15. Male Reproductive System

Question 1

What are the functions of testes and why is it located external to the body?

Answer 1

1. produce sperm - sperm production requires a lower temp. than body temp., achieved by the location of the testes (external to the body) and the contraction of the dartos muscle
2. secrete hormones

Question 2

What is the scrotum?

Answer 2

single pouch of skin, supporting structure for testes, separated into lateral portions by the raphe

Question 3

What is the raphe?

Answer 3

seam, a continuous ridge of tissue that extends from the anus, through the midline of the scrotum and upwards through the posterier midline aspect of the penis

Question 4

What is the scrotal septum?

Answer 4

divides scrotum into 2 sacs, each containing a single testis. Made of dartos muscle

Question 5

What is dartos muscle?

Answer 5

layer of smooth muscle fibers. Normal sperm production requires a lower temp. (2-3o C lower than body temp.). Achieved by dartos muscle expanding (if warm) or contracting (if cold, to bring it closer to the body’s heat)

Question 6

What is the structure of the testes?

Answer 6

tunica vaginalis + tunica albuginea

Question 7

What is the tunica vaginalis?

Answer 7

serous membrane, partially covers testes. Remnant that would have been part of the vagina if they had been a girl

Question 8

What is the tunica albuginea?

Answer 8

internal to tunica vaginalis, white fibrous capsule composed of dense irregular CT. Extends inward from septa that divide each testis into 200-300 lobules (internal compartments)

Question 9

What does each lobule of the testis contain?

Answer 9

1. seminiferous tubule (1-3 per lobule) that contains spermatogenic cells and Sertoli (nurse) cells
2. Leydig (interstitial) cells

Question 10

What is the seminiferous tubule?

Answer 10

tightly coiled tubules where sperm are produced

Question 11

What are spermatogenic cells?

Answer 11

sperm-forming cells

Question 12

What are Sertoli (nurse) cells?

Answer 12

1. found in epithelium, large, irregularly shaped with large cytoplasmic arms
2. tight junctions join neighboring Sertoli cells to form the blood-testis barrier - substances must first pass through Sertoli cells before reaching developing sperm. This prevents an immune response against the spermatogenic cell’s surface antigens, which are recognized as “foreign”
3. support spermatogenesis by providing nourishment to spermatocytes, spermatids, and sperm, and pick off bacteria?
4. phagocytize excess spermatid cytoplasm
5. control movements of spermatogenic cells and release of sperm into lumen of seminiferous tubule,
6. provide fluid for sperm transport
7. secrete hormone inhibin (decreases rate of spermatogenesis)
8. regulate effects of testosterone and FSH

Question 13

What are Leydig (interstitial) cells?

Answer 13

clusters located between seminiferous tubules, secrete testosterone

Question 14

What is the route of sperm?

Answer 14

formed in seminiferous tubules pf testis --> 
straight tubules --> 
rete testis --> 
efferent ducts in epididymis --> 
ductus epididymus --> 
head, body, tail of epididymus --> 
ductus vas deferens --> (ejaculation)
ejaculatory duct --> 
urethra --> 
penis

Question 15

What is the rete testis?

Answer 15

1. network of ducts in testis, highway connecting seminiferous tubules to epididymus
2. organized into lobules, separated by CT wall (septum)

Question 16

What is the epididymus?

Answer 16

1. narrow, tightly coiled tube connecting each testicle to its vas deferens. 3 main regions - head, body, and tail
2. storage facility for sperm and propels them during sexual arousal
3. site of sperm maturation - where sperm acquire motility and ability to fertilize ovum

Question 17

What is the pathway of the vas deferens?

Answer 17

1. ascends along posterior border of epididymis…
2. through spermatic cord (ascends out of the scrotum) to lower abdominal wall where it passes…
3. through the inguinal canal to enter the…
4. superficial inguinal ring
5. deep inguinal ring
6. pelvic cavity, it loops over the ureter and passes over the side and down into the posterior surface of the urinary bladder

Question 18

What are the vas deferens ducts?

Answer 18

vas deferens ducts contract to propel sperm from the epididymis (where it was stored) up to the vas deferens. The beginning of emission is typically experienced as a “point of no return”

Question 19

What is the ejaculatory duct?

Answer 19

1. ejaculation of semen through urethra, formed by union of the duct from the seminal vesicle and the ampulla of the vas deferens, and terminates in prostatic urethra
2. is mixed with fluids from the seminal vesicles, the prostate gland, and the bulbourethral (Cowper’s) glands to form the semen/ejaculate

Question 20

What are the 2 functions of fluid precum?

Answer 20

1. neutralizes uric acid of the man’s urethra to prevent capacitation in the male (we want motile sperm in the female, not the male)
2. serves as a natural lubricant

Question 21

What are the 3 accessory sex glands?

Answer 21

1. seminal vesicles
2. prostate gland
3. bulbourethral (Cowper’s) glands

Question 22

What is the secretion of the seminal vesicles?

Answer 22

60% of volume of semen, convoluted pouch-like structures, located posterior to the urinary bladder. Secretion contains:

1. alkaline: helps neutralize acidic environment of male urethra and female reproductive tract that would otherwise inactivate/kill sperm
2. fructose (sugar): used for ATP production by sperm
3. prostaglandins: contribute to sperm motility
4. clotting proteins (not like in blood): help semen coagulate after ejaculation

Question 23

What is the secretion of the prostate gland?

Answer 23

1. 30%, doughnut-shaped gland the size of a golf ball, located inferior to urinary bladder
2. secretes thin, milky alkaline fluid to help sperm live when exposed to acidic lining of vagina and uterus?

Question 24

What is the secretion of the bulbourethral (Cowper’s) glands?

