Body Folding & Body Cavities

Question 1

Define embryonic growth ?

Answer 1

cell division and elaboration fo cell products

Question 2

Define embryonic morphogenesis?

How is it controlled?

Answer 2

-devp. of size, shape, etc of a particular organ or part of whole body

–> controlled by gene expression and regulation ; changes in cell fate, shape, and movement allow interaction b/w cells during formation

Question 3

Define embryonic differentiation?

Answer 3

cells organized in precise pattern of tissue & organs that are capable of performing specialized functions

Question 4

What is a coelom?

Answer 4

body cavity lined by epithelium derived from mesoderm

Question 5

What is the first step in embryonic folding and when does it occur?

Answer 5

-primordium of intraembryonic coelom appear ; they coal’s two make intra embryonic coelom

Week 4 (during same time as neurulation

Question 6

What does the intraembryonic coelom split the lateral plate mesoderm into?

Answer 6

• somatic (parietal) layer

- splanchnic (visceral layer)

Question 7

what two layers of embryo for the body wall?

what is it called?

Answer 7

• somatic layer and ectoderm

- somatopleure

Question 8

What two layers of embryo for the embryonic gut?

what is it called?

Answer 8

• splanchnic layer and endoderm

- splanchnopleure

Question 9

What 3 planes does the embryo fold in simultaneously to get shape?

Answer 9

horizontal (cranial and caudal) and coronal (lateral) planes

Question 10

When does the embryo begin to fold cranially?

Answer 10

Day 22 (4th wk)

Question 11

Describe what happens during cranial folding

Answer 11

• the primitive brain will overgrow the oropharyngeal membrane
• this will push the septum transversum, IEC, and primordial heart ventrally
• it will also pull the forget ( endoderm of umbilical vesicle) with it

Question 12

What is the result of cranial folding?

Answer 12

• pericardial cavity, primordial heart, and septum transverse are ventral
• oropharyngeal membrane is now cranial to those structures
• foregut is dorsal to all of those structures

-pericardioperitoneal canals are dorsal to pericardial cavity and heart, lateral to foregut

Question 13

what primordial features does the foregut turn into?

Answer 13

-future pharynx, esophagus, lower respiratory system

Question 14

Are the intraembryonic and extra embryonic coeloms in communication after cranial folding?

Answer 14

YES

Question 15

Describe what happens during tail folding?

Answer 15

• -caudal eminence overgrows the cloacal membrane
• this causes the push of endoderm up and in = hindgut
• pushes primitive streak caudal to cloacal membrane
• allantois is partially incorporated
• connecting stalk is moved ventrally

Question 16

What promotes tail folding?

Answer 16

growth of distal neural tube (SC primordium)

Question 17

What is the hindgut give rise to?

Answer 17

-descending colon, rectum

Question 18

What does the terminal hind gut give rise to?

Answer 18

forms cloaca = rudiment of bladder and rectum

Question 19

What is the allantois?

Answer 19

diverticulum of umbilical cord

Question 20

What is the connecting stalk?

Answer 20

future umbilical cord

Question 21

What initiates lateral folding?

Answer 21

rapid growth of SC and sorties

Question 22

Describe lateral folding

Answer 22

• embryo extends ventrally -> cylindrical shape
• abdominal wall begins to form and incorporates endoderm to for midgut (SI primordium)
• connx b/e umbilical vesicle and midgut is narrowed = omphaloenteric duct/vitalline duct
• IEC and EEC cone narrows
• amniotic cavity expands

Question 23

Result of lateral folding?

Answer 23

• IEC and EEC no longer in communications
• amnion forms epithelial of umbilical cord
• midgut connected to 2ndry yolk sac via vitalline duct
• midgut formed

Question 24

What is Gastroschisis and what embryo step went awry?

Answer 24

protrusion of viscera due to failure of proper lateral folding

• bowel is uncovered and in amniotic fluid
• • defect is right of the umbilical cord

Question 25

What is congenital epigastric hernia and what embryo step went awry?

