Reproductive Physiology Practice Questions

Q: In this normal menstrual cycle graph, the mark 'X' represents levels of which hormone?

Progesterone. ***Progesterone*** - The mark 'X' (blue line) represents a hormone that significantly rises during the **luteal phase** after ovulation, reaching its peak around day 21-24 and then declining if pregnancy does not occur. - This pattern is characteristic of **progesterone**, which is primarily produced by the corpus luteum after ovulation to prepare the uterus for potential implantation. *LH* - **Luteinizing Hormone (LH)** is characterized by a sharp, transient peak just before ovulation (around day 14), which triggers the release of the egg. The blue line does not show this pre-ovulatory surge. - After ovulation, LH levels generally fall and remain relatively low throughout the luteal phase, unlike the sustained high levels shown by the blue line. *FSH* - **Follicle-Stimulating Hormone (FSH)** levels are typically higher during the early follicular phase, promoting follicle growth, and then decrease as estrogen rises. There is a smaller, transient peak around ovulation. - The blue line's profile, with its primary peak in the mid-luteal phase, does not match the typical FSH secretion pattern. *Estrogen* - **Estrogen** (specifically estradiol) typically shows a prominent peak during the late follicular phase, preceding the LH surge, and a secondary, smaller peak in the mid-luteal phase. - The blue line's peak is much higher and more sustained during the luteal phase than expected for estrogen, which is usually represented by the red curve in such graphs.

Q: Testosterone is secreted by:

Leydig cell. ***Leydig cell*** - **Leydig cells** are located in the **interstitial tissue** of the testes and are responsible for producing **testosterone** in response to **luteinizing hormone (LH)** stimulation. - They are the primary source of androgens in males, crucial for the development of male secondary sexual characteristics and spermatogenesis. *Granulosa cell* - **Granulosa cells** are found in the **ovarian follicles** and are primarily involved in the production of **estrogen** and **progesterone** in females. - They surround the oocyte and convert androgens (produced by theca cells) into estrogens. *Theca cells* - **Theca cells** are found in the **ovarian follicles** and produce **androgens** (mainly androstenedione) in response to **LH** stimulation. - These androgens are then converted to estrogens by the adjacent granulosa cells through aromatization. - While they produce androgens, they are not the primary source of testosterone in the body. *Sertoli cell* - **Sertoli cells** are located in the **seminiferous tubules** of the testes and provide structural and metabolic support for **spermatogenesis**. - They produce substances like **androgen-binding protein**, inhibin, and Müllerian inhibiting factor, but they do not secrete testosterone.

Q: Inhibin is secreted by:

Sertoli cells. ***Sertoli cells*** - **Sertoli cells** are located in the seminiferous tubules of the testes and play a crucial role in spermatogenesis. - They secrete **inhibin**, a hormone that selectively inhibits the secretion of follicle-stimulating hormone (FSH) from the anterior pituitary gland. *Peg cells* - **Peg cells** (non-ciliated secretory cells) are found in the lining of the fallopian tubes, not the testes. - They produce **tubal fluid** which nourishes the ovum and spermatozoa, and aids in sperm capacitation. *Leydig cells* - **Leydig cells** are found in the interstitial tissue between the seminiferous tubules of the testes. - Their primary function is to produce and secrete **androgens**, such as testosterone, in response to luteinizing hormone (LH). *Interstitial cells* - This term is a general descriptor for cells located in the spaces between functional tissues or organs. - In the context of the testes, **Leydig cells** are the primary interstitial cells responsible for hormone production, while **Sertoli cells** are part of the seminiferous tubules.

Q: There is a mid-cycle shift in the basal body temperature (BBT) after ovulation in women. This is caused by :

Progesterone. **Progesterone** - After ovulation, the ruptured follicle transforms into the **corpus luteum**, which primarily secretes progesterone. - **Progesterone** is a **thermogenic hormone**, meaning it directly causes an increase in basal body temperature (BBT) by about 0.5 to 1.0°F (0.2 to 0.5°C). *FSH-peak* - The **FSH-peak** occurs earlier in the follicular phase, stimulating follicular growth. - It does not directly influence basal body temperature in the post-ovulatory phase. *Oestradiol* - **Oestradiol** (estrogen) levels are highest just before ovulation, which can have a slight temperature-lowering effect or no significant impact on BBT. - It is not responsible for the sustained post-ovulatory temperature rise. *LH-peak* - The **LH-peak** triggers ovulation but does not directly cause the sustained post-ovulatory increase in BBT. - The temperature shift due to LH is transient and not sustained without subsequent progesterone production.

