Pelvis - Rectum And Anus

Question 1

1. 1. At what level does the Rectum begin within the pelvis?

1. 2. How does it differ macroscopically from the colon?

Answer 1

1. 1. S3

1. 2. Absence of taemia coli, haustra and omental appendices

Question 2

Peritoneal covering of the rectum

Answer 2

Upper 1/3 - anterior and lateral covered with peritoneum

Middle 1/3 - anterior

Lower 1/3 - no peritoneum

Question 3

Name the vascular supply of the rectum:

1. 1. Arterial
2. 2. Venous

Answer 3

1.1.
Superior rectal artery - terminal branch IMA
Middle rectal artery - branch of IIA
Inferior rectal artery - branch of internal pudendal artery

1.2.
Superior rectal vein - drains into portal venous
Middle rectal vein - drains into systemic
Inferior rectal vein - drains into systemic

Portocaval anastamosis located in the wall of anal canal

Question 4

1. 1. Nerve supply to the rectum

1. 2. Lymphatic drainage

Answer 4

1.1.
Sympathetic - lumbar splanchnic nerves, superior and inferior hypogastric plexus

Parasympathetic - S2-4 via pelvic splanchnic nerves

1.2.
Pararectal lymph nodes - drain into the inferior mesenteric

Lower rectum - directly into internal iliac

Question 5

The anal canal is located within the anal triangle.

Name the anatomical relations of the anal canal

Answer 5

Males:
Anterior - perineal body, urogenital diaphragm, urethra, bulb of penis

Females:
Anterior: perineal body, urogenital diaphragm, vagina

Posterior - anococcygeal ligament, sacrum, coccyx
Lateral - ischioanal fossae

Question 6

Internal anal sphincter is lined by involuntary smooth muscle and the external anal canal by voluntary muscle.

1.1. The anal canal is lined by what type of epithelium?

Answer 6

1.1. Columner epithelium

Question 7

Internal anal sphincter is lined by involuntary smooth muscle and the external anal canal by voluntary muscle.

The anal canal is lined by what type of epithelium above and below the dentate line?

Answer 7

Above dentate line - columner epithelium
Below dentate line - non-keritanized stratified squamous

Transitions below the intersphincteric groove to true keritanized stratified squamous epithelium

Question 8

The dentate (or pectinate) divides the anal canal into upper and lower parts.

Name the difference between

1. 1. Embryological origin
2. 2. Innervation
3. 3. Vascular supply
4. 4. Lymphatics

Answer 8

1.1.
Above dentate line - embryonic hindgut
Below dentate line - ectoderm of the proctoderm

1.2.
Above dentate line - inferior hypogastric plexus - sensitive to stretch
Below dentate line - somatic innervation via the inferior rectal nerve (branch of pudendal)

1.3.
Above dentate line:
Superior and middle rectal artery - superior rectal vein
Below dentate line:
Inferior and middle rectal artery - inferior rectal vein

1.4.
Above dentate line - internal iliac
Below dentate line - superficial inguinal