Devo Lect 7 - Gastrulation

Question 2

Gastrulation definition*

Answer 2

Cells move, inductive interactions; form primary tissue layers; basic body plan (tube with 2 openings)

Question 3

Basic body plan

Answer 3

Inner tube forms digestive system and respiratory tract, 2 openings are mouth and anus

Question 4

Invagination

Answer 4

Folding in of a layer

Question 5

Involution

Answer 5

Layers of cells migrating inwards

Question 6

Ingression

Answer 6

Cells leave one layer and move to another layer; in general, they stop producing some adhesin molecules and form new ones

Question 7

Delamination

Answer 7

Separate one layer into two

Question 8

Epiboly

Answer 8

A layer envelopes another

Question 9

Sea urchin gastrulation

Answer 9

Starts at blastula larvae (1000 cells); bottom forms vegetal plate; some start to ingress, these are 1˚ mesenchyme cells; invagination forms blastopore; cells divide to form tube, becomes gastrula embryo

Question 10

Archenteron

Answer 10

Name of the tube (means “primitive gut”)

Question 11

2˚ mesenchyme cells

Answer 11

In sea urchins; Pull archenteron up the blastocoel wall near the end of invagination

Question 12

Protostome and Deuterostome

Answer 12

P: 1st opening is mouth; D: 1st one is anus, 2nd is mouth

Question 13

Amphibian gastrulation

Answer 13

Blastula embryo; invagination for blastopore; bottle cells migrate as a layer inwards at the gray crescent, involution; blastocoel shrinks, new cavity forms (archenteron); epiboly of outer cells, 2nd set of bottle cells migrate in; gastrula embryo is curved, the two openings are initially close together; lip

Question 14

Yolk Plug

Answer 14

In Amphibians: the remaining patch of endoderm still exposed by blastopore; when it is covered by ectoderm, the mesoderm will be in between them

Question 15

Avian gastrulation

Answer 15

at blastoderm; embryo formed completely from epiblast; primitive streak forms as cells move down into embryo, grows from posterior end to anterior; forms Hensen’s node at anterior end (brain/head region), migrates posteriorly; involution, form mesoderm; last structures to form will be at posterior end

Question 16

Hypoblast

Answer 16

In avian: Forms from some cells delaminating from epiblast and cells migrating from Koller’s sickle across the blastocoel; will eventually form the yolk sac and such things

Question 17

Compare the types of gastrulation!***

Answer 17

Sea urchin: basically forms a straight tube; amphib: involution forms archenteron, displaces blastocoel; avian: forms primitive streak by involution; all form mesoderm.

Question 18

Mammalian gastrulation

Answer 18

Similar to avian, primitive streak forms (posterior); differences: invade uterus; placenta forms

Question 19

Amniotic fluid

Answer 19

Fluid which surrounds the developing embryo. Birds, reptiles and mammals.

Question 20

4 main membranes in amniotes

Answer 20

Amniotic membrane: around embryo, provides support; chorion: gas exchange, barrier to pathogens; yolk sac: nutrition source for reptiles and birds; allantois: some gas exchange, collects waste``

Question 21

Formation of placenta (in mammals)

Answer 21

Trophoblasts form synctiotrophoblasts; invade tissue layers of uterus; secretions; membranes of aminotes begin (~day 9); no yolk in yolk sac; allantois not needed in mammal; trophoblastic lacunae are future sites of material exchange (mother’s blood); placenta functional by 3 weeks

Question 22

hCG

Answer 22

human chorionic gonadotropin, released by synctiotrophoblasts; essential to pregnancy to maintain the corpus luteum so the uterine lining is maintained. This is tested for in pregnancy tests (antibodies)

Question 23

sommatomammotropin

Answer 23

hormone from synctiotrophoblast that stimulates breasts to grow so they can produce milk

Question 24

Roles of trophoblast cells

Answer 24

many divide and fuse (multi nuclear - “synctiotrophoblast”); invade tissue layers of uterus; secrete hCG, sommatomammotropin, implantation enzymes, IDO