Chapter 7: The Gut Tube and the Body Cavities

Question 1

A TUBE ON TOP OF A TUBE

During the ______ and ______ weeks, the top layer (______) of the trilaminar embryonic disc forms the ______ that rolls up into a tube to form the ______ and ______ by the process called ______.

Answer 1

third, fourth, ectoderm, neural plate, brain, spinal cord, neurulation

Question 2

A TUBE ON TOP OF A TUBE

Almost simultaneously, the ventral layer
(______) rolls down to form the ______, such that the embryo consists of a tube on top of a ______: the neural tube ______ and the gut tube ______.

Answer 2

endoderm, gut tube, tube, dorsally, ventrally

Question 3

A TUBE ON TOP OF A TUBE

The middle layer (______) holds the ______ tubes together and the ______ component of this mesoderm layer also splits into ______ (______) and ______ (______) layers.

Answer 3

mesoderm, two, lateral plate, visceral, splanchnic, parietal, somatic

Question 4

A TUBE ON TOP OF A TUBE

The ______ layer rolls ventrally and is intimately connected to the gut tube; the ______ layer, together with the overlying ectoderm, forms the ______ (one on each side of the embryo), which move ______ and meet in the ______ to close the ______.

Answer 4

visceral, parietal, lateral body wall folds, ventrally, midline, ventral body wall

Question 5

A TUBE ON TOP OF A TUBE

The space between visceral and parietal layers of lateral plate mesoderm is the ______, which at this early stage is a ______ cavity, because it has not yet been subdivided into the ______, ______, and ______ regions.

Answer 5

primitive body cavity, continuous, pericardial, pleural, abdominopelvic

Question 6

FORMATION OF THE BODY CAVITY

At the end of the ______ week, ______ differentiates into ______, which forms ______ and ______ that play a major role in forming the skull and vertebrae; ______, which contributes to the urogenital system; and ______, which is involved in forming the body cavity.

Answer 6

third, intraembryonic mesoderm, paraxial mesoderm, somitomeres, somites, intermediate mesoderm, lateral plate mesoderm

Question 7

FORMATION OF THE BODY CAVITY

Soon after it forms as a solid mesodermal layer, ______ appear in the ______ that coalesce to split the solid layer into two: (1) the ______ (______) layer adjacent to the surface ectoderm and continuous with the extraembryonic parietal mesoderm layer over the ______; (2) the ______ (______) layer adjacent to endoderm forming the gut tube and continuous with the visceral layer of extraembryonic mesoderm covering the ______.

Answer 7

clefts, lateral plate mesoderm, parietal, somatic, amnion, Visceral, splanchnic, yolk sac

Question 8

FORMATION OF THE BODY CAVITY

Together, the parietal (somatic) layer of lateral plate mesoderm and overlying ______ are called the ______.

Answer 8

ectoderm, somatopleure

Question 9

FORMATION OF THE BODY CAVITY

Together, the visceral (splanchnic) layer of lateral plate mesoderm and underlying ______ are called the ______.

Answer 9

endoderm, splanchnopleure

Question 10

FORMATION OF THE BODY CAVITY

The space created between the two layers of lateral plate mesoderm constitutes the ______.

Answer 10

primitive body cavity

Question 11

FORMATION OF THE BODY CAVITY

During the ______ week, the sides of the embryo begin to grow ventrally forming two ______. These folds consist of the ______ layer of lateral plate mesoderm, overlying ______, and cells from adjacent ______ that migrate into the mesoderm layer across the ______. As these folds progress, the ______ layer also folds ventrally and closes to form the ______.

Answer 11

fourth, lateral body wall folds, parietal, ectoderm, somites, lateral somitic frontier, endoderm, gut tube

Question 12

FORMATION OF THE BODY CAVITY

By the end of the ______ week, the lateral body wall folds meet in the ______ and fuse to close the ______. This closure is aided by growth of the ______ and ______ regions (folds) that cause the embryo to curve into the ______.

Answer 12

fourth, midline, ventral body wall, head, tail, fetal position

Question 13

FORMATION OF THE BODY CAVITY

Closure of the ventral body wall is complete except in the region of the ______ (future ______).

Answer 13

connecting stalk, umbilical cord

Question 14

FORMATION OF THE BODY CAVITY

Similarly, closure of the gut tube is complete except for a connection from the midgut region to the yolk sac called the ______ (______) duct. This duct is incorporated into the ______, becomes very ______, and ______ with the yolk sac between the ______ and ______ months of ______.

