ANS 123 Exam 2

Karyogamy

fusion of ovum and sperm (pro-nuclei)

Germ layers

Ectoderm, Mesoderm, Endoderm

Pre-natal

Before birth

Peri-natal

Around birth

Post-natal

After birth

Neo-natal

Newly born

Totipotency

Ability to express ALL the genes in the organism's genome; "all the things"

Pluripotency

Ability to express genes that code for germ layers; "all three layers"

Multipotency

Ability to express genes that code for closely related family of cells (Progenitor cells); 1 derivative of 1 germ layer

Unipotency

Ability to undergo a limited number of divisions and express genes that produce SINGLE type of cell (Precursor cells); 1 kind of functional specialized cell

True stem cells include...

Totipotent cells and pluripotent

Morphpgenesis

generation, differentiation, and growth of tissues and organs during development; where organism takes shape

Morphogenesis covers

cleavage, layer formation, gastrulation, neurulation, organogenesis

T/F Morphogenesis happens post-fetilization

True

Delamination

splitting single sheet of cells by loss of adhesion

Delamination Example

Hypoblast formation

Ingression

Division and migration of cells into internal area to form a separate layer

Ingression Example

Internal cell mass (ICM) and trophoblast separation

Invagination

Depression in the cell layer depends due to cell vision; sides come together and pinch off existing layer

Invagination Example

Neural tube formation

Epiboly

Increase in \# of cells on outer surface

Epiboly Example

Primitive streak formation

Involution

Inward rolling of cells along an exiting membrane to create layer

Involution Example

Myeline sheath formation

Fertilization

Fusion of female and male gametes to achieve karyogamy; female part is the ovum and the male gamete is the sperm

T/F Female birds and mammals can produce an infinite number of ova during their lifetime

False; birds and mammals have \# ova set peri-natally

Cleavage Functions

1) Increase \# cells via mitosis without growth 2) Establish embryonic vs. extraembryonic cell line

Cleavage Result Avian vs. Mammalian

Avian: blastoderm vs. Mammalian: blastocysts; ends when blastocyst makes contact with uterine wall

Meroblastic

Yolk does not get cleaved; avian

Discoidal

Cells clump together into a disc-shape; avian

Open cell

Cytoplasm mixes with yolk; avian

T/D After 1-16 divisions daughter cells form a complete cell membrane (Avian)

False; open cells

Blastomere (Avian)

closed cell membrane and 16 divisions; not identical

Blastoderm (Avian)

Most central are closed cells (embryo only) and open cells beneath and around embryo

Doral-ventral axis (Avian)

Dorsal \= egg shell side Ventral \= Yolk side

Anterior-Posterior axis Avian)

Egg rotates in shell gland "heavy" blastoderm tilts away from top of yolk; lower end of blastoderm \= anterior and upper end \= posterior

Two cell lineages of blastoderm (Avian)

Closed cell and Open cells

Avian cleavage overview

1) Increase number of cells thu cell division 2) Establish embryonic vs. extraembryonic cell lines 3) Establish axes of polarity

Holoblastic

Extends completely through ovum; Mammalian

Rotational

Division occurs along different cleavage planes; Mammalian

T/F Cleavage occurs asynchronously to reposition cells with reference to one another

True; Mammalian

Compaction

cells become tightly joinged

Cavitation

Formation of fluid filled cavity

3rd Cleavage; Mammalian

Cells squish and form tight junctions to seal off the interior

Inner cell mass (ICM)

small group of completely enclosed cells within interior (embryo proper)

Trophectoferm

external cells form epithelial-like layer (placenta); form tight junctions and fill morula with water

Compacted mrula

Has ICM and Trophectoderm; at 8-32 cells

Mammalian cleavage overview

1) Increase number of cells thu cell division 2) Establish embryonic vs. extraembryonic cells lines 3)

T/F ICM cells undergo apoptosis and cells bunch along one side

True, then forms blastocoel

Blastoceol

Resulting fluid filled cavity; from ICM

2 Blastocyst lineages (Mammalian)

ICM and Trophectoderm

Layer Formation

irreversible physical segregation of cell lineages to form Hypoblast; prior to oviposition/implantation (visceral endoderm in rodents)

T/F Hypoblast is called "viseral endoderm" in rodents

True

T/F Oviposition refers to Mammals

False, refers to avain

T/F Implantation refers to Mammals

True, refers to mammals

Setting up for layer separation; avian

1) Blastoderm undergoes reduction via cell shedding 2) Fluid filled subgerminal cavity

