L39, 40, 41 Ovarian function, pregnancy, reproduction, contraception Flashcards
(170 cards)
1
Q
What are gonads?
A
Organs that produce gametes – ovaries in females, testes in males.
2
Q
What is the female gamete called?
A
Oocyte (egg).
2
Q
What is a gamete?
A
A mature reproductive cell with a haploid set of chromosomes.
3
Q
What are germ cells?
A
Reproductive cells (sperm or oocyte) or their developmental precursors.
4
Q
Where do primordial germ cells originate?
A
In the epithelium of the yolk sac (around week 3).
4
Q
When does gonadal development become sex-specific?
A
Week 7 of embryonic development.
5
Q
How do PGCs migrate to the genital ridges?
Primordial germ cells
A
Via amoeboid movement, guided by chemotaxis.
6
Q
What happens if PGCs don’t reach the genital ridges?
A
They may become tumourigenic.
tendency to produce tumours
7
Q
What is the default developmental pathway?
A
Female, due to absence of the SRY gene on the Y chromosome.
8
Q
What are the three influxes of cells in ovary formation?
A
- Sex cord cells → granulosa cells
- PGCs → oogonia
- Mesonephric cells → theca cells and vasculature
9
Q
What is the developmental path of female germ cells?
A
PGC → Oogonium → Primary oocyte → Secondary oocyte → Mature oocyte (if fertilised)
10
Q
When does oogenesis begin and pause in females?
A
Begins in fetal life; pauses in prophase I (first meiotic block) until puberty.
11
Q
When does the second meiotic block occur?
A
After ovulation in metaphase II; only completes if fertilised.
12
Q
How many oocytes are ovulated in a lifetime?
A
Around 400.
13
Q
Why are meiotic divisions in oogenesis asymmetrical?
A
To retain most of the cytoplasm in the oocyte and discard excess genetic material.
14
Q
What signifies fertilisation?
A
Presence of a second polar body.
Sperm. Not to be confused with the polar bodies that come from the oocyte
15
Q
What are the stages of follicular development?
A
- Primordial Follicle:
- Formed in the foetus: oogonia surrounded by sex cord cells.
- Oogonia enter meiosis I but arrest in prophase I (first meiotic block) to become oocyte.
- Each is enclosed in a primordial (squamous) follicle.
- Females are born with ~1–2 million; only ~400 ovulate in a lifetime.
- Primary Follicle (Pre-antral):
- Oocyte remains arrested in prophase I.
- Follicle becomes cuboidal granulosa cells but is still hormone-independent.
- The zona pellucida (a glycoprotein layer) forms around the oocyte.
- Secondary Follicle (Early Antral):
- Begins at puberty: FSH and LH stimulate further development.
- Granulosa cells proliferate into multiple layers.
- Theca cells begin to develop around the follicle.
- Meiosis I completed, forming:
- A secondary oocyte (enters meiosis II and arrests at metaphase II — second meiotic block).
- A first polar body (discarded DNA).
- Tertiary (Graafian/Antral) Follicle:
- Fully mature follicle. A large antrum (fluid-filled space) forms.
- Ovulation releases the secondary oocyte into the fallopian tube.
- If fertilised, the oocyte completes meiosis II, forming:
=A mature ovum (haploid)
=A second polar body
- If not fertilised, the oocyte degenerates.
16
Q
What does the HPG axis stand for?
A
Hypothalamus–Pituitary–Gonadal axis.
16
Q
What is the zona pellucida and its functions?
A
A glycoprotein layer that:
Binds sperm
Triggers the acrosome reaction
Prevents polyspermy
Protects the embryo
17
Q
What does GnRH do?
A
Stimulates the pituitary to release FSH and LH.
18
Q
What does FSH do in females?
A
Stimulates follicle growth.
19
Q
What does LH do in females?
A
Stimulates ovulation and corpus luteum formation.
20
Q
What triggers puberty hormonally?
