Term
| What happens during formation & activation of primordial follicles, after the initial differentiation of the gonad? (4 points) |
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Definition
-large number of primordial germ cells die
-squamous granulosa begin to differentiate
-oocytes organize in clusters surrounded by squamous granulosa
-oocytes start meiosis, arrest in Prophase 1 |
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Term
True or False
Primordial follicles will continue to differentiate throughout a female mammal's life |
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Definition
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Term
| What hormone regulates the process of primordial follicle formation in mammals? |
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Definition
| none, it is LH/FSH independent |
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Term
| What is theorized to cause oocytes to arrest in Prophase 1 |
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Definition
| estradiol & progesterone levels drop just before assembly & activation of the follicles, theorized to cause the arrest of meiosis |
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Term
| What are the steps involved in formation of an ooctye? |
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Definition
Primary Follicle
Secondary Follicle
Antral (tertiary) Follicle
Dominant Follicle |
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Term
| What is a primary follicle? What is happening at this stage of oocyte development? (4) |
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Definition
-simple cuboidal cells surrounding the oocyte
-meisosis arrested in diplotene stage of Prophase 1, chromosomes condense & are actively transcribed
-membrane surrounds the oocyte (future zona pellucida)
-oocyte secretes factors to stimulate granulosa cells, which secrete other factors stimulating oocyte gtowth |
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Term
| Describe what is happening during oocyte growth (5) |
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Definition
-organelles replicate (esp. mito & DNA)
-ribosomes, mRNA & proteins increase
-nutrients stored in granules & vesicles
-Golgi enlarge & move to periphery
-centriole disappears |
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Term
| Describe the interactions that occur between the oocyte & the granulosa cells |
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Definition
-Granulosa cells begin expressing FSH receptor
-cells & oocyte can now communicate via gap-junctions, critical in preventing continuation of meiosis |
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Term
| Describe what happens during the development of the secondary follicle (4) |
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Definition
-granulosa cell layers increase
-theca cells begin multiplying on outside of basal lamina
-blood vessels develop within theca
-nutrients & waste will diffuse from theca layer |
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Term
| Describe what happens during the development of the antral follicles (4) |
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Definition
-fluid filled cavity appears
-granulosa & theca cells multiply
-theca externa cells form a muscular innervated layer
-theca interna cells produce androgens under control of LH & insulin |
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Term
| What are the two layers of theca cells and what do each do? |
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Definition
-theca externa cells form a muscular innervated layer
-theca interna cells produce androgens under control of LH & insulin |
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Term
| What is a follicular wave? |
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Definition
Recruitement: group of small antral follicles grow & mature in synchrony
Selection: some follicles stop growing & undergo atresia, others continue growing
Dominance: some follicles have a large number of FSH receptors, continue growing to form a Graafian follicle even when there is only a small amount of FSH present |
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Term
| What causes some antral follicles to undergo atresia during the selection process? |
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Definition
Inhibin levels increase, inhibiting FSH production
-follicles with fewer FSH receptors close off |
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Term
| What happens to the levels of FSH, LH and inhibin present as you move from recruitment to selection to dominance during a follicular wave? |
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Definition
Recruitement: high FSH, low LH, no inhibin
Selection: low FSH, moderate LH, low inhibin
Dominance: low FSH, high LH, low inhibin |
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Term
| When does the final maturation of oocytes occur? |
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Definition
| immediately prior to ovulation |
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Term
| Describe the process of resuming meiosis (3 steps) |
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Definition
1. Germinal vesicle braks down
-LH stimulates production of growth fators (IGF)
-LH surge densensitizes granulosa cells, decreasing cAMP
2. First meiotic division completes, expelling the first polar body
3. Initiation of Meiosis 2, arresting in Metaphase 2 until fertilization occurs |
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Term
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Definition
| excess DNA wrapped in a membrane to be disposed of |
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Term
What is cytoplasmic maturation & why is it important?
What changes occur? |
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Definition
Metabolic & structural changes in the oocyte essential to ensure proper fertilization, processing of sperm & preparation for pre-implantation.
-oocyte gains ability to release Ca upon fertilization
-produces proteins to prepare male pronucleus
-mRNA, proteins, substrates & nutrients accumulate |
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Term
| Why is oocyte maturation important? |
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Definition
-despite there being many oocytes present on an ovary, only a few collected will be pre-ovulatory and capable of fertilization
-if we want to do in-vitro fertilization, using hormones to increase the number of dominant follicles present we can obtain a large number of 'fertilizable' oocytes |
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Term
| Describe the steps involved in ovulation |
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Definition
1. LH surge causes fluid to accumulate, increasing pressure on follicle
-collagenase loosens ovarian connective tissue
-blood flow to ovary increases, more fluid accumulates
2. Follicuular wall burst
3. Oocyte is released from granulosa cells & captured by the infundibulum
4. Oocyte is moved to the ampula by the ciliated epithelium of infundibulum |
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Term
| Describe the hormone changes & their effects during ovulation (5 points) |
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Definition
-LH surge causes local production of progesterone & its receptor
-COX-2 enzyme stimulates prostaglandin production
-prostaglandings act on epithelial cells of the presumptive stigma
-lysosomal enzymes are released, degrading underlying tissue
-stigma forms & egg-cumulus complex is released |
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Term
| What is the luteal phase? (4) |
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Definition
-corpus hemorrhagicum forms (granulosa & theca cells)
-hemorrhagic trauma heals, corpus luteum is formed
-large amounts of progesterone are produced which have negative feedback on GnRH
-blood vessels invade |
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Term
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Definition
| a temporary structure composed of ex-granulosa & ex-theca cells, which produces large amounts of progesterone |
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Term
| How soon after ovulation should an oocyte encounter spermatozoa in the oviduct to ensure successful fertilization? |
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Definition
| 15-30 minutes post-ovulation |
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Term
| Why is it important to detect estrous in cattle? |
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Definition
| indicates ovulation is about to occur, and you should breed the cow within 24hrs |
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Term
| What stimulates mounting behaviour & standing to be mounted? |
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Definition
| increased levels of estradiol 17-B |
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Term
| Describe the factors that might affect expression of mounting behaviour |
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Definition
-footing
-lameness
-time of day
-head room
-distractions
-temperate weather |
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Term
| Describe the non-behavioural changes that occur at estrus |
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Definition
-low progesterone, high estradiol 17-B
-surge in LH & FSH
-production of cervical mucus & estrus-related odours
-vulval reddening/swelling |
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