Male Reproductive System II Flashcards
What gonadotropins regulate gametogenesis and gonadal steroidogenesis?
Follicle stimulating hormone
Luteinizing hormone
What will happen as a result of continuous exposure to GnRH?
Suppression of gonadotrope secretory activity
Functional Castration
Describe the HPG axis during fetal development
Established during the firs trimester
Activity peaks mid-gestation and declines towards birth due to negative feedback of placental estrogens
Describe the HPG axis during the neonatal period
HPG axis becomes active again
Gonadotropin levels are elevated then decline as CNS gradually exerts an inhibitory effect on the HPG
Describe the HPG axis during childhood
Comes under the control of CNS neurons that exert a strong inhibitory effect
HPA axis remains relatively quiescent during childhood
Describe the HPG axis during the lat prepubertal period?
Gradual disinhibition
First detectable change in goandotropin production is a sleep-associated surge in LG release
Describe the HPG axis during puberty?
HPG becomes increasingly active
Adult patter of HPG activity is established
What are the major events associated with puberty?
Establishment of HPG activity
Maturation of reproductive system and development of secondary sexual characteristics
Pubertal growth spurt
Gametes capable of fertilization
What is the feedback effect of testosterone?
Testosterone inhibits the hypothalamic pulse generator
What is the feedback effect of Inhibin?
Secreted by sertoli cells
Inhibits FSH release
No effect on LH
What are the helicine arteries?
Supply the cavernous spaces in the penis
In a flaccid state, these vessels are constricted
What does the rigidity of an erection depend on?
Increae in flow of arterial blood into the cavernous
Decreased venous efflux resulting from compression of the subtunical venous plexus
What is the role of efferent parasympathetic fibers in the erectile response?
Release NO and vasoactive intestinal peptide
These releax the helicine arteries and smooth muscle fibers
What is emission and its control mechanism?
Movement of semen into the proximal part of the urethra
Controlled by sympathetic signals via NE
What is the ejaculatory response?
Filling the urethra elicits sensory signals via pudendal nerve
Efferent signals trigger rhythmic contraction of the striated musculature of the perineum, especially the bulbocavernosus
What are the clinical manifestations of testicular dysfunctions?
Infertility
Decreased Libido
Poor development of secondary sexual characteristics
What is gynecomastia?
Benign enlargement of the male breast caused by the proliferation of glandular tissue
Results from exposure to excessive amounts of estrogen, decreased testosterone production
What is primary hypogonadism?
Primary testicular failure
E.g. Klinefelter syndrome
What is Klinefelter syndrome?
Most common type of hypogonadism in males
Most common karyotype is XXY
What are the clinical symptoms of Klinefelter syndrome?
Seminiferous tubules are fibrotic and hylanized
germ cells are not present
Infertility
Leydig function is variable
Signs of androgen deficiency
Gynecomastia
What are the lab findings in Klinefelter syndrome?
Elevated FSH and LH
Testosterone low to normal
Elevated Estradiol
What is Orchitis?
Inflammation of the testes, usually secondary to mumps
Seminiferous tubule destruction
Leydig cells unaffected
What is Kallmann syndrome?
Isolated gonadotropin deficiency caused by deficient production of GnRH
Second most common reproductive disorder in males
Often associated with defective sense of smell
