21.1 Male Reproductive System

Question 1

1º spermatocytes

Answer 1

Primary spermatocytes (1º spermatocytes) are diploid cells (2n) that arise from spermatogonia through mitotic division. They are an essential stage in spermatogenesis, the process of sperm cell development.

Question 2

2º spermatocytes

Answer 2

Secondary (2°) spermatocytes are haploid (n) cells formed from primary (1°) spermatocytes after Meiosis I during spermatogenesis. They contain 23 chromosomes and are located in the seminiferous tubules of the testes. These cells quickly undergo Meiosis II to produce spermatids, which later mature into spermatozoa. Due to their short lifespan, secondary spermatocytes are rarely observed in histological slides.

Question 3

acrosome

Answer 3

The acrosome is a specialized cap-like structure covering the head of a sperm cell. It is derived from the Golgi apparatus and contains enzymes (such as hyaluronidase and acrosin) that help the sperm penetrate the egg’s outer layers during fertilization. The acrosome reaction, triggered upon contact with the egg, releases these enzymes, allowing the sperm to fuse with the egg membrane. This structure is essential for successful fertilization.

Question 4

bulbourethral glands

Answer 4

The bulbourethral glands (also called Cowper’s glands) are two small, pea-shaped exocrine glands located beneath the prostate gland on either side of the urethra. They secrete a clear, mucus-like fluid that lubricates the urethra and neutralizes acidic traces of urine before ejaculation. This pre-ejaculatory fluid helps create a more favorable environment for sperm survival and movement.

Question 5

ejaculatory duct

Answer 5

The ejaculatory duct is a short duct formed by the union of the vas deferens and the seminal vesicle duct. There are two ejaculatory ducts, one on each side, which pass through the prostate gland and open into the prostatic urethra. Their main function is to transport sperm and seminal fluid into the urethra during ejaculation.

Question 6

epididymis

Answer 6

The epididymis is a long, coiled tube located at the back of each testis, responsible for the storage, maturation, and transport of sperm. It consists of three parts: the head, body, and tail. Sperm enter the epididymis from the testes as immature and non-motile cells and gain motility and fertilization ability as they pass through. The epididymis also absorbs excess fluid and secretes substances that help sperm mature before being transported to the vas deferens for ejaculation.

Question 7

FSH

Answer 7

In males, Follicle-Stimulating Hormone (FSH) is essential for spermatogenesis (sperm production). It is released by the anterior pituitary gland and acts on the Sertoli cells in the seminiferous tubules of the testes. FSH stimulates these cells to produce androgen-binding protein (ABP), which helps maintain high testosterone levels necessary for sperm development. It also promotes the maturation of sperm and supports the overall function of the testes. FSH secretion is regulated by Gonadotropin-Releasing Hormone (GnRH) and controlled through negative feedback by inhibin, a hormone produced by Sertoli cells

Question 8

glans penis

Answer 8

The glans penis is the rounded, sensitive tip of the penis, covered by the prepuce (foreskin) in uncircumcised males. It contains numerous nerve endings, making it highly sensitive to stimulation. The glans plays a crucial role in sexual arousal and ejaculation. It is also where the external urethral orifice is located, allowing for the passage of urine and semen.

Question 9

GnRH

Answer 9

In males, Gonadotropin-Releasing Hormone (GnRH) is produced by the hypothalamus and stimulates the anterior pituitary gland to release Follicle-Stimulating Hormone (FSH) and Luteinizing Hormone (LH). FSH promotes spermatogenesis by acting on Sertoli cells in the testes, while LH stimulates Leydig cells to produce testosterone, which is essential for sperm production and the development of male secondary sexual characteristics. The release of GnRH is regulated by feedback mechanisms involving testosterone and inhibin, ensuring proper reproductive function.

Question 10

interstitial cells

Answer 10

Interstitial cells (also known as Leydig cells) are found in the interstitial tissue of the testes, between the seminiferous tubules. These cells are responsible for producing testosterone in response to stimulation by Luteinizing Hormone (LH) from the anterior pituitary. Testosterone is crucial for the development of male secondary sexual characteristics, such as deep voice, facial hair, and muscle growth, as well as for supporting spermatogenesis.

Question 11

LH

Answer 11

In males, Luteinizing Hormone (LH) is produced by the anterior pituitary gland and plays a crucial role in reproductive health. LH stimulates the Leydig cells in the testes to produce testosterone, which is vital for the development of male secondary sexual characteristics, such as facial hair, deep voice, and muscle growth. Testosterone also supports spermatogenesis (sperm production) and overall male fertility. LH secretion is regulated by Gonadotropin-Releasing Hormone (GnRH) from the hypothalamus and controlled by negative feedback from testosterone.

Question 12

prostaglandins

Answer 12

In males, prostaglandins are present in semen and play an important role in fertility. They help promote smooth muscle contractions in the female reproductive tract, specifically in the uterus and cervix, which aids in the movement of sperm toward the egg. This action enhances the chances of successful fertilization. Additionally, prostaglandins can help in the transport of semen through the male reproductive tract during ejaculation.

