zoo 470 final exam flashcards (vocab)

unit 13-16

Deep cells

Inner layer of cells in blastula, located beneath epiblast/animal cap

superficial cells

outermost layer of blastula, part of epiblast and covers the embryo in thin epithelial layer 

marginal zone

region of blastula located between the animal pole and the vegetal pole

blastocoel(amphibians)

fluid filled cavity that forms inside the blastula during the early stages of development 

Blastopore

 opening that forms on surface of embryo, marks the beginning of gastrulation

blastopore closure

final stage of gastrulation, cells migrate inward and closes the opening 

yolk plug

small patch of endodermal cells that remain visible at center of blastopore during later stages of frog gastrulation

animal cap

group of cells located at the animal pole of the frog blastula, made up of superficial ectodermal cells, gives rise to skin and nervous system

epiboly

sheets of ectodermal cells (especially from animal cap) spread and thin out to cover entire embryo

bottle cells

 specialized cells that play a crucial role in initiating frog gastrulation by helping to form the blastopore

Invagination

a region of the epithelial layer (usually the marginal zone) folds inward to form an indentation/pocket

apical constriction

cellular process where the top surface of the cell becomes narrower relative to the bottom surface

involuting marginal zone(IMZ):

are of frog embryo marginal zone in which cells move inward during gastrulation through the process of involution

non-involuting marginal zone(NIMZ)

region of frog embryo marginal zone that does not undergo involution 

convergent extension

 vital for shaping the frog embryo, tissue narrows along one axis while simultaneously elongating along a perpendicular axis

planar cell polarity (PCP)

 cellular mechanism that coordinates the orientation of cells along the tissue’s surface, typically along anterior-posterior axis

leading edge mesoderm

located at dorsal lip of blastopore and extends out towards the anterior of embryo, important for involuting movements, contributes to notochord formation

Fibronectin

glycoprotein found in the extracellular matrix,plays key role in cell adhesion, migration, and tissue organization 

integrin

transmembrane receptors that mediate the connection between cells and the extracellular matrix. 

vegetal endoderm

endodermal cells located at vegetal pole (area opposite of animal pole), forms the archenteron through involution

Blastodisc

disc-shaped structure that forms on the surface of the yolk in birds and zebrafish

embryonic shield

 forms on dorsal side of blastodisc in both zebrafish and birds. Acts as organizer for dorsal-ventral axis in zebrafish, in birds it is the region where the primitive streak begins to form 

Hypoblast

Found beneath epiblast with the blastodisc in birds, contributes to formation of yolk sac, does not directly contribute to the embryo proper. In mammals it is part of the inner cell mass of the blastocyst ,also contributes to formation of yolk sac and contributes towards embryo proper. 

enveloping layer

layer of cells in the early zebrafish embryo that forms the outermost layser of embryo, is part of epiblast

B-catenin

crucial protein that plays an essential role in both cell-cell adhesion and intracellular signalling during embryonic development and tissue formation

Bone Morphogenetic Proteins(BMPs)

group of signalling molecules that belong to the TGF-𝛃 superfamily. Critical in regulating axis formation,patterning, cell differentiation, and tissue morphogenesis 

Chordin

secreted protein and a key BMP antagonist, crucial to development of dorsal-ventral axis 

Planar cell polarity (PCP) signaling

regulates the orientation and polarization of cells within the plane of a tissue instead of along apical-basal axis 

Wnt

(frizzled receptors, 𝛃-catenin pathway) a key morphogen. In zebrafish it helps specify dorsal identity, in birds it is critical for primitive streak formation and posterior axis initiation

Cadherins(birds/reptiles)

family of calcium dependent cell adhesion molecules, in zebrafish they help form the organizer and coordinate cell movement during axis formation. In birds they regulate primitive streak formation and vital for axis specification 

Involution

cells move inward and spread along inner surface of the embryo, cells move from embryonic shield to form mesoderm in zebrafish, cells ingress at primitive streak and move to form inner layers 

convergent extension

cells move towards midline and extend. In zebrafish cells move towards midline and intercalate to lengthen the axis, in birds a similar thing happens but drives the elongation of the primitive streak and body.

Amniote

group of vertebrates (birds,reptiles, mammals) 

amniotic egg

 crucial for terrestrial life in amniotes, has a series of specialized membranes to support and protect the embryo allowing it survive out of water

Epiblast (Birds/reptiles)

the outermost layer of cells in early embryos and located just above the hypoblast. Forms the embryonic disc.

subgerminal space

a fluid filled cavity found beneath the germ layers and under the epiblast, forms area between epiblast and hypoblast, especially prominent in avian embryos 

area pellucida

clear/translucent region of the embryonic disc, central part of the blastoderm, is where gastrulation begins and where the primitive streak forms

area opaca

darker region of the blastoderm, located on the outer edge of blastoderm, contributes to the formation of the chorion and trophoblast (mammals)

