Rectum and Anal Canal Flashcards
How long is the rectum
12cm
Where is the rectosigmoid junction
S3
Where is the anorectal junction
Pelvic Floor
At the Perineal flexure
At the point where the Puborectalis Muscle forms a U-shaped sling
What is characteristic of the Perineal Flexure?
It annulates the anorectal junction
Annulates = marked with or formed of rings
What is the anorectal ring
The anorectal ring is a muscular structure at the junction of the anal canal and the rectum.
It includes the puborectalis sling and upper portions of the internal and external sphincter
See pl. 372
Describe the rectal flexures
S shaped in coronal plane - when viewed posteriorly
Three curves:
- Superior = lies to right
- Middle= lies to left
- Inferior = lies to right
Contains the Transverse Rectal Folds (Valves of Houston)
See pl. 371
Where is the Rectal Ampulla
In the region of the middle and lower curves
See pl. 346
Explain the relationship of the Rectum with the Peritoneum
Upper third
-Anterior and lateral aspect are covered
Middle third
-Anterior aspect is covered
Lower third
-No peritoneum
Where are the pararectal fossae located
On the lateral sides of the upper third
See pl. 341
What allows for distension of the rectum
Pararectal fossae
Rectovesical septum / Rectovaginal septum
What are the relations of the rectum:
Posterior:
- Lower 3 sacral vertebrae
- Coccyx
- Anococcygeal Lig.
- Sympathetic trunk nerves
- Superior rectal vessels
- Median sacral vessels
Anterior (male):
- Base of bladder
- Terminal ureters
- Ductus deferens
- Seminal vesicle
- Prostate gland
- Rectovesical pouch and Septum
- Sigmoid colon
- Ileum
Anterior (female):
- Posterior fornix of vagina
- Cervix
- Rectouterine pouch
- Sigmoid colon
- Ileum
What is the blood supply of the rectum
Upper part:
-1x Superior rectal a. (from inf. mesenteric a.)
Middle and Inferior parts
-Middle rectal aa. (from int. iliac aa.)
Inferior parts and Anal Canal
-Inferior Rectal aa. (from int. pudendal a.)
What is the venous drainage of the rectum
Superior rectal v. (inferior mesenteric v.)
Middle rectal v. (internal iliac v)
Inferior rectal v. (internal pudendal v.)
This is how a Portacaval anastomes happen
What is the lymphatic drainage of the rectum
Pararectal LN – Superior Half
Internal iliac LN – Lower Half
What is the innervation of the rectum
PNS:
-S2-S4
Visceral afferents and motor function
What is the length of the Anal Canal
2.5 - 4cm
What is the position of the Anal Canal
Descends between:
- Perineal Body
- Anococcygeal Lig
Describe the position and structure of the Anal Sphincters
Puborectalis contributes to the Ext. Anal Sphincter.
Int. Anal Sphincter lies medial to the Ext. Anal Sphincter
What are the features of the internal aspect of the Anal Canal
Anal columns occupy the upper half
Anal Valves (NB - not the same as valve of Houston)
Anal sinuses (filled with mucus)
Pectinate Line
See pl 371
What is the histological structure of the internal aspect of the Anal Canal
Above pectinate line: Columnar Epithelium
Below pectinate line: Stratified Epithelium
Where is the Internal Anal Sphincter located
At the upper two-thirds of the anal canal
What are the effects of the autonomic stimulation of the Internal Anal Sphincter
PNS: Relaxation
What is the position of the External Anal Sphincter
Surrounds the lower end of the anal canal
Lies in the perineum
What are the three parts of the External Anal Sphincter
Subcutaneous:
-No bony attachment
Superficial:
- Attaches from tip of Coccyx to Perineal Body
- Has Anterio-posterior extensions
Deep:
- Fuses with Puborectalis M.
- Fuses with Superficial Transverse Perineal M.
- Arises from Perineal Body
What is the innervation of the External Anal Sphincter
Inferior Rectal Nerves (Pudendal N. – Perineal Br. of S4)
What is the blood supply of the Anal Canal
Above Pectinate Line:
-Superior Rectal Artery
Below Pectinate Line:
-Inferior rectal Arteries
MIDDLE RECTAL ARTERY ANASTOMOSES WITH THE TWO
What is the venous drainage of the Anal Canal
Superior Rectal Vein (To IMV)
Inferior Rectal Vein (To Int. Pudendal V.)
MIDDLE RECTAL VEIN ANASTOMOSES WITH THE TWO
This is a Portacaval anasomosis
See pl 377
What is the innvervation of the Anal Canal
Above Pectinate Line:
-Inferior Hypogastric Plexus (autonomic)
Below Pectinate Line:
-Inferior rectal branches (from Pudendal N)
What is the lymphatic drainage of the Anal Canal
Above Pectinate Line:
-Internal Iliac LN
Becow Pectinate Line
-Superficial Inguinal LN
Describe the Ischiorectal (iscihoanal) fossae
- Fat filled
- Wedge-shaped
- Recesses on either side of anal canal
- Communicate with each other posteriorly over the Anococcygeal Ligament
See pl. 360 and 358
What are the boundaries of the Ischiorectal fossae
Lateral:
- Ischium
- Obturator internus muscle and fascia
Medial:
-Anal canal (surrounded by External anal sphincter)
Anterior:
- Base of urogenital diaphragm
- Body of Pubis
Superior:
-Pelvic Diaphragm
Inferior:
- Superficial perineal fascia
- Skin
Posterior:
- Sacrotuberous Ligament
- Gluteus Maximus
What are the contents of the Ischiorectal Fossae
ischiorectal pad of fat
Perineal br. of S4
Branches of S2 and S3
Pudendal Canal:
- Internal pudendal vessels
- Pudendal Nerve
What are the clinical implications of the ischiorectal fossa
Can form an Ischiorectal Abscess if filled with pus
What are the clincal implications of the Anal Canal
Internal Haemorrhoids - Not sore
External Haemorrhoids - Painful
What are the clincal implications of the Rectum
Recal Prolapse (usually due to sexual insult)