A
Kisspeptin stimulates GnRH release.
21
Q
What links body weight to puberty?
A
Leptin – needed for puberty onset; mutations in the leptin gene delay it.
22
How is oestrogen synthesised in the ovary?
Theca cells produce testosterone under LH stimulation.
Granulosa cells convert testosterone to oestrogen using aromatase (FSH-controlled).
23
What are the three phases of the menstrual cycle?
Follicular/Proliferative
Ovulatory
Luteal/Secretory
24
What causes the LH surge and ovulation?
Rising oestrogen levels from the dominant follicle.
25
What happens post-ovulation?
Corpus luteum forms, secreting progesterone and oestrogen.
26
What maintains the corpus luteum during early pregnancy?
hCG produced by the syncytiotrophoblast (vili in the placenta allowing exchange of nutrients)
27
When does the placenta take over hormone production?
Around 7 to 10 weeks of gestation, during the luteal-placental shift, the placenta assumes production of progesterone and oestrogen from the corpus luteum.
28
What happens if no fertilisation occurs?
Corpus luteum degenerates (luteolysis), hormone levels drop, and menstruation begins.
29
What guides PGCs to the genital ridge during development?
Chemotaxis – a chemical signalling gradient.
30
What can happen if PGCs don't reach the genital ridge?
They may develop into teratomas (rare type of germ cell tumor that may contain immature or fully formed tissue, including teeth, hair, bone and muscle) , particularly in midline structures.
31
What gene is essential for meiosis initiation in females?
Stra8 (Stimulated by Retinoic Acid gene 8).
32
What allows females but not males to enter meiosis during fetal life?
Retinoic acid accumulates in females; males break it down using cytochrome P450 enzymes.
33
Why is female fertility affected by age?
Oocytes are arrested in prophase I for decades, increasing risk of chromosomal errors like nondisjunction.
34
Which condition is associated with maternal age and meiotic errors?
Trisomy 21 (Down syndrome).
35
What is follicular atresia?
The degeneration of follicles that do not reach full maturity.
36
Q: How is the dominant follicle selected?
It has higher FSH sensitivity and continues to develop even as FSH levels drop due to rising oestrogen.
37
How does oestrogen regulate FSH levels?
Via negative feedback early in the cycle; high levels later trigger LH surge through positive feedback.
38
What role does inhibin play in hormonal control?
Secreted by granulosa cells, it selectively inhibits FSH release.
39
What is the receptor for GnRH and where is it found?
GnRHR (a GPCR), found on pituitary gonadotrophs.
| cells that secrete FSH and LH
40
Where are FSH and LH receptors expressed in the ovary?
FSHR: Granulosa cells
LHCGR: Theca cells and granulosa cells (later in dominant follicle)
| luteinizing hormone/chorionic gonadotropin receptor
41
What receptor does kisspeptin bind to?
KISS1R (GPR54).
42
What disorder is linked to mutations in KISS1R?
Hypogonadotropic hypogonadism – delayed or absent puberty.
43
43
43
44
44
What are the hormonal changes during the menstrual cycle?
1. FSH ↑ → follicle growth
2. Oestrogen ↑ → FSH ↓
3. Oestrogen peaks → LH surge
4. LH surge → ovulation
5. Corpus luteum → progesterone ↑
6. No fertilisation → hormones ↓ → menstruation
45
46
47
Why can pregnancy tests detect hCG early?
hCG is secreted by the embryo's syncytiotrophoblast, and detectable in urine within days.
48
How is hCG similar to LH?
Both share the same α-subunit, allowing hCG to bind LHCGR.
49
What are the three main types of oestrogen and when do they predominate?
Oestradiol (E2) – active during reproductive years
Oestriol (E3) – pregnancy
Oestrone (E1) – post-menopause
50
Which oestrogen is the most potent?
Oestradiol (E2).
51
What side effects can synthetic progestins have?
Androgenic effects (e.g., acne) due to binding to androgen receptors.
