By Dr SaminaAnjum Slide 2 FORMATION OF PRIMITIVE GUT
Cephalocaudal folding Lateral folding Slide 3 FORMATION OF
PRIMITIVE GUT Incorporation of endoderm lined cavity in embryo Yolk
sac and allantois remain outside the body of embryo Slide 4
DIVISIONS OF PRIMITIVE GUT Foregut & hind gut are the blind
ending tubes Slide 5 Endoderm forms: The epithelial lining of gut
Parenchyma of glands Visceral mesoderm forms: Stroma of glands
Musculature of organs Peritoneum Slide 6 MESENTERIES Slide 7
FOREGUT The derivates of foregut are: The primordial pharynx and
its derivates namely, oral cavity, pharynx, tongue, tonsils,
salivary glands and upper respiratory system. The lower respiratory
system. The esophagus and stomach. The duodenum, proximal to the
opening of the bile duct. The liver, biliary apparatus (hepatic
ducts, gall bladder, bile duct and pancreas) All these foregut
derivatives, except the pharynx respiratory tract and most of the
esophagus are supplied by celiac trunk. Slide 8 DEVELOPMENT OF
ESOPHAGUS Slide 9 Initially short, but with the descent of the
heart and lungs, it lengthens rapidly. The muscular coat &
Innervation Slide 10 Abnormalities Of Esophagus Tracheoesophageal
fistula and atresia Polyhydramnios. Esophageal stenosis in the
lower third. Congenital hiatal hernia occurs when the esophagus
fails to lengthen sufficiently and the stomach is pulled up into
the esophageal hiatus through the diaphragm. Slide 11 Slide 12
Development of Stomach Fusiform dilation of the foregut in the
fourth week Dorsal & Ventral mesenteries The stomach rotates
around a longitudinal and an anteroposterior axis. Slide 13 The
stomach rotates 90 degrees clockwise around its longitudinal axis,
causing its left side to face anteriorly and its right side to face
posteriorly. Slide 14 Vagus nerves During this rotation, the
original posterior wall of the stomach grows faster than the
anterior portion, this differential growth forms the greater and
lesser curvatures. Slide 15 The cephalic and caudal ends of the
stomach originally lie in the mid line, but during further growth,
the stomach rotates around an anteroposterior axis so that the
pyloric part moves to the right and upward and cardiac portion
moves to the left and slightly downwards. Slide 16 Rotation about
the longitudinal axis pulls the dorsal mesogastrium to the left and
creates a space behind the stomach called the lesser sac. This
rotation pulls the ventral mesogastrium to the right. Slide 17 The
spleen primordium appears as a mesodermal proliferation between the
two leaves of the dorsal mesogastrium during 5 th week. The
posterior leaf of the dorsal mesogastrium and the peritoneum along
this line of fusion degenerate. Lienorenal and gastrolienal
ligaments. Slide 18 Initially pancreas grow in the dorsal
mesoduodenum, but eventually its tail extends into the dorsal
mesogastrium and is covered by peritoneum on its anterior surface
only and therefore lies in a retroperitoneal position. Secondarily
retroperitoneal organs: pancreas Slide 19 Forms by the dorsal
mesogastrium as it bulges down and forms a double layered sac
extending over transverse colon and small intestinal loops. Later
it layers fuse and forms a single sheet hanging from the greater
curvature of stomach. The posterior layer of greater omentum fuses
with the mesentery of transverse colon. GREATER OMENTUM Slide 20
Forms from the ventral mesogastrium. Its derivatives are: Falciform
ligament- free margin contains left umbilical vein; obliterates
after birth to form ligamentum Teres hepatis Lesser omentum- Right
free margin(hepatoduodenal ligament) contains portal triad and
forms the roof of the epiploic foramen FALCIFORM LIGAMENT &
LESSER OMENTUM Slide 21 Abnormalities Of Stomach Pyloric stenosis
is one of the most common abnormalities of the stomach in infants
which is believed to develop during fetal life. Occurs when
circular muscle hypertrophies. Extreme narrowing of the pyloric
lumen and the passage of food is obstructed, resulting in severe
projectile vomiting. Slide 22 DEVELOPMENT OF DUODENUM The terminal
part of the foregut and the cephalic part of the midgut form the
duodenum. The junction of the two parts is directly distal to the
origin of the liver bud. Slide 23 Due to the rotation of the
stomach, the duodenum takes on the form of a C-shaped loop and
rotates to the right. Ultimately, the duodenum swings from its
initial midline position to the right side of the abdominal cavity
Slide 24 Once developed, the hepatic and cystic ducts connect to
the duodenum by the common bile duct. The entrance of the bile duct
into the small intestine gradually shifts from an initial anterior
position to a posterior one and passes behind the duodenum. Slide
25 The duodenum and head of the pancreas press against the dorsal
body wall and the right surface of the dorsal mesoduodenum fuses
with the adjacent peritoneum and subsequently disappear. Slide 26
The dorsal mesoduodenum disappears entirely except in the region of
the pylorus of the stomach where a small portion of the duodenum
(duodenal cap) retains its mesentery and remains intraperitoneal
Slide 27 Cont During the 2 nd month, the lumen of the duodenum is
obliterated. However, the lumen is recanalized shortly thereafter.
