Reproduction notes
The Male
A. Structure and Function
1. testes - where the sperm and testosterone are produced
2. seminal vesicles - adds
fluids that makes up semen
3. epididymis - sperm are stored here
4. prostate gland - adds
fluids that make up semen
5. urethra - tube that carries urine and semen out of the body
6. Vas deferens - is a tube covered with smooth muscle which contracts to
propel the sperm along.
7. Cowper's gland - secretes fluids that make up semen and lubricates the
urethra
8. penis - the organ of copulation
Be able to identify the parts in
the list above (1 to 8) on the diagram below
B. Pathway of Sperm
-sperm is produced in the seminiferous tubules of the testes and are
stored and mature in a long coiled tube called the epididymis. (the testis and
epididymis together make up a testicle.) From the epididymis the sperm travel
along the vas deferens. The vas deferens is a tube covered with smooth muscle
which contracts to propel the sperm along. Sperm then continue along the vas
deferens and pass by the seminal vesicle and prostate where fluids are added.
Eventually this mixture reaches the urethra, passing by Cowper's gland where
more fluids are added, to be ejaculated out of the penis as semen.
C. Sources and Function of Seminal fluid (Semen)
Seminal fluid or semen is made up of fluids secreted by the prostate,
seminal vesicle and Cowper's gland. It has a basic pH which promotes sperm
survival, it contains fructose to nourish the sperm, and it contains
prostaglandins which cause the uterus to contract which carries sperm to the
upper regions of the female reproductive tract within minutes of ejaculation.
Once out of the body the sperm have a life span of about 48-72 hrs. (ability to
fertilize)
D. Structure of Sperm
Know the names of the labelled areas
and their functions
E. Control of Testosterone Production
-Testosterone is produced in the testes by the interstitial cells. It's
production is controlled by a hormone called luteinizing hormone (L.H.). L.H. is
produced in the anterior pituitary and is secreted when the hypothalamus
secretes "gonadotropic releasing hormone". Secretion of L.H. stimulates the
interstitial cells to produce testosterone which stimulates sperm production.
Follicle stimulating hormone (F.S.H.), another anterior pituitary hormone, acts
on the seminiferous tubules and also stimulates sperm production. As the levels
of testosterone rise, less releasing hormone is secreted by the hypothalamus.
This stops the secretion of L.H., which causes the levels of testosterone to
fall. If the levels remain artificially high, as in steroid use, the whole
system may not restart when the person stops using steroids. The secretion of
the hormones is thought to be related to certain environmental stimuli.
F. Functions of Testosterone
enlarges the male genitalia at puberty, causes the larynx and vocal cord
to enlarge which deepens the voice, stimulates growth of hair in the armpits,
pubic regions and on the body, causes the development of muscles, is responsible
for sex drive, cause development of sweat and oil glands.
2. The Female
A. Structure and Function
1. Ovaries - produce eggs. Follicle produces estrogen and corpus luteum
produces progesterone. Estrogen stimulates the development of: breasts (that's
why some women on the pill experience breast enlargement.), and growth of vagina
and uterus, distribution of body fat, necessary for egg maturation, responsible
for onset of uterine cycle, body hair growth, and enlargement of the pelvic
girdle.
2. Oviducts (Fallopian tubes) - carry the egg from the ovaries to the
uterus
3. Uterus -place where fetus develops
4. Cervix - muscular neck
leading to the uterus
5. Vagina - is the female organ of copulation (receives the penis during
sexual intercourse)
6. Clitoris - similar in structure to the penis. Contains nerve endings
for sexual pleasure
Be able to identify the parts in the
list above (1 to 6) on the diagrams below
B. Ovarian cycle
Eggs develop in the ovaries. They mature one at a time about every 28 days after
the maturation of the previous one. A mature follicle is called a Graafian
follicle.
-in the final stages of growth the follicle moves to the surface of the ovary
and produces a thin blister-like projection. During ovulation this projection
ruptures releasing the egg. The egg is then swept into the fallopian tube and
takes about 3 days to travel down to the uterus. The egg only lives for about 24
hours. Fertilization takes place in the fallopian tube. If the egg is fertilized
it implants in the uterine wall (endometrium) and if the egg is not fertilized
it is shead along with the endometrium during menstruation.
C. The Menstrual cycle
-menstruation is the cyclical process of the shedding of the endometrium and the
associated loss of blood. It begins with the casting off of the endometrium.
