Wall consists of mucosa, submucosa, and two complete muscle layers, inner circular, outer longitudinal.
12-15cm in length, reflection is 6-8cm above anus.
Upper 1/3 ant/lat covered by peritoneum, middle 1/3 only anteriorly covered, lower 1/3 completely retroperitoneal.
The rectum starts where tenia coli coalesce to form a complete layer of longitudinal muscle at level of sacral promontory.
Three distinct curves, proximal and distal curve to the right, middle curves to the left. These folds are called Valves of Huston. This area is great for biopsy purposes as they do not contain all layers so risk of perforation is less.
Waldeyer’s fascia is a dense connection between sacrum and rectum at 4th sacral body goes anteriorly to rectum, covering sacrum and overlying vessels and nerves.
Dennonviller’s fascia is a retrovesical septum in men, rectovaginal in women.
Pelvic floor is musculotendinous sheet formed by the levator ani muscle and is innervated by S4.
The pubococcygeus, iliococcygeus, and puborectalis make the levator ani. These are paired muscles that are intertwined and act as a unit.
The anal canal starts at pelvic diaphragm and ends at anal verge. Approximately 4cm long. The anatomic anal canal extends from anal verge to dentate line. Surgical anal canal is anal verge to anorectal ring, the circular upper border of puborectalis that is palpable by rectal exam. It is 1-1.5 cm from dentate line.
The anal verge is the junction between anoderm and perianal skin.
The dentate line is a true mucocutaneous junction located 1-1.5 cm from anal verge. A 6-12mm transitional zone exists above the line where squamous becomes cuboidal, then columnar.
Anal sphincter mechanism made by internal and external sphincters.
The internal sphincter is a specialized continuation of the circular smooth muscle layer of the rectum. It is involuntary, and contracted at rest.
The intersphincteric plane is a fibrous continuation of the longitudinal smooth muscle layer of the rectum..
These cushions are thought to act as a plug to the anal canal, and contribute 15-20% to the resting pressure of the anal canal. There are three of these cushions 11,3,7 o'clock.
Abnormal swelling of the cushions result in prolapse of the upper anal/lower rectal tissue thru the anal canal. This causes the symptoms of hemorrhoids: bleeding, discomfort, pruritis, prolapse, swelling, pain, discharge.
Bleeding is the most common symptom, pain is not common, unless a associated fissure is present (20%), or it’s a thrombosed external.
Classification of internal hemorrhoids.
Classification of Internal Hemorrhoids
I- Bleed, but do not prolapse.
II- Spontaneous prolapsing and reducing with or without bleeding.
III- Prolapsing,that require manual reduction.
IV- Prolapsed, cannot reduce...