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Digestive System

MULTIPLE CHOICE

Directions: Each group of questions below consists of a numbered list of descriptive words or phrases accompanied by a diagram with certain parts indicated by letters or by a list of lettered headings. For each numbered word or phrase, select the lettered part or heading that matches it correctly and then insert the letter in the space to the right of the appropriate number. Sometimes more than one numbered word or phrase may be correctly matched to the same lettered part or heading.

        1.  

________ Primarily involved in extrahepatic biliary atresia

a.
A
b.
B
c.
C
d.
D
e.
E

ANS:   B

In extrahepatic biliary atresia, parts of the hepatic ducts and bile duct are not canalized. Parts of the bile ducts are blocked (atresia); other parts may have narrow lumina (stenosis). These severe anomalies are not common. The extrahepatic system of bile ducts develops as solid cords that typically soon become canalized. When this fails to occur, atresia results. If the lumen forms but is small, stenosis is present. Congenital atresia of the bile ducts may be caused by noxious agents acting during the development of the bile duct system. There is little evidence that this anomaly is hereditary; it rarely occurs in siblings (brothers or sisters). Jaundice gradually increases after birth; the stools are clay-colored, and the urine is dark brown.

        2.  

________ Forms the major part of the pancreas

a.
A
b.
B
c.
C
d.
D
e.
E

ANS:   D

The dorsal pancreatic bud forms the major part of the pancreas; the inferior part of the head of the pancreas and the uncinate process are derived from the ventral pancreatic bud. The main pancreatic duct forms by fusion of the ducts of both pancreatic buds.

        3.  

________ Penetrates the septum transversum

a.
A
b.
B
c.
C
d.
D
e.
E

ANS:   C

The liver arises as a bud from the caudal part of the foregut late in the third week. This hepatic diverticulum extends ventrally and cranially into the mesenchyme of the septum transversum between the pericardial cavity and the omphaloenteric duct. Subsequently, the liver lies between the layers of the ventral mesentery. These layers become the peritoneal covering of the liver and the ligaments associated with the liver.

        4.  

________ Partly derived from the midgut

a.
A
b.
B
c.
C
d.
D
e.
E

ANS:   E

The epithelium and glands of the duodenum distal to the point of entrance of the bile duct are derived from the midgut. Other layers of the mucous membrane and the wall of the duodenum are derived from mesenchyme adjacent to the endodermal midgut. The epithelium and glands of the duodenum cranial to the entrance of this duct are derived from the foregut.

        5.  

________ Forms the inferior part of the head of the pancreas

a.
A
b.
B
c.
C
d.
D
e.
E

ANS:   A

The ventral pancreatic bud forms the inferior part of the head of the pancreas, including the uncinate process. Most of the pancreas develops from the dorsal bud. Sometimes the two pancreatic buds form a ring of pancreatic tissue around the duodenum (anular pancreas), which may cause obstruction of the duodenum.

        6.   ________ Derived from the midgut loop

a.
Spleen
b.
Omphaloenteric duct (yolk stalk)
c.
Gallbladder
d.
Appendix
e.
Celiac trunk

ANS:   D

The appendix is derived from the cecal diverticulum, an outpouching from the antimesenteric side of the midgut loop. The distal end of the cecum does not grow rapidly; thus, the appendix forms. At birth, the appendix is relatively longer than in the adult and is continuous with the apex of the cecum.

        7.   ________ Continuous with the apex of the midgut loop

a.
Spleen
b.
Omphaloenteric duct (yolk stalk)
c.
Gallbladder
d.
Appendix
e.
Celiac trunk

ANS:   B

The omphaloenteric duct is attached to the apex of the midgut loop. The other end of this stalk is attached to the remnant of the umbilical vesicle (yolk sac), located near the placenta. The yolk stalk normally degenerates at the end of the embryonic period, but in about 2% of people, the proximal part of it persists as an ileal (Meckel) diverticulum.

        8.   ________ Organ derived solely from mesenchyme

a.
Spleen
b.
Omphaloenteric duct (yolk stalk)
c.
Gallbladder
d.
Appendix
e.
Celiac trunk

ANS:   A

The spleen is derived from a condensation of mesenchymal cells between the layers of the dorsal mesogastrium. The splenic artery is a branch of the foregut (celiac) artery; this explains why it gives off pancreatic branches, short gastric arteries, and the left gastro-omental artery. Recall that the stomach and pancreas are foregut derivatives.

        9.   ________ Derived from foregut

a.
Spleen
b.
Omphaloenteric duct (yolk stalk)
c.
Gallbladder
d.
Appendix
e.
Celiac trunk

ANS:   C

The gallbladder is derived from the foregut. The hepatic diverticulum from the foregut divides into two parts; the larger cranial part gives rise to the liver, and the caudal part gives rise to the gallbladder.

      10.   ________ Supplies foregut derivatives

a.
Spleen
b.
Omphaloenteric duct (yolk stalk)
c.
Gallbladder
d.
Appendix
e.
Celiac trunk

ANS:   E

The celiac trunk (artery) carries blood from the aorta to the foregut derivatives (inferior end of the esophagus, stomach, liver, part of the duodenum, gallbladder, and part of the pancreas). The celiac artery also supplies the spleen, which develops from mesenchyme in the dorsal mesentery of the stomach.