Answer 25

- midline bulge of abdominal wall b/w diploid process of sternum and umbilicus - due to defect in lateral folding - bowel not exposed to amniotic fluid (covered by skin and subQ)

Question 26

What does the intraembryonic coelom create?

Answer 26

- pericardial cavity - pleural cavity - peritoneal cavity

Question 27

What does the extra embryonic coelom create?

Answer 27

- chorionic sac - amniotic sac - yolk sac - allantois

Question 28

What are the intraembryonic coelom cavities lined with?

Answer 28

mesothelium (simple squamous)

Question 29

What folding causes the reshaping of the IEC?

Answer 29

cranial/head folding

Question 30

What does reshaping of the IEC due to cranial folding result in?

Answer 30

- pericardial cavity | - pericardioperitoneal canals

Question 31

Describe the process by which the IEC turns into the pericardial cavity and formation of the pericardiopertioneal canals

Answer 31

- IEC moves ventrally as pericardial cavity (anterior to foregut) - cavity then creates 2 pericardioperitoneal canals that run lateral to the foregut but dorsal to the cavity - developing heart now bulging inside of pericardial cavity

Question 32

What is the location of the septum transversum before cranial folding and after folding/reshaping of IEC?

Answer 32

- before : ventral to IEC, primordial heart, and foregut | - after : caudal to pericardial cavity and primordial heart ; ventral to pericardioperitoneal canals ;

Question 33

What is the dorsal mesentery? and what does it do?

Answer 33

- derivative of splanchopleuric mesoderm | - suspends formed, and hindgut in peritoneal cavity

Question 34

What is the septum transversum?

Answer 34

primordial central tendon of the diaphragm

Question 35

What causes the creation of pleural and peritoneal cavities?

Answer 35

growth of primordial lungs

Question 36

Describe the process of creating the pleural cavity?

Answer 36

- pleuropericardial folds form superior to the lungs (house phrenic nerve and cardinal vein) - as bronchial buds grow they invaginate the fold and the fold begins to enlarge - fold projects into pericardioperitoneal canals - fold turns into membrane and fuses with mesenchyme ventral to the esophagus

Question 37

When is the pleural cavity created?

Answer 37

7th week

Question 38

What allows the pericardioperitoneal canal to expand to allow for septation?

Answer 38

bronchial buds

Question 39

What do the bronchial buds do to the mesenchyme?

Answer 39

-splits it to an outer and inner layer ``` outer = thoracic wall (parietal) inner = fibrous pericardium (outer layer of pericardial sac ```

Question 40

Describe the process of creating the peritoneal cavity

Answer 40

- pleuroperitoneal folds enlarge and project into canals - folds be/c membrane - membranes fuse with dorsal mesentery of the esophagus and septum transversum - myoblasts migrate into membrane to complete closure (diaphragm) (right closes before left)

Question 41

When is the peritoneal cavity created?

Answer 41

6th week

Question 42

What 4 components make up the diaphragm? and what do they turn into?

Answer 42

- septum transversum (central tendon of diaphragm) - pleuroperitoneal membrane (primordial of diaphragm) - dorsal mesentery (median portion of diaphragm) - myoblasts (cur of diaphragm)

Question 43

Describe the innervation of the diaphragm

Answer 43

- pleuropericardial membrane fuse with dorsal mesentery - membrane contain cardinal veins and myoblasts (diaphragm) - myoblasts pull ventral rami (C3-5) with them - passing thru membranes - phernic now on fibrous pericardium

Question 44

What is congenital diaphragmatic hernia?

Answer 44

-posterolateral visceral buldge into pleural cavity cause by failure of septum transversum to fuse posters-laterally with the pleuroperitoneal membrane

Question 45

What are the features of congenital diaphragmatic hernia?

Answer 45

- lung maturation delayed - polyhydramnios may be present - LEFT SIDE - corrected at birth