Rectum

Question 1

Important features of the rectum

Answer 1

Distal part of the large gut.
Placed b/w sigmoid colon and anal canal
Not straight, curved side to side and anteroposteriorly
3 cardinal features of large intestine, sacculations, appendices epiploicae and taeniae are absent

Question 2

Situation of Rectum

Answer 2

Posterior part of the lesser pelvis, in front of the lower 3 pieces of the sacrum and the coccyx

Question 3

Extent of rectum

Answer 3

Begins as a continuation of the sigmoid colon at the level of the S3. The rectosigmoid junction is indicated by the lower end of the sigmoid mesocolon. The rectum ends by becoming continuous with the anal canal.

Question 4

Point of rectosigmoid junction

Answer 4

In males, corresponds to apex of prostate

Generally, 2-3cms and in front of and a little below the tip of coccyx

Question 5

Dimensions of Rectum

Answer 5

12 cm long
upper part (same as that of sigmoid colon) - 4cm diameter 
Lower part forms an ampulla (rectal ampulla)

Question 6

Course and Direction

Answer 6

First runs downwards and backwards and finally downwards and forwards.
The beginning and end is along the median plane but it shows two types of curvatures
2 anteroposterior curvatures - Sacral flexure and perineal flexure
3 Lateral curvatures - Upper, Middle and Lower

Question 7

Curvatures of Rectum

Answer 7

2 anteroposterior curvatures -
Sacral flexure which is along concavity of sacrum and coccyx and,
perineal flexure which is the backwards bend near the anorectal junction

3 Lateral curvatures -
Upper lateral curve which is convex right,
Middle lateral curve which is convex left and,
Lower Lateral Curve which is convex right

Question 8

Peritoneal Relations of the Rectum

Answer 8

Upper 1/3rd covered by peritoneum in front and on the sides.
Middle 1/3rd only in the front
Lower 1/3rd (rectal ampulla) is peritoneal free and lies below the rectovesical pouch in males and rectouterine pouch in females. (Note distance between anus and floor of pouch is 7.5 cm in male and 5.5 cm in female)

Question 9

Visceral Relations of Rectum (MALES)

Answer 9

Ant -
:Upper 2/3rd Rectovesical pouch with coils of intestine and sigmoid colon
:Lower 1/3rd Base of urinary bladder, terminal parts of the ureters, seminal vesicles, ductus deferens and the prostate gland

Post -
:Lower 3 pieces of sacrum, coccyx and anococcygeal ligament
:Pyriformis, coccygeus and levator ani
:Median Sacral, Superior rectal, Lower lateral sacral vessels
:Sympathetic chain with the ganglion impar; the anterior primary rami of S3, S4, S5, Coccygeal 1 and the pelvic splanchnic nerves; lymph nodes, lymphatics and fat.

Question 10

Visceral Relations of Rectum (FEMALES)

Answer 10

Ant -
:Upper 2/3rd Rectouterine pouch with coils of intestine and sigmoid colon (Pouch separates the rectum from the uterus, and upper part of vagina)
:Lower 1/3rd Lower part of vagina

Post -
:Lower 3 pieces of sacrum, coccyx and anococcygeal ligament
:Pyriformis, coccygeus and levator ani
:Median Sacral, Superior rectal, Lower lateral sacral vessels
:Sympathetic chain with the ganglion impar; the anterior primary rami of S3, S4, S5, Coccygeal 1 and the pelvic splanchnic nerves; lymph nodes, lymphatics and fat.

Question 11

Mucosal Folds of the Rectum / Valves of houston

Answer 11

2 types
Longitudinal-
: Transitory and are present in the lower part of the empty rectum. The disappear on distention.

Transverse -
AKA VALVES OF HOUSTON/ PLICAE TRANSVERSALES
Permanent and most prominent in distended rectum
:1st - Near upper end of rectum. Projects from the left wall (about 15cm above anus)
:2nd - LARGEST and most constant. Upper end of rectal ampulla and projects from the anterior and right walls. (about 8 cm above anus)
: 3rd - inconstant, projects from left wall (about 2.5 cm below the 2nd)

Question 12

Developmental Parts of rectum

Answer 12

2 developmental parts -
Upper part, above the third transverse fold, covered by peritoneum and developed from hindgut.
Lower part, below the third transverse fold, not covered by peritoneum and developed from the cloaca

Question 13

Arterial Supply of Rectum

Answer 13

1. Superior Rectal artery - Chief artery of rectum. Continuation of Inferior Mesenteric Artery at the pelvic brim, medial to left ureter. It lies in the medial limb of the pelvic mesocolon and divides opposite S3 into right and left branches which run on each side of the rectum. Each branch breaks up at the middle of rectum into smaller branches which pierce the muscular coat and run in the anal columns upto the anal valves where they form looped anastomoses.
2. Middle Rectal Arteries - Only superficial coats of the lower rectum. Arise from the anterior division of the internal iliac artery, runs in the lateral ligaments of the rectum and supply the muscle coats of the lower rectum. Poor anastomosing
3. Median Sacral Artery - small branch dorsal branch of abdominal aorta near its lower end. it descends in the median plane and supplies the posterior wall of the anorectal junction.

Question 14

Venous Drainage of Rectum

Answer 14

1. Superior Rectal Vein - The tributaries begin in anal canal (from internal rectal venous plexus) in the form of 3 veins of considerable size. Pass upwards in rectal submucosa, pierce the muscular coat close to the second rectal fold, to form the superior rectal vein which drains into the inferior mesenteric vein and then splenic vein.
2. Middle Rectal Vein - Chiefly drain muscular walls of rectal ampulla, and opens into internal iliac vein.
3. Median Sacral Vein - Joins the left common iliac vein.

Question 15

Lymphatic Drainage of Rectum

Answer 15

:More than upper half - along with superior rectal vessels, to inferior mesenteric nodes after passing through sigmoid and pararectal nodes.
:Lower half, along middle rectal to internal iliac nodes
:Lower part of anal canal into superficial inguinal

Question 16

Nerve Supply of Rectum

Answer 16

Through the superior rectal/Inferior mesenteric and inferior hypogastric plexus

Sympathetic - L1,2
Vasoconstrictor, inhibitory to rectal musculature and motor to internal sphincter, Pain sensations along with parasympathetic

Parasympathetic - S2,3,4
Motor to musculature of rectum but inhibitory to internal sphincter. Pain and distension sensations.

Question 17

Supports of Rectum

Answer 17

:Pelvic floor by levator ani
:Fascia of waldeyer- lower part of rectal ampulla attached to sacrum. Formed due to condensation of pelvic fascia behind rectum. (Encloses superior rectal vessels and lymphatics)
:Lateral Ligament of rectum - Attach rectum to posterolateral walls of lesser pelvis. Condensation of pelvic fascia on either side of rectum. (enclose middle rectal vessels, branches of pelvic plexuses)
:Rectovesical fascia of Denonviller - From rectum to behind the seminal vesicles and prostate in front
:Pelvic peritoneum and related vascular pedicles.
:Perineal body with its muscles.