PHYSIOLOGY

1. 1
Human Physiology
KAAF University
The reproductive system
Dr Joseph Somuah Akuamoah
Senior lecturer

2. 2
The Reproductive system
• Male reproductive and hormonal
functions
• Female physiology before pregnancy
and female hormones

3. 3
Male reproductive and hormonal functions
• The reproductive functions of the male are
divided into 3 major divisions:-
1. Spermatogenesis
2. Performance of the male sexual act
3. Regulation of male reproductive functions by the
various hormones.

4. 4
1. Spermatogenesis
• Spermatogenesis occurs in the seminiferous
tubules during active sexual life as the result of
stimulation by anterior pituitary gonadotrophic
hormones; beginning around the age 13 years.
• Large primary spermatocytes undergo meiotic
division to form two secondary spermatocytes.
After a few days, these also divide to form
spermatids that are eventually modified to
become spermatozoa (sperm).
• During this division, the 46 chromosomes (23
pairs of chromosomes) of the spermatocyte are
divided, so 23 chromosomes go to one spermatid
and the other 23 to the second spermatid.

5. 5
Spermatogenesis….
• This also divides the chromosomal genes so that
only one half of the genetic characteristics of the
eventual fetus are provided by the father, whereas
the other half are derived from the oocyte
provided by the mother.
• The spermatids differentiate and elongate into
spermatozoa- composed of a head and a tail.
• The head comprises the condensed nucleus of
the cell. The tail of the sperm, called the flagellum,
provides motility of the sperm.
• Normal sperm move in a fluid medium at a
velocity of 1-4 mm/min

6. 6
Spermatogenesis……
Maturation of sperm
• After the sperm is formed in the seminiferous
tubules, the sperm require several days to pass
through the 6-meter long tubule of the epididymis.
Storage of sperms
• The two testes of the human adult form up to 120
million sperms each day. A small quantity of these
can be stored in the epididymis but most are
stored in the vas deferens.
• They can remain stored, maintaining their fertility
for at least a month. With a high level of sexual
activity and ejaculations, storage may be no
longer than for a few days.

7. 7
Spermatogenesis….
The mature sperm
• The activity of sperm increases markedly with
increasing temperature.
• Although sperm can live for many weeks in the
suppressed state in the testes, life expectancy of
ejaculated sperm in the female genital tract is only
1-2 days.
Semen
• Semen is ejaculated during the male sexual act.
• It is composed of the fluid and sperm from the vas
deferens (10%), seminal vesicles (60%), prostate
gland (30%) and small amounts from the
bulbourethral glands

8. 8
Male sexual act
• The most important source of sensory nerve
signals for initiating the male sexual act is the
glans penis. E.g. Direct stimulation of the genitalia
• Impulses may also enter the spinal cord from
areas adjacent to the penis (scrotum, perineum,
anal area) to aid in stimulating the sexual act.
• Appropriate psychic stimuli like fantasy can
greatly enhance the ability of a person to perform
the sexual act.
• Thinking sexual thoughts or dreaming can initiate
the male act culminating in ejaculation-nocturnal
emissions

9. 9
Stages of the Male sexual act
Penile erection
• This is caused by parasympathetic impulses that pass
from the sacral portion of the spinal cord through the
pelvic nerves to the penis. The stimulation makes the
nerves release nitric oxide.
• Nitric oxide released leads to rapid arterial blood flow
into the erectile tissue of the penis whiles the venous
outflow is partially occluded causing ballooning of the
erectile tissue for the penis to become hard and
elongated.
• The parasympathetic impulses cause the urethral and
bulbourethral glands to secrete mucus which aids in
lubrication during coitus. However the female sexual
organs provide most of the lubrication during coitus.

10. 10
Stages of the Male sexual act
Emission and ejaculation
• When the sexual stimulus becomes extremely
intense, the reflex centers of the spinal cord begin
to emit sympathetic impulses that leave the cord
at T-12 to L-2 to the genitals to initiate emission,
the forerunner of ejaculation.
• The entire period between emission and
ejaculation is called the male orgasm.
• At its termination, the male sexual excitement
disappears almost entirely within 1-2 minutes and
erection ceases, a process called resolution

11. 11
Medical importance
Erectile dysfunction
• This is the inability of the man to develop or maintain
an erection of sufficient rigidity for satisfactory sexual
intercourse
• Can be due to 1. performance nervousness, anxiety,
fear, social pressure; 2. drugs (alcohol, nicotine); 3.
vascular disease (diabetes, hypertension) or 4.
neurological (trauma to the parasympathetic nerves)
Baldness
• This could be hereditary. This is the most common
cause. Or could be due to…..
• Increased levels of testosterone leads to baldness –
a man without a testes cannot be bald.

