colon anatomy, anatomy of large intestine, anatomy of large bowel, histology of large intestine, large intestine, histology, colon, appendices epiploica, taenia coli, haustrautions, ilio caecal valve
5. Embryology Of Gut..,
• Blastocyst has,
• Outer cell mass (trophoblast) &
• Inner cell mass (embryoblast)
• Now coming to Embryoblast.,which divides into,
• Epiblast & Hypoblast
• And here comes the process of gastrulation, which results in
division of epiblast into.,
• Ectoderm
• Mesoderm &
• Endoderm
6. Embryology Of Gut..,
• And we know that entire gut is formed from endoderm
• Now coming to endoderm which replaces hypoblast
and covers entire yolk sac….
• Now imagine that entire surface of yolk sac is covered
with endoderm
Yaa..finally precursor for GUT tube is formed
successfully
7. Embryology Of Gut..,
• Now the yolk sac which is covered by endoderm forms head and tail fold
• After formation of head and tail fold,
Part of Yolk sac goes into embryo and forms primitive Gut
9. Embryology Of Gut..,
• For colon, midgut and hindgut are the
precursors
• Midgut initially is a blunt wide tube which
later forms a loop along the axis of vitelline
artery (later forms the Superior Mesenteric
Artery)
• After loop formation midgut is divided into
prearterial and postarterial parts
10. Embryology Of Gut.., (Midgut)
• After loop formation midgut is divided into
prearterial and postarterial parts
• Derivatives of prearterial midgut includes,
• Half of D2, D3, D4
• Jejunum
• Ileum
• Derivatives of postarterial midgut includes,
• Terminal ileum
• Caecum and Appendix
• Ascending colon
• Right 2/3rd of transverse colon
11.
12. Embryology Of Gut.., (Hindgut)
• Now coming to hindgut.. Hindgut is divided by allantoic
diverticulum into
• Pre allantoic part and
• Post allantoic part
• Derivatives of Pre allantoic HindGut
• Left 1/3rd of transverse colon,
• descending colon and sigmoid colon
• Derivatives of post allantoic Hindgut
• Forms dilated cloaca which again
divides into ventral urogenital sinus
and dorsal Rectum and Anal Canal
14. Colon Introduction.,
• Large bowel extends from ileocaecal junction to the Anus
• 1.5m long
• Large intestine = caecum + colon + rectum
• Colon is Divided into.,
1. Ascending colon
2. Transverse colon
3. Descending colon
4. Sigmoid colon
15. Anatomical features of colon
• Large intestine is wider at caecum (7.5cm) and narrower at sigmoid
colon (2.5cm)
• Greater part of colon is fixed (i.e, Reteroperitoneal) except at the
• Appendix
• Tranverse colon
• Sigmoid colon
• Longitudinal muscle plays some important roles in colon
Major role is to form 3
ribbon like bands termed
Taenia Coli
Minor role in forming a
thin layer of muscle coat
in colon
16. Anatomical features of colon (Taenia coli)
• Now let us see about TAENIA COLI.,
• They are 3 in nos
• 1 anterior (t. libera)
• 1 posteromedial (t. mesocolia)
• 1 posterolateral (t. omentalis)
• Location of these taenia is not same in the
entire large bowel…bcoz large bowel is not a
pvc pipe but flexible fire service pipe
• Taenia converge @ appendix and helps in identification of appendix
• It diverges @ distal part and continues with long. Muscles of rectum
19. Anatomical features of colon (Haustrations)
• As discussed already longitudinal
muscle layer is very thin in colon
• But circular muscle layer of colon is
very thick
• This leads to formation of
sacculations
(termed HAUSTRATIONS)
21. Anatomical features of colon (Appendices Epiploicae)
• Small bags of filled with fat (termed
APPENDICES EPIPLOICAE)
• Present all over colon ( not all over large
bowel – bcoz absent in caecum, rectum)
• It’s looking like makeup or artwork for
colon, but usually it’s too dangerous. Bcoz
it’s rich in anastomosis
• If peeled up by extra traction bleeding and
antimesenteric border ischemia occurs
22. Anatomical features of colon (Appendices Epiploicae)
• It’s looking like makeup or artwork for
colon, but usually it’s too dangerous. Bcoz
it’s rich in anastomosis
• If peeled up by extra traction bleeding and
antimesenteric border ischemia occurs
23. Anatomical features of colon (diverticulosis)
• Large bowel wall is weakened at
a. region where vessels pierce the
wall and
b. Attachment of appendices
epiploica
• So, mucosa may herniate at these areas and
will lead to diverticulosis, which may later
bcom diverticulitis, fibrosis and stricture
24. Iliocaecal valve
• Ilium opens into the posteromedial aspect
of the caecum, which is guarded by cone
shaped ileocaecal valve.