Q: Dihydrotestosterone acts on

External genitalia. ***External genitalia*** - **Dihydrotestosterone (DHT)** is critical for the development of **male external genitalia** during fetal development. - In adulthood, **DHT** is responsible for the growth of the **prostate** and secondary male sexual characteristics like **facial hair** and **balding**. *Pituitary* - The **pituitary gland** is primarily regulated by **gonadotropin-releasing hormone (GnRH)** from the hypothalamus and feedback from **gonadal steroids** like **testosterone** and **estrogen**, not directly by **DHT**. - **DHT** does not exert significant direct action on the anterior pituitary to regulate gonadotropin release. *Internal genitalia* - The development of **internal male genitalia**, such as the **epididymis**, **vas deferens**, and **seminal vesicles**, is primarily mediated by **testosterone** directly, not **DHT**. - **Testosterone** acts on the **Wolffian ducts** to promote their differentiation into the internal male reproductive structures. *Testis* - The **testis** is the primary site of **testosterone production** and conversion to **DHT** by **5α-reductase**. - While **DHT** is produced within the testis, its main actions are on peripheral target tissues rather than directly regulating testicular function.

Q: Transplacental exchanges that take place are essential to the well being of the fetus. Which of those listed below is NOT a method?

Exocytosis. ***Exocytosis*** - **Exocytosis** is the process where cells release substances by fusing vesicles with the cell membrane and expelling their contents outside the cell. - While exocytosis occurs as part of **transcytosis** (where substances are taken up by endocytosis on one side and released by exocytosis on the other), it is **not classified as an independent primary mechanism** of transplacental transport in standard physiology teaching. - The major recognized mechanisms of transplacental exchange are: simple diffusion, facilitated diffusion, active transport, and endocytosis/pinocytosis. *Active transport* - **Active transport** uses ATP energy to move substances against their concentration gradients across the placental membrane. - Essential for transporting **amino acids, water-soluble vitamins (B, C), calcium, iron, and iodine** from mother to fetus. - Ensures the fetus receives adequate supplies even when maternal concentrations are low. *Simple diffusion* - **Simple diffusion** is a passive process where substances move down their concentration gradient directly across cell membranes. - This is the **primary mechanism** for exchange of **respiratory gases (O₂, CO₂)**, water, and **lipid-soluble substances** (steroid hormones, fatty acids, fat-soluble vitamins) across the placenta. *Endocytosis* - **Endocytosis** involves cells internalizing substances by engulfing them via membrane invagination, forming vesicles. - **Receptor-mediated endocytosis** is crucial for transfer of **maternal IgG antibodies** to provide passive immunity to the fetus. - **Pinocytosis** (fluid-phase endocytosis) allows transfer of other large molecules and proteins.

Q: Ovulation is primarily caused by preovulatory surge of:

Luteinizing hormone. ***Luteinizing hormone*** - The **luteinizing hormone (LH) surge** is the direct trigger for ovulation, causing the mature follicle to rupture and release the ovum. - This surge is induced by a rapid increase in **estradiol** levels from the dominant follicle, which switches from negative to positive feedback on the hypothalamus and pituitary. *Progesterone* - While progesterone levels begin to rise *after* the LH surge and play a crucial role in maintaining the uterine lining for potential pregnancy, it is **not the primary cause** of ovulation itself. - Progesterone levels are relatively low during the follicular phase and only increase significantly after ovulation, particularly from the **corpus luteum**. *Estradiol* - **Estradiol** levels *rise significantly* during the follicular phase and ultimately *trigger* the LH surge through a positive feedback mechanism. - However, estradiol itself does **not directly cause follicular rupture and ovum release**; it primes the system for the LH surge to perform that function. *Follicle stimulating hormone* - **Follicle-stimulating hormone (FSH)** is primarily responsible for the **growth and maturation of ovarian follicles** during the follicular phase of the menstrual cycle. - Although FSH levels also experience a modest surge around the time of ovulation, it is the **LH surge** that directly causes follicular rupture and ovum release.

Q: Which hormones antagonize the effect of NO and cause the penis to become flaccid after orgasm?

Endothelin and norepinephrine. ***Endothelin and norepinephrine*** - **Endothelin** is a potent vasoconstrictor that promotes the contraction of smooth muscle in the penile arteries, reducing blood flow and leading to detumescence. - **Norepinephrine** (a sympathetic neurotransmitter) causes vasoconstriction in the penile arteries and corpus cavernosum, also contributing to flaccidity after orgasm. *Luteinizing hormone (LH) and follicle-stimulating hormone (FSH)* - **LH** stimulates testosterone production in Leydig cells, playing a crucial role in libido and spermatogenesis, but not directly in the process of penile detumescence. - **FSH** is primarily involved in spermatogenesis and the maturation of germ cells, with no direct role in the vascular mechanisms of penile flaccidity. *Progesterone and LH* - **Progesterone** is predominantly a female sex hormone, with only minor roles in male physiology, and does not directly antagonize NO effects in penile detumescence. - As mentioned, **LH** primarily regulates testosterone production and is not involved in post-orgasm flaccidity. *Estrogen and progesterone* - **Estrogen** levels in males are low and primarily involved in bone health and spermatogenesis, not penile detumescence. - **Progesterone** does not play a direct role in the vascular mechanisms leading to penile flaccidity in males.

