Male Reproductive System and Spermatogenesis

Flashcards covering the male reproductive system, spermatogenesis, Sertoli and Leydig cells, hormonal control, epididymis, and accessory glands.

What are the three main components of the male reproductive system?

Testes, male genital tract, and accessory glands

What structures produce spermatozoa and secrete testosterone?

Testes (specifically, seminiferous tubules and Leydig cells, respectively)

What is the function of the male genital tract?

Ensures maturation and transport of spermatozoa

Name the accessory glands of the male reproductive system.

Seminal vesicles, prostate gland, and Cowper's glands

How is semen formed?

Accessory glands secrete sperm mixed with seminal fluid, forming semen.

Shape of testes?

Ellipsoid

Where are the testes located?

In the scrotum

What is the optimal temperature for the testes?

2–4°C lower than body temperature

Where is the epididymis applied?

Applied on the postero-superior region of each testis

Name the fibrous capsule that covers the testes?

Tunica albuginea

What is the tunica albuginea crossed by?

Testicular vessels

What is the tunica albuginea made of?

Collagen fibers and some smooth muscle cells

The main thing the tunica albuginea is innervated?

Andrenergic terminations

How does the tunica albuginea move and why?

Contracting rhythmically and spontaneously. helps propel sperm and seminal fluid

Where does spermatogenesis occur?

Seminiferous tubules

What cells synthesize androgens in the testes?

Leydig cells

On the upper edge of testis, the tunica thickens and sinks deeply to form what?

Body of Highmore

What is the BoH perforated by and what does that form?

Perforated by vessels and channels, forming the rete testis.

Between the tunica albuginea and the BoH…

There is a division or septa delimiting 200-300 testicular lobules

What is the approximate duration of spermatogenesis in humans?

74 days

What are the three phases of spermatogenesis?

Mitotic proliferation (spermatogonia), meiotic division (spermatocytes), and spermiogenesis (cytodifferentiation of spermatids)

What is the role of Type Ad spermatogonia?

Maintain stem cell supply and undergo proliferation

What is the role of Type Ap spermatogonia?

Divide mitotically, form cell clones, and differentiate into type B spermatogonia

What is the role of apoptosis in spermatogenesis?

Reduces the number of cells and regulates mitotic division and differentiation

What do type B spermatogonia produce?

Primary spermatocytes (spermatocyte I)

What are the products of the first meiotic division?

Two haploid spermatocytes II

What is the DNA content of a spermatocyte I after replication?

46 chromosomes, 2 chromatids = 4C DNA

What is the DNA content of a spermatid after the second meiotic division?

23 chromosomes, 1 chromatid = 1C DNA

What is spermiogenesis?

The transformation of round spermatids into motile spermatozoa

What is the function of the acrosome?

Contains hydrolytic enzymes important for the acrosomal reaction during fertilization

What enzymes are present in the acrosome?

Hyaluronidase and acrosin

Describe the successive stages of developing spermatids.

Round spermatids, elongating spermatids, elongated spermatids, mature spermatids close to spermatozoa

What proteins replace histones during nuclear reorganization?

Transition proteins and protamines

Which centriole initiates zygote division?

Proximal centriole

What forms the axoneme?

Distal centriole

What is the function of the mitochondrial sleeve?

Provide energy necessary for flagellar movement

What cells phagocytose residual bodies?

Sertoli cells

What part of the spermatozoon ensures the connection between the head and the flagellum?

Connecting piece (Neck)

What is teratospermia?

An ejaculate in which most of the spermatozoa have multiple morphological abnormalities

What is oligospermia?

An ejaculate in which the concentration is less than 20 million/ml

What is azoospermia?

Absence of spermatozoa in the ejaculate

What is asthenospermia?

When the percentage of motile sperms is too low, or their speed is significantly reduced

What are the two anatomical and functional compartments delimited in the seminiferous tubules?

Peripheral basal compartment and central adluminal compartment

Name two functions of Sertoli cells.

Development and regulation of spermatogenesis

What hormone receptors do Sertoli cells contain?

FSH membrane receptors and testosterone nuclear receptors

Where are Leydig cells located?

Interstitial spaces between seminiferous tubules

What is the main function of Leydig cells?

Synthesize steroid hormones and testicular androgens

What percentage of plasma testosterone do Leydig cells secrete?

~95%

Name 3 major roles of testosterone.

Activates hypophyseal-testicular axis, differentiates male genital organs, promotes secondary sex characteristics and male behavior, maintains germ line integrity, initiates and maintains spermatogenesis

What is the basic endocrine regulator of reproduction?

Hypothalamo-hypophyseal axis

What hormones does GnRH control the secretion of?

LH (luteinizing hormone) and FSH (follicle stimulating hormone)

What is the action of LH on Leydig cells?

Stimulates testosterone production from cholesterol

What is the action of FSH on Sertoli cells?

Stimulates adenylyl cyclase activity, RNA synthesis, testicular fluid production, and protein synthesis

What hormone exerts negative feedback on the pituitary to reduce serum FSH?

Inhibin

What hormone inhibits GnRH secretion at the hypothalamus?

Testosterone

What cells secrete factors regulating Sertoli activity?

Peritubular cells

What is the role of P-Mod-S?

Stimulates Sertoli cells to produce ABP, transferrin, and inhibin

What factors do germ cells secrete to regulate Sertoli function?

Growth factors like EGF

What two interleukins control DNA replication of spermatogonia and primary spermatocytes?

IL-1 and IL-6

What is the function of the epididymis?

Sperm maturation, transport, secretion, reabsorption, and metabolism

What drives sperm progression through the extratesticular ducts?

Intraluminal pressure and tunica albuginea contractions

What structures does sperm progress through, post-spermiation to ejaculation?

Seminiferous tubules → straight tubules → rete testis → efferent ductules → epididymis → vas deferens → ejaculatory duct → urethra

What is reabsorbed in the epididymis?

90% of testicular fluid, ions, and proteins (e.g., ABP, transferrin)

What changes occur in the plasma membrane during maturation of spermatozoa?

Stabilized via lipid changes (↓ phospholipids, ↑ cholesterol = decapacitation)

What fluids do seminal vesicles secrete?

Fructose-rich fluid and prostaglandins

What is the function of the secretions from the seminal vesicles?

Fructose provides energy for sperm motility, while prostaglandins stimulate smooth muscle contractions

Where is the prostate gland located?

Below the bladder, anterior to the rectum

What is the function of the Bulbourethral gland secretions?

Lubricates urethra and neutralizes acidity from urine residue