L18a: Male Reproductive System and Spermatogenesis

Where does spermatogenesis occur in the testis?

In the seminiferous tubules.

Which cells are primarily responsible for testosterone production in the testis?

Leydig (interstitial) cells.

What structure transports sperm from the tail of the epididymis to the urethra?

Ductus deferens.

where do sperm aquire some motility and gain better fertility?

head and body of the epididymis

what is the function of the acessory sex glands?

prepare sperm for long journey and surface coating

what is the function of the testis?

gametogenic and testosterone production

where are testes housed?

within the scrotum

what does the testicular vein form?

pampiniform plexus

What is the function of the pampiniform plexus?

Temperature regulation and counter-current exchange of testosterone.

what does the arrangement of the pampinoform plexus allow for?

1. temperature regulation

2. countercurrent exchange of testosterone

what is the level of testosterone when the artery takes blood to the testes?

low concentration

what is the level of testosterone when the veins take blood away from the testes?

high concentration

location of epididymis

dorsal to the testis

the epididymis is the site of…

fluid absorption and final steps of sperm maturation

location of ductus deferens

originates at the tail of the epididymis and ends at the beginning of the urethra

what is the function of the ductus deferens?

transports the semen out of the epididymis and into pelvic urethra

what are the accessory glands of the male?

1. ampulla of ductus deferens

2. seminal vesicles

3. prostate

4. bulbourethral glands

what is the functiono of the male accessory sex glands?

produce liquid portion of semen that will provide optimal environment and nutrition for spermatozoa

how is the penis classified in dogs and horses?

musculocavernous

how is the penis classified in ruminants and pigs?

fibroelastic

penis function

serves as copulatory organ and passageway for semen and urine

what systems is the penis part of?

reproductive and urinary

what are the main organs involved in male reproduction?

1. hypothalamus

2. pituitary gland

3. testicles

what hormones are involved in male reproduction?

1. GnRH

2. LH

3. FSH

4. E2

5. testosterone

what must have occurred for the reproduction cycle to be fully functional?

animal must have undergone puberty

puberty

the process of acquiring reproductive competence

what two nuclei do the hypothalamus contain?

1. tonic center

2. surge center

what nuclei are present in the hypothalamus of the male?

ONLY TONIC CENTER

what abolishes the male’s fetus surge center?

fetal testosterone

what happens once male fetus testosterone enters the brain?

it is transformed into estradiol which minimizes the function of the surge center

what does the tonic center produce?

GnRH

what occurs after puberty?

hypothalamus released GnRH in a pulsatile fashion every few hours in the mature male

what follows the GnRH pulses in the male?

• pulse of LG

• FSH release from the anterior pituitary gland

tubular compartment

site of spermatogenesis

intersitial compartment

site of testosterone production

what cells are located in the tubular compartment?

sertoli cells

what cells are located in the interstitial compartment?

leydig cells

what type of receptors do leydig cells have?

LH

what hormone do leydig cells produce?

testosterone

what receptors doe sertoli cells have?

FSH receptors

what do sertoli cells produce?

produce spermatogenic substances and inhibin

what hormone is essential to stimulate/maintain spermatogenesis?

testosterone

what happens to testosterone once it diffuses into sertoli cells?

conversted to active dihydrostestosterone and partly estradiol

spermatogenic substances

androgen binding proteins that maintain high tubular testosterone despite pulsatile release

what are examples of spermatogenic substances?

1. activin

2. opioids

3. growth factors

4. oxytocin

5. nutrient-binding proteins

inhibin

selectively inhibits FSH release from anterior pituitary by creating negative feedback

what are the general effects of testosterone?

1. growth of PRIMARY male sex characteristics

2. development of SECONDARY male characteristics

what is circumference measurement of the scrotum a good indicator for?

sperm producing ability

what are the major hormones produced by the anterior pituitary?

LH and FSH

spermatogenesis

division and transformation from diploid stem cell to haploid spermatozoon

when does spermatogenesis conclude?

after differentiation of spherical spermatids into highly specialized spermatozoa

where does spermatogenesis take place?

seminiferous tubules

spermatogonia

immature germ cells located near the basement membrane of seminiferous tubule

what are the phases of spermatogenesis?

1. mitosis

2. meiosis

3. differentiation

what are the phases of capacitation?

1. golgi phase

2. cap phase

3. acrosomal phase

4. maturation phase

Define capacitation.

Final functional maturation of sperm in the female tract, enabling fertilization.

Where does capacitation complete?

In the isthmus of the oviduct.

What are the three parts of the epididymis?

Head, body, and tail.

What covers the testis externally and around the testes?

Scrotum; testis also has tunica albuginea (capsule) and tunica vaginalis (serous covering).

What temperature is required for spermatogenesis relative to body temperature?

About 4–6°C cooler than body temperature.

What divides the testicular parenchyma into lobules?

Connective tissue septae.

What is the rete testis?

A network that collects contents from seminiferous tubules and connects to efferent ducts.

What forms the head of the epididymis?

Efferent ductules from the rete testis.

What is the time frame for spermatogenesis in most domestic species?

Approximately 40–60 days.

What is the role of mitosis in spermatogenesis?

Proliferation of spermatogonia to produce more germ cells and primary spermatocytes.

What is meiosis I in spermatogenesis, and what is produced?

Primary spermatocytes divide to form secondary spermatocytes (genetic diversity via crossing over).

what is Meiosis II in spermatogenesis?

primary spercatocytes produces secondary spermatocytes

what is formed from secondary spermatocytes during Meiosis II?

haploid spermatids

What is the end product of spermatogenesis?

fully differentiated, high specialized sperm with a head, flagellum, and tail

What is the tail end of the epididymis important for?

Maturation and storage of sperm; tail is where maturation reaches fertilizing capability.

sperm capacitation

sperm spend time in the female reproductive tract to acquire maximum fertility

capacitation includes

1. final functional maturation of sperm

2. hyperactivation of flagellar activity

3. acrosome reaction

what is 7?

epidiymal head

what is 5?

rete testis

what is 8?

ductus deferens

what is 6?

seminiferous tubules

what is 1?

differentiation

what is 4?

meiosis II

what is 3?

meiosis I

what is 2?

mitosis

tunica albuginias

connective tissue that divides testicles into functional lobules

what is the flow of sperm?

1. tunica albuginias

2. convolutes seminiferous tubules

3. straight seminiferous tubules

4. rete testes

5. efferent ductules

6. head of epidiymis

7. ductus deferens

8. seminal vesicles

9. prostate gland

10. urethra

what is 1?

head of epidiymus

what is 2?

pampiform plexus

what is 3?

body of epididymis

what is 4?

tail of epidiymis

what are the orange boxes indicating?

tail of epididymis

what are the orange arrows pointing at?

ductus deferens