This document provides an overview of the anatomy of the rectum and anal canal. It describes the rectum as beginning at the S3 vertebra and ending at the tip of the coccyx, where it continues as the anal canal. Key points include: - The rectum has two anterior-posterior curves and three lateral curves that allow it to fit within the pelvis. - The anal canal can be divided into upper, middle, and lower parts. The upper part contains anal valves and crypts, while the middle part is stratified squamous epithelium. - Both structures are supplied by branches of the inferior mesenteric artery and drained by corresponding veins. Lymphatic drainage is to internal

1. RECTUM & ANAL CANAL
DR.LOVELY JAIN
Department of Anatomy
N.S.C.B.Medical College
Jabalpur(M.P.)

2. Rectum
 ≈ 5 in. (13 cm) long
 Begins in front of the S3 vertebra as a
continuation of the sigmoid colon
 Ends in front of the tip of the coccyx by
piercing the pelvic diaphragm and
becoming continuous with the anal canal
 The lower part of the rectum is dilated to
form the rectal ampulla

3. Rectum - Course and Direction
 Two A-P curves
Sacral flexure
◼ follows concavity of the
sacrum and coccyx
Perineal flexure
◼ convex forwards at
anorectal junction
◼ Maintained by the
pubo-rectal sling of the
levator ani
 Three lateral curves
Upper – convex to the
right; S3 and 4
vertebrae
Middle – convex
to left, SC junction
Lower – convex to
right; tip of coccyx
.

6. Histology
 Peritoneum
anterior and lateral surfaces of the 1st third
anterior surface of the middle third
 Muscular coat: outer longitudinal and inner
circular layers of smooth muscle
 The mucous membrane of the rectum, together
with the circular muscle layer, forms two or
three semicircular permanent folds called the
transverse folds of the rectum

8. SUPPORT S Of Rectum
.

9. LevatorAni
. Anterior fibers
Prostate and vaginal
support
 Intermediate fibers
The puborectalis forms
a sling around the
junction ofthe rectum
and anal canal
The pubococcygeus
passes posteriorly to be
inserted into a small
fibrous mass, called the
anococcygeal body,
between the tip of the
coccyx and the anal canal
 Posterior fibers
The iliococcygeus is
inserted into the
anococcygeal body
and the coccyx

10. Rectum - Relations .
 Anteriorly
(female)
Upper 2/3 - the
sigmoid colon
and coils of
ileum that
occupy the
rectouterine
pouch (pouch
of Douglas)
Lower 1/3 -
posterior surface
of the vagina

11. Rectum – blood supply
 The superior rectal artery
IMA
chief artery supplying the mucous membrane
It enters the pelvis by descending in the root of the sigmoid mesocolon
and divides into right and left branches, which pierce the muscular coat
and supply the mucous membrane
They anastomose with one another and with the middle and inferior
rectal arteries
 The middle rectal artery
small branch of the internal iliac artery and isdistributed mainly to
the muscular coat
 The inferior rectal artery
branch of the internal pudendal artery in the perineum
Anastomoses with the middle rectal artery at the anorectal junction

13. Rectum – venous drainage
. Correspond to the arteries
 The superior rectal vein
tributary of theportal circulation and
drains into the IMV
 The middle and
inferior rectal veins
drain into the
internal iliac and
internal pudendal
veins,
respectively
The union between
the rectal veins
forms an important
portal systemic
anastomosis

14.  Upper part
lymph vessels accompany the SRA
and drain into IMN
 Lower part
follow the MRA to the internal iliac
nodes
 Sympatheitic
Superior
hypogastric
plexus (L1,2)
Primarily
vasomotor;
stimulate the
internal
sphincter
 Parasympathetic
Pelvic splanchnic
nerves
• (S1,2,3)
Secretomotor to the
glands
Stimulate peristalsis
Relax sphincters
Lymphatics Nerve Supply

15. Digital Rectal Examination  Ano-rectal sling, ischiorectal fossa, ischial spines
 Males
Posterior surface of prostate
Seminal vesicles
Vas deferens
 Females
Perineal body
Cervix
Clinical uses of DRE
Evaluation:-
Rectal masses
Prostatic disorders (tumours and BPH)
Haemorrhoids
 Gynecological palpations:- of internal organs
 Estimation of the tonicity:- of the anal
sphincter
fecal incontinence
neurologic diseases, including traumatic spinal cord
injuries
 Examination of stool:-
 Prior to a colonoscopy or proctoscopy :-
In newborns to exclude imperforate anus
.

17. Terminal part of the alimentary tube
Begins at ano-rectal junction and opens at the anal orifice
2.5 – 5 cm
Upper, middle and lower parts

18. Anal Canal – Upper part
 Dentate line
2cm proximal to anal verge; anal valves
 Anal crypts
Mucous glands to provide lubrication during defecation
If blocked ---> nidus for abscess and fistula
 Columns of Morgagni
Squamous to pink columnar (rectum)
 Arterial
Superior rectal artery
 Lymphatics
Internal iliac nodes
 Nerve supply
Sympathetic – inferior hypogastric plexus (L1,2)
Parasympathetic – pelvic splanchnic nerve (S1,2,3)
Sensitive to stretch/distension

19. Middle part/ Pecten
15 mm
Between dentate and white
(Hilton’s) lines
Stratified squamous non-
keratinized
Shiny, blue
Lower part
8mm
Below white line; true
skin
Sweat and sebaceous glands
 Arterial
Middle and inferior rectal a.
 Lymphatics
Superior inguinal nodes
 Nerve supply
Inferior rectal nerve (S2,3,4)
Sensitive to pain, temp, touch

20. Anal Canal - Relations
 Anterior
Perineal body
Bulb of the penis and spongy urethra(males)
Lower part of the posterior wall of the vagina
(females)
 Posterior
Ano-coccygeal ligament, tip of the coccyx, fibro-
fatty tissue
 Ischiorectal fossa

21. Anal SphinctersInternal
Involuntary
Formed by the
thickening of the circular
muscle coat
Surrounds the upper
3cm of the anal canal
Lies above the
SC part and deep
tot eh superficial
and deep parts of
the external
sphincter
Externa
• Voluntary; surrounds the entire
length of the anal canal
• Subcutaneous
• Below the level of the internal
sphincter; surrounds the
• lower part as a flattened band
• Superficial
• Elliptical; arises from the tip of
the coccyx and anococcygeal
body ---> perineal body
• Deep
• Surrounds the upper part of the
internal sphincter; fused with the
puborectalis

23. Thank You