The document summarizes key anatomical features of the small and large intestines. It describes the parts, positions, lengths, and arterial supply of the small intestine. It also details differences between the jejunum and ileum. For the large intestine, it outlines the caecum, appendix, and parts of the colon including the transverse and pelvic colons. It compares features of the small and large intestines and describes peritoneal coverings and blood supply of parts of the large bowel.

1. ‫الرحي‬ ‫الرحمن‬ ‫هللا‬ ‫بسم‬
‫م‬
SMALL & LARGE INTESTINES

2. Jejunum
Ileum
Duodeno-
jejunnal
flexure
Ileo-coecal
junction
Duodenum

3. Small Intestines
- Position : in the infracolic comparment of the
greater sac occupying the central and lower part of
abdomen
- Beginning : at the pyloro-duodenal junction
- Termination : at the iliocaecal junction
- Length : it is 6 meters (20 feet)
- Parts: formed of 3 parts:
a)Duodenum:1st10 inches & fixed to post. abd. wall
b)Jejunum: 8 feet& form proximal 2/5 of small intest.
c)Ileum: 12 feet &form distal 3/5 of the small
intestine. it joins the caecum at the iliocaecal valve.

5. b) The jejunum & ileum
- Small intestine proper extends from the
duodenojejunal flexure to the ileocaecal junction.
- Its upper two-fifth forms the jejunum and its
lower three-fifth forms the ileum. However, there
is no definite line of demarcation.
- The jejunum and ileum are suspended from the
posterior abdominal wall by a large fold of
peritoneum called the mesentery of small intestine;
hence, the small intestine enjoys a considerable
mobility.

6. Jejunum
Ileum
Duodeno-
jejunnal
flexure
Ileo-coecal
junction
Duodenum

7. jejunum ileum
Part proximal 2/5 of the small intestine distal 3/5 of the small intestine
Length 8th feet long 12th feet long
Site lies more to umbilical region lies more to hypogastric region
Lumen wider than ileum Narrower than jejunum
Wall Thick mucosa due to active
absorption & thick musculosa due to
active peristalsis
thin mucosa & musculosa due to less
active digesion & absorption)
Circular Folds Circular folds of the mucosa are
numerous
the mucosa contains less Circular
folds
Peyers
Patches
aggregation of lymphoid follicles in
the submucosa are absent
Many Peyers patches in the
submucosa along antimeesenteric
border of ileum
Arteries The jejunal arteries : forming one or
2nd arches in the mesentery of
jejunum (simple arterial arcades)
The ileal arteries : Forming 3rd to 5th
arches in the mesentery of ileum
(complicated arterial arcades)
Mesentery Contains less fat allowing light to pass
in the spaces between
arteries(windows of mesentery)
Contains dense fat which mask the
arteries ( no windows)
Layers At operation, the jejunal wall is felt as
double layer
At operation, the ileal wall is felt as
single layer

8. ARTERIAL SUPPLY:
The jejunum and ileum are supplied by the jejunal
and ileal branches (12-15 in number) of the superior
mesenteric artery.
The terminal part of the ileum is supplied by the
ileal branches of the ileocolic branch of the superior
mesenteric artery.
As soon as these enter the mesentery they break up
into smaller branches which anastomose with each
other to form a series of arterial arcades which are
more complex in the ileum than in the jejunum.
From the convexities of the terminal arcades, small
parallel straight vessels called “vasa recta” arise and
pass to the mesenteric border of the gut to be
distributed alternatively to the opposite surfaces of
the small intestine.
VENOUS DRAINAGE: corresponding to the branches
of superior mesenteric artery and drain into the portal
vein.

9. Jejunum Ileum
Arterial arcades
Windows

10. Middle colic
Inferior pancreatico-
duodenal
Rt colic
Jejunal ileal
branches
Ileo-colic

11. Mesente
Root of mesentery
MESENTERY OF THE SMALL INTESTINE
- Definition: peritoneal fold enclosing the free
part of small intestine (jejunum & ileum )
connecting it to the post. abd. wall
- Shape: Fan shaped fold having broad free
border & narrow attached border
a) The free border: 6th meters (20 feet) long &
encloes jejunum & ileum
b) attached border: (root of mesentery) :
- 6th inches long & 6 inches away from the free
border
- It is attached to post. abd. wall extending
from : the duodeno-jejunal flexure (on LT. side
of L2) to the ileocaecal junction (above the RT.
sacroiliac joint).

