Chapter 19

When the original flat embryonic disc folds into a tube, the   becomes trapped inside forming the
epithelial lining of the  

Mesoderm cells surround the tube and form   and  

.Neural crest cells migrate into the gut and differentiate into   and   cells.

The primitive gut tube is divided into  ,  , and , each supplied by a specific artery
and  .

Foregut is from   to  

Foregut proper is  , , and 

The midgut is the rest of the   and the  

The hindgut is the   (splenic flexure) to  (above the pectinate line)

FOREGUT- gives rise to the ,  ,  , and .

MIDGUT - connects to the   which eventually becomes restricted to a   which is
incorporated into the  

The rapid growth and twisting of the   results in a
temporary herniation of the developing intestines into the yolk sac.

HINDGUT- enlargement at the end, the   becomes subdivided into two passages, one
for food waste ( ) and the other for urine ( ).

  Absence or a closure of an orifice or passage (like GI tube) in the body.

  Abnormal passage between two hollow or tubular organs or between the surface and a tubular
organ

  Abnormal narrowing or contraction of a passage of the body

  Abnormal passage between two hollow or tubular organs or between the surface and a tubular
organ

The initially hollow gut tube becomes clogged with replicating epithelial cells around Weeks  
  or reopening of the tube occurs when the overgrowth cells die a few weeks later.

Failure to reform the lumen can result in   or  . This is especially common in two regions
of the foregut, the   and  .

The fetus continually swallows the  , absorbs it into the body, and then adds fluid back into the
  in the form of  .

Increased amounts of   can be indicative of a
  (defective recanalization, twisting, compromised blood supply, tracheoesophageal
fistula, etc.) or the failure of the  to develop (usually due to anencephaly).

The foregut extends from the   to the   at the entrance of the bile duct. Buds arising from the
foregut give rise to the  ,  ,   &  .

The respiratory system develops as a bud that appears at   in the ventral wall of the endoderm lined
foregut.

Growth of a septum separates the between the foregut (future ) from the bud (future
 ), and restricts their connection to a small opening at the  .

Failure of the septum to develop properly during weeks  can result in abnormal connections and/orblockage between the trachea and esophagus (ex. tracheoesophageal fistula with esophageal atresia).

The most common defect (90%) is a   between the  . The
newborn infant and the gastric contents reflex into the lungs.

Prior to birth there is an increased volume of amniotic fluid (polyhydramnios). Amniotic fluid is normally
  and  , but in these infants the swallowed fluid is blocked
from entering the intestines.

The respiratory bud branches repeatedly, forming   and  which continue to branch into
smaller and smaller channels, ending in the  

The  ,  , and   of the gall bladder develop from buds that arise from the distal foregut (future )

Failure of the biliary ducts to develop or recanalize leads to   or  

Biliary atresia or stenosis is more likely to occur in  .   likely needed for survivial.

The pancreas develops as  and   buds, arising from oppoisite sides of the future duodenum. Rotation of the stomach and duodenum results in migration and fusion of the pancreatic buds dorsally to form the  

The  is formed when the   bud splits and encircles the dudenum, constristing the lumen, leading to duodenal stenosis or atresia

  is a common malformation (1 in 150 males, 1 in 750 females) caused by hypertrophy of the smooth muscle of the pyloric sphincter. This severe stenosis blocks the movement of food and is associated with projectile vomiting in the infant.

The midgut begins in the  (after the entrance of the bile duct) and includes  including the  and  

The midgut is connected to the yolk sac through the 
at the site of the  .

During   the midgut grows and elongates so quickly that the developing intestines, no longer able to fit
inside the abdominal cavity, herniates into the and .

The unequal accelerated growth
also causes the herniated midgut to loop on itself forming the  

During weeks  , the
gut returns or retracts to the now enlarged abdominal cavity.

During the process of herniation and retraction, the midgut undergoes a massive    
rotation.

Initially the midgut with its developing artery (superior mesenteric artery) rotates 

The final
rotation of   occurs as the elongated gut is retracted back into the abdominal cavity.

Failure of the gut to   (ex. ) is a relatively common malformation. This condition is
asymptomatic unless the intestines become twisted and the   becomes obstructed.
The infarcted region of the intestines can become  

Omphalocoele: occurs when the midgut loops fail to return to the abdominal cavity during Weeks  .
Infants are born with the intestines in an  , covered by the amniotic membrane. This condition
is often associated with   and   and  .

Gastroschisis: is caused by defective lateral folding of the embryo . The ventral abdominal wall
is weak and the viscera (intestines and neighboring organs) herniate directly into the a 
(usually to the right of the umbilicus).This is often associated with malrotation.

  is the most common malformation of the small intestine.

Meckel’s diverticulum consists of an out pocketing
from the   connected to the umbilicus by a  or an  .
It  ,  , or  . Meckel’s diverticulum is usually asymptomatic but can leadto inflammation and bleeding (if tissue secretes acid), obstruction and perforation

The hindgut gives rise to the lining of the epithelium of the  ,  , and upper part of  

The   is a dilated terminal portion of the hindgut that becomes divided into the   and   urethra, urinary bladder, lower vagina

Failure of the urorectal septum to divide the  properly can lead to abnormal openings
between the rectum, urethra, and vagina.

  or Hirschsprung’s disease is caused by defective neural crest migration of
  (Auerbach’s and Meissner’s plexus) into a portion of the colon and rectum.
This leads to defective smooth muscle contraction and constriction of this portion of the bowel.
This is the most common cause of  

The blood supply of the foregut is the  

The blood supply of the midgut is the 

The blood supply of the hindgut is the  

The parasympathetic innervation of the foregut and midgut is the  

The parasympathetic innervation of the hindgut is the pelvic  

Sympathetic of Foregut
Preganglion
Postganaglion

Sympathetic of Midgut
Preganglion
Postganaglion

Sympathetic of Hindgut
Preganglion
Postganaglion

3 Categories of things comming from ectoderm?

3 categories of things coming from meoderm?

8 things from endoderm