Biology Today — May 2017

• Lactation (milk secretion and ejection) is the main function of mammary glands.

• During pregnancy, mammary glands grow under the influence of hormones estrogen and progesterone. At the time of
infant’s birth, the hormone prolactin stimulates the production of milk and the hormone oxytocin causes release of milk as
the infant sucks the breast.

Functions of Female Reproductive System

Ovaries

•    Production and secretion

of female sex hormones.

•    Germinal epithelial cells

of ovary produce ova by

oogenesis.

Fallopian tubes

•    Convey the ovum from

the ovary to the uterus by

peristalsis.

•    These are sites of fertilisation,

i.e., fusion of gametes in

ampullary isthmic junction.

Uterus

•    If fertilisation takes place, then the embryo

gets attached to the uterine wall which

protects and nourishes the developing fetus,

i.e., implantation.

•    It is involved in uterine movements and also

goes through menstrual cycle, after puberty.

Vagina

•    It provides a passage

for the menstrual flow

and receives sperms

during intercourse.

•    It also acts as a birth

canal during labour.

•    General build up – less muscular

•    Hair growth – shows axillary hair growth and

development of pubic hair

•    Mammary glands – well developed

•    Skin – less hairy and coarse

•    Voice – high pitched

•    Breathing – predominantly thoracic

•    Shoulders – are not so broad as compared to

men

•    Shape – attains feminine shape, i.e.,

widening of pelvis, deposition of

fat in thighs, buttocks and face

Secondary Sexual Characteristics in Female

OOGENESIS

• The process of formation of a mature female gamete (ovum) is called oogenesis. It occurs in ovaries and involves three
phases-mutliplication, growth and maturation.

• At birth, ovaries contain approx. 2 to 4 million oogonia (egg mother cells). No more oogonia are formed and added after birth.

• During fetal life, all the oogonia develop into primary oocytes. Then they undergo a first meiotic division by replicating their
DNA, however, they do not complete the division in the fetus. Accordingly, all the primary oocytes present at birth are said
to be in a state of meiotic arrest containing 46 chromosomes, each with two sister chromatids.

• The first polar body may divide to form two second polar bodies. They did not play any role in reproduction and soon
degenerate due to lack of cytoplasm and food.

• The actual female gamete is ovum. From one oogonium, one ovum and three polar bodies are formed.

• The steps in oogenesis can be illustrated as:-