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What is the arterial supply of the testicle?
testicular artery, cremasteric artery (external spermatic), deferential vasal artery
What happens in countercurrent heat exchange?
veins exchange heat with the arterial supply
What cell types are present in the seminiferous tubules?
sertoli cells (like epithelium), spermatagonia (germ cells), spermatocytes
What cell types are present in the interstitium of the testes?
Leydig cells, Mast cells, macrophages, nerves, blood, lymph, fibroblastic supporting cells
Describe the histologic appearance of Leydig cells.
Rich in mitochondria and SER
What are the two main functions of the testes?
spermatogenesis and secretion of testosterone.
Describe the 3 main functions of Sertoli cells
provide nutrients to the differentiating sperm, create the blood-testes barrier, secrete and aqueous fluid into the lumen which helps transport sperm to the epididymis
What is the function of Leydig cells?
synthesis and secretion of testosterone
From where is GnRH released, and what is its target?
from the hypothalamus (arcuate nucleus) to the anterior pituitary
From where is LH released, and what is its target?
from the anterior pituitary to the Leydig cells of the testes
From where is FSH released, and what is its target?
from the anterior pituitary to the Sertoli cells of the testes
Aside from spermatogenesis, what other important pathways do Sertoli cells activate?
Inhibin and Activin
What blood supply does GnRH travel through?
hypophyseal portal blood
Why is it best to test a male's testosterone in the morning?
pulsatile secretion of GnRH occurs in the morning
What kind of negative feedback occurs within the H-AP-G axis in male reproduction system?
Testosterone inhibits GnRH and LH secretion, inhibin inhibits FSH secretion
LH stimulates Leydig cells to synthesize testosterone by increasing the activity of ________.
cholesterol desmolase
LH action on the testes parallels what other endocrine pathway?
ACTH in the adrenal cortex, both pathways stimulate the first step in steroidogenic pathways
Why do Leydig cells synthesize testosterone specifically?
lacks 21beta and 11beta hydroxylase, thereby preventing mineralocorticoid and gluococorticoid synth
What enzyme do Leydig cells possess that specifically helps in the synth of testosterone, and what are the reactants/products?
17beta hydroxysteroid dehydrogenase, adrostenedione to testosterone
Why do obese patients tend to have less testosterone?
aromatase levels are increased, converting testosterone to estradiol
Since only 2% of testosterone is bioavailable, where is all the rest of the testosterone?
50% bound to albumin, 44% bound to SexHormoneBindingGlobulin (Sertoli cells), 4% bound to other plasma proteins
What are the actions mediated by testosterone?
differentiation of Wolffian duct structures, increased muscle mass, pubertal growth spurt, deepening ov voice, epiphyseal closure, spermatogenesis, libido, negative feedback on H-P, penile growth
Which enzyme catalyzes the conversion of testosterone to DHT?
What are the actions mediated by DHT?
differentiation of penis, scrotum, and prostate, mae hair distribution, sebaceous gland growth, prostatic growth
What causes the peak in testosterone in the fetal stage?
beta-HCG (analagous to LH)
What would be the effect of androgen absence in adolescence and in an adult?
adolescent - lack of virilzation and delayed/absent puberty, adult - decreased libido, infertility
What drugs are 5-AR inhibitors, and what is their clinical significance?
finasteride/dutasteride, decreased DHT will reduce prostate size
How long does it take for a spermatagonia to commit to being a spermatazoa?
64 days
What are the 3 components of the blood testes barrier?
TJs bw sertoli cells, capillary endothelial cells, peritubular myoid cells
What occurs during spermiogenesis?
loss of cytoplasm, formation of the acrosome, formation of the flagellum, migration of cytoplasmic organelles
Where are sperm stored?
How long does it take for sperm to move from the head to tail of epididymis?
2 - 12 days
Epididymal sperm have what characteristics?
immotile but fertile
Describe the differences between spermatazoa of the proximal verus caudal epididymis.
proximal - higher amplitude, lower frequency, less forward movement; caudal - more focused
Where does most of the ejaculatory fluid voiume come from?
seminal vesicle
What is the innervation of the seminal vesicle?
sympathetic via the hypogastric nerve
The seminal vesicle is necessary for ___________ of the ejaculate.
What is the primary action of the prostatic secretions?
liquefacation of the semenal coagulum
Describe the prostatic secretions.
rich in citrate, calcium, enzymes (PSA), and are acidic
Define oligospermia and azospermia.
oligospermia - having less than 15 or 20 million sperm, azospermia - having no sperm
What are the 2 types of obstructive infertility, and what could be their cause?
normal volume - obstructed at level of vas deferens (vasectomy), low volume - obstructed at level of urethra or ejaculatory duct
In isolated spermatogenic failure, what would you expect to see in terms of FSH, LH, and testosterone levels?
elevated FSH, normal LH, normal testosterone
In testicular failure, what would you expect to see in terms of FSH, LH, and testosterone levels?
elevated FSH, elevated LH, normal or low testosterone
What is the somatic innervation of the penis?
dorsal nerve of the penis from the pudendal nerve (S2 - S4)
What is the autonomic parasympathetic innervation of the penis?
S2 - S4 --> pelvic plexus --> cavernoseal nerve (dorsal nerve)
What is the sympathetic innervation of the penis?
T10 - L2 --> sympathetic chain --> hypogastric plexus --> pelvic plexus --> cavernosal nerves
What is the principal neurotransmitter mediating penile erection and what is its mechanism?
NO, increases the production of cGMP which relaxes cavernous smooth muscle
What kind of drugs are Viagra, Levitra, and Cialis and how do they work?
PDE-5s, hydrolyze cGMP to GMP and therefore restores cavernosal smooth muscle tone
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