Lecture 1: introduction and Gametogenesis 1 Flashcards
Define ontogeny
Includes all developmental processes from contraception to death
Define embryogeny
the part of ontogeny from contraception to birth
Define determination
process by which a cell or part of an embryo becomes restricted to a given developmental pathway
Define differentiation
complex changes involved in specialization of structure and function
Define morphogenesis
generation of form or assumption of new shape
Define induction
effect that one embryonic tissue has on another that changes the development that changes it from if the inhibitor had been absent
Define integration
process by which different tissues are brought together and combined
When is the first appearance of germ cells in humans?
24 hours after fertilization
Define teratomas
growths from misdirected migrating primordial germ cells with mixtures of highly differentiated tissues
What are the 5 stages of prophase 1?
- leptotene
- zygotene
- pachytene
- diplotene
- diakinesis
What are the major results of meiosis?
- increase in cell numbers
- daughter cells are not genetically identical
- daughter cells are haploid
Describe leptotene
first stage of prophase one:
- chromosomes are threadlike
- chromosomes consists of two chromatids
- chromosomes begin to coil
Describe zygotene
-homologous chromosome pair (synapsis); synaptonemal complex forms
Describe pachytene
- maximum coiling
- tetrads
- crossing over begins
Describe diplotene
- crossing over continues
- chiasmata well defined
Describe diakinesis
- crossing over is complete
- terminalization
- spindle apparatus in place
- nuclear membrane disrupted
What happens in the event of a nondisjunction?
Aneuploidy
What are mutations that cause changes in part of a chromosome?
translocations
deletions
inversions
duplications
Describe the fetal period in regards to follicular structure
the diploid oogonium is not surrounded by follicle cells
there is no follicle
1 chromatid/chromosome
Describe the later fetal period through birth
primary oocyte has advanced to the diploid stage of meiosis
primordial follicle with flattened follicle cells
2 chromatids.chromosome
Describe the follicular structure in regards to birth to puberty
-diploid primary oocyte
-primary follicle with a single layer of cuboidal follicle cells
-connected via gap junctions
zona pellucida separates primary oocytes from follicular cells
2 chromatids/chromsome
List the components of the Tertial Graafian follicle from external to internal
- theca externa (produce angiogenesis)
- theca interna (LH receptors, secrete testosterone)
- membrana granulosa
- mural granulosa (develop FSH receptors, synthesize aromatase in response to FSH which converts testosterone)
- antrum
- cumulus (facilitate release of ovum)
- zona pellucida
- oocyte
What are the characteristics of the Graafian follicle
Large
projects from ovary
9 day development
What does the egg accumulate from external sources?
via heterosynthesis through follicle cells or nurse cells; yolk manufactured in the liver
What does the egg accumulate from itself?
via autosynthesis
lamp brush chromosomes, gene amplification
Describe the corona radiata
layer of follicle cells surrounding the oocyte and interacts via gap auctions and microvilli
Describe the zona pellucida
non-cellular membrane that is secreted ny the corona radiata and oocyte
