[DEVBIO] LECTURE 08 GERM LAYERS AND NEURAL CREST CELLS

Germ layers

The three primary layers of cells that form during embryonic development - endoderm, mesoderm, and ectoderm.

Epiblast

The upper layer of cells in the blastocyst that gives rise to the embryonic epiblast and amniotic ectoderm.

Hypoblast

The lower layer of cells in the blastocyst that gives rise to the extraembryonic endoderm, forming the yolk sac.

Blastocyst

A structure composed of two cell populations - the inner cell mass (ICM) and the trophectoderm - that develops during early embryonic development.

hypoblast

part of the ICM that will give rise to extraembryonic endoderm, forming the yolk sac

epiblast

part of the ICM that will split and delaminate into embryonic epiblast and amniotic ectoderm

bilaminar disc , trilaminar disc

Formation of epiblast and hypoblast is called the [] formation

Formation of the three germ layers is called the []formation

Embryonic endoderm
Embryonic mesoderm

Notochordal process at the midline

Morphogenetic movements of the cell passing through the PS forms the ff [],[],and []

Trophoblast

The outer layer of cells in the blastocyst that gives rise to the cytotrophoblast and syncytiotrophoblast, which play a role in implantation and placenta formation.

Inner cell mass (ICM)

The group of cells within the blastocyst that will develop into the embryo.

Cytotrophoblast

The layer of trophoblast responsible for the initial attachment of the blastocyst to the uterine lining.

Syncytiotrophoblast

The layer of trophoblast that has lost cellular membranes and forms a continuous layer, secreting enzymes for implantation and contributing to placenta formation.

Yolk sac

A structure derived from the hypoblast that plays a role in early embryonic nutrition and blood cell formation.

Notochord

A rod-like structure derived from mesodermal cells that plays a role in axial skeleton development.

Mesoderm

One of the three germ layers that gives rise to various tissues and organs, including muscle, bone, and connective tissue.

Ectoderm

One of the three germ layers that gives rise to the skin, nervous system, and other external structures.

Endoderm

One of the three germ layers that gives rise to the lining of the digestive tract and other internal organs.

Somites

Segmented blocks of mesoderm that give rise to the vertebrae, muscles, and other structures along the body axis.

Oropharyngeal, primitive streak, primitive node

[] membrane is forming anteriorly

Epiblast layer is where the [] is forming

[] site of invaginating cell

ectoderm

mesoderm

endoderm

those on top will form the =

the ingressing cells =

the cells displacing the hypoblast =

3 1 4 2

arrange the steps of the formation of NOTOCHORD
[ ] Migrating prenotochordal cells become intercalated in the endoderm to form the notochordal plate

[ ] Definitive notochord is formed at the cephalic to caudal region

[ ] Intercalated notochordal plate will detach to form the definitive notochord

[ ] Prenotochordal cells migrate through the primitive pit of the PS moving cranially

Paraxial mesoderm

Intermediate mesoderm

Lateral plate mesoderm

the three [3] mesodermal sheet

hypomere

the mesoderm that extends further to the side and downward to form the lateral plate mesoderm

mesoderm

notochord has [] blank at its sides

mesomere

Between the paraxial and lateral plate mesoderm is the intermediate mesoderm called

Embryonal coelom

[] is formed when two lateral plate mesoderms split.

somites

Paraxial mesoderm gives rise to [ ].

urogenital units, components of the reproductive system and the excretory system

Intermediate mesoderm gives rise to different .

somatic and splachnic mesoderm

Lateral Plate Mesoderm split into [] and []

Epithelialization

The process by which embryonic cells transform into flat, tightly packed cells.

Mesenchymal

Referring to cells that have lost their epithelial arrangement and have become more loosely arranged and migratory.

Dorsomedial cells and Ventrolateral cells

Cells that will form the myotome.

Dermatome

Cells that remain between dorsomedial and ventrolateral cells and will form the outermost layer of the somite.

Somite

Structure composed of three layers - sclerotome, myotome, and dermatome.

Sclerotome

Innermost layer of the somite that forms the vertebrae.

Myotome

Middle layer of the somite that surrounds the neural tube and notochord and gives rise to muscles.

Dermamyotome

Cells that will give rise to the dermis and muscles.

Sonic Hedgehog (SHH)

Gene expressed by the notochord and floor plate of the neural tube that helps form the sclerotome.

Noggin

Gene expressed by the notochord and floor plate of the neural tube that helps form the sclerotome.

PAX1

Gene expressed by the sclerotome that controls chondrogenesis and vertebrae formation.

WNT proteins

Proteins secreted by the dorsal neural tube that activate PAX3 and demarcate the dermamyotome.

MYF5

Muscle-specific gene expressed by muscle cell precursors.

NT3

Gene expressed by the dorsal neural tube that helps form the dermis.

BMP4

Protein that, along with WNT protein, activates MyoD expression.

