Body Formation

Question 1

What permitted reptiles, mammals and birds to move away from aquatic environment?

Answer 1

Evolution of extra-emryonic or fetal membranes

Question 2

What are the 6 overall functions extra-embryonic membranes?

Answer 2

Hormone Protection

Immune Protection

Supply/storage of nutrients

Mechanical Protection

Excretion of Wastes

Gas Exchange

Question 3

What are the 4 extra embryonic membranes?

Answer 3

Chorion

Amnion

Yolk Sac

Allantois

Question 4

What is the 1st extra-embryonic membrane to be formed?

Answer 4

Yolk Sac

Question 5

What is the chorion derived from?

Answer 5

Trophectoderm, near the embryonic disc

Question 6

What is the outermost extra-embryonic membrane?

Answer 6

Chorion

Question 7

What are the functions of the chorion?

Answer 7

Gas Exchange

Respiration

Question 8

In reptiles and birds, what would be up against the egg shell?

Answer 8

Chorion

Question 9

What is the most evolutionarily significant membrane?

Answer 9

Amnion

Question 10

Explain the amnion

Answer 10

Surrounds the embryo proper and provides an aquatic micro-environment which permits embryogenesis in water

• Prevents dessication
• Acts as shock absorber

Question 11

What is the amniotic cavity formed by?

Answer 11

Formed by the fusion of the somatopleure around the embryo

Question 12

What occurs in ruminants that doesnt occur in other species?

Answer 12

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

Question 13

What does the allantois do?

Answer 13

Acts to stor urinary wastes from embryo’s developing urinary system and mediate gas exchange

Question 14

In mammals what does the size of the allantois depend upon?

Answer 14

How well nitrogenous wastes are removed by chorionic placenta, but it can fill the entire extra-embryonic coelom

Question 15

What can the allantois in reptiles and birds become?

Answer 15

It can become quite large and apposed to chorion keeping toxic by-products of metabolism away from the embryo

Question 16

What is the composition of fetal fluids?

Answer 16

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

Question 17

What are Hydrops?

Answer 17

Excessive accumulation of fetal fluids in either Amnion or Allantois in Cattle

Question 18

What are two forms of Hydrops?

Answer 18

Hydrallantois

Hydramnion

Question 19

Explain Hydrallantois

Answer 19

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

Question 20

You are presented with pregnant cow 6-9months gestation with progressive distension of the right abdominal wall.

What could be the issue?

Answer 20

Hydrallantois - a form of hydrops which is excessive accumulation of fetal fluids in the allantois

Question 21

Explain Hydramnion

Answer 21

8-10X normal fluid level associated with malformation of the digestive system

Question 22

Initially, what are developing heart and lungs surrounded by?

Answer 22

Left and right segments of pleuro-pericardial cavity

Question 23

Folds of mesoderm

Answer 23

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

Question 24

What will the heart be suspended in?

Answer 24

One pericardial cavity when ventral and dorsal mesocardium are lost

Question 25

As diaphram forms, what does it separate?

Answer 25

Separates the pleuro-pericardial cavity from the developing peritoneal cavity

Question 26

closure of the space between pleural cavities and peritoneal cavity occurs as a result of what?

Answer 26

Growth fo the pleuro-peritoneal folds from the lateral body wall to fuse with septum transversum and the mesothelial fold suspending the esophagus

Question 27

What is the primordial diaphram?

Answer 27

Closure of the space between pleural cavities and peritoneal cavity

Question 28

When do congenital anomalies of the diaphragm occur?

Answer 28

When components of it do not fuse and completely partion the abdominal from the thoracic cavities

Question 29

What is a congenital diaphragmatic herniation?

Answer 29

When abdominal viscer pass through an opening into the thoracic cavity

Question 30

What are the two types of congenital hernia?

Answer 30

Pleuro-peritoneal herniation Peritoneal-pericardial herniation

Question 31

Explain Pleuro-peritoneal herniation

Answer 31

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

Question 32

Explain Peritoneal-pericardial herniation

Answer 32

Defect in development of septum transversum leading to improper comunication between peritoneal and pericardial cavities Herniation of viscera such as the liver

Question 33

What do lateral body folding result in?

Answer 33

Left and right intra-embryonic coeloms surrounding the developing gut

Question 34

What is gut suspended by?

Answer 34

Folds of splanchnic mesoderm = visceral mesoderm, between the coelomic cavities lined by mesothelium

Question 35

What is Gastroschisis?

Answer 35

Failure of ventral body wall to close in the abdominal region Movement of abdominal contents

Question 36

What is one of the most common developmental defects in pigs?

Answer 36

Congenital umbilical hernias

Question 37

What is congenital umbilical hernia

Answer 37

Protrusion of viscera occurs around umbilicus due to lack of muscular body wall in that region