Transcript MALE REPRODUCTIVE SYSTEM

MALE
REPRODUCTIVE SYSTEM
dr sikander khan
• Reproduction is the production of
offsprings.
• ‘Re’ is Latin word. It means ‘again’.
• Reproductive system is the system
responsible for the formation of
progeny .
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In male, reproductive system includes:
Two testes, right and left.
Two epididymis, right and left.
Two deferent ducts, right and left.
Two ejaculatory ducts, right and left.
Two seminal vesicles, right and left.
One prostate gland.
One penis.
Two bulbo-urethral glands, right and left.
• Testes are the primary sex organs. Here
the male gametes are formed.
• Epididymis, deferent ducts and ejaculatory
ducts transport mature male gametes
(sperms) to the organ of copulation.
• Penis is the organ of copulation.
• Seminal vesicles, prostate gland and
bulbo-urethral glands are associated
accessory glandular structures.
Testes
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These are primary reproductive organs.
They are homologous to ovaries in female.
They are ellipsoidal shaped structures.
They are not in pelvis, different to ovaries.
They are included in external genitalia and
suspended in the scrotum.
• Left testis is usually about 1 cm lower than
the right.
• Each testis is compressed laterally, having
upper and lower poles, medial and lateral
surfaces and anterior and posterior
borders. The anterior border is convex
and posterior border is nearly straight.
• Average testicular dimensions are 4-5 cm
in length, 2.5 cm breadth and 3 cm anteroposterior diameter.
• Their weight varies from 10.5-14 g.
COVERINGS OF TESTIS
• Tunica Vaginalis is like peritoneum. It
covers the whole testis except posterior
border.
• Tunica albuginea is a dense irregular
connective tissue. It forms the true capsule
of testis.
• Tunica Vasculosa is present internal to
tunica albuginea.
• Microscopic picture of testis showing three
coats of testis.
MICROSCOPIC STRUCTURE
• There are 200-300 lobules in each testis.
• Each lobule contains 1-3 horseshoe
shaped highly convoluted seminiferous
tubules embedded in loose connective
tissue.
• This loose connective tissue contains
groups of interstitial cells of Leydig outside
the seminiferous tubules.
SEMINIFEROUS TUBULES
• Highly convoluted tubules. About 0.2mm in
diameter and 50cm in length. Horseshoe
shaped. The ends are straight. Here they are
given the name straight tubules. The straight
tubules open into the rete testis.
• Each seminiferous tubule is lined by complex
stratified epithelium called seminiferous
epithelium. The epithelium rests on a thin basal
lamina, which is covered by connective tissue
containing fibroblasts, numerous fibers and
myoid cells.
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Sustentacular Cells of Sertoli.
Spermatogenic Cells
Sustentacular Cells of Sertoli
• These are tall columnar cells resting on
basal lamina of seminiferous tubules. The
cell outline is very irregular and indistinct.
They have invaginations on their basal
surfaces, their sidewalls and their luminal
surfaces.
• The nucleus is towards the base. It is
located some distance above the base of
the cell. It is pale and ovoid. It contains a
nucleolus.
• The adjacent surfaces show complex
occluding junctions.
• These junctions are near the bases and
constitute blood-testis barrier.
Spermatogenic Cells
• These are germ cells.
• They form a stratified layer of epithelium
consisting of four to eight cell types.
Spermatogonia:
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Until puberty these are the only germ cell type
present. They occupy a space present
between the basal lamina and sertoli cells.
They contain 46 chromosomes.
Three basic types of spermatogonia are:
1. Type A dark spermatogonia
2. Type A pale spermatogonia
3. Type B spermatogonia
Spermatogonia multiply by mitosis.
Primary Spermatocytes:
• Some of the spermatogonia cells enlarge and
differentiate into primary spermatocytes. They
are the largest germ cells seen within
seminiferous tubules. Initially they are in the
basal compartment of seminiferous tubule.
Then they cross blood-testis barrier and lie
between the adjacent Sertoli cells. Here they
are in the invaginations present in the lateral
walls of Sertoli cells
• Each cell is spherical or ovoid in outline. They
contain 46 chromosomes.
Secondary Spermatocytes:
• Primary spermatocytes undergo first
meiotic division and form secondary
spermatocytes.
• These are about half the size of primary
spermatocytes.
• They lie in the invaginations in the lateral
walls of Sertoli cells near the lumen of the
seminiferous tubules.
• They contain 23 chromosomes.
Spermatids:
• Secondary spermatocytes undergo
second meiotic division and form
spermatids. These are about the size of
secondary spermatocytes and contain 23
chromosomes.
• They migrate to the luminal surface of
Sertoli cell and lie in the invaginations
there.
• Here they transform into spermatozoa by a
process called spermiogenesis.
Spermatozoa:
• Each spermatozoon is 60 µm in length
• It consists of head, neck, middle piece and
tail.
• Head is 4 µm in length, 3 µm in width and
1 µm in thickness
• It has
– a nucleus
– with a cap called acrosome
– surrounded by cell membrane
• Middle piece is separated from head by a
narrow neck.
• It is 7 µm in length and 1 µm in diameter
• It contains
– Axoneme
a core of longitudinal filaments
2+9 arrangement
– surrounded by nine dense fibers
– surrounded by a sheath of mitochondria
– Surrounded by cell membrane
• Tail has two parts
1. Principle piece is 40 µm in length. It
consists of
– Axoneme. It has two central and nine
peripheral double filaments
– Seven outer dense fibers
– Fibrous sheath
– Cell membrane
2. End piece (8 µm in length) has axoneme
and cell membrane only
• Heads are embedded in the invaginations
on luminal surfaces of Sertoli cells
• and tails float in the lumen of seminiferous
tubules.
Sperms:
• When the spermatozoa become detached
from Sertoli cell and free in the lumen of
seminiferous tubules they are called
sperms.
• The interstitial tissue, within the lobules is
loose connective tissue containing.
• Cells. Fibroblasts, macrophages, mast
cells, undifferentiated mesenchymal cells
and interstitial cells of Leydig.
• Collagen fibers.
• Blood and lymph vessels.
• Nerves.
• The specific interstitial cells of Leydig are a
marked feature of this tissue.
• They lie in groups.
• They are large rounded cells contain central
rounded nucleus.
• The nucleus contains course chromatin
granules and a distinct nucleolus.
• Under electron microscopy my dear students
you will observe abundant smooth endoplasmic
reticulum.
• Interstitial cells of Leydig secrete testosterone.
• Smooth endoplasmic reticulum is
concerned with synthesis of steroid
hormone.
• Rough endoplasmic reticulum is
concerned with synthesis of proteins.
Spermatogenic Cells
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Spermatogonia:
46 Mitosis
Primary Spermatocytes:
46 Meiosis I
Secondary Spermatocytes: 23 Meiosis II
Spermatids:
23
Spermeogenesis
Spermatozoa:
23
Attached
Sperms:
23
Free
• Spermatogenic cells
– Begin sperm production at puberty
• Sertoli or sustentacular cells
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Junctions form blood-testis barrier
Nourish spermatogenic cells
Carry out phagocytosis
Control spermatogenic movement
Produce fluid for transport
Secrete hormone inhibin
• Leydig (interstitial) cells
– Secrete testosterone
Thanks