52
What is mifepristone (RU486) and how does it work?
An anti-progestagen that acts as an antagonist at progesterone receptors – used in medical termination.
53
How does GnRH pulse frequency influence hormone production?
Medium pulses → FSH secretion
Rapid pulses → LH secretion
53
What other embryological structures are involved in gonad development?
The mesonephros (temporary, intermediate kidney structure that develops in vertebrate embryos) contributes mesonephric cells which become theca cells and part of the ovarian vasculature.
54
Why must GnRH secretion be pulsatile?
Constant GnRH leads to desensitisation/downregulation of GnRH receptors, halting FSH/LH production.
54
What type of neurons produce GnRH?
Parvocellular neurosecretory neurons in the hypothalamus.
55
What happens to granulosa cells in the dominant follicle?
They acquire LHCGR expression in preparation for the LH surge.
56
What structural specialisation occurs near ovulation?
Cumulus oophorus forms, anchoring the oocyte, and corona radiata surrounds the oocyte directly.
57
What are the two luteal cell types, and what do they produce?
Granulosa lutein cells → progesterone & oestrogen
Theca lutein cells → androgens (later aromatised)
58
Through what mechanism do LH and FSH exert their effects?
Via G-protein coupled receptors (GPCRs) that activate adenylyl cyclase, increasing cAMP.
59
What causes the follicle wall to rupture during ovulation?
Proteolytic enzymes weaken the wall (esp. at the stigma)
Increased follicular pressure from fluid
Cumulus expansion loosens the oocyte
60
What causes luteolysis in the absence of fertilisation?
Lack of hCG, leading to fall in LH support → luteal degeneration → hormone levels drop → menstruation
61
How do GnRH agonists and antagonists differ in clinical use?
Agonists: Initially stimulate, then suppress gonadotrophins (used in IVF, endometriosis)
Antagonists: Immediately suppress FSH/LH (also used in fertility treatments)
62
Why are aromatase inhibitors relevant to oestrogen?
Block conversion of androgens to oestrogens – used in breast cancer treatment.
62
What hormone promotes endometrial proliferation during the follicular phase?
Oestrogen
63
What does progesterone do in the luteal phase of the menstrual cycle?
Induces secretory transformation (decidualisation) to prepare endometrium for implantation.
64
What is histiotrophic nutrition?
Nourishment of the early embryo via endometrial gland secretions before placental formation.
65
How does the embryo move from the fallopian tube into the uterus?
Increased progesterone:oestrogen ratio relaxes the isthmic sphincter.
66
What is the implantation window?
Days 20-24 of the cycle when the endometrium is most receptive.
67
Q: What is the first hormone secreted after implantation?
hCG (by syncytiotrophoblast ~1 week post-fertilisation).
68
What is the role of hCG in early pregnancy?
Maintains the corpus luteum for continued progesterone secretion.
69
When does hCG peak and decline?
Peaks around week 8, then declines but remains detectable.
70
What is a biochemical vs clinical pregnancy?
Biochemical: hCG detected (~week 1); Clinical: ultrasound evidence (~week 6)
71
What hormone is essential to maintain pregnancy and how is it produced?
Progesterone; initially by corpus luteum, then placenta (~week 6)
72
What is the predominant oestrogen in pregnancy?
Oestriol.
72
How is oestrogen synthesised during pregnancy?
Progesterone (placenta) → Androgens (foetal adrenal) → Oestrogen (placenta).
72
What drug blocks progesterone action?
Mifepristone (RU486).
73
What is hPL and its role?
Human placental lactogen (chorionic somatomammotropin); anti-insulin, increases glucose and lipolysis.
74
# *
What hormone prepares for lactation during pregnancy?
Prolactin (PRL), stimulated by oestrogen.
75
What are the stages of labour?
1. Cervix effacement/dilation,
2. Baby delivery,
3. Placenta delivery.
76
What hormones mediate cervical ripening?
