Male Reproductive System - Lecture Flashcards
What are the 3 structures that the kidney develops from? What are the structures that the reproductive system derives from?
pronephros, mesonephros, and metanephros
- metanephros - second kidney
Reproductive development - pronephros and mesonephros
- pronephros is not functional in human
- mesonephros - first functioning kidney, forms genital ridge
- further develops into epididymis, vas deferens, and prostatic region of urethra
Describe the descent of the testes
posterior to peritoneum
attached to abdominal cavity by upper/lower gubernaculum (mesenchymal tissue)
- upper degenerates
- lower shortens, pulls testes + abdominal wall through inguinal canal to the scrotum
Describe the layers of the inguinal canal in order from deepest to most superficial
Deep ring - internal opening lateral to inferior epigastric vessels
peritoneum
Extraperitoneal fascia
Transversalis fascia
Arching fascia of transverse abdominis
Arching muscle and fascia of internal ab oblique
Arching fascia/floor fascia of external ab oblique
Superficial ring
What is in the spermatic cord?
vas deferens, testicular artery, pampiniform plexus, genitofemoral nerve, lymphatic vessels
What happens to the mesonephric and paramesonephric duct during male development?
mesonephric duct - 1st embryonic kidney, becomes associated with the mesonephros
mesonephros - develops as secondary and transient kidney, forms efferent ductules at week 4
paramesonephric duct - degenerates due to anti-Mullerian hormone - not present in male
What is the genital ridge? What happens to it during development?
genital ridge - mass of mesoderm that eventually becomes testes
- primordial germ cells migrate from yolk sac
- epithelial cells of genital ridge become Sertoli cells
- seminiferous tubules form in the gonadal ridge to join mesonephric duct
What is the fate of the genital tubercle and urogenital sinus?
genital tubercle - forms the penis
- labioscrotal folds fuse in midline to enfold urethra and scrotum
urogenital sinus - forms the urethra
Describe the descent of the testes. What muscles descend with them?
lower gubernaculum shortens and pulls the testes down
in order from inner to outer:
- tunica vaginalis - made peritoneum
- internal spermatic fascia - transversalis - CT ONLY
- internal oblique muscle - cremaster muscle
- external spermatic fascia external oblique muscle
also has a layer of dartos muscle with superficial fascia, then skin
What is the inguinal canal for?
inguinal canal is a passageway through the muscles and CT of the inguinal area to allow spermadic cord to go through
Describe the difference between the direct and indirect inguinal hernia
hernia - bulging of intestinal loop into inguinal canal
direct - straight through, medial to epigastric vessels
indirect - lateral to epigastric vessels - enters via deep inguinal ring
In the scrotal wall, label the nerves that innervate the skin, dartos muscle, and cremaster muscle (internal oblique.
Skin - sensory innervation
- anterior - genitofemoral nerve
- posterior - superficial perineal nerve
Dartos muscle - smooth muscle
- sympathetic postganglionic fibers from L1/2 that travel with the genitofemoral nerve
Cremaster muscle - internal oblique
- genitofemoral nerve - general somatic efferent neurons
What are the roles of each of the following: tunica albuginea, straight tubule, rete testis, efferent ductules
tunica albuginea - collagen fibers that cover the testis and separate the seminiferous tubules
straight tubule - where seminiferous tubules join, connect to rete testis
rete testis - where straight tubules become interconnected for the efferent ductules
efferent ductules - connect the rete testis to the epididymis
Describe the steps in spermatogenesis.
Spermatogonium (type B, 2N) enter meiotic division
MEIOSIS I
- prophase I: primary spermatocytes replicate sister chromatids pair with homologous partner - 2(2N)
- this is when crossing over can occur
-metaphase I: secondary spermatocytes - chromosomes separate into maternal and paternal sets
- replicated sister chromatids remain attached - 2(N)
- continues through cytokinesis
MEIOSIS II - contains NO replication of chromatic material
- go through (MAT)II and cytokinesis II to form spermatids - N
What’s the difference between spermatogenesis and spermeogenesis? What happens in spermeogenesis?
