Reproductive System

Question 1

Internal Reproductive Organs:
What are the female ducts?
→ What do they form?
→ What are they inhibited by?

What are the male ducts?
→ What do they form?
→ What are they stimulated by?
→ What are they inhibited by?

External Reproductive Organs:
What occurs here for it to form?

Answer 1

➊ Mullerian ducts
→ Uterine tubes, Uterus, Upper 1/3 Vagina
→ AMH (from Sertoli cells) in males

➋ Wolffian ducts
→ Epididymis, Vas Deferens, Seminal vesicles, Ejaculatory ducts
→ Testosterone
→ Lack of Testosterone (from Leydig cells) in females

➌ Testosterone is converted into DHT by 5-α-Reductase
• DHT binds to testosterone receptor with ↑efficacy (↑POTENT) → differentiation into male external genitalia

Question 2

Gonadotrophins:
How do they affect the ovaries?

How do they affect the testes?

Answer 2

➊ • FSH causes Follicular maturation and growth
‣ FSH receptors on Granulosa cells Oestrogen synthesis
‣ LH receptors on Theca cells = Androgen synthesis
• When Oestrogen is high for a few days, there’s a temporary switch, causing LH surge → Ovulation
• Corpus Luteum is rescued by hCG in pregnancy

➋ • FSH receptors on Sertoli cells = Oestrogen synthesis
• LH receptors on Leydig cells = Testosterone synthesis

Question 3

Follicle:
What is the structure of the Primordial Follicle?

How does Folliculogenesis occur?

Answer 3

➊ Oocyte surrounded by protective layers of Granulosa cells and the Basal Lamina

➋ • Folliculogenesis is driven mostly by FSH, but early growth is independent of FSH (driven by local factors)
‣ Even with FSH suppression (e.g. with Combined Oral Contraceptive), follicles continue with early growth, but then die
• As it grows, the Granulosa cells divide even more, forming gaps in the layers, which fill with follicular fluid to form an Antrum = Antral/Secondary Follicles
• Follicle Initiation and Recruitment - Cohort of early follicles leave the resting pool and grow continuously. They won’t continue to grow until they reach a sufficient size to respond to changes in FSH during the menstrual cycle
• Only 1 follicle from the pool will be selected for Ovulation

Question 4

Ovulation:
What causes it to occur?
→ What occurs during this?

Answer 4

➊ LH surge
→ • Basement membrane breaks so blood pours into the middle - Oocyte-Cumulus complex breaks off and is caught by Fimbrae
• Theca and Granulose cells become mixed, forming the Corpus Luteum

Question 5

Luteal Phase:
What is mainly produced here?
→ What’s the effect of this?

What else is produced?
→ What’s the effect of this?

What occurs after ovulation if there’s no pregnancy?
→ How does this change in pregnancy?

What’s the end stage of the oocyte?

Answer 5

➊ Progesterone
→ • Readies endometrium for implantation
• Thickens cervical mucous to prevent further sperm penetration
• Suppresses cilia in Uterine tubes once Oocyte has passed

➋ Oestrogen
→ Maintains endometrium

➌ CL has a finite lifespan of 14 days if no fertilisation occurs - Regression and fall in progesterone occurs, which is necessary to initiate new cycle (Inter-cycle rise in FSH)
→ CL rescued in pregnancy by hCG, which binds to LH receptors for more Progesterone production

➍ Apoptosis, Vasculature breakdown, and CL shrinks to become a Corpus Albicans