Prostaglandin E (PGE), relaxin, nitric oxide (NO).
77
What suppresses contractions during pregnancy?
Progesterone reduces oxytocin receptor expression.
78
What causes contractions at term?
Rising oestrogen:progesterone ratio increases oxytocin receptor expression.
79
Where is oxytocin produced and what does it do?
Synthesised in the hypothalamus, secreted by posterior pituitary; stimulates uterine contractions.
79
What is the Ferguson reflex?
Baby’s head stretches cervix → oxytocin release → more contractions (positive feedback).
79
What fetal signals initiate labour?
Maturation of fetal HPA axis, CRH and cortisol increase → oestrogen and prostaglandin production.
80
What role does cortisol play?
Promotes surfactant synthesis for lung maturation.
81
What is dexamethasone used for?
To induce lung maturation in preterm labour.
82
What are the main components of the breast involved in lactation?
Lobes with alveoli (epithelial and myoepithelial cells), lactiferous ducts.
83
What promotes duct development at puberty?
Oestrogen.
84
What promotes alveolar development during pregnancy?
Oestrogen and progesterone.
85
Why does milk not secrete before birth?
Progesterone inhibits prolactin responsiveness.
86
What hormonal changes allow milk secretion postpartum?
Drop in oestrogen/progesterone, sustained prolactin.
87
What triggers the let-down reflex?
Nipple stimulation → oxytocin release → contraction of myoepithelial cells.
88
What is lactational amenorrhoea?
| no period
High prolactin suppresses FSH/LH → prevents ovulation.
89
When is lactational amenorrhoea effective as contraception?
First 6 months postpartum if exclusively breastfeeding and amenorrhoeic.
90
What is perimenopause?
Transition period before menopause; symptoms include hot flushes, mood changes, irregular cycles.
90
What are the stages of oocyte decline?
8wks: 600k → 20wks: 7M → Birth: 2M → Puberty: 400k → ~400 ovulated.
90
What defines menopause?
≥ 50: 12 months amenorrhoea; <50: 24 months.
91
Which oestrogen predominates post-menopause?
Oestrone (from adrenals and adipose).
92
Consequences of oestrogen withdrawal?
Osteoporosis, coronary disease risk, vaginal dryness, behavioural changes.
93
What is HRT and when is it used?
Hormone Replacement Therapy; used to manage menopausal symptoms.
93
What are HRT risks?
Breast cancer, cardiovascular disease.
93
Who can use oestrogen-only HRT?
Women post-hysterectomy (otherwise risk of endometrial cancer).
94
What are the 5 main types of contraception?
Hormonal, Barrier, IUDs, Permanent, Natural.
95
What is the Pearl Index?
Number of contraceptive failures per 100 woman-years. E.G If 100 women use condoms and 3 get pregnant then the index is 3.
96
How do hormonal methods of contraception work?
Suppress HPG axis, thicken cervical mucus, thin endometrium.
97
What are the key hormonal changes in early pregnancy?
Oestrogen (follicular phase): promotes endometrial proliferation.
Progesterone (luteal phase): induces secretory changes in the endometrium for implantation (decidualisation).
hCG: secreted by syncytiotrophoblast ~1 week after fertilisation; maintains the corpus luteum for progesterone production until placenta takes over (~week 6).
98
What does the placenta produce to maintain pregnancy?
Progesterone: Maintains endometrium and suppresses myometrial contractions.
Oestrogen (mainly oestriol): Promotes uterine growth and blood flow.
hPL (human placental lactogen): Increases maternal glucose and lipolysis for fetal nutrition (anti-insulin effect).
Prolactin: Prepares breast for milk synthesis (stimulated by oestrogen).
99
What hormonal changes initiate parturition (labour)?
Increased oestrogen:progesterone ratio → upregulation of oxytocin receptors.
Oxytocin: from posterior pituitary and decidua, stimulates uterine contractions.
