Q: Q1. Fill in the blanks:\n(a) Humans reproduce __________ (asexually/sexually)\n(b) Humans are __________ (oviparous/viviparous/ovoviviparous)\n(c) Fertilisation is __________ in humans

(a) Humans reproduce **sexually**.\n(b) Humans are **viviparous**.\n(c) Fertilisation is **internal** in humans.\n(d) Male and female gametes are **haploid**.\n(e) Zygote is **diploid**.\n(f) The process of release of ovum from a mature follicle is called **ovulation**.\n(g) Ovulation is induced by a hormone called **Luteinizing Hormone (LH)**.\n(h) The fusion of male and female gametes is called **fertilisation**.\n(i) Fertilisation takes place in **fallopian tube (ampullary-isthmic junction)**.\n(j) Zygote divides to form **blastocyst**, which is implanted in uterus.\n(k) The structure which provides vascular connection between the foetus and uterus is called **placenta**.

Q: Q4. Write two major functions each of testis and ovary.

The two major functions of the testis and ovary are:\n\n**Functions of Testis:**\n1. **Spermatogenesis:** The primary function of the testes is the production of male gametes, called spermatozoa (sperms), through a process called spermatogenesis. This occurs in the seminiferous tubules within the testes.\n2. **Hormone Production:** The testes produce male sex hormones, primarily androgens like testosterone. These hormones are responsible for the development of male secondary sexual characteristics, maintenance of male reproductive organs, and regulation of spermatogenesis.\n\n**Functions of Ovary:**\n1. **Oogenesis:** The primary function of the ovaries is the production of female gametes, called ova (eggs), through a process called oogenesis. This involves the development and maturation of ovarian follicles and the release of a mature ovum during ovulation.\n2. **Hormone Production:** The ovaries produce female sex hormones, mainly estrogen and progesterone. Estrogen is responsible for the development of female secondary sexual characteristics and the growth of ovarian follicles. Progesterone is crucial for maintaining pregnancy and preparing the uterus for implantation.

Q: Q14. Define spermiogenesis and spermiation.

### Spermiogenesis\nSpermiogenesis is the process of transformation of non-motile, spherical, haploid **spermatids** (formed after meiosis II) into highly motile, elongated, and specialized **spermatozoa** (sperms). This process involves significant morphological changes within the spermatid, including:\n* Formation of the acrosome from the Golgi apparatus.\n* Condensation and elongation of the nucleus.\n* Formation of the middle piece with mitochondria arranged spirally.\n* Development of a flagellum (tail) for motility.\n* Shedding of excess cytoplasm.\nDuring spermiogenesis, the developing sperm heads become embedded in the Sertoli cells for nourishment and support.\n\n### Spermiation\nSpermiation is the final step in spermatogenesis, where the mature spermatozoa are released from the Sertoli cells into the lumen of the seminiferous tubules. After undergoing spermiogenesis, the fully formed spermatozoa detach from the Sertoli cells and are then transported out of the testes through the male accessory ducts.

Question 1

Q1. Fill in the blanks:
(a) Humans reproduce __________ (asexually/sexually)
(b) Humans are __________ (oviparous/viviparous/ovoviviparous)
(c) Fertilisation is __________ in humans

Accepted Answer

(a) Humans reproduce **sexually**.
(b) Humans are **viviparous**.
(c) Fertilisation is **internal** in humans.
(d) Male and female gametes are **haploid**.
(e) Zygote is **diploid**.
(f) The process of release of ovum from a mature follicle is called **ovulation**.
(g) Ovulation is induced by a hormone called **Luteinizing Hormone (LH)**.
(h) The fusion of male and female gametes is called **fertilisation**.
(i) Fertilisation takes place in **fallopian tube (ampullary-isthmic junction)**.
(j) Zygote divides to form **blastocyst**, which is implanted in uterus.
(k) The structure which provides vascular connection between the foetus and uterus is called **placenta**.

Question 2

Q2. Draw a labelled diagram of male reproductive system.

Accepted Answer

A detailed, labelled diagram of the human male reproductive system should be drawn. The diagram should clearly illustrate the various organs and their anatomical positions. Key structures to be labelled include:

**Primary Sex Organ:**
1.  **Testis:** The primary male gonad, located outside the abdominal cavity within the scrotum.

**Accessory Ducts:**
2.  **Rete Testis:** Network of tubules within the testis.
3.  **Vasa Efferentia:** Ducts leading from the rete testis to the epididymis.
4.  **Epididymis:** A long, coiled tube located along the posterior surface of each testis, where sperm mature and are stored.
5.  **Vas Deferens:** A tube that carries sperm from the epididymis up into the pelvic cavity, loops over the urinary bladder.
6.  **Ejaculatory Duct:** Formed by the union of the vas deferens and the duct from the seminal vesicle, it passes through the prostate gland and opens into the urethra.
7.  **Urethra:** The terminal duct for both urine and semen, extending from the urinary bladder through the penis.