12. - Contents of mesentery :
1) coils of jejunum & ileum in the free margin of the mesentery.
2) superior mesenteric a. & its branches.
3) superior mesenteric vein & its tributaries.
4) lymphatics & 3 raws of mesenteric L.Ns.
5) plexuses of autonomic nerve fibers around the arteries.
6) extraperitoneal fatty tissue.
S M A
Duodeno
jejunal
flexure
Root of
mesentery
Structure crossed by
root of mesentery
Aorta
3rd part of duodenum
Abdominal aorta
Inferior vena cava
Right gonadal vessels
Right ureter
Right psoas major
Ileocaecal junction
- the root crosses 6th structures on the post.
Abdominal wall
(2 parts of duodenum, 2 large vessels & 2 muscles)
1) the 4th part of duodenum.
2) The 3rd part of duodenum.
3) The abdominal aorta.
4) The inferior vena cava.
5) The RT. psoas major m. with structures on it (
RT. ureter, RT. gonadal vessels & RT.
genitofemoral n.)
6) The RT. iliacus m.

13. LARGE INTESTINE
- Length: about 1.5 m long and
- Extensions: from the caecum in the right iliac fossa to the anus in the perineum.
- Functions:
1. Absorption of water from fluid contents in it to help form the feces.
2. Storage, lubrication, and expulsion of feces.
3. Synthesis of vitamin B complex by normal bacterial flora present its lumen.
4. Protection from invasion by microorganisms by its mucoid secretion which is rich in
IgA group of antibodies.
- Parts: divided into the following four parts:
1. Caecum and appendix.
2. Colon: is further divided into four parts:
-ascending colon. -transverse colon.
- descending colon. -sigmoid colon
1. Rectum.
2. Anal canal.

14. CARDINAL FEATURES of the large intestine
a) Teniae Coli
- Defintion: three ribbon-like bands of the
longitudinal muscle coat.
- Extensions: converge proximally at the base of
the appendix and spread out distally to become
continuous with the longitudinal muscle coat of
the rectum.
- Location:
 In the caecum, ascending colon&descending
colon, the positions of teniae are anterior (Teniae
libera), posteromedial (Teniae mesocolica), and
posterolateral (Teniae omentalis).
 in the transverse colon the corresponding
positions are inferior, posterior, and superior,
respectively.

15.  Appendices Epiploicae
- Defintion: small bags of visceral peritoneum
filled with fat attached to the teniae of large
intestine.
- Thus, they are absent in the appendix,
rectum, and anal canal and most numerous
on the sides of sigmoid colon and posterior
surface of the transverse colon.
 Sacculation (or Haustrations)
- Defintion: a series of pouches/dilatations in
the wall of caecum and colon between the
teniae.
- They are produced because length of teniae
fall short of the length of circular muscle
coat.

17. Features Small intestine Large intestine
Length 6 m 1.5 m
Lumen Narrower Wider
Mobility More Less
Transverse
mucous folds
Permanent and not
obliterated by
distension of the gut
Temporary and obliterated
by distension of the gut
Villi Present Absent
Peyer's patches Present Absent
Appendices
epiploicae
Absent Present
Teniae coli Absent Present
Sacculation Absent Present
•
Differences between the small and large intestines:

18. Taenia coli
Subcecal
Pelvic
Pre-& post-ileal Meso-
appemdix
Retrocecal
- Site: in the RT. iliac fossa above the lat. 1/2
of the inguinal ligament
- Surface anatomy: A triangular area in the
RT. iliac fossa bounded by :
a) Above: intertubercular plane.
b) Below: lat. 1/2 of the inguinal ligament.
c) Medially: RT. lat. vertical plane.
- Shape & size: a blind pouch 3 inches long
(closed below & open above)
- Communications:
a) above: it is continuous with ascending
colon
b) medially: it is communicates with the
terminal part of ileum via ileocaecal valve
c) posteromedially: the appendix open into it
about 1 inch below ileocaecal valve
- Peritoneal covering : completely covered
with peritoneum & related to 3 peritoneal
recesses
Caecum

