Anus, rectum and defecation

Question 1

describe the superior and inferior continuation of rectum and where it occurs

Answer 1

• The rectum is part of the GI viscera
• It is continuous superiorly with the sigmoid colon at the level of s3
• Inferiorly it passes through the pelvic diaphragm where it will join to the anal canal at the anorectal junction

Question 2

Describe the AP curvatures of rectum and function

Answer 2

• The first A-P curvature is known as the sacral curvature as it is formed as the rectum follows the concave surface of the sacrum
• The second A-P flexure occurs as the rectum passes through the pelvic diaphragm and is known as the perineal flexure
• The perineal flexure a.k.a anorectal angle is formed from the action of the puborectalis muscle acting like a sling pulling the rectum anteriorly so the anus will extend posteriorly and thus maintains the 80 degrees anorectal angle . If the puborectalis wasn’t working the angle will become more obtuse like in defacation between 110-180 degrees and as a result this can cause fecal incontinence

Question 3

Describe the lateral curvatures of rectum and clinical correlations

Answer 3

• The lateral flexures are classified as superior, intermediate and inferior and they are formed by transverse folds within the wall of the rectum
• The function of these transverse folds is to help slow down the movement of faces as if it all came at once it will lead to too large an urge to defecate they are also important to consider as in an empty rectum they can overlap such that it makes a colonoscopy or sigmoidoscopy difficult

Question 4

Describe the function of rectal ampulla

Answer 4

• The inferior portion of the rectum is expanded to form the rectal ampulla in order to store feaces when it is relaxed

Question 5

state 5 distinguishing features of rectum from other GI

Answer 5

1. flexures A-P and lateral
2. Lack of distnict tenia colli,
3. lack of sacculations (haustra of colon)
4. lack of omental appendices
5. rectal ampulla