**Accessory Glands:**
8.  **Seminal Vesicle:** Paired glands that secrete a fluid rich in fructose, prostaglandins, and clotting proteins, contributing to semen volume.
9.  **Prostate Gland:** A single gland surrounding the urethra, secreting a milky, slightly acidic fluid containing citrate, enzymes, and prostate-specific antigen (PSA).
10. **Bulbourethral Glands (Cowper's Glands):** Paired glands located inferior to the prostate, secreting a clear, alkaline mucus that lubricates the urethra and neutralizes acidic urine.

**External Genitalia:**
11. **Scrotum:** A pouch of skin that contains the testes, helping to maintain a lower temperature necessary for spermatogenesis.
12. **Penis:** The male copulatory organ, containing erectile tissue, through which the urethra passes.

**Other associated structures:**
13. **Urinary Bladder:** Stores urine.
14. **Ureter:** Tube carrying urine from the kidney to the bladder.
15. **Rectum:** Terminal part of the large intestine.
16. **Pubic Symphysis:** Cartilaginous joint between the pubic bones.

The diagram should typically show a sagittal view (side view) to clearly depict the relationship between these structures.

Question 3

Q3. Draw a labelled diagram of female reproductive system.

Accepted Answer

A detailed, labelled diagram of the human female reproductive system should be drawn. The diagram should clearly illustrate the various organs and their anatomical positions. Key structures to be labelled include:

**Primary Sex Organ:**
1.  **Ovary:** Paired primary female sex organs located one on each side in the lower abdomen, responsible for producing ova and steroid hormones.

**Accessory Ducts (Oviducts/Fallopian Tubes):**
2.  **Infundibulum:** The funnel-shaped part of the fallopian tube closest to the ovary, with finger-like projections called fimbriae.
3.  **Fimbriae:** Finger-like projections of the infundibulum that help collect the ovum after ovulation.
4.  **Ampulla:** The wider, longest part of the fallopian tube, where fertilisation typically occurs.
5.  **Isthmus:** The narrow lumen part of the fallopian tube that joins the uterus.

**Uterus (Womb):**
6.  **Uterus:** A hollow, pear-shaped muscular organ where the fertilised egg implants and develops into a foetus.
7.  **Fundus:** The dome-shaped upper part of the uterus.
8.  **Uterine Cavity:** The space within the uterus.
9.  **Endometrium:** The innermost glandular layer of the uterine wall, which undergoes cyclical changes during the menstrual cycle and is the site of implantation.
10. **Myometrium:** The middle thick layer of smooth muscle of the uterine wall, responsible for strong contractions during childbirth.
11. **Perimetrium:** The outermost thin membranous layer of the uterine wall.

**Cervix:**
12. **Cervix:** The narrow lower part of the uterus that extends into the vagina.
13. **Cervical Canal:** The canal within the cervix.
14. **Internal Os:** Opening from the uterus into the cervical canal.
15. **External Os:** Opening from the cervical canal into the vagina.

**Vagina:**
16. **Vagina:** A muscular tube extending from the cervix to the exterior, serving as the birth canal and receiving sperm during copulation.

**Other associated structures:**
17. **Urinary Bladder:** Stores urine.
18. **Ureter:** Tube carrying urine from the kidney to the bladder.
19. **Rectum:** Terminal part of the large intestine.

The diagram should typically show a frontal view (anterior view) to clearly depict the relationship between these structures.

Question 4

Q4. Write two major functions each of testis and ovary.

Accepted Answer

The two major functions of the testis and ovary are:

**Functions of Testis:**
1.  **Spermatogenesis:** The primary function of the testes is the production of male gametes, called spermatozoa (sperms), through a process called spermatogenesis. This occurs in the seminiferous tubules within the testes.
2.  **Hormone Production:** The testes produce male sex hormones, primarily androgens like testosterone. These hormones are responsible for the development of male secondary sexual characteristics, maintenance of male reproductive organs, and regulation of spermatogenesis.

