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Animal Production > Follicles & Corpus Luteum > Flashcards

Follicles & Corpus Luteum Flashcards

1
Q

What does a follicle become when it releases the egg inside it?

A

corpus luteum

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2
Q

What are the functions of the ovaries?

A
  • development of the female gamete (oocyte) for fertilization
  • production & secretion of sex steroid hormones that regulate reproductive health
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3
Q

How is the ovary is divided in most mammals, and what is the exception?

A
  • in most mammals, ovary is divided into 2 distinct regions: AN OUTER CORTEX & AN INNER MEDULLA
  • the cortex contains the ovarian follicles, while the medulla houses blood vessels, nerves, & CT
  • Eq are the opp of all other mammals; inner cortex and outer medulla, but otherwise structurally and functionally the same
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4
Q

What is folliculogenesis?

A
  • the developmental process of ovarian follicles starting from a reserve of quiescent primordial follicles set up in early life & ending w/ either ovulation or follicular death by atresia
  • primordial -> primary -> early secondary -> secondary -> antral -> preovulatory
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5
Q

What are the two phases of folliculogenesis?

A

resting phase (primordial follicles) & growth phase

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6
Q

In which three cell populations do major cellular events occur in during gonad transformation to ovaries?

A
  1. the supporting cells, a subtype of somatic cells that become GRANULOSA CELLS
  2. the steroidogenic cell precursors, another subtype of somatic cells that later become THECA CELLS
  3. THE PRIMORDIAL GERM CELLS, WHICH BECOME OOCYTES THROUGH THE PROCESS CALLED OOGENESIS
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7
Q

Where does development of the ovary commence?

A

At the mesonephric surface epithelium in the location of the future gonadal ridge

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8
Q

What are the steps in the development of primordial follicles?

A
  1. the development of the ovary commences at the mesonephric surface epithelium in the location of the future gonadal ridge
  2. some mesonephric surface epithelial cells change phenotype into gonadal ridge epithelial-like (GREL) cells
  3. the GREL cells proliferate, & the basal lamina underlying the mesonephric surface epithelium breaks down, allowing stromal cells to penetrate into the gonadal ridge
  4. GREL cells continue to proliferate & primordial germ cells (PGCs) migrate into the ridge between the GREL cells
  5. oogonia proliferate & stroma penetrates further towards the ovarian surface, enclosing oogonia & GREL cells into ovigerous cords
  6. a compartmentalization into the cortex and medulla becomes obvious. GREL cells at the surface align to the basal lamina & begin to differentiate into typical ovarian surface epithelium
  7. ovigerous cords are partitioned into smaller cords & eventually into follicles. these contain GREL cells that form granulosa cells & oogonia that form oocytes.
  8. at the final stage, the surface epithelium becomes mostly single-layered & a tunica albuginea is formed
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9
Q

What do primordial follicles consist of ?

A
  • primordial follicles consist of a primary oocyte, surrounded by a single layer of flat follicular cells (~6 cells), ~90 days of gestation (cattle), diameter of ~35.2 micrometers
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10
Q

How do Ru & Car primordial follicles differ?

A

In Car, primordial follicles are clustered, while in Ru they are singular.

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11
Q

What is a primary follicle?

A
  • when the epithelium around the primary oocyte becomes cuboidal (~10-40 cells), the follicle is called a primary follicle
  • ~140 days of gestation (cattle), diameter of ~46.1 micrometers
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12
Q

What is a secondary follicle?

A
  • follicle w/ 2-6 layers of granulosa cells is referred to as a secondary follicle
  • secondary follicles also acquire an additional somatic cell layer, the theca (typical steroid-producing cells)
  • initial deposition of the zona pellucida (ZP) material (glycoprotein layer secreted by the oocyte & granulosa cells)
  • ~210 days of gestation (cattle), diameter of ~81 micrometers
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13
Q

what is the tertiary (antral) follicle?

A
  • follicles w/ more than 6 layers of granulosa cells & a fluid (follicular)-filled antrum are referred to as tertiary (or antral) follicles
  • ~230-250 days of gestation (cattle), diameter of ~250 micrometers (smallest antral follicle)
  • transition from secondary to tertiary stage includes FULLY DEVELOPED ZP, THE DEVELOPMENT OF THE INTERNAL & EXTERNAL THECA CELL LAYERS, & THE BEGINNING OF CUMULUS CELL FORMATION
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14
Q

How is the antrum formed?

A

fluid comes from theca & granulosa cells together

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15
Q

What are Graafian follicles (preovulatory)?

A
  • the most mature stage of antral follicles
  • granulosa cells of the preovulatory follicle produce estradiol
  • differentiation of theca interna (vascular) & externa (CT)
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16
Q

What is the zona pellucida?