• The valve has two lips and two frenula.
Lips-
upper lip – horizontal
lower lip- concave
25. Iliocaecal valve – function mechanism.,
• The valve is actively closed by
a) The sympathetic tone and
b) Mechanically by distention of
caecum
• Function is to prevent reflux from caecum to
ileum. Thus large bowel obstruction
becomes close loop obstruction which is a
surgical emergency.
Add image of two rubber band
28. Ascending colon.,
• The ascending colon is 15cm in length.
• Extends from iliocaecal junction to the
hepatic flexure.
• Its posterior surface is fixed against the
retroperitoneum and the anterior,
medial and lateral surfaces are covered
by peritoneum (i.e., covered by
peritoneum on three sides)
29. • Anteriorly,
Coils of small intestine
Right edge of greater omentum
Anterior abdominal wall
• Posteriorly,
Back muscles (quad lumb, transverse abdominis)
Nerves (ilioinguinal, iliohypogastric and lateral cutaneous)
Right kidney
• Laterally,
Right paracolic gutter
Ascending colon relations.,
30. Right paracolic gutter.,
• It is a sulcus present laterally to the colon .
• Fluid and pus transverse along this gutter either
from appendicular region to the hepatorenal pouch
or from liver and epigastrium to the pelvis
32. TransverseColon
•Passes from right hypochondriac region
into left hypochondriac region.
•Extends from right colic flexure to left
colic flexure below the spleen.
•The left colic flexure is higher and more
posterior than the right colic flexure
,and is attached to the diaphragm by the
phrenicocolic ligament.
•Transverse mesocolon, the mesentery of transverse
colon suspends the transverse colon from the
anterior border of pancreas.
33. • Anterior relations:
1. Greater omentum
2. anterior abdominal wall
• Posterior relations:
1. Descending part of the duodenum
2. Head of the pancreas
3. Coils of jejunum and ileum
• superior relations
1. Liver
2. Gall-bladder
3. Greater curvature of stomach
4. Lower end of spleen
• Inferior relations–
1. Small intestine
Relations of transversecolon:
34. DescendingColon
•It is 10inch in length
•Runs vertically down from the splenic flexure up to
iliac crest and then inclines medially iliacus and psoas
major and then continues with sigmoid colon
•Descending colon is narrower than the ascending colon
35. Relations of descendingcolon:
• Anterior relations:
-Coils of small intestine
-Greater omentum
-Anterior abdominal wall
• Posterior relations:
-Lateral border of left kidney
-Origin of transversus abdominis muscle
-Quadratus lumborum muscle
-Iliac crest
-Iliacus muscle
-Left psoas muscle
-Iliohypogastric and Ilioginuinal nerves
-Lateral cutaneous nerve of thigh
-Femoral nerve
37. Relations of sigmoidcolon:
• Anterior relations:
-Urinary bladder (in males)
-Posterior surface of uterus and upper part of vagina (in females)
• Posterior relations:
-Sacrum
-external iliac vessels
-left piriformis
-left sacral plexus of nerves
39. Both rt. & lt. colic artery has ascending and descending branches
40. Arterial supply of colon
• From Marginal artery terminal branch arises
• Divides into vasa longa and vasa brevia
• Both enter along mesocolic border (mesocolic
taenia)
• Blood supply will be less on the side between
two amesocolic taenia…..so, here the
longitudinal incisions can be given
41. Venous supply of colon
• Venous supply corresponds to the arterial supply
42. Lymphatic drainage of colon
• Lymph of colon is being drained via different
level of nodes.,
1. Epicolic – lying on wall of gut
2. Paracolic – on medial side
3. Intermediate – on main branches
4. Terminal nodes – on IM, SM Vessles
• If Ca spread occurs till intermediate or terminal
nodes, for removing nodes corresponding
arteries have to be ligated…so, the
corresponding bowel has to be resected
eventhough the bowel loop doesn’t contain
carcinoma
43. Nerve supply of colon
• Lymph of colon is being drained via different
Gut level
Corresponding
bowel loops PNS SNS PAIN LEVEL
ROUTE OF
NERVE
SUPPLY
CLINICAL
IMPORTANCE
MIDGUT JUNCN. OF
D1/D2 TO RT.