**Functions of Ovary:**
1.  **Oogenesis:** The primary function of the ovaries is the production of female gametes, called ova (eggs), through a process called oogenesis. This involves the development and maturation of ovarian follicles and the release of a mature ovum during ovulation.
2.  **Hormone Production:** The ovaries produce female sex hormones, mainly estrogen and progesterone. Estrogen is responsible for the development of female secondary sexual characteristics and the growth of ovarian follicles. Progesterone is crucial for maintaining pregnancy and preparing the uterus for implantation.

Question 5

Q5. Describe the structure of a seminiferous tubule with the help of a labelled diagram.

Accepted Answer

The seminiferous tubules are the structural and functional units of the testis, where spermatogenesis (sperm production) takes place. Each testis contains about 250 compartments called testicular lobules, and each lobule contains one to three highly coiled seminiferous tubules. A transverse section (TS) of a seminiferous tubule reveals its complex internal structure.

### Structure of a Seminiferous Tubule

1.  **Tubular Wall:** The wall of the seminiferous tubule is lined by a germinal epithelium, which consists of two main types of cells:
    *   **Male Germ Cells (Spermatogonia):** These are undifferentiated, diploid (2n) cells located on the inner wall of the seminiferous tubule. They undergo mitotic divisions to increase their number and then differentiate to form primary spermatocytes, which further undergo meiosis to produce sperm.
    *   **Sertoli Cells (Sustentacular Cells):** These are tall, pyramidal cells that extend from the basement membrane to the lumen of the tubule. They provide nourishment to the developing germ cells, phagocytose cellular debris, and secrete various factors, including androgen-binding protein (ABP) and inhibin, which are important for spermatogenesis regulation. They also form the blood-testis barrier.

2.  **Developing Spermatogenic Cells:** Within the seminiferous tubule, various stages of developing sperm cells can be observed, arranged in a specific order from the periphery towards the lumen:
    *   **Spermatogonia:** The outermost layer, closest to the basement membrane.
    *   **Primary Spermatocytes:** Larger cells formed from spermatogonia, undergoing Meiosis I.
    *   **Secondary Spermatocytes:** Smaller, haploid cells formed after Meiosis I, undergoing Meiosis II.
    *   **Spermatids:** Haploid cells formed after Meiosis II, which then undergo spermiogenesis to transform into spermatozoa.
    *   **Spermatozoa (Sperms):** Mature male gametes, with heads embedded in Sertoli cells and tails extending into the lumen, eventually released into the lumen.

3.  **Lumen:** The central cavity of the seminiferous tubule, into which mature spermatozoa are released.

### Interstitial Space (Leydig Cells)

Outside the seminiferous tubules, in the interstitial spaces, there are small blood vessels and specialized endocrine cells called **Interstitial Cells (Leydig Cells)**. These cells synthesize and secrete testicular hormones called androgens (e.g., testosterone) in response to Luteinizing Hormone (LH) from the pituitary gland. These androgens are crucial for spermatogenesis and the development of male secondary sexual characteristics.

### Labelled Diagram Description:
A labelled diagram of a transverse section (TS) of a seminiferous tubule should clearly show:
*   The outer **basement membrane** of the tubule.
*   **Spermatogonia** (germ cells) located near the basement membrane.
*   Progressively developing stages of sperm: **Primary spermatocytes**, **Secondary spermatocytes**, and **Spermatids** towards the lumen.
*   **Spermatozoa** (sperms) with their heads embedded in Sertoli cells and tails pointing towards the lumen.
*   Large, irregularly shaped **Sertoli cells** extending from the basement membrane to the lumen, enveloping the developing germ cells.
*   The central **lumen** of the tubule.
*   In the **interstitial space** outside the tubule, **Leydig cells** and **blood vessels** should be depicted.

Question 6

Q6. What are the major functions of male accessory ducts and glands?

Accepted Answer

The male accessory ducts and glands play crucial roles in the transport, maturation, and nourishment of spermatozoa, as well as in the formation of semen.

### I. Male Accessory Ducts
The male accessory ducts are responsible for the storage and transport of spermatozoa from the testis to the outside. These include:

1.  **Rete Testis:** This is a network of tubules located within the testis. Its primary function is to collect spermatozoa from the seminiferous tubules and channel them towards the vasa efferentia.

2.  **Vasa Efferentia (Efferent Ductules):** These are 10-12 fine tubules that emerge from the rete testis and open into the epididymis. Their main function is to transport spermatozoa from the testis to the epididymis.

