Histology of Testis by Dr Mohammad Manzoor Mashwani
TestisDr Mohammad Manzoor Mashwani
Size of testis
In healthy European males, the average
volume of each testicle is 18cm2. The
average size after puberty measures to
around 2 inches in length, 0.8 inches in
breadth and 1.2 inches in height.
1. Spermatozoa (EXOCRINE FUNCTION)
2. Testosterone (ENDOCRINE FUNCTION)
It is a compound tubular gland of the cytogenic
There are two layers of the tunica vaginalis: the
visceral and the parietal. The visceral layer overlies
the tunica albuginea (middle layer of the tunica)
while the parietal layer lines the scrotal cavity. A
thin fluid layer separates the two sections of the
tunica vaginalis and reduces friction between the
testes and the scrotum. An increased quantity of
fluid between these layers can form a
hydrocoele(an accumulation of fluid).
• Each testis is covered by a thick capsule
called Tunica Albuginea.
• It is composed mainly of collagenous
fibers but also contains smooth muscle
Posteriorly the tunica albuginea
is thickened and projects into
the gland as mediastinum
• Thin fibrous septa, called Septula testis, radiate
from the midiastinum to the capsule and divide
the interior of the testis into 200 to 300
• The septula are not complete partitions; they show
numerous gaps, through which the testicular
lobules communicate quite freely.
• Beneath the tunica albuginea there
is a layer of loose areolar
connective tissue containing
networks of blood vessels .This layer
, known as tunica vasculosa, also
lines the Septula Testis.
• Each testicular lobule contains 1-4 highly
convoluted Seminiferous Tubules, surrounded and
supported by Intertubular Connective Tissue.
• Each seminiferous tuble is intricately coiled
,averaging about 0.2 mm diameter and 50 cm in
• Individual tubules usually commence as Free Blind
Ends but neighbouring tubules may form
At the apex of the testicular lobule
seminiferous tubules lose their
convolutions and become straight.
Theses short straight segments,
known as Tubulo Recti, constitute
the initial part of the male genital
The tubule recti pass into
the mediastinum testis and
join a network of
The Rete Testis.
From the Rete Testis arise 10-20
spirally wound efferent ductules (
Ductuli Efferentes) which leave the
testis and open into the Duct of
• Seminiferous tubule is lined by a complex
Germinal or Seminiferous Epithelium.
• It is a modified stratified cuboidal
• The epithelium rests on a thin Basal
Seminiferous Epithelium (Germinal
Epithelium) is surrounded
externally by a thin layer of
connective tissue called Tunica
Spermatogenic or Germ Cells
• These cells lie Between The Sortoli Cells.
• They form a Stratified Epithelium.
• Consisting of Several Layers of cells which occupy
the space between the Basal Lamina and Lumen of
the Seminiferous Tubule.
Spermatogenic cells cont..
CHILD: In the testis of a child only the Primitive
Germ cells, called Spermatogonia are present.
• However, with the onset of Sexual maturity the
process of spermatogenesis starts and the
spermatogenic cells are seen in various stages of
differentiation, arranged in an orderly manner.
Spermatogonia (The primitive germ cells)
The most immature cells
located near the basal
The spermatogonia ( average diameter 12um)
are located directly inside the basal lamina of
the seminiferous epithelium.
They are roughly spherical cells, each
containing a centrally located, round
Types of Spermatogonia
Depending on the nuclear structure , the
spermatogonia can be classified into three types in
an adult person.
These three types are:
i. Type A dark spermatogonia,
ii. Type A pale spermatogonia and
iii. Type B spermatogonia
The Type A Dark Spermatogonia
Contain an oval, darkly- staining nucleus , in
which the nucleolus is located close to the
They are reserve cells and divide occasionally
to maintain their own number and give rise
Type A Pale Spermatogonia.
Type A Pale Spermatogonia
Contain a light –staining nucleus.
