Reproductive Physiology — MCQs

Reproductive Physiology Indian Medical PG Practice Questions and MCQs

Question 391: Which hormone binds to the receptors on Leydig cells?

A. TSH
B. GH
C. PRL
D. LH (Correct Answer)

Explanation: ***LH*** - **Luteinizing Hormone (LH)** binds to specific receptors on **Leydig cells** in the testes. - This binding stimulates the Leydig cells to produce and secrete **testosterone**, which is crucial for male reproductive function. *TSH* - **Thyroid-Stimulating Hormone (TSH)** acts on the **thyroid gland** to stimulate the production of thyroid hormones (T3 and T4). - It does not have a direct role in regulating Leydig cell function. *GH* - **Growth Hormone (GH)** primarily promotes **tissue growth** and development by stimulating protein synthesis and cell proliferation throughout the body. - While it has broad effects, it does not directly bind to Leydig cell receptors for testosterone production. *PRL* - **Prolactin (PRL)** is primarily involved in **lactation** in females and has various general metabolic effects in both sexes. - While it plays a role in male reproductive health, it does not directly stimulate Leydig cells via specific receptors to produce testosterone.

Question 392: Ovulation is influenced by

A. LH+FSH
B. LH (Correct Answer)
C. FSH
D. GnRH

Explanation: ***LH*** - A surge in **luteinizing hormone (LH)** is the primary trigger for ovulation, inducing the final maturation of the oocyte and rupture of the dominant follicle. - The **LH surge** leads to the release of the ovum from the ovary, typically occurring about 24-36 hours after its onset. *LH+FSH* - While both **LH** and **FSH** are essential for follicular development, the *final act of ovulation itself is primarily driven by the LH surge*, not a combined surge of both. - **FSH** mainly promotes the growth of ovarian follicles in the early to mid-follicular phase. *FSH* - **Follicle-stimulating hormone (FSH)** is crucial for the *development and maturation* of ovarian follicles but does not directly trigger the release of the egg. - High levels of **FSH** alone do not induce ovulation; its role is completed before the actual ovulatory event. *GnRH* - **Gonadotropin-releasing hormone (GnRH)** is released from the hypothalamus and stimulates the pituitary gland to release **LH** and **FSH**. - **GnRH** is a precursor to the release of LH and FSH, but it does not directly act on the ovary to cause ovulation.

Question 393: Ejection of milk is caused by

A. Progesterone
B. Thyroxine
C. ADH
D. Oxytocin (Correct Answer)

Explanation: ***Oxytocin*** - **Oxytocin** is responsible for the **milk ejection reflex** (let-down reflex) by stimulating the contraction of **myoepithelial cells** surrounding the alveoli in the mammary glands. - This hormone is released from the **posterior pituitary** in response to suckling, leading to the expulsion of milk from the alveoli into the ducts. *Progesterone* - **Progesterone** is primarily involved in the **development of mammary glands** during pregnancy and preparing them for lactation. - High levels of progesterone during pregnancy actually **inhibit lactation** by blocking prolactin's action; milk production begins after progesterone levels drop postpartum. *Thyroxine* - **Thyroxine** (thyroid hormone) plays a role in **overall metabolism** and is necessary for normal growth and development, but it does not directly cause milk ejection. - While thyroid hormones support general metabolic functions including lactation, they are not involved in the milk ejection reflex itself. *ADH* - **ADH (Antidiuretic Hormone)**, also known as vasopressin, primarily regulates **water balance** by promoting water reabsorption in the kidneys. - Despite being released from the posterior pituitary like oxytocin, ADH has no direct role in the milk ejection reflex.

Question 394: Inhibin inhibits secretion of which of the following hormones?

A. FSH (Correct Answer)
B. LH releasing hormone
C. LH
D. Estrogen and progesterone

Explanation: ***FSH*** - **Inhibin** is a glycoprotein hormone primarily produced by the **gonads (Sertoli cells in males, granulosa cells in females)** and selectively inhibits the secretion of **follicle-stimulating hormone (FSH)** from the anterior pituitary gland. - This negative feedback mechanism helps regulate **gamete production** without significantly affecting **luteinizing hormone (LH)** secretion. *LH releasing hormone* - **Luteinizing hormone-releasing hormone (LHRH)**, also known as **gonadotropin-releasing hormone (GnRH)**, is released from the hypothalamus and stimulates the anterior pituitary to secrete both **LH and FSH**. - Inhibin does not directly inhibit the secretion or action of **LHRH/GnRH**. *LH* - While both **FSH** and **LH** are gonadotropins, inhibin specifically targets **FSH** secretion. - **LH** secretion is primarily regulated by **GnRH** and sex steroids, not directly by inhibin. *Estrogen and progesterone* - **Estrogen** and **progesterone** are steroid hormones produced by the gonads and play crucial roles in regulating the **menstrual cycle** and **reproductive functions**. - Inhibin does not directly inhibit the secretion of **estrogen** and **progesterone**; rather, these steroid hormones exert their own feedback on the **hypothalamus** and **pituitary**.