2/3RD
TRANVERSE
COLON
VAGUS
(CN 10)
(T11-L1)
COELIAC
GANGLION
AND
SUPERIOR
MESENTERIC
GANGLION
AROUND
UMBLICUS
(T11-L1)
DERMATOME
VIA SUPERIOR
MESENTERIC
PLEXUS
SO, IN ANY
MIDGUT
PROBLEM
PAIN
AROUND
UMBLICUS
HINDGUT LEFT 1/3RD
TRANSVERSE
COLON TO
ANAL CANAL
NERVI
ERIGENTIS
(S2, S3, S4)
(L1-L2)
LUMBAR
SYMPATHETIC
CHAIN
AROUND
PUBIC
REGION
VIA INFERIOR
MESENTERIC
PLEXUS AND
SUPERIOR
HYPOGASTRIC
PLEXUS
SO, IN ANY
HINDGUT
PROBLEM
PAIN
AROUND
PUBIC
REGION
45. Histology of Gut.,
Histology of gut consists of,
1. Mucosa
• Epithelium
• Lamina propria
• Muscularis mucosa
2. Submucosa
3. Muscularis externa
4. Adventitia / Serosa
46. Histology of colon…, (Mucosa)
• Mucosa has,
a) Epithelium – Columnar – absorbs water and ions
b) In lamina propria – has 2 glands
1. Goblet cells – secrete mucous for
lubrication
2. Entero endocrine cells – secrete various
harmones for regulation of secretion and
peristalsis
c) muscularis mucosa – has smooth muscles which
facilitates secretion
d) No villi, but crypts of lieberkuhn present
47. Histology of colon…, (Sub Mucosa)
• SubMucosa has,
• Dense connective tissue
• Blood vessels and
• Sub mucosal (Meissner’s Plexus) – regulates
submucosal glands and muscularis mucosa
• Does not has any glands (but in duodenum
submucosa has brunners gland, which secrete
mucin and alkalizes acid)
48. Histology of colon…, (Muscularis Externa)
• Muscularis externa has,
a) Inner circular and
b) Myenteric plexus (auerbach)
c) Outer Longitudinal layers, which has 2 roles
Major role is to form
3 ribbon like bands
termed Taenia Coli
Minor role in forming
a thin layer of muscle
coat in colon
49. Histology of colon…, (Serosa / adventitia)
• Serosa –
• has serous membrane
• Made of squamous epithelium
• Helps in lubrication by secreting serous fluid
• Present in the bowel loops covered by peritoneum
• So, in large intestine present in transverse and sigmoid colon
• Adventitia –
• Attaches organ to the surrounding tissues
• It covers retro peritoneal part of large intestine (i.e., except trans. And sigmoid colon)
51. Enteric plexus
• Enteric plexus are of two types,
• Submucosal (meissners) and
• Myenteric (Auerbach)
• Myenteric plexus is responsible for peristaltic contraction and relaxation
• These plexus are derived from neural crest cells