Prostaglandins (PGE): soften cervix (cervical ripening) and enhance contractions.
Fetal HPA axis: releases CRH and cortisol, triggering placental oestrogen and prostaglandin production.
100
What hormones are involved in breast development and milk production?
Oestrogen: stimulates ductal growth during puberty and pregnancy.
Progesterone: promotes alveolar development but blocks milk secretion pre-birth.
Prolactin (PRL): promotes milk synthesis, rises during pregnancy and stimulated by suckling postpartum.
Oxytocin: triggers milk ejection via contraction of myoepithelial cells (let-down reflex).
101
What happens to hormone levels after birth?
Oestrogen and progesterone drop suddenly (placenta removal).
Prolactin levels remain high, maintained by suckling (positive feedback).
Oxytocin continues to be released with nipple stimulation.
102
What is lactational amenorrhoea and its hormonal basis?
High prolactin levels suppress GnRH, leading to low FSH/LH and inhibition of ovulation.
Effective as contraception (98%) if exclusively breastfeeding and mother remains amenorrhoeic within the first 6 months postpartum.
103
What is menopause?
The permanent cessation of menstruation due to ovarian follicle depletion.
Defined as 12 months of amenorrhoea if ≥50 years old, or 24 months if <50.
Average age in the UK: 51 years.
104
What are hormonal changes during menopause?
↓ Oestrogen (mainly oestradiol)
↑ FSH and LH (due to loss of negative feedback)
Oestrone becomes the predominant oestrogen (from adrenals/adipose).
105
What are clinical consequences of oestrogen withdrawal?
Bone loss (↑ risk of osteoporosis)
Cardiovascular risk (altered lipid profile)
Urogenital symptoms (vaginal dryness, dyspareunia)
Mood changes and hot flushes
106
What is HRT and who should receive it?
Hormone Replacement Therapy replaces lost oestrogen ± progesterone.
Oestrogen-only HRT: for hysterectomised women.
Combined HRT: for women with a uterus to prevent endometrial hyperplasia.
Risks: Breast cancer, CVD, endometrial cancer.
107
What is contraception?
The intentional prevention of pregnancy, allowing individuals to control if/when they conceive.
108
What are the five main categories of contraception?
Hormonal: Suppresses ovulation (e.g. COCs, POPs, implant, injections).
Barrier: Prevents sperm-egg interaction (e.g. condoms, diaphragm).
IUDs: Prevent fertilisation/implantation (Copper or LNG-releasing).
Permanent: Surgical sterilisation (e.g. vasectomy, tubal ligation).
Natural: Based on fertility awareness, withdrawal, or lactational amenorrhoea.
109
What is UKMEC?
The UK Medical Eligibility Criteria – guidelines for safe contraceptive use based on health status (e.g. age, CVD risk, migraine).
110
What are the three major categories of ovarian tumors? Which is the most common
Surface epithelial tumors(most common)
Germ cell tumors
Sex cord-stromal tumors
111
Name the two most common types of surface epithelial tumors.
Serous tumors
Mucinous tumors
112
What are the three subtypes of serous ovarian tumors?
Benign (serous cystadenoma)
Borderline (atypical proliferative)
Malignant (serous cystadenocarcinoma)
113
What are psammoma bodies and where are they typically found?
| Carcinomas are epithelial cell cancers
Psammoma bodies are concentric calcifications commonly found in serous carcinomas.
114
What differentiates mucinous tumors from serous tumors in appearance?
Mucinous tumors are typically multiloculated with mucin-filled cysts, whereas serous tumors are often unilocular and contain watery fluid.
115
# *
What condition is associated with mucinous tumors spilling into the peritoneum?
Pseudomyxoma peritonei
116
What is a Brenner tumor?
A rare, benign surface epithelial-stromal tumor with transitional cell (urothelial-like) epithelium.
117
What is the most common type of germ cell tumor in the ovary?
