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Animal Reproduction > Quest 5 > Flashcards

Quest 5 Flashcards

1
Q

Estrous vs Estrus

A
  1. Estrous (adj.)
    - used to describe estrous when manipulating
    ex: estrous cycle
  2. Estrus (n.)
    - the act or display of being in estrous
    - period of sexual receptivity, or when in heat
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2
Q

Cycle

A
  • a series of continuous events that is marked by an event(s) of physiological importance
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3
Q

Estrous Cycle

A
  • a series of events that run from estrus (d1)-> estrus(end)

- estrus is a behavioral event

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4
Q

3 Types of Estrous Cyclicity

A
  1. Polyestrus
    - cow, swine and rodents
    - has a uniform distribution of many estrous cycles throughout the year
  2. Seasonally Polyestrus
    - deer, horse, sheep, goat
    - has many estrous cycles throughout the year, but within a specific season
  3. Monoestrus
    - dogs and pandas
    - has one estrous cycle throughout the year
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5
Q

Menstrual Cycle

A
  • menses to menses
  • menses (menstrual period) lasts 2-5 days
  • 28 to 42 days
  • ovulation at day 14
  • estrogen is high!
  • sloughing of endometrial lining
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6
Q

Estrous Cycle Phases

A
  • named after the predominant structure on the ovary during each stage
  • after day 1 (estrus stage) ovulation occurs btw phases on day 3
  • cycle ends after diestrus 15-17 days later
    1. Follicular Phase
    2. Luteal Phase
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7
Q

Follicular Phase of Estrous Cycle

A
  • named after follicles on ovary (primary structure is follicles on ovary)
  • growing and maturation of follicles on the ovary
  • period of regression of the Corpus Luteum (luteolysis) to ovulation
    -> luteolysis causes the decrease in progesterone, which increases GnRH, FSH and LH
  • estrogen concentration is highest in this phase (primary)
  • makes up 20% of the estrous cycle
    INCLUDES:
    1. proestrus (dec P4, inc E2)
    2. estrus stages (E2 is high)
  1. GnRH, FSH, LH released
  2. Follicular Development (recruitment, selection, dominance, atresia)
  3. Sexual Receptivity (Estrogen increase is responsible)
  4. Ovulation
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8
Q

Luteal Phase of Estrous Cycle

A
  • named after corpus luteum on the ovary (primary structure on ovary is corpus luteum)
  • period of ovulation to regression of the Corpus Luteum (luteolysis)
  • progesterone concentration is highest in this phase
  • makes up 80% of estrous cycle
    INCLUDES:
  • metestrus (dec E2, Inc P4)
  • diestrus (High P4, sustained levels)
    1. Ovulation
    2. Luteinization
    3. Synthesis and Secretion of Progesterone
    4. Luteolysis
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9
Q

4 Stages of Estrous Cycle

A
  1. Follicular Stages
    a. Proestrus
    b. Estrus
  2. Luteal Stages
    c. Metestrus
    d. Diestrus
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10
Q

Proestrus Stage of estrous cycle

A
  • transitory period (goes from a high concentration of progesterone to a high concentration of estrogen)
  • period of regression of the corpus luteum(luteolysis) to when estrus begins
  • estrogen secretion begins in this phase
  • lasts 2-5 days
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11
Q

Estrus Stage of estrous cycle

A
  • period from estrus to ovulation
  • estrogen is high
  • behavioral changes are noticed
  • period of sexual receptivity
  • demonstrates lordosis (arching of the back for mounting)
  • lasts 2-5 days
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12
Q

Metestrus Stage of estrous cycle

A
  • transitory period (goes from high estrogen to high progesterone)
  • period between ovulation and formation of functional corpus luteum
  • luteinization (when the ovulated follicle forms the corpus luteum)
  • lasts 2-5 days
  • progesterone secretion begins in this phase
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13
Q

