Body Cavities And body Folding Flashcards
What defines Growth as a phase of embryonic development?
Cell division and elaboration of cell products
What defines Morphogenesis as a phase of embryonic development ?
Development of f shape, size and other features of a particular organ or part of whole body
How is Morphogenesis controlled?
What changes will this lead to?
Controlled by gene expression and regulation in an orderly sequence
Changes in
- cell fate
- cell shape
- cell movement
What does Morphogenesis allow fo?
Allows cells to interact w/ each other during the formation of tissues and organs
What defines Differentiation as a phase of embryonic development?
Organization of cells into a precise pattern of tissues and organs capable of performing specialized functions
What will form the primordium of the intraembryonic coelom?
Isolated coelomic spaces int he lateral plate and cardiogenic mesoderm
What is a coelom?
Embryonic body cavity
How is the intraembryonic coelom formed?
What shape does this take on?
Thru the coalescing of isolating coelomic spaces
Horseshoe shaped
What will the formation of the Itnraembyronic coelom do tot he Lateral mesoderm?
Divides lateral mesoderm into
- Somatic/parietal layer of lateral mesoderm
- Splanchnic/visceral layer of lateral mesoderm
What is the somatic layer of lateral mesoderm continuous w/ ?
Continuous w/ extra-embryonic mesoderm covering the amnion
What is the splanchnic layer of the lateral mesoderm continuous w/?
W/ extra-embryonic mesoderm covering the umbilical vesicle
What is somatopleure?
What doe this form?
Somatic mesoderm and overlying embryonic ectoderm
forms the body wall
What is splanchopleure?
What will it form?
Splanchnic mesoderm and underlying embryonic endoderm
forms embryonic gut
How does folding in the embryonic planes occur?
Folding in cranial and caudal and sides simultaneously
What does the body folding of the embryonic in the median and horizontal planes do?
Takes flat,trilaminar embryonic disc
—>
Cylindrical embryo
Does folding occur faster laterally or in the median plane?
Lateral edges do not keep pace w/ the increase in embryo length
What day does the head fold begin?
Day 22/week 4
How does Head Folding occur?
- Embryo elongates in length
- Neural folds grow over the oropharyngeal membrane
- This moves the septum transversum, primordial heart, pericardial coelom and oropharyngeal membrane to ventral (front) surface
- Part of endoderm of umbilical vesicle is incorporated as foregut
What comprises the foregut?
Primordium of pharynx, esophagus, and lower respiratory system
After head folding, how is the intra-embryonic coelom?
Pericardial cavity is at front
Pericardioperitoneal canal run dorsally on each side of foregut
Intraembryonic and extraembryonic coelom are in communication
What is the process of tail folding?
- Caudal (back) end of embryonic folds in due to growth of distal neural tube
Forms the spinal cord primordium - Caudal eminence projects over the cloacal membrane
- Part of endoderm from Allantois will form hindgut
- Terminal hindgut dilates to form the cloaca
What is the future of the cloacal membrane?
To form the anus
What comprises the hindgut?
Descending colon/rectum
What is the cloaca?
Rudiment of urinary bladder/rectum
Before tail folding where did the primitive streak lie?
After folding?
Before: primitive streak lies cranial to cloacal membrane
After: lies caudal to cloacal membrane
What is the allantois/
Diverticulum of the umbilical vesicle
What produces the right and left lateral folds?
Rapid growth of SC and smites
What happens when the lateral fold extend ventrally toward midline
Creates a cylindrical embryo
Abdominal walls forms and incorporates ENDOderm to form midgut
Omphaloentric duct is formed
How is the omphaloenterifc duct formed?
By reducing the connection b/w the umbilication vesicle and midgut
What happens as the umbilical cord forms?
Communication between the intraembryonic and extra-embryonic coelomic cavities narrows
What will eventually obliterate most of the extraembryonic coelom?
Expansion of the amniotic cavity
What does the amnion form for the umbilical cord?
Forms epithelial covering
What is the intraembryonic coelom divided into?
