Early Embryonic Development (Exam II) Flashcards
Define Teratogen and give some examples.
Any agent or factor that can cause congenital abnormalities in an embryo or fetus.
Genetic factors, radiation, hormones, chemical agents, infectious agents (viruses, parasites)
Define Totipotent, Multipotent, Pluripotent, Unipotent
Totipotent - can differentiate into ANY type of cell
Multipotent/Pluripotent - can differentiate into a certain cells
Unipotent - Can differentiate into 1 type of cell
What happen when a teratogen acts during….
- Predifferentiation
- During Organogenesis
- During fetal growth stage
- Embryo dies.
- Structural defects.
- Affects functional maturation.
Describe the basic process of development from Ootid to gastrulation…
Ootid (female and male pronuclei) –> (Zygote (single cell) –> Morula (compact mass of cells) –> Blastula (fluid filled cyst with cells at periphery) –> Blastocyst (addition of inner cell mass (embryoblast)) –> Hatching Blastocyst (where zona pellucida breaks open) –> Early gastrula (Bilaminar disk) –> Late Gastrula (Trilaminar disk to tube shape)
Describe Cleavage
The zygote undergoes divisions in the uterine tube without any change in size. The resulting cells are Blastomeres.
What is a Morula
16 cells (blastomeres), zona pellucida is still intact.
What is a Blastocyst?
Stage where the cavity has formed (forms in blastula) and there is now an inner cell mass (embryoblast) and an outer cell mass (trophoblast). Still the same size as the zygote (results from cleavage) & compaction).
What is a gastrula?
Stage where there is the formation of the 3 germ layers (ectoderm, mesoderm, endoderm) and primitive axial organs (neural tube, notochord, somites, primitive gut)
What is the trophoblast? What does the trophoblast become?
Outer cell mass of blastula/blastocyst. Will form parts of the placental/fetal membrane (chorion, amnion)
What is the embryoblast? What does it become?
Inner cell mass of blastula/blastocyst. Will become the entire embryo. Forms the bilaminar disk of epiblast (dorsal) and hypoblast (ventral).
What does the primitive streak do?
Establishes the cranial/caudal (head/tail) axis.
What does the ectoderm form?
Epidermal structures, lining of oral and nasal cavity, anus, nervous system
What does the mesoderm form?
Connective tissue (of neural crest origin in head), muscle tissue, cardiovascular system, urogenital tract, endothelium and mesothelium (the linings of body cavities and vessels)
What does the endoderm form?
Epithelial structures, lining and glands of the digestive and respiratory systems
What is a Teratoma?
A neoplasm with more than one type of germ layer.
Describe the steps of Gastrulation
Primitive streak forms in epiblast –> epiblast cells migrate towards primitive streak –> hypoblast cells are replaced by epiblast cells to form primary endoderm, mesoderm formed by epiblast cells that descend through the primitive streak but do not replace the hypoblast cells, ectoderm formed by epiblast cells that do not descend through primitive streak
What lines the yolk sac?
Primary endoderm
What forms the notochord? What is the notochord?
Notochord is formed from mesoderm. It is a cluster of cells that determines the axis of embryo and is required to signal neural tube formation from the neural ectoderm. It is a transient embryonic midline structure that induces the lateral body folds, neural tube and primitive gut formation.
Describe the Mesoderm Inductive Effects..
Mesoderm forms notochord –> notochord induces the ectoderm to form neural tissue –> neural tube and neural crest cells are formed –> somites form
Lateral, cranial, caudal body fold create the head, tail, primitive anus and mouth. Nervous system is defined.
Describe the steps in Neural Tube Formation
Neural ectoderm thickens –> Neural folds dip down producing the neural groove –> Neural folds contact. Neural ectoderm cells rearrange –> Forms neural tube.
What are the 4 types of mesoderm (named for their location on transverse section of body)? What do they form?
- Axial - Notochord
- Paraxial - Somites
- Intermediate - Urogenital systems
- Lateral Plate - Somatic and Splanchnic mesoderm - becomes all other cartilage and bones of the body and limbs
What are the 3 regions that somites form? What do they give rise to?
- Dermatome - skin (dermis)
- Myotome - muscle (skeletal muscle)
- Sclerotome - cartilage, tendons, endothelium (forms axial skeleton)
What does the neural tube become?
The cranial part becomes the brain
The caudal part becomes the spinal cord
What does the notochord become?
The nucleus purposes of intervertebral discs.
What are 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
What does somatic mesoderm (division of lateral plate mesoderm) form?
forms most connective tissue and smooth muscle
What does sphlanchnic mesoderm (division of lateral plate mesoderm) form?
Forms most connective tissue and smooth muscles of endoderm lined organs and epithelial linings of body coelom. Forms all tissues of the cardiovascular system.
