Page 129 - Clinical Anatomy

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114 The abdomen and pelvis

‘open weave’ appearance of the bladder wall, readily seen through a
cystoscope.
The circular component of the muscle coat condenses as an (involun-
tary) internal urethral sphincter around the internal orifice. This can be
destroyed without incontinence providing the external sphincter remains
intact (as occurs in prostatectomy).

Cystoscopy
The interior of the bladder and its three orifices (the internal meatus and
the two ureters) are easily inspected by means of a cystoscope. The ureteric
orifices lie 1in (2.5cm) apart in the empty bladder, but when this is dis-
tended for cystoscopic examination, the distance increases to 2in (5cm).
The submucosa and mucosa of most of the bladder are only loosely
adherent to the underlying muscle and are thrown into folds when the
bladder is empty, smoothing out during distension of the organ. Over the
trigone, the triangular area bounded by the ureteric orifices and the internal
meatus, the mucosa is adherent and remains smooth even in the empty
bladder.
Between the ureters, a raised fold of mucosa can be seen called the
interureteric ridge which is produced by an underlying bar of muscle.

Blood supply

Blood is supplied from the superior and inferior vesical branches of the
internal iliac artery. The vesical veins form a plexus which drains into the
internal iliac vein.

Lymph drainage
Lymphatics drain alongside the vesical blood vessels to the iliac and then
para-aortic nodes.

Nerve supply

Efferent parasympathetic fibres from S2 to S4 accompany the vesical
arteries to the bladder. They convey motor fibres to the muscles of the
bladder wall and inhibitory fibres to its internal sphincter. Sympathetic
efferent fibres are said to be inhibitory to the bladder muscles and motor to
its sphincter, although they may be mainly vasomotor in function, so that
normal filling and emptying of the bladder are probably controlled
exclusively by its parasympathetic innervation. The external sphincter is
made up of striated muscle. It is also concerned in the control of micturition
and is supplied by the pudendal nerve (S2, 3, 4). Sensory fibres from the
bladder, which are stimulated by distension, are conveyed in both the sym-
pathetic and parasympathetic nerves, the latter pathway being the more
important.