The zygote passes through several developmental stages till implantation. Describe each stage briefly with suitable diagrams.
The zygote passes through the following stages till implantations
(i) The embryo with 8-16 blastomeres is called a morula.
(ii) The morula continues to divide and transforms into blastocyst as it moves further into uterus.
(iii) The blastomeres in the blastocyst are arranged into a surface layer called trophoblast and a cluster of interior cells attached to trophoblast are called the inner cell mass.
(iv) The trophoblast layer then gets attached to the endometrium and inner mass cells get differentiated as embryo.
(v) After attachment, the uterine cells divide rapidly to cover the blastocyst.
(vi) The blastocyst becomes embedded in the uterine endometrium. This is called implantation.
$$ \text { Transport of ovum, fertilisation and passage of growing embryo through Fallopian tube } $$
Draw a neat diagram of the female reproductive system and label the parts associated with the following (a) production of gamete, (b) site of fertilisation (c) site of implantation and (d) birth canal.
The female reproductive system consists of a pair of ovaries along with a pair of oviducts, uterus, cervix, vagina and the external genitalia located in pelvic region.
These parts are integrated structurally and functionally to support the processes of ovulation, fertilisation, pregnancy and birth.
Diagrammatic sectional view of the female reproductive system
Labels
(i) Ovary (production of gamete)
(ii) Isthmus-ampullary junction(site of fertilisation)
(iii) Uterine endometrium (site of implantation)
(iv) Cervix and vagina (birth canal)
With a suitable diagram, describe the organisation of mammary gland.
The description of mammary gland is as follows
(i) The mammary glands are paired structures (breasts) that contain undeveloped duct system and adipose tissue (fat containing cells).
(ii) During pregnancy, in response to oestrogen and progesterone, a glandular system develops for milk production.
(iii) Glandular tissue of each breast develops mammary lobes containing clusters of cells called alveoli.
(iv) The cells of alveoli secrete milk, which is stored in the cavities (lumens) of alveoli
(v) The alveoli open into mammary tubules. The tubules of each lobe join to form a mammary duct.
(vi) Several mammary ducts join to form a wider mammary ampulla which is connected to lactiferous duct through which milk is sucked out by the baby.
$$ \text { A diagrammatic sectional view of mammary gland } $$