaces, which face downwards and to either side; these become less distinct as it fills.

The apex connects towards the umbilicus through the median umbilical ligament. This is the fibrous remnant of the urachus, an embryonic channel associated with the developing bladder. The bladder neck is supported by surrounding pelvic connective tissue; in males, it rests on the prostate.

How is the bladder wall structured?

The inner lining is urothelium, a specialised epithelium, or covering tissue, whose cells accommodate stretching. Beneath it lies connective tissue, followed by the detrusor muscle. The detrusor is the smooth muscle of the bladder wall; smooth muscle contracts without voluntary control.

When the bladder is empty, much of its lining forms folds called rugae. These flatten as the wall stretches. The trigone is a smooth triangular region on the internal base, bounded by the openings of the ureters and the internal urethral opening, where the urethra begins.

The trigone remains comparatively smooth during filling because its lining is firmly attached to the underlying tissue. The ureters pass obliquely through the bladder wall before opening into it. Compression of these passages as the bladder fills helps limit backward flow towards the ureters.

The urinary bladder neck smooth muscle surrounds the outlet region. In males, smooth muscle here also helps prevent semen from passing into the bladder during ejaculation. It should not be confused with the external urethral sphincter, a separate skeletal muscle that provides voluntary control of the urethral outlet.

How does the urinary bladder store and release urine?

During storage, the bladder wall accommodates incoming urine while the outlet remains closed. The detrusor stays relatively relaxed, and the urethral sphincters help maintain closure. A sphincter is muscle arranged to control an opening.

Emptying is called micturition. It requires coordinated contraction of the detrusor and relaxation of the urethral outlet. The bladder therefore functions as a temporary reservoir rather than producing urine, which is formed in the kidneys.

What supplies blood to the bladder, and where does lymph drain?

The superior vesical artery supplies the upper bladder and arises from the patent, or open, part of the umbilical artery. In males, the inferior vesical artery commonly supplies the lower bladder. In females, vaginal arteries contribute to this region, with additional contributions from uterine arteries.

Veins drain into the vesical venous plexus, a network of interconnected veins around the bladder. This plexus drains towards the internal iliac veins, the major veins receiving blood from pelvic structures.

Lymph, fluid collected from tissues by lymphatic vessels, passes mainly to external and internal iliac lymph nodes. These nodes lie along the corresponding pelvic blood vessels. Drainage from the bladder neck also reaches sacral lymph nodes, near the sacrum at the back of the pelvis.

Which nerves control the urinary bladder?

Bladder control involves the autonomic and somatic divisions of the nervous system. Autonomic nerves regulate involuntary activity, while somatic motor nerves control skeletal muscle, including the external urethral sphincter.

Parasympathetic fibres, an autonomic pathway carried in the pelvic splanchnic nerves from sacral spinal levels S2–S4, stimulate detrusor contraction during emptying. Sympathetic fibres, another autonomic pathway, reach the bladder through pelvic nerve networks and support storage by promoting detrusor relaxation and outlet contraction.

Sensory fibres convey information about bladder stretching to the spinal cord. The pudendal nerve supplies the external urethral sphincter, allowing voluntary control to work alongside the reflex pathways governing bladder emptying.

How can you locate the bladder in the 3D model?

In the 3D model beside this article, rotate and zoom to choose a viewing angle. Select, hide or isolate structures, or fade them and switch layers to adjust the view. You can also pull parts apart to compare their spatial relationships from different viewing angles.

Cut a section along the sagittal, coronal or transverse plane to change the view. A sagittal plane divides left and right portions, a coronal plane divides anterior and posterior portions, and a transverse plane divides superior and inferior portions.