Individual testicle, responsible for some
endocrine activity, and responsible for generating
spermatozoa. Analogous to the
ovary in the female, there are two of these in the adult human male, suspended outside the body in a wrinkled sac of skin, the
scrotum, which can contract to bring the
testes closer to the body in cold or dangerous conditions. Plural
testes.
A testis requires a lower temperature than normal body temperature in order to produce healthy
sperm; thus, it is suspended outside the body in the
scrotum. During embryonic development, the testes are found inside the
abdominal cavity of the embryo, later
descending into the
scrotum before birth. In some males, one or both
testes may fail to descend; a condition known as
cryptorchidism or
ectopic testis. Such
undescended testes become
sterile if not artificially placed in the
scrotum; they also tend to become
cancerous.
In certain individuals, one or both
testes may be capable of ascending into the
abdominal cavity under pressure or in times of stress.
Mainly composed of about 250 compartments (the
lobuli testes), each containing from 1 to 3
seminiferous tubules. While mostly separate, the tubules in adjacent lobules may occasionally intercommunicate. The lobules converge on the
mediastinum, where they each produce a small tubule, the
caniculari recti which then terminate in the
rete testis. The testes are suspended in the
scrotum by the
spermatic cords.
The testis is enclosed by a thick, firm, white membrane, the
albuginea testis, which projects into the testis to form the
mediastinum testis. There is an additional membrane covering the
albuginea testis, termed the
tunica vaginalis propria; these two membranes are separated by a thin cavity, termed the
cavitas serosa. Covering the whole of the testis and the epididymis is the
tunica vaginalis communis.