Unit 3: Human Reproduction (Male) Flashcards
Why reproduce?
•to produce offspring—> species survival.
•sexual reproduction: create new gene combinations.
•natural selection: only the best adapted survive.
Advantages of reproduction:
-increases variation.
-promotes survival.
-removes harmful genes from populations.
Disadvantages of reproduction:
-need two parents.
-requires more time/energy.
-fewer offspring produced.
Male and female reproductive systems are characterized by distinct…
•gonads (testes vs. ovaries).
•sex hormones (testosterone vs. estrogen).
•gametes (sperm vs. eggs).
•primary sex characteristics (reproductive organs).
•secondary sex characteristics (features not directly related to reproduction).
Sexual reproduction:
•the male gonads = testes—> produce sperm.
•the female gonads = ovaries—> produce eggs.
•the fusion of a male and female sex cell is called fertilization which produces a zygote.
•the zygote divides many times to form an embryo which continues to grow into a fetus.
Male reproduction (labels to know):
-ureter.
-large intestine.
-seminal vesicle (provides energy to sperm).
-ejaculatory duct.
-prostate gland (secretes buffer to protect sperm).
-Cowper’s gland (secretes mucous to protect sperm).
-epididymis (matures and stores sperm cells).
-testis (produce sperm cells).
-scrotum (regulates temp. of testis).
-foreskin (protects the glans penis).
-glans penis.
-penis (deposits sperm cells in female reproductive tract).
-urethra (carries semen & urine out of the body).
-ductus deferens (carries sperm to urethra).
-urinary bladder.
Male anatomy (testes):
•male gonads (make reproductive cells).
•produce sperm and testosterone (androgen).
•sperm production: begins at 13 and continues throughout life.
Male anatomy (scrotum):
•tissue sac.
•sperm production occurs at 3 degrees lower than body temp.
•close to body when cold, away when hot.
Each testes contains:
- Seminiferous tubules:
•coiled tube within testis (250m).
•sperm cells.
•spermatogenesis: making sperm.
-300-500 million/day (both).
Sertoli cells:
-found within tubules.
-supply nutrients to developing sperm cells.
Interstitial cells:
-found between tubules.
-produce testosterone.
The outer most cells in a testes cut in half:
-spermatogonium (2n).
-are the most basic (like elementary school sperm cells).
-least mature.
The more inner/ the closer you get to the middle cells in a testes cut in half:
-spermatids (n).
-are more mature (like high school cells).
1 kindergarten cell—>:
-4 mature sperm cells.
Sperm (sperm cells):
-3 parts:
- Head:
•nucleus containing DNA.
•23 chromosomes.
•acrosome: caps with enzymes that dissolve egg’s coat and allow penetration. - Middle:
•mitochondria: moves tail, energy. - Tail (flagellum):
•motility (movement).
Male accessory organs (epididymis):
-duct.
-comma shaped, on top of testis.
•sperm cells are produced in the testes, but they mature in the epididymis.
•stores immature sperm.
•sperm become fertile and motile as they move through epididymis. (Sperm school).
•takes about 20 days to mature.
Male accessory organs (ductus (vas) deferens):
•connected to epididymis.
•storage duct.
•carries sperm to ejaculatory duct.
•vasectomy: ductus deferens is cut and cauterized (birth control).
•the tube that connects with the epididymis and transports sperm to the urethra.
•vas deferens connects to the urethra through the ejaculatory duct.
•walls of the seminiferous tubules contract during sexual arousal do expel sperm through the vas deferens.
Male accessory organs (ejaculatory duct):
•controls the semen (sperm + fluids) entering into the urethra.
•carries sperm to the penis.
Penis:
-anatomy:
•shaft with tip (glans).
•foreskin surrounds tip.
•circumcision: removal of foreskin.
-function:
•to deliver sperm into female.
-erection:
•erectile tissue fills with blood; veins compressed.
Urethra:
•shared tube in males for both urine and semen (but never at the same time).
•sphincter at the base of bladder is closed by erection so urine can’t enter during an erection.
Ejaculation:
-urinary system shut off:
•bladder sphincter tightens.
•cannot have both semen and urine in the urethra at the same time.
-send off:
•sympathetic, parasympathetic and sensory nervous system cause penis contraction.
-semen:
•sperm and gland secretions.
•3-4 mL of fluid + 500 million sperm per ejaculation.
•basic pH of 7.2-7.4.
•sperm live for 24-72 hours in semen.
As the sperm move through the ductus (vas) deferens they are:
-mixed with fluid from a series of glands.
The glands (seminal vesicles (paired)):
•fructose: provides sperm energy.
•prostaglandins:
-cause reverse peristalsis in female.
-helps sperm get to egg.
The glands (prostate gland (single)):
•size of a walnut, located in front of rectum, surrounds urethra.
•provides an alkaline buffer to acidic vagina (pH of 3.5-4), activates sperm.
•prostatitis:
-as men age prostate can enlarge, “strangles” urethra, causes difficulty urinating.
The glands (Cowper’s glands (paired)):
-secrete mucus prior to ejaculation to neutralize semen in urethra from urine.
Seminal fluid- review:
•semen: milky mixture containing sperm and seminal fluid.
•seminal fluid is the part of semen which is secreted by three glands:
1. Prostate gland.
2. Cowper’s gland.
3. Seminal vesicles.
- Prostate gland:
•single large gland surrounding part of the urethra.
•produces a thin, milky, alkaline (basic) fluid that activates the sperm to swim and protects them from the acidic vagina.
- Cowper’s gland:
•aka bulbourethral gland (very small).
•secretes an alkaline fluid prior to ejaculation to neutralize the acidity of the urethra (left from urine) and facilitate sperm movement and lubrication.
- Seminal vesicles:
•two glands that have a duct leading to the vas deferens and contains:
-fructose: sugar for energy for the sperm.
-prostaglandins: hormones that stimulate uterine contractions in the female to help the sperm move towards the egg.
Pathway of sperm:
•produced and mature in testes in seminiferous tubules—> epididymis—> vas (ductus) deferens—> (passes seminal vesicle, prostate gland and bulbourethral gland)—> urethra.
Males throughout life (before birth):
•XY:
-on the Y:
•gene: testes determining factor (TDF).
•causes production of androgens (male hormones).
•testes descend:
-develop in abdominal cavity.
-start descending at 3rd month.
-finish descent by 7th month.
Males throughout life (puberty):
-testosterone production causes:
•final development of sex organs.
•spermatogenesis.
•secondary sexual characteristics: deep voice, hair, muscle and bone growth.
•andropause:
-drop in testosterone level (40).
-loss of bone and muscle mass.
-low sperm production.
Hormonal regulation in males:
-hypothalamus (in brain) releases GnRH (gonadotropic releasing hormone) which stimulates anterior pituitary gland (in brain) to release 2 hormones:
1. FSH.
2. LH.
- FSH:
-follicle stimulating hormone.
-promotes production of sperm in seminiferous tubules.
- LH:
-lutenizing hormone.
-aka interstitial cell stimulating hormone (ICSH).
-act on the interstitial cells to produce testosterone.
Alkaline:
-base.
Interstitial:
-in between.
