ABDOMINAL CAVITY - University of Kansas Medical Center
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Transcript ABDOMINAL CAVITY - University of Kansas Medical Center
RECTUM and ANAL
CANAL
Rectum
Begins at level of sacral vertebra 3.
Follows curvature of sacrum and coccyx.
Rectum
Transverse rectal folds:
Three internal infoldings of the mucous and
submucous layers.
Rectum
Anorectal flexure:
At the levator ani muscles.
Important for fecal continence.
Ampulla:
Rests on the pelvic diaphragm.
Holds the fecal mass until defecation.
Anal Canal
Internal anal sphincter:
Thick ring of circular smooth muscle.
Surrounds upper part of anal canal.
Controlled reflexively and involuntarily
by ANS:
Parasympathetic system
promotes relaxation.
Sympathetic system
promotes contraction.
Anal Canal
External anal sphincter:
Three rings of skeletal muscle.
Extends entire length of anal
canal.
Controlled voluntarily via
branches of pudendal nerve.
Anal Canal
Anal columns:
5-10 longitudinal folds of mucosa in upper
half of canal.
Anal Canal
Pectinate line:
Marks junction between endoderm
portion of anal canal and ectoderm
portion of anal canal (proctodeum).
Marks division between visceral and
somatic arterial, venous, lymphatic, and
nerve supply.
Anal Canal
Pectinate line:
Innervation above the line:
Via the ANS.
Innervation below the line:
Anococcygeal nerve (PNS).
Anal Canal
Pectinate line:
Lymphatic changes:
Above the line to the cisterna
chyli.
Below the line to superficial nodes.
Arterial supply:
Inferior rectal artery.
Fig. 3.43
Anal Canal
Figures from Moore:
Vessels of rectum and anal canal:
Figure 3.34.
Innervation:
Figure 3.36