Spermatogenesis - 2n to n
Spermeogenesis - change in spermatid appearance
- Acrosome formation from Golgi apparatus - cap of sperm, accumulates carbohydrates and hydrolytic enzymes to get through protein shell of egg
- Centrioles migrate to other end and form flagellum - elongates with nine course fibrils in the middle
- Mitochondria form the mid piece - form condensed, helical manner around first part of flagellum
- excess cytoplasm is phagocystized by the Sertoli cell the spermatozoa is located in
Describe the role of the epididymus
single, highly coiled tubule on posterior surface of testes
- site of STORAGE and MATURATION of spermatozoa
- psudostartifles columnar with microvilli
maturation of spermatozoa:
- more cytoplasm reduction
- enzyme maturation in acrosome
- ability to bind rona pelludica (protein coat around egg)
- flagella beating
What is the role of the vas deferens? What E is it part of?
major male duct, major structure of spermatic cord
- lined with pseudo stratified columnar with microvilli
- three layers of smooth muscles: inner circular, middle longitudinal, outer circular
- controlled by sympathetic nervous system
part of EMISSION - undergoes peristalsis to propel sperm from tail of epididymus to urethra
post to bladder, VD dilates to form ampulla - joins the duct of seminal vesicles to form EJACULATORY DUCT that empties into prostatic urethra
Describe the role of the seminal vesicles. What do the produce? What E are they part of?
secrete fluid during EMISSION that forms majority of the volume in semen
thick, mucous secretion incudes:
- bicarbonate to neutralize
- fructose/citrate
- prostaglandins
- sperm motility enhancers
- antioxidants/antibodies
- fibrinogen, vesiculase (clotting agents)
- fibrinolysin - liquefying agents
Describe the prostate. What does it secrete?
surrounds the prostatic urethra - last structure of mesonephric duct
secretes:
- zinc: stabilizes spermatozoan plasma membrane and chromatin
- clotting enzymes
- seiminalplasmin - antibiotic
- spermine - stabilizes helical nature of DNA
- prostatic specific antigen - decreases viscosity of semen – high PSA = cancer
- fertilization promotion protein - activates incapacitated spermatozoa, inhibits capacitated spermatozoa
Describe the bulbourethral gland. What is its function?
secretes thick mucous that neutralizes/flushes residual urine and lubricates the penis
Describe the contents of semen
2-5 mL with 20-200 million spermatozoa per mL
- fructose/citric acid
- clotting enzymes
- liquefying enzymes
- zinc
- prostaglandins
- seminalplasmin
- bicarbonate ions
Describe the crus of the penis. What does it attach to, and what does it become?
attached to the ischial and inferiors pubic ramus - attached to bone = crus
gives rise to the corpora cavernous when not attached - dorsal surface of the shaft of the penis
- two erectile bodies that contain the major erectile tissue of the penis
covered and compressed by the ISCHIOCAVERNOSUS MUSCLE
- innervated by deep perineal nerve
Describe the corpus spongiosum. What does it originate/end as, and what does it contain?
originate - bulb
- covered/compressed by the bulbospongiosum muscle
- innervated by branches of pedestal nerve
end - glans penis: covers tip of corpora cavernosa
- covered by prepuce
contains the spongy/penile urethra
Describe what happens after the hypothalamus secretes GNRH
GNRH reaches the anterior pituitary (adenohypophesis) and causes it to release luteinizing hormone (LH/interstitial cell stimulating hormone) and follicle stimulating hormone (FSH)
LH: goes to the interstitial cells in the testes and stimulates TESTOSTERONE synthesis
- negative feedback on hypothalamus
FSH: goes to Sertoli cells of seminiferous tubules and increases spermiogenesis and release:
- androgen binding hormone - increases localized testosterone
- inhibin - neg feedback effect on pituitary FSH secretion
Describe GNRH. What has a negative effect on its release? What kind of receptor does it activate?
short polypeptide hormone synthesized in the arcuate nucleus of the hypothalamus
binds to G coupled protein receptor in gonadotrophs of adenohypophysis
- phospholipase C pathway: calmodulin + Ca act as second messengers,
- DAG and Ca activate protein kinase C - activates proteins for synthesis, activation and release of LH and FSH
negative effect - sex steroids, inflammation, stress, drugs metabolism
Describe interstitial cell stimulating hormone. What kind of receptor does it activate and where is the receptor located?
glycoprotein hormone released from the adenyhypophysis
binds to G protein coupled receptors in interstitial cells
- activates adenylate cyclase and increases cAMP levels
cAMP activates PKA - causes cholesterol to go into the mitochondria
- de-esterification of cholesterol
- activation of cholesterol transporting proteins
- activation of steroidgenic protein and enzyme gene expression
mitochondrial enzyme P450cc located in inner membrane converts cholesterol into pregnenolone
pregnenolone transported from mitochondria to smooth ER where it gets converted to androstenedione then testosterone
What is DHT?
