Body Folding and Body Cavities

Question 1

WHat are the three phases of Embryonic Development

Answer 1

Growth: cell division and elaboration of cell products

Morphogenesis: devlopment of shape, size and features of a particular organ
-controlled by gene expression and regulation

Differentiation: Cells are organized in a precise pattern of tissues and organs that are capable of performing specialized functions

Question 2

What is the intraembryonic Coelom and what does it divide the lateral mesoderm into

Answer 2

Isolated coelomic spaces in the lateral plate and the cardiogenic mesoderm
-the coalesce form the horseshoe shaped cavity (intraembryonic coelom)

Divides the lateral mesoderm into the:

• Somatic layer of lateral mesoderm
• Splanchnic layer of lateral mesoderm

Question 3

What is the somatic layer of the lateral mesoderm continous with

Answer 3

(parietal)

continous with the extraembryonic mesoderm covering amniion

Question 4

What is the splanchnic layer of lateral mesoderm continuous with

Answer 4

(Visceral)

Continuous with the extraembryonic mesoderm covering the umbilical vesicle

Question 5

What is Somatopleure

Answer 5

Somatic mesoderm and overlying embryonic ectoderm forming the body wall

Question 6

What is Splanchnopleure

Answer 6

Splanchnic Mesoderm and underlying embryonic endoderm forming the embryonic gut

Question 7

Where does folding occur in the embryo and where does constriction occur

Answer 7

Occurs along the embryonic planes

occurs in the cranial and caudal ends and sides simultaneously

constriction occurs at the junction of the embryo and umbilical vesicle

Question 8

the 4 steps of the Head fold

Answer 8

1: Embryo Elongates cranially and caudally at the 4th week
2. Neural folds project dorsally and overgrow oropharyngeal membrane (soon to be mouth)
3) Overgrowth moves the septum transversum, primordial heart, pericardial coelom, and oropharyngeal membrane to ventral surface
4) Part of the endoderm of the umbilical vesicle is incorporated as the foregut (primoridim of pharynx, esophagus, and lower respiratory system)

Question 9

What happens after to the coelom before and after the head folding:

Answer 9

Before: coelom is flattened and in its respective horseshoe shaped cavity

After: -Pericardial cavity is ventral

• Pericardioperitoneal canals run dorsally on each side of the fore gut
• Intraembryonic and extraembryonic coeloms are in communciation

Question 10

What occurs before and after the tail folding:

Answer 10

occurs due to the growth of the distal neural tube

before: primitive streak lies cranial to cloacal membrane

After: primitive streak lies caudal to cloacal membrane

Caudal eminence projects over the cloacal membrane (anus)

Part of the endoderm forms the hindgut (descending colon and rectum)

Terminal hindgut forms the cloaca (urinary bladder/rectum)

Question 11

What occurs in the lateral folding

Answer 11

Creates a cylindrical embryo
Abdominal wall forms and incorporates endoderm to form the midgut (SI primordium)

COnnection between umbilical vesicle and midgut is reduced forming the omphaloenteric duct

amniotic cavity expands and obliterates most of the extraembryonic coelom

Amnion forms epithelial covering of the umbilical cord

Question 12

What is Gastroschisis

Answer 12

Protrusion of the viscera and occurs at the sited of the abdominal defect usually to the right of the umbilical cord

contents are uncovered and floating in the amniotic fluid leading to damage from the amniotic fluid

Question 13

What is a congenital epigastric Hernia

Answer 13

Midling bulge of abdominal wall located between the xiphoid process and the umbilicus

Bowel is not exposed to the amniotic fluid because it remains covered by skin and subcutaneous tissue

Question 14

What are the three body cavities derived from the Intraembryonic coelom

Answer 14

Pericardial Cavity
Pleural cavities
Peritoneal cavity

Question 15

What embryonic tissue lines body cavities and what are its two components

Answer 15

Mesothelium

Parietal wall derived from somatic mesoderm (future parietal layer of peritoneum)

Visceral wall derived from splanchnic mesoderm (future visceral layer of peritoneum

Question 16

After the head folds how is the intraembryonic coelom reshaped

Answer 16

Pericardial cavity is relocated ventrally, anterior to the foregut

the pericadial cavity opens into two pericardioperitoneal canals located dorsal to the foregut

the caudal peritoneal cavity is positioned where the IE and EE coeloms are continuous

Question 17

What are the two partitions that form in each pericardioperitoneal canal and how do they form

Answer 17

Pleuropericardial folds (cranial) and seperates the lung and the heart

Pleuroperitoneal fold (Caudal) and seperates the lung and the abdomen

form due to growth of the primordial lungs

These folds will then enlarge to become membranes and fuse with mesenchyme ventral to the esophogus and septum transversum in the 6th week

Myoblasts will then migrate into the pleuroperitoneal membrane to complete the closure

Question 18

What are the 4 components of the diaphragm

Answer 18

Septum transversum: expands and fuses with the dorsal mesentary of the esophagus and pleuroperitoneal membranes making the central tendon of the diaphragm

Pleuroperitoneal membrane: make up the primordial diaphragm

Dorsal Mesentary: make up the median portion of the diaphragm

Myoblasts: grow into the dorsal mesentary giving rise to the crura of the diaphragm

Question 19

What is the innervation of the diaphragm and how does it embryoligically come to be

Answer 19

C3,4,5

due to the myoblasts pulling the ventral rami C3-5 with them through the pleuropericardial membranes

therefore the phrenic subsequently lies on fibrous pericardium

Question 20

What is congenital Diaphragmatic Hernia

Answer 20

Viscera bulge into the pleural cavity

lung maturation may be delayed, polyhydraminos may be present

occurs due to failure to close the pericardioperitoneal canals

usually occurs on the left side since that canal opening is bigger