Kohler’s sickle

 thickening of cells located in the posterior part of epiblast just before formation of primitive streak. Important in induction of primitive defines the site of gastrulation

posterior marginal zone(PMZ)

narrow band of cells located at the posterior edge of the blastoderm adjacent to area opaca. Ensures that primitive streak forms at the correct location and that body axes are correctly specified

Hypoblast

layer of cells that forms on the ventral side of epiblast, located beneath epiblast and above the yolk in birds and reptiles, above the extra embryonic membranes in mammals. It is temporary and does not give rise to cells in the embryo proper, but essential for organization.

definitive endoderm

 key layer in gastrulation process, responsible for generating many essential organs. Derived from epiblast cells in both birds and mammals, becomes the endodermal layer in birds, transitioned from primitive endoderm in mammals 

primitive groove

linear depression that forms along the midline of the primitive streak during gastrulation 

Primitive streak

forms along the dorsal surface of the embryo at the posterior end of the epiblast, serves as signalling center and foundation for establishing body axes 

Henson’s node

located at anterior end of primitive streak and marks future head of embryo

notochordal (head) process

forms from Henson’s node, central role in the formation of the notochord 

Totipotency

a single cell that can give rise to all cell types, found in the earliest stages of mammalian development (zygote and early blastomeres)

Pluripotency

a single that can give rise into ectoderm,mesoderm, and endoderm, but not extra embryonic tissues like placenta. Found in the inner cell mass of the blastocyst in mammals 

Compaction

 occurs during 8-cell stage, blastomeres increase surface contact with each other through tight junction formation and increased cell adhesion, usually mediated by proteins like E-cadherin

Cadherin

calcium dependent adhesion molecule, vital at 8-cell stage as it holds blastomeres together, establishes cell polarity, and supports the formation of the blastocyst

Blastocyst

key stage in early mammalian embryonic development, consists of trophectoderm,inner cell mass, and blastocoel. Marks first morphological differentiation and critical for axis specification 

Blastocoel (mammals)

a fluid filled cavity that forms inside the blastocyst

inner cell mass

 a cluster of pluripotent cells inside the blastocyst that will give rise to the embryo proper (mesoderm,endoderm, ectoderm)

Trophoblast

outer layer of cells of the blastocyst originating from the trophectoderm, forms during compaction. Forms extra embryonic tissues (primarily placenta)

Monozygotic twinning

a single zygote splits into two embryos, they share the same genetic material and are always the same sex.

Trophectoderm

outer layer of cells in the blastocyst that surrounds the inner cell mass and the blastocoel, gives rise to the trophoblast 

primitive (visceral) endoderm

 also known as hypoblast, one of the two cell lineages that arise from the inner cell mass. Forms a layer of cells lining the blastocoel beneath the epiblast, contributing extra embryonic tissues including yolk sac.

Epiblast (mammals)

one of the two cell lineages that arise from the inner cell mass. Upper layer of the inner cell mass and lies above the primitive endoderm. Gives rise to the embryo proper (pluripotent) 

Cytotrophoblast

inner layer of the trophoblast and composed of mononucleated cells. Critical for early stages of implantation and the formation of placenta

Syncytiotrophoblast

outermost layer of the trophoblast and is a multinucleated structure (many nuclei with a single cytoplasmic mass). Facilitates the embryo's attachment to the uterine wall and allows for formation of placenta.  

Oct-4

transcription factor that is critical for maintaining pluripotency in mammalian embryos. Primarily expressed in the inner cell mass and important for identifying pluripotent stem cells 

Cdx2

transcription factor that is critical for the formation of the trophectoderm and differentiation of extra embryonic tissues

Nanog

transcription factor that is critical for maintaining pluripotency in mammalian embryos. Primarily expressed in the inner cell mass and important for identifying pluripotent stem cells, down regulation of this factor triggers differentiation into embryo proper

Gata6

transcription factor that is critical for the formation of the primitive endoderm (hypoblast), highly expressed within the inner cell mass and helps establish extra embryonic tissues 

Tead4

a transcription factor that regulates the formation of trophectoderm and the inner cell mass, highly expressed in trophectoderm and ensures proper segregation of trophectoderm.

Lats(large tumor Suppressor)

 a protein kinase that is a key component of the Hippo signalling pathway by inactivating YAP/TAZ transcriptional co-activators, this helps ensure tissues grow to the appropriate sizes. 

Hippo

Pathway that regulates cell growth, proliferation, and apoptosis. When inactive it allows YAP/TAZ to enter cells and promote cell growth, when active it inhibits YAP/TAZ, reducing cell growth. 

The Node

 small specialized group of cells at the posterior tip of the primitive streak during gastrulation, secretes noggin,chordin,follistatin which antagonizes BMP, crucial for establishing dorsal side of embryo. Also contributes towards formation of notochord

anterior visceral endoderm (AVE)

 positioned at the future head region of the developing embryo, secretes cerberus, lefty, and dickopf which inhibits the Wnt and Nodal signalling pathways. This directs formation of anterior structures of the embryo.

