Early Embryonic Development Flashcards
Trace the development from zygote through gastrulation.
1. Zygote- single cell
1+2= Cleavage occurs resulting in cells called blastomeres.
2. Morula- compact mass of cells. cells grow from 16-32. final stage of clevage.
3= Blastulation
3. Blastula- cavity begins to form. (trophoblast/embryoblast). early stage= no change in size. compaction forms bastula. hatches from zone pellucida.
late stage= expands to become fluid-filled cyst with peripheral cells= Blastocyst (has Ec,Tc, Bc)
4 + 5= Gastrulation
4. Early Gastrula- bilaminar disk
5. Late Gastrula- trilaminar disk to tube shape. 3 germ layers and primative axial organs (neural tube, notochord, somites and gut)
6. Body Folding= embryo
male and female pronuclei
male and female pronuclei= the genetic components of male and female gametes that combine within fertilized egg to produce embryonic DNA.
Clevage
Clevage= process by which zygote becomes morula
- Zygote- single cell. clevage into multiple cells (each called a blastomere).
- Morula- final stage of clevage! grows from 16 to 32 cells!
Blastulation
Blastulation= compaction and organization of cells into blastocyst
- Blastogenesis= blastocyst formation…
- early blastula=cavity begins to form
- within zona pellucida
- no change in size!
- compaction
- trophoblast and embryoblast present
- late blastula=expanded blastocyst!
- “hatch” from zone pellucida
- distinct layers! (EC,TC,BC)
Blastocyst: structure
The Blastocyst is the product of blastulation
Clear organization of blastocyst (see diagram)
-
Trophoblast cells= outer cell mass
- give rise to fetal placental membrane
-
Embryoblast cells= inner cell mass
- give rise to ALL cells of embryo
- organized in bilaminar disc of epiblast and hypoblast
- establishes dorsal/ventral axis
*** this is where gastrulation starts now…
Gastrulation
Gastrulation= formation of three germ layers and primative stuff
Early Gastrulation
- begins with formation of primative streak in epiblast
- estiblished cranial/caudal axis
- epiblast cells migrate towart primative streak and begin to form Ectoderm
- hypoblast cells form Endoderm
- epiblast cells and hypoblast cells migrating from primatave streak form the Mesoderm
Late Gastrulation
- formation of neural tube, notochord, somites, and primative gut by derivation of germ layers…
Define and give some derivative examples of ectoderm, mesoderm, endoderm.
In late gastrulation and body folding, germ layers give rise to primative structures in the embryo!
Ectoderm- makes epidermal structures, nervous tissue, and neural crest cells
- Origin: Epiblast
Mesoderm- CT, muscle, endothelium, mesothelium, urogenital system, cardiovascular system
- Origin: Epiblast cells that migrated to primative streak
Endoderm-epithelium of digestive and respitory systems
- Origin: Hypoblast (aka endoblast)
***** note that all three layers give rise to epithelium!
Divisions of the mesoderm
Divisions of Mesoderm
Note: mesoderm in different locations on embryo differentiates to form different structures.
- Axial: notochord
- Paraxial: somites
- Intermediate:
- Genital systems
- Urinary systems
- Lateral plate: somatic and splanchnic mesoderms
List the derivatives of a somite.
List the derivatives of a somite.
**Note: somites develop from paraxial mesoderm
Somites: division of animals body that give rise to muscle, cartilage, tendons, dermis (limbs/vertebrae)
Dermatome- dermis
Myotome- muscle
Sclerotome- cartilage, tendons, endothelia
Briefly Explain: pluripotent, totipotent, unipotent, migration, differentiation
Embryonic Cells
Totipotent:cells that can differentiate into any other cells.
Pluripotent: can differentiate into many types of cells, but not all types of cells.
Unipotent: cells that can only give rise to the same type of cells.
Migration: movement of newly generated cells to final destination
Differentiation: cells specialize and diverse tissue structures arise
Neural Crest Cells
Nerual Crest Cells= transient, multipotent, migratory cells
- Origin: ectoderm (transformation induced by mesoderm)
- Unique to vertebrates!!!
- produces diverse cell lineage:
- melanocytes
- craniofacial cartialge and bone
List some common developmental anomalies and teratogens.
Developmental Anomalies:
- Spina Bifida
- Hydrocephalus
- Cleft Palate
Teratogens:
- Radiation
- Chemical Agents
- nicotine
- alcohol
- Infectious Agents
- viruses
- parasites
*
Teratogen
Teratogen: any agent or factor that can result in congenital anomalies in an embryo.
Teratogenic influences on development:
at predifferentiation stage
during organogenesis stage
during fetal growth stage
Teratogenic influences on development:
at predifferentiation stage—Embryo Dies
during organogenesis stage—Structural Defects
during fetal growth stage—Affects Functional Maturation
