1. THE FOREGUT
• For descriptive purposes the
primordial gut is divided into four
parts:
1.Pharyngeal gut
2.Foregut
3.Midgut
4.Hindgut.

2. • Lateral view of developing 26 day old embryo showing
different parts of primitive gut.
• Foregut begins caudal to respiratory diverticulum and
extends up to liver diverticulum.

4. •The derivatives of the
foregut are:
–Esophagus
–Stomach
–Duodenum, proximal to the opening of the
bile duct
–Liver, biliary apparatus (hepatic ducts,
gallbladder, and bile duct)
–Pancreas

5. • Foregut ends at the level of liver
diverticulum.
• Midgut begins caudal to foregut.
• This junction where the foregut ends and
midgut begins is called anterior intestinal
portal.
• The midgut extends from anterior
intestinal portal to posterior intestinal
portal.

6. Let us first understand intestinal portal

7. Derivatives of midgut
• Small intestine, including most of the
duodenum
• Cecum, vermiform appendix, ascending
colon, and right half to two-third of
transverse colon.
• All these derivatives are supplied by
superior mesenteric artery, the artery of
the midgut. Similarly derivatives of midgut
are drained by superior mesenteric vein.

8. • The small intestine is the longest section
of the digestive tube
• It is about seven meters long
• It is a tunnel from the pylorus to the large
intestine
• It is divided into three segments:
duodenum, jejunum and ileum

9. • Duodenum is the first part of small
intestine. So it is the widest part of small
intestine.
• It is C – shaped structure.
• It is only 25 cm long.
• t lacks mesentery. It is retroperitoneal and
fixed to posterior abdominal wall.

10. • Duodenum becomes jejunum opposite the
second lumbar vertebra.
• At duodenojejunal junction it turns abruptly
anteriorly forming duodenojejunal flexure.

11. Duodenum receives secretions
from
• Liver via common bile duct
• pancreas through pancreatic
duct

12. Duodenum is divided into four portions:
• First or Superior part
• Second or Descending part
• Third or Horizontal part
• Fourth or Ascending part

14. The first (superior) part
• begins as a continuation of the duodenal end
of the pylorus.
• From here it passes laterally (right),
superiorly and posteriorly, for approximately
5 cm, before making a sharp curve inferiorly
into the superior duodenal flexure (the end of
the superior part).
• It is the only intraperitoneal portion of the
duodenum

16. The second or descending part
• The second (descending) part of the
duodenum begins at the superior
duodenal flexure.
• It passes inferiorly to the lower border of
vertebral body L3, before making a sharp
turn medially into the inferior duodenal
flexure (the end of the descending part).

18. Inferior or horizontal part
• The third (inferior/horizontal) part of the
duodenum begins at the inferior duodenal
flexure and passes transversely to the left,
crossing the right ureter, right
testicular/ovarian vessels, inferior vena
cava, abdominal aorta and the vertebral
column

19. Ascending part
• The fourth (ascending) part passes
superiorly, either anterior to, or to the left
of, the aorta, until it reaches the inferior
border of the body of the pancreas.
• Then, it curves anteriorly and terminates at
the duodenojejunal flexure where it joins
the jejunum.

20. • The duodenum
• Its fourth part lies anterior to the IVC
• It is shortest, narrowest and most sessile
part of small intestine
• It is 30 cm long
• It encircles the umbilicus
• It has superior and inferior duodenal
flexures

21. • Its fourth part lies anterior to and left of the
abdominal aorta
• It is shortest, widest and most sessile part
of small intestine
• It is 20-25 cm long
• It is situated entirely above the level of
umbilicus
• It has superior and inferior duodenal
flexures

22. • The wall of small intestine consists of four
classical coats
• Mucosa
• Submucosa
• Muscularis
• Serosa

24. • Identification points
• Lining epithelium is simple columnar with goblet
cells
• Intestinal villi are numerous
They are tall and broad
They are mucosal projections with a
core of lamina propria
They are covered by simple columnar
epithelium with goblet cells

25. • The intestinal glands or crypts of
Lieberkühn are lined by simple columnar
epithelium containing goblet cells and
paneth cells
• Paneth cells are present at the bases of
the glands and they are most numerous in
duodenum

26. • Plicae circulares or circular folds or
Kerckring’s valves are present
• They are submucosal horizontal or
transverse semilunar folds or valves,
containing mucosa and submucosa
• Brunner’s glands are present in
submucosa and mucosa. They are
compound tubular mucous secreting
glands

31. Development
of the
Duodenum

32. • Duodenum begins to develop in the early part
of fourth week.
• It (epithelium) develops from caudal part of
foregut and cranial part of midgut.
• All the other layers of duodenum are derived
from surrounding splanchnic mesenchyme.
• The junction of the two parts of the duodenum
is just distal to the origin of the liver diverticulum
and in adult it is common bile duct.
• At this junction the ventral and dorsal
pancreatic buds are also developing.

33. • Duodenum grows rapidly, forming a C-shaped loop
ventrally.

34. • As stomach rotates 90 degrees in clockwise
direction around its longitudinal axis to the left,
duodenal loop rotates to the right.
• This rotation together with rapid growth of
pancreas swings duodenum from its initial
midline position to the right.

35. • Duodenum and pancreas are pressed against
posterior abdominal wall. The right leaf of
dorsal meso-duodenum fuses with parietal
layer of peritoneum. The two layers
subsequently disappear. Duodenum and
pancreas become retroperitoneal structures.
• Mesoduodenum disappears entirely except in
the region of pylorus of stomach, where a small
portion of duodenum (duodenal cap) retains its
mesentery and remains intraperitoneal.

36. • Transverse sections 5th and 7th week embryo

37. • During the fifth and sixth weeks, the lumen of
duodenum becomes progressively smaller and
is temporarily obliterated because of the
proliferation of its epithelial cells. Normally
vacuolization occurs because of degeneration
of the epithelial cells. As a result, the duodenum
normally becomes re-canalized by the end of
the embryonic period. But sometimes the
occlusion persists leading to duodenal stenosis.

38. • Because duodenum is developing from
foregut and midgut, it is supplied by
branches of celiac and superior
mesenteric arteries.
1.right gastric - a branch of hepatic artery - a
branch of celiac trunk.
2.supra-duodenal – arises from either gastro-
duodenal, hepatic artery, or right gastric
artery. Gastro-duodenal and right gastric are
branches of hepatic artery. Hepatic artery is
branch of celiac trunk.

39. 1. right gastro-epiploic - a branch of
hepatic artery - a branch of celiac
trunk.
2. superior pancreatico-duodenal - a
branch of hepatic artery - a branch of
celiac trunk.
3. inferior pancreatico-duodenal – a
branch of superior mesenteric artery.