Reproductive - week 23

Question 1

uterine (fallopian) tube

Answer 1

where sperm and oocyte will meet and fertilization will occur –> contains cilia that help to move the oocyte or embryo along uterine

Question 2

uterus

Answer 2

muscular organ
- accommodates and maintains pregnancy
- site of normal embryo implantation into the endometrium
- development of endometrium regulated by estrogen
- maturation of endometrium regulated by progestrone

Question 3

what is the endometrium

Answer 3

lining of uterus

Question 4

ovary

Answer 4

site of developing female gamete
- responsive to FSH and LH
- secretes estrogen and progesterone
- ovary will release oocyte during ovulation

Question 5

cervix

Answer 5

forms connection between vaginal canal and uterus
- secretes mucus that varies during menstrual cycle from thin (to facilitate sperm entry) to thick (prevent sperm entry)
- higher estrogen levels cause cervical mucus to be thinner
- higher progesterone levels cause cervical mucus to be thicker

Question 6

vagina

Answer 6

receives penis and sperm during copulation
- allows for discharge of fluid during menstruation and birth of baby

Question 7

fimbrea

Answer 7

capture the oocyte after released by ovary at ovulation
- finger like projections that sweep oocyte into uterine (fallopian) tube

Question 8

stages where most oocytes are blocked at

Answer 8

• oocytes begin meiosis during gestation (time between conception and birth) but stop at the diplotene stage (stage of prophase 1) of prophase 1 and then resumes at puberty in oocytes that are recruited
• oocytes that are not recruited remain dormant until they are recruited during a future menstrual cycle ( therefore oocyte may stay blocked for 50-55 years)

Question 9

if oocyte recruits

Answer 9

becomes unblocked and meiosis will resume.

meiosis

Question 10

syngamy

Answer 10

joining of sperm DNA and oocyte DNA

Question 11

fertilization

Answer 11

triggers meiosis II to resume
- another polar body produced
- makes oocyte a haploid cell just in time for sperms DNA to be added to oocyte DNA
- form a zygote (1-cell embryo)

Question 12

oogenesis

Answer 12

oocyte development
- refers to egg itself

Question 13

zona pellucida

Answer 13

forms during oocyte development
- “egg shell”
- gelatinous layer between oocyte and cells of follicle

Question 14

‘nurse’ cell

Answer 14

contribute to maturation, maintenance and care
- granulosa and theca cells
- secrete ovarian hormones (estrogen and progesterone)

Question 15

folliculogenesis

Answer 15

process where ovarian follicles mature
- start from small primordial to larger preovulatory follicles

Question 16

stages of folliculogenesis

Answer 16

primordial follicle
primary follicle
secondary follicle
tertiary (antral) follicle

Question 17

atresia

Answer 17

follicles degenerate

Question 18

hypothalamic-pituitary-gondal axis

Answer 18

• where GnRH is released from hypothalamus to cause release of FSH and LH from anterior pituitary
• FSH and LH travel to gonads, specifically ovaries to regulate gametogenesis

Question 19

primordial follicle

Answer 19

• follicle consists of an oocyte (immature egg cell) that is surrounded by a single layer of flattened granulosa cells
• follicles are formed during fetal development and remain dormant until puberty

Question 20

primary follicle

Answer 20

• upon activation, 30-50 of the primordial follicle develop into primary follicle
• only one will become the dominant follicle and go on to be ovulated
• rest of them will degrade in a process called atresia
• granulosa cells become cuboidal and start to proliferate (reproduce rapidly)
  
  • forms multiple layers around the oocyte
• here the zona pellucida is also formed

Question 21

secondary follicle

Answer 21

• what the primary follicle matures into
• granulosa cells continue to multiply and a new layer of cells called the theca cells form around the follicle

Question 22

tertiary (antral) follicle

Answer 22

what the secondary follicle becomes
- characterized by the formation of a fluid-filled cavity called the antrum
- granulosa cells and theca cells continue to multiply and follicle grows larger

Question 23

pre-ovulatory follicle

Answer 23

the tertiary follicle matures and the antrum enlarges
- the follicle is ready to release the oocyte during ovulation

Question 24

ovulation

Answer 24

the follicle ruptures and release the mature oocyte into uterine tube, where it can be fertilized by sperm

Question 25

corpus luteum formation

Answer 25

after ovulation the remnants of the follicle transform into the corpus luteum, which secretes hormones to support a potential pregnancy if no pregnancy occurs, then it degrade into scar tissue called the corpus albican

Question 26

what are endometrial changes

Answer 26

thickening and preparation of uterine lining for potential implantation

Question 27

what is the step by step regulation of menstrual cycle by HPG axis

Answer 27

1. Hypothalamus releases GnRH in pulses 2. pituitary gland releases FSH and LH 3. ovaries produce estrogen and progesterone 4. feedback loops regulate the cycle 5. estrogens positive feedback loop on LH 6. if pregnancy does not occur the corpus luteum breaks down, progesterone and estrogen levels drop and endometrial lining sheds (menstruation) the cycle restarts where hypothalamus releases GnRH again

