RECTUM and ANAL RECTUM and ANAL CANALCANAL

RectumRectum

Begins at level of sacral vertebra 3.Begins at level of sacral vertebra 3.Follows curvature of sacrum and coccyx.Follows curvature of sacrum and coccyx.

RectumRectum

Transverse rectal folds:Transverse rectal folds:Three internal infoldings of the mucous Three internal infoldings of the mucous

and and submucous layers.submucous layers.

RectumRectum

Anorectal flexure:Anorectal flexure:At the levator ani muscles.At the levator ani muscles.

Important for fecal continence. Important for fecal continence. Ampulla:Ampulla:

Rests on the pelvic diaphragm.Rests on the pelvic diaphragm.

Holds the fecal mass until defecation.Holds the fecal mass until defecation.

Anal CanalAnal Canal

Internal anal sphincter:Internal anal sphincter:Thick ring of circular smooth muscle.Thick ring of circular smooth muscle.Surrounds upper part of anal canal.Surrounds upper part of anal canal.Controlled reflexively and involuntarily Controlled reflexively and involuntarily by ANS:by ANS:

Parasympathetic system Parasympathetic system promotes relaxation.promotes relaxation.Sympathetic system Sympathetic system promotes contraction.promotes contraction.

Anal CanalAnal Canal

External anal sphincter:External anal sphincter:Three rings of skeletal muscle.Three rings of skeletal muscle.

Extends entire length of anal Extends entire length of anal canal.canal.

Controlled voluntarily via Controlled voluntarily via branches of pudendal nerve.branches of pudendal nerve.

Anal CanalAnal Canal

Anal columns:Anal columns:5-10 longitudinal folds of mucosa in upper 5-10 longitudinal folds of mucosa in upper half of canal.half of canal.

Anal CanalAnal Canal

Pectinate line:Pectinate line:Marks junction between endoderm Marks junction between endoderm portion of anal canal and ectoderm portion of anal canal and ectoderm

portion of anal canal (proctodeum).portion of anal canal (proctodeum).

Marks division between visceral and Marks division between visceral and somatic arterial, venous, lymphatic, and somatic arterial, venous, lymphatic, and nerve nerve supply.supply.

Anal CanalAnal Canal

Pectinate line:Pectinate line:Innervation above the line:Innervation above the line:

Via the ANS.Via the ANS.

Innervation below the line:Innervation below the line:Anococcygeal nerve (PNS).Anococcygeal nerve (PNS).

Anal CanalAnal Canal

Pectinate line:Pectinate line:Lymphatic changes:Lymphatic changes:

Above the line to the cisterna Above the line to the cisterna chyli.chyli.Below the line to superficial nodes. Below the line to superficial nodes.

Arterial supply:Arterial supply:Inferior rectal artery.Inferior rectal artery.

Fig. 3.43Fig. 3.43

Anal CanalAnal Canal

Figures from Moore:Figures from Moore:Vessels of rectum and anal canal:Vessels of rectum and anal canal:

Figure 3.34.Figure 3.34.

Innervation:Innervation:Figure 3.36Figure 3.36