Mature cystic teratoma (dermoid cyst)
118
What are the components of a teratoma?
Tissues from all three germ layers: ectoderm, mesoderm, and endoderm.
119
When does menarche typically occur and what is its nature early on?
Average age: 12.5 years (95% range: 11-15 years)
Early menstruation is often irregular and anovulatory(where an egg isn't released)
120
What defines precocious puberty and what are its causes and treatments?
SSC before 8 years, menarche before 10 years
Causes: Constitutional or neurological/tumors
Leads to early growth spurt, early epiphyseal fusion → short stature
Treatment: GnRH agonists, progestins, growth hormone
121
What defines delayed puberty and what are potential causes?
No menstruation by 16 yrs (with SSC) or by 14 yrs (without SSC)
Causes: Haematocolpos (imperforate hymen), vaginal agenesis, resistant ovary syndrome, H-P axis issues, constitutional
| Secondary sexual characteristics - breasts etc
121
Define the following menstrual disorders:
1. Amenorrhea
2. Oligomenohhrea
1. Amenorrhea: Absence of menstruation
→ Primary: Never started
→ Secondary: Ceased for ≥6 months
2. Oligomenorrhea: Irregular cycles (<9 per year)
121
What are clinical presentations of ovarian dysfunction?
* Oligomenorrhea, amenorrhea, infertility
* Oestrogen deficiency: Hot flushes, poor libido, dyspareunia
* Hyperandrogenism: Hirsutism, acne, androgenic alopecia
* Others: Weight changes, galactorrhoea
122
Diagnostic steps in evaluating ovarian dysfunction:
1. Pregnancy test
2. Hormonal tests:
- FSH/LH (Day 2/3) for ovarian reserve & HPG axis
- Progesterone (Day 21) to confirm ovulation
3. Progesterone Challenge Test:
- Medroxyprogesterone acetate for 5 days
- Withdrawal bleed in 2-7 days indicates functional endometrium & normal oestrogen
123
Causes of primary ovarian failure:
* Ovarian insensitivity or damage (gonadotropins normal, high FSH/LH due to lack of oestrogen feedback)
* Causes:
- Premature ovarian failure (Primary ovarian insufficiency)
- Turner’s Syndrome (XO)
- Chemo-/radiotherapy-induced ovarian damage
124
Central causes of ovarian dysfunction:
* Hyperprolactinemia: ↑ serum prolactin → suppresses FSH/LH
- Causes: Prolactin-secreting tumors, pituitary stalk compression
- Treatment: Surgery or dopamine agonists
* Kallman Syndrome: Genetic defect; GnRH neurons fail to migrate
* Lifestyle Factors: Anorexia, excessive exercise, obesity, stress (HPG axis suppression)
125
What is PCOS? Full overview
* Most common endocrine disorder in premenopausal women (~10%)
* Symptoms: Oligo-/amenorrhea (80%), hirsutism (excess hair mostly around mouth and chin)(30%), obesity (40%), infertility (30%)
* Biochem: ↑ Androgens (testosterone, androstenedione), ↑ LH:FSH ratio, possible insulin resistance
* Diagnosis (Rotterdam Criteria - 2 of 3):
- Oligo-/amenorrhea
- Clinical/biochemical hyperandrogenism(excessive amounts of androgen hormone)
- Polycystic ovaries on ultrasound (>=12 cysts, 2-9 mm, >10 ml volume)
126
Premature Ovarian Failure (Primary Ovarian Insufficiency) overview:
Amenorrhea, low oestrogen, high FSH/LH before age 40
Prevalence: 1% of women
Causes: Turner’s Syndrome (1:2500, 45XO), autoimmune, iatrogenic (chemo, radiation, surgery)
127
Requirements for fertility:
1. Normal sperm production
2. Normal egg production
3. Sperm reaches egg (capacitation, motility)
4. Fertilization of oocyte
5. Embryo implantation & pregnancy maintenance
128
Definition and stats on infertility (NICE):
Failure to conceive after 2 years of unprotected sex