19. McBurney’s point
Appendix
- Site: in the RT. iliac fossa, attached to the postero-medial
aspect of caecum one inch below the ileocaecal valve.
- Size: 1.5-9 inches ( it is the narrowest part of gut)
- Shape: worm like tube, closed distally but open proximally
into the caecum
- Peritoneal covering : Completely covered by peritoneum &
suspended by peritoneal fold called mesoappendix
- Positions of the appendix:
1. Paracolic (11 o'clock) position:
2. Retrocaecal/retrocolic (12 o'clock) position:
3. Splenic (2 o'clock) position:
4. Promonteric (3 o'clock) position:
5. Pelvic (4 o'clock) position:
6. Midinguinal/subcaecal (6 o'clock) position:
Arterial supply: appendicular artery; a branch of the
ileocolic artery from (sup. mesenteric a.).

21. ASCENDING COLON DESCENDING COLON
Length 5 - 8 (6 inches) inches 10-12 inches
DIAMETER Wider Naroower
Peritoneal
covering
Partially covered
[Front & sides ]
Beginning =In right iliac fossa
=From upper end of
caecum
in LT. lumbar & LT. iliac
regions, descending from the
LT. colic flexure above.
Termination =In right hypochondrium
=At right colic flexure
the LT. border of pelvic brim
below by becoming the
sigmoid (pelvic) colon.
upper & lower left colic
arteries from Inferior
mesenteric artery
RT. colic a. & ascending br. of
ileocolic a. from Superior
mesenteric artery
Arterial supply

22. Superior mesenteric artery
Superior mesenteric plexus
Vagus nerves
Inferior mesenteric artery
Inferior mesenteric plexus
Pelvic splanchnic nerve (S2,3,4)

23. Upper Lt colic
Lower Lt colic
Inferior mesenteric artery

24. Features Right colic flexure Left colic flexure
Location lumbar region (where it is related to
the inferior surface of right lobe of the
liver)
Left hypochondrium (immediately
below the spleen)
Level 1 inch (2.5 cm) below the transpyloric
plane, at the level of L2 vertebra
1 inch (2.5 cm) above the transpyloric
plane, at the level of T12 vertebra
Angulation Wider Acute
Attachment
to
diaphragm
No attachment Attached to diaphragm at the level of
10th and 11th ribs by phrenicocolic
ligament
Arterial
supply
RT. colic a. LT. colic a.
Colic flexures

25. T R A N S V E R S E
&
P E L V I C
C O L O N S

26. Length
PELVIC COLON
SIGMOID COLON
TRANSVERSE
COLON
16 inches
5-35 may
18-20 inch

27. Beginning
PELVIC COLON
SIGMOID COLON
TRANSVERSE
COLON
=At left side of
pelvic inlet.
=Continuation of
descending
colon.
=At right
hypochondrium
=At right colic
flexure.
=In front of 2nd
part of
duodenum.

28. PELVIC COLON
SIGMOID COLON
TRANSVERSE
COLON
=At left side of
pelvic inlet.
=Continuation of
descending
colon.
=At right
hypochondrium
=At right colic
flexure.
=In front of 2nd
part of
duodenum.

29. Termination
PELVIC COLON
SIGMOID COLON
TRANSVERSE
COLON
=Ends at level of
S 3
=To become
Rectum
=At left
hypochondrium
=At lateral margin
of left kidney.
=Continues as left
colic flexure.

30. PELVIC COLON
SIGMOID COLON
TRANSVERSE
COLON
=Ends at level of
S 3
=To become
Rectum
=At left
hypochondrium
=At lateral margin
of left kidney.
=Continues as left
colic flexure.

