Body Folding & Body Cavities Flashcards
Define embryonic growth ?
cell division and elaboration fo cell products
Define embryonic morphogenesis?
How is it controlled?
-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
Define embryonic differentiation?
cells organized in precise pattern of tissue & organs that are capable of performing specialized functions
What is a coelom?
body cavity lined by epithelium derived from mesoderm
What is the first step in embryonic folding and when does it occur?
-primordium of intraembryonic coelom appear ; they coal’s two make intra embryonic coelom
Week 4 (during same time as neurulation
What does the intraembryonic coelom split the lateral plate mesoderm into?
- somatic (parietal) layer
- splanchnic (visceral layer)
what two layers of embryo for the body wall?
what is it called?
- somatic layer and ectoderm
- somatopleure
What two layers of embryo for the embryonic gut?
what is it called?
- splanchnic layer and endoderm
- splanchnopleure
What 3 planes does the embryo fold in simultaneously to get shape?
horizontal (cranial and caudal) and coronal (lateral) planes
When does the embryo begin to fold cranially?
Day 22 (4th wk)
Describe what happens during cranial folding
- 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
What is the result of cranial folding?
- 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
what primordial features does the foregut turn into?
-future pharynx, esophagus, lower respiratory system
Are the intraembryonic and extra embryonic coeloms in communication after cranial folding?
YES
Describe what happens during tail folding?
- -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
What promotes tail folding?
growth of distal neural tube (SC primordium)
What is the hindgut give rise to?
-descending colon, rectum
What does the terminal hind gut give rise to?
forms cloaca = rudiment of bladder and rectum
What is the allantois?
diverticulum of umbilical cord
What is the connecting stalk?
future umbilical cord
What initiates lateral folding?
rapid growth of SC and sorties
Describe lateral folding
- 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
Result of lateral folding?
- IEC and EEC no longer in communications
- amnion forms epithelial of umbilical cord
- midgut connected to 2ndry yolk sac via vitalline duct
- midgut formed
What is Gastroschisis and what embryo step went awry?
protrusion of viscera due to failure of proper lateral folding
- bowel is uncovered and in amniotic fluid
- defect is right of the umbilical cord
What is congenital epigastric hernia and what embryo step went awry?
- 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)
What does the intraembryonic coelom create?
- pericardial cavity
- pleural cavity
- peritoneal cavity
What does the extra embryonic coelom create?
- chorionic sac
- amniotic sac
- yolk sac
- allantois
What are the intraembryonic coelom cavities lined with?
mesothelium (simple squamous)
What folding causes the reshaping of the IEC?
cranial/head folding
What does reshaping of the IEC due to cranial folding result in?
- pericardial cavity
- pericardioperitoneal canals
Describe the process by which the IEC turns into the pericardial cavity and formation of the pericardiopertioneal canals
- 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
What is the location of the septum transversum before cranial folding and after folding/reshaping of IEC?
- before : ventral to IEC, primordial heart, and foregut
- after : caudal to pericardial cavity and primordial heart ; ventral to pericardioperitoneal canals ;
What is the dorsal mesentery? and what does it do?
- derivative of splanchopleuric mesoderm
- suspends formed, and hindgut in peritoneal cavity
What is the septum transversum?
primordial central tendon of the diaphragm
What causes the creation of pleural and peritoneal cavities?
growth of primordial lungs
Describe the process of creating the pleural cavity?
- 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
When is the pleural cavity created?
7th week
What allows the pericardioperitoneal canal to expand to allow for septation?
bronchial buds
What do the bronchial buds do to the mesenchyme?
-splits it to an outer and inner layer
outer = thoracic wall (parietal) inner = fibrous pericardium (outer layer of pericardial sac
Describe the process of creating the peritoneal cavity
- 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)
When is the peritoneal cavity created?
6th week
What 4 components make up the diaphragm? and what do they turn into?
- septum transversum (central tendon of diaphragm)
- pleuroperitoneal membrane (primordial of diaphragm)
- dorsal mesentery (median portion of diaphragm)
- myoblasts (cur of diaphragm)
Describe the innervation of the diaphragm
- 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
What is congenital diaphragmatic hernia?
-posterolateral visceral buldge into pleural cavity cause by failure of septum transversum to fuse posters-laterally with the pleuroperitoneal membrane
What are the features of congenital diaphragmatic hernia?
- lung maturation delayed
- polyhydramnios may be present
- LEFT SIDE
- corrected at birth