Answer 14

Vitelline, yolk sac, umbilical cord, narrow, degenerates, second, third, gestation

Question 15

FORMATION OF THE BODY CAVITY

Note that throughout the process of body cavity and gut tube development, the ______ and ______ layers of lateral plate mesoderm are ______ with each other at the junction of the ______ with the ______.

Answer 15

parietal, visceral, continuous, gut tube, posterior body wall

Question 16

SEROUS MEMBRANES

Some cells of the parietal layer of lateral plate mesoderm lining the body wall of the primitive embryonic cavity become ______ and form the ______ layer of the ______ lining the outside of the ______, ______, and ______ cavities.

Answer 16

mesothelial, parietal, serous membranes, peritoneal, pleural, pericardial

Question 17

SEROUS MEMBRANES

In a similar manner, some cells of the visceral layer of lateral plate mesoderm form the ______ layer of the ______ covering the ______ organs, ______, and ______.

Answer 17

Visceral, serous membranes, abdominal, lungs, heart

Question 18

SEROUS MEMBRANES

Visceral and parietal layers are ______ with each other as the ______, which suspends the gut tube from the ______ into the ______.

Answer 18

continuous, dorsal mesentery, posterior body wall, peritoneal cavity

Question 19

SEROUS MEMBRANES

Dorsal mesentery extends continuously from the ______ limit of the ______ to the ______ of the ______.

Answer 19

caudal, foregut, end, hindgut

Question 20

SEROUS MEMBRANES

Ventral mesentery exists only from the ______ to the ______ portion of the ______ and results from thinning of ______ of the ______, a block of mesoderm that forms connective tissue in the liver and forms a scaffold for formation of the diaphragm.

Answer 20

caudal foregut, upper, duodenum, mesoderm, septum transversum

Question 21

SEROUS MEMBRANES

These mesenteries are ______ layers of ______ that provide a pathway for ______, ______, and ______ to the organs.

Answer 21

double, peritoneum, blood vessels, nerves, lymphatics

Question 22

Clinical Correlates
Ventral Body Wall Defects

Ventral body wall defects occur in the ______, ______, and ______ and involve the ______ [______], ______ [______], and/or ______ or ______], depending on the location and size of the abnormality.

Answer 22

thorax, abdomen, pelvis, heart, ectopia cordis, abdominal viscera, gastroschisis, urogenital organs bladder, cloacal exstrophy

Question 23

Clinical Correlates
Ventral Body Wall Defects

The malformations are due to a failure of the ______ to close and probably involve the ______ to a greater extent than the ______ and ______ folds. Thus, one or both of the ______ fail to progress ______ or there are abnormalities in the ______ process once they meet in the midline.

Answer 23

ventral body wall, lateral body wall folds, head, tail, lateral body wall folds, ventrally, fusion

Question 24

Clinical Correlates
Ventral Body Wall Defects

An ______ also represents a ventral body wall defect; however, its primary cause is not due to inhibition of body wall closure. Instead, this abnormality occurs when a portion of the ______ fails to return to the ______ following its normal ______ into the ______.

Answer 24

omphalocele, gut tube, abdominal cavity, herniation, umbilical cord

Question 25

Clinical Correlates Ventral Body Wall Defects ______ occurs when lateral body wall folds fail to close the midline in the thoracic region causing the heart to lie outside the body cavity.

Answer 25

Ectopia cordis

Question 26

Clinical Correlates Ventral Body Wall Defects Sometimes, the closure defect begins at the caudal end of the sternum and extends into the upper abdomen resulting in a spectrum of abnormalities called ______. This spectrum includes ______, defects in the ______ region of the ______, absence of the ______, defects in the ______, and abdominal wall defects including ______ and ______.

Answer 26

Cantrell pentalogy, ectopia cordis, anterior, diaphragm, pericardium, sternum, omphalocele, gastroschisis

Question 27

Clinical Correlates Ventral Body Wall Defects Note: Omphaloceles that may occur in Cantrell pentalogy are ______ to the body wall closure defect, not ______. The closure defect reduces the ______ of the ______ and prevents the return of the ______ from the ______.

