Body Cavities, Mesenteries, and Diaphragm

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.  

________ Derived from intraembryonic coelom

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

ANS:   E

The peritoneal cavity is derived from the caudal extension of the horseshoe-shaped intraembryonic coelom that forms early in the fourth week of development. In the illustration, the foregut (primordial stomach) is suspended in the peritoneal cavity by the dorsal mesentery (dorsal mesogastrium) and the ventral mesentery (hepatogastric ligament).

        2.  

________ Ventral mesentery of the stomach

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

ANS:   A

The ventral mesentery of the stomach develops from the septum transversum and extends from this septum to the ventral aspect of the caudal part of the foregut. This part of the foregut gives rise to the stomach and the superior part of the duodenum. After the liver develops, the ventral mesentery attaches the stomach to the liver (hepatogastric ligament) and the first part of the duodenum to the liver (hepatoduodenal ligament).

        3.  

________ Caudal part of the foregut

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

ANS:   B

The endoderm of the caudal part of the foregut gives rise to the epithelium and glands of the inferior end of the esophagus, the stomach, and the superior part of the duodenum. The muscular and fibrous elements of these structures are derived from the surrounding splanchnic mesoderm. The superior part of the foregut gives rise to the pharynx and its derivatives, the lower respiratory tract, and the superior part of the esophagus.

        4.  

________ Dorsal mesogastrium

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

ANS:   D

The dorsal mesentery (dorsal mesogastrium) suspends the stomach in the peritoneal cavity. The spleen subsequently develops between the two layers of the dorsal mesogastrium. Later, as the result of positional changes and growth, the dorsal mesogastrium hangs over the transverse colon and small intestine; this part of the dorsal mesentery is the greater omentum.

        5.   ________ Large esophageal opening

A.
Costodiaphragmatic recess
B.
Cervical myotomes
C.
Congenital hiatal hernia
D.
Pleuroperitoneal membrane
E.
Pericardioperitoneal canal

ANS:   C

If the embryonic esophageal hiatus or opening in the diaphragm is excessively large, abdominal viscera may herniate through it into the thorax, producing a congenital diaphragmatic hernia (CDH). Another uncommon type of CDH, the sliding hiatal hernia, is believed to be caused by a short esophagus. Because of this anomaly, the superior part of the stomach remains in the thorax and the stomach is constricted where it passes through the esophageal opening.

        6.   ________ Posterolateral diaphragmatic defect

A.
Costodiaphragmatic recess
B.
Cervical myotomes
C.
Congenital hiatal hernia
D.
Pleuroperitoneal membrane
E.
Pericardioperitoneal canal

ANS:   D

If the pleuroperitoneal membrane fails to develop or to fuse with other parts of the diaphragm, a posterolateral defect develops, usually on the left side. Associated with this defect is herniation of abdominal viscera into the thorax and compression of the lungs. This type of CDH often results in a medical-surgical emergency because of difficulty in fetal breathing.

        7.   ________ Diaphragmatic muscles

A.
Costodiaphragmatic recess
B.
Cervical myotomes
C.
Congenital hiatal hernia
D.
Pleuroperitoneal membrane
E.
Pericardioperitoneal canal

ANS:   B

The diaphragmatic muscles are mainly derived from myoblasts that migrate from the myotome regions of the cervical somites. Other myoblasts are derived from the myotome regions of the thoracic somites, and some myoblasts originate in the body wall tissues.

        8.   ________ Connects the pericardial and peritoneal cavities

A.
Costodiaphragmatic recess
B.
Cervical myotomes
C.
Congenital hiatal hernia
D.
Pleuroperitoneal membrane
E.
Pericardioperitoneal canal

ANS:   E

The pericardioperitoneal canals become the adult pleural cavities. Membranes develop at the cranial and caudal ends of these canals that separate the pleural cavities from the pericardial cavity and the peritoneal cavity, respectively. The developing lungs invaginate the medial walls of the pericardioperitoneal cavities. The inner (visceral) and outer (parietal) walls of these canals eventually come close together as the layers of pleura.

        9.   ________ Herniation of the abdominal viscera

A.
Costodiaphragmatic recess
B.
Cervical myotomes
C.
Congenital hiatal hernia
D.
Pleuroperitoneal membrane
E.
Pericardioperitoneal canal

ANS:   D

Herniation of abdominal viscera into the thorax occurs through a posterolateral defect in the diaphragm where there is failure of development or fusion of the pleuroperitoneal membrane with other parts of the diaphragm, usually on the left side. Because of the presence of abdominal viscera in the thorax, the lungs often are compressed and may be hypoplastic (incompletely developed).