A

surrounds the oocyte & is located btwn the oocyte & the follicular cells

17
Q

What is the corona radiata?

A

the first layer of follicular (granulosa) cells outside the zona pellucida

18
Q

what is the cumulus oophorus?

A

(“egg-bearing heap”). a thickened mound of granulosa cells that surround the oocyte and project into the antrum

19
Q

What is the antrum?

A

the fluid-filled space (liquor folliculi) of an antral follicle

20
Q

What is the membrana granulosa?

A

the layer of granulosa cells (follicular cells) bordering the antrum

21
Q

what is the theca interna?

A

these cells are endocrine like and border the membrana granulosa

22
Q

what is the theca externa?

A

fibroblast-resembling cells just outside the theca interna. the exterior limits of the theca externa are not discernable b/c it blends & merges w/ other cells of the ovarian stroma; the beginning of this layer can be identified, however, by its proximity to the theca interna

23
Q

What are atretic (regressing) follicles?

A
  • follicular atresia can occur in different follicular phases (ex: primordial, primary, secondary, antral, & Graafian follicles)
  • atresia of follicles is an active cellular process w/ resorption of the follicle involving macrophage infiltration, phagocytosis, migration of fibroblasts from the theca, & production of collagen
  • NOT all Graafian follicles ovulate (ex: 0.01% of human primordial follicles will ever ovulate)
24
Q

What are the two types of ovulation in domestic mammals?

A
  1. spontaneous (most domestic animals)
  2. induced (queens, camelids, & rabbits)
25
Q

What happens when ovulation is near?

A

blood supply increases & the follicular wall becomes thin & transparent near the future site of ovulation

26
Q

What are the sizes of the preovulatory follicles in our domestic spp?

A

50-70 mm in mare, 13-16 mm in cow, 8-10 mm in ewe, goat, & sow, & 2 mm in Ca & queen

27
Q

What do you need to remember in females when checking the ovaries?

A

there are 2! need to check both w/ U/S. but they work as a unit together & wont ovulate @ the same time

28
Q

Summary of folliculogenesis:

A

primordial follicle -> primary follicle -> secondary follicle -> early antral follicle -> late antral follicle -> preovulatory follicle -> ovulation

29
Q

How do oocytes develop?

A
  • primordial germ cells migrate to the developing gonadal ridges &, during migration, PGCs proliferate via mitosis
  • upon arrival at the gonadal ridges, these PGCs differentiate into oogonia
  • oogonia undergo multiple rounds of mitotic division, increasing their number significantly
  • oogonia enter meiosis I & are then referred to as primary oocytes
  • primary oocytes initiate meiosis but are arrested in the diplotene stage of prophase I (dictyate stage)
  • the primary oocyte completes its first meiotic division immediately before ovulation to form a secondary oocyte & a first polar body (due to an LH surge)
  • however, in Ca & Eq, the follicle will release the primary oocyte & then it will become a secondary oocyte (while in most other animals it becomes a secondary oocyte prior to release)
30
Q

How does the corpus luteum develop?

A

it is a transient endocrine gland that develops from a Graafian follicle after ovulation & is required to support pregnancy in mammals
corpus hemorrhagicum -> corpus luteum -> corpus albicans

31
Q

what is the corpus hemorrhagicum?

A
  • once ovulation of the Graffian follicle (tertiary) has occurred, BLOOD DERIVED FROM TORN BLOOD VESSELS OF THE THECA LAYER INFILTRATES THE COLLAPSED FOLLICLE, & results in the formation of the corpus hemorrhagicum, a developing corpus luteum w/ a bloody core
32
Q

what is the corpus luteum?

A
  • the remaining granulosa cells & cells of the theca interna undergo hypertrophy, proliferate, & invade the corpus hemorrhagicum, transforming into granulosa lutein cells & theca lutein cells respectively (luteinization). these cells organize into a highly vascular glandular organ called the corpus luteum (Latin for “yellow body”)
  • the yellow colour of this structure is b/c of lutein (Eq, Bo, Ca, & Fe) or other lipid pigments (ewes & sows)
  • corpus luteum is fully developed by 9 days after ovulation in a cow, continues to grow till 12 days (grows up to 25 mm in diameter) & regresses in late diestrus
33
Q

What is the corpus albicans?

A

if pregnancy does not occur, the corpus luteum degenerates after a certain length of time, depending on the sp. it involves condensation of the lutein pigment & degeneration of luteal cells. the connective tissues replace the luteal cells & form the CORPUS ALBICANS (latin for “wht body”)

Animal Production (13 decks)

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