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.

Rectum

Location and peritoneal relations of the rectum 12 cm 1 inch infront of coccyx

Shape (flexures) of the rectum - Anteroposterior curve - 3 flexures Upper concave to left lower concave to left Middle concave to right Rectal ampulla

Rectum

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 Anterior Posterior On each side

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

Hemorrhoids Internal hemorrhoids External hemorrhoids Tributary of sup rectal Above white line Generally painless External hemorrhoids Tributary of inf rectal Below white line Generally painful

11 o’clock 7 o’clock 3 o’clock

Lymph drainage of rectum: Upper half drains to para rectal L.Ns which drain to inferior mesenteric L.Ns. 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. 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 1 2

The external sphincter (voluntary)

Vessels and nerves of the anal canal 2 cm 1 ½ cm ½ cm

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