Answer 27

secondary, primary, size, abdominal cavity, intestinal loops, umbilical cord

Question 28

Clinical Correlates Ventral Body Wall Defects ______ occurs when body wall closure fails in the abdominal region. As a result, ______ herniate into the ______ through the defect, which usually lies to the ______ of the ______.

Answer 28

Gastroschisis, intestinal loops, amniotic cavity, right, umbilicus

Question 29

Clinical Correlates Ventral Body Wall Defects The incidence of gastroschisis is increasing [______/______], and it is most common in infants from thin white women younger than ______ years of age. The defect can be detected by ______ and by elevated ______ concentrations in ______ and the ______. The malformation is not associated with chromosome abnormalities, but other defects occur in ______% of cases, including heart defects in ______%. Affected loops of bowel may be damaged by exposure to ______, which has a corrosive effect, or by twisting around each other [______] and compromising their blood supply.

Answer 29

3.5, 10,000, 20, fetal ultrasound, a-fetoprotein [AFP], maternal serum, amniotic fluid, 15, 5, amniotic fluid, volvulus

Question 30

Clinical Correlates Ventral Body Wall Defects ______ or ______ results from abnormal body wall closure in the pelvic region.

Answer 30

Bladder, cloacal exstrophy

Question 31

Clinical Correlates Ventral Body Wall Defects ______ represents a less severe closure defect in the pelvic region and only the ______ is exposed; in males, the ______ may be involved and ______ [a split in the dorsum of the penis; is common].

Answer 31

Bladder exstrophy, bladder, penis, epispadias

Question 32

Clinical Correlates Ventral Body Wall Defects ______ results from a more severe failure of body wall closure in the pelvis such that the ______ and ______, which are derived from the ______, are exposed.

Answer 32

Cloacal exstrophy, bladder, rectum, cloaca

Question 33

Clinical Correlates Ventral Body Wall Defects ______ represents another ventral body wall defect, but it does not arise from a failure in body wall closure. Instead, it originates when portions of the ______ [the ______] that normally herniates into the ______ during the ______ to the ______ weeks [______] fails to return to the ______.

Answer 33

Omphalocele, gut tube, midgut, umbilical cord, 6th, 10th, physiological umbilical herniation, abdominal cavity

Question 34

Clinical Correlates Ventral Body Wall Defects Omphalocele Subsequently, ______, and other ______, including the ______, may herniate into the defect. Because the umbilical cord is covered by a reflection of the ______, the defect is covered by this ______ layer. [In contrast, loops of bowel in ______ are not covered by amnion because they herniate through the ______ directly into the ______.]

Answer 34

loops of bowel, viscera, liver, amnion, epithelial, gastroschisis, abdominal wall, amniotic cavity

Question 35

Clinical Correlates Ventral Body Wall Defects Omphalocele, which occurs in ______/______ births, is associated with high mortality rates and severe malformations, including ______ abnormalities and ______ defects. Furthermore, chromosome ab- normalities are present in ______% of cases. Like gastroschisis, omphaloceles are associated with elevated ______ concentrations.

Answer 35

2.5, 10,000, cardiac, neural tube, 15, AFP

Question 36

DIAPHRAGM AND THORACIC CAVITY The ______ is a thick plate of mesodermal tissue occupying the space between the ______ and the stalk of the ______.

Answer 36

septum transversum, thoracic cavity, yolk sac

Question 37

DIAPHRAGM AND THORACIC CAVITY The septum is derived from ______ (______) mesoderm surrounding the ______ and assumes its position between the ______ and ______ when the ______ end of the embryo grows and curves into the ______.

Answer 37

visceral, splanchnic, heart, primitive thoracic, abdominal cavities, cranial, fetal position

Question 38

DIAPHRAGM AND THORACIC CAVITY This septum (septum transversum) does not separate the thoracic and abdominal cavities completely but leaves large openings, the ______, on each side of the ______.

Answer 38

pericardioperitoneal canals, foregut

Question 39

DIAPHRAGM AND THORACIC CAVITY When lung buds begin to grow, they expand ______ within the ______.

Answer 39

caudolaterally, pericardioperitoneal canals

Question 40

DIAPHRAGM AND THORACIC CAVITY As a result of the rapid growth of the lungs, the pericardioperitoneal canals become too ______, and the lungs begin to expand into the ______ of the body wall ______, ______, and ______. Ventral and lateral expansion is posterior to the ______.