Diestrus Stage of estrous cycle

A
  • corpus luteum is fully functional and secreting progesterone
  • high levels of progesterone
  • period when corpus luteum is fully functional to when it is regressed (luteolysis)
  • lasts 10-14 days
  • In cow, mares and sows lasts 14 days
  • In ewe lasts 10 days
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14
Q

Hormone concentration in the 4 stages (FSH, LH, GnRH)

A
  1. FSH stimulates follicles to produce estrogen
  2. LH is luteinizing, so will peak after estrogen peaks
    - peaks around estrus
  3. GnRH follows FSH and LH pattern
    - will peak before LH peaks
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15
Q

Silent Heat

A
  • first estrus
  • needs progesterone
  • no behavioral changes
  • progesterone stimulates the brain to be responsive to estrogen
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16
Q

Anestrus

A
  • without estrus (heat)
  • can last up to 5 months
  • can be caused due to stress, pathology, parturition, presence of offspring, lactation, pregnancy, season
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17
Q

QUEEN/BITCH Estrous Cycle

A
  1. anestrus- lasts 5 months
  2. Proestrus- lasts 9 days
  3. Estrus- affected by photoperiod
    - increased day light, will result in longer estrus period
    - copulation
    - ovulation (cats/rabbits are reflex-ovulators, will ovulate every time they breed)
    - superfecundation (multiple sires/males)
  4. Diestrus
    - will return to estrus after ovulation if not bred, if pregnant will remain in diestrus period for 63 days
    - can have a false pregnancy
    - after diestrus go to anestrus period
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18
Q

What do seasonal breeders depend on?

A
  • the amount of light

- the melatonin levels

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19
Q

Long Day Breeders

A 
- mares are long day breeders
HORSE
- inc day light, dec melatonin
- inc in RFRP-3, inc kisspeptin
- inc GnRH, inc FSH/LH
- reproductively active, can reproduce
SHEEP
- inc day light, dec melatonin
- dec RFRP-3, dec kisspeptin
- dec GnRH, dec FSH/LH
- reproductively inactive, unable to reproduce
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20
Q

Short Day Breeders

A 
- sheep, goat, elks, deer are short day breeders
HORSE
- dec day light, dec melatonin
- dec RFRP-3, dec kisspeptin
- dec GnRH, dec FSH/LH
- reproductively inactive, unable to reproduce
SHEEP
- dec day light, dec melatonin
- inc RFRP-3, inc kisspeptin
- inc GnRH, inc FSH/LH
- reproductively active, can reproduce
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21
Q

Estrous Cycle vs Menstrual Cycle

A
  1. Estrous Cycle
    - begins and ends with estrus and, or ovulation
    - the follicular phase is short and luteal phase is long
  2. Menstrual Cycle
    - begins (day 0) and ends with the start of menses (day 28)
    - menses(menstrual period) lasts 2-5 days
    - ovulation occurs in the middle of the cycle (day 14)
    - the follicular and luteal phases are about the same length
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22
Q

Tonic Center

A
  • basal secretion of GnRH throughout the estrous cycle
  • small amounts of GnRH are continuously released over a long period of time and causes a peak of GnRH
  • dec in progesterone, inc GnRH, inc FSH/LH, leads to follicle maturation and growth, produces estrogen
    ex: leaky faucet
23
Q

Surge Center

A
  • basal secretions of GnRH until receive a positive signal
  • positive signal is detected when estrogen reaches its threshold
  • when estrogen reaches threshold, GnRH will surge
  • “Full Blast Faucet”
  • > it will secrete large amounts of GnRH, then turn off
  • surge of GnRH important for ovulation
  • LH levels are 10x higher in surge than tonic
24
Q

Feedback on Surge center

A
  • when estrogen is low and progesterone is high there is negative feedback on surge center (dec GnRH pulses)
  • when estrogen is high and progesterone is low there is positive feedback on surge center (GnRH surge inc and secretes LH)
25
Q