1) Blastoderm undergoes reduction via cell shedding; Avian

Blastoderm undergoes reduction via cell shedding

T/F Delaminated cells undergo apoptosis

True

2) Fluid Filled subgerminal cavity forms; Avian

Blastoderm cell absorb water from albumen and pump between ventral surface and yolk (Similar to mammalian cavitation)

Area pellucida

Clear central area of clear cell undergoing rapid division, central blastoderm bull's eye; Avian

Area pellucida becomes...

embryo proper

Area opaca and marginal zone becomes...

Extraembryonic tissues and temporary embryonic structures

Area opaca

Area of open cells in contact with yolk outer ring; Avian

Marginal zone

Mixture of open and closed cells diving AP and AO middel ring; Avian

Epiblast

Continuous single-cell layer of AP+MZ+AO

Setting up for layer separation; mammalian

1) Cell determination and differentiation

Cell determination and differentiation; mammalian

Pluripotent ICM undergo determination; Epiblast & PE sifferentiation & seoarate layer, multipotent trophectoderm proliferate

ICM undergo determination into...

Epiblast progenitor cells and primitive endoderm progenitor cells (PE)

Separation of layers

Hypoblast is transitory stucture to prepare embryo for cellular complexity

T/F Separation of layers is well studied in birds and mammals

False, well studied in birds not so much mammals

Layer Formation (Avian)

AP epiblast cells delaminate and migrate toward yolk to become hypoblast cells; epiblast creates embryo and blastocoel cavity between epi- and hypoblast

Blastula

epiblast + hypoblast \= bilaminar

Hypoblast; Avian

Formed in subgerminal cavity below AP epiblast, gives rise to primordial germ cells; very transitory does not contribute

Elongation; Mammals

Epiblast forms amniotic cavity where proximal \= aminion and distal \= epiblast

Establish anterior-posterior axis; Mammals

Determination and differentiation PE cells split visceral endoderm/Hypoblast and Yolk sac endoderm; VE activated to distal VE

DVE (Distal Visceral endoderm); mammalian

Migrates up anterior side of blastocyst, becomes AVE

Blastula; mammalian

Epiblast and Hypoblast/VE \= bilaminar

End of layer formation

Avian and Mammalian have blastula

Gastrulation

cells differentiate and form lining of gut; starts posterior and goes anterior

Primitive streak

Site of ingression in epiblast; massive cell proliferation

How many phases does Gastrulation occur?

2, Ingression and Regression

Ingression

Primitive streak formation; first wave \= forming three germ cells form endo, meso, and endoderm; second wave \=

T/F: Changes during Ingression will set the stage for an additional layer to form

True

Koller's sickle; avian

Blastomere forming the vanguard of posterior marginal zone; crescent shape, crucial for primitive steak and enables endoblast to replace hypoblast

Endoblast; avian

Hypoblast replaced by sheet of endoblast cells; epiblast cells on Koller's sickle condense and begins gastrulation

T/F Endoblast is a permanent structure

False, it is a temporary stucture

T/F Epiblast cells below KS groove form primitive streak

False, cells above KS do this

Epiboly; avain

Primitive steak triggers epiboly across epiblast and mirgrate; replaced by future ectoderm cells

2 New layers in blastocoel; avian

Endoderm (replace endoblast) and Mesoderm (above endoderm)

Migrated cells become....(Avian)

Mesoderm, head process and notochord, and endoderm

Hensen's node

at anterior end, specialized thickened region in primitive streak (left and right fully determined)

T/F Epiboly gives rise to ectoderm in epiblast

True

Endoderm; mammals

is replaces the endoblast/hypoblast/all VE

Blastula is \____ and becomes gastrula \______

bilaminar, trilaminar

Regression

Primitive streak degeneration, Hensen's node moves posterior, neurulation

T/F as primitive streak regresses the notochord completes

True; concludes with formation of anal region

Nerulation

formation of spinal cord precursor from epiblast ectoderm

T/F Neurulation begins after gastrulation

False, Neurulation begins as primitive streak regresses during gastrulation

Neural tube

rudiment of CNS, formed first

Notochord

rod of mesoderm cells form under epiblast after Hensen's node moves; temporary structure and initials CNS formation