Rectum & Anal canal
Objectives
• Discuss the anatomical structure of the rectum.
• Describe the anatomical structure of the anal canal.
• Give the blood supply of rectum and anal canal.
• Define external and internal hemorrhoids.
Beginning:
Course:
Termination:
Begins at the 3rd sacral piece as a continuation of the sigmoid
colon.
Follows the concavity of sacrum& coccyx (sacral flexure).
Ends at the recto-anal junction, about 1 inch in front and
below thetip of coccyx by bending posteriorly (perineal
flexure).
Its lower part is dilated and called ampulla.
Peritoneal covering
Upper 1/3rdfront and sides are covered by peritoneum.
Middle 1/3rd front is only
covered by peritoneum.
Lower 1/3rd has No peritoneal
covering.
Lateral Flexures
&
Mucosal folds
(valves).
Flexures:
1-Upper lateral
flexure.
1-Middle lateral
flexure.
1-Lower lateral
flexure.
Mucosal folds:
2 left mucosal
folds and one right mucosal fold.
Rectum
Location and peritoneal relations of
the rectum
S3
1 inch infront of
coccyx
Shape (flexures) of the rectum
- Anteroposterior curve
- 3 flexures
1. Upper concave to left
2. lower concave to left
3. Middle concave to right
Rectal ampulla
Rectum
In males:
Relations of
rectum
Anterior
- Recto-vesical pouch containing coils of
ileum and sigmoid colon.
- Base of urinary bladder.
- Ampulla of vas deference.
- Seminal vesicles.
- Prostatic gland.
- Terminal part of ureter.
Posterior
Muscles :
(3)
- Piriformis
- LevatorAni
-Coccygeus
Bones:
(2)
- Sacrum
-Coccyx
Vessels:
(2)
- Superior Rectal Artery
- MedianSacral Artery
Nerves:
(3)
- Sympathetic Trunks
- Lower 3 Sacral Nerves
- Coccygeal Nerves
Laterally
-LevatorAni
- Coccygeus
-Pararectal Fossa
In females
- Recto-uterinepouch, coils of ileum and
sigmoid colon.
- Posterior wall of vagina.
As males
As males
Anterior relations of the rectum
Posterior relations of the rectum
Per rectal (PR) examination
•
Knee-chest position
•
Index finger introduced into
lower rectum through anal
orifice
•
Structures palpated
1. Anterior
2. Posterior
3. On each side
Arterial supply
1. Superior rectal artery:
- It is the continuation of inferior
mesenteric artery.
- It supplies the rectum and upper half
of anal canal.
2. Middle rectal artery:
It arises from the anterior division of
internal iliac artery.
3. Inferior rectal artery:
It arises from internal pudendal artery.
Blood
supply of
rectum
Venous drainage
1. Superior rectal vein continues up as
inferior mesenteric vein which drains
into the splenic vein.
(Portal circulation)
2. Middle rectal vein:
Drains into internal iliac vein.
(Systemic circulation)
3. Inferior rectal vein:
Drains into internal pudendal vein.
(Systemic circulation)
Clinical note:
Superior, middle, and inferior rectal veins
anastomose with each other in
submucosa of rectum and anal canal.
Hemorrhoids (piles): is the dilation of
the veins at the site of anastomosis.
Hemorrhoids
(Piles)
Arterial supply of
the rectum and anal
canal
median sacral artery
superior rectal artery
(inferior mesenteric)
middle rectal artery
(internal iliac)
inferior rectal artery
(internal pudendal)
Arteries of the rectum and anal canal
•
•
•
•
Superior rectal
Middle rectal
Inferior rectal
Median sacral
Veins of the rectum
Hemorrhoids
Internal hemorrhoids
•Tributary of sup rectal
•Above white line
•Generally painless
External hemorrhoids
•Tributary of inf rectal
•Below white line
•Generally painful
11 o’clock
3 o’clock
7 o’clock
• Lymph drainage of rectum:
1.Upper half drains to para rectal L.Ns which
drain to inferior mesenteric L.Ns.
2.Lower half drains to internal iliac lymph
nodes.
•
Lymphatic drainage of the rectum
Anal canal
• Beginning: It begins one inch below and anterior to the tip of the
coccyx at the recto-anal junction.
• Course: It runs down and backwards.
• Termination: It ends at the anus.
•
•
•
•
Relations:
Laterally: Ischioanal fossae.
Posteriorly: Anococcygeal raphe between it and tip of coccyx.
Anteriorly: Perineal body between it and bulb of penis in males.
Perineal body between it and vagina in females.
anal sinus
anal valve
Pectinate line
(dentate line)
Blood supply, nerve supply and lymph drainage of anal canal:
Upper part
Lower part
Blood
supply
-It is supplied by superior rectal
artery.
- It is drained by superior rectal vein
(portal circulation).
-It is supplied by:
1- Middle rectal artery of internal iliac
artery.
2. Inferior rectal artery of internal
pudendal artery.
-The corresponding veins drain into internal
iliac vein (systemic circulation.)
Nerve
supply
Above pectinate line by autonomic
nerve fibers.
Below pectinate line by inferior rectal nerve
(Sensitive to pain &touch).
Lymphatic
drainage
Above pectinate line into internal
iliac LNs.
Below the pectinate line into superficial
inguinal LNs.
Anal sphincters:
Internal anal sphincter:
-It is the thickened inner involuntary circular muscle layer of the anal canal.
-Surrounds the upper 3/4th of the anal canal, extending from ano-rectal
junction till the white line (Hilton’s line).
Nerve supply: autonomic
External anal sphincter:
-Striated voluntary muscle fibers.
-Surrounds the whole length of the anal canal outside the internal anal
sphincter.
-Parts: I) Subcutaneous Part:
-Surrounds the anus just under the perianal skin.
-Attached to perineal body &anococcygeal raphe.
II) Superficial Part:
-Surrounds the lower part of the internal sphincter above the subcutaneous
part.
III) Deep Part
Relations of the Anal Canal
• The anal canal is related:
• posteriorly to the fibrous tissue between it
and the coccyx (anococcygeal body),
• laterally to the ischiorectal fossae containing
fat,
• anteriorly to the perineal body separating it
from the bulb
• of the urethra in the male or the lower vagina
in the female.
anal sinus
anal valve
Pectinate line
(dentate line)
Sphincters of the anal canal
2
1
The external sphincter
(voluntary)
Vessels and nerves of the anal canal
2 cm
1 ½ cm
½ cm
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