Tonic center peaks during follicular and luteal phase

A
  • in follicular phase peaks every 1.5-2 hours

- in luteal phase peaks every 5-8 hours

26
Q

Follicular Dynamics

A
  • the growth and degeneration of follicles
  • 4 phases
    1. Recruitment (emergence)
    2. Selection
    3. Dominance
    4. Atresia (irreversible degeneration)
27
Q

Recruitment in Follicular Phase

A
  • the emergence/growth of a cohort of follicles
  • secrete estrogen
  • high FSH, low inhibin, low LH pulse frequency, low estrogen
28
Q

Selection in Follicular Phase

A
  • follicles are selected to become dominant
  • continue to secrete estrogen and inhibin
  • low FSH, moderate LH, low inhibin
  • in dogs/cats/pigs -> cohort of follicles selected
  • in cows/humans/mares -> one follicle selected
29
Q

Dominance in Follicular Phase

A
  • one or more follicles exerts major inhibiting effect on follicles from selected and recruited phase
  • continued production of estrogen and inhibin
  • high inhibin, high LH pulse frequency, low FSH
30
Q

Atresia in Follicular Phase

A
  • irreversible degeneration
  • disappearance or closure of the Antrum
  • occurs to 90% of follicles
  • continuous throughout folliculogenesis
31
Q

Progesterone levels affect on LH

A
  • increased levels of progesterone, LH secreted once every 4 hours
  • decreased levels of progesterone, LH secreted one time every hour (ovulation)
32
Q

How Antrum forms in Follicular Phase

A
  1. Primordial follicle formed with development of ovary
    - one layer of squamous epithelium
  2. Primary follicle (Recruitment)
    - becomes 1 layer of cuboidal epithelium
  3. Secondary follicle (selection)
    - forms 2 more layers of cuboidal epithelium (3 layers)
  4. Tertiary follicle (Graafian follicle, pre-ovulatory, ovulatory, antral)
    - antrum (fluid filled sac) is developed
33
Q

2 gonadotropins acting on cell in Follicular Phase

A
  1. FSH

2. LH

34
Q

Theca cell components in Follicular Phase

A
  1. oocyte
  2. Granulosa cells
    - closest to oocyte
  3. Theca interna
    - closest to granulosa cells
  4. Theca externa
    - furthest from granulosa cells
35
Q

2 cell, 2 gonadotropin theory in Follicular Phase

A
  • granulosa cells produce receptors for FSH
  • theca cells produce receptors for LH
  • the theory describes how the 2 cells and 2 gonadotropins interact to cause ovulation and estrogen synthesis
36
Q

2 cell, 2 gonadotropin theory steps (how it works)

A
  1. GnRH secreted from the hypothalamus and increases production of LH and FSH
  2. LH binds to theca cells
  3. Theca cells convert cholesterol to testosterone when LH binds
  4. Testosterone can cross into the granulosa cells which have FSH receptors, when FSH binds converts testosterone to estrogen
  5. Estrogen sends signals to the hypothalamus to secrete more GnRH, which increases production of FSH and LH
    - positive feedback system
  6. Cycle continues until a threshold of estrogen has been reached
    - Granulosa cells will start to lose FSH receptors and
    will synthesize LH receptors
    - when LH receptors are present, surge center can exert its full affect of LH on follicle cells
    - when LH surges, follicle cell is very responsive to it and will cause ovulation (sexual receptivity)
37
Q

Sexual Receptivity in the Follicular Phase

A
  • occurring as estrogen is increasing
    1. Increased blood flow universally (to all organs)
  • increase in secretory cavities
  • increase in delivery of leukocytes (aids in phagocytosis of foreign material)
  • swelling of genitalia
    2. Changes in the mucosal epithelium
  • Posterior vagina thickens
  • Anterior vagina increases secretions (flushing, lubrication and gamete transportation)
  • Cervix increases
  • Uterus (prepping of endometrium glands)
  • Oviduct (increase secretions and increase beat frequency of cilia)
    3. Increase in the Muscular Tone of the Reproductive Tract
  • has slight contractions to aid in gamete transportation
38
Q

