Chapter 27: The Male Reproductive System

Flashcards reviewing the anatomy, physiology, and hormonal control of the male reproductive system, including spermatogenesis and semen.

What is biparental reproduction?

Offspring receives genes from two parents and is not genetically identical to either.

What is the role of the male reproductive system?

To produce sperm and introduce it into the female body using the penis as a copulatory organ.

What are the primary sex organs (gonads)?

The testes, which produce gametes.

What are secondary sex organs?

Organs other than gonads that are necessary for reproduction, such as ducts, glands, and the penis in males, and uterine tubes, uterus, and vagina in females.

Where are the external and internal genitalia located?

External genitalia are located in the perineum and are externally visible, while internal genitalia are located in the pelvic cavity (except testes and associated ducts).

Name some secondary sex characteristics.

Features that distinguish the sexes and influence mate attraction, such as pubic/axillary hair, scent glands, facial hair (males), body fat distribution (females), etc.

How is chromosomal sex determined?

By the type of sperm that fertilizes the mother's egg: X-carrying sperm results in a female (XX), while Y-carrying sperm results in a male (XY).

What happens to the mesonephric and paramesonephric ducts in males during prenatal development?

Mesonephric (wolffian) ducts develop into the reproductive tract, while paramesonephric (müllerian) ducts degenerate.

What is the role of the SRY gene?

The SRY gene (sex-determining region of Y chromosome) codes for testes-determining factor (TDF), which initiates development of testes.

What happens in the absence of a Y chromosome?

No TDF is produced, and the cortex of the embryonic gonads develops into ovaries.

Why is estrogen not responsible for the female differentiation?

Female development of a fetus occurs whenever there is an absence of androgen hormones, Mothers hormones are always high during pregnancy.

Name the homologous structures between male and female external genitalia.

Penis is homologous to the clitoris, and the scrotum is homologous to the labia majora.

What is the perineum?

The diamond-shaped area between the thighs bordered by the pubic symphysis, ischial tuberosities, and coccyx.

List the three mechanisms the scrotum has to regulate temperature of the testes.

Cremaster muscle, dartos muscle, and pampiniform plexus.

What is the function of the pampiniform plexus?

A countercurrent heat exchanger that removes heat from the descending arterial blood, cooling the blood before it reaches the testis.

Describe the structure of the testes.

Oval and slightly flattened, covered by tunica vaginalis and tunica albuginea, with connective tissue septa dividing the testes into lobules.

Where are sperm produced?

In the seminiferous tubuleswithin each lobule of the testes.

What is the role of sustentacular (Sertoli) cells?

To protect germ cells and promote their development, providing nutrients, waste removal, growth factors, and other needs.

Where is testostrone produced?

Interstitial cells (Leydig) between tubules produce testosterone.

Describe the path of spermatic ducts from the testis to the urethra.

Efferent ductules -> duct of the epididymis -> ductus (vas) deferens -> ejaculatory duct -> urethra.

List the three regions of the male urethra.

Prostatic, membranous, and spongy (penile) urethra.

Name the three sets of accessory glands in the male reproductive system.

Seminal vesicles, prostate gland, and bulbourethral glands.

What is the function of bulbourethral (Cowper) glands?

During sexual arousal, they produce a clear slippery fluid that lubricates the head of the penis and neutralizes the acidity of residual urine in the urethra.

What are the components of semen?

Seminal vesicle fluid, prostatic fluid, sperm, and spermatic duct secretions.

Describe the contributions of the seminal vesicles and prostate gland to semen composition.

Seminal vesicles contribute viscous yellowish fluid containing fructose, citrate, prostaglandins, and proseminogelin. The prostate produces a thin, milky white fluid containing calcium, citrate, phosphate ions, clotting enzyme, and serine protease (PSA).

How does semen promote fertilization?

Stickiness of semen entangles the sperm, sticks to the inner wall of the vagina and cervix, and promotes uptake of sperm-laden clots into the uterus. Prostaglandins may thin cervical mucus and stimulate uterine contractions.

Explain the endocrine control of puberty in males.

Hypothalamus produces GnRH, which stimulates the anterior pituitary to secrete FSH and LH. FSH stimulates sustentacular cells, and LH stimulates interstitial cells to produce testosterone.

What is the role of inhibin?

Inhibin from sustentacular cells suppresses FSH output from the pituitary, reducing sperm production without reducing LH and testosterone secretion.

What is spermatogenesis?

The process of sperm production in seminiferous tubules.

What are the three principal events in spermatogenesis?

Division and remodeling of germ cells, reduction of chromosome number by one-half, and shuffling of genes.

Compare and contrast mitosis and meiosis.

Mitosis produces two genetically identical daughter cells, while meiosis produces four gametes (haploid cells) with half the DNA of the diploid body cells.

Outline the stages of meiosis.

Meiosis I (prophase I, metaphase I, anaphase I, telophase I) and meiosis II (prophase II, metaphase II, anaphase II, telophase II).

Describe spermiogenesis.

Changes that transform spermatids into spermatozoa, including discarding excess cytoplasm and growing tails.

Describe the structure of spermatozoa.

Has a head (nucleus, acrosome, basal body) and tail (midpiece, principal piece, endpiece).

What is the function of the acrosome?

Enzyme cap over the apical half of the nucleus that contains enzymes that penetrate the egg.

Where do primordial germ cells form and what do they become?

Primordial germ cells form in the yolk sac of the embryo, colonize gonadal ridges, and become spermatogonia after arriving.

Explain the process of spermatogenesis from spermatogonia to spermatozoa.

Spermatogonia divide by mitosis, one daughter cell remains as a stem cell (Type A spermatogonium), the other enlarges to become a primary spermatocyte. Primary spermatocytes undergo meiosis I to form secondary spermatocytes, which then undergo meiosis II to form spermatids, which then undergo spermiogenesis to become spermatozoa.

What is the blood-testis barrier (BTB) and what is its function?

Sustentacular cells protect spermatocytes from the body’s immune system via the blood testis barrier (BTB).