The nucleolus is located close to nuclear
These cells divide regularly to give rise to other
Type A Pale Spermatogonia as well as
Type B Spermatogonia.
The Type B Spermatogonia
Have a spherical nucleus that shows
Darkely Staining Clumps of Chromotain located
adjacent to the nuclear envelope.
The nucleolus is situated in the center of nucleus.
Each type B spermatogonium divide mitotically a few
times to give rise to a number of daughter cells
which do not divide further but transform into
Stages of development of spermatogenic cells
• Usually four to five concentric layers of
morphologically distinct spermatogenic cells,
representing generations of cells at various stages
of development, can be identified in the
• Starting with a spermatogonium
these stages include Primary
Spermatocyte, and Spermatid.
As the cells proliferate and undergo
differentiation, they gradually move
towards the lumen of the tubule.
Finally the cells come to lie at the luminal
surface of the seminiferous tubule, where
they transform into spermatozoa
which become free to lie within the
lumen of the tubule.
The primary spermatocytes lie
next to the spermatogonia.
They are large cells (diameter
18um) having vesicular
These are smaller cells
that arise from a
primary spermatocyt as
a result of First Meiotic
Produced from the secondary spermatocytes by the
second meiotic division.
They lie adjacent to the lumen of the siminiferous
closely applied to the surface of Sertoli cells.
A spermatid does not divide further but is
transformed into a spermatozoon
by a series of morphological changes
which are collectively known as
Testicular biopsy showing numerous seminiferous tubules with normal spermatogenesis
Note the orderly maturation of germ cells from the base to the center of the lumen.
Spermatogonia (along the basement membrane), primary & secondary spermatocytes
spermatids, and spermatozoa are seen.
Sertoli cells/Sustentacular cells/Nurse
cells/Mother cells/Tree cells/Stringy cells
• Sertoli cells are called so because of their eponym
Enrico Sertoli, an Italian physiologist who
discovered them while studying medicine in the
University of Pavia, Italy.
• He published a description of this cell in 1865. In
the 1865 publication, his first description used the
terms "tree-like cell" or "stringy cell" and most
importantly he referred to these "mother cells." It
was other scientists who used Enrico's family name,
Sertoli, to label these cell in publications, starting in
Sertoli Cells or Sustentacular Cells
• These are tall columnar cells that
• Extend from the basal lamina to the
lumen of the seminiferous tubule,
• Interposed between the developing
Sustentacular Cells or Sertoli Cells
• Each Sertoli cell is 70-90 um long and
nearly 3o um wide.
• Due to their loose association with
spermatogenic cells, the lateral margins
of Sertoli cells are irregular and can not
easily be distinguished under L/M.
• Each sustentacular cell has a large pale- staining
(euchromatic) nucleus which is located in the basal
portion of the cell.
• The nucleus exibits two distinctive features:
• 1) the nuclear envelope shows many infoldings,
• 2) the nucleolus is very prominent (Dark
Luminal surface of a Sertoli cell
shows many grooves in which heads of the
maturating spermatozoa are embeded.
Sustentacular or Sertoli cells
The cytoplasm of a Sertoli cell is seen to
2. Glycogen granules and
E/M shows that these cells contain:
1. A well-developed Golgi apparatus,
2. An abundant smooth endoplasmic reticulum,
3. Some rough endoplasmic reticulum,
4. Numerous mitochondria and
5. Many lysosomes.
Functions of Sertoli cells
• A Sertoli cell is a 'nurse' cell or
‘mother’ cell of the testes.
• It is activated by follicle-stimulating
hormone and has FSH-receptor on
Functions of Sertoli Cells
1.Support, protection and nutritional
regulation of developing spermatozoa.
Adjacent Sertoli cells are bound together
by occluding junctions just above the
level of spermatogonia, which lie in a
basal compartment that has free access
to material carried in blood.