Investigations start after 1 year
Affects 1 in 6 UK couples, 2.5% of births via fertility treatment (~15,000/year
129
Causes of infertility:
Female factors: Ovulatory disorders (60%), tubal damage, endometriosis, uterine issues
Unexplained (15%): Normal ovulation, no anatomical or male issues
Age-related: Female fertility drops after 35, male factors include diabetes, hypertension
130
Assisted conception options:
A. Ovulation Induction:
- Clomiphene citrate (anti-oestrogen), 5 days early in cycle → ↑ FSH → follicle development
-Risk: Multiple follicles, multiple births
B. Intrauterine Insemination (IUI):
- Sperm injected into uterus
- Indications: Cervical issues, same-sex couples, intercourse difficulties
- Success: 5-20%; multiple pregnancy: ~10%
C. In Vitro Fertilisation (IVF):
- 50,000-100,000 sperm with egg outside body
- ICSI (Intracytoplasmic Sperm Injection) for male factor infertility (1 sperm per egg)
D. Blastocyst Culture:
- Culture for 5-6 days before transfer → embryo selection
131
IVF Protocol Steps:
1. Pituitary suppression (GnRH agonist/antagonist)
2. Ovarian stimulation (rFSH) → multifollicular growth
3. Follicular monitoring
4. hCG trigger → final maturation
5. Egg collection (24h post-hCG)
132
IVF/ICSI Risks:
- Multiple pregnancy
- Ovarian Hyperstimulation Syndrome (esp. in PCOS)
- Maternal risks, congenital abnormalities, imprinting disorders
- Inheritance of male infertility (esp. via ICSI)
133
What is the difference between IVF and ICSI?
* IVF (In Vitro Fertilisation):
- Egg and ~50,000–100,000 motile sperm are placed together in a petri dish.
- Fertilisation occurs naturally (i.e. the sperm must reach and penetrate the egg on their own).
- Used when sperm count and motility are within acceptable range.
* ICSI (Intracytoplasmic Sperm Injection):
- A single sperm is injected directly into the cytoplasm of the egg using a fine needle.
- Used in severe male factor infertility (low count, poor motility, abnormal morphology) or after IVF failure.
134
When do primordial germ cells first appear in development?
A) Week 1
B) Week 3
C) Week 6
D) Week 8
Answer: ✅ Week 3
Explanation: PGCs originate in the yolk sac epithelium and appear around week 3.
135
How do PGCs reach the genital ridges?
A) Passive diffusion
B) Through vasculature
C) Amoeboid movement guided by chemotaxis
D) Via neuronal signalling
Answer: ✅ Amoeboid movement guided by chemotaxis
Explanation: PGCs migrate by amoeboid movement and are directed by chemical signals (chemotaxis).
136
What happens to PGCs that fail to reach the genital ridges?
A) They form oocytes elsewhere
B) They remain dormant
C) They are eliminated by apoptosis
D) They may form tumours like teratomas
Answer: ✅ They may form tumours like teratomas
Explanation: Misplaced PGCs may form germ cell tumours such as teratomas due to aberrant development.
137
What is the default pathway for gonadal development?
A) Male
B) Female
C) Intersex
D) Androgenic
Answer: ✅ Female
Explanation: In the absence of the Y chromosome and the SRY gene, the gonads develop as ovaries by default.
138
Which three cell types contribute to ovary formation?
A) Sertoli, Leydig, germ cells
B) Theca, granulosa, trophoblast
C) Sex cord cells, PGCs, mesonephric cells
D) Zona cells, luteal cells, stromal cells
Answer: ✅ Sex cord cells, PGCs, mesonephric cells
Explanation: These cell types form granulosa cells, oocytes, and theca/vascular support structures, respectively.
139
When does female meiosis begin?
