Bladder
| BLADDER | |
|---|---|
 1. Human urinary system: 2. Kidney, 3. Renal pelvis, 4. Ureter, 5. Urinary bladder, 6. Urethra. (Left side with frontal section) 7. Adrenal gland | |
 Male Bladder Makeup | |
| Details | |
| Precursor | urogenital sinus |
| Artery | Superior vesical artery Inferior vesical artery Umbilical artery Vaginal artery |
| Vein | Vesical venous plexus |
| Nerve | Vesical nervous plexus |
| Lymph | external iliac lymph nodes, internal iliac lymph nodes |
| Identifiers | |
| Latin | vesica urinaria |
| MeSH | D001743 |
| TA98 | A08.3.01.001 |
| TA2 | 3401 |
| FMA | 15900 |
| Anatomical terminology | |
In anatomy, the urinary bladder is the organ that collects urine excreted by the kidneys prior to disposal by urination. A hollow[1] muscular, and distensible (or elastic) organ, the bladder sits on the pelvic floor. Urine enters the bladder via the ureters and exits via the urethra.
Embryologically, the bladder is derived from the urogenital sinus and, it is initially continuous with the allantois. In males, the base of the bladder lies between the rectum and the pubic symphysis. It is superior to the prostate, and separated from the rectum by the rectovesical excavation. In females, the bladder sits inferior to the uterus and anterior to the vagina. It is separated from the uterus by the vesicouterine excavation. In infants and young children, the urinary bladder is in the abdomen even when empty.[2]
Detrusor muscle
The detrusor muscle is a layer of the urinary bladder wall made of smooth muscle fibers arranged in spiral, longitudinal, and circular bundles. When the bladder is stretched, this signals the parasympathetic nervous system to contract the detrusor muscle. This encourages the bladder to expel urine through the urethra.
For the urine to exit the bladder, both the autonomically controlled internal sphincter and the voluntarily controlled external sphincter must be opened. Problems with these muscles can lead to incontinence. If the amount of urine reaches 100% of the urinary bladder's capacity, the voluntary sphincter becomes involuntary and the urine will be ejected instantly.
The urinary bladder usually holds 300-350 mL of urine; a full adult bladder holds about 500mL of urine, 15 times its empty volume. Not all specialists accept these values, some say a urinary bladder can hold ca. 1000 mL, but it is different from person to person. As urine accumulates, the rugae flatten and the wall of the bladder thins as it stretches, allowing the bladder to store larger amounts of urine without a significant rise in internal pressure.[3]
The desire to urinate usually starts when the bladder reaches around 125% of its working volume. At this stage it is easy for the subject, if desired, to resist the urge to urinate. As the bladder continues to fill, the desire to urinate becomes stronger and harder to ignore. Eventually, the bladder will fill to the point where the urge to urinate becomes overwhelming, and the subject will no longer be able to ignore it.
Since the urinary bladder has a transitional epithelium, it does not produce mucus.[4]
Fundus
- ^ Howard A. Werman, MD and Keith J. Karren, PhD.
- ^ Moore, Keith L.; Dalley, Arthur F, Clinically Oriented Anatomy, 5th Edition, 2006 Lippincott Williams & Wilkins
- ^ Marieb, Mallatt Human Anatomy 5th Edition Pearson International Edition Chapter 23 p700
- ^ T . Chin , C . Liu , H . Tsai , C . Wei. Vaginal reconstruction using urinary bladder flap in a patient with cloacal malformation