REPRODUCTIVE SYSTEM

Presented by:
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Dr. Wishan Das
Public Health Specialist
FUNCTIONS OF THE MALE REPRODUCTIVE SYSTEM
• The reproductive functions of the male can be divided into three major
subdivisions:
1) Spermatogenesis
2) Performance of the male sexual act
3) Regulation of male reproductive functions by various hormones
• Associated functions are related to the effects of male hormones on the
accessory sexual organs, cellular metabolism, growth and other functions of
the body.
FUNCTIONS OF THE FEMALE REPRODUCTIVE SYSTEM
• Female reproductive functions can be divided into two major phases:
1) Preparation of the female body for conception and pregnancy
2) The period of pregnancy itself.
SPERMATOGENESIS
• Spermatogenesis is formation of
the sperm.
• It occurs in the seminiferous
tubules.
• Begins at an average age of 13
years as a result of stimulation
by anterior pituitary gonado trophic hormones.
• The primary immature cells,
spermatogonia present in the
testes arise during the formation
of the embryo as primordial germ
cells.
HORMONAL FACTORS THAT STIMULATE SPERMATOGENESIS
1) Testosterone, secreted by the interstitial
cell of Leydig of the testes is essential for the growth and the division of spermatogonia.
2) Luteinizing hormone stimulates the
Leydig cells to secrete testosterone.
3) Follicle-stimulating hormone helps in
conversion of spermatids to sperm by
stimulating the Sertoli cells.
4) Estrogens, formed from testosterone by
the Sertoli cells when they are stimulated
by FSH, are essential for spermiogenesis.
5) Growth hormone is necessary for controlling the metabolic functions of the testes.
TESTOSTERONE
PRODUCTION
Testosterone, an androgen is formed by the interstitial cells of Leydig lying in the
interstices between the seminiferous tubules of the testes.
CHEMISTRY
All androgens are steroid compounds.
METABOLISM
Much of the testosterone that becomes fixed to the tissues is converted within the
tissue cells to dihydrotestosterone.
DEGRADATION AND EXCRETION
Testosterone not fixed to tissues is rapidly converted, mainly by the liver to
andosterone and dehydroepiandosterone and simultaneously conjugated as
either glucuronides or sulfates.
FUNCTIONS OF TESTOSTERONE
1) Functions of testosterone during fetal development:
Testosterone secreted first by the genital ridge cells and later by the fetal testes
is responsible for the development of the male body characteristics while at the
same time suppressing the formation of female genital organs. It begins to be
elaborated by the 7th week of fetal life.
Effect of Testosterone to cause descent of the testes:
Descent of testes into the scrotum in the last 2-3 weeks of gestation occurs in
response to considerable testosterone secretion.
Testosterone or gonadotropic hormonal administration may help in newborn’s with
undescended testes.
2) Effect of testosterone on development of Adult Primary and secondary Sexual
characteristics
After puberty, increasing amounts of testosterone cause the external genital organs to
enlarge about 8 fold before the age of 20.
The development of secondary characteristics that differentiate a male from a female
also begins at puberty in response to testosterone. They are:
a) Effect on distribution of body hair
b) Baldness
c) Effect on the voice
d) Increased thickness of skin and development of acne
e) Increased protein formation and muscle development
f) Increased bone matrix and calcium retention
g) Increased basal metabolic rate
h) Increased red blood cell production
i) Increase in blood and extracellular fluid volume in relation to body weight.
PHYSIOLOGICAL CHANGES DURING MALE PUBERTY
1) Growth of hair over the face, pubis, upward along linea alba, chest and less often on
the back.
2) Increased thickness of the skin and ruggedness of the subcutaneous tissues.
3) Production of acne because of excessive sebaceous gland secretions.
4) 50% increase in muscle mass on average at puberty because of protein anabolic
function.
5) Bones grow thicker and deposit additional calcium salts so that both the size and the
strength increase.