DHT - 2,4-dihydrotestosterone - potent agonist of androgen receptors
- important for male physique and male patterned baldness
synthesized by 5-a-reductase in many target tissue cells - male reproductive glands, skin, brain, liver, hair follicles
What is the role of testosterone in sertoli cells?
- maintains blood-testis barrier
- maintain adhesions between Sertoli/spermatids
- spermiogenesis - maturation of late spermatids/spermatozoa
- release of spermatozoa into fluid of seminiferous tubules
some testosterone gets converted into estrogen via the enzyme aromatase
Describe FSH. What kind of receptor does it bind to and where is the receptor located?
follicle-stimulating hormone - binds to G coupled protein receptor of Sertoli cell
- activation of adenylate cyclase pathway
- cAMP activates protein kinase A to increase intracellular Ca
leads to synthesis of proteins that activate androgen binding hormone, inhibits, and aromatase
What are the role of the Sertoli cells?
- maintain the blood-testis barrier
- renewal of stem cells (spermatogonia)
- supple nutrients and growth factors
- secretes substances that initiate meiosis
- secrete supporting testicular fluid
- secrete androgen-binding protein
- secrete inhibin
- phaocytose residual cellular debris
All three E’s have a common sensory pathway. What is it?
general somatic afferent neurons
dorsal nerve of the penis - prudential nerve - erection center of the sacral spinal cord
Describe the motor pathway of erection. What system does it use, and what does it release?
parasympathetic nervous system
pelvic splanchnic nerves (preganglionic) - inferior hypogastric plexus - cavernous nerve (postganglionic) - synapses on the branches of the internal pedestal artery
releases ACh and NO
- ACh releases more NO
- NO - activates guanylate cyclase G coupled protein
- cGMP activated protein kinase G to cause smooth muscle relaxation on penile arterioles
What are the motor pathways for emission? What kind of pathway is it?
sympathetic nervous system
LUMBAR SPLANCHNIC NERVE
- formed from pregang neurons from T12-L2 and enter…
- SUPERIOR HYPOGASTRIC PLEXUS to form the HYPOGASTRIC NERVES that descend to…
- INFERIOR HYPOGASTRIC PLEXUS where there are postgang neurons
- sympathetic post ganglionic neurons synapse with smooth muscle of vas deferens/ejaculatory ducts, secretory cells of the seminal vesicles, prostate and bulbourethral glands to release NE
SACRAL SPLANCHNIC NERVE
- starts as pregang neurons from T12-L2 that travel down the sympathetic paravertebral chain ganglia
- SACRAL SPLANCHNIC NERVES are formed when the neurons exit the sympathetic paravertebral chain ganglia
- enter the INFERIOR HYPOGASTRIC PLEXUS where they synapse with the post ganglionic neurons
- synapse with the same places as lumbar splanchnic nerves
Describe the parasympathetic motor pathway for ejaculation
similar to erection
preganglionic nerves - pelvic splanchnic nerves enter the inferior hypogastric plexus to synapse with post ganglionic
post ganglionic nerves leave the inferior hypogastric as the cavernous nerves
cavernous nerves synapse with smooth muscle of the urethral wall to cause peristaltic contraction of the urethra
Describe the sympathetic efferent pathway of ejaculation
similar to the sacral splanchnic path of emission
preganglonic nerves enter inferior hypogastric plexus where they synapse with post gang neurons
those post gang neurons synapse with the smooth muscle of the internal urethral sphincter
- constriction prevents urine from entering the urethra during ejaculation
Describe the voluntary motor pathway for ejaculation
reflex arc activates lower motor neurons in anterior gray horn of sacral spinal nerve
- components of the pudendal nerve
- NMJ’s at skeletal muscle of the deep pereneii muscle, ischiocavernosus and bulbospongiosus muscles
- ACh released by these lower motor neurons results in rhythmic contractions and ejaculatory movement of spematozoa and seminal fluid through the urethra