Situs solitus

correct left-right patterning during embryonic development. Involves asymmetric placement of organs (heart,stomach, spleen on the left) (liver on the right) (lungs asymmetric, 3 lobes on right, 2 lobes on left) 

situs inversus totalis

reversal of normal left-right patterning during embryonic development. (heart,stomach,spleen on right) (liver on left) (lungs have 3 lobes on left, 2 lobes on right)

Heterotaxy

 also called situs ambiguus, abnormal arrangement of internal organs along the left-right axis.

Primary cilia

hairlike projections found of the surface of nearly all vertebrate cells, senses and transducts extracellular signals 

Kartagener’s triad

 the main features seen in individuals with primary ciliary dyskinesia (PCD).

Chronic sinusitis: persistent inflammation of sinuses

Bronchiectasis: chronic dilation and damage of bronchi 

Situs inversus: reversal of normal left-right positioning of internal organs 

primary ciliary dyskinesia

rare inherited disorder which causes structural and functional issues within motile cilia 

intraflagellar transport(IFT)

 the transport of protein complexes along the axoneme

Kupffer’s vesicle

a transient cilliated structure found in zebrafish and is the functional equivalent of the embryonic node in mammals. Establishes L-R asymmetry in fish embryos, located at the posterior end of the nototchord 

gastrocoel roof plate(GRP)

cilliated epithelial structure in early amphibian embryos, functional equivalent of embryonic node in mammals and kupffer’s vesicle in fish. Forms on dorsal roof of the gastrocoel during gastrulation 

nodal cilia

specialized motile cilia found on the cells of the embryonic node (aka. organizer) in developing vertebrate embryos

nodal vesicular parcels

 small vesicles found in embryonic node (or in similar structures like Kupffer’s vesicle) that are involved in the generation and transport of signalling molecules during left-right axis specification 

Pitx2

 transcription factor that is asymmetrically expressed on the left side of the embryo during left-right axis patterning. Ensures correct heart looping, lung lobe formation, gut coiling and is activated by nodal. 

Nodal

 secreted signaling molecule from TGF-ꞵ superfamily, expressed on the left side of the developing embryo during left-right axis patterning.Suppressed by dand5 on right side of body, if not it leads to ambiguus (abnormal organ placement) 

Lefty

secreted signaling protein, expressed on left side of embryo and acts as an inhibitor of Nodal by binding to receptors, usually expressed in lateral plate mesoderm. Acts later in L-R patterning

Dand5

secreted signalling protein, directly inhibits nodal by binding to receptors, usually expressed in the embryonic node. Acts in early stages of L-R patterning 

Ontology

the philosophical study of existence and being (ex: when does an embryo become a person?) 

Deontological ethics

 a moral theory that emphasizes the importance of following rules and obligations in determining whether an action is morally right regardless of consequences (duty-based ethics). 

consequentialist ethics

morality of an action is determined by its outcomes, an action is morally right if it leads to the best possible outcome. 

Utilitarianism

form of consequentialist ethics, the morally right action is the one that produces the greatest net benefit for everyone affected by the action 

Intuitionism

 ethical theory that moral truths are known intuitively without need for reasoning and/or empirical evidence 

Preimplantation genetic diagnosis (PGD)

technique used to test embryos for specific genetic conditions before they are implanted in the uterus during IVF.

Amniocentesis

medical procedure used to collect a small sample of amniotic fluid during pregnancy, typical performed when there is a concern about the health of the fetus or if certain risk factors are present

chorionic villus biopsy

takes small sample of tissue from the chorion (outer layer of the placenta) to analyze the fetus’s genetic material. Can identify things such as down syndrome, cystic fibrosis and Tay-Sachs disease. 

polar body biopsy

examines the polar bodies (which are byproducts of oocyte maturation) and indirectly gather genetic info on the egg (if polar body as abnormal gene, egg probably doesn't) 

Sex selection

the practice of choosing the sex of the offspring before/during conception. The most accurate method being preimplantation diagnosis (PGD)

Down syndrome (trisomy 21)

occurs when there is a third copy of chromosome 21, most common form of down syndrome making up of roughly 95% of cases in which all cells that an extra chromosome 21

Synthetic embryo

artificially made embryos that are created using stem cells or other cellular components to mimic some or all of the early developmental stages of an embryo. 

14-day rule

 proposed in the 1979 warnock report, was considered the point at which the primitive streak begins to form which is a precursor to the nervous system. Before this point the embryo is considered an undifferentiated mass of cells and allows for testing/research without most ethical concerns. 

Neurulation

embryonic process in which the neural tube is formed from the neural ectoderm

phylotypic stage

 the part of embryonic development in which embryos of different species from the same phylum look similar to each other, usually after neurulation in vertebrates 

neural crest

group of cells derived from the edges of the neural plate during neurulation and is made of multipotent cells