      10.   ________ Derived from the third to fifth cervical spinal cord segments

A.
Esophageal mesentery
B.
Pleuropericardial membrane
C.
Phrenic nerves
D.
Crura of the diaphragm
E.
Embryonic mediastinum

ANS:   C

The phrenic nerves are derived from the third, fourth, and fifth cervical segments of the spinal cord. These nerves accompany the myoblasts that grow into the developing diaphragm from the myotome regions of the cervical somites. The diaphragm descends as elongation of the neck, descent of the heart, and expansion of the pericardial and pleural cavities occur. The descent of the diaphragm, after it receives its main nerve supply, explains the rather unusual course of the phrenic nerves.

      11.   ________ Muscular origins of the diaphragm

A.
Esophageal mesentery
B.
Pleuropericardial membrane
C.
Phrenic nerves
D.
Crura of the diaphragm
E.
Embryonic mediastinum

ANS:   D

The crura of the diaphragm (muscular origins of diaphragm from superior lumbar vertebrae) develop as muscle fibers in the esophageal mesentery.

      12.   ________ Forms median part of the diaphragm

A.
Esophageal mesentery
B.
Pleuropericardial membrane
C.
Phrenic nerves
D.
Crura of the diaphragm
E.
Embryonic mediastinum

ANS:   A

The dorsal mesentery of the esophagus (mesoesophagus) forms the median part of the diaphragm. The pleuroperitoneal membranes fuse with the esophageal mesentery and septum transversum during the sixth week, forming a partition between the thoracic and abdominal cavities. Completion of the diaphragm occurs during the 9th to 12th weeks as body wall tissue is added to it peripherally.

      13.  

________ Future pleural cavity

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

ANS:   B

The pericardioperitoneal canals are the future pleural cavities. As the lungs develop, they invaginate (push into) the medial walls of these canals, like fists pushed into the sides of almost empty balloons. These invaginations are so complete that the space between the two walls of the canals (future layers of pleura) is reduced to a narrow gap.

      14.  

________ Primordium of the esophagus

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

ANS:   E

The foregut gives rise to the epithelium and glands of the esophagus and stomach. Other regions of the foregut give rise to the pharynx and its derivatives, the lower respiratory tract, the duodenum as far as the bile duct, the liver, the pancreas, and the biliary apparatus.

      15.  

________ Gives rise to central tendon

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

ANS:   A

The septum transversum, a thick mass of mesenchyme, gives rise to the central tendon of the diaphragm. It is the first component of the diaphragm that is recognizable (end of third week). It forms the caudal limit of the pericardial cavity after folding of the embryo and separates it from the future peritoneal cavity. During the fourth week, groups of myoblasts (muscle-forming cells) from the cervical somites (three to five) migrate into the cranial part of the septum transversum, carrying their phrenic nerve fibers with them.

      16.  

________ Pleuroperitoneal membrane

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

ANS:   D

The pleuroperitoneal membranes, produced as the lungs and pleural cavities expand by invading the body walls, form caudal partitions in the pericardioperitoneal canals. These membranes gradually grow medially and fuse during the sixth week with the dorsal mesentery of the esophagus and the septum transversum to form the diaphragm. Failure of one of these membranes to form results in a CDH through which the abdominal viscera can herniate. The defect usually appears in the region of the left kidney.

      17.  

________ Derived from the foregut

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

ANS:   C

The epithelium and glands of the esophagus are derived from the foregut. The muscular and fibrous elements are derived from the surrounding splanchnic mesenchyme. The foregut also gives rise to the epithelium and glands of the lower respiratory tract. Faulty partitioning of the foregut into the esophagus and trachea during the fourth and fifth weeks results in a tracheoesophageal fistula.

      18.  

________ Esophageal mesentery

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

ANS:   E

The esophageal mesentery (dorsal mesentery of esophagus) is one of the components of the primordial diaphragm. The other components are the septum transversum and pleuroperitoneal membranes. Later, a fourth component, the body wall, contributes to peripheral regions of the diaphragm. The esophageal mesentery constitutes the median portion of the diaphragm. The crura of the diaphragm develop from muscle fibers that form in the dorsal mesentery of the esophagus.

      19.  

________ Future pleural cavity

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

ANS:   A

The pericardioperitoneal canals become the pleural cavities. The bronchial buds grow laterally during the fifth week and evaginate the medial walls of the canals. The inner walls of the canals become the visceral pleura and the outer walls become the parietal pleura.

      20.  

________ Gives rise to the central tendon of the diaphragm

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

ANS:   B

The septum transversum gives rise to the central tendon of the diaphragm. Although initially located opposite the cervical region of the spinal cord, the septum transversum is invaded by myoblasts from the third, fourth, and fifth myotome regions of the cervical somites. Later, the diaphragm descends until its dorsal part lies at the level of the first lumbar vertebra. Thus, the seemingly curious origin and course of the phrenic nerves result from the developmental origin of the septum transversum.