6) The pelvic outlet narrows, lengthens, assumes a funnel like shape and greatly
increases in strength for load- bearing.
7) Spurt in total body height at puberty.
8) 5-10% increase in basal metabolism because of protein anabolism and general
increase in cell activity.
9) Increase in red blood cell production and blood volume along with increase in
extracellular fluid volume in relation to body weight.
FEMALE OVARIAN HORMONES
Estrogens
Β-estradiol
Estrone
Estriol
PRODUCTION
Significant secretion from the ovaries, minute amounts by the adrenal cortices in the
non-pregnant state.
Tremendous quantities secreted from the placenta during pregnancy.
Progestins
Progesterone
17-α-hydroxyprogesterone
PRODUCTION
From the ovaries, secretion in the later half of the ovarian cycle in the non-pregnant state
while secretion from the placenta after the fourth month of gestestion in pregnancy.
FUNCTIONS OF ESTROGENS AND THE PHYSIOLOGICAL CHANGES AT PUBERTY
Primary function of estrogen is to cause cellular proliferation and growth of the
tissues of the sex organs and other tissues related to reproduction.
1) The female reproductive organs; ovaries, fallopian tubes, uterus and vagina all
increase several times in size with enlargement of external genitalia at puberty.
2) There is marked proliferation of endometrial stroma with development of
endometrial glands in the uterus.
3) There is proliferation of glandular tissues of the mucosal lining of the fallopian
tubes with increase in ciliated epithelial cells and enhancement of ciliary
activity.
4) Initiation of growth and milk producing apparatus of the breasts.
5) Estrogens stimulate bone growth by inhibiting osteoclastic activity.
6) Growth spurt for several years at puberty followed by union of
epiphyses of long bones.
7) Slight increase in total body protein and whole body metabolic rate.
8) Deposition of increased quantities of fat in the subcutaneous tissues.
9) Little effect on hair distribution. Androgens formed from the female
adrenal gland contribute to pubic and axillary hair development.
10) Development of soft and smooth texture of skin with increase in
vascularity and warmth of skin.
11) Causes sodium and water retention by the kidney tubules.
FUNCTIONS OF PROGESTERONE
1) It promote secretory changes in the uterine endometrium, during the later half
of the monthly endometrial cycle, preparing the uterus for implantation of the
fertilized ovum.
2) It decreases the frequency and intensity of uterine contractions, thereby
helping to prevent expulsion of the implanted ovum.
3) It promotes secretion from the mucosal lining of the fallopian tubes which are
necessary for the nutrition of the fertilized dividing ovum.
4) It promotes the development of the breasts.
MONTHLY ENDOMETRIAL CYCLE, OVULATION AND
MENSTRUATION
• The monthly endometrial cycle associated with the monthly cyclical production
of estrogen and progesterone from the ovaries operates through:
1) Proliferative Phase (Estrogen phase) of the endometrial cycle, occurring
before ovulation
a. At the beginning of each monthly cycle, under the influence of estrogens,
secreted in increasing quantities by the ovaries, the stromal and the epithelial
cells of the endometrium proliferate rapidly within 4-7 days.
b. There is increase in the number of stromal cells and progressive growth of the
endometrial glands and new blood vessels in the next week and a half.
c. Endometrium gets 3-5 mm thick by the time of ovulation.
OVULATION
1) During the first stage of the ovarian cycle, estrogen plays a positive feedback effect of
stimulating the pituitary secretion of LH and to a lesser extent FSH.
2) The granulosa cells of the follicles secrete small but increasing quantities of
progesterone a day or so before ovulation stimulating excess LH secretion .
3) The preovulatory LH surge will result in ovulation from the ovary, when the secretion
of LH has increased upto six-eight folds and FSH secretion increases two folds.
4) Ovulation takes place at about the 14th day of the monthly endometrial cycle during
the secretory phase.