Question 395: Follicle stimulating hormone (FSH) receptors are present on:

A. Granulosa cells (Correct Answer)
B. Basement membrane of ovarian follicle
C. Leydig cells
D. Theca cells

Explanation: ***Granulosa cells*** - **Granulosa cells** are the **primary target cells** for **FSH** in the ovarian follicles. - FSH binding to its receptors on granulosa cells stimulates their proliferation and differentiation, leading to **follicular growth** and **estrogen production**. - Granulosa cells have the **highest density of FSH receptors** in the ovary, making this the classical answer. *Basement membrane of ovarian follicle* - The **basement membrane** is a structural component that separates the granulosa cells from the theca cells and ovarian stroma. - It does not contain hormone receptors, as its function is primarily for **structural support** and **filtration**. *Leydig cells* - **Leydig cells** are found in the testes, not the ovarian follicle, and are primarily stimulated by **luteinizing hormone (LH)** to produce **androgens**. - Leydig cells do not have FSH receptors; FSH receptors in the testes are found on **Sertoli cells**. *Theca cells* - **Theca cells** are primarily responsible for producing **androgens** (e.g., androstenedione) in response to **LH stimulation**. - **LH receptors predominate** on theca cells, making them the primary LH-responsive cells in the follicle. - While theca interna cells may express some FSH receptors, their density is much lower compared to granulosa cells, and LH remains their primary regulatory hormone. - Androgens produced by theca cells are transported to granulosa cells for aromatization into estrogens.

Question 396: Ductal development of breast is caused by

A. Prolactin
B. Progesterone
C. hCG
D. Estrogen (Correct Answer)

Explanation: ***Estrogen*** - **Estrogen** is the primary hormone responsible for the **proliferation and branching of ducts** in the breast. - It stimulates the growth of the ductal system during puberty and throughout the menstrual cycle. *Prolactin* - **Prolactin** primarily stimulates **milk production** (lactogenesis) in fully developed breasts, rather than ductal development. - It also plays a role in the differentiation of mammary epithelial cells. *Progesterone* - **Progesterone** is mainly responsible for the development of the **lobuloalveolar structures** (glandular tissue) in the breast, which are responsible for milk secretion. - It works in conjunction with estrogen to prepare the breast for lactation, but its primary role is not ductal growth. *hCG* - **Human chorionic gonadotropin (hCG)** is a hormone produced during **pregnancy**, primarily by the placenta. - While it supports the maintenance of pregnancy and indirectly influences breast changes, it does not directly cause ductal development.

Question 397: Which of the following nuclei of Hypothalamus is most closely related to sexual activity in males?

A. Lateral hypothalamic nuclei
B. Posterior hypothalamic nuclei
C. Preoptic nucleus (Correct Answer)
D. Supraoptic nucleus

Explanation: ***Preoptic nucleus*** - The **preoptic area** of the hypothalamus, particularly its medial preoptic nucleus, is critically involved in regulating **male sexual behavior** and **gonadotropin release**. - Lesions in this area can significantly reduce or abolish sexual activity in males. *Lateral hypothalamic nuclei* - The **lateral hypothalamic nuclei** are primarily associated with the sensation of **hunger** and **feeding behavior**. - Stimulation of this area can induce eating, while lesions can lead to aphagia. *Posterior hypothalamic nuclei* - The **posterior hypothalamus** is largely involved in **arousal**, maintaining **wakefulness**, and regulating **body temperature**. - It plays a role in the sympathetic nervous system's response to stress. *Supraoptic nucleus* - The **supraoptic nucleus** is responsible for producing **vasopressin (ADH)** and **oxytocin**, which are then released by the posterior pituitary. - These hormones are crucial for water balance and social bonding, respectively.