Celiac Artery Superior mesenteric Artery Slide 28 ///LIVER &
GALL BLADDER Hepatic diverticulum appears - middle of 3 rd week as
an outgrowth of the endodermal epithelium at the distal end of
foregut Liver bud consists of rapidly proliferating liver cells
that penetrate the Septum Transversum Slide 29 Cont With further
proliferation connection between liver bud & foregut narrows to
form bile duct A small ventral outgrowth is formed by bile duct,
this outgrowth give rise to gallbladder and the cystic duct. Slide
30 Hepatic sinusoids Formed by vitelline & umbilical veins
Epithelial Liver cords Differentiate into parenchyma & form
lining of biliary ducts Mesoderm of septum transversum
Hematopoietic cells Kupffer cells Connective Tissue cells Slide 31
Mesoderm of septum transversum becomes membranous forming lesser
omentum & falciform ligament Mesoderm on the surface of the
liver differentiates into visceral peritoneum except on its cranial
surface. Here, the liver remains in contact with the rest of the
original septum transversum which form the central tendon of the
diaphragm - Bare area of liver Slide 32 6 th week Hematopoiesis 10
th week Weight of the liver - 10% of total body weight 12 th week
Bile formed by hepatic cells Bile duct formed & bile can enter
the GIT Last two months Hematopoietic function reduced Weight of
the liver only 5% of total body weight Slide 33 Development of
Pancreas In dorsal mesentery Slide 34 When duodenum rotates to
right and becomes C- shaped, the ventral pancreatic bud moves
dorsally and comes to lie immediately below and behind the dorsal
bud. Later, the parenchyma and the duct systems of the dorsal and
ventral pancreatic buds fuse. Slide 35 DERIVATIVES OF PANCREATIC
BUDS & DUCTS The ventral bud the uncinate process inferior part
of the head of the pancreas. The dorsal bud The remaining part of
the gland. The main pancreatic duct of Wirsung, together with the
bile duct enters the duodenum at the site of the major papilla. The
distal part of the dorsal pancreatic duct The entire ventral
pancreatic duct. Accessory pancreatic duct of Santorini The
proximal part of the dorsal pancreatic duct. The entrance of the
accessory duct is at the site of the minor papilla. Slide 36 Slide
37 Third month pancreatic islets (of Langerhans) develop from
parenchymal cells. Fifth month Insulin secretion Glucagon and
somatostatin-secreting cells also develop from parenchymal cells.
Splanchnic mesoderm surrounding the pancreatic buds forms the
pancreatic connective tissue. Slide 38 Annular pancreas Slide 39
MIDGUT Begins distal to the entrance of bile duct into duodenum and
terminates at the junction of right two-thirds of the transverse
colon with the distal third. Superior mesenteric artery Slide 40 In
the 5 th week midgut Is suspended from the dorsal abdominal wall by
a short mesentery. Communicates with the yolk sac through vitelline
duct until the tenth week Slide 41 Development of midgut: Is
characterized by rapid elongation of gut and its mesentery to form
the primitive intestinal loop. Midgut loop has Cephalic limb---
Distil part of duodenum, jejunum and part of ileum Caudal limb---
Lower portion of ileum, cecum, appendix, ascending colon and
proximal 2/3 rd of transverse colon Slide 42 Physiological umblical
Herniation Cause: Due to rapid growth and expansion of liver,
abdominal cavity becomes smaller Movement of intestinal loops into
EEC in the umbilical cord during 6 th week. Slide 43 The midgut
loop during herniation in the umbilical cord, rotates 90
counterclockwise (when viewed from the anterior aspect) around the
axis of the superior mesenteric artery. The cranial limb swings
down and right while the caudal limb swings up and left During
rotation, the cranial limb of the midgut elongates and forms
jejunal-ileal loops while the expanding cecum sprouts as vermiform
appendix. ROTOATION OF MID GUT Slide 44 Cont Additional rotation at
180 counterclockwise when intestinal loops return into abdomen
during 10 th week. Total rotation of midgut= 270 counterclockwise
Slide 45 RETRACTION OF HERNIATED LOOPS Causes: Regresssion of
mesonephric kidney Reduced growth of liver Expansion of abdominal
cavity During 10 th week herniated intestinal loops return to the
abdominal cavity. Proximal portion of jejunum is the first part to
reenter the abdominal cavity. Later remaining loops settle more and
more to right. Slide 46 The caecal diverticulum is the last part of
the gut to reenter the abdominal cavity, temporarily lying in the
right upper quadrant directly below the right lobe of the liver.
