PHYSIOLOGY OF THE MALE REPRODUCTIVE SYSTEM.pptx

Physiology of the male reproductive system

INTRODUCTION
 Reproductive system ensures the continuation of species. Gonads are the primary
reproductive organs which produce the gametes (egg or ovum); a pair of testes (singular =
testis) produces sperms in males and a pair of ovaries produces ovum in females.
 Normally, most of the animals including humans are either definite males or definite
females.
 However, in some organisms like earthworms and snails, both sexes may be present in the
same organism and this condition is known as hermaphroditism.
 In humans and most of the higher animals, reproduction occurs sexually, i.e. by mating.
However, there are some species like insects which can produce offsprings without mating.

MALE REPRODUCTION
 Reproductive organs include:
 Primary sex organs: Testes
 Accessory sex organs: Seminal
vesicles, Prostate gland, Urethra,
Penis.
External and Internal Genitalia
 Reproductive organs are generally
classified into two groups, namely
external genitalia (genital organs)
and internal genitalia.
 External genital organs in males are
scrotum, penis and urethra.
Remaining sex organs constitute the
internal genitalia.

FUNCTIONAL ANATOMY OF TESTES
 Testes are the primary sex organs or gonads in males. There are two testes in almost all the species.
In human beings, both the testes are ovoid or walnut-shaped bodies that are located and suspended
in a sac-like structure called scrotum.
 Each testis weighs about 15 to 19 g and measures about 5 × 3 cm. Testis is made up of about 900
coiled tubules known as seminiferous tubules, which produce sperms.
 Seminiferous tubules continue as the vas efferens, which form the epididymis. It is continued as vas
deferens. Vas deferens is also called ductus deferens, spermatic deferens or sperm duct.
 From epididymis in scrotum, the vas deferens extends on its one side upwards into abdominal cavity
via inguinal canal. Terminal portion of vas deferens is called ampulla. Ampulla of vas deferens joins
ducts of seminal vesicle of same side, to form ejaculatory duct.
 Thus, there are two ejaculatory ducts each of which receives sperm from vas deferens and
secretions of seminal vesicle on its own side.
 Both the ejaculatory ducts empty into a single urethra. Actually, ejaculatory ducts open into
prostatic part of urethra.

Each testis is enclosed by three coverings.
 Tunica Vasculosa
 Tunica vasculosa is the innermost covering. It is
made up of connective tissue and it is rich in
blood vessels
 Tunica Albuginea
 Tunica albuginea is the middle covering. It is a
dense fibrous capsule
 Tunica Vaginalis
 Tunica vaginalis is the outermost closed cleft
like covering, formed by mesothelial cells.
 It is formed by visceral and parietal layers,
which glide on one another and allow free
movement of testes.
 Visceral layer of tunica vaginalis adheres to
tunica albuginea and the parietal layer lines the
inner surface of the scrotum.
 Anterior and lateral surfaces of testis are
covered by all the three layers. Posterior surface
is covered by tunica albuginea only.

Pathway for the passage of sperms
 Seminiferous Tubules
 Each lobule contains 1 to 4 coiled tubules known as the
seminiferous tubules, which are surrounded and supported by
interlobular connective tissue. Seminiferous tubules do not
end bluntly, but form single, double or triple arches.
 Limbs of an arch are not in the same lobule.
 Rete Testis
 Rete testis is a network of thin-walled channels present in
mediastinum. All the seminiferous tubules open into the rete
testis.
Vas Efferens
 From rete testis, 8 to 15 tubules called vas efferens arise. Vas
efferens join together and form the head of epididymis and
then converge to form the duct of epididymis.
Epididymis
 Duct of epididymis is an enormously convoluted tubule, with
a length of about 4 meter. It begins at head, where it receives
vas efferens.
Vas Deferens
 At the caudal pole of testis, epididymis turns sharply upon
itself and continues as vas deferens, without any definite
demarcation.

SEMINIFEROUS TUBULES
 Seminiferous tubules are thread-like convoluted tubular structures which produce the spermatozoa
or sperms.
 There are about 400 to 600 seminiferous tubules in each testis. Each tubule is 30 to 70 cm long with
a diameter of 150 to 300 μ.
 Sertoli cells are the supporting cells for spermatogenic cells in seminiferous tubules. These cells are
also called sustentacular cells or nurse cells.
 Sertoli cells are the large and tall irregular columnar cells, extending from basement membrane to
lumen of the seminiferous tubule.
 Germ cells present in seminiferous tubule are attached to Sertoli cells by means of cytoplasmic
connection.
 This attachment between germ cells and Sertoli cells exists till the matured spermatozoa are
released into the lumen of seminiferous tubules.

