Summary for Quiz One

Question 1

Explain the process of gastrulation:

Answer 1

• Endoderm is replaced by gastrulating cells that invade and replace the entire hypoblast layer
• Ectoderm formed by cells remaining in the epiblast
• Mesoderm formed by cells that migrate between these two layers
• Protostomes- mouth first, deuterostomes- mouth second

Question 2

What are the three embryological germ layers and what are the derivatives of them?

Answer 2

• Ectoderm- the outermost layer- epidermis and nervous tissue
• Mesoderm- the middle layer – muscle and connective tissues
• Endoderm- inner layer- gut, liver, lungs

Question 3

Name each of these features on an egg:

Answer 3

1. Amnion
2. Shell
3. Chorion
4. Yolk
5. Albumen
6. Allantois

Question 4

Name a unique feature of bovine placentas:

Answer 4

Coyledonary appearance

Question 5

Describe the pattern of blood flow through a foetal heart:

Answer 5

1. Blood enters the right atrium
2. Right atrium blood goes to the left atrium (via the foramen ovale)
3. Small amount of blood goes from the right atrium to the right ventricle and this is then shunted away from the pulmonary artery to the aorta via the ductus arteriosus

Question 6

What are the main changes to the pattern of foetal blood flow that occur at birth?

Answer 6

1. Pulmonary circuit pressure decreases, while systemic circuit pressure ultimately increases
   * Because when oxygen diffuses into blood vessels surrounding the alveoli, the pulmonary arterioles will relax and pulmonary resistance will fall so blood will flow into the lungs
2. Closure of the ductus arteriosus

• Pressure changes causes decreased blood flow through the ductus arteriosus
• Complete closure 12-24 hours after birth
• Physical remanent- ligamentum arteriosum

1. Closing of the foramen ovale

• Pressure in the right side of the heart falls- sealing the foramen ovale
• Physical remanent- fossa ovalis

Question 7

How many pharyngeal arches are there?

Answer 7

6 pharyngeal arches exist

Question 8

What is formed by cleft one and pouch one?

Answer 8

auditory tube and the external ear

Question 9

What does pouch two normally form?

Answer 9

Palantine tonsils

Question 10

What is formed by the pouches 3-6?

Answer 10

Endocrine glands

Question 11

What is formed by pharyngeal arch one?

Answer 11

Merkels cartiladge

Question 12

What is normally formed by pharyngeal arch two?

Answer 12

Styloid process

Question 13

What is normally formed by phayngeal arch 3?

Answer 13

Hyoid Bone

Question 14

What is normally formed by pharyngeal arch 4 and 5?

Answer 14

Thyroid cartiladge and hyoid cartiladge

Question 15

How does a cleft palate form?

Answer 15

• Cleft palate is a condition that will typically occur when the palatine process and the incisor processes fail to meet up correctly during embryological development
• The hard palate does not form and as a consequence the animal will not be able to suckle

Question 16

How does a cleft lip normally form?

Answer 16

Forms as a result from the failure of fusion of the medial nasal prominences with maxillary prominences