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.