Oogenesis Flashcards
Know the 4 phases of oocyte maturation.
-Primordial oocyte
-Primary oocyte
-Secondary oocyte
-Ootid
What follicles are primary oocytes found in?
-Primordial follicles
-Primary follicles
-Secondary follicles
-Tertiary follicles
What follicles are secondary oocytes found in?
Ovulation follicles
Define/describe the zona pellucida
-A glycoprotein-rich layer surrounding the egg
-Designated Zona Protein (ZP) 1, 2, and 3: Sperm binds to ZP3
Know what polar bodies are.
-A small cell produced during egg maturation
-Contains one set of chromosomes
Know how oogenesis occurs
-primordial germ cell: Mitosis
-Oogonia (diploid)
-primary oocyte
-LH surge: meiotic inhibitors removed
-secondary oocyte
-ovulation
-second meiotic diision producing second polar body
-Fertilization
-ootid
-Zygote
Primordial germ cell
-prenatal
- Precursor cells that give rise to eggs and sperm
-2n (diploid)
-Mitosis
Primary oocyte
-prenatal and post pubertal
-4n
-Primary oocytes are present throughout follicle development: primordial, primary, secondary, and tertiary follicle (Dominant)
-Meiotic prophase begins and DNA replicates
-Nuclear arret at end of first meiotic prophase
Secondary oocyte
-LH surge signals progression up to metaphase 2: Rearrested into dictyate
-Cortical granules move to just inside oocyte plasma membrane
-Perivitelline space completely formed
-First polar body discards half the DNA
-2n cell
Ootid
-Post-pubertal
-An immature egg with two pronuclei that have not yet combined.
-Second polar body discards half the remaining DNA
-Contact with sperm cell
-1n Cell
Zygote
-The cell formed by the fusion of the egg and sperm
-Fusion of maternal and paternal
-1n cell from each
Know the characteristics of primordial germ cells.
-Found in prenatal fetus
-Originate from the gut and migrate to developing gonads
-10-20 micrometers
-Mitotic divisions: 20-100 cells divide into millions
-2n cells
Know the characteristics of primary oocytes.
-Prenatal and post-pubertal
-Progression into 1st meiotic prophase
-Development pauses in prophase 1 (Dictyate: Period of prolonged rest)
-4n cells
-Primary oocytes are present throughout follicle development
How does the primary oocyte change in a primordial follicle as it grows and develops.
-Single layer squamous epithelial cells
-Primordial resting pool
How does the primary oocyte change in a primary follicle as it grows and develops.
-Single layer of 11-20 cuboidal granulosa cells
-Begin to see increase in organelles
-Elongated mitochondria and dividing mitochondria
-Smooth and rough ER
How does the primary oocyte change in a secondary follicle as it grows and develops.
-Second layer of granulosa cells
-Initial deposition of zona pellucida: glycoproteins
-Cortical granules formed
-Oocyte begins RNA synthesis
How does the primary oocyte change in an early tertiary follicle as it grows and develops.
Becomes transcriptionally active
How does the primary oocyte change in a tertiary follicle as it grows and develops.
-Perivitelline space appears
-Free smooth and rough ER decrease
-Hooded mitochondria appear
-Organelles cluster and nucleus migrate to periphery: Mitochondria, Golgi bodies, and Cortical granule
How does the primary oocyte change in a dominant follicle as it grows and develops.
-Increase in lipid content
-Decrease in size of Golgi bodies
-Cortical granules move closer to plasma membrane
Describe what happens to the oocyte as a result of the LH surge.
-cortical granules move to just inside the oocyte plasma membrane
-Perivitelline space completely formed
-Further increase in lipid content and decrease in Golgi bodies
-Meiosis resumes
Know stages at which meiosis becomes arrested and what events release each arrest.
-Prenatal: Meiosis is first arrested in Prophase 1
-LH surge: Continues and arrested again in Metaphase 2
-Fertilization: Completes meiosis 2