31. Course

32. TRANSVERSE COLON
=Crosses abdomen.
=From right colic to left colic flexures.
=Little below umbilicus.
=Along its course ,
it forms an arch which is convex
downwards & forewords

33. PELVIC COLON (SIGMOID COLON)
=[ S ] shaped course.
=It has three parts:-
1st part:-
descends in contact with pelvic wall.
2nd part:-
=crosses pelvic cavity
=Between:-
♀:- ♂:-
uterus [anterior] urinary bladder[ant.]
rectum[posterior] rectum [post.]
3rd part:-
=arches backwards
=reaches median plane at S 3
=it bends downwards and continues as
Rectum

34. Peritoneal covering
PELVIC COLON
TRANSVERSE COLON
=Completely covered
with peritoneum.
=It is suspended to
posterior abdominal
wall by pelvic
mesocolon
=Completely covered
with peritoneum.
=EXCEPT:-
at its beginning where
the transverse colon lies
directly in front of
duodenum.
=It is suspended to
posterior abdominal wall
by transverse mesocolon

35. ARTERIAL SUPPLY
PELVIC COLON
TRANSVERSE COLON
Sigmoid branches of
of inferior
mesenteric artery.
Right 2/3:- S.M.A.
1- Right colic artery.
2- Middle colic artery.
Left 1/3:- I.M.A.
Left colic artery

36. VENOUS DRAINAGE
PELVIC COLON
TRANSVERSE
COLON
Inferior mesenteric
vein.
Right 2/3:- S.M.V.
 Left 1/3 :-I.M.V.

37. TRANSVERSE MESO-
COLON
PELVIC MESO-
COLON
DEFINITION =It is a fold of peritoneum.
=Which encloses transverse
colon.
=Connects it to posterior
abdominal wall
=It is a fold of peritoneum.
=Which encloses pelvic
colon.
=Connects it to posterior
abdominal wall
ATTACHMENT:- Free border:-
encloses transverse colon
Attached border [root]:-
attached to front of :-
1]=Head of pancreas
2]=Body of pancreas
(anterior border)
Free border:-
encloses pelvic colon
Attached border [root]:-
=Inverted V shaped line
medial limb:-
=on pelvic surface of sacrum.
=ends opposite S 3
lateral limb:-
=along left side of pelvic inlet.
=from ing. Lig. [ant.] to
Lt. C.I.A. [post.]
apex:- on Lt. C.I.A.
CONTENTS:- Transverse colon
Middle colic artery.
‫المشهورة‬ ‫الأربعة‬
Pelvic colon in free border
Superior rectal art.in medial li
Sigmoid vessels in lateral lim.
‫المشهورة‬ ‫الأربعة‬

38. RECTUM

39. • lies in the post part of pelvic cavity
infront of lower 1/2 of sacrum.

40. • It is 5 inches long
• Its upper part is 1.5 inch in diameter
while its lower part is dilated to form
the rectal ampulla (2.5 inches) in
diameter

41. • opposite the 3rd sacral piece as the
continuation of the sigmoid
(pelvic)colon

43. • one inch below & infront of the coccyx & sharply
downward & backwards to form the anal canal

44. a) Antero-posterior curves (flexures):
1)sacral curve (flexure): concave forwards,
following the concavity of sacrum.
1)perineal curve (flexure): convex
forwards, at the ano-rectal junction.
a) lateral curves (flexures):
1)upper : convex to the RT. side
2)middle: convex to the LT. side
3)lower: convex to the RT. side
Lower lateral curvature
Anal canal
Upper lateral curvature

48. 1) Upper 1/3 : covered on front & sides.
2) Middle 1/3: covered on the front only.
Lower 1/3 : has no peritoneal covering
Upper 1/3rd of rectum
Peritoneum
Middle 1/3rd of rectum
Peritoneum
Lower 1/3rd of rectum

49. - Mucosal folds of the rectum ( huostons valves):
• The interior of the rectum presents two types of mucosal folds:
1) Temporary folds: mostly longitudinal and found in the lower part of the
rectum. They disappear when rectum distends.
2) Permanent folds (Houston’s valves):
 Semilunar (crescentic) transverse folds situated against the concavities of
the lateral curvatures of the rectum.
 They are permanent and become more prominent when the rectum is
distended. they are four in number:
a) First fold: near the upper end & projects from RT or LT wall.
b) Second fold: lies about 1 inch (2.5 cm) above the third fold.
c) Third valve: the largest, most constant, and most important..
d) Fourth valve: projects from left wall &about 2.5cm below third valve.
Third transverse fold
Second transverse fold