Functions of Sertoli cells
 Sertoli cells provide support, protection and nourishment for the spermatogenic cells
present in seminiferous tubules.
Sertoli cells:
1. Support and nourish the spermatogenic cells till the spermatozoa are released from them
2. Secrete the enzyme aromatase, which converts androgens into estrogen
3. Secrete androgen-binding protein (ABP), which is essential for testosterone activity,
especially during spermatogenesis
4. Secrete estrogen-binding protein (EBP)
5. Secrete inhibin, which inhibits FSH release from anterior pituitary
6. Secrete activin, which has opposite action of inhibin (increases FSH release)
7. Secrete müllerian regression factor (MRF) in fetal testes. MRF is also called müllerian
inhibiting substance (MIS). MRF is responsible for the regression of müllerian duct during sex
differentiation in fetus.

Blood-testes Barrier
 Blood-testes barrier is a mechanical barrier that separates blood from seminiferous tubules of the
testes.
 It is formed by tight junctions between the adjacent Sertoli cells, near the basal membrane of
seminiferous tubule.
Functions of blood-testes barrier
 Protection of seminiferous tubules
 Blood-testes barrier protects the seminiferous tubules and spermatogenic cells by preventing the
entry of toxic substances from blood and fluid of the surrounding tissues into the lumen of
seminiferous tubules.
 However, blood-testes barrier permits substances essential for spermatogenic cells.
 Prevention of autoimmune disorders: Blood-testes barrier also prevents the development of
autoimmune disorders by inhibiting the movement of antigenic products of spermatogenesis, from
testis into blood.

GAMETOGENIC FUNCTIONS OF TESTES –
SPERMATOGENESIS
 Spermatogenesis is the process by which
the male gametes called spermatozoa
(sperms) are formed from the primitive
spermatogenic cells (spermatogonia) in
the testis.
 It takes 74 days for the formation of
sperm from a primitive germ cell.
Throughout the process of
spermatogenesis, the spermatogenic cells
have cytoplasmic attachment with Sertoli
cells.
 Sertoli cells supply all the necessary
materials for spermatogenesis through
the cytoplasmic attachment.
 Spermatogenesis occurs in four stages:
1. Stage of proliferation
2. Stage of growth
3. Stage of maturation
4. Stage of transformation.

FACTORS AFFECTING
SPERMATOGENESIS
Spermatogenesis is
influenced by:
1. Sertoli cells
2. Hormones
3. Other factors.

HORMONES SECRETED BY TESTES
 Testes secrete male sex hormones, which are collectively called the androgens.
 Androgens secreted by testes are:
1. Testosterone
2. Dihydrotestosterone
3. Androstenedione.

FUNCTIONS OF TESTOSTERONE
 Testosterone performs three functions in fetus:
 Sex differentiation in fetus
 Development of accessory sex organs
 Descent of the testes.
 Testosterone has two important functions in adult:
 Effect on sex organs
 Effect on secondary sexual characters.

Regulation of
testosterone
secretion

MALE ANDROPAUSE OR CLIMACTERIC
 Male andropause or climacteric is the condition in men, characterized by emotional and
physical changes in the body, due to low androgen level with aging.
 It is also called viropause. After the age of 50, testosterone secretion starts declining. It is
accompanied by decrease in number and secretory activity of Leydig cells.
 Low level of testosterone increases the secretion of FSH and LH, which leads to some
changes in the body. It does not affect most of the men.
 But some men develop symptoms similar to those of female menopausal syndrome.
Common symptoms are hot flashes, illusions of suffocation and mood changes.

APPLIED PHYSIOLOGY
 EFFECTS OF EXTIRPATION OF TESTES
 HYPERGONADISM IN MALES
 HYPOGONADISM IN MALES

STRUCTURE OF SEMINAL VESICLES
 Seminal vesicles are the paired glands situated in lower abdomen on either side of prostate
gland behind urinary bladder.
 Each seminal vesicle is a hollow sac of irregular shape and is lined by complexly folded
mucous membrane.
 Epithelial cells of the mucous membrane are secretory in nature and secrete seminal fluid.
Duct of seminal vesicle from each side joins with ampulla of vas deferens to form
ejacculatory duct.
 Thus seminal fluid is emptied into ejaculatory ducts, which open into urethra.