Question 398: In human males, testosterone is mainly produced by

A. Leydig cells (Correct Answer)
B. Seminiferous tubules
C. Epididymis
D. Sertoli cells

Explanation: ***Leydig cells*** - **Leydig cells** are located in the **interstitial tissue** between the seminiferous tubules in the testes and are responsible for producing **testosterone** in response to luteinizing hormone (LH). - These cells are crucial for the development of male secondary sexual characteristics and spermatogenesis. *Seminiferous tubules* - The **seminiferous tubules** are the primary sites of **spermatogenesis**, the process of sperm production. - While essential for male fertility, they do not directly produce testosterone. *Epididymis* - The **epididymis** is a coiled tube located on the posterior aspect of each testis, where **sperm mature** and are stored. - It plays no role in the production of testosterone. *Sertoli cells* - **Sertoli cells** are found within the **seminiferous tubules** and provide support, nourishment, and protection to developing sperm. - They also produce **androgen-binding protein (ABP)** and inhibin, but not testosterone.

Question 399: Inhibin B during the follicular phase is primarily secreted by-

A. Corpus luteum
B. Ovarian Follicle (Correct Answer)
C. Stroma
D. Surface epithelium of ovary

Explanation: ***Ovarian Follicle*** - **Inhibin B** is primarily secreted by the **granulosa cells** of developing ovarian follicles during the **follicular phase** of the menstrual cycle. - It selectively inhibits **FSH secretion** from the anterior pituitary, providing negative feedback regulation. - Inhibin B levels rise during follicular development and peak at mid-cycle. *Corpus luteum* - The corpus luteum primarily secretes **Inhibin A** (not Inhibin B) during the luteal phase after ovulation. - While both structures produce inhibin, **Inhibin B is specifically associated with follicular activity**, whereas Inhibin A is the luteal phase marker. - The corpus luteum's main hormones are progesterone and estradiol. *Stroma* - The ovarian **stroma** consists of connective tissue and provides structural support. - It contains theca cells that produce androgens but does not directly secrete inhibin. - Its primary role is supportive rather than endocrine. *Surface epithelium of ovary* - The **surface epithelium** is the outermost protective layer of the ovary. - It has no endocrine function and does not produce inhibin or other reproductive hormones. - This layer is primarily involved in covering and protecting the underlying ovarian tissue.

Question 400: Which finding would be present following selective destruction of sertoli cells?

A. Increased plasma luteinizing hormone (LH) levels
B. Increased plasma testosterone levels
C. Increased plasma follicle-stimulating hormone (FSH) levels (Correct Answer)
D. Increased plasma inhibin levels

Explanation: ***Increased plasma follicle-stimulating hormone (FSH) levels*** - **Sertoli cells** produce **inhibin B**, which directly and specifically provides **negative feedback** on **FSH** secretion from the anterior pituitary. - Selective destruction of **Sertoli cells** leads to markedly decreased inhibin B, removing this negative feedback on **FSH**, thus causing a **significant increase** in plasma FSH levels. - This is the **most direct and prominent** hormonal finding following Sertoli cell destruction. *Increased plasma luteinizing hormone (LH) levels* - While **LH** may increase somewhat due to impaired testicular function and loss of paracrine support, the **primary and most direct** hormonal change is the increase in **FSH**. - **LH** regulation is mainly through testosterone negative feedback from **Leydig cells**, which remain intact in selective Sertoli cell destruction. - The FSH elevation is far more pronounced and specific to Sertoli cell loss than any LH changes. *Increased plasma testosterone levels* - **Testosterone** is primarily produced by **Leydig cells**, which are not directly affected by selective destruction of Sertoli cells. - In reality, testosterone levels would likely **decrease** (not increase) over time due to loss of spermatogenic tubule integrity and paracrine support from Sertoli cells. - There is no physiological mechanism by which Sertoli cell destruction would increase testosterone. *Increased plasma inhibin levels* - **Inhibin B** is secreted specifically by **Sertoli cells** and acts as a negative regulator of **FSH** release. - Selective destruction of Sertoli cells would lead to a marked **decrease** in inhibin B production, not an increase.

Practice by Chapter

Male Reproductive Physiology

Practice Questions

Spermatogenesis and Sperm Function

Practice Questions

Female Reproductive Physiology

Practice Questions

Menstrual Cycle

Practice Questions

Ovulation and Fertilization

Practice Questions

Physiology of Pregnancy

Practice Questions

Parturition

Practice Questions

Lactation

Practice Questions

Sexual Differentiation and Development

Practice Questions

Reproductive Aging

Practice Questions

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