testes.ppt

8/10/2019 Testes.ppt

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Testes

By

Dr. Nimer Khraim


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Testes

Whereas the visceral layer, the

peritoneal covering of the testis (and

epididymis), remains intimatelyassociated with the underlying capsule

of the testis, the tunica albuginea.


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Testes

The visceral layer of the tunica vaginalis

consists of a mesotheliumand a

connective-tissue layerthat blends withthe tunica albuginea.


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Testes

The tunica albuginea is a solid capsule

of dense irregular connective tissue.

It consists predominantly of collagen

fibers, a few elastic fibers, and

myofibroblasts.


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TestesSEPTULA TESTIS AND MEDIASTINUM

TESTIS

The tunica albuginea is continuous with

connective tissue trabeculae, the so-called

septula testis.Which converge toward the mediastinum

testis.


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Testes

Interstitial Cells

The intertubular spaces contain:

loose connective tissue.

blood and lymph vessels

fibrocytes

free mononuclear cells interstitial endocrine (Leydig) cells


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Testes

Interstitial endocrine cells produce

testicular androgens (steroid)

and, in boars, large amounts of estrogen

as well.


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Testes

Two generationsof interstitial cells, fetal

and pubertal, develop from mesenchyma

like precursors.

In some species, e.g., bovine and

porcine, a third generation of interstitial

cells (early postnatal)is encountered.


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Testes

Interstitial cells constitute approximately

1% of the entire testicular volume in

adult rams, approximately 5% in bulls,and 20 to 30% in boars.

In seasonally breedingmales (e.g.,

camel), interstitial cell volume and

number may change during the year.


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Testes Interstitial endocrine cells occur in cords

or clusters

not every cell is in close contact with a

capillars.

Between adjacent cells are intercellular

canaliculi and gap junctions.

High concentrations ofsteroidsare

found in testicular tissue and lymph.


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Testes

The interstitial endocrine cells are large

polymorphous cells with spherical nuclei

and smooth endoplasmic reticulum

More than 90%of all androgens in the

organism are produced by the testis


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Testes

Among the main functions of testosterone (to be effective, in

some tissue, testosterone must be converted into

dihydroteststerone by the enzyme 5-reductase)are:

(a) promotion of normal sexual behavior (libido).

(b) triggering of the growthand maintenanceof the function of the

penis, male accessory glandsand secondary sex

characteristics .

(c) control of spermatogenesis(together with follicle-stimulating

homone (FSH)

(d) negative feedbackaction on the hypophysis and

hypothalamus

(e) general anabolic effects

(f) the prenatal maintenance of the wolffian ductand itsdifferentiation into deferent duct and epididymis.


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Convoluted Seminiferous

Tubules


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Testes

The convoluted seminiferous tubules

(tubuli seminiferi convoluti) in most

mammals are tortuous two ended loops

with a diameter between 150 and 300m

They are lined by the stratified germinal

epithelium, surrounded by a laminapropria, and connected at both ends to

straight testicular tubules by specialized

terminal segment


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Testes

Histologically, the seminiferous tubules

have three components: lamina propria.

Sustenacular cells (somatic, supporting ,

or Sertoli cells) , and spermatogeniccells


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Testes

SUSTENTACULAR CELLS

Sustentacular cells are derived from

undifferentiated supportingcells of the

prepubertal goned.

These cells Are mitotically active,

contain large amounts of rough

endoplasmic reticulum, and produce theanti-paramesonephric hormone, a

glycoprotein that suppresses

development of uterine tubes, uterus,

and vagina in the male.


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Testes

During puberty, sustentacular cell

emulation is accompanied by a

morphologic transformation and loss ofmitotic capability.

The adultsustentacular cells are

irregularly outlined, elongated cells.

Their broad base rests on the basal

lamina


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Testes

The oval or pear-shaped nucleus is generally

located in the broad basal portion of the cell

and is often deeply infolded and contains a

large nucleolus.

The basal portion and the central trunk region

of the sustentacular cell contain mitochondria,

an inconspicuous Golgi complex, abundantsER, little rER. free ribosomes.


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Testes

The shape of the cell, the surface area,

and the volume percentages of

organelles change in accordance withspermatogenetic events (sustentacular

cell cycle).

Sustentacular cells formhemidesmosomes with the basal lamina.


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Testes

Early spermatocytesmust pass through

these intercellular junctions without

interrupting the physiologic blood-testisbarrier.


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Testes

Sustentacular cells have nutritive,

protective, and supportive functionsfor

the spermatogenic cells.

In addition, they phagocyte degenerating

spermatogenic cells and detached

residual bodies of spermatids.

They release the spermatozoa into the

lumen of the seminiferous tubules

(spermiation).


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Testes

They mediatethe action of FSH andtestosterone on the germ cells

participate, in the synchronizationofspermatogenic events, produce an androgen-binding protein

and secrete constituents of the intratubularfluid, such as transferrin, androgen-bindingprotein, and inhibin.


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Testes

Inhibin is reabsorbedfrom the lumen of

the efferent ductules and the initial

segment of epididymis.

It then reaches the bloodstream and

exerts negative feedbackon

hypophyseal FSH secretion.


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Testes

Although normal sustentacular cells

have only a minimal proven

steroidogenic function

sustentacular cell tumorsmay produce

large amounts of estrogen, leading to

feminizationof the organism.


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Testes

SPERMATOGENIC CELLS

Various spermatogenic cells,

representing different phases in thedevelopment and differentiation of the

spermatozoon, are locatedbetween and

above the sustentacular cells


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Testes

The sequence of events in the

development of spermatozoa from

spermatogonia is referred to asspermatogenesisand is subdivided into

three phases:


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(a) sperniatocytogenesis. the process

during which spermatogoniadevelop

into spermatocytes.

(b) meiosis, the maturation division of

spermatocytes that results in

Spermatids with a reduced (haploid)number of chromosomes.


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Testes

The seminiferous epithelium contains a

separate stem celland spermatogonia

precursorcell line.

Stem cells and spermatogonia precursor

cells are morphologically similarto

spermatogonia and are also located inthe basaltubular compartment


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Testes

In all domestic mammals, most of the

convoluted seminiferous tubules

terminate in the vicinity of the rete testis

they continue into the straight testiculartubules (tubuli recti)

which connectthem to the rete testis.

Straight testicular tubules are shortandhave either a straight or a tortuous

course.


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Testes The straight testicular tubules are lined with a

simple squamous to columnarepithelium.

In bulls, a simple cuboidalepithelium lines the

proximal portionof the Straight tubules

and a simple columnarepithelium lines distal

portion

This epithelium contain numerous

macrophages and lymphocytes and is able to

phagocytespermatozoa.


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Testes

Irregularly anastomosing canals,

surrounded by the loose connective

tissue of the mediastinum testis, form therete testis

It is lined by simple squamous and

columnarepithelium.

Elastic fibersand contractile cells are

present under the epithelium.


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Testes

Most of the testicular fluid, which is

reabsorbed in the head of the

epididymis, is producedin the rete testis

(in the ram approximately 40 mL/day).

Rete testis fluiddiffers in composition

from tubular seminiferous fluid, testicular

lymph, and blood plasma.

testes.ppt

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