PROPERTIES AND
COMPOSITION OF SEMINAL
FLUID
 Seminal fluid is mucoid and
viscous in nature. It is neutral
or slightly alkaline in
reaction.
 It adds to the bulk of semen
as it forms 60% of the total
semen.

FUNCTIONS OF SEMINAL FLUID
 NUTRITION TO SPERMS
 CLOTTING OF SEMEN
 FERTILIZATION

PROSTATE GLAND
 Human prostate gland weighs about 40 g. It consists of 20 to 30 separate glands, which
open separately into the urethra.
 These glands are tubuloalveolar in nature. Epithelial lining of these glands is made up of
columnar cells.
 Prostate secretes prostatic fluid, which is emptied into prostatic urethra through prostatic
sinuses

PROPERTIES AND
COMPOSITION OF
PROSTATIC FLUID
 Prostate fluid is a thin,
milky and alkaline fluid.
 It forms 30% of total
semen.

FUNCTIONS OF PROSTATIC FLUID
 MAINTENANCE OF SPERM MOTILITY
 CLOTTING OF SEMEN
 LYSIS OF COAGULUM

APPLIED PHYSIOLOGY – ENLARGEMENT OF PROSTATE GLAND

Semen
 Semen is a white or grey fluid that contains sperms. It is the collection of fluids from testes,
seminal vesicles, prostate gland and bulbourethral glands.
 Semen is discharged during sexual act and the process of discharge of semen is called
ejaculation.
 Testes contribute sperms. Prostate secretion gives milky appearance to the semen.
Secretions from seminal vesicles and bulbourethral glands provide mucoid consistency to
semen.

NATURE OF SEMEN
 At the time of ejaculation, human semen is liquid in nature. Immediately, it coagulates and
after some time it becomes liquid once again (secondary liquefaction).
 Fibrinogen secreted from the seminal vesicle is converted into a weak coagulum by the
clotting enzymes secreted from prostate gland.
 Coagulum is liquefied after about 30 minutes, as it is lysed by fibrinolysin produced in
prostate gland.
 When semen is ejaculated, the sperms are nonmotile due to the viscosity of coagulum.
When the coagulum dissolves, the sperms become motile.

PROPERTIES OF SEMEN
 Specific gravity : 1.028
 Volume : 2 mL to 6 mL per ejaculation
 Reaction : It is alkaline with a pH of 7.5.
 Alkalinity is due to the prostate fluid.

Sperm
 Sperm is the male gamete (reproductive cell), developed in the testis. It is also called
spermatozoon (plural = spermatozoa). Matured sperm is 60 μ long.
Sperm Count
 Total count of sperm is about 100 to 50 million/mL of semen. Sterility occurs when the
sperm count falls below 20 million/mL.
 Though the sperms can be stored in male genital tract for longer periods, after ejaculation
the survival time is only about 24 to 48 hours at a temperature equivalent to body
temperature.
 Rate of motility of sperm in female genital tract is about 3 mm/minute. Sperms reach the
fallopian tube in about 30 to 60 minutes after sexual intercourse.
 Uterine contractions during sexual act facilitate the movement of sperms.

Structure of Sperm
Sperm consists of four parts: Head, Neck, Body,
Tail.
Head
 Head of sperm is oval in shape (in front
view), with a length of 3 to 5 μ and width
of up to 3 μ. Anterior portion of head is
thin.
 Head is covered by a thin cell membrane
and it is formed by a condensed nucleus
with a thin cytoplasm.
 Anterior two thirds of the head is called
acrosome or galea capitis.
Acrosome
 Acrosome is the thick cap like anterior part
of sperm head. It develops from Golgi
apparatus and it is made up of
mucopolysaccharide and acid phosphatase.
 Acrosome also contains hyaluronidase and
proteolytic enzymes, which are essential
for the sperm to fertilize the ovum.

NECK
 Head is connected to the body by a short neck. Its anterior end is formed by thick disk-shaped
anterior end knob, which is also called proximal centriole.
 Posterior end is formed by another similar structure known as posterior end knob. It gives rise to
the axial filament of body.
 Often, the neck and body of sperm are together called midpiece. Body is cylindrical with a length of
5 to 9 μ and the thickness of 1 μ.
 The body of the sperm consists of a central core called axial filament, covered by thin cytoplasmic
capsule.
 Axial filament starts from posterior end knob of the neck. It passes through the body and a
perforated disc called end disk or end ring centriole.
 Finally, the axial filament reaches the tail as axial thread. In the body, the axial filament is
surrounded by a closely wound spiral filament consisting of mitochondria.