      11.  

________ Derived from the foregut and midgut

a.
A
b.
B
c.
C
d.
D
e.
E

ANS:   B

The duodenum is derived from the caudal part of the foregut and the cranial part of the midgut. The junction of the foregut and midgut is at the apex of the embryonic duodenal loop. The junction is indicated in the adult by the point of entrance of the bile duct. Because of its dual origin, the duodenum is supplied by both the foregut (celiac) and midgut (superior mesenteric) arteries.

      12.  

________ Hepatoduodenal ligament

a.
A
b.
B
c.
C
d.
D
e.
E

ANS:   A

The ventral mesentery between the cranial or superior part of the duodenum and the liver persists and gives rise to the hepatoduodenal ligament. The remainder of the ventral mesentery of the foregut gives rise to the hepatogastric ligament, peritoneal covering of the liver, falciform ligament, and coronary and triangular ligaments of the liver. The superior part of the duodenum is the only part of the intestines that has a ventral mesentery.

      13.  

________ Arises as a diverticulum of the foregut

a.
A
b.
B
c.
C
d.
D
e.
E

ANS:   D

The liver arises as a diverticulum from the caudal end of the foregut. The proliferating endodermal cells give rise to interlacing cords of cells, which become the liver parenchyma. The fibrous and hematopoietic tissue are derived from splanchnic mesenchyme.

      14.  

________ Its free border contains the umbilical vein

a.
A
b.
B
c.
C
d.
D
e.
E

ANS:   E

The umbilical vein passes in the inferior free border of the falciform ligament on its way to the liver with well-oxygenated blood from the placenta. Within the liver, the umbilical vein is broken up by the proliferating hepatic cords. The hepatic sinusoids are derived from remnants of the umbilical and vitelline veins. The adult derivative of the extrahepatic part of the umbilical vein is the round ligament (L. ligamentum teres) of the liver.

      15.  

________ Embryonic site of hematopoiesis

a.
A
b.
B
c.
C
d.
D
e.
E

ANS:   D

The liver is an important site of blood formation in the embryo and early fetus. Hematopoiesis begins in the liver during the sixth week; before this, blood formation occurs in the extraembryonic mesenchyme of the umbilical vesicle and allantois. Blood is later formed in the spleen, bone marrow, and lymph nodes.

      16.   ________ Faulty partitioning of the foregut

a.
Pyloric stenosis
b.
Anorectal agenesis
c.
Esophageal atresia
d.
Omphalocele
e.
Polyhydramnios

ANS:   C

Esophageal atresia may occur as an isolated anomaly resulting from failure of canalization of the esophagus, but most often, it is associated with tracheoesophageal fistula. In more than 85% of cases of this type of fistula, the esophagus ends blindly. The fistula between the inferior end of the esophagus and the trachea results from faulty or incomplete partitioning of the foregut into the esophagus and the laryngotracheal tube. Incomplete formation of the tracheoesophageal septum at any level may give rise to a fistula.

      17.   ________ Herniation of the intestines

a.
Pyloric stenosis
b.
Anorectal agenesis
c.
Esophageal atresia
d.
Omphalocele
e.
Polyhydramnios

ANS:   D

Omphalocele is a congenital protrusion or herniation of the intestines through a large defect in the anterior abdominal wall at the umbilicus. This anomaly is believed to result from failure of the intestines to return from the umbilical cord during the tenth week. The hernial mass is covered by a thin, transparent membrane composed of peritoneum internally and amnion externally (from the amniotic covering of the umbilical cord).

      18.   ________ Causes projectile vomiting

a.
Pyloric stenosis
b.
Anorectal agenesis
c.
Esophageal atresia
d.
Omphalocele
e.
Polyhydramnios

ANS:   A

Pyloric stenosis (narrowing of the distal opening of the stomach) results from hypertrophy of the muscle fibers of the pylorus, principally the circular musculature. The typical clinical picture is an infant who appears normal at birth, but within a week or more, there is a gradual onset of vomiting that progresses to a projectile type.

      19.   ________ Duodenal obstruction

a.
Pyloric stenosis
b.
Anorectal agenesis
c.
Esophageal atresia
d.
Omphalocele
e.
Polyhydramnios

ANS:   E

High intestinal obstruction (e.g., duodenal atresia) frequently is an accompaniment of polyhydramnios. Excessive amniotic fluid is also associated with meroanencephaly (partial absence of the brain) and esophageal atresia. With meroanencephaly, there appears to be difficulty in swallowing. In esophageal and duodenal atresia, amniotic fluid accumulates because it is unable to pass to the intestines for absorption.

      20.   ________ Faulty partitioning of the cloaca

a.
Pyloric stenosis
b.
Anorectal agenesis
c.
Esophageal atresia
d.
Omphalocele
e.
Polyhydramnios

ANS:   B

Fistulas are associated with most cases of anorectal agenesis. The fistulas usually are rectourethral in males and rectovaginal in females. Anorectal agenesis with a fistula results from faulty or incomplete partitioning of the cloaca by the urorectal septum into the rectum and urogenital sinus.

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Pharyngeal Apparatus

Urogenital System