As you are aware, humans are sexually reproducing and
viviparous. The reproductive events in humans include
formation of gametes (gametogenesis), i.e., sperms in males
and ovum in females, transfer of sperms into the female
genital tract (insemination) and fusion of male and female
gametes (fertilisation) leading to formation of zygote. This
is followed by formation and development of blastocyst
and its attachment to the uterine wall (implantation),
embryonic development (gestation) and delivery of the
baby (parturition). You have learnt that these reproductive
events occur after puberty. There are remarkable
differences between the reproductive events in the male
and in the female, for example, sperm formation continues
even in old men, but formation of ovum ceases in women
around the age of fifty years. Let us examine the male and
female reproductive systems in human.
3.1 THE MALE REPRODUCTIVE SYSTEM
The male reproductive system is located in the pelvis region
(Figure 3.1a). It includes a pair of testes alongwith
accessory ducts, glands and the external genitalia.
CHAPTER 3
HUMAN REPRODUCTION
3.1 The Male Reproductive
System
3.2 The Female Reproductive
System
3.3 Gametogenesis
3.4 Menstrual Cycle
3.5 Fertilisation and
Implantation
3.6 Pregnancy and
Embryonic Development
3.7 Parturition and Lactation
2020-21
The testes are situated outside the
abdominal cavity within a pouch
called scrotum. The scrotum helps
in maintaining the low temperature
of the testes (2–2.5
o
C lower than
the normal internal body
temperature) necessary for
spermatogenesis. In adults, each
testis is oval in shape, with a length
of about 4 to 5 cm and a width of
about 2 to 3 cm. The testis is
covered by a dense covering. Each
testis has about 250 compartments
called testicular lobules
(Figure 3.1b).
Each lobule contains one to
three highly coiled seminiferous
tubules in which sperms are
produced. Each seminiferous tubule
is lined on its inside by two types
of cells called male germ cells
(spermatogonia) and Sertoli cells
(Figure 3.2 ). The male germ cells
undergo meiotic divisions finally
leading to sperm formation, while
Sertoli cells provide nutrition to the
germ cells. The regions outside the
seminiferous tubules called
interstitial spaces, contain small
blood vessels and interstitial cells
or Leydig cells (Figure 3.2). Leydig
cells synthesise and secrete
testicular hormones called
androgens. Other immunologically
competent cells are also present.
The male sex accessory ducts include rete testis, vasa efferentia,
epididymis and vas deferens (Figure 3.1b). The seminiferous tubules of
the testis open into the vasa efferentia through rete testis. The vasa efferentia
leave the testis and open into epididymis located along the posterior surface
of each testis. The epididymis leads to vas deferens that ascends to the
abdomen and loops over the urinary bladder. It receives a duct from seminal
vesicle and opens into urethra as the ejaculatory duct (Figure 3.1a). These
ducts store and transport the sperms from the testis to the outside through
urethra. The urethra originates from the urinary bladder and extends
through the penis to its external opening called urethral meatus.
Figure 3.1(a) Diagrammatic sectional view of male pelvis
showing reproductive system
Figure 3.1(b) Diagrammatic view of male reproductive system
(part of testis is open to show inner details)
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HUMAN REPRODUCTION
2020-21