Lecture 10: Early Embryonic Development Flashcards
Terratogen
Any agent or factor that can cause congenital abnormalities in an embryo or fetus
5 common terratogens
- Genetic factors
- Radiation
- Hormones
- Chemical agents
- Infectious agents
Teratogenic influence at predifferentiation stage
Embryo dies
Teratogenic influence at organogenesis stage
Structural defects (embryonic period)
Teratogenic influence at fetal growth stage
Affects functional maturation
Single cell
zygote
Compact mass of cells
Morula
Fluid filled cyst with cells at periphery
Blastula
`Bilaminar disc
early gastrula
Trilaminar disc to tube shape
late gastrula
Zygote
- Large (160 um)
- Divisions occur in uterine tube, resulting in blastomeres
Is there an increase in size during blastogenesis?
No. Compaction occurs as the cell divides.
No increase in overall size o embryo while inside zone of pellucida
Trophoblasts will form
part of placental membranes
Embryoblasts will form
- the entire embryo
- forms the bilaminar disc of the epiblast and hypoblast
- establishes dorsal and ventral axis
Epiblasts give rise to
Ectoderm
Hypoblast gives rise to
Endoderm
Ectoderm gives rise to
Epithelium
Nervous tissue
Neural crest cells
Endoderm
Epithelium of digestive and respiratory systems
Mesoderm gives rise to
Connective tissues Muscle tissues Cardiovascular system Urogenital tract Endothelium Mesothelium
What layers is the epithelium derived
All three (ecto, meso, and endoderm)
Gastrulation is a formation of
a three layered embryo
Gastrulation begins with
the formation of the primitive streak in the epiblast.
Cranial-caudal axis established
How is the primitive streak formed?
- Epiblast cell migrate towards primitive streak and form the ectoderm
- Hypoblast/endoblast cells replaced to form the primary endoderm
- Mesoderm is also formed from cells migrating from the primitive streak
Notochord
Cluster of cells derived from the mesoderm, determines axis of embryo and required to signal neural tube formation.
Transient embryonic midline structure in vertebrates
6 Mesoderm inductive effects
- Forms notochord
- Notochord induces ectoderm to form neural tissue
- Neural tube and neural crest cells formed
- Some somites seen
- Lateral, cranial, caudal body folds create the head, tail, primitive anus and mouth
- Nervous system defined
Where is the presumptive notochord located
in or above the endoderm but of mesodermal origin
4 steps of neural tube formation
- Neural ectoderm thickens
- Neural folds dip down, producing the neural groove
- Neural folds contact, neural ectoderm cells rearrange
- The neural tube is formed
Axial mesoderm gives rise to
Notochord
Paraxial mesoderm gives rise to
Somites
Intermediate mesoderm gives rise to
Genital systems
Urinary system
Lateral plate mesoderm gives rise to
Somatic and splanchnic mesoderms
Somites
Division of animals body giving rise to muscle, cartilage, tendons, dermis (limbs, vertebrae)
Three somites
Dermatome - dermis
Myotome - muscle
Schlerotome -cartilage, tendons, endothelia
Cranial part of neural tube
brain
Caudal part of neural tube
spinal cord
Neural crest cells
Transient, multipotent migratory cell population unique to vertebrates that gives rise to a diverse cell lineage, including melanocytes, craniofacial cartilage, and bone