Question 28

step 1: hypothalamus releases GnRH in pulses

Answer 28

travels to the anterior pituitary and controls the release of FSH and LH

Question 29

step 2: pituitary gland releases FSH and LH

Answer 29

follicle stimulating hormone: stimulates folliculogenesis, leading to growth of several ovarian follicles - one dominant follicle emerges and produces estrogen Luteinizing Hormone: - works with FSH to mature the dominant follicle - sudden LH surge triggers ovulation, releasing the egg

Question 30

step 3: ovaries produce estrogen and progesterone

Answer 30

- the growing follicles release estrogen which has 2 effects 1. stimulates thickening of endometrial lining, prepare for implantation 3. provides feedback to brain to regulate FSH and LH levels after ovulation, empty follicle becomes corpus lutem which secretes progesterone - progesterone stabilizes the endometrial lining and makes it receptive for a fertilized egg

Question 31

step 4: feedback loops regulate the cycle

Answer 31

negative feedback: high estrogen and progesterone inhibit FSH and LH production to prevent multiple ovulations

Question 32

step 5: estrogens positive feedback loop on LH

Answer 32

- during most of menstrual cycles, estrogen provides negative feedback to hypothalamus and pituitary gland which suppresses FSH and LH release - just before ovulation, estrogen briefly switches to positive feedback loop which leads to an LH surge and triggers ovulation

Question 33

how do progesterone and estrogen work

Answer 33

- as the dominant follicle matures it produces a high level of estrogen - when estrogen reaches the threshold (~12-14 days of the cycle), it stimulates the hypothalamus and pituitary - the positive feedback causes rapid surge in LH along with small FSH increases - the LH surge triggers ovulation and a release of egg from follicle - after ovulation, the estrogen drops and progesterone is released from corpus luteum restoring negative feedback and suppressing LH release the temporary positive feedback mechanism ensures that ovulation occurs at the right time in the cycle

Question 34

hormones and how they affect the uterine lining

Answer 34

- estrogen stimulates thickening of endometrial lining during first half of menstrual cycle - prepare uterus for potential implantation - after ovulation, progesterone from corpus luteum stabilizes lining - if fertilization does not occur, hormone levels drop - cause endometrial lining to shed

Question 35

what is the menstrual cycle

Answer 35

shedding of uteral lining

Question 36

how does birth control take advantage of hormonal regulation

Answer 36

combined birth control pill: contains synthetic estrogen and progestin (artificial version of progesterone) - work together to prevent pregnancy by suppressing ovulation - the constant level of estrogen and progestin provide a negative feedback to hypothalamus and pituitary which prevents LH surge that triggers ovulation - progestin thickens cervical mucus (difficult for sperm to reach egg) and thins endometrial lining (reduces chances of implantation) by maintaining stable hormone levels, pill overrides natural menstrual cycle and prevents hormone fluctuations needed for follicle development and ovulation there are progestin only birth control pills but no estrogen only birth control pills as by itself it is a carcinogenic`

Question 37

hormonal changes in menopause

Answer 37

change in hormone levels occur because ovaries stop responding to signals from the brain - primarily due to depletion of ovarian follicles and reduced hormone production

Question 38

what is menopause

Answer 38

the natural decline in reproductive hormones that occurs to people with ovaries happens at the 45-55 yr mark marks the end of ovulation and menstrual cycles

Question 39

GnRH during menopause

Answer 39

- still released by the hypothalamus - has no major changes but become less effective because the ovaries don't respond to stimulation

Question 40

FSH changes during menopause

Answer 40

- increases significantly - tries to stimulate the ovaries but they no longer respond due to follicle depletion

Question 41

LH changes during menopause

Answer 41

- increases significantly - no ovulation occurs, despite the high levels

Question 42

estrogen changes during menopause

Answer 42

- decreases - leads to symptoms like hot flashes, mood changes and bone loss

Question 43

progesterone changes during menopause

Answer 43

- decreases - no ovulation means no corpus luteum, so less progesterone is produced

Question 44

why do hormones change during menopause

Answer 44

- due to ovaries becoming less responsive to FSH and LH as a person with ovaries ages 1. ovarian follicle depletion females are born with finite number of follicles, overtime they are lost through ovulation and natural degeneration (atresia). - by menopause almost no functional follicles remain so the estrogen and progesterone production stops 2. loss of estrogen and progesterone productions - estrogen produced by developing follicles -- fewer follicles = less estrogen - progesterone produced by corpus luteum. if no ovulation happening, corpus luteum is not produced

Question 45

why does FSH and LH increase but ovaries don't respond during menopause

Answer 45

normal: high estrogen provides negative feedback to the brain to regulate FSH and LH with low estrogen, this feedback loop fails so pituitary release more FSH and LH to try and stimulate the ovaries but ovaries do not respond because no functional follicles remain and ovarian cells become less sensitive to hormonal signals

Question 46

effects of menopause in body

Answer 46

- hot flashes and night sweats (hypothalamus misinterpreting body temp) - irregular or absent periods (ovulation stops, therefore menstrual cycles is irregular/stops) - bone loss/ osteoporosis risk (estrogen helps maintain bone density so higher chances of fractures - mood changes and sleep disturbances (estrogen affects neurotransmitters in brain, influencing mood and sleep) - vaginal dryness and changes in skin (estrogen maintains vaginal and skin elasticity so its loss can cause dryness and thinning)