3.  **Epididymis:** A long, highly coiled tube located along the posterior surface of each testis. It serves several critical functions:
    *   **Storage:** It stores spermatozoa for a period, allowing them to mature.
    *   **Maturation:** Spermatozoa acquire motility and fertilizing capacity during their transit through the epididymis.
    *   **Protection:** It provides a suitable environment for sperm survival.

4.  **Vas Deferens (Ductus Deferens):** This tube ascends from the epididymis, loops over the urinary bladder, and joins with the duct from the seminal vesicle to form the ejaculatory duct. Its primary function is to transport mature sperm from the epididymis to the ejaculatory duct during ejaculation.

### II. Male Accessory Glands
The male accessory glands contribute fluids that constitute the seminal plasma, which mixes with sperm to form semen. These fluids provide nourishment, protection, and aid in sperm motility.

1.  **Seminal Vesicles (Paired):** These are a pair of glands located posterior to the urinary bladder. They secrete a viscous, alkaline fluid that makes up about 60-70% of the semen volume. This fluid contains:
    *   **Fructose:** Provides energy for sperm motility.
    *   **Prostaglandins:** Stimulate uterine contractions in the female reproductive tract, aiding sperm movement towards the ovum.
    *   **Clotting Proteins (e.g., Fibrinogen):** Help semen coagulate after ejaculation, preventing its leakage from the vagina.

2.  **Prostate Gland (Single):** This gland is located inferior to the urinary bladder and surrounds the urethra. It secretes a milky, slightly acidic fluid (about 20-30% of semen volume) containing:
    *   **Citric Acid:** A nutrient for sperm.
    *   **Enzymes:** Such as acid phosphatase, fibrinolysin, and prostate-specific antigen (PSA), which help in liquefaction of the coagulated semen after some time.
    *   **Seminalplasmin:** An antibiotic that destroys bacteria, protecting sperm.

3.  **Bulbourethral Glands (Cowper's Glands) (Paired):** These small glands are located inferior to the prostate gland. They secrete a clear, viscous, alkaline fluid into the urethra prior to ejaculation. This fluid serves to:
    *   **Lubricate:** Lubricate the urethra and the tip of the penis.
    *   **Neutralize Acidity:** Neutralize any residual acidity from urine in the urethra, creating a favorable environment for sperm survival.

**Overall Function:** The combined secretions of the male accessory glands form the seminal plasma, which, along with the spermatozoa, constitutes the semen. This seminal plasma provides the necessary medium for sperm transport, nourishment, protection, and activation, ensuring their viability and successful delivery to the female reproductive tract.

Question 7

Q7. What are the major functions of male accessory ducts and glands?

Accepted Answer

The male accessory ducts and glands play crucial roles in the transport, maturation, and nourishment of sperm, as well as in the formation of semen.

### I. Male Accessory Ducts
The male accessory ducts include the rete testis, vasa efferentia, epididymis, and vas deferens. Their primary functions are:

1.  **Rete Testis:** A network of tubules located in the mediastinum testis. It collects spermatozoa from the seminiferous tubules and channels them into the vasa efferentia.
2.  **Vasa Efferentia (Efferent Ductules):** These are 10-12 fine tubules that emerge from the rete testis and open into the epididymis. They transport spermatozoa from the rete testis to the epididymis. The epithelial lining contains cilia that aid in sperm movement.
3.  **Epididymis:** A long, coiled tube located along the posterior surface of each testis. It serves as a site for:
    *   **Sperm Storage:** Stores spermatozoa for a period, allowing them to mature and acquire motility.
    *   **Sperm Maturation:** Spermatozoa undergo physiological maturation here, becoming motile and capable of fertilization.
    *   **Sperm Concentration:** Absorbs excess fluid, concentrating the sperm.
4.  **Vas Deferens (Ductus Deferens):** A muscular tube that ascends from the epididymis, loops over the urinary bladder, and joins with the duct from the seminal vesicle to form the ejaculatory duct. Its main functions are:
    *   **Sperm Transport:** Transports mature spermatozoa from the epididymis to the ejaculatory duct during ejaculation.
    *   **Sperm Storage:** Can also store sperm for a short period.

### II. Male Accessory Glands
The male accessory glands include the seminal vesicles, prostate gland, and bulbourethral glands. Their secretions collectively form the seminal plasma, which mixes with sperm to form semen.

