NOTES: CH 46, part 2 –

Hormonal Control /

Reproduction

Hormones Involved in Reproduction - MALES

● Androgens: produced in Leydig cells in testes

(i.e. TESTOSTERONE)

● GnRH: from hypothalamus; stimulates anterior pituitary to release FSH and LH

● FSH: acts on seminiferous

tubules to increase sperm

production

● LH: stimulates androgen

production

*primary sex characteristics:

-development of internal and external

reproductive organs

-sperm production

*secondary sex characteristics:

-deepening of voice

-distribution of facial & pubic hair

-muscle growth

Hormones Involved in

Reproduction - FEMALES

● MENSTRUAL CYCLE = changes that

occur in uterus

● OVARIAN CYCLE = changes that occur in

ovaries

Menstrual cycle occurs in 3

phases:

1) Menstrual flow phase (3-5 days):

endometrium is being shed from uterus

2) Proliferative phase (1-2 weeks):

regeneration & thickening of

endometrium

Menstrual cycle occurs in 3 phases:

3) Secretory phase (2 weeks):endometrium continues to thicken, becomes more vascularized & develops glands which secrete a glycogen rich fluid which serves as nutritional fluid for the embryo

(IF embryo does NOT implant in uterine lining by the end of this phase, a new menstrual flow phase begins)

Ovarian Cycle:

1) Follicular phase: several follicles in

ovaries begin to grow

2) Ovulatory phase: follicle & adjacent wall

of ovary rupture, releasing the egg

(2° oocyte)(Follicular phase)

Ovarian Cycle:

3) Luteal phase: the remaining follicular

tissue in ovary after ovulation becomes the

CORPUS LUTEUM which is endocrine

tissue that secretes hormones

(Luteal phase)

Menstrual and Ovarian Cycles

are closely related:

● increased amts. of estrogen secreted by growing follicle stimulates endometrium to thicken in preparation for embryo

(PROLIFERATIVE PHASE)

● after ovulation, estrogen & progesterone secreted by the CORPUS LUTEUMstimulate continued development & maintenance of the endometrium

(SECRETORY PHASE)

Menstrual and Ovarian Cycles

are closely related:

● decreased concentration of estrogen &

progest. due to disintegration of the C.L.

reduces blood flow to the endometrium; the

endometrium breaks down & passes out of

the uterus

● IF embryo is present, it secretes HCG which

maintains estrogen & progest. secretion by

the C.L. so the endometrium is maintained

MENOPAUSE

Menopause: cessation of

ovulation and menstruation

-between ages of 46 and 54

-ovaries lose their

responsiveness to FSH/LH

-decline in production of

estrogens

FERTILIZATION & IMPLANTATION

● fertilization occurs in the

OVIDUCT

● female repro. tract produces

secretions which capacitate

sperm cells

● a capacitated sperm cell

reaches the egg and must

penetrate the ZONA

PELLUCIDA

FERTILIZATION & IMPLANTATION

● when sperm cell binds to

receptor molecules in zona

pellucida, the

ACROSOME releases its

contents (i.e. digestive

enzymes) so that it can

penetrate the plasma

membrane of the egg

(= “acrosomal reaction”)

FERTILIZATION & IMPLANTATION

● binding of sperm cell to egg triggers

depolarization of egg membrane (functions

as a “fast block” to polyspermy)

(= “cortical reaction”; a series of

changes in outer zone, “cortex,” of the

egg cytoplasm)

FERTILIZATION & IMPLANTATION

● CLEAVAGE (cell division) begins

approx. 24 hours after

conception

● after 3 days, embryo contains

approx. 16 cells (MORULA)

● embryo reaches uterus approx. 7

days after fertilization & contains

approx. 100 cells

(BLASTOCYST)

FERTILIZATION & IMPLANTATION

● implantation occurs within next 5 days

● for the first 2-4 weeks, embryo obtains nutrients directly from endometrium

● in 2nd trimester, fetus secretes its own progesterone to maintain pregnancy

BIRTH● high estrogen levels

during the last weeks of pregnancy trigger formation of oxytocin receptors in uterus

● oxytocin secreted by fetus & posterior pituitary of mother stimulate smooth muscles of uterus to contract

BIRTH

● oxytocin stimulates prostaglandin

secretion by placenta which enhances

muscle contraction of uterus

● decreased levels of progesterone after

birth remove inhibition from anterior

pituitary which allows for prolactin

secretion

BIRTH

● PROLACTIN stimulates milk production

after 2-3 days

● OXYTOCIN controls release of milk from

mammary glands

BIRTH CONTROL:

Methods of Contraception:

1) COITUS INTERRUPTUS: withdrawal of penis before ejaculation

2) RHYTHM METHOD:

requires abstinence

from sexual intercourse

a few days before/after

ovulation

3) MECHANICAL BARRIERS:

-condom (male, female)

-diaphragm

-cervical cap

4) CHEMICAL BARRIERS:

-creams, foams, jellies w/spermicide

-easy to use, but high failure rate

unless used with a condom or

diaphragm

5) ORAL CONTRACEPTIVES:

-“the pill”

-contain synthetic hormones to disrupt the

ovarian cycle and prevent ovulation

-can be taken in pill form, injected, or

implanted

6) INTRAUTERINE DEVICE (IUD):

-small, solid object placed

within the uterus

-prevents implantation

of blastocyst

7) SURGERY:

-in males: VASECTOMY

-in females: TUBAL LIGATION