Question 13

prostate gland

Answer 13

The prostate gland is a small, walnut-shaped gland located just below the bladder in males, surrounding the urethra. Its main function is to produce a significant portion of the seminal fluid (about 20-30%), which nourishes and transports sperm during ejaculation. The fluid produced by the prostate contains enzymes, citric acid, and other substances that help activate sperm, maintain their motility, and protect them in the acidic environment of the female reproductive tract. The prostate also plays a role in the regulation of urine flow, as it surrounds part of the urethra.

Question 14

seminal vesicle

Answer 14

The seminal vesicles are two glandular structures located behind the bladder in males, near the prostate gland. They produce a significant portion of semen, contributing about 60-70% of its volume. The fluid secreted by the seminal vesicles is rich in fructose, which provides energy for sperm, as well as other substances like prostaglandins, which aid in sperm motility and help the sperm navigate the female reproductive tract. The seminal vesicles also produce proteins that help in the coagulation and later liquefaction of semen after ejaculation, optimizing conditions for fertilization.

Question 15

seminiferous tubules

Answer 15

The seminiferous tubules are highly coiled structures located within the testes and are the site of spermatogenesis (sperm production). These tubules contain Sertoli cells, which support and nourish developing sperm cells, and are lined with germ cells that undergo division and maturation to become sperm. The seminiferous tubules are connected to the epididymis, where sperm mature and are stored. The process of spermatogenesis within the seminiferous tubules is regulated by hormones such as Follicle-Stimulating Hormone (FSH) and testosterone, which are essential for the development and maturation of sperm cells.

Question 16

Sertoli cells

Answer 16

Sertoli cells are specialized cells found in the seminiferous tubules of the testes. Often referred to as “nurse cells,” their primary role is to support and nourish developing sperm cells during spermatogenesis. Sertoli cells provide structural support and create a protective environment for the germ cells. They also produce androgen-binding protein (ABP), which helps concentrate testosterone in the tubules, essential for sperm development. Additionally, Sertoli cells secrete inhibin, a hormone that helps regulate Follicle-Stimulating Hormone (FSH) levels through negative feedback, ensuring proper spermatogenesis.

Question 17

spermatid

Answer 17

A spermatid is a haploid cell that is the result of Meiosis II during spermatogenesis. It is formed from a secondary spermatocyte and has half the chromosome number of a typical cell (23 chromosomes in humans). Spermatids are not yet mature sperm but are in the final stages of development.

Question 18

spermatogenesis

Answer 18

Spermatogenesis is the process by which sperm cells are produced in the testes. It occurs within the seminiferous tubules and involves several stages of cell division and maturation:

Spermatogonia (diploid stem cells) undergo mitosis to produce primary spermatocytes.
Primary spermatocytes (diploid) undergo Meiosis I to form secondary spermatocytes (haploid).
Secondary spermatocytes then undergo Meiosis II, resulting in the formation of spermatids (haploid).
Spermatids undergo spermiogenesis, a maturation process where they develop tails (flagella) and streamline their shape to become spermatozoa (mature sperm).
The entire process takes about 64–72 days, and the resulting sperm are stored in the epididymis until ejaculation. The process is regulated by hormones like FSH, LH, and testosterone.

Question 19

spermatogonium

Answer 19

A spermatogonium is a diploid stem cell found in the seminiferous tubules of the testes. It is the initial cell in spermatogenesis, the process of sperm production. Spermatogonia undergo mitosis to produce more spermatogonia, ensuring a continuous supply of stem cells, and also give rise to primary spermatocytes, which will go through meiosis to eventually form sperm.

Spermatogonia are the starting point for sperm production and are crucial for maintaining the male germ cell line throughout life.

Question 20

testes

Answer 20

The testes (also called testicles) are the male reproductive organs responsible for producing sperm and testosterone, the primary male sex hormone. Located in the scrotum, outside the body cavity, the testes are composed of tightly coiled seminiferous tubules, where spermatogenesis (sperm production) occurs

Question 21

urethra

Answer 21

The urethra is a tube that carries urine from the bladder to the outside of the body. In males, the urethra also serves as a passageway for semen during ejaculation. It is divided into three sections: the prostatic urethra, which runs through the prostate gland; the membranous urethra, which passes through the pelvic floor muscles; and the penile urethra, which runs through the penis.

In males, the urethra plays a dual role in both the urinary and reproductive systems. During urination, it expels urine, while during ejaculation, it transports sperm mixed with seminal fluid from the seminal vesicles, prostate gland, and bulbourethral glands.

Question 22

vas deferens

Answer 22

The vas deferens (also known as the ductus deferens) is a long, muscular tube that transports sperm from the epididymis to the urethra during ejaculation. It is part of the male reproductive system and plays a crucial role in sperm maturation and delivery. The vas deferens is responsible for carrying mature sperm from the epididymis, where sperm are stored and gain motility, to the ejaculatory duct, where sperm are mixed with seminal fluid before being expelled through the urethra. During ejaculation, the smooth muscle of the vas deferens contracts to propel sperm forward, a process known as peristalsis.