male reprodctive system pdf - د. ملاك

Histology of Male Reproductive

system (1)

Prof. Dr. Malak A. Al-yawer

Learning Objectives

 At the end of this lecture, the 2

medical student will be able to:

 State the organization of the testis
 Define seminiferous tubules and interstitial tissue
 List the components of seminiferous tubules
 List the phases of spermatogenesis
 State the histological characteristics of spermatogonia and

distinguish between its two types

 State the histological characteristics of primary & secondary

spermatocytes

 State the histological characteristics of spermatids
 List the phases of spermiogenesis and state the histological

characteristics of each phase

 State the structure and functions of Sertoli cells
 Define blood testis barrier
 List the light and electron microscopic features of leydig cells

Male Reproductive System

is composed of the
1.  testes
2.  genital ducts
3.  accessory glands
4.  penis

Testes

•

Each testis is surrounded by a thick capsule of

dense connective tissue, the tunica albuginea.

•

The tunica albuginea is thickened on the

posterior surface of the testis to form the

mediastinum testis, from which fibrous septa

penetrate the gland, dividing it into about 250

pyramidal compartments called the testicular

lobules

•

These septa are incomplete, and there is

frequent intercommunication between the

lobules.

•

Each lobule is occupied by one to four

seminiferous tubules enmeshed in a web of

loose connective tissue

•

the tunica vaginalis, derived from the

peritoneum. The tunic consists of an outer

parietal layer and an inner visceral layer,

covering the tunica albuginea on the anterior

and lateral sides of the testis

Testis

 Straight tubules(tubuli

recti )are short segments
that connect the
seminiferous tubules to
an anastomosing
labyrinth of epithelium-
lined channels, the rete
testis.

 About 10 -20 ductuli

efferentes connect the
rete testis to the cephalic
portion of the epididymis

The Seminiferous Tubules

Each testicle has 250-

1000 convoluted
seminiferous tubules

 that measure about

150-250 μm in diameter
and 30-70 cm in length.

 The combined length of

the tubules of one testis
is about 250 m.

The seminiferous tubules

 are lined with a complex stratified

epithelium called germinal or
seminiferous epithelium.

 Their outer wall is surrounded by
• a well-defined basal lamina and
• a fibrous connective tissue

consisting of several layers of
fibroblasts. The innermost layer,
adhering to the basal lamina,
consists of flattened myoid cells,
which have characteristics of
smooth muscle.

Interstitial tissue

• is a web of loose

connective tissue found
between the
seminiferous tubules

• is rich in blood and

lymphatic vessels,
nerves, and interstitial
cells, also known as
Leydig cells.

The seminiferous epithelium consists
of two types of cells:

 Sertoli, or supporting,

cells

 cells that constitute the

spermatogenic lineage
which are stacked in
four to eight layers;
their function is to
produce spermatozoa.

Spermatogenesis

Is the process of

production of
spermatozoa

Includes
 Spermatogonial Phase

(Mitosis )

 Spermatocyte Phase

(Meiosis)

 Spermatid Phase

(Spermiogenesis)

Spermatogonia

• Spermatogonium is a primitive germ

cell small in size about 12 μm in

diameter, situated next to the basal

lamina of the epithelium

• At sexual maturity, spermatogonia

begin dividing by mitosis, producing

successive generations of cells. The

newly formed cells can follow one of

two paths:

 they can continue dividing as stem

cells, also called type A

spermatogonia, or

 they can differentiate during

progressive mitotic cycles to

become type B spermatogonia

which are progenitor cells that will

differentiate into primary

spermatocytes .

Primary spermatocytes

• The primary spermatocyte has 46

(44 + XY) chromosomes and 4N of

DNA.

• Soon after their formation, these

cells enter the prophase of the

first meiotic division.

• Because this prophase takes

about 22 days, the majority of

spermatocytes seen in sections

will be in this phase.

• The primary spermatocytes are

the largest cells of the

spermatogenic lineage and are

characterized by the presence of

chromosomes in various stages of

the coiling process within their

nuclei

Secondary spermatocytes

• Smaller cells arise from the first meiotic

division

• with only 23 chromosomes (22 + X or 22 + Y)

& 2N DNA per cell.

• Secondary spermatocytes are difficult to

observe in sections of the testis because they
are short-lived cells that remain in interphase
very briefly and quickly enter into the second
meiotic division.

Spermatids

• Each secondary spermatocyte

results in two spermatids that

contain 23 chromosomes and (1N)

DNA

• The spermatids can be

distinguished by their small size (7-8

μm in diameter) and by nuclei with

areas of condensed chromatin.

• Their position within the

seminiferous tubules is close to the

lumen

• The cytoplasm of spermatids

contains a prominent Golgi complex

near the nucleus, mitochondria, a

pair of centrioles, free ribosomes,

and tubules of smooth endoplasmic

reticulum

Spermiogenesis

• spermatids are transformed into spermatozoa.

No cell division occurs during this process.

• Spermiogenesis is a complex process that

includes

formation of the acrosome
condensation and elongation of the nucleus
development of the flagellum
loss of much of the cytoplasm.

Spermiogenesis can be divided into

three phases.

