Download Unit – P Reproduction - Mr. Schmitt

Unit P - 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.
(see video)
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.
2.
3.
4.
5.
Formed in the seminiferous tubules of the testes
Mature and stored in the epididymus
Stored in the Vas Deferens
Enters the urethra just prior to ejaculation
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 (Leutenizing Hormone)
-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)
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 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.
Oxytocin Positive Feedback Loops
Oxytocin causes contractions, which cause oxytocin to be
released, which causes contractions, which causes oxytocin to be
released etc until birth
Oxytocin Positive Feedback Loops
Suckling causes milk to be
released, which causes
oxytocin to be released,
which causes milk to be
released, which causes
oxytocin to be released
etc until baby stops
suckling.