Functions of Sertoli cells cont…
• The spermatocytocytes cross these junctions
and come to lie in an adluminal
• This compartment is protected from blood-
borne materials by a blood-testis barrier
formed by occluding junctions between
Functions of Sertoli Cells cont..
• The spermatocytes, spermatids and developing
spermatozoa are isolated from the blood circulation
and depend on Sertoli cells to mediate the
exchange of nutrients and metabolites.
• The blood-testis barrier protects the cells in the
adluminal compartment from blood-born harmful
substances and from autoimmune reaction against
Functions of Sertoli Cells cont…
2. Secretions: Sustentacular cells of Sertoli
secrete a fluid into the lumen of the seminiferou
tubules which flows in the direction of genital ducts
and is used for sperm transport.
• Sertoli cells secrete the following substances:
• anti-Müllerian hormone (AMH) - secreted during
the early stages of fetal life.
• inhibin and activins - secreted after puberty, and
work together to regulate FSH secretion
• androgen binding protein (also called testosterone
binding globulin) - increases testosterone
concentration in the seminiferous tubules to
• estradiol - aromatase from Sertoli cells convert
testosterone to 17 beta estradiol to direct
• glial cell line-derived neurotrophic factor (GDNF) -
has been demonstrated to function in promoting
undifferentiating spermatogonia, which ensures
stem cell self-renewal during the perinatal period.
• the Ets related molecule (ERM transcription factor) -
needed for maintenance of the spermatogonial
stem cell in the adult testis.
• transferrin - a blood plasma protein for iron ion
Functions of Sertoli Cells cont….
During sperminogenisis excess
spermatid cytoplasm is shed as
residual bodies which are
phagocytized and broken down by
Functions of Sertoli Cells cont…
During the maturation phase of
spermiogenesis, the Sertoli cells consume the
unneeded portions of the spermatozoa.
• These are slender, motile, flagellate bodies,
each having an average length of 60 um.
• A mature spermatozoon (Sperm) consist of
two main parts, a head and a tail .
• The junctional region between these two
parts is referred to as neck. All these parts
are covered by a plasma membrane.
The Spermatozoa cont…
• Head: The head is a flattened, pear-shaped body
measuring about 4um in length, 3um in width and
1um in thickness.
• It consist chiefly of the condensed nucleus, present
as a compact mass of chromatin enclosed in the
The anterior two third of the nucleus are covered by a
flattened, membrane bound sac called acrosomal cap.
This cap has been found to contain hydrolytic
enzymes like hyaluronidase, etc.
Plasmlemma. The entire sperm , including the head, is
covered by a plasmalemma.
The Spermatozoa cont……
• The Neck: The neck is a short region
between the head and tail of the sperm.
It contains the proximal centriole
running fibers that become continuous
with those of the middle piece of the tail.
The Tail of spermatozoa
Has 3 segments:
Interstitial Cells of Leydig
• Leydig cells, also known as interstitial
cells of Leydig, are found adjacent to the
seminiferous tubules in the testicle. They
produce testosterone in the presence of
luteinizing hormone (LH).
• Leydig cells are named after the German
anatomist Franz Leydig, who discovered
them in 1850
• Leydig cells are polyhedral in
shape, display a large prominent
nucleus, an eosinophilic
cytoplasm and numerous lipid-
Leydig cell has a single eccentrically
located ovoid nucleus. The nucleus
contains one to three prominent
nucleoli and large amounts of dark-
staining peripheral heterochromatin.
• The acidophilic cytoplasm usually contains
numerous membrane-bound lipid droplets
and large amounts of smooth endoplasmic
• Besides the obvious abundance of
SER with scattered patches of rough
endoplasmic reticulum, several
mitochondria are also prominent
within the cytoplasm.
• Frequently, lipofuscin pigment and rod-shaped
crystal-like structures 3 to 20 micrometres in
diameter (Reinke's crystals)
are found. These inclusions have no known