Q: Progesterone production in the ovary is primarily by:

Corpora lutea. ***Corpora lutea*** - The **corpus luteum** forms after ovulation from the remnants of the ovarian follicle and is the primary source of **progesterone** during the luteal phase of the menstrual cycle and early pregnancy. - Its main function is to prepare the **endometrium** for implantation and maintain pregnancy. *Corpora albicans* - This is the **scar tissue** left after the degeneration of the **corpus luteum** when pregnancy does not occur. - It is **inactive hormonally** and does not produce significant amounts of progesterone. *Stroma* - The **stroma** is the connective tissue framework of the ovary that supports the follicles. - While it contains cells that can produce some **androgens**, it is not the primary site of **progesterone** production. *Mature follicles* - **Mature follicles** (Graafian follicles) primarily produce **estrogen** in preparation for ovulation. - Although they produce some progesterone just before ovulation, the **corpus luteum** is the main producer after ovulation.

Q: Spermatogenesis is mostly controlled by:

FSH. ***FSH*** - **Follicle-stimulating hormone (FSH)** acts directly on **Sertoli cells** in the seminiferous tubules, stimulating them to support spermatogenesis and produce **androgen-binding protein (ABP)**. - FSH directly promotes the **proliferation and differentiation of spermatogonia** and is essential for the initiation and maintenance of spermatogenesis. - While spermatogenesis requires both FSH and testosterone working synergistically, **FSH is considered the primary direct regulator** at the Sertoli cell level, making it the best answer when comparing these hormonal options. *LH* - **Luteinizing hormone (LH)** acts on **Leydig cells** to stimulate **testosterone production**, which is absolutely essential for completing spermatogenesis (especially meiosis and spermiogenesis). - However, LH's role is considered **indirect** as it works through testosterone, whereas FSH directly stimulates the Sertoli cells that physically support developing sperm. - Both FSH and testosterone are required; neither alone is sufficient. *GnRH* - **Gonadotropin-releasing hormone (GnRH)** from the hypothalamus controls the release of both LH and FSH from the anterior pituitary gland. - It acts as the **master regulator of the hypothalamic-pituitary-gonadal axis** but does not directly control spermatogenesis at the testicular level. - Its effect is indirect, operating two steps removed from the testes. *Inhibin* - **Inhibin** is produced by **Sertoli cells** in response to FSH and provides **negative feedback** on FSH secretion from the anterior pituitary. - It regulates the regulator (FSH levels) but does not directly control spermatogenesis itself. - It serves as a feedback mechanism to fine-tune FSH levels based on the state of spermatogenesis.

Question 1

In this normal menstrual cycle graph, the mark 'X' represents levels of which hormone?

Accepted Answer

Progesterone

Answer

LH

Answer

FSH

Answer

Estrogen

Question 2

Testosterone is secreted by:

Accepted Answer

Leydig cell

Answer

Granulosa cell

Answer

Theca cells

Answer

Sertoli cell

Question 3

Inhibin is secreted by:

Accepted Answer

Sertoli cells

Answer

Peg cells

Answer

Leydig cells

Answer

Interstitial cells

Question 4

There is a mid-cycle shift in the basal body temperature (BBT) after ovulation in women. This is caused by :

Accepted Answer

Progesterone

Answer

FSH-peak

Answer

Oestradiol

Answer

LH-peak

Question 5

Dihydrotestosterone acts on

Accepted Answer

External genitalia

Answer

Pituitary

Answer

Internal genitalia

Answer

Testis

Question 6

Transplacental exchanges that take place are essential to the well being of the fetus. Which of those listed below is NOT a method?

Accepted Answer

Exocytosis

Answer

Active transport

Answer

Simple diffusion

Answer

Endocytosis

Question 7

Ovulation is primarily caused by preovulatory surge of:

Accepted Answer

Luteinizing hormone

Answer

Progesterone

Answer

Estradiol

Answer

Follicle stimulating hormone

Question 8

Which hormones antagonize the effect of NO and cause the penis to become flaccid after orgasm?

Accepted Answer

Endothelin and norepinephrine

Answer

Luteinizing hormone (LH) and follicle-stimulating hormone (FSH)

Answer

Progesterone and LH

Answer

Estrogen and progesterone

Question 9

Progesterone production in the ovary is primarily by:

Accepted Answer

Corpora lutea

Answer

Corpora albicans

Answer

Stroma

Answer

Mature follicles

Question 10

Spermatogenesis is mostly controlled by:

Accepted Answer

FSH

Answer

GnRH

Answer

LH

Answer

Inhibin

Reproductive Physiology — MCQs

Reproductive Physiology — MCQs

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