Gametes - Female Reproduction Flashcards
What are the ovaries the site of
Oocyte production
Hormonal production
What are the 3 types of mammalian reproductive patterns
- Induced ovulators - copulation induced oocyte release
- Cyclical ovulators - oestrus cycle is characterised by period of heat
- Menstrual cycle - menstrual bleeding, shedding of endometrium of uterus, in the absence of fertilisation
Diagram of egg maturation in the ovary
What is formed with the secondary follicle
fluid that bathes the oocyte - follicular fluid
Rich in nutrients and growth factors (not the same as blood)
Which is the largest follicle
Graafian follicle
What is the composition of the layer that surrounds the egg
Glycoprotein - stays there until 7 days after fertilisation when the embryo hatches out of zona pellucida (early embryonic loss due to premature hatching)
What is the oocyte released with
What is this an indicator of
Released with cumulus cells
Good indicator of healthy egg
What happens to the cells that remain
Enriched with lipid and cholesterol to form the CORPUS LUTEUM
- remain there for 12 wks if pregnant
- regress if not pregnant to form scar tissue
Ovarian follicle growth - primordial follicle
1st degree oocyte
1 layer pre-granulosa cells
Ovarian follicle growth - primary follicle
Enlarged 1st degree oocyte
Zona pellucida
Ovarian follicle growth - pre-antral follicle
- Multiple layers of granulosa cells
- Oestrogen, FSH and LH receptors
- Differentiation of theca layers
- Androgens and LH receptors
What do theca cells produce
androgens
Role of uterus in female reproduction
- Myometrium forms part of the endometrium
- Endometrium
- Site of implantation
- Hormonally controlled development
Ovarian follicle growth - antral follicle (antrum formed)
Multiple layers of granulosa cells
2 thecal layers - externa & interna
What role doe the oviduct/fallopian tube play in female reproduction
It is a muscular wall ciliated (propels egg towards sperm) epithelium that is responsible for:
- Oocyte collection and oocyte/sperm transport
- Site of fertilisation
- Early embryonic development (1st 3 days)
Define placenta pravea
As the foetus enlarges, it can block the birth canal
What will happen to the vast majority (99%) of immature oocytes (formed in foetus)
They will degenerate - atresia
Name the shadow seen in this image
Zona pellucida
1st polar body is seen
Overview of oogenesis
Follicular/proliferative phase of cycle
- 1-14
- Follicle changes - FSH action @ day 5
- Follicle growth and development begins
- Oestrogen secretion dominates
UTERINE CHANGES
Days 1-5 - absence of fertilisation endometrium shedding
Days 5-14 - increase in endometrial glands & BVs
** under influence of increased oestrogens
Follicular growth and development
What are the changes to the oocyte in the follicular phase of the cycle (day 1-14)
- 1-13: primary oocyte arrested @ prophase I
- 14, just before ovulation:
- Primary oocyte completes meiosis I
- Secondary oocyte and 1st polar body
OVULATION
- LH action
- 14: graafian follicle ruptures
- Release of secondary oocyte - picked up // fimbria
- Propelled up fallopian tube
What substance tells your body that you’re pregnant
Interferon tau
What is formed in the luteal/secretory phase (days 15-28)
What are the uterine changes
CORPUS LUTEUM FORMATION
- Site of ovulation: follicle collapses and granulosa cells luteinise
- Corpus luteum: progesterone secretion rises, increase in steroid producing tissue (ug -> mg) - production is by the cells that remain and are filled with lipid and cholesterol, then comes from placenta
UTERINE CHANGES
- Progesterone action increases secretion in uterine glands
What is the fate of the oocyte & uterine changes in the luteal phase (days 15-28)
FATE OF OOCYTE
-
Fertilisation: in fallopian tube
- oocyte activated - meiosis II - 2nd polar body
- Fertilised ovum develops zygote
-
No fertilisation:
- Degeneration of secondary oocyte
UTERINE CHANGES
-
Fertilisation:
- CL maintained until placenta functioning @ 12 weeks
-
No fertilisation:
- CL regression - menstrual bleeding
HPO Axis - follicular vs luteal phase
What is LH responsible for
Ovulation
Define leutinisation
Mature ovarian follicle is infiltrated with lipid and cholesterol, becomes yellow and corpus luteum is formed
What does the corpus luteum (formed in leutinisation) produce
Progesterone at high levels
Changes in
- GnRH
- FSH
- LH
- Oestrogen
- Inhibin
- Progesterone
during the ovarian cycle
What unique property does progesterone have
It is thermogenic
What does inhibin inhibit
FSH alone
Relationship between oestrogen (from follicle) and GnRH
Oestrogen increases GnRH
Oestrogen and LH surge in ovarian cycle
What are the hypothalamic hormones
Describe the functions of the hormones
GnRH
Stimulates production of FSH and LH
What are the anterior pituitary hormones
Describe the functions of the hormones
FSH - promote androgen and oestrogen production
