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

1 inch infront of coccyx

Location and peritoneal relations of the rectum

S3

12 cm

Shape (flexures) of the rectum

- Anteroposterior curve - 3 flexures

1. Upper concave to left2. lower concave to left3. Middle concave to right

Rectal ampulla

Rectum

In males:

In females

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.

- Recto-uterinepouch, coils of ileum and sigmoid colon. - Posterior wall of vagina.

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

As males

Laterally -LevatorAni - Coccygeus -Pararectal Fossa

As males

Relations of rectum

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 Venous drainage

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.

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)

Blood supply of rectum

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

Internal hemorrhoids•Tributary of sup rectal •Above white line•Generally painless

External hemorrhoids•Tributary of inf rectal•Below white line•Generally painful

Hemorrhoids

11 o’clock

7 o’clock

3 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.

Pectinate line (dentate line)

anal sinus anal valve

  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.

Blood supply, nerve supply and lymph drainage of anal canal:

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.

Pectinate line (dentate line)

anal sinus anal valve

Sphincters of the anal canal

12

The external sphincter

(voluntary)

Vessels and nerves of the anal canal

2 cm

1 ½ cm

½ cm

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