Male Anatomy and Physiology Flashcards
Male Sex Organs
serve a reproductive function; bring pleasure to self; give pleasure to others; may serve to attract potential sexual partners; sharing of genital sexuality can play a bonding role in relationships
External structures
The penis and the scrotum
Penis
from latin word for tail; organ through which sperm and urine pass;
Three sections of penis
Root, shaft, corpora cavernosa, corpus spongiosum
Root
attaches penis with pelvic cavity
Shaft
contains 3 parallel columns of erectile tissue (corpora cavernosa (2) columns and corpus spongiosum (1) column)
Corpora cavernosa
2 columns along the front surface of shaft
corpus spongiosum
runs beneath the corpora cavernosa, also forms the glans (urethra)
Glans Penis*
enlarged head of the penis; * most sexually sensitive
Corona
rim at the base of the glans
Frenulum
triangular area of skin that attaches the glans to the forskin
Foreskin or Prepuce
sleeve-like covering glans
circumcision
surgical removal of the foreskin
urethra
a tube that transports urine and semen and runs from the bladder
Scrotum*
- pouch of loose skin that holds the two testicles; skin is more heavily pigmented; sparsely covered with hair; divided in the middle by ridge of skin; * testicle temp control= 93 degrees F; two sets of muscles within the scrotal sac– Dartos muscle and cremaster muscle
Dartos muscle
a smooth muscle under the skin that contracts and causes the surface to wrinkle
Cremaster Muscle
fibrous muscle that causes the testicles to elevate
Testes (internal structure)
two major functions: sperm and hormone production; shaped like olives, 1.5” long and 1” in diameter; size and weight decrease as men age; spermatic cord; within each testicle, there are about 1000 seminiferous tubules
spermatic chord
located within the scrotal sac; suspends each testicle and contains a vas deferens
seminiferous tubules *
- production of sperm takes place in these tubes; contain sertoli cells; between these are Leydig cells
sertoli cells *
- manufacture inhibin which signals the hypothalamus to stop the production of GnRH, which in turn, signals the pituitary gland to stop the production of FSH
Leydig cells*
also known as interstitial cells; between the seminiferous tubules; * responsible for producing testosterone
Epididymis* (internal structure)
a tightly coiled tube that is connected to ducts inside the testicle; the head emerges from the top of the testis, descends along the outer surface, and then moves upward to become the vas deferens at its tail; * sperm are stored and mature here
Vas Deferens (internal structure)
the tubes that transport sperm from the epididymis to the ejaculatory ducts
Ejaculatory Ducts (internal structure)
formed by the union of the vas deferens with the duct of the seminal vesicle; they pass through the prostate; they open into the urethra
Seminal Vesicles* (internal structure)
- small glands that lie behind the bladder; responsible for sperm cells; * produces a yellowish viscous fluid rich in fructose; this fluid makes up about 60% of the seminal fluid
Prostate Gland (internal structure)
lies beneath the bladder; the fluid is milky and alkaline; this fluid makes up about 30-35% of the seminal fluid
Cowper’s glands or Bulbourethral glands (internal structure)
positioned below the prostate; secretes a clear alkaline mucous that contributes to the cohesive-jelly like texture of semen; also known as pre-ejaculatory fluid or pre-cum
Urethra (internal structure)
transports urine and semen from the bladder and ejaculatory ducts to the exterior of the body; about 8” in length
Semen
has to provide a nutritive and protective medium for the sperm during their journey through the female reproductive tract, increases the motility of sperm out the male’s urethra and then once it is inside the vagina, helps neutralize some of the acidity in the male’s urethra and in the vagina, prevents the sperm from diffusing out of the semen
Seminal Fluid
semen without the sperm; whitish viscous fluid; produced by contributions from the seminal vesicles, prostate gland, and Cowper’s gland
Sperm
sperm production is called sperm atogenesis; an ongoing process from puberty onward; the avg male will produce roughly 525 billion sperm cells over a lifetime; a teaspoon of ejaculated semen contains 250 million sperm; healthy men produce sperm at a rate of about 60,000 every minute; each individual sperm takes about three months to grow; male is considerred clinically infertile if his sperm concentration falls below 20 million sperm per ml of semen; sperm occupy about 2-5% of the total ejaculate; the normal sperm pH ranges from 7.2-7.8; a sperm’s swimming ability (motility) and shape (morphology) are key factors to examine in a good semen analysis; the shape of sperm is an indirect measure of the quality of genetic information they contain; the number, motility and shape of sperm all generally decline with age
Fertilization
Sperm cells contain receptors on the surface of the sperm head (similar to odor receptors in the nose); researchers believe that sperm can detect the “odor” of the released egg and follow its scent to locate it; the egg is usually covered by a thick layer of cells called the corona radiata; modern in-vitro fertilization techniques can by-pass this selection process and achieve fertilization with much fewer sperm; successful fertilization is now even accomplished with sperm that can’t swim; the sperm must then penetrate the zona pellucida, which is the outer layer of the egg
corona radiata
serves as a blockade to restrict sperm from getting into the egg
cryptorchidism
a medical term referring to the absence from the scrotum of one or both testicles; represents failure of the testis to move, or “descend”, during fetal development from an abdominal position into the scrotum; about 3% of full-term and 30% of pre-mature infant boys are born with at least one undescended testes; the most common birth defect of the male genitalia; most testes descend by the first year of life (the majority within three months) making the true incidence of cryptorchidism around 1% overall
Testosterone
acts on seminiferous tubules to produce sperm; regulates sex drive; is responsible for development of secondary sex characteristics in puberty; influences growth of bones and muscle mass
Hormones That Affect Male Reproductive Processes (1) *
*GnRH –> FSH –> stimulates seminiferous tubules –> sperm
Hormones That Affect Male Reproductive Processes (2) *
GnRH –> * ICSH (interstitial cell stimulating hormone) –> stimulates Leydig cells –> testosterone
