Rectum and Anal Canal Flashcards
Describe the location of the rectum
- starts at rectosigmoid junction at level S3
- follows curve of sacrum and coccyx
- ends in front of the tip of the coccyx by piercing the pelvic diaphragm and becoming continuous with anal canal
Is the rectum peritoneal?
- upper 1/3: covered in peritoneum anteriorly and laterally in C shape
- middle 1/3: only covered anteriorly
- lower 1/3: no peritoneal covering
- peritoneum reflects off of the surfaces it covers to form pouches/fossae
What do the lateral reflections of peritoneum off of the rectum form?
- pararectal fossa
- lateral curvatures coinciding with rectal folds or valves internally
- important for maintenance of continence
How can you distinguish the rectum from the large intestines?
lacks taenia, haustra or epiploic appendices
How are the lateral flexures of the rectum formed?
- by 3 transverse rectal folds
- forms the 3 lateral flexures:
- superior and inferior on left side
- intermediate on right side
Where is the perineal flexure/anorectal angle and how is it formed?
- it is the junction between the rectum and anal canal
- caused by anterior pull of the rectum by the puborectal muscle
- muscle is important in maintenance of continence by preventing leakage of poop into anus
Describe the anatomical relations of the rectum in males
Posterior:
- S3-5, coccyx and anococcygeal ligament
- pelvic plexus
- rectosacral fascia
- median sacral artery
Anterior:
- rectovesical pouch
- bladder
- prostate and fascia
Lateral:
- pararectal fossae
- pudendal plexus
Describe the anatomical relations of the rectum in females
Posterior:
- S3-5, coccyx and anococcygeal ligament
- pelvic plexus
- rectosacral fascia
Lateral:
- pararectal fossae
- pudendal plexus
Anterior:
- rectourterine pouch
- vagina
- rectovaginal fascia
- bladder (most anterior)
What makes up the anorectal ring, where is it located and what is its purpose?
- puborectalis sling
- upper portions of internal and external sphincters
- located at the junction of the anal canal and rectum
- it stays tonically contracted throughout the day to prevent leakage of faeces into the anus/anal canal
Expand on the internal anal sphincter
- smooth muscle
- autonomic
- derived from circular muscular layer
Expand on the external anal sphincter
- striated muscle
- one functional unit with deep, superficial and subcutaneous parts
- fuses with puborectalis
Describe the anatomy of the anal columns
- anal canal has longitudinal folds called anal columns in upper parts
(house branches of superior rectal vein, artery, lymphatics and nerves) - unite at the bottom to form anal valves
- superior to each valve is an anal sinus (depression)
(location of mucous glands that lubricate faeces)
Describe the anatomical importance of the pectinate/dentate line
- where the anal valves in the anal canal form a circle
- above it is the haemorrhoidal zone
- below is a transition zone called the anal pecten
What is the arterial supply of the rectum and anal canal?
- superior 1/3: superior rectal artery (from IMA)
- middle 1/3: middle rectal artery (from internal iliac)
- below anorectal line: inferior rectal artery (from internal pudendal)
- superior rectal artery
Describe how and where you could see the anal cushions
- patient sitting at an angle with legs spread
- 3 anal cushions:
- 11 o’clock
- 7 o’clock
- 3 o’clock