Bladder (Urinary), Anatomy, Location, Parts and Pictures, by Dr. Chris

Male urinary bladder
male urinary bladder The urinary bladder is a hollow muscular organ located in the lesser pelvis when empty. It serves as a reservoir for urine and can stretch considerably to store close to a maximum of 500 milliliters of urine. The average full bladder that is not overly distended contains about 350 milliliters of urine. It receives urine produced in the kidneys via the ureters and passes it out into the external environment through the urethra.
See also for location of bladder within the body.
See also Elimination of Urine for a similar article, but which explains a few more physiological things.

Anatomy of the Urinary Bladder

Male urinary bladder The empty urinary bladder is somewhat tetrahedral in shape – like a three sided pyramid with a triangular base (illustrated in diagram). This gives the bladder one superior surface (top), two inferolateral surfaces (sides) and a posterior surface (back). The external aspect of the superior surface of the bladder is covered by peritoneum.

The internal surface of the bladder is lined with mucosa, which is folded to form rugae. This makes the internal surface of the bladder rough except for the smooth area of the trigone. The bulk of the bladder wall is composed of the detrusor muscle. which is smooth muscle and therefore under involuntary control.

Parts of the Urinary Bladder

The apex of the bladder points forward towards the pubic symphysis, while the base (fundus) lies posteriorly, against the rectum in males or vagina in females. The neck of the bladder is the inferior aspect where the bladder walls narrow and converge towards the urethra like a funnel. This directs urine into the urethra.

The body of the bladder is the largest part lying between the apex, fundus and neck of the bladder. The trigone of the bladder is a triangle region on the posterior wall. The two ureteric orifices (ureteral opening where the ureters enter) and internal urethral orifice (where the urethra begins) mark the three points of the trigone. It has a slight elevation known as the uvula of the bladder.

The parts of the detrusor muscle towards the neck of the bladder form the internal urethral sphincter. Some fibers run around the neck (radially) for better bladder control. This sphincter closes during ejaculation to prevent backward flow of semen into the bladder in men. The internal urethral sphincter is under involuntary control. The external urethral sphincter which is under voluntary control (skeletal muscle) is formed by the urogenital diaphragm.

Nerve Supply to the Bladder

from upper lumbar spinal cord and inferior thoracic nerves through the hypogastric plexus.
from sacral spinal cord through the pelvic splanchnic nerves and inferior hypogastric plexus.

Blood Supply to the Bladder

Mainly superior vesical arteries and to a lesser extent, the obturator and inferior gluteal arteries
Males: inferior vesical arteries
Females: vaginal arteries
Vesical venous plexus >> internal iliac veins or into the internal vertebral venous plexus
Males: vesical plexus communicates with the prostatic plexus
Females: vesical plexus communicates with the vaginal/uterovaginal plexus

Location of the Urinary Bladder

As it fills with urine, the bladder rises up into the greater pelvis. In infants and children, the bladder is contained within the lower abdomen when empty or full and drops into the greater pelvis around the age of 6 years. After puberty it descends into the lesser pelvis.



Lower Urinary Tract Physiology and Pathophysiology
Jerilyn M. Latini M.D., Assistant Professor, Dept of Urology
University of Michigan, USA

Powerpoint Slides

Bladder Anatomy urinary bladder anatomy
Body Detrusor: main portion of bladder
Responsible for storage and elimination
Trigone Region where ureters enter the bladder
Sphincter Proximal urethra and sphincteric region
Responsible for continence

Neuroanatomy of the Bladder urinary bladder anatomy
Body S2 - S4 parasympathetic (pelvic nerve)
Trigone T11 - L2 sympathetic (hypogastric nerve)
External Sphincter Somatic S2 - S4 (pudendal nerve)

urinary bladder anatomy urinary bladder anatomy

  Normal Infantile Voiding Normal Adult Voiding
1. Detrusor contraction with increase in detrusor pressure Sudden and complete relaxation of the external sphincter
2. Opening of bladder neck Decrease in urethral pressure
3. Sudden and complete relaxation of the external sphincter Detrusor contraction with increase in detrusor pressure
4. Decrease in urethral pressure Opening of the bladder neck
5. Voiding Voiding

Causes of Abnormal Micturition
1. Problems with the “pump” bladder 2. Problems with the “valve” sphincter 3. Problems with the “wiring” innervation
Bladder “Pump” Problems Sphincter “Valve” Problems Neurologic “Wiring” Problems
1. Poorly contractile detrusor
    - Weak detrusor muscle
    - Aging
2. Increased bladder outlet resistance
    - Benign prostatic enlargement
    - Urethral stricture disease
1. Incompetent sphincter
    - Loss of urethral coaptation
    - Loss of muscle support
    - Loss of support to pelvic floor
2. Hyperactive sphincter
    - Inability of the sphincter to relax
    - Sphincteric spasms
1. Loss of afferent innervation
    - Inability to sense bladder fullness
    - Inability to suppress unwanted contractions
2. Loss of efferent innervation
    - Inability to initiate bladder contraction
    - Inability to relax sphincter
3. Loss of both afferent and efferent
    - Loss of coordinated voiding