unit – p reproduction · become enlarged and urination becomes quite painful. (surgically fixed)...

REPRODUCTION

Testes (male gonads)

-Produce sperm

-Produce sex hormones

-Found in a sac called the scrotum

-Suspended outside of the body cavity for

temperature reduction

-Testes wall made of fibrous connective

tissue (Divides the testes into lobules

(Chambers)

- Inside chambers are long tubes (70 cm)

called the Seminiferous tubules) .

- This is the actual site for spermatogenesis.

- Interstitial cells secretes androgens

“testosterone”

Spermatogenesis –Sperm Development

Sperms cells are derived from undifferentiated cells called

SPERMATOGONIA (sing. Spermatogonium), which lie just on

the outside wall of a tubule and divide mitotically (dividing into

copies), always producing new spermatogonia.

Some newly formed spermatogonia move away from the outer

wall to increase in size and become primary spermatocytes,

which undergo meiosis, a type of cell division.

Primary spermatocytes, with 46 chromosomes, divide to give 2

secondary spermatocytes, each with 23 chromosomes.

Secondary spermatocytes divide to produce 4 spermatids, also

with 23 chromosomes.

Spermatids then differentiate into sperm (spermatozoa).

Also present in the tubules are the sertoli, which support, nourish

and regulate the spermatogenic cells.

Epididymus

-Stores sperm as they mature

Seminal Vesicle

-Contributes to seminal fluid

Cowper’s Gland

-Pea-sized organs that lie posterior to the

prostate on either side of the urethra.

-Contributes to seminal fluid

Prostate Gland

-A single dough-nut shaped gland that surrounds the upper portion of the urethra just below the bladder.

- Older men can have their prostate

become enlarged and urination

becomes quite painful.

(surgically fixed)

- Helps produce seminal fluid

Urethra -Conducts sperm out

of the body

Ductus Vas Deferens- Conducts

and stores sperm

Penis -Serves as an organ of

copulation

Path of Sperm

1. Formed in the seminiferous tubules of the testes

2. Mature and stored in the epididymus

3. Stored in the Vas Deferens

4. Enters the urethra just prior to ejaculation

5. Accessory glands (prostate, Cowper’s gland, and

seminal vesicle) add secretions to semen.

6. Semen and sperm exit through the penis.

Seminal Fluid

SOURCES: 1. Seminal Vesicle

2. Prostate Gland

3. Cowper’s Gland

FUNCTION: Produce slightly basic pH

1. 7.5 preferred pH of sperm (Basic) to counteract the acidity level of the vagina.

2. Provides fructose for energy for sperm

3. Contains prostaglandins – chemicals which cause the uterus to contract.

4. Aids in the movement of the sperm to the egg.

5. Lubrication

Sperm Parts

Head: 23 chromosomes

Acrosome attached- type of Lysosome

-contains hydrolytic enzymes

-digests in outer layer of egg so sperm can penetrate.

Middle Piece: Contains mitochondria – for energy

Tail: Used for locomotion

Function of Testosterone

1. Essential for development of primary sex

organs.

2. Essential for the development of sperm

-spermatogenic cells take up testosterone

which stimulate their activity.

3. Increased testosterone concentration at

puberty causes maturation of penis and

testes.

4. Secondary Sex Characteristics

-facial hair -larynx expands

(voice changes)

-armpit hair -Increase muscular

strength

-pubic hair -aggression

-oil and sweat -sex drive

glands secrete(=Stinky)

Hormonal Control of Testosterone

-Hypothalamus releases GnRH

(Gonadotropic releasing hormone)

-GnRH causes anterior pituitary to release 2

gonadotropic hormones:

FSH (Follicle stimulating hormone)

-promotes spermatogenesis in the

seminiferous tubules

LH (LeutenizingHormone)

-promotes production of testosterone in

interstitial cells.

NEGATIVE FEEDBACK

Increased testosterone concentration in the blood causes the anterior pituitary to make less LH, therefore less testosterone is produced.

Decreased testosterone concentration in the blood causes the anterior pituitary to make more LH and therefore more testosterone is produced.

Increased concentration of stored sperm causes an

increase in production of inhibin and decreases

production of FSH, therefore production of sperm

decreases.

Decreased concentration of stored sperm causes a

decrease in production of inhibin and more FSH,

therefore more sperm is produced.

Female Reproductive System

Ovaries

-Produce eggs and sex hormones

Uterus (Womb)

-Houses developing fetus

Oviduct

-conducts egg towards the uterus

-also called the fallopian tubes or uterine tube

Fimbriae

- finger-like projections of the oviducts which brush over the

ovaries.

