Rectum and Anal Canal

Question 1

At what vertebral level does the rectum start?

Answer 1

S3

Question 2

What epithelium type is found in the rectum?

Answer 2

Simple columnar

Question 3

What are the 2 main flexures in the rectum?

Answer 3

Sacral flexure and anorectal flexure

The sacral flexure follows the curve of the sacrum and coccyx.
The anorectal flexure is formed by the tone of the puborectalis muscle and is very important in faecal continence

Question 4

What is the name of the final part of the rectum?

Answer 4

The ampulla

- this relaxes to accumulate and temporarily store faeces until defecation occurs.

Question 5

Describe the blood supply of the rectum.

Answer 5

Superior, middle and inferior rectal arteries.
- sup from inferior mesenteric
- middle from internal iliac
- inferior from internal pudendal
Superior, middle and inferior rectal veins

Question 6

What is the lymphatic drainage of the rectum?

Answer 6

Pararectal lymph nodes (to inferior mesenteric nodes)

Internal iliac nodes (lymph from lower rectum)

Question 7

What is the autonomic innervation of the rectum?

Answer 7

SNS - lumbar splanchnic and superior&inferior hypogastric plexus

PNS - pelvic splanchnic (from S2-4) and inferior hypogastric plexus

Question 8

What muscle types are found in the internal and external anal sphincters?

Answer 8

Internal - smooth - superior 2/3

External - skeletal - inferior 2/3

Question 9

What is the anorectal ring?

Answer 9

A muscular ring found at the junction of the rectum and anus, which is formed by the fusion of the internal sphincter, external sphincter and puborectalis muscle.

Question 10

What epithelium type is found in the anal canal?

Answer 10

Above the pectinate line: simple columnar

Below pectinate line: non-keratinising stratified squamous

At the anocutaneous line and below: skin - keratinising stratified squamous

Question 11

What is the arterial supply and venous drainage of the anal canal?

Answer 11

Above pectinate line

• superior rectal artery and anastomosing branches from middle rectal artery
• superior rectal vein

Below pectinate line

• inferior rectal artery and anastomosing branches from middle rectal artery
• inferior rectal veins

Question 12

What is the innervation of the anal canal?

Answer 12

Above pectinate line
- inferior hypogastric plexus (visceral)

Below pectinate line
- inferior anal nerves (somatic from pudendal nerves)

Question 13

What is the lymphatic drainage of the anal canal?

Answer 13

Above: internal iliac
Below: superficial inguinal lymph nodes