1. The Golgi Phase
2. The Acrosomal Phase
3. The Maturation Phase

The Golgi Phase

• Proacrosomal granules

accumulate in the Golgi
complex.

• They subsequently

coalesce to form a
single acrosomal
granule within a
membrane-limited
acrosomal vesicle.

• The flagellar axoneme

begins to form

The Acrosomal Phase

 The acrosomal vesicle spreads to

cover the anterior half of the

condensing nucleus and is then

known as the acrosome. The

acrosome contains several

hydrolytic enzymes. It serves as a

specialized type of lysosome.

 During this phase of

spermiogenesis, the nucleus of

the spermatid becomes oriented

toward the base of the

seminiferous tubule, and the

axoneme projects into its lumen.

In addition, the nucleus becomes

more elongated and condensed .

 Mitochondria aggregate around

the proximal part of the flagellum,

forming a thickened region known

as the middle piece

The Maturation Phase

• Residual cytoplasm is shed and

phagocytosed by Sertoli cells,
and the spermatozoa are
released into the lumen of the
tubule.

Sertoli cells

• are elongated pyramidal cells

that partially envelop cells of
the spermatogenic lineage.

• The bases of the Sertoli cells

adhere to the basal lamina,
and their apical ends
frequently extend into the
lumen of the seminiferous
tubule.

• In the light microscope, the

outlines of Sertoli cells appear
poorly defined because of the
numerous lateral processes
that surround spermatogenic
cells .

Setoli cells

• with the electron

microscope, these cells

contain abundant smooth

endoplasmic reticulum,

some rough endoplasmic

reticulum, a well-developed

Golgi complex, and

numerous mitochondria and

lysosomes.

• The nucleus, which is often

triangular in outline,

possesses numerous

infoldings and a prominent

nucleolus; it exhibits little

heterochromatin

Blood testis barrier

• Adjacent Sertoli cells are

bound together by occluding

junctions at the basolateral

part of the cell, forming a

blood testis barrier.

• The spermatogonia lie in a

basal compartment that is

situated below the barrier.

• some of the cells resulting

from division of

spermatogonia somehow

traverse these junctions and

come to lie in the adluminal

compartment situated above

the barrier.

• Sertoli cells are also connected by gap

junctions that provide ionic and
chemical coupling of the cells; this may
be important in coordinating the cycle
of the seminiferous epithelium
described above.

• Sertoli cells in humans and in other animals do

not divide during the reproductive period.

• They
are extremely resistant to adverse conditions

such as infection, malnutrition, and x-
irradiation

have a much better rate of survival after these

insults than do cells of the spermatogenic
lineage

Sertoli cells have several functions

 Support, protection, and nutritional regulation of the developing

spermatozoa.

 Phagocytosis.
 Secretion.
 Sertoli cells continuously secrete a fluid that flows in the direction

of the genital ducts and is used for sperm transport.

 Secretion of an ABP( androgen binding protein) by Sertoli cells is

under the control of follicle-stimulating hormone (FSH) and

testosterone and serves to concentrate testosterone in the

seminiferous tubule, where it is necessary for spermatogenesis.

 Sertoli cells can convert testosterone to estradiol.
 They also secrete a peptide called inhibin, which suppresses

synthesis and release of FSH in the anterior pituitary gland

Sertoli cells have several functions

 Production of the anti-müllerian hormone.
• acts during embryonic development to promote

regression of the müllerian (paramesonephric)

ducts in the male fetus; testosterone fosters the

development of structures derived from the

Wolffian (mesonephric) ducts.

 The blood testis barrier. The existence of a barrier

between the blood and the interior of the

seminiferous tubules accounts for the fact that few

substances from the blood are found in the

testicular fluid. The testicular capillaries are

fenestrated and permit passage of large molecules.

The interstitial tissue of the testis

 The spaces between the seminiferous tubules in

the testis are filled with connective tissue,
nerves, fenestrated capillaries, and lymphatic
vessels.

 The connective tissue consists of various cell

types, including

 Fibroblasts
 undifferentiated connective cells
 mast cells
 Macrophages
 interstitial, or Leydig cells of the testis which

become apparent during puberty ; it is either
rounded or polygonal in shape and has a central
nucleus and an eosinophilic cytoplasm rich in
small lipid droplets . They have the
characteristics of steroid-secreting cells. These
cells produce the male hormone testosterone by
enzymes present in mitochondria and in the
smooth endoplasmic reticulum.

Summary

 Each testis is divided into about 250 lobules and each lobule is

occupied by 1-4 seminiferous tubules

 Straight tubules(tubuli recti ) connect the seminiferous tubules to

the rete testis and about 10 -20 ductuli efferentes connect the rete

testis to the cephalic portion of the epididymis

 The seminiferous tubules are lined with a germinal or seminiferous

epithelium.

 The seminiferous epithelium consists of cells that constitute the

spermatogenic lineage and Sertoli cells

 Spermatogenesis includes spermatogonial, spermatocyte and

spermatid Phase

 Spermiogenesis can be divided into Golgi, acrosomal and

maturation phases

 Blood testis barrier is formed by occluding junctions between

adjacent Sertoli cells

 interstitial, or Leydig cells of the testis have the characteristics of

steroid-secreting cells i.e. production of testosterone