Lecture 2

Question 1

Name the diagnostic features of Craniates

Answer 1

1) Skull
2) placodes
3) five-part brain
4) paired cranial nerves
5) neural crest
6) Gill filaments lining the gill slits
7) Endoskeleton
8) complexly digestive system
9) complex circulatory system
10) semicircular canals in the inner ear

Question 2

What is the neurocranium

Answer 2

It immediately surrounds the brain and sense organs (floor of skull)

Question 3

What is the dermatocranium

Answer 3

The outer most component of the brain, which forms an external sheath around the neurocranium

Develops from dermal bone

Question 4

The dermatocranium consists of what?

Answer 4

1) dermal bones of the cranial roof
2) dermal bones of the primary palate
3) dermal bones of the upper jaw
4) dermal bones of the lower jaw

Question 5

The neurocranium consists of what?

Answer 5

1) bones of the occipital region
2) bones of the temporal region
3) bones of the sphenoid region
4) bones of the ethmoid region

Question 6

The splanchnocranium or viscerocranium consists of what?

Answer 6

1) First arch (mandibular arch)
2) Second arch (hyoid arch)
3) Additional arches (third up to 6-7)

Question 7

What are Placodes?

Answer 7

Localised thickenings in the ectoderm (outer layer) of the head of a craniates embryo

Question 8

What are Neural crest cells?

Answer 8

A temporary group of cells unique to craniates that arise from the embryonic ectoderm cell layer and in turn give rise to diverse structures

Question 9

What are the structures that arise from neutral crests?

Answer 9

1) sensory organs (nerve cells)
2) some skeletal and connective tissues in the skull
2) some pigment-containing cells and other integumentary tissues
3) gill arches, jaws and parts of the braincase floor
4) the formation of dermal skeleton (scales, teeth and dermal bones)

Question 10

What does the skull consist of?

Answer 10

Neurocranium

Dermatocranium

Splanchnocranium

Question 11

What is the neurocranium?

Answer 11

The part of the skull which originates as cartilage around the brain and sense organs; it is the second oldest component of the skull

-box like structure

Question 12

What is the splanchocranium? (Viscerocranium)

Answer 12

The part of the skull which originates from pharyngeal arches.

Question 13

What does the brain of craniates develop from?

Answer 13

Five vescicles of the neural tube

Question 14

What are semicircular canals?

Answer 14

They detect angular acceleration and deceleration of the head.