Biology Today — January 2018

TESTES : THE PRIMARY MALE SEX ORGANS

Testes are the components of both reproductive system and endocrine system and thus are homologous to ovaries. Though they
develop in the abdominal cavity during early fetal life, they (testes) descend into the scrotum through inguinal canals and remain
suspended in it by spermatic cords. The fibrous cord that extends from the caudal end of the testis to the scrotal wall is called
gubernaculum. Each testes is oval in shape with a length of about 4-5 cm and width of about 2-4 cm. The peritoneum called
mesorchium supports the testis. Testes produce sperms (by spermatogenesis) and androgens (testosterone) at the time of puberty.

Efferent tubules

Septum

Septa of

testis

Epididymis
Long narrow
closely coiled
tubule lying
along the
inner side of
each testis.
It stores
sperms
as well as
secretes fluid
supposed to
nourish the
sperms.

Rete

testis

Testicular veins

Testicular artery

Vas deferens

Coverings of testis

Spermatic cord Seminiferous tubule

One to three highly coiled tubules are present in

each testicular lobule of testis

Testicular lobules

Each testis has about 250 compartments known

as testicular lobules

Tunica vasculosa

Comprises of a network of capillaries supported

by delicate connective tissue, lining the tunica

albuginea

Tunica vaginalis

Outer covering of testis

Tunica albuginea

White fibrous capsule enveloping each testis and

produces lobules by partitions into its interior

Cauda epididymis

Posterior end of epididymis

Corpus epididymis

Middle part of epididymis

Caput epididymis

Anterior end of epididymis,

into which vasa efferentia

open

T.S. of

seminiferous tubule

Fig.: Section of seminiferous

tubules showing its cells

at various stages

Cytoplasmic

bridges

Basal lamina

Fibroblast

Meiosis

Capillary

Early spermatids

The second maturation division of secondary

spermatocytes forms four haploid spermatids.

Secondary spermatocytes

Late spermatid

Early spermatids net

transformed into sperms by

spermiogenesis.

Interstitial cells or Leydig’s cells

Endocrine cells present in the connective

tissue which secrete androgens, i.e.,

testosterone.

Primary spermatocytes

Spermatogonia actively grow into larger cells called

primary spermatocytes by absorbing nutrition from

Sertoli cells. These undergo meiotic divisions.

Spermatogonium

The undifferentiated germ cells undergo mitosis to

form diploid spermatogonia or sperm mother cells.

Some act as stem cells and keep on adding new cells.

Sertoli cell

Large, elongated pyramidal cells called nurse or

sustentacular cells. Bases of these cells adhere to

basal lamina and apices project into lumen. Support

developing germ cells and provide them with

nutrition. They secrete androgen binding protein

(ABP) that concentrates testosterone in seminiferous

tubules and inhibin that suppresses FSH synthesis.

Sertoli

cell

Spermatozoa

After spermiogenesis, the head of

sperms become embedded in Sertoli

cells, before being finally released

from seminiferous tubules.

Fig.: L.S. of testis and accessory ducts