Answer 40

small, mesenchyme, dorsally, laterally, ventrally, pleuropericardial folds

Question 41

DIAPHRAGM AND THORACIC CAVITY At first, these folds (pleuropericardial folds) appear as small ______ projecting into the primitive undivided ______.

Answer 41

ridges, thoracic cavity

Question 42

DIAPHRAGM AND THORACIC CAVITY With expansion of the lungs, ______ of the body wall forms two components: (1) the definitive ______ of the ______ and (2) the ______, which are extensions of the pleuropericardial folds that contain the common ______ and ______.

Answer 42

mesoderm, wall, thorax, pleuropericardial membranes, cardinal veins, phrenic nerves

Question 43

DIAPHRAGM AND THORACIC CAVITY Subsequently, descent of the ______ and positional changes of the ______ shift the common ______ toward the ______, and the pleuropericardial membranes are drawn out in ______ fashion. Finally, they fuse with each other and with the root of the ______, and the ______ is divided into the definitive ______ and two ______.

Answer 43

heart, sinus venosus, cardinal veins, midline, mesentery-like, lungs, thoracic cavity, pericardial cavity, pleural cavities

Question 44

DIAPHRAGM AND THORACIC CAVITY In the adult, the pleuropericardial membranes form the ______.

Answer 44

fibrous pericardium

Question 45

FORMATION OF THE DIAPHRAGM Although the pleural cavities are separate from the ______, they remain in open communication with the ______ (______) cavity by way of the ______.

Answer 45

pericardial cavity, abdominal, peritoneal, pericardioperitoneal canals

Question 46

FORMATION OF THE DIAPHRAGM During further development, the opening between the prospective pleural and peritoneal cavities is partially closed by crescent-shaped folds, the ______, which project into the caudal end of the pericardioperitoneal canals.

Answer 46

pleuroperitoneal folds

Question 47

FORMATION OF THE DIAPHRAGM By the ______ week, the folds (pleuroperitoneal folds) become thinner to form the ______ that grow medially to fuse with the ______ of the ______ that forms the ______ of the ______ around the ______. The ______ then continue to grow until they fuse with each other and completely cover the ______.

Answer 47

seventh, pleuroperitoneal membranes, mesentery, esophagus, crura, diaphragm, aorta, pleuroperitoneal membranes, septum transversum

Question 48

FORMATION OF THE DIAPHRAGM The central region of these fused membranes (pleuroperitoneal membranes) forms the ______ of the ______, whereas their periphery forms ______ that serves as a scaffold and guide for migrating ______.

Answer 48

central tendon, diaphragm, connective tissue, myoblasts

Question 49

FORMATION OF THE DIAPHRAGM These muscle cells (myoblasts) originate from ______ segments ______ to ______ (______—______) to form the musculature of the diaphragm.

Answer 49

cervical, three, five, C3, C5

Question 50

FORMATION OF THE DIAPHRAGM Innervation of the diaphragm is via the ______ that are derived from ______ of ______ carrying motor and sensory fibers that also originate from ______ to ______.

Answer 50

phrenic nerves, ventral primary rami, spinal nerves, C3, C5

Question 51

FORMATION OF THE DIAPHRAGM The reason that muscle cells and nerve fibers from cervical segments populate and innervate the diaphragm is because the ______ region is where diaphragm development originated in the ______ week.

Answer 51

cervical, fourth

Question 52

FORMATION OF THE DIAPHRAGM Later, in the ______ week, differential growth, whereby growth of the ______ part of the embryo (brain and vertebral column) is greater than the ______ part, causes the diaphragm to move ______ and ______ to its final location, resulting in the ______ taking a long course to reach their destination.

Answer 52

sixth, dorsal, ventral, ventrally, caudally, phrenic nerves

Question 53

FORMATION OF THE DIAPHRAGM In summary, the diaphragm is derived from the following structures: The two pleuroperitoneal membranes form the ______ of the ______ and provide a ______ scaffold for muscle cells migrating in on the ______.

Answer 53

central tendon, diaphragm, connective tissue, periphery

Question 54

FORMATION OF THE DIAPHRAGM In summary, the diaphragm is derived from the following structures: Muscular components from ______ at cervical segments ______ to ______.

Answer 54

somites, three, five

Question 55

FORMATION OF THE DIAPHRAGM In summary, the diaphragm is derived from the following structures: The mesentery of the ______, in which the ______ of the diaphragm develop

Answer 55

esophagus, crura