Body Folding and Body Cavities Flashcards
WHat are the three phases of Embryonic Development
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
What is the intraembryonic Coelom and what does it divide the lateral mesoderm into
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
What is the somatic layer of the lateral mesoderm continous with
(parietal)
continous with the extraembryonic mesoderm covering amniion
What is the splanchnic layer of lateral mesoderm continuous with
(Visceral)
Continuous with the extraembryonic mesoderm covering the umbilical vesicle
What is Somatopleure
Somatic mesoderm and overlying embryonic ectoderm forming the body wall
What is Splanchnopleure
Splanchnic Mesoderm and underlying embryonic endoderm forming the embryonic gut
Where does folding occur in the embryo and where does constriction occur
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
the 4 steps of the Head fold
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)
What happens after to the coelom before and after the head folding:
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
What occurs before and after the tail folding:
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)
What occurs in the lateral folding
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
What is Gastroschisis
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
What is a congenital epigastric Hernia
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
What are the three body cavities derived from the Intraembryonic coelom
Pericardial Cavity
Pleural cavities
Peritoneal cavity
What embryonic tissue lines body cavities and what are its two components
Mesothelium
Parietal wall derived from somatic mesoderm (future parietal layer of peritoneum)
Visceral wall derived from splanchnic mesoderm (future visceral layer of peritoneum
After the head folds how is the intraembryonic coelom reshaped
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
What are the two partitions that form in each pericardioperitoneal canal and how do they form
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
What are the 4 components of the diaphragm
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
What is the innervation of the diaphragm and how does it embryoligically come to be
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
What is congenital Diaphragmatic Hernia
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
