Body Formation Flashcards
What permitted reptiles, mammals and birds to move away from aquatic environment?
Evolution of extra-emryonic or fetal membranes
What are the 6 overall functions extra-embryonic membranes?
Hormone Protection
Immune Protection
Supply/storage of nutrients
Mechanical Protection
Excretion of Wastes
Gas Exchange
What are the 4 extra embryonic membranes?
Chorion
Amnion
Yolk Sac
Allantois
What is the 1st extra-embryonic membrane to be formed?
Yolk Sac
What is the chorion derived from?
Trophectoderm, near the embryonic disc
What is the outermost extra-embryonic membrane?
Chorion
What are the functions of the chorion?
Gas Exchange
Respiration
In reptiles and birds, what would be up against the egg shell?
Chorion
What is the most evolutionarily significant membrane?
Amnion
Explain the amnion
Surrounds the embryo proper and provides an aquatic micro-environment which permits embryogenesis in water
- Prevents dessication
- Acts as shock absorber
What is the amniotic cavity formed by?
Formed by the fusion of the somatopleure around the embryo
What occurs in ruminants that doesnt occur in other species?
Mesamnion remains. Which causes for amnion to be torn at birth
In other species it disappears after fusion occurs and neonates will be covered with an intact amnion that will need to be removed
What does the allantois do?
Acts to stor urinary wastes from embryo’s developing urinary system and mediate gas exchange
In mammals what does the size of the allantois depend upon?
How well nitrogenous wastes are removed by chorionic placenta, but it can fill the entire extra-embryonic coelom
What can the allantois in reptiles and birds become?
It can become quite large and apposed to chorion keeping toxic by-products of metabolism away from the embryo
What is the composition of fetal fluids?
Similar to fetal and maternal blood plasma
Secretions from skin and from developing respiratory tract go into amniotic fluid
Secretions from allantoic membrane go into the allantoic fluid
Once kidneys are functional, urine goes into the fluid too
What are Hydrops?
Excessive accumulation of fetal fluids in either Amnion or Allantois in Cattle
What are two forms of Hydrops?
Hydrallantois
Hydramnion
Explain Hydrallantois
Present 6-9 months gestation with up to 40X excess fluid
Clinically present as progressive distension of the right abdominal wall and thought to be result of placental abnormalities
You are presented with pregnant cow 6-9months gestation with progressive distension of the right abdominal wall.
What could be the issue?
Hydrallantois - a form of hydrops which is excessive accumulation of fetal fluids in the allantois
Explain Hydramnion
8-10X normal fluid level associated with malformation of the digestive system
Initially, what are developing heart and lungs surrounded by?
Left and right segments of pleuro-pericardial cavity
Folds of mesoderm
Pleuropericardial folds grow medially into the left and right parts of the pleuro-pericardial cavity eventually fusing to separate the pleural from the pericardial cavity
What will the heart be suspended in?
One pericardial cavity when ventral and dorsal mesocardium are lost
As diaphram forms, what does it separate?
Separates the pleuro-pericardial cavity from the developing peritoneal cavity
closure of the space between pleural cavities and peritoneal cavity occurs as a result of what?
Growth fo the pleuro-peritoneal folds from the lateral body wall to fuse with septum transversum and the mesothelial fold suspending the esophagus
What is the primordial diaphram?
Closure of the space between pleural cavities and peritoneal cavity
When do congenital anomalies of the diaphragm occur?
When components of it do not fuse and completely partion the abdominal from the thoracic cavities
What is a congenital diaphragmatic herniation?
When abdominal viscer pass through an opening into the thoracic cavity
What are the two types of congenital hernia?
Pleuro-peritoneal herniation
Peritoneal-pericardial herniation
Explain Pleuro-peritoneal herniation
Failure of one or both pleuro-peritoneal folds to develop or fuse with mesoesophagus and septum transversum
Usually occurs on left side
Viscera are present in pleural cavity
Explain Peritoneal-pericardial herniation
Defect in development of septum transversum leading to improper comunication between peritoneal and pericardial cavities
Herniation of viscera such as the liver
What do lateral body folding result in?
Left and right intra-embryonic coeloms surrounding the developing gut
What is gut suspended by?
Folds of splanchnic mesoderm = visceral mesoderm, between the coelomic cavities lined by mesothelium
What is Gastroschisis?
Failure of ventral body wall to close in the abdominal region
Movement of abdominal contents
What is one of the most common developmental defects in pigs?
Congenital umbilical hernias
What is congenital umbilical hernia
Protrusion of viscera occurs around umbilicus due to lack of muscular body wall in that region