Answer 24

1. <1% fluid secretion, size of a pea, located inferior to prostate
2. secrete alkaline substance that protects sperm by neutralizing acids from urine in urethra
3. also secretes mucus that lubricates penis and lining of urethra, thereby reducing the number of sperm damaged during ejaculation

Question 25

What is the urethra?

Answer 25

shared terminal duct of reproductive and urinary systems, passagemway for both semen and urine

Question 26

What is the penis?

Answer 26

contains the urethra, is a passageway for the ejaculation of semen and the excretion of urine. Consists of a body, glans penis, and root

Question 27

What does the body of the penis contain?

Answer 27

composed of 3 cylindrical masses of tissue, each surrounded by tunica albuginea 1. corpus cavernosum (2) 2. corpus spongiosum (1)

Question 28

What is the corpus cavernosum of the penis?

Answer 28

(cavernosa = hollow), 2 dorsolateral masses

Question 29

What is the corpus spongiosum of the penis?

Answer 29

smaller midventral mass, contains the spongy, flexible urethra, helps protect the delicate urethra, and keeps it open during ejaculation

Question 30

What is the erectile tissue of the penis?

Answer 30

- encloses the corpus cavernosum and corpus spongiosum of the penis - composed of numerous blood sinuses (vascular spaces) lined by endothelial cells and surrounded by smooth muscle and elastic CT - during erections, it will fill with blood

Question 31

What is the glans penis?

Answer 31

the expanded cap of the corpus spongiosum

Question 32

What is the prepuce?

Answer 32

- the foreskin of the penis, covers the head of the uncircumcised penis - removed by circumcision in U.S., because it was thought to be more sanitary, but results in loss of sensitivity. Foreskin can be regained by stretching the skin

Question 33

Which NS innervates the erection and which NS innervates the ejaculation?

Answer 33

erection: parasympathetic NS ejaculation: sympathetic NS

Question 34

What is an erection?

Answer 34

- the enlargement and stiffening of the penis, promoted by the PARASYMPATHETIC NS (more active at night), occurs when the 2 tubular corpus cavernosum (and to a lesser extent the corpus spongiosum) become engorged with venous blood - initiated by the parasympathetic fibers from the sacral portion of the spinal cord, which release and cause local production of nitric oxide --> causes smooth muscle in the walls of arterioles supplying erectile tissue and the erectile tissue to RELAX --> allows blood vessels to dilate, widening of the blood sinuses --> allows large amounts of blood to enter the erectile tissue of the penis

Question 35

What is ejaculation?

Answer 35

-the powerful release of semen from urethra to exterior, promoted by SYMPATHETIC stimulation --> causes the smooth muscle located in the walls of the ducts and accessory sex glands of the reproductive tract to CONTRACT and propel the semen along its course, draining veins dilate and the penis shrinks to flaccidity

Question 36

What are the 2 phases of ejaculation?

Answer 36

1. vas deferens duct: contract to propel sperm from epididymis to vas deferens 2. ejaculatory ducts: contribution from seminal vesicles, prostate gland, and bulbourethral (Cowper's) glands to semen/ejaculate

Question 37

What causes a fractured penis?

Answer 37

occurs when there is abrupt lateral bending of the penis that breaks the stiff tunica albuginea, resulting in a fractured penis

Question 38

What is the gubernaculum?

Answer 38

- ligament that secures testes to scrotum. If not secured, testes will twist within the scrotum and cut off blood circulation - it manifests itself at the beginning of puberty. If this occurs, one of the balls must be removed

Question 39

What is an inguinal hernia?

Answer 39

the inguinal canal is still continuous and flows into the pelvic cavity (continuous with the abdominal cavity). This occurs during weightlifting - if not fixed, it can become twisted and become gangrenous tissue. Do not lift with your gut but with your legs

Question 40

What is cryptorchidism?

Answer 40

undescended testis - if the testes is near body temperature, it has the potential to become a malignant tumor

Question 41

What is spermatogenesis?

Answer 41

when seminiferous tubules of testes produce sperm, takes 65-75 days. Or, the process by which stem cells develop into mature spermatozoa

Question 42

What is the process of deveopment for spermatogonia (2n, stem cells) to sperm?

Answer 42

spermatogonia (2n, stem cells) --> differentiate into primary spermatocytes (2n) -->meiosis (replication before meiosis, crossing over during meiosis) --> 2 secondary spermatocytes (1n) --> meiosis II --> 4 spermatids --> spermiogenesis --> 4 sperm

Question 43

What drives the process of spermatogenesis?

Answer 43

testosterone

Question 44

What is spermiogenesis?

Answer 44

the metamorphosis of spherical spermatids into elongated spermatozoa

Question 45

What is capacitation?

Answer 45

- process of final sperm maturation (activation of sperm tails due to altered mitochondrial organization in the tail) that occurs post-ejaculation in the female reproductive tract where female fluids are acidic - can now fertilize a secondary oocyte - capacitation/activation causes a sperm's tail to beat more vigorously, prepares the sperm cell's plasma membrane to fuse with the oocyte's plasma membrane

Question 46

What is the structure of the spermatozoa?

Answer 46

1. head - acrosome: cap-like structure derived from Golgi apparatus that contains digestive enzymes to help the sperm penetrate a secondary oocyte. Used up - nucleus: during spermiogenesis, the spermatid's chromatin (haploid chromosomes, 23) is remodeled into a more tightly packaged, compact, structure 2. tail - neck: contains centrioles that form the microtubules of the tail - midpiece: hold the mitochondria that provides energy for swimming/locomotion of sperm. Sperm's mitochondria gets destroyed by the egg cell, so we inherit our mitochondria only from our mothers