1.  **Seminal Vesicles (Paired):** These are a pair of glands located posterior to the urinary bladder. They secrete a viscous, alkaline fluid that constitutes about 60-70% of the total semen volume. This fluid contains:
    *   **Fructose:** Provides energy for sperm motility.
    *   **Prostaglandins:** Stimulate contractions in the female reproductive tract, aiding sperm transport.
    *   **Clotting Proteins:** Help semen coagulate after ejaculation, keeping it in the female reproductive tract.
2.  **Prostate Gland (Single):** A single, large gland located inferior to the urinary bladder, surrounding the urethra. It secretes a milky, slightly acidic fluid (about 20-30% of semen volume) containing:
    *   **Citrate:** A nutrient for sperm.
    *   **Enzymes:** Such as prostate-specific antigen (PSA), acid phosphatase, and fibrinolysin, which help liquefy the coagulated semen after some time.
    *   **Seminalplasmin:** An antibiotic that helps prevent urinary tract infections in males.
3.  **Bulbourethral Glands (Cowper's Glands) (Paired):** Small, pea-sized glands located inferior to the prostate gland, on either side of the urethra. They secrete a clear, viscous, alkaline fluid into the urethra before ejaculation. This fluid:
    *   **Lubricates the Urethra:** Reduces friction for sperm passage.
    *   **Neutralizes Acidity:** Helps neutralize any residual acidity from urine in the urethra, protecting sperm.
    *   **Lubricates the Penis:** Aids in intercourse.

In summary, the accessory ducts facilitate the transport and maturation of sperm, while the accessory glands provide the necessary fluid medium, nutrients, and protective substances for sperm survival, motility, and successful delivery into the female reproductive tract.

Question 8

Q8. What is spermatogenesis? Briefly describe the process of spermatogenesis.

Accepted Answer

### What is Spermatogenesis?
Spermatogenesis is the process of formation of spermatozoa (sperm) from immature germ cells (spermatogonia) in the seminiferous tubules of the testes. This complex process involves mitotic divisions, meiotic divisions, and morphological differentiation, occurring continuously in sexually mature males.

### Process of Spermatogenesis
Spermatogenesis can be broadly divided into three main phases:

#### 1. Multiplication Phase
*   **Spermatogonia:** The innermost layer of cells in the seminiferous tubules consists of undifferentiated primordial germ cells called spermatogonia (2n, diploid). These cells are present on the inner wall of seminiferous tubules.
*   **Mitotic Divisions:** At puberty, due to the secretion of Gonadotropin-Releasing Hormone (GnRH) from the hypothalamus, which stimulates the anterior pituitary to secrete Luteinizing Hormone (LH) and Follicle-Stimulating Hormone (FSH), the spermatogonia start multiplying by repeated mitotic divisions. Some spermatogonia act as stem cells (Type A spermatogonia) to maintain the population, while others (Type B spermatogonia) differentiate to enter the next phase.

#### 2. Growth Phase
*   **Primary Spermatocytes:** Type B spermatogonia grow in size and accumulate nutrients, becoming larger diploid cells called primary spermatocytes (2n). These cells are ready to undergo meiosis.

#### 3. Maturation Phase (Meiosis)
This phase involves two meiotic divisions:

*   **Meiosis I:** Each diploid primary spermatocyte (2n) undergoes the first meiotic division (reductional division). This division produces two equal, haploid cells called secondary spermatocytes (n). Each secondary spermatocyte has 23 chromosomes, each with two chromatids.
*   **Meiosis II:** Each secondary spermatocyte (n) then rapidly undergoes the second meiotic division (equational division). This division produces two haploid spermatids (n). Thus, from one primary spermatocyte, four haploid spermatids are formed.

#### 4. Spermiogenesis
*   **Transformation of Spermatids:** Spermatids are non-motile, round cells. The process of transformation of non-motile spermatids into motile, elongated spermatozoa (sperm) is called spermiogenesis. During this process, the spermatid undergoes significant morphological changes:
    *   The nucleus condenses to form the head of the sperm.
    *   The Golgi apparatus forms the acrosome, a cap-like structure containing hydrolytic enzymes essential for fertilization.
    *   Mitochondria gather in the middle piece to provide energy for tail movement.
    *   A flagellum (tail) develops for motility.

#### 5. Spermiation
*   After spermiogenesis, the sperm heads become embedded in the Sertoli cells (nurse cells) for nourishment. Eventually, they are released from the seminiferous tubules by a process called spermiation.

