anal canal - Coggle Diagram
Hemorrhoids are submucosal vascular cushions located within the anal canal.
They occur in three constant positions: Right Anterior, Right Posterior and Left Lateral
Hemorrhoids can be internal (originating above the dentate line/painless), external (originating below the dentate5 line/painful), or mixed
Predisposing factors for hemorrhoids include pregnancy, chronic constipation and prolonged toilet sitting and straining, and any disorder that impedes venous return, including increased intraabdominal pressure.
Internal hemorrhoids (piles) painless: are prolapses of rectal mucosa. more specifically, of rectal cushions containing the normally dilated veins of the internal rectal venous plexus.
External hemorrhoids painfull: are in the veins of the external rectal venous plexus and covered by skin. May thrombose.
C/F: Bleeding, Mass/ Lump, Pruritis, and Pain if thrombosed or ulcerated
Anal fistula or Anorectal
abnormal communication between the anus and the perianal skin
May result from the spread of an anal infection and cryptitis.
Anal canal glands situated at the dentate line afford a path for infecting organisms to reach the intramuscular spaces.
One end of this abnormal canal (fistula) opens into the anal canal and the other end opens into an abscess in the ischioanal fossa or into the perianal skin.
Fistulas can occur spontaneously or secondary to a perianal (or perirectal) abscess.In fact, following drainage of a perianal abscess, there is an approximate 50% chance of developing a chronic fistula
Other fistulae develop secondary to trauma, Crohn's disease, anal fissures, carcinoma, radiation therapy, actinomycoses, tuberculosis, and chlamydial infections.
park's Classification of Perianal Fistulas
Intersphincteric fistulae (70%)
are confined to the intersphincteric space and internal sphincter. Result from perianal abscesses
2.Transsphincteric fistulae (25%)
result of ischiorectal abscesses, with extension of the tract through the external sphincter.
3.Suprasphincteric fistulae (<5%)
are the result of supralevator abscesses. Pass through the levator ani muscle, over the top of the puborectalis muscle, and into the intersphincteric space.
4.Extrasphincteric fistulae (<1%) thru
bypass the anal canal and sphincter mechanism, passing through the ischiorectal fossa and levator ani muscle, and open high in the rectum.
Is a slit like tear in the squamous epithelial mucosa of the distal anal
Occur between the anocutaneous junction and the dentate line
Follow the mechanical tearing , but may involve anodermal ischemia, infection, chronic constipation,
and/or hypertonicity of the smooth muscle of internal anal sphincter
most often occur in the posterior midline, and the reasons for this are both anatomic and functional in nature. The posterior commissure of the anoderm is less well perfused than other regions
Women occasionally have anterior fissures, and lateral fissures typically suggest an unusual diagnosis (Crohn's disease, STD, malignancy).
Is painful - supplied by sensory fibers of the inferior rectal nerves. Perianal abscesses may follow infection of anal fissures
Perianal (60%), ishioranal fossa (30%) or above the level of the levator muscles, creating ischioanal and/or supralevator abscesses, respectively.
Usually begins when bacteria enters anal glands in 90% or tear in the lining of the rectum or anus.
Abscess increases in size, will follow the plane of least resistance and spread towards the surface, creating abscesses elsewhere.
Abscess may rupture spontaneously, opening into the anal canal, rectum, or perianal skin.
Infections may reach the ischioanal (ischiorectal) fossae in several ways:
After cryptitis (inflammation of the anal sinuses).
Extension from a pelvirectal abscess.
After a tear in the anal mucous membrane.
From a penetrating wound in the anal region.
Diagnostic signs of an ischioanal abscess are fullness and tenderness between the anus and the ischial tuberosity.
Because the ischioanal fossae communicate posteriorly through the deep postnatal space, an abscess in one fossa may spread to the other one and form a semicircular horseshoeshaped abscess around the posterior aspect of the anal canal.
The anorectal ring: marks the junction between the rectum and the anal canal . felt digitally, especially on its posterior and lateral aspects.formed by the joining of the puborectalis muscle , the deep external sphincter, conjoined longitudinal muscle and the highest part of the internal sphincter
Anorectal Incontinence:Stretching of the pudendal nerve(s) during a traumatic childbirth can result in pudendal nerve damage and anorectal incontinence
Anal columns (columns of Morgagni), are 5 to 12 longitudinal folds of mucosa in its upper half (each column contains a small artery and a small vein).
The anal valves together form pectinate/dentate line (junction of upper 2/3 and lower 1/3), most important landmark both morphologically and surgically, representing the site of fusion of the proctodaeum and postallantoic gut (hindgut)
Inferior to the pectinate line is a transition zone known as the anal pecten, which is lined by nonkeratinized stratified squamous epithelium.
The anal pecten ends inferiorly at the anocutaneous line ("white line"), or where the lining of the anal canal becomes skin