2. • The large intestine extends from the ileum to the
anus
• It is divided into the cecum, appendix, ascending
colon, transverse colon, descending colon,
sigmoid colon, rectum and anal canal.

3. The primary function of the
large intestine - the absorption
of water and electrolytes and
the storage of undigested
material until it can be
expelled from the body as feces.

4. Location and Description
• The cecum is that part of the large intestine
that lies below the level of the junction of
the ileum with the large intestine.

5. • It is a blind-ended pouch that is
situated in the right iliac fossa.
• . Attached to its posteromedial
surface is the appendix.

7. The cecum is often distended
with gas and can then be
palpated through the anterior
abdominal wall in the living
patient.

8. The appendix communicates
with the cavity of the cecum
through Appendicular valve

12. •Arteries Anterior and posterior cecal
arteries form the ileocolic artery, a branch of the
superior mesentericartery
•Veins The veins correspond to the
arteries and drain intothe
superior mesenteric vein.

13. • Lymph Drainage
• Into the superior mesenteric nodes.
• Nerve Supply
• Branches from the sympathetic and
parasympathetic (vagus) nerves form
the superior mesenteric plexus.

15. Location and Description
•The appendix is a narrow, muscular
tube containing a large amount of
lymphoid tissue.
•It varies in length from 8 to 13 cm

16. The appendix lies in the right
iliac fossa, and in relation to the
anterior abdominal wall

17. base is attached to the
posteromedial surface of the
cecum about 2.5 cm below the
ileocecal junction.

18. • It has a complete peritoneal
covering-the mesoappendix.

20. • Common Positions of the
Appendix
• The tip of the appendix is
subject to a considerable range
of movement and may be found
in the following positions:

22. Blood Supply
•Arteries The appendicular artery is a
branch of the posterior cecal artery.
•Veins The appendicular vein drains
into the posterior cecal vein.
.

23. Lymph Drainage
• into the superior mesenteric
nodes.
Nerve Supply
• The appendix is supplied by the
sympathetic and parasympathetic
(vagus) nerves from the superior
mesenteric plexus.

25. Location and Description
•The ascending colon is about 5 in. (13
cm) long and lies in the right lower
quadrant

27. . It extends upward from the
cecum to the inferior surface of
the right lobeof the liver, where it
turns to the left, forming the right
colic flexure, and becomes
continuous with the transverse
colon..

30. Blood Supply
•Arteries The ileocolic and right colic
branches of the superior mesenteric
artery supply this area.
•Veins The veins correspond to the
arteries and drain into the
superior mesenteric vein.

31. Lymph Drainage
• The lymph vessels drain into the
superior mesenteric nodes.
Nerve Supply
• Sympathetic and
parasympathetic (vagus)
nerves from the superior
mesenteric plexus

33. Location and Description
•The transverse colon is about 15 in.
(38 cm) long and extends across the
abdomen, occupying the umbilical
region.

35. It begins at the right colic
flexure below the right lobe of
the liver and ends at the left
colic flexure below the spleen

39. Blood Supply
• Arteries The proximal two thirds are
supplied by the middle
• colic artery, a branch of the superior mesenteric artery. The distal third is
supplied by the left colic artery, a branch of the inferior mesenteric artery .
• Veins The veins correspond to the
arteries and drain into the
superior and inferior mesenteric veins.

40.  Lymph Drainage
• The proximal two thirds drain into the colic nodes and then
into the superior mesenteric nodes; the
distal third drains into the colic nodes and then into the
inferior mesenteric nodes.
 Nerve Supply
• The proximal two thirds are innervated by
sympathetic and vagal nerves through the
superior mesenteric plexus; the distal third
is innervated by sympathetic and
parasympathetic pelvic splanchnic nerves
through the inferior mesenteric plexus.

41. Location and Description
• The descending colon is about 10 in.
(25 cm) long and lies in the left upper
and lower quadrants .
• It extends downward from the left colic
flexure, & becomes continuous with
the sigmoid colon.

44. Blood Supply
•Arteries The left colic and the
sigmoid branches of the inferior
mesenteric artery supply this area.
•Veins The veins correspond to the
arteries and drain into the
inferior mesenteric vein.

45. Lymph Drainage
• Lymph drains into the colic lymph
nodes and the inferior mesenteric
nodes around the origin of the
inferior mesenteric artery.
Nerve Supply
• The nerve supply is the sympathetic
and parasympathetic pelvic
splanchnic nerves through the inferior
mesenteric plexus.

46. Location and Description
• The sigmoid colon is 10 to 15 in. (25 to 38
cm) long and begins as a continuation of
the descending colon in front of the pelvic
brim.

47. Below, it becomes continuous with
the rectum in front of the 3rd
sacral vertebra.
The sigmoid colon is attached to
the posterior pelvic wall by the
fan-shaped sigmoid mesocolon.

50. Blood Supply
•Arteries :- Sigmoid branches of
the inferior mesenteric artery.
•Veins :- The veins drain into the
inferior mesenteric vein,
which joins the portal venous
system.

51. Lymph Drainage
• The lymph drains into nodes
along the course of the sigmoid
arteries; from these nodes, the
lymph travels to the inferior
mesenteric nodes.