Pericardial cavity
Pleural cavities
Peritoneal cavity
What are the cavities of the intraembryonic coelom lined with?
With mesothelium
- parietal walls from somatic mesoderm
- visceral wall from splanchnic mesoderm
How do head folds reshape the intraembryonic coelom re: Pericardial cavity?
Pericardial cavity..
moved ventrally and anterior to foregut and above septum transversum (heart will reposition itself into this cavity)
opened into peri-cardio-peritoneal canals lateral to foregut
What is the function of the pericardioperitoneal canals?
Connect pericardial cavity tot he peritoneal cavity
How do head folds reshapes the intraembryonic coelom re: Peritoneal cavity?
Relocated so IE and EE coeloms are continuous f
What is suspended in the peritoneal cavity and how?
Caudal foregut, midgut, and hindgut are suspended by dorsal mesentery
What is the septum transversum?
Primordium of the central tendon of diaphragm
How do partitions form in the pericardioperitoneal canals?
Partitions form due to growth of primordial lounges
What are the 2 folds found in each pericardial peritoneal canal?
Pleuro-pericardial folds
Pleuro-peritoneal folds
What is the function of pleuro-pericardial folds?
Separate head from lungs
Where do pleuro-pericardial folds develop in the pericardial-peritoneal canals?
Develop above developing lungs
What will the pleuro-pericardial folds form upon enlargement?
Form pleuropericardial membranes
How do the pericardial cavities and 2 pleural cavities become separated?
When do they become separate?
Pleuropericardial membranes fuse w/ mesenchyme in front of esophagus
Week 7
What will grow into he pericardioperitoneal canals?
What will this cause?
Bronchial buds
Will cause cavity to expand and mesenchyme to split
What will the growing bronchial buds cause mesenchyme to split into?
Outer layer —> thoracic wall
Inner layer —> fibrous pericardium (outerlayer of pericardial sac)
What do the pleuroperidaial folds form form and where?
From somatic layer of the lateral plate mesoderm (somatic = parietal)
On lateral body wall
How many layers do the pleuropericardial folds have?
3 layers
Epithelia-mesenchym-epithelie
How is the primordial diaphragm formed?
Pleuroperitoneal membrane fuses with the dorsal mesentery of esophagus and septum transversum
What forms the central tendon of the diaphragm?
Expansion of the septum transversum and subsequent fusion w/ the dorsal mesentery of the esophagus and Pleuroperitoneal membranes
What is the dorsal mesentery?
Median portion of diaphragm
How is the Crura of the diaphragm formed?
From myoblasts growing into the dorsal mesentery
What is the innervation of the diaphragm?
Why?
As myoblasts migrated into the dorsal mesentery it pulled ventral rami C3-C5 with them
They passed thru pleuroperidarical membranes
—>
Phrenic n. Lies on fibrous pericardium
What is Gastroschisis?
Protrusion of viscera;
site of abdominal defect to right of umbilical cord rather than midline
How common is gastroschisis?
1 in 3000 live births
How is Gastroschisis different from an umbilical hernia?
Bowel is uncovered and floating in amniotic fluid
Why does Gastroschisis occur?
Results from failure of the lateral body folds to fuse complete when the anterior abdominal wall forms
When does the anteiror abdominal wall form?
4th week
What is a congenital Epigastric hernia?
Midline bulge of abdominal wall located b/w the xyphoid process and umbilicius
Bowel is not exposed to amniotic fluid; remained covered by skin and subcutaneous tissues
What is Congenital Diaphragmatic hernia? (CDH)
A posterolateral defect where viscera bulge into the plural cavity
What is the occurrence of Congenital diaphragmatic hernias?
1 in 2200 live births
What can cause Congenital DIaphragmatic hernias?
-improper closure of body cavities
-open left canal bc of lack of myoblasts migrating into the pericardioperitoneal canals/membrane
(Right closes before left, so usually left is affected)
What are some consequences of a Congenital Diaphragmatic Hernia?
Which side is typically affected more?
Delayed lung maturation
Polyhydramnios
Left side affected 80% of time