50. - Differences between the rectum & other parts of
large intestine:
1)the rectum lacke of the 3 characters of the large
intestine(taenia coli – sacculations – appendices
epiploicae).
2)the rectum has no mesentery

52.  superior rectal artery : (single artery)
 Begins infront of LT. common iliac artery as direct
continuation of the inf. mesenteric a.
 Middle rectal arteries ( RT. & LT.):
 Each artery arises from the ant. division of the
corresponding int.iliac a.
 median sacral artery:
 It is a single artery which arises from the back of
lower end of abd. Aorta.
 Inferior rectal arteries (RT. & LT.):
 Each artery arises from internal pudendal artery
in the pudendal canal.

54.  superior rectal vein (portal) : continues upward as
the inferior mesenteric vein which drains into the
splenic vein (portal system).
 Middle rectal vein (systemic) (RT. & LT.):
drain into the internal iliac vein (systemic
vein).
 Inferior rectal vein (systemic) (RT. & LT. ): runs
laterally in the ischiorectal fossa in company
with inf. rectal a.) to end in the internal
pudendal vein.

56. - Lymphatic drainage:
 lymphatics of upper 1/2 of rectum follow sup. rectal a. to drain into:
a) pararectal L.Ns on each each side of the rectum
b) L.Ns in the sigmoid mesocolon along sup. rectal vessels
c) inf. mesenteric L.Ns around origin of inf. mesenteric a.
•
a) lymphatics of the lower 1/2 of rectum pass along the middle rectal
vessels to drain into internal iliac L.Ns
- Nerve supply of the rectum:
a) parasympathetic fibers : derived from S2,3,4 via pelvic splanchnic n.
b) sympathetic fibres: from L1,2 through the inf. mesenteric plexus

57. - SUPPORTS OF THE RECTUM:
 The rectum is kept in position and prevented from prolapse by;
1) Pelvic diaphragm: formed by the levator ani muscles.
2) Fascia of Waldeyer: a connective tissue behind the rectum. It extends from
the lower part of rectal ampulla to the sacrum and coccyx.
3) Lateral ligaments of the rectum: These are fibrous bands formed by the
condensation of pelvic fascia one on each side of the rectum.
4) Rectovesical fascia of Denonvilliers.
5) Reflection of pelvic fascia from parietal to visceral layers around the rectum.
6) Pelvirectal and ischiorectal fat act as a loose packing material around the
rectum and anal canal.
7) Pelvic peritoneum and related vascular pedicles.
8) Perineal body.

58. ANAL CANAL

59. • 1inch below & infront of coccyx as
acontinuation of the rectum
• Direction: downwards
& backwards
- Ends: at the anal orifice
- Length: 1.5 inch (4cm)

60. 1”
1”

62.  Formed of striated muscle fibres
 Surrounds the whole length of anal canal
 lies outside the internal anal sphincter
 it is voluntary & supplied by somatic nerves
(inf. rectal n. & S4)
 consistes of 3 parts: deep, superficial &
subcutaneous

63. Circular muscle coat of rectal
wall
Longitudinal muscle coat of
rectal wall Puborectalis
Pectinate line
Conjoint longitudinal coat of
anal canal
Anal valve
Perianal fascia
Perianal space
Fibroelastic septa
Anal column
Internal anal sphincter
Deep part
Superficial part
Subcutaneous part
Pecten

66. Anorectal sling of
puborectalis
Anococcygeal raphe
External anal sphincter
Pubic symphysis
Perineal body
Anal canal
Rectum
Superficial part
Subcutaneous part

67.  It is the continuation of the circular muscle
layer of rectum
 It surrounds the upper 2/3 of the anal canal
 It begins at the anorectal junction & ends at
the white line
 It is involuntary sphincter & supplied by
autonomic nerves

68. a)Ano-rectal ring:
 It is muscular ring at the junction of the rectum &
anal canal
 It is formed by the fusion of 4muscular structures :
 Pubo-rectalis part of levator ani.
 deep part of ext. anal sphincter
 the longitudinal muscle layer
 the internal anal sphincter

69. B. Internal anal sphincter:
A. External anal sphincter
Smooth muscle fibers
striated muscle fibers
Surrounds upper 2/3 of anal canal
Surrounds lower 2/3 of anal canal
Involuntary
Voluntary
=Supplied by autonomic nerves:-
1.Parasympathetic :-
pelvic nerve (S2,3 & 4)
2.Sympathetic :
pelvic splanchnic nerves..
=Supplied by somatic nerves:-
1.Perineal branch (S4)
2.Inferior rectal from pudendal
nerve.