**Summary of Stages and Ploidy:**
Spermatogonia (2n) --(Mitosis)--> Primary Spermatocyte (2n) --(Meiosis I)--> Secondary Spermatocytes (n) --(Meiosis II)--> Spermatids (n) --(Spermiogenesis)--> Spermatozoa (n)

**Hormonal Regulation:**
Spermatogenesis is initiated at puberty due to the increased secretion of GnRH. GnRH stimulates the anterior pituitary to secrete:
*   **LH (Luteinizing Hormone):** Acts on Leydig cells (interstitial cells) to stimulate the synthesis and secretion of androgens (testosterone).
*   **FSH (Follicle-Stimulating Hormone):** Acts on Sertoli cells and stimulates the secretion of some factors (like androgen-binding protein - ABP) which help in the process of spermiogenesis. FSH also stimulates the secretion of inhibin, which negatively regulates FSH secretion.

Question 9

Q9. Name the hormones involved in regulation of spermatogenesis.

Accepted Answer

The regulation of spermatogenesis is a complex process involving several hormones, primarily from the hypothalamus, anterior pituitary gland, and testes. The key hormones involved are:

1.  **Gonadotropin-Releasing Hormone (GnRH):** Secreted by the hypothalamus. It acts on the anterior pituitary gland, stimulating the release of gonadotropins (LH and FSH).
2.  **Luteinizing Hormone (LH):** Secreted by the anterior pituitary gland. It acts on the Leydig cells (interstitial cells) in the testes, stimulating them to synthesize and secrete androgens, primarily testosterone.
3.  **Follicle-Stimulating Hormone (FSH):** Secreted by the anterior pituitary gland. It acts on the Sertoli cells (nurse cells) in the seminiferous tubules, stimulating them to secrete factors like Androgen-Binding Protein (ABP) and inhibin. ABP concentrates testosterone in the seminiferous tubules, which is essential for spermiogenesis. FSH also promotes the secretion of other factors that aid in spermatogenesis.
4.  **Androgens (Testosterone):** Secreted by the Leydig cells in the testes under the influence of LH. Testosterone is crucial for stimulating and maintaining spermatogenesis, particularly the process of spermiogenesis. It also plays a role in the development of male secondary sexual characteristics.
5.  **Inhibin:** Secreted by the Sertoli cells. It selectively inhibits the secretion of FSH from the anterior pituitary, providing a negative feedback mechanism to regulate spermatogenesis.

Question 10

Q10. Define spermiogenesis and spermiation.

Accepted Answer

Here are the definitions for spermiogenesis and spermiation:

1.  **Spermiogenesis:**
    Spermiogenesis is the final stage of spermatogenesis, which involves the morphological transformation and differentiation of non-motile, spherical haploid spermatids into motile, elongated spermatozoa (sperm). During this process, the spermatid undergoes significant structural changes, including the formation of the acrosome from the Golgi apparatus, condensation of the nucleus, development of the middle piece with mitochondria, and the growth of a flagellum (tail) for motility.

2.  **Spermiation:**
    Spermiation is the process by which mature spermatozoa are released from the Sertoli cells into the lumen of the seminiferous tubules. After spermiogenesis, the heads of the developing sperm remain embedded in the Sertoli cells for nourishment and support. Once fully mature, they detach from the Sertoli cells and are released into the lumen, from where they are transported to the epididymis.

Question 11

Q11. What are the major functions of male accessory ducts and glands?

Accepted Answer

The male accessory ducts and glands play crucial roles in the transport, maturation, and nourishment of sperm, as well as in the formation of semen.

### I. Male Accessory Ducts
The male accessory ducts include the rete testis, vasa efferentia, epididymis, and vas deferens. Their primary functions are:

1.  **Rete Testis:** A network of tubules located in the mediastinum testis. It collects spermatozoa from the seminiferous tubules.
2.  **Vasa Efferentia (Efferent Ductules):** 10-20 fine tubules that emerge from the rete testis and open into the epididymis. They transport sperm from the rete testis to the epididymis.
3.  **Epididymis:** A long, coiled tube located along the posterior surface of each testis. It serves as a site for:
    *   **Sperm Storage:** Stores sperm temporarily.
    *   **Sperm Maturation:** Sperm acquire motility and fertilizing capacity here, a process that takes about 2-3 weeks.
    *   **Sperm Transport:** Propels sperm into the vas deferens.
4.  **Vas Deferens (Ductus Deferens):** A long, muscular tube that ascends from the epididymis into the abdominal cavity, loops over the urinary bladder, and joins with the duct from the seminal vesicle to form the ejaculatory duct. Its main function is to transport mature sperm from the epididymis to the ejaculatory duct during ejaculation.

### II. Male Accessory Glands
The male accessory glands include the seminal vesicles, prostate gland, and bulbourethral glands. Their secretions form the seminal plasma, which mixes with sperm to form semen.

