Devo Lect 7 - Gastrulation Flashcards Preview

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Flashcards in Devo Lect 7 - Gastrulation Deck (23):
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Gastrulation definition*

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

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Basic body plan

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

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Invagination

Folding in of a layer

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Involution

Layers of cells migrating inwards

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Ingression

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

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Delamination

Separate one layer into two

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Epiboly

A layer envelopes another

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Sea urchin gastrulation

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

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Archenteron

Name of the tube (means “primitive gut”)

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2˚ mesenchyme cells

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

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Protostome and Deuterostome

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

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Amphibian gastrulation

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

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Yolk Plug

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

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Avian gastrulation

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

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Hypoblast

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

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Compare the types of gastrulation!***

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

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Mammalian gastrulation

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

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Amniotic fluid

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

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4 main membranes in amniotes

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``

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Formation of placenta (in mammals)

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

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hCG

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)

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sommatomammotropin

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

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Roles of trophoblast cells

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