73. Circular muscle coat of rectal
wall
Longitudinal muscle coat of
rectal wall Puborectalis
Pectinate line
Conjoint longitudinal coat of
anal canal
Anal valve
Perianal fascia
Perianal space
Fibroelastic septa
Anal column
Internal anal sphincter
Deep part
Superficial part
Subcutaneous part
Pecten

74. Internal Of THE Upper PART OF ANAL CANAL
• Anal columns (columns of Morgagni): These are permanent
longitudinal mucous folds numbering 6 to 10. They contain radicles
of the superior rectal vein.
• Anal valves (valves of Morgagni): These are crescentic folds of the
mucous membrane which connect the lower ends of adjacent anal
columns. The free margins of these valves are directed upward. The
position of these valves is indicated by the wavy pectinate line (also
called dentate line).
• Anal sinuses: These are vertical recesses between the anal
columns and above the anal valves. The ducts of tubular anal
glands present in the submucosa open in the floor of anal sinuses.
•

75. Internal of THE LOWER PART OF ANAL CANAL
• Upper region (often called pecten): It is 15 mm long and extends
from the pectinate line to Hilton's line. It is lined by the non-
keratinized stratified squamous epithelium. The mucous lining in
this region appears bluish in colour due to underlying dense
venous plexus and is adherent to the underlying structures.
• Lower region of lower anal canal: It is about 8 mm in extent and
lined by the true skin containing sweat and sebaceous gland. It
shows pigmentation. In adult males, coarse hairs are often found
around the anal orifice.

76. Lower part
Upper part
Ectodermal
Endodermal
1.Origin
Stratified
Columnar
2.Epithelium
Below pectineal line
Above pectineal line
3.Site
Inferior rectal artery
Superior & middle rectal
4.Arterial
supply
Systemic circulation
Portal circulation
5.Venous
drainage
Ingiunal L.N.
Internal iliac L.N.
6.Lymphatic
drainage.
Somatic pudendal nerve
(painful)
Autonomic nerves
(painless)
7.Nerve supply
Site for external haemorrhoids
Site of internal haemorrhoids
8.Heamorrhoids

77. - Arterial supply:
a) upper endodermal 1.5cm (above the pectinate line): By
sup.& middle rectal arteries
b) lower ectodermal 2.5cm (below the pectinate line): By inf.
rectal a.
- Venous drainage :
a) upper endodermal 1.5cm (above the pectinate line): By
sup. rectal vein (portal) & middle rectal vein (systemic)
b) lower ectodermal 2.5cm (below the pectinate line): By inf.
rectal v. (systemic)

78. Rectal (haemorroidal) venous plexus & piles
1. Internal rectal venous plexus:
 It lies in the submucosa of the lower part of the
rectum & anal canal
 It is formed by tributaries of the sup. rectal v.
(portal) which lie in the anal columns of
morgagni
 It communicates with the external rectal
venous plexus which is formed by middle &
inf. rectal v. (systemic)
Internal piles :
It is dilatation of inf. rectal venous plexus pushing
the mucous membrane
It occurs mainly in the veins of the 3 anal columns
situated at 3,7,11 oclock positions (as seen in the
lithotomy position)

79. External piles :
It is the rupture of dilated vein from the
external rectal venous plexus into the
peri-anal space
It occurs below the pectinate line
(therefore very painful)
•External rectal venous plexus:
•It lies outside the muscular coat of the rectum & anal
canal
•It is formed by tributaies of middle & inf. rectal veins
(systemic)
•It communicates with the internal rectal venous plexus
(porto-systemic anastmosis)