1.  **Seminal Vesicles (Paired):** These glands contribute about 60-70% of the total volume of semen. Their secretion is a viscous, alkaline fluid containing:
    *   **Fructose:** Provides energy for sperm motility.
    *   **Prostaglandins:** Stimulate contractions in the female reproductive tract, aiding sperm transport.
    *   **Clotting Proteins:** Help semen coagulate after ejaculation.
2.  **Prostate Gland (Single):** Located just below the bladder, it surrounds the urethra. It secretes a milky, slightly acidic fluid (about 20-30% of semen volume) containing:
    *   **Citrate:** A nutrient for sperm.
    *   **Enzymes:** Such as acid phosphatase, fibrinolysin, and prostate-specific antigen (PSA), which help in liquefaction of the ejaculate.
3.  **Bulbourethral Glands (Cowper's Glands) (Paired):** Small glands located inferior to the prostate gland. They secrete a clear, viscous, alkaline fluid into the urethra prior to ejaculation. This fluid:
    *   **Lubricates the Urethra:** Reduces friction for sperm passage.
    *   **Neutralizes Acidity:** Cleanses and neutralizes any acidic urine residue in the urethra, protecting sperm from damage.

In summary, the male accessory ducts are primarily involved in the transport and maturation of sperm, while the accessory glands provide the fluid medium (seminal plasma) that nourishes, protects, and facilitates the movement of sperm, thus ensuring successful fertilization.

Question 12

Q12. What is spermatogenesis? Briefly describe the process of spermatogenesis.

Accepted Answer

### What is Spermatogenesis?
Spermatogenesis is the process of formation of mature male gametes, called spermatozoa (sperms), from the immature germ cells (spermatogonia) in the seminiferous tubules of the testes. This process begins at puberty and continues throughout the male's reproductive life. It involves three main phases: multiplication phase, growth phase, and maturation phase.

### Process of Spermatogenesis
Spermatogenesis can be broadly divided into the following stages:

1.  **Multiplication Phase (Mitosis):**
    *   The innermost layer of the seminiferous tubule wall contains undifferentiated primordial germ cells called **spermatogonia** (2n, diploid). These cells are cuboidal and act as stem cells.
    *   At puberty, spermatogonia multiply by repeated mitotic divisions to increase their number. Some of these spermatogonia remain as stem cells, while others differentiate to enter the next phase.

2.  **Growth Phase:**
    *   Some spermatogonia grow in size and accumulate nutrients, becoming larger diploid cells called **primary spermatocytes** (2n).
    *   These primary spermatocytes are ready to undergo meiosis.

3.  **Maturation Phase (Meiosis):**
    *   **Meiosis I:** Each diploid primary spermatocyte (2n) undergoes the first meiotic division (reductional division) to form two equal, haploid cells called **secondary spermatocytes** (n). Each secondary spermatocyte contains 23 chromosomes, each with two chromatids.
    *   **Meiosis II:** Each haploid secondary spermatocyte (n) then rapidly undergoes the second meiotic division (equational division) to form two haploid cells called **spermatids** (n). Thus, from one primary spermatocyte, four haploid spermatids are produced.

4.  **Spermiogenesis (Differentiation):**
    *   The newly formed spermatids are non-motile and spherical. They undergo a process of transformation called **spermiogenesis**, where they differentiate into highly specialized, motile spermatozoa (sperms).
    *   During spermiogenesis, the spermatid undergoes significant morphological changes, including:
        *   Formation of a head (containing the nucleus and acrosome).
        *   Formation of a middle piece (containing mitochondria for energy).
        *   Formation of a tail (for motility).
        *   Loss of most of the cytoplasm.
    *   After spermiogenesis, the sperm heads become embedded in the Sertoli cells (nurse cells) for nourishment and protection.

5.  **Spermiation:**
    *   Finally, the mature spermatozoa are released from the Sertoli cells into the lumen of the seminiferous tubules. This process is called **spermiation**.

The entire process of spermatogenesis takes approximately 64-74 days in humans.

Question 13

Q13. Name the hormones involved in regulation of spermatogenesis.