2) Secretory phase (progestational phase) of the Endometrial cycle, occurring
after ovulation
• After ovulation , progesterone and estrogen together are secreted in larger
quantities by the corpus luteum which will produce a highly secretory
endometrium that contains large amounts of stored nutrients to provide
appropriate conditions for the implantation of a fertilized ovum.
• Blood supply to the endometrium further increases
• Endometrial changes taking place are:
a) Endometrial glands increase in tortuosity
b) Accumulation of secretory substance in glandular cells
c) Increase in stromal cytoplasm
d) Increased deposition of glycogen and lipid in stromal cells
• Endometrium thickness increases to 5-6 mm
MENSTRUATION
• If the ovum is not fertilized, about two days before the end of the monthly cycle
of 28 days, the corpus luteum in the ovary suddenly involutes resulting in low
levels of secretion of ovarian hormones and so menstruation starts and there is
expulsion of uterine contents.
• After desquamation by menstruation, only a thin layer of endometrial stroma
remains with epithelial cells of the deeper layer of the glands only.
• Within 4-7 days after the start of menstruation, loss of blood ceases because of
re-epithelialization of the endometrium
FEMALE REPRODUCTIVE CYCLES
MENOPAUSE
• It is the period during which the female sexual cycle ceases and the female sex
hormones diminish to almost none.
• At the age of 40 - 50 years, the reproductive cycle becomes irregular and ovulation
often fails to occur after which over a few months to few years , the cycle ceases
altogether.
• The cause of menopause is burning out of ovaries.
• Physiological changes after hormonal loss:
a) Hot flushes
b) Psychic sensation of dyspnea
c) Irritability
d) Fatigue
e) Anxiety
f) Decreased strength and calcification of bones.
PREGNANCY
• Pregnancy or gestation is a sequence of events taking place in the
female starting with the fertilization of the ovum leading to the
development of a full term fetus.
HORMONAL FACTORS IN PREGNANCY
1) Human chorionic Gonadotropin causes persistence of the corpus
luteum and prevents menstruation. It stimulates the testes to
produce testosterone in the male fetus until the time of birth.
2) Estrogen exerts proliferative function on most reproductive and
associated organs of the mother. It also relaxes the pelvic
ligaments.
3) Progesterone decreases contractility of the pregnant uterus,
contributes to development of conceptus, plays important role in
nutrition of early embryo, helps estrogen prepare the mother for
lactation.
4) Human chorionic sommatomammotropin has partial effect on
breast development, causes protein tissue formation, causes
decreased insulin sensitivity and decreased utilization of glucose
with mobilization of fat stores in the mother.
5) Glucocorticoids mobilize mother’s aminoacids to syntheisze fetal
tissues.
6) Aldosterone with estrogen exerts water retention effect.
FUNCTIONS OF THE PLACENTA
1) The placenta allows diffusion of Oxygen, carbon dioxide and nutrients while allowing
excretion of waste products through the placental membrane.
2) The placenta forms large quantities of human chorionic gonadotropin, estrogens,
progesterone and human chorionic sommatomammotropin, which are all essential to a
normal pregnancy.
PHYSIOLOGICAL CHANGES OF PREGNANCY
1) Increased size of various sexual organs.
2) Weight gain
3) Rise in basal metabolism as a hormonal effect and use of extra energy for
muscular activity overcoming extra load.
4) Rise in nutritional needs during pregnancy
5) Blood flow through the placenta and maternal cardiac output increase during
pregnancy up to 30-40% above normal by the 27th week of gestation after
which during the last eight weeks, it falls to only a little above normal.
6) Maternal blood volume increases during pregnancy along with rise in red blood
cells.
7) Maternal respiration increases during pregnancy with rise in minute ventilation.
8) There is slight increase in the rate of urine formation, renal tubules reabsorptive
capacity for sodium, chloride and water is increased and there is renal
vasodilation leading to increase in renal blood flow and glomerular filtration rate.