Ovulation in the Follicular Phase

A
  • estrus occurs before ovulation
  • sophisticated process involving the release of an oocyte and the destruction of follicular tissue
    1. LH surge caused by a threshold of estrogen
  • results in an inc histamine, inc prostaglandin E2, inc prostaglandin F2(alpha), inc progesterone (locally), inc in blood flow (locally)
    2. Inc in blood flow to the dominant cell
  • theca cells become edematous (swell)
  • excess fluid goes to antrum and gets trapped in the ovary, increase in pressure will eventually cause it to pop
    3. Theca cells produce progesterone (inc)
  • Progesterone stimulates the production of the enzyme collagenase
  • Collagenase breaks down the connective tissue surrounding the ovary (Tunica Albuginea)
  • Increase in pressure and breakdown causes an apex, or a point of weakness, on the Tunica Albuginea
    4. Increase production of Prostaglandin E2
  • produces plasminogen to help dissolve blood clot (corpus hemorrhagicum) when the tissue ruptures and aids in follicular remodeling to the corpus luteum after ovulation
    8. Increase production of Prostaglandin F2(alpha)
  • start to see smooth muscle contract
  • lysosomes within the granulosa cells will rupture and release enzymes that will further deteriorate the connective tissue
39
Q

LH Surge in follicular phase hormone production

A
  1. Inc Histamine
    - causes theca cells to become edematous (swell), accumulation of fluids in follicle (increases pressure)
  2. Inc Prostaglandin E2
    - increases blood flow in follicles and aids in follicular remodeling after ovulation
  3. Inc Blood Flow
    - accumulation of more fluid in the follicles, inc pressure (mechanical pressure)
  4. Inc Prostaglandin F2(alpha)
    - smooth muscle contractions, and lysosomes will rupture, causes a release of enzymes that break down follicular tissue
  5. Inc Progesterone
    - produces collagenase, an enzyme that breaks down the connective tissue covering the ovary (Tunica Albuginea)
    - weakens the follicular wall (chemical-enzyme)
    * follicular wall needs to be weakened for ovulation to occur and oocyte to be released
40
Q

Cumulus Oocyte Complex

A
  • This is made up of the oocyte, zona pellucida, and granulosa cells
  • formed during ovulation
41
Q

When do oocytes undergo Meiosis 1?

A
  • with ovulation, oocytes undergo meiosis 1
  • formation of the first polar body
  • one cell holds all of the genetic material, any other structure forms a polar body
42
Q

Ovulation in Luteal Phase of Estrous Cycle

A
  • bleeding
  • forms a blood clot called the corpus hemorrhagicum
  • after ovulation lasts for about 1-3 days of estrous cycle
43
Q

Luteinization in Luteal Phase of Estrous Cycle

A
  • transformation of remaining follicle cells to luteal cells
  • transformation dependent on LH
  • oocyte leaves the cumulus oocyte complex (COC)
  • granulosa cells, basement membrane and theca cells remain in ovary
  • fluid in antrum leaves
  • basement membrane begins to disintegrate before oocyte is released
  • remaining cell in ovary is the corpus luteum
  • granulosa cells are now responsive to LH (not FSH)
  • theca cells are always responsive to LH
44
Q

Before luteinization in luteal phase three things must occur:

A
  1. Disintegration of Basement Membrane
    - mixing of theca and granulosa cells
  2. Follicular Wall Collapse
    - all cell populations mix together
    - folds interdigitate
    - uniform mixing of theca and granulosa cells
  3. Gland Forms
    - luteal cells are derived from basement membrane, granulosa cells and theca cells
    - both granulosa cells and theca cells form luteal cells through luteolysis and both are steroidogenic (produce progesterone)
    a. Granulosa cells
    - can range from 20-70 micrometers (um) and form large luteal cells
    - have secretory granules that contain oxytocin
    - the # of granulosa cells in the follicle = the number of large luteal cells in the newly formed Corpus Luteum
    - large luteal cells can grow in size (hypertrophy)
    b. Theca cells
    - are under 20 micrometers (um) and form small luteal cells
    - are irregularly shaped and contain lipid droplets
    - small luteal cells can increase in number during growth of corpus luteum (hyperplasia)
45
Q

