MEDICAL.. ANATOMY.. SURGICAL.. CLINICAL IMPORTANCE

1. ANATOMY OF ANAL
CANAL
Presented by : AYESHA JALIL
Roll# 43

2. What is ANAL CANAL?

3. SURGICAL ANATOMY
 The anal canal is about
1.5”(4 cm) long,
commences at the level
where the rectum passes
through the pelvic
diaphragm, downward and
backward from rectal
ampulla and ends at the
anal verge

5. LOCATION
 PELVIS
 PERINEUM
 ANAL TRIANGLE

9. RELATIONS
POSTERIORLY
Anococcygeal body
LATERALLY
Ischiorectal fossas

10.  ANTERIORLY IN MALE
 Perineal body
 Urogenital diaphragm
 Membranous part of urethra
 Bulb of penis
 ANTERIORLY IN
FEMALE
 Perineal body
 Urogenital diaphragm
 Lower part of vagina

11. STRUCTURE
 EMBRYOLOGY

13. INTERIOR OF ANAL CANAL
Divided by pectineal line & Hilton’s line into 3 areas
1. Upper (15 mm)
2. Intermediate (15 mm)
3. Lower (8 mm)
(Anal verge)
Pectinate / dentate line
Hilton’s line

15. UPPER HALF(2/3) LOWER HALF(1/3)
STRUCTURE
 Mucous membrane of upper
half of anal canal is derived
from hindgut entoderm.
 It is lined by columnar
epithelium
 It is thrown into vertical folds
called anal columns, which
are joined together at their
lower end by semilunar folds
called anal valves(remains of
proctodeal membrane).
 Nerve supply is derived from
autonomic hypogastric plexus.
It is sensitive to stretch only.
 Mucous membrane of lower
half is derived from ectoderm
of anal pit.
 It is lined by stratified
squamous epithelium.
 There are no anal columns
• The nerve supply is from
somatic inferior rectal nerve.;
it is thus sensitive to pain,
temperature, touch and
pressure.

16. BLOOD SUPPLY

17. VENOUS DRAINAGE

18. LYMPHATIC DRAINAGE

19.  The arterial supply is that of
hindgut- superior rectal
artery, branch of inferior
mesenteric artery.
 The venous drainage is by
the superior rectal vein, a
tributary of inferior
mesenteric vein, and the
portal vein.
 The lymphatic drainage is to
the pararectal nodes and
then eventually to inferior
mesenteric nodes.
 The arterial supply is inferior
rectal artery, a branch of
internal pudendal artery.
 The venous drainage is by
inferior rectal vein, a tributary
of the internal pudendal vein,
which drains into the internal
iliac vein.
 The lymphatic drainage is
downward to the medial
group of superficial inguinal
nodes.

20. NERVE SUPPLY

21. IMPORTANT!!!
 When considering metastasis of cancer cells, tumors in
superior part are painless, and those in inferior part painful.

23. MUSCULARIS EXTERNA
 As in the upper parts of GIT, it is divided into an outer
longitudinal and inner circular layer of smooth muscle.

24. ANAL FOLDS AND COLUMNS
 The mucosa and submucosa above the dentate line is
uneven and thrown into folds, the so-called anal cushions.
there are usually three, the left lateral, right posterior and
right anterior positions, and they continue proximally as the
primary rectal foldings. Secondary foldings (the rectal
columns of Morgagni) lie both over and between the primary
folds.

26. MUCOSA SUSPENSORY
LIGAMENT
 the increased density of fibres that insert into the mucosa of
the anal crypts at the level of the dentate line, termed the
‘mucosal suspensory Ligament.

27. INVOLUNTARY INTERNAL VOLUNTARY EXTERNAL
ANAL SPHINCTERS
 2-5 mm of thickening of the
smooth muscle of the
circular coat at the upper
end of the anal canal.
 Supplied by autonomic
plexus and remains in tonic
state of contraction.
 It has three parts
 Subcutaneous
 Superficial
 Deep
 Supplied by pudendal
nerve.

31. ANORECTAL RING
 At the junction of rectum
and anal canal, the internal
sphincter, the deep part of
external sphincter,
conjoined longitudinal
muscle and puborectalis
muscles form anorectal
ring.

32. INTERSPHINCTERIC PLANE
 Between the external
sphincter muscle laterally
and the longitudinal muscle
medially exists a potential
space, the intersphincteric
plane.
 IMPORTANCE
 Contains anal glands
 Route for spread of pus
 The plane can be opened up
surgically to provide access
for operations on the
sphincter muscles.

34. HILTON’S LINE
ALSO CALLED WHITE LINE/ANOCUTANEOUS INE.
It is a color contrast bet’ bluish pink area above and black skin
below.
The line is represented by inter-sphincteric groove at the lower
end of the internal sphincter .
Indicates lower end of internal sphincter.
Ischiorectal abscess when communicates with anal canal
usually opens at or below Hilton’s line.

35. ANAL GLANDS
 Anal glands may be found in the submucosa and
intersphincteric space, and normally number between 0 and
10 in an individual.
 Their function is unknown, although they secrete mucin.
which perhaps lubricates the anal canal to ease defaecation.
 The importance of intersphincteric anal glands is that they
are widely considered to be the potential source of anal
sepsis, either acute, presenting as perianal, ischiorectal or
even pelvic sepsis, or chronic, presenting as a
cryptoglandular (non-specific) anal fistula.