THE URINARY BLADDER ANATOMY AND PHYSIOLOGY
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Transcript of THE URINARY BLADDER ANATOMY AND PHYSIOLOGY
THE URINARY BLADDER ANATOMY AND
PHYSIOLOGY
Dr. Ali Kamal M. SamiM.B.Ch.B. M.A.U.A.F.I.B.M.S. M.I.U.A.
Gross Appearance
A hollow muscular organA reservoir for urineThe adult bladder normally has a capacity of 400–500 ml.
When empty, bladder lies behind the pubic symphysis &it is a pelvic organ.
In infants and children , it is situated higher.
When it is full, it rises above the symphysis and can readily be palpated or percussed.
When over distended, as in acute or chronic urinary retention, it may cause the lower abdomen to bulge visibly.
Extending from the dome of the bladder to the umbilicusis a fibrous cord, the median umbilical ligament, whichrepresents the obliterated
urachus .
Ureters enter the bladder posteroinferiorly are about 5 cm
apart .
The orifices,situated at interureteric ridge that forms the proximal border of the trigone, are about 2.5 cm apart .
The trigone occupies the area between the ridge and the bladder neck.
The internal sphincter, or bladder neck, is not a true
circular sphincter but a thickening formed by interlaced
and converging muscle fibers of the detrusor as they pass
distally to become the smooth musculature of the urethra.
RELATIONSIn males, the
bladder is related
posteriorly to the seminal
vesicles, vasa deferentia,
ureters, and rectum .
In females, the uterus and vagina are
interposed between the bladder and
rectum .The dome and
posterior surfaces are covered by peritoneum.
So in this area the
bladder is related to the small
intestine and sigmoid colon.
The bladder is related to
the posterior surface of
the pubic symphysis,
and, when distended, it is
in contact with the lower
abdominal wall.
Histology
The mucosa of the bladder is composed of transitional
epithelium.
Beneath
it ,is a submucosal layer formed of connective
and
elastic
tissues
External
to the submucosa is the
detrusor muscle
the detrusor muscle which is made up
of a mixture of
smooth muscle fibers
arranged at random
in a longitudin
al, circular,
and spiral manner without
any layer formation or specific orientatio
n
Except close to
the internal meatus, where
the detrusor muscle
assumes 3 definite
layers:Inner longitudinal,
middle circular,and outer
longitudinal.
Blood Supply
A. ARTERIAL
1-Superior Vesical, 2-Middle Vesical, 3-Inferior Vesical arteries, which arise fromthe anterior trunk of the internal iliac (hypogastric)artery, 4-The obturator artery.5-The inferior gluteal artery. In females, the 6-uterine and 7-vaginalarteries also send branches to the bladder.
B. VENOUS
Surrounding the bladder is a rich plexus of veins that ultimately empties into the internal iliac (hypogastric) veins.
LymphaticsThe lymphatics of the bladder drain into 1-the vesical,2-external iliac, 3-internal iliac (hypogastric), 4-common iliac lymph nodes.
Physiology
The nerves concerned in micturition are as follows.
1-The parasympathetic input; derived from the anterior primary divisions of the second, third and fourth sacral segments ( S2 ,S3,S4). These fibers pass through the pelvic splanchnic nerves inferior hypo gastric plexus, from which they are distributed to the bladder.
The pelvic plexus is easily damaged during excisions of the rectum, following which disturbances of micturition and sexual function may occur.
2-The sympathetic input;
These nerves arise in the 11th thoracic to the second lumbar segments (T11,T12,L1,L2). Pass via the presacral hypo gastric nerve and the sympathetic chains to the inferior hypo gastric plexus, which is situated lateral to the rectum, the bladder
3-Somatic innervations;
passes to the distal sphincter through the Pudendal nerves and through the inferior hypo gastric plexus .
The sympathetic nerves convey afferent painful stimuli following over distension of the fundus , from the mucosa where they respond to touch, temperature and pain, and also from the muscle of the detrusor and lamina propria where they convey stretch information. These afferents pass via the inferior hypo gastric plexus . Efferent fibers pass via the pelvic parasympathetics. Normal micturition is coordinated in the Pons in the midbrain where detrusor contraction is timed with inhibition of the distal sphincter mechanism.
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