D. Hormonal control of the Ovarian and Menstrual cycle
-Controlled by two hormones F.S.H. (follicle stimulating hormone) and L.H. (luteinizing
hormone). These hormones are produced in the anterior pituitary and is secreted
when the hypothalamus secretes "gonadotropic releasing hormone".
i. Ovarian cycle
a. Follicular phase - (days 1-13)
-in the first part of the phase F.S.H. is secreted by the anterior pituitary,
the follicle matures and secretes large amounts of estrogen. As the estrogen
levels rise, less releasing hormone is secreted by the hypothalamus and F.S.H.
secretion decreases.
-in the latter part of the phase -the high levels of estrogen exert positive
feedback on the hypothalamus for a very short time and unusually large amounts
of FSH and LH are secreted. It is this surge of LH that is believed to cause
ovulation
b. ovulation - (day 14)
-the follicle bursts releasing the egg. The resulting scar on the ovary is the
corpus luteum.
c. Luteal phase (days 15-28)
-L.H. is secreted by the anterior pituitary. This causes the development of the
corpus luteum which begins to secrete progesterone and estrogen. As the estrogen
and progesterone levels rise, less releasing hormone is secreted by the
hypothalamus and the secretion of L.H.and FSH is stopped. The corpus luteum
begins to degenerate and menstruation begins.
The diagram below represents an
ovary and the changes that would occurs over 1 complete ovarian cycle. Be able
to identify X and Y and the other parts.
The diagram below
represents the developing follicle over time.
ii. Menstrual cycle
a. Menstruation (days 1 -5)
Low level of hormones (progesterone and estrogen) causes the endometrium (lining
of uterus) to break down and rupture its blood vessels. The lining is released
along with the loss of blood.
b. Proliferation Phase ( days 6-13)
Increased secretion of estrogen by the ovarian follicle causes the endometrium
to become thickened, full of blood vessels (become vascular) and glandular.
c. ovulation - (day 14)
-the follicle bursts releasing the egg
d. Secretory Phase - (days 15-28)
- Increased secretion of progesterone causes the endometrium to double in
thickness. The uterine glands become mature and produce a thick mucoid
secretion. The uterus is now ready to accept the fertilized egg.
E. Hormonal Changes as a Result of Pregnancy
If pregnancy occurs the zygote burrows into the wall of the uterus. A membrane
surrounding the developing zygote produces a hormone called Human Chorionic
Gonadotropin. (HCG) This hormone prevents the corpus luteum from breaking down
and causes it to secrete even greater amounts of progesterone. After the
placenta develops it takes over the secretion of HCG, estrogen and progesterone.
I. Reproduction Quiz Questions
1. What is the function of the following parts of the male reproductive system:
a. testes b. epididymis c. vas deferens d. seminal vesicles e.
prostate f. urethra g. Cowper's gland h. penis
2. What is the function of the following parts of the female reproductive system
a. ovaries b. oviducts (fallopian tubes) c. uterus e. cervix
f. vagina
3. What hormone does the follicle secrete
4. What hormone does the corpus luteum secrete
5. List 4 effects of testosterone on the male
6. 10. What is a mature follicle called
7. List 4 effects of Estrogen on the female
8. How long does the mature egg live
9. How long do sperm live
10. What is the definition of the Menstrual cycle
11. Where does fertilization take place
12. What is ovulation
13. What time during the ovarian cycle does ovulation take place
14. List 2 characteristic of the proliferation phase of the menstrual cycle
15. List 2 characteristic of the secretory phase of the menstrual cycle
16. List 2 characteristic of the follicular phase of the ovarian cycle
17. List 2 characteristic of the luteal phase of the ovarian cycle
18. List 2 functions of Human Chorionic Gonadotropin (HCG)
19. List the function of the following part of a mature sperm
a. head b. acrosome cap c. nucleus d. midpiece
e. tail
II. Reproduction Written Questions
1. Describe four changes that occur in the human male at puberty as a result of
increased secretion of testosterone
2. Describe the results of the following on the reproductive system:
a. A failure of the corpus luteum to degenerate 10 days after ovulation
b. A lack of FSH production during the first 15 days of the menstrual cycle
3. Explain how the menstrual cycle is controlled by hormones from the ovaries,
hypothalamus, and pituitary gland.
4. Explain how the ovarian cycle is controlled by hormones from the ovaries,
hypothalamus, and pituitary gland.
5. Explain how the secretion of testosterone is controlled by hormones from the
testes, hypothalamus, and pituitary gland.
6. Describe any two hormonal changes in a female that occur as a result of
implantation of the embryo. (pregnancy)