Tail
 Tail of the sperm consists of two segments:
i. Chief or main piece: It is enclosed by cyto - plasmic capsule and has an axial thread. It is 40
to 50 μ long
ii. Terminal or end piece: It has only the axial filament.

SEMEN ANALYSIS
 Analysis of semen evaluates the qualities of semen, which is useful to investigate the
infertility.
 Parameters of semen analysis:
1. Volume
2. Reaction and pH
3. Liquefaction
4. Sperm count
5. Morphology of sperm
6. Motility of sperms
7. Pus cells and RBCs
8. Fructose level.

QUALITIES OF SEMEN REQUIRED FOR FERTILITY
 Minimum required qualities of semen for fertility are:
1. Volume of semen per ejaculation must be at least
2 mL
2. Sperm count must be at least 20 million/mL
3. Number of sperms in each ejaculation must be at least 40 million
4. 75% of sperms per ejaculation must be alive
5. 50% of sperms must be motile
6. 30% of sperms must have normal shape and structure
7. Sperms with head defect must be less than 35%
8. Sperms with midpiece defect must be less than 20%
9. Sperms with tail defect must be less than 20%.

Fertility control
 Fertility control is the use of any method or device to prevent pregnancy. It is also called
birth control, family planning or contraception.
 Fertility control techniques may be temporary or permanent.
 Several methods are available for fertility control.

Rhythm method
 Rhythm method of fertility control is based on the time of ovulation. After ovulation, i.e. on
the 14th day of menstrual cycle, the ovum is fertilized during its passage through fallopian
tubes.
 Its viability is only for 2 days after ovulation and should be fertilized within this period.
Sperms survive only for about 24 to 48 hours after ejaculation in the female genital tract.
 If sexual intercourse occurs during this period, i.e. between few days before and few days
after ovulation, there is chance of pregnancy. This period is called the dangerous period.
 Pregnancy can be avoided if there is no sexual intercourse during this period. The
prevention of pregnancy by avoiding sexual mating during this period is called rhythm
method.
 The periods, when pregnancy does not occur are 4 to 5 days after menstrual bleeding and 5
to 6 days before the onset of next cycle. These periods are together called safe period.

Advantages and Disadvantages
 It is one of the most successful methods of fertility control provided the woman knows the
exact day of ovulation.
 However, it is not a successful method because of various reasons. Basic knowledge about
the menstrual cycle is necessary to determine the day of ovulation.
 Self-restraint is essential to avoid sexual intercourse. Because of the practical difficulties,
this method is not popular.

MECHANICAL BARRIERS – PREVENTION OF ENTRY OF SPERM INTO UTERUS
 Mechanical barriers are used to prevent the entry of sperm into uterine cavity. These
barriers are called condoms.
 The male condom is a leak proof sheath, made of latex. It covers the penis and does not
allow entrance of semen into the female genital tract during coitus.
 In females, the commonly used condom is cervical cap or diaphragm. It covers the cervix
and prevents entry of sperm into uterus.

CHEMICAL METHODS
 Chemical substances, which destroy the sperms, are applied in female genital tract before
coitus.
 Destruction of sperms is called spermicidal action.
 The spermicidal substances are available in the form of foam tablet, jelly, cream and paste.

ORAL CONTRACEPTIVES (PILL METHOD)
 Oral contraceptives are the drugs taken by mouth (pills) to prevent pregnancy. These pills
prevent pregnancy by inhibiting maturation of follicles and ovulation.
 This leads to alteration of normal menstrual cycle. The menstrual cycle becomes the
anovulatory cycle.
 This method of fertility control is called pill method and pills are called contraceptive pills
or birth control pills.
 These pills contain synthetic estrogen and progesterone. Contraceptive pills are of three
types:
 Classical or combined pills
 Sequential pills
 Minipills or micropills.

CLASSICAL OR COMBINED PILLS
 Classical or combined pills contain a moderate dose of synthetic estrogen like ethinyl estradiol or
mestranol and a mild dose of synthetic progesterone like norethindrone or norgestrol.
 Pills are taken daily from 5th to 25th day of menstrual cycle. The withdrawal of the pills after 25th
day causes menstrual bleeding. The intake of pills is resumed again after 5th day of the next cycle.
Mechanism of Action
 During the continuous intake of the pills, there is relatively large amount of estrogen and
progesterone in the blood.
 It suppresses the release of gonadotropins, FSH and LH from pituitary by means of feedback
mechanism.
 Lack of FSH and LH prevents the maturation of follicle, and ovulation. In addition, progesterone
increases the thickness of mucosa in cervix, which is not favorable for transport of sperm.
 When the pills are withdrawn after 21 days the menstrual flow starts.