52. Nerve Supply
• The sympathetic and
parasympathetic nerves from the
inferior hypogastric plexuses.

55. Location and Description
• The rectum is about 5 in. (13 cm) long
and begins in front of the third sacral
vertebra as a continuation of the
sigmoidcolon.
• It passes downward, following the curve
of the sacrum and coccyx, and ends in
front of the tip of the coccyx and
becoming continuous with the anal
canal.

56. The lower part of the rectum is
dilated to form the rectal
ampulla.

57. • 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 they vary in
position.

59. Blood Supply
• Arteries
The superior, middle, and inferior rectal arteries
supply the rectum. The
• Veins
The veins of the rectum correspond to the
arteries.

60. Lymph Drainage
• The lymph vessels of the rectum drain
first into the pararectal nodes and then
into inferior mesenteric nodes.
Nerve Supply
• The nerve supply is from the sympathetic
and parasympathetic nerves from the
inferior hypogastric plexuses. The rectum
is sensitive only to stretch.

62. Location and Description
• The anal canal is about 1.5 in. (4 cm) long
and passes downward and backward from
the rectal ampulla to the anus
. Except during defecation, its lateral
walls are kept in apposition

63. • The mucous membrane of the upper half of the anal canal
• is derived from hindgut entoderm. It has the following
important anatomic features:
• ■■ It is lined by columnar epithelium.
• ■■ It is thrown into vertical folds called anal columns, which are
joined together at their lower ends by small semilunar folds called
anal valves (remains of proctodeal membrane).
• ■■ The nerve supply is the same as that for the rectal mucosa and
is derived from the autonomic hypogastric plexuses. It is sensitive
only to stretch.
• ■■ The arterial supply is that of the hindgut—namely, the
superior rectal artery, a branch of the inferior mesenteric
artery. The venous drainage is mainly

64. by the superior rectal vein, a tributary of the inferior mesenteric vein, and
the portal vein.
• ■■ The lymphatic drainage is mainly upward along the superior rectal
artery to the pararectal nodes and then eventually to the inferior
mesenteric nodes. The mucous membrane of the lower half of the
anal canal is derived from ectoderm of the proctodeum. It has the
following important features:
• ■■ It is lined by stratified squamous epithelium, which gradually
merges at the anus with the perianal epidermis.
• ■■ There are no anal columns.
• ■■ The nerve supply is from the somatic inferior rectal nerve; it is thus
sensitive to pain, temperature, touch, and pressure.
• ■■ The arterial supply is the inferior rectal artery, a branch of the
internal pudendal artery. The venous drainage is by the inferior rectal
vein, a tributary of the internal pudendal vein, which drains into the
internal iliac vein.
• ■■ The lymph drainage is downward to the medial group of
superficial inguinal nodes. The pectinate line indicates the level
where the upper half of the anal canal joins the lower half .

67. Muscle Coat
• As in the upper parts of the intestinal tract, it is divided into an outer
longitudinal and an inner circular layer of smooth muscle Anal
Sphincters The anal canal has an involuntary internal sphincter and a
voluntary external sphincter. The internal sphincter is formed from a
thickening of the smooth muscle of the circular coat at the upper end of
the anal canal. The internal sphincter is enclosed by a sheath of striped
muscle that forms the voluntary external sphincter The external
sphincter can be divided into three parts:
• ■■ A subcutaneous part, which encircles the lower end of the anal
canal and has no bony attachments
• ■■ A superficial part, which is attached to the coccyx behind and
the perineal body in front

68. • ■■ A deep part, which encircles the upper end of the anal canal and
has no bony attachments The puborectalis fibers of the two levatores
ani muscles blend with the deep part of the external sphincter . The
puborectalis fibers of the two sides form a sling, which is attached in
front to the pubic bones and passes around the junction of the rectum
and the anal canal, pulling the two forward at an acute angle . The
longitudinal smooth muscle of the anal canal is continuous above with
that of the rectum. It forms a continuous coat around the anal canal and
descends in the interval between the internal and external anal
sphincters. Some of the longitudinal fibers are attached to the mucous
membrane of the anal canal, whereas others pass laterally into the
ischiorectal fossa or are attached to the perianal skin . At the junction of
the rectum and anal canal , the internal sphincter, the deep part of the
external sphincter, and the puborectalis muscles form a distinct ring,
called the anorectal ring, which can be felt on rectal examination.

70. Blood Supply
• Arteries
• The superior artery supplies the upper half and the inferior artery
supplies the lower half .
• Veins :- The upper half is drained by the superior rectal vein into the
inferior mesenteric vein, and the lower half is drained by the inferior rectal
vein into the internal pudendal vein.
Lymph Drainage
• The upper half of the anal canal drains into the pararectal nodes and
then the inferior mesenteric nodes. The lower half drains into the
medial group of superficial inguinal nodes .
Nerve Supply
• The mucous membrane of the upper half is sensitive to stretch and is
innervated by sensory fibers that ascend through the hypogastric
plexuses. The lower half is sensitive to pain, temperature, touch, and
pressure and is innervated by the inferior rectal nerves. The involuntary
internal sphincter is supplied by sympathetic fibers from