Endoderm

Innermost layer of the embryo that forms the digestive gut, liver, gallbladder, pancreas, stomach, intestine, and pharyngeal pouches.

Vitelline duct

Connection between the midgut and yolk sac that houses the vitelline blood vessel.

○ Heart ○ Septum transversum ○ Yolk sac and amnion

Midsagittal sections of embryos at various stages of development showing: cephalocaudal folding and its ef fects upon position of the [] [] and []

Mesonephros

Region that arises from the intermediate mesoderm and gives rise to the lining of the body cavity and various visceral organs.

Somatic/parietal mesoderm

Layer of the lateral plate mesoderm that forms the lining of the body cavity and body mesenteries.

Splanchnic/visceral mesoderm

Layer of the lateral plate mesoderm that forms a layer around the visceral organs and gives rise to various visceral organs.

Intraembryonic cavity

Cavity formed when the parietal and visceral mesoderm split.

Digestive gut

[] running from the stomodeum down to the proctodeum (cloaca).

liver, gallbladder, and the pancreas.

Out pocketing of the digestive gut gives rise to the [] [] and []

allantois

Out pocketing of the hindgut is the []

pharyngeal pouches

pouches originating from the endodermal layer are the [].

pouch, slit, arch

Pharyngeal [] - lining of the foregut

Pharyngeal [] - comes from the outside are white fanning

Pharyngeal [] - bulges

Neural crest cells

Derivatives of the ectodermal layer that migrate from the brim of the neuroectoderm and give rise to various cell types in the embryonic body.

Pluripotent cells

NCC are [ ] meaning they are cells capable of giving rise to various cell types in the embryonic body.

Mesenchymal cells

Loosely arranged cells with amoeboid movement, characteristic of neural crest cells.

Epithelial-mesenchymal transition

Transition from epithelial to mesenchymal type and vice versa that neural crest cells undergo as they give rise to different cell types in the embryonic body.

Cranial neural crest cells

Neural crest cells that migrate to the cranial region and give rise to components of the face and neck, pigment cells of the skin, adrenal medulla, and sensory ganglia.

Lateral migration pathway

Route taken by neural crest cells that gives rise to melanocytes.

Medial migration pathway

Route taken by neural crest cells that gives rise to ganglia, including dorsal root and sympathetic ganglia.

Microenvironment

The final destination where neural crest cells settle and undergo final differentiation via cell-to-cell signaling.

Anterior sclerotome

Part of the somite that contains neural crest cells and participates in the formation of cartilages and bones of the vertebral column.

Posterior sclerotome

Part of the somite that does not contain neural crest cells and is concentrated on the anterior sclerotome.

Cranial, cardiac, vagal, and lumbosacral domains where neural crest cells settle and give rise to various structures in the body.

what are the four overlapping domains

Cardiac neural crest cells

Neural crest cells that contribute to the septum between the pulmonary arch and aortic arch and the endothelium of aortic arch arteries.

Dorsolateral pathway

Route taken by neural crest cells that gives rise to melanocytes, neurons, cartilages, connective tissues, and other structures.

Ventral pathway

Route taken by neural crest cells that gives rise to dorsal root ganglia, sympathetic ganglia, parasympathetic ganglia, schwann cells, and adrenal medulla.

Cranial NCC

Neural crest cells that migrate to form structures in the pharyngeal arches, face, and neck.

Cardiac NCC

Neural crest cells that migrate to form the septum between the pharyngeal arches and aorta in the developing embryonic heart.

Trunk NCC

Neural crest cells that migrate to form sympathetic neurons.

Vagal NCC

Neural crest cells that migrate to form parasympathetic nerves of the gut.

Sacral NCC

Neural crest cells that migrate to form parasympathetic nerves of the gut posterior to somite 28.

Neural tube

The structure from which neural crest cells originate.

BMPs

Signaling molecules that influence the fate of embryonic ectoderm, with different concentration levels inducing epidermis formation, neural crest cell formation, or neural ectoderm formation.

Fibroblast Growth Factors (FGF)

Interplay with intermediate concentration of BMPs to induce the specification of neural plate border cells as neural crest cells.

SLUG

Transcription factor that promotes the migration of neural crest cells from the neuroectoderm.

N-cadherin

Cell adhesion molecule that, when lost, allows neural crest cells to undergo amoeboid migratory movement.

Extracellular matrix (ECM) proteins

Control the path of neural crest cell migration, with some promoting migration and others restricting migration.

Chemotactic factors

Soluble factors secreted by potential destinations that allow continuous proliferation of neural crest cells and influence their final differentiation.

TGF-β superfamily

Cell signaling factors that determine the final differentiation of trunk neural crest cells.

Hox genes

A subclass of highly conserved homeobox-containing genes that specify the general body plan of an animal and convey positional information.

Germ layers

The three primary layers of cells in the early embryo, including the ectoderm, mesoderm, and endoderm.