-along with cilia in the oviducts, they cause a current which

sweeps the egg into the oviduct

Cervix

-narrow end of uterus leading to the vagina

-dilates at birth to allow baby to exit

Vagina

-Receives penis during sexual intercourse

and serves as a birth canal

Clitoris

-female sensory organ; homologous to the male penis

-provides sensitivity during intercourse

Labia major and Labia minor

-protective folds of skin which surround and protect the

clitoris and the openings of the vagina and urethra

Functions of Estrogen (Female Sex Hormone)

1. Stimulates growth of uterus and vagina at

puberty

2. Egg maturation

3. Secondary Sex Characteristics:

-armpit hair / pubic hair

-fat distribution beneath skin

-enlarged pelvic girdle (wider hips)

-breast development (requires

progesterone as well)

2007

LH

FSH

estrogen

progesterone

lining of uterus

egg development ovulation = egg release

corpus luteum

0 7 14 21 28days

MENSTRUAL CYCLE

Hypothalamus

Pituitary

Ovaries

Body cells

GnRH

FSH & LH

estrogen

MENSTRUAL CYCLE

Hypothalamus

Pituitary

Ovaries

Body cells

GnRH

FSH & LH

estrogen

Ovarian Cycles

(see video)

Day 1 –13 Follicular Phase

1. Hypothalamus produces a GnRH to stimulate Anterior lobe of

pituitary

2. FSH and LH stimulates ovary for follicle growth from pituitary gland

3. Primary follicle (46 chromosomes) contains primary oocyte

(egg cell) which divides.

(produces female sex hormones)

One oocyte gets most cytoplasm and 23 chromosomes.

(called a secondary oocyte, which is inside the now

secondary follicle)

4. Other oocyte called the polar body disintegrates

5. The secondary follicle grows into a Grafian (vesicular) Follicle.

Day 14 Ovulation

6. Grafian Follicle bursts (ovulation) LH is at its highest and triggers

ovulation

Day 15 –28 Luteal Phase

7. The follicle has lost its oocyte (or

“egg”) and forms into the

Corpus Luteum. (LH causes the

corpus luteum to form.)

-the corpus luteum secretes hormones

-estrogen and progesterone

(see video)

If pregnancy (fertilization) does not occur: Corpus

Luteum breaks down (about 10 days) Cycle will

repeat.

If pregnancy does occur: Corpus luteum remains

for 3 – 6 months and continues to produce

hormones.

Uterine Cycle

Day 1 –5 Menstruation

1. Low levels of sex hormones (Corpus Luteum

has just disintegrated)

2. Endometrium (lining of Uterus) breaks down

3. Cells of the endometrium, blood vessels, and blood are

shedding from the uterus and exit the vagina.

4. A flow of blood (called menses) passes out of the vagina

during a period called menstruation.

Day 6 – 13 Proliferative phase

1. Increase estrogen by the ovarian

follicle causes the endometrium to

rebuild.

2. Endometrium becomes thick and

vascularized

Day 14

Ovulation occurs (release of the egg)

Day 15 –28 Secretory Phase

1. Increase level of progesterone by the corpeus

luteum

2. Endometrium doubles in thickness

3. Glands produce mucous

4. Now prepared to receive embryo

(see video)

If no pregnancy, the corpeus luteum

degenerates, decrease in progesterone production occurs and the endometrium breaks

down. Cycle continues.

Controls of Cycles by Hormones

Hypothalamus secretes GnRH (gonadotropic releasing hormone) and causes the anterior pituitary to secrete FSH and LH

FSH causes follicles to mature. Maturing follicles produce estrogen.

Increase in estrogen concentration

causes the anterior pituitary to stop

producing FSH and LH(negative feedback)

Around day 12, the increased levels of estrogen suddenly cause

positive feedback on the anterior pituitary and stimulate the

release of FSH and large amounts of LH.

This surge of LH triggers ovulation.

LH then triggers the remaining follicle cells to differentiate into the

corpus luteum which secretes progesterone and some estrogen.

Estrogen promotes the thickening of the endometrium

Progesterone stimulates the endometrium to mature and

become secretory.

These changes are to prepare for the possibility of

fertilization, implantation and pregnancy.

At the end of the cycle, if the egg has not been fertilized or

implantation and pregnancy do not occur, the corpus luteum

breaks down and stops releasing estrogen and progesterone.

Without these hormones, the uterine lining (endometrium) breaks

down and menstruation starts.

Implantation

Fertilization (sperm cell enters the oocyte) occurs in the oviduct. The joining of the two cells forms an embryo.

Implantation of the embryo occurs in the uterus.

Embryo embeds itself in the endometrium

several days after fertilization.

Pregnancy has now begun.

Implantation starts the production of the hormone HCG (Human Chorionic Gonadotropin) which prevents the corpus luteum from degenerating.

It is found immediately in blood and a few days later in the urine. Ex. Pregnancy test. (About one week later)

HCG prevents the breakdown of the Corpus Luteum. The

Corpus Luteum produces progesterone that keeps the

endometrium from breaking down.

FSH and LH production is inhibited which stops the egg from

being released.

The placenta begins to develop from embryonic and maternal tissues after implantation.

Placenta

Contains both maternal and fetal tissue

Area where gas and nutrients exchange occurs.

No exchange of blood

Diffusion of gases and wastes and nutrients occur

over the cell layers

Placenta produces HCG, progesterone (prevents breakdown

of the endometrium) and estrogen (keeps new egg from

developing)

Oxytocin and Positive Feedback – Giving Birth

Oxytocin used to induce birth. Oxytocin causes uterine contractions,

which in turn stimulate the release of more oxytocin. Positive

feedback.

Oxytocin also causes mammary glands to release milk. Lobules

containing milk contract forcing milk into ducts which lead to the

nipple.