LH - promote androgen and oestrogen production
what are the ovarian hormones
Describe the functions of these hormones
Oestrogen predominates in follicular phase
Progesterone predominates in luteal phase
inhibin/activin regulates FSH secretion
FSH’s role in follicle growth
Essential from PRE-ANTRAL stage
Primordial -> antral happens without FSH
FSH’s role in oestrogen levels
2 CELL THEORY
With LH, it increases oestrogen secretion
Stimulate aromatase activity in granulosa cells
Converts androgens to oestrogen
FSH’s role in altering LH activity
Increases LH receptors on ovary tissue
The granulosa cells of dominant follicle sensitise ovarian cells to LH action
2-cell-2-gonadotropin theory
What are the regulatory mechanisms of androgen production by theca cells
What is a possible cause of polycystic ovarian syndrome
Metabolic problems
=> body fat, glucose etc affect reproduction
LH’s role in ovulation
RUPTURE OF DOMINANT FOLLICLE
- Increased prostaglandin secretion
- Increased progesterone secretion
- Increased enzyme activity
Lh’s role in oestrogen secretion
On theca cells, there is in an increase in androgen levels indirectly caused by the increase in oestrogen secretion
What hormone helps in formation of corpus luteum
Describe the change in cells
What does the corpus luteum secrete
LH
Granulosa cells become luteal cells
Secrete progesterone
What effect does LH have on the oocyte
Resumption of meiosis
Effect of LH on blood flow
Increased ovarian blood flow
90% to corpus luteum (via prostaglandin)
5 functions of LH
- Ovulation
- Oestrogen secretion
- Corpus luteum formation
- Stimulates resumption of meiosis in oocyte
- Increased ovarian blood flow
Consequences of LH surge
What happens at ovulation
How are oestrogen and progesterone formed
Name the 3 different types of oestrogens
17 β-oestradiol
Oestrone
Oestriol
How are oestrogens transported
In the blood, bound to
- Specific Sex Steroid Binding Globulin (SSBG)
- Albumin
Serum conc of D1
2-8 μg/100ml
Serum conc of D14
12-48 μg/100ml
Serum conc of D21
9-30 μg/100ml
What sort of steroid is oestradiol
C-18 steroid
How does oestrogen production vary in women throughout their life
Effect of oestrogen on foetal development
Helps in formation of uterus, oviduct, cervix, vagina
Effect of oestrogen on the endometrium during the follicular phase
Increased number and size of endometrial glands
Increased blood vessel growth (Angiogenesis)
Increased progesterone receptors
Effect of oestrogen on uterine smooth-muscle
Increased contractility aids in sperm transport
effect of oestrogen and cervical mucus
Makes it aqueous and alkaline which facilitates sperm transport
4 uterine and ovarian effects of oestrogens
- Fetal development
- Changes in endometrium during the follicular phase
- contractility of uterine smooth-muscle
- cervical mucus
Other effects of oestrogens
- Female appearance - hair distribution & fat deposition
- Salt and water retention via increased Ang (activating RAS)
- Growth of ducts in breast tissue
- Bone conservation
- Lipoproteins - increased HDL, Decreased LDL and vLDL
- Gonadotrophins:
- +ve feedback in the follicular phase
- -ve feedback in luteal phase
Oestrogens and gonadotrophins
Positive feedback - follicular phase
Negative feedback - luteal phase
Changes in lipoproteins due to oestrogens
Increased HDL
Decreased LDL
Decreased vLDL
Synthesis of progesterone
Cholesterol → Pregnenalone → Progesterone
What are the sites of synthesis of progesterone
Corpus luteum
Placenta
Rate of secretion of progesterone during the follicular phase
5 mg/day
Rate of secretion of progesterone mid-luteal phase
32 mg/day
From the CORPUS LUTEUM
Rate of secretion of progesterone during the last trimester
300 mg/day
From PLACENTA
4 Uterine and ovarian effects of progesterone
- Endometrium - luteal phase
- Uterine smooth muscle
- Cervical mucus
- Embryo survival
Effect of progesterone on the endometrium (luteal phase)
Differentiation of endometrium into scretory glands
Effect of progesterone on uterine smooth muscle
Decreased contractility
Effect of progesterone on cervical mucus
Thickened and acidic - contains glycogen
Hinders sperm entry - provides energy to developing embryo
Effect of progesterone on embryo survival
Enhances the chances of embryo survival
Name 4 other effects of progesterone
- Breast tissue - increases alveolar tissue
- Thermogenic - increases body temp by 0.2-0.5 degrees C
- Increases resp rate
- Decreases both LH and FSH (both GONADOTROPHINS) secretion at high conc
Production rate of sex steroids in women at different stages of the menstrual cycle
MCQ
Benefits of ovarian tissue cryopreservation
Ovarian stimulation not performed
Acquire hundreds of immature oocytes
Less delay in commencement of cancer treatment
Concerns with ovarian tissue cryopreservation
Reimplantation - risk of recurrence
How to develope the immature oocytes
- need lots of O2 but too much results in ROS
