Male Reproductive System - Lecture

Question 1

What are the 3 structures that the kidney develops from? What are the structures that the reproductive system derives from?

Answer 1

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

Question 2

Describe the descent of the testes

Answer 2

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

Question 3

Describe the layers of the inguinal canal in order from deepest to most superficial

Answer 3

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

Question 4

What is in the spermatic cord?

Answer 4

vas deferens, testicular artery, pampiniform plexus, genitofemoral nerve, lymphatic vessels

Question 5

What happens to the mesonephric and paramesonephric duct during male development?

Answer 5

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

Question 6

What is the genital ridge? What happens to it during development?

Answer 6

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

Question 7

What is the fate of the genital tubercle and urogenital sinus?

Answer 7

genital tubercle - forms the penis
- labioscrotal folds fuse in midline to enfold urethra and scrotum

urogenital sinus - forms the urethra

Question 8

Describe the descent of the testes. What muscles descend with them?

Answer 8

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

Question 9

What is the inguinal canal for?

Answer 9

inguinal canal is a passageway through the muscles and CT of the inguinal area to allow spermadic cord to go through

Question 10

Describe the difference between the direct and indirect inguinal hernia

Answer 10

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

Question 11

In the scrotal wall, label the nerves that innervate the skin, dartos muscle, and cremaster muscle (internal oblique.

Answer 11

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

Question 12

What are the roles of each of the following: tunica albuginea, straight tubule, rete testis, efferent ductules

Answer 12

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

Question 13

Describe the steps in spermatogenesis.

Answer 13

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

Question 14

What’s the difference between spermatogenesis and spermeogenesis? What happens in spermeogenesis?

Answer 14

Spermatogenesis - 2n to n
Spermeogenesis - change in spermatid appearance

1. Acrosome formation from Golgi apparatus - cap of sperm, accumulates carbohydrates and hydrolytic enzymes to get through protein shell of egg
2. Centrioles migrate to other end and form flagellum - elongates with nine course fibrils in the middle
3. Mitochondria form the mid piece - form condensed, helical manner around first part of flagellum
4. excess cytoplasm is phagocystized by the Sertoli cell the spermatozoa is located in

Question 15

Describe the role of the epididymus

Answer 15

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

Question 16

What is the role of the vas deferens? What E is it part of?

Answer 16

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

Question 17

Describe the role of the seminal vesicles. What do the produce? What E are they part of?

Answer 17

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

Question 18

Describe the prostate. What does it secrete?

Answer 18

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

Question 19

Describe the bulbourethral gland. What is its function?

Answer 19

secretes thick mucous that neutralizes/flushes residual urine and lubricates the penis

Question 20

Describe the contents of semen

Answer 20

2-5 mL with 20-200 million spermatozoa per mL

• fructose/citric acid
• clotting enzymes
• liquefying enzymes
• zinc
• prostaglandins
• seminalplasmin
• bicarbonate ions

Question 21

Describe the crus of the penis. What does it attach to, and what does it become?

Answer 21

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

Question 22

Describe the corpus spongiosum. What does it originate/end as, and what does it contain?

Answer 22

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

Question 23

Describe what happens after the hypothalamus secretes GNRH

Answer 23

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

Question 24

Describe GNRH. What has a negative effect on its release? What kind of receptor does it activate?

Answer 24

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

Question 25

Describe interstitial cell stimulating hormone. What kind of receptor does it activate and where is the receptor located?

Answer 25

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

Question 26

What is DHT?

Answer 26

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

Question 27

What is the role of testosterone in sertoli cells?

Answer 27

• 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

Question 28

Describe FSH. What kind of receptor does it bind to and where is the receptor located?

Answer 28

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

Question 29

What are the role of the Sertoli cells?

Answer 29

• 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

Question 30

All three E’s have a common sensory pathway. What is it?

Answer 30

general somatic afferent neurons

dorsal nerve of the penis - prudential nerve - erection center of the sacral spinal cord

Question 31

Describe the motor pathway of erection. What system does it use, and what does it release?

Answer 31

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

Question 32

What are the motor pathways for emission? What kind of pathway is it?

Answer 32

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

Question 33

Describe the parasympathetic motor pathway for ejaculation

Answer 33

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

Question 34

Describe the sympathetic efferent pathway of ejaculation

Answer 34

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

Question 35

Describe the voluntary motor pathway for ejaculation

Answer 35

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