Summary of Ovulation Factors in Luteal Phase

A
  1. Bigger follicle = Bigger Corpus Luteum
  2. Bigger Corpus Luteum = More Progesterone production
  3. More progesterone production = better maintenance of pregnancy
46
Q

What does the Gland Form in Ovulation in Luteal Phase

A
  • small luteal cells
  • large luteal cells
  • connective tissue
  • vascularization (fluids and angiogenic factors)
47
Q

Secretion and Synthesis of Progesterone in Luteal Phase

A
  • the fully functional Corpus Luteum produces progesterone
  • progesterone targets the hypothalamus and uterus
    1. In Hypothalamus:
  • progesterone has negative feedback on hypothalamus
  • increased levels of progesterone cause dec GnRH, dec FSH/LH, dec estrogen levels
  • prevent folliculogenesis and ovulation
  • inhibits behavioral estrus
    2. In Uterus:
    a. increases uterine secretions
  • supports development of uterine glands
    b. decreases uterine contractions
  • supports develop of mammary glands during pregnancy, prepares for lactation
  • causes a uterine quiescence
48
Q

Progesterone Synthesis requires?

A
  1. Cholesterol

2. Basal Concentration of LH

49
Q

Steps for Progesterone Synthesis

A
  1. Cholesterol is delivered to a luteal cell inside of a lipoprotein (HDL/LDL)
  2. Cholesterol leaves the lipoprotein (HDL/LDL) inside of the luteal cell
  3. LH binds to luteal cells (receptor-ligand interactions)
  4. Cholesterol enters the mitochondria of the luteal cell
  5. Cholesterol is converted to pregnenolone
  6. Pregnenolone leaves mitochondria of luteal cell
  7. Pregnenolone is converted to progesterone
  8. Progesterone picked up by capillaries
  9. Capillaries deliver to target cell
50
Q

Luteolysis in luteal phase

A
  • the lysis, or destruction of the corpus luteum
  • lasts 2 to 3 days
  • during the proestrus stage
  • 10 to 14 days after progesterone production begins
  • if not pregnant, this will occur
  • if pregnant, fetus will secrete an antiluteolytic factor (Maternal Recognition of Pregnancy)
    1. Prostaglandin F2(alpha)
  • kills and removes luteal cells by decreasing blood flow and phagocytosis/cytokines
  • prevents steroidogenesis (progesterone production)
  • originates from endometrium and is locally produced
  • countercurrent exchange of Prostaglandin F2(alpha) between uterine vein and ovarian artery
51
Q

Effects of Different Hysterectomies

A
  1. Intact Uterus
    - has both uterine horns
    - lysis of CL will occur
  2. Contralateral Hysterectomy (Opposite side of CL)
    - uterine horn on the opposite side of CL is removed
    - lysis of CL will occur
  3. Ipsilateral Hysterectomy (same side of CL)
    - uterine horn on the same side of CL is removed
    - CL will persist
  4. Total Hysterectomy
    - both uterine horns are removed
    - CL will persist
52
Q

What stimulates Prostaglandin F2(alpha) in late luteal phase?

A
  • large luteal cells have secretory granules that contain oxytocin
  • inc in oxytocin causes inc in Prostaglandin F2(alpha)
  • Inc in PG F2(alpha) causes a loss of progesterone receptors
53
Q

Corpus Albicans

A
  • connective tissue in the corpus luteum

- leftover scar (white body) is formed

Animal Reproduction (13 decks)

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