A) At puberty
B) During ovulation
C) During fetal life
D) After implantation
Answer: ✅ During fetal life
Explanation: Female germ cells begin meiosis in the fetal period and arrest in prophase I until puberty.
140
What gene promotes meiotic entry in females?
A) SRY
B) FSHR
C) Stra8
D) GnRH
Answer: ✅ Stra8
Explanation: Stra8 (stimulated by retinoic acid) initiates meiosis in female germ cells.
141
What causes the second meiotic block in oocytes?
A) Progesterone suppression
B) Arrest at metaphase II
C) Low FSH
D) Zona pellucida thickening
Answer: ✅ Arrest at metaphase II
Explanation: After ovulation, the oocyte arrests at metaphase II and remains in this state until fertilisation.
142
What does the presence of a second polar body indicate?
A) Ovulation occurred
B) Fertilisation has taken place
C) Oocyte death
D) Endometrial shedding
Answer: ✅ Fertilisation has taken place
Explanation: The second polar body forms only when the oocyte completes meiosis II after fertilisation.
143
What is the role of granulosa cells in folliculogenesis?
A) Vascular development
B) Androgen production
C) Oestrogen synthesis from testosterone
D) Progesterone inhibition
Answer: ✅ Oestrogen synthesis from testosterone
Explanation: Granulosa cells convert theca cell-derived testosterone into oestrogen via aromatase.
144
Which follicular stage is gonadotrophin-dependent?
A) Primordial
B) Primary
C) Secondary
D) Pre-primordial
Answer: ✅ Secondary
Explanation: Secondary follicles require FSH and LH for further development and maturation.
145
What forms the cumulus oophorus and corona radiata?
A) Theca externa
B) Specialised granulosa cells
C) Mesonephric remnants
D) Zona pellucida
Answer: ✅ Specialised granulosa cells
Explanation: These granulosa cells directly surround and support the oocyte.
146
What is the zona pellucida composed of and what is its role?
A) Collagen, prevents ovulation
B) Lipid layer, insulates oocyte
C) Glycoproteins, mediates sperm binding and blocks polyspermy
D) RNA layer, supports meiotic division
Answer: ✅ Glycoproteins, mediates sperm binding and blocks polyspermy
Explanation: The zona pellucida is a protective glycoprotein layer critical for fertilisation control.
147
What is the main role of LH in the ovarian cycle?
A) Oocyte protein synthesis
B) Zona pellucida degradation
C) Stimulates ovulation and corpus luteum formation
D) Inhibits aromatase
Answer: ✅ Stimulates ovulation and corpus luteum formation
Explanation: The LH surge triggers ovulation and supports the formation of the progesterone-producing corpus luteum.
148
What role does FSH play in follicle development?
A) Stimulates progesterone synthesis
B) Activates Stra8
C) Promotes granulosa cell proliferation and aromatase activity
D) Suppresses meiosis
Answer: ✅ Promotes granulosa cell proliferation and aromatase activity
Explanation: FSH helps granulosa cells grow and produce oestrogen.
149
What structure produces oestrogen in early follicular development?
A) Corpus luteum
B) Granulosa cells (from theca testosterone)
C) Endometrial glands
D) Zona pellucida
Answer: ✅ Granulosa cells (from theca testosterone)
Explanation: Granulosa cells aromatise theca-derived testosterone into oestrogen under FSH influence.
150
Which phase is characterised by endometrial proliferation?
A) Ovulatory
B) Follicular (proliferative)
C) Secretory
D) Luteal
Answer: ✅ Follicular (proliferative)
Explanation: Oestrogen promotes regeneration and thickening of the endometrial lining during this phase.
151
What triggers the LH surge mid-cycle?
A) High progesterone
B) Inhibin release
C) Sustained high oestrogen levels (positive feedback)
D) GnRH inhibition
Answer: ✅ Sustained high oestrogen levels (positive feedback)
Explanation: Prolonged elevation of oestrogen causes a switch from negative to positive feedback, triggering the LH surge.
