Lecture 4 - Menstrual cycle II Flashcards
Follicular development: what happens in the beginning of follicle development?
- Primordial germ cells migrate from the yolk sac to the foetal ovary
- Mitosis occurs but cytokinesis is incomplete - cells become interconnected (germ cell cysts/nests)
- Oocytes enter meiosis but become arrested at prophase of meiosis I, breakdown of intracellular bridges and enclosure of oocytes occurs
- Primordial follicles formed (1x10⁶ at birth)
Follicular survival: do all follicle cells survive?
No, some undergo apoptosis before entering meiosis I (this occurs while still connected through intracellular bridges)
No, environmental contaminants may cause the formation of primordial follicles with more than one oocyte - these become programmed for death as the egg is compromised
Primordial follicles: what is the next step of development after this and what are the differences?
Primary follicle formation
Oocytes are still arrested at MI prophase, but primary follicles have cuboidal granulosa cells (instead of flat) and also have a zona pellucida
Primary follicles: what is the next step of development after this and what are the differences?
Secondary follicle formation
Oocytes are still arrested at MI prophase and they have a zona pellucida, but secondary follicles are larger, have multiple layers of granulosa cells (instead of a single cuboidal layer) and also have a theca
Theca cells: what are they, what do they do, where are they located, and what types are there?
Endocrine cells that support oocytes
Secrete hormones, provide follicular structural support, etc
In secondary follicles
Theca interna - closest to granulosa
Theca externa - outside follicle, structural support
Follicular development from primordial to secondary follicle: what gonadotrophin(s) is it dependent on?
None, this process process is gonadotrophin independent - relies on OSFs
OSF: what are they, what do they do, what are some examples, and what families do these examples come from?
Oocyte-secreted factors
Promote follicle development
GDF-9
BMP-15
TGFβ superfamily
Granulosa cell: what are they, what do they do, what are some secreted factors, and what do these secreted factors do?
Ovarian cells which secrete hormones
Kit ligand - promotes follicular development
AMH - suppresses follicular development
Kit ligand: what is it and what does it do?
A factor produced by granulosa cells
Promote follicular development
AMH: what is it and what does it do?
Anti-mullerian hormone - may be used to determine follicle reserves (higher AMH keeps reserves for longer - follicles stopped from activating too soon)
Suppress follicular development
GDF-9: what is it and what does it do?
Growth differentiation factor 9
Promote follicular development
BMP-15: what is it and what does it do?
Bone morphogenic protein 15
Promote follicular development
Tertiary follicle development: what is required for development into this stage, and what are the similarities/differences with the prior stage?
FSH-dependent
Oocytes are still arrested at MI prophase, they have a zona pellucida, granulose cells, and a theca
Tertiary follicles are larger, have mural (around the follicle) and cumulus (immediately around the oocyte) granulosa cells, and antral cavity (produced from granulosa cells)
Antral cavity: what is it, what is it produced by, and what does it do?
Secreted fluid which accumulates between cells
Granulose cells - requires FSH presence
Provides an environment for follicle development
Pre-antral vs antral follicles: what are they and why is each named as such?
Pre-antral - name given to secondary follicles due to lack of antral cavity presence, these do not produce sex steroids
Antral - name given to tertiary follicles due to antral cavity presence, these produce sex steroids
