Lecture 29/Animal Dev III

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Lecture 29: Animal Development III

Campbell, 5th, pp. 928-929, bottom 939-top 950, 953-955
(Campbell, 4th.,953-955, 967-mid 981

I. Vertebrate development
A. Amphibians47.8, 47.10
1. Cleavage - holoblastic, but distorted
Amphibian oocytes contain more yolk than sea urchin eggs and it's concentrated at the vegetal pole. As a consequence, the cleavage furrow moves more slowly through the vegetal region. Vegetal cells divide later than animal pole cells and are larger. A blastula is formed, with the cavity towards the animal pole.

2. Gastrulation through blastopore
Those big, yolky cells don't move either, but they're the ones that need to be brought inside to form the gut. The simple method of gastrulation used by the sea urchin embryo is out of the question. Instead, the rest of the embryo moves around the yolky mass and engulfs it.

3. Cells of the dorsal lip form blastopore
The inward movement is begun by the cells that form the opening or blastopore.

4. Spemann's "Organizer"47.21. 47.22
- established by events at time of fertilization
- gastrulation linked toaxis formation

5. Neural tube

47.11

B. Birds
1. Meroblastic cleavage
2. Flat blastodisc
3. One layer splits in two (delamination)
4. Gastrulation through primitive streak
5. Primitive streak defines the A-P axis
6. Formation of extraembryonic membranes
a. amnion
b. chorion
c. allantois
d. yolk sac

47.12

47.14


Lecture 29: Animal Development III Campbell, 5th, pp. 928-929, bottom 939-top 950, 953-955 (Campbell, 4th.,953-955, 967-mid 981 I. Vertebrate development A. Amphibians47.8, 47.10 1. Cleavage - holoblastic, but distorted Amphibian oocytes contain more yolk than sea urchin eggs and it's concentrated at the vegetal pole. As a consequence, the cleavage furrow moves more slowly through the vegetal region. Vegetal cells divide later than animal pole cells and are larger. A blastula is formed, with the cavity towards the animal pole. 2. Gastrulation through blastopore Those big, yolky cells don't move either, but they're the ones that need to be brought inside to form the gut. The simple method of gastrulation used by the sea urchin embryo is out of the question. Instead, the rest of the embryo moves around the yolky mass and engulfs it. 3. Cells of the dorsal lip form blastopore The inward movement is begun by the cells that form the opening or blastopore. 4. Spemann's "Organizer"47.21. 47.22 - established by events at time of fertilization - gastrulation linked toaxis formation
		5. Neural tube		47.11
	B. Birds 1. Meroblastic cleavage 2. Flat blastodisc 3. One layer splits in two (delamination) 4. Gastrulation through primitive streak 5. Primitive streak defines the A-P axis 6. Formation of extraembryonic membranes a. amnion b. chorion c. allantois d. yolk sac
			47.12 47.14