Testes, Spermatogenesis, Endocrine Control

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What are the two mechanisms for testicular thermoregulation?

pampiniform plexus and scrotum

How does the pampiniform plexus function to regulate temperature?

allows vascular countercurrent heat exchange

How does the scrotum function to regulate temperature?

thermosensitive nerves influence scrotal sweating to cool off and tunica dartos m. contracts to bring testis closer to body to warm up

What is the primary reproductive organ in males?

testis

What is the function of the testis?

produces spermatozoa, hormones, proteins, and fluids

What is the temperature range that the testes must be in for spermatogenesis to occur?

4-6 degrees celcius cooler than body temp

What are the four layers of the testes?

capsule, parenchyma, mediastinum, rete tubules

What are the two portions of the capsule of testes?

visceral vaginal tunic and tunica albuginea

What are the two compartments of the parenchyma of the testes?

tubular and interstitial compartments

What is included in the tubular compartment?

seminiferous tubules, and all materials IN it; sertoli cells, developing sperm cells, tubular fluid

What is included in the interstitial compartment?

all cells and materials OUTSIDE of seminiferous tubules; lymph vessels, capillaries, connective tissue, interstitial cells of leydig

What is the blood-testis barrier?

specialized, highly tight physical barrier formed by junctional complexes (tight junctions) between neighboring sertoli cells in the seminiferous tubules

What is the function of the blood-testis barrier?

haploid cells are “foreign” to immune system so limits access to adluminal compartment to protects against immune cell attacks

What is the pathway out of the testis?

seminiferous tubules, rete tubules, efferent duct, head, body, tail of epididymis, ductus deferens

What is another term for rete tubule?

mediastinum

What describes the endocrine regulation of males?

low amplitude pulse of GnRH every couple hours with no LH surge

What describes the endocrine regulation of females?

periodic large episodes of GnRH followed by LH surge

True or false: Males have both a surge and tonic center.

False; male don’t have a surge center, females have both

What does LH stimulate?

leydig cells to produce T and E2

What does FSH stimulate?

sertoli cells to produce inhibin and DHT

What is included in spermatogenesis?

all cell divisions and all morphologic changes that take place within the seminiferous epithelium

What are the three phases of spermatogenesis?

proliferation, meiotic, differentiation

What is another word for differentiation?

spermiogenesis

What are the phases of differentiation?

golgi, cap, acrosomal, maturation

What happens during the golgi phase?

acrosomic vesicle formation with well developed golgi apparatus in spherical spermatid

What is the proximal centriole?

point of tail attachment

What is the distal centriole?

gives rise to axoneme

What is the axoneme?

central portion of tail

What happens during the cap phase?

acrosomic vesicle spreading over the nucleus

What happens during the acrosomal phase?

acrosome covers 2-thirds of anterior nucleus, annulus are formed, and manchette develops near the posterior nucleus

What happens during the maturation phase?

final assembly while mitochondria form a spiral helix around the flagellum to define middle piece and entire spermatozoa is covered with a plasma membrane

What does the manchette give rise to?

post-nuclear cap

What does the annulus give rise to during the maturation phase?

forms the junction between middle and principle piece of tail

What is spermiation?

release of fully differentiated spermatozoa into the lumen of seminiferous tubules

What is included in a spermatozoa?

head and tail

What is included with the head of spermatozoa?

nucleus, acrosome, post-nuclear cap

What is included with the tail of spermatozoa?

capitulum, middle, principle, and terminal pieces

What is the function of the capitulum in the tail of spermatozoa?

fits into the implantation sockets of head

What is the function of laminated columns in neck region of spermatozoa?

give tail and middle piece flexibility allowing side to side movement of sperm

What is the fibrous helix of the spermatozoa?

surrounds axoneme and outer course fibers, provides tail with flexibility

What hormone in the male is known for having frequent intermittent episodes?

GnRH

What hormone in the male is known for having frequent episodes every 3-6 hours?

LH

What hormone in the male is known for having lower amplitude but longer duration?

FSH