SEQUENTIAL PILLS
 Sequential pills contain a high dose of estrogen along with moderate dose of progesterone.
These pills also prevent ovulation.
 Sequential pills are taken in two courses:
 Daily for 15 days from 5th to 20th day of the menstrual cycle and then
 During the last 5 days, i.e. 23rd to 28th day.

MINIPILLS OR MICROPILLS
 Minipills contain a low dose of only progesterone and are taken throughout the menstrual
cycle.
 It prevents pregnancy without affecting ovulation. The progesterone increases the thickness
of cervical mucosa, so that the transport of sperms is inhibited.
 It also prevents implantation of ovum.

DISADVANTAGES AND ADVERSE EFFECTS OF ORAL CONTRACEPTIVES
 About 40% of women who use contraceptive pills may have minor transient side effects. However,
long term use of oral contraceptives causes some serious side effects.
 Following are the disadvantages and adverse effects of oral contraceptives:
 Major practical difficulty is the regular intake of the pills
 May not be suitable for women having disorders such as diabetes, cardiovascular diseases or liver
diseases
 Clotting tendency of blood due to suppressed production of anticoagulants in liver
 Hypertension and heart attack
 Increases the risk of stroke
 Tenderness of breast and risk of breast cancer (but may decrease the risk of ovarian and uterine
cancer).
 To avoid taking pills daily, the long-term contraceptives are used. These contraceptives are in the
form of implants containing mainly progesterone.
 The implants, which are inserted beneath the skin release the drug slowly and prevent fertility for 4
to 5 years. Though it seems to be effective, it may produce amenorrhea.

INTRAUTERINE CONTRACEPTIVE DEVICE (IUCD) – PREVENTION OF FERTILIZATION AND IMPLANTATION OF
OVUM
 Fertilization and the implantation of ovum are prevented by inserting some object made from metal or plastic
into uterine cavity. Such object is called intrauterine contraceptive device (IUCD).
MECHANISM OF ACTION OF IUCD
 Intrauterine contraceptive device prevents fertilization and implantation of the ovum. The IUCD with copper
content has spermicidal action also.
 The IUCD which is loaded with synthetic progesterone slowly releases progesterone. Progesterone causes
thickening of cervical mucus and prevents entry of sperm into uterus.
 The common IUCDs are Lippes loop, which is ‘S’ shaped and made of plastic and copper T, which is made up of
copper. It is inserted into the uterine cavity by using some special applicator.
DISADVANTAGES OF IUCD
IUCD has some disadvantages. It has the tendency to:
 Cause heavy bleeding in some women
 Promote infection
 Come out of uterus accidentally.

MEDICAL TERMINATION OF PREGNANCY (MTP) – ABORTION
 Abortion is done during first few months of pregnancy. This method is called medical
termination of pregnancy (MTP). There are three ways of doing MTP.
DILATATION AND CURETTAGE (D AND C)
 In this method, the cervix is dilated and the implanted ovum or zygote is removed.
VACUUM ASPIRATION
 The implanted ovum is removed by vacuum aspiration method. This is done up to 12 weeks
of pregnancy.
ADMINISTRATION OF PROSTAGLANDIN
 Administration of prostaglandin like PGE2 and PGF2 intravaginally increases uterine
contractions resulting in abortion.

SURGICAL METHOD (STERILIZATION) – PERMANENT METHOD
 Permanent sterility is obtained by surgical methods. It is also called sterilization.
TUBECTOMY
 In tubectomy, the fallopian tubes are cut and both the cut ends are ligated. It prevents entry of
ovum into uterus.
 The operation is done through vaginal orifice in the postpartum period. During other periods, it is
done by abdominal incision. Tubectomy is done quickly (in few minutes) by using a laparoscope.
 Though tubectomy causes permanent sterility, if necessary recanalization of fallopian tube can be
done using plastic tube by another surgical procedure.
VASECTOMY
 In vasectomy, the vas deferens is cut and the cut ends are ligated. So the sperms cannot enter the
ejaculatory duct and the semen is devoid of sperms.
 It is done by surgical procedure with local anesthesia. If necessary, the recanalization of vas
deferens can be done with plastic tube.

PHYSIOLOGY OF THE MALE REPRODUCTIVE SYSTEM.pptx

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