The caecal bud descends to the right iliac fossa, placing the
ascending colon and the hepatic flexure on the right side of the
abdominal cavity. As the appendix forms during the caecum's
descent, it frequently lies posterior to the caecum (retrocaecal)
or posterior to the colon (retrocolic ). Slide 47 Slide 48 The
derivatives of the midgut The small intestine, including most of
the duodenum The cecum, appendix, ascending colon and the right
two-thirds of the transverse colon Slide 49 FATE OF MESENTERIES The
mesentery of the primary intestinal loop becomes very twisted with
the movements of the bowel. Dorsal mesentery of small intestine
twist around the origin of superior mesenteric artery when caudal
limb of loop moves to right side of abdomen Mesenteries of
ascending and descending colon press against the peritoneum of the
posterior abdominal wall, fuse & degenerate so that these
organs become secondarily retroperitoneal. Slide 50 Cont The
mesentery of transverse mesocolon fuses with the posterior wall of
the greater omentum. The appendix, lower end of the cecum and
sigmoid colon retain their free mesenteries. Slide 51 Cont After
the mesentery of the ascending colon disappears, the fan-shaped
mesentery of the small intestine (mesentery proper) acquires a new
line of attachment running from the duodenojejunal junction in an
inferolateral direction to the ileocaecal junction Slide 52 Slide
53 ABNORMALITIES OF THE MESENTERIES Persistence of a portion of the
mesocolon gives rise to a mobile cecum. If the mesentery of the
ascending colon fails to fuse with the posterior body wall abnormal
movements of the gut occurs or volvulus of the cecum and colon
occurs. Slide 54 OMPHALOCELE fFailure of bowel to return during
physiological herniation Slide 55 GASTROSCHISIS Slide 56 Abnormal
closure of body wall around the connecting stalk, cocaine use
increases the tendency in young women Slide 57 GUT ROTATION DEFECTS
A: Abnormal rotation of the primary intestinal loop. Only 90 degree
rotation occurs, resulting in left sided colon. B: The primary
intestinal loop is rotated 90 degree clockwise (reversed rotation).
The transverse colon passes behind the duodenum & SMA. Slide 58
REVERSED ROTATION SUBHEPATIC CECUM & APPENDIX Slide 59 In 2-4%
cases vitelline duct persists forming Meckels diverticulum, 40-60cm
from ileocecal valve on the antimesenteric border of ileum Slide 60
INTESTINAL RECANALIZATION & DUPLICATION Slide 61 Slide 62 GUT
ATRESIAS & STENOSIS A: Region of bowel is lost--- 50% B: A
fibrous cord remains --- 25% C: Narrowing, with a thin diaphragm
separating the larger & smaller pieces of bowel--- 25% D:
Stenosis---5% Slide 63 Slide 64 The derivatives of the hind gut
are: The left 1/3rd of the transverse colon, the descending colon
and sigmoid colon, the rectum and the upper part of the anal canal.
The endoderm of hind gut also forms the internal lining of the
urinary bladder and most of the urethra. Slide 65 DEVELOPMENT OF
HINDGUT Slide 66 Slide 67 Slide 68 DEVELOPMENT OF ANAL CANAL B.S
Slide 69 Slide 70 HINDGUT ABNORMALITIEES A: Urorectal fistula B:
Rectovaginal fistula D: Imperforate anus Slide 71 CONGENITAL
MEGACOLON Also called HIRSCHSPRUNG DISEASE or AGANGLIONIC
MEGACOLON. Absence of parasympathetic ganglia in the bowel wall
distal to the dilated segment. Failure of neural crest cells to
migrate in the wall of colon. Rectum & sigmoid colon Male to
female ratio is 4:1 RADIOGRAPH OF COLON AFTER BARIUM ENEMA Slide 72
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