The Rectum

THE RECTUM (उत्तर गुदम्)

1. AYURVEDA : a. Koshthang : It is one of the koshthang..

                                       b. Avayava : It is matruja avayava..

                                       c. Srotas : Annavaha & Punshvaha..

                         

2. INTRODUCTION : Length : 12 cm

The rectum is the distal part of the large gut. It is placed between the sigmoid colon above & anal canal below. The three cardinal features of the large intestine i.e sacculations, appendices epiploicae & taeniae coli are absent in the rectum. In the upper part it has the same diameter (4 cm) as that of the sigmoid colon, but in the lower part it is dilated to form the rectal ampulla.

3. DEVELOPMENT : The distal part of the hindgut is known as cloaca which is divided by the urorectal septum into primitive anorectal canal posteriorly & vesicourethral canal anteriorly.

Upper part of rectum i.e part above the middle fold of rectum, develops from endoderm of hindgut. This part is related to peritoneum. Lower part, below the middle fold is formed from the dorsal part of the cloaca. It is devoid of peritoneum..

4. LOCATION : It is situated in the posterior part of the lesser pelvis. The rectosigmoid junction (S3) to anorectal junction (in front of tip of coccyx).

❖  COURSE & DIRECTION :

The rectum runs first :-

         1. Downwards then backwards, 2 Downwards & 3. Finally downwards & forwards.

5. RELATIONS : a. Peritoneal :

                        1. The upper 1/3rd is covered with peritoneum.

                        2. The middle 1/3rd is covered only in front.

                        3. The lower 1/3rd which is dilated to form the ampulla which is devoid of peritoneum.

b. Visceral relations :

1. In males : Ant. – upper 2/3rd to the rectovescicle pouch. Lower 1/3rd to the base of urinary bladder, the terminal parts of the ureters, the seminal vesicles, the different ducts & the prostate.

2. In females : Ant – upper 2/3rd to the rectouterine pouch. Lower 1/3rd to the lower part of the vagina. (the pouch seperates rectum from the uterus & upper part of vagina.)

Posterior - (same in male & female) :

1. Lower 3 pieces of sacrum & coccyx. 2. Piriformis, the coccygeous & levator ani.  3. The median sacral, the superior rectal and the lower lateral sacral vessels..

6. MUCOSAL FOLDS : Two types of folds, 1. Longitudinal folds are present in the lower part of an empty rectum, and are obliterated by distention.

                        2. The transverse or horizontal folds : are permanent and most marked when the rectum is distended. A. Upper fold lies near the upper end of the rectum and projects the right or left wall. B. The middle or the largest fold lies at the upper end of the rectal ampulla and projects from the anterior and right walls. C. The lowest fold lies 2.5cm below the middle fold and projects from the left wall.

                         

7. FUNCTIONS : It’s distention causes the desire to defeacate.

8. A. ARTERIAL SUPPLY :

1. Superior rectal artery : It’s main artery (Branch of Inferior messenteric artery).

2. Middle rectal arteries : Branches of anterior division of internal iliac artery.

3. Median sacral artery : Small branch of aorta.

B. VENOUS DRAINAGE :

1. Superior rectal vein drain into inferior messenteric vein .

2. Middle rectal veins drain into internal iliac veins.

C. LYMPHATIC DRAINAGE :

1. Lymphatics from upper half drains into pararectal & sigmoid nodes.

2. Lymphatics from the lower half drains into iliac nodes.

D. NERVE SUPPLY : 1. Sympathetic – L1 & L2.  2. Parasympathetic – S2, S3 & S4.

❖  Supports of Rectum:

1. Pelvic floor.

2. Fascia of waldeyer : It attaches the lower part of rectum to the sacrum. ( condensation of pelvic fascia)

3. Lateral ligaments of rectum : Rectum to posterolateral walls of lesser pelvis.

4. Rectovesical fascia (of Denovilliers) : It extends from the rectum behind to the seminal vesicles & prostate in front.

5. The pelvic peritoneum.

❖  Applied Anatomy:

1. P.R. examination : A. In males - we can palpate prostate, seminal vesicles & vasa deferential.

B. In females - perineal body, cervix.

C. In both – anorectal ring, coccyx, sacrum, ischiorectal fossae.

                         

2. Proctoscopy & Sigmoidoscopy.

3. Prolapse of rectum : A. Incomplete - prolapse of rectum through the anus may occur following violent straining. This is due to imperfect support of the rectal mucosa by submucosa which is made up of loose areolar tissue.

B. Complete – is the condition in which the whole thickness of rectal wall protrudes through the anus. The contributory factors in its causation are : 1. Laxity of the pelvic floor.

2. Excessively deep rectovesical pouch.