12. 12
Female hormonal system
Three hormones are important in females
• A hypothalamic releasing hormone-gonadotropin
releasing hormone (GnRH)
• The anterior pituitary sex hormones-follicle
stimulating hormone (FSH) and luteinizing
hormone (LH) both of which are secreted in
response to the release of GnRH from the
hypothalamus
• The ovarian hormones-oestrogen and
progesterone which are secreted by the ovaries in
response to FSH and LH from the anterior
pituitary.

13. 13
Monthly ovarian cycle
• The rates of secretion of the female hormones
and corresponding physical changes in the
ovaries and other sexual organs gives a
rhythmical pattern in reproductive females.
• This rhythmical pattern is called the female
monthly sexual cycle which averages 28 days.
(can be as short as 20 days and long as 45 days)
• Only a single ovum is normally released from the
ovaries each month, so normally only a single
fetus will begin to grow at a time
• The uterine endometrium is prepared in advance
for implantation of the fertilized ovum.
• Ovulation in a 28 day female occurs on day 14

14. 14
Puberty, menarche and menopause
• Puberty means the onset of adult sexual life and
menarche means the beginning of the cycle of
menstruation.
• Puberty is caused by a gradual increase in
gonadotrophic hormone secretion by the pituitary
around age 8 years of life leading to onset of
puberty and menstruation at ages 11 to 16 years.
• At age 40-50 years the sexual cycle becomes
irregular and ovulation often fails to occur.
• Menopause is the period during which the cycle
ceases and the female sex hormone diminish to
almost to none

15. 15
Female sexual act
1. Stimulation
• Thinking sexual thoughts can lead to female
sexual desire, and this aids greatly in the
performance of the female sexual act.
• Desire for sex also changes during the monthly
sexual cycle, reaching a peak near the time of
ovulation, probably due to the high levels of
oestrogen secretion during the preovulatory
period.
• Local sexual stimulation occur around the vulva,
vagina and other perineal regions.
• The clitoris is especially sensitive for initiating
sexual sensations

16. 16
Female sexual act
2. Female erection and lubrication
• Located around the introitus and extending into
the clitoris is erectile tissue (penis) controlled by
the parasympathetic nerves which sends signals
for dilatation of the arteries of the erectile tissue.
• Parasympathetic fibers also cause the Bartholin
glands to secrete mucus inside the introitus for
good lubrication during sexual intercourse
• Dilatation of the arteries causes the introitus to
tighten around the penis which aids the male to
ejaculate fast

17. 17
Female sexual act
3. Female orgasm
• When local sexual stimulation reaches maximum
intensity, and especially when this is supported by
appropriate psychic conditioning signals from the
cerebrum, reflexes are initiated that cause the
female orgasm, also called the female climax.
• Female orgasm is analogous to emission and
ejaculation in the male and may help promote
fertilization of the ovum. (increased perineal
contractions and dilation of the cervical canal for
up to 30 minutes allows easy transport of sperm)
• After orgasm, there is a sense of satisfaction -
resolution

18. 18
Medical importance
1. Fertile period of each sexual cycle
• The ovum remains viable and capable of being
fertilized after it is expelled from the ovary
probably no longer than 24 hours. Therefore
sperm must be available soon after ovulation if
fertilization is to take place
• A few sperm can remain fertile in the female
reproductive tract for up to 5 days. Hence for
fertilization to take place, intercourse must
sometime between 4 and 5 days before
ovulation up to a few hours after ovulation
• The period of female fertility during each month
is short about 4 to 5 days.

19. 19
Medical importance
2. Abnormal conditions that cause female sterility
• About 5-10% of women are infertile.
Occasionally no abnormality can be discovered
in the female genital organs.
• The most common cause of female sterility is
failure to ovulate due to:-
 hyposecretion of gonadotrophic hormones
 Abnormal ovaries that do not allow ovulation
• Simple tests for ovulation include:
 the daily temperature chart;
 urine test during the latter half of the sexual cycle
for a surge in pregnanediol etc.

20. 20
Questions
1. List three secondary sex characteristics of
females.
2. Describe the events and possible consequences
of menopause.
3. A man swam in a cold lake for an hour and then
noticed that his scrotum was shrunken and
wrinkled. His first thought was that he had lost
his testicles. What had really happened?

21. 21
Questions
4.
a.What types of sexual dysfunction might arise in men
taking drugs that inhibit sympathetic nervous activity as
part of their treatment for high blood pressure?
b.Explain the physiologic basis for administering
posterior pituitary extract to induce or facilitate labor
c.Akosua Mensah who is in in her second month of
gestation, has been experiencing severe abdominal
cramping. Her Physician has diagnosed her condition as
an Ectopic pregnancy.
(i)What is an ectopic pregnancy?
(ii) Why must this pregnancy be surgically removed?