Accepted Answer

Spermatogenesis is a complex process regulated by several hormones, primarily originating from the hypothalamus, pituitary gland, and testes. The key hormones involved are:

1.  **Gonadotropin-Releasing Hormone (GnRH):** Secreted by the hypothalamus, GnRH acts on the anterior pituitary gland, stimulating the release of gonadotropins.
2.  **Luteinizing Hormone (LH):** Secreted by the anterior pituitary gland, LH acts on the Leydig cells (interstitial cells) in the testes. It stimulates Leydig cells to synthesize and secrete androgens, primarily testosterone.
3.  **Follicle-Stimulating Hormone (FSH):** Also secreted by the anterior pituitary gland, FSH acts on the Sertoli cells (sustentacular cells) in the seminiferous tubules. FSH stimulates Sertoli cells to secrete some factors, including Androgen Binding Protein (ABP), which concentrates testosterone within the seminiferous tubules, and inhibin.
4.  **Androgens (Testosterone):** Secreted primarily by the Leydig cells under the influence of LH, testosterone is essential for spermatogenesis. It acts on Sertoli cells to promote the differentiation of spermatids into spermatozoa. Testosterone also plays a crucial role in the development of male secondary sexual characteristics.
5.  **Inhibin:** Secreted by Sertoli cells in response to high sperm count or high FSH levels, inhibin selectively suppresses FSH secretion from the anterior pituitary, providing a negative feedback mechanism.

Question 14

Q14. Define spermiogenesis and spermiation.

Accepted Answer

### Spermiogenesis
Spermiogenesis is the process of transformation of non-motile, spherical, haploid **spermatids** (formed after meiosis II) into highly motile, elongated, and specialized **spermatozoa** (sperms). This process involves significant morphological changes within the spermatid, including:
*   Formation of the acrosome from the Golgi apparatus.
*   Condensation and elongation of the nucleus.
*   Formation of the middle piece with mitochondria arranged spirally.
*   Development of a flagellum (tail) for motility.
*   Shedding of excess cytoplasm.
During spermiogenesis, the developing sperm heads become embedded in the Sertoli cells for nourishment and support.

### Spermiation
Spermiation is the final step in spermatogenesis, where the mature spermatozoa are released from the Sertoli cells into the lumen of the seminiferous tubules. After undergoing spermiogenesis, the fully formed spermatozoa detach from the Sertoli cells and are then transported out of the testes through the male accessory ducts.

Question 15

Q15. Draw a labelled diagram of a section view of seminiferous tubule.

Accepted Answer

A labelled diagram of a section view of a seminiferous tubule should clearly illustrate the various cell types involved in spermatogenesis and their arrangement, as well as the surrounding structures. The diagram should include the following labels:

1.  **Seminiferous Tubule Lumen:** The central cavity where mature spermatozoa are released.
2.  **Spermatogonia (Germinal Epithelium):** Diploid, undifferentiated germ cells located at the outermost layer of the tubule wall, near the basement membrane. These are the stem cells that undergo mitosis.
3.  **Primary Spermatocytes:** Larger diploid cells formed from spermatogonia, undergoing Meiosis I. Located closer to the lumen than spermatogonia.
4.  **Secondary Spermatocytes:** Haploid cells formed after Meiosis I, typically short-lived and thus less frequently observed. Located closer to the lumen than primary spermatocytes.
5.  **Spermatids:** Haploid, spherical cells formed after Meiosis II, undergoing spermiogenesis. Located very close to the lumen, often embedded in Sertoli cells.
6.  **Spermatozoa (Sperms):** Mature, motile male gametes with distinct head, middle piece, and tail, released into the lumen.
7.  **Sertoli Cells (Sustentacular Cells):** Large, pyramidal or columnar cells extending from the basement membrane to the lumen. They provide nourishment, support, and protection to developing germ cells, and also secrete ABP and inhibin. Their nuclei are typically large and oval.
8.  **Basement Membrane:** The layer separating the seminiferous tubule from the interstitial space.
9.  **Interstitial Space (or Interstitial Tissue):** The region outside the seminiferous tubule.
10. **Leydig Cells (Interstitial Cells):** Located in the interstitial space, these cells synthesize and secrete androgens (testosterone).
11. **Blood Vessels:** Present in the interstitial space, supplying nutrients and hormones.

The diagram should show the progression of germ cells from the periphery (spermatogonia) towards the lumen (spermatozoa), with Sertoli cells spanning this entire region and Leydig cells in the surrounding interstitial tissue.

Question 16

Q16. What are the major functions of placenta?

Accepted Answer

The placenta is a temporary organ that develops in the uterus during pregnancy. It is a vital connection between the mother and the developing fetus, facilitating exchange of substances and performing crucial endocrine functions. It is formed by the interdigitation of chorionic villi (fetal part) and uterine tissue (maternal part).

Chapter 3: Human Reproduction