The Anal Canal Flashcards
The anal canal is…
…the final (terminal) segment of the gastrointestinal tract, extending between the rectum and the anus.
The anal canal extends between the…
The rectum and anus
The anal canal has an important role in…
…defecation and maintaining faecal continence
The anal canal connects with the rectum at…
…the point where it passes through a muscular pelvic diaphragm
The Anal Canal is distinguished from the rectum because of…
…the transition of its internal surface from a mucous membrane layer (endodermal) to one of skin-like tissue (ectodermal).
The anal canal is situated…
…below the level of the pelvic diaphragm. It lies in the anal triangle of perineum, in between the right and left ischioanal fossae, which allow its expansion during passage of the faeces.
The sacculations and taeniae are absent in the anal canal. True or false?
True
Dimension of the anal canal
The anal canal is 2.5 to 4 cm (1 to 1.5 inches) in length
Diameter of the anal canal in relation to rectum
Its diameter is narrower than that of the rectum to which it connects.
The anal canal starts from and ends at…
the anorectal junction to the anus.
Direction of the anal canal
From the ano-rectal junction, it passes downwards & backwards through the pelvic diaphragm
The anal canal is surrounded by…
…inner involuntary sphincters which keep the lumen closed in the form of an anteroposterior slit.
The anorectal junction is marked by…
…the forward convexity of the perineal flexure of the rectum
The anorectal junction lies…
…2-3cm in front of and slightly below the tip of the coccyx
What is the anorectal angle at the anorectal junction?
80 degrees
The anal canal opens at…
…the anal orifice situated in the intergluteal cleft 4 cm below & in front of tip of coccyx.
The Ano-rectal junction in males
corresponds to…
…the apex of prostate
The canal is divided into…
…three areas:
- The upper longitudinal folds - anal column
- The lower portion with sphincters
- The anal orifice
The interior of the anal canal is divided by ____ into ____
…by pectinate & Hilton’s line into 3 areas.
Lengths of the divisions of the anal canal
Upper part - 15 mm long
Middle part - 15 mm long
Lower part - 8mm long
Each part of the anal canal is lined by…
…a characteristic epithelium and reacts differently to various diseases of this regions
The upper part of the anal canal is lined by…
…mucous membrane, and is of endodermal origin.
The mucous membrane is made up of ____ folds called… shows:
6 to 10 vertical folds; called the anal columns of Morgagni
The lower ends of the anal columns are united to each other by…
…short transverse folds of mucous membrane called the anal valves.
Above each anal valve, there is…
…a depression in mucosa which is called the anal sinus.
The anal valves together form a…
…transverse line called the pectinate line, that runs all round the anal canal.
The pectinate line is situated…
…opposite the middle of internal anal sphincter, the junction of ectodermal and endodermal parts.
Occasionally, the anal valves show…
…epithelial projections called anal papillae, which are remnants of the embryonic anal membrane
The middle layer of the anal canal is also lined by…
…a mucous membrane
What is the colour of the mucosa of the middle layer of the anal canal?
It has a bluish appearance because of a dense venous plexus that lies between it and the muscle coat.
The mucosa in the upper region is less mobile than in the middle part of the anal canal. True or false?
False. It is more mobile.
The less mobile middle region of the anal canal is referred to as the…
…pecten or transitional zone.
Hilton’s line is situated at…
…the level of the interval between the subcutaneous part of the external anal sphincter and the lower border of internal anal sphincter.
Hilton’s line marks…
…the lower limit of pecten or stratified squamous epithelium which is thin, pale and glossy and is devoid of sweat glands
What is the colour of the lower limit of the pecten?
It is usually whitish and so is referred to as the white base of Hilton
The lower cutaneous part of the anal canal is lined by…
…true skin containing sweat and sebaceous glands.
The epithelium of the lower part of the anal canal resembles…
…that of the true skin in which sebaceous and sweat glands are present.
In terms of musculature, the anal canal is surrounded by…
…internal and external anal sphincters, whichplay a crucial role in the maintenance of faecal continence