Snigdha Goswami

Immunology is all about our body's mechanism of protection from the harmful pathogens present outside our body in the environment. There are different levels of Defence for protection in our body. The first level of protection that the pathogens coming towards our body faces is called first line of Defence. ( Microbes = any micro-organism both harmful and harmless to human  Pathogen = micro-organism that can cause disease) From where pathogens can enter our body : 1. Skin  : skin covers the internal organs of our body .It is the largest organ covering the most area of our body externally. 2. ear  : hole of the ear is an entrance into the body. 3. Eye: eyes are not covered by the skin and exposed to the environment facing direct contact with pathogens 4. nose:  nostril is an entrance to the Airways which leads towards the internal organ lungs 5. Mouth:  mouth hole is the entrance to the body mainly to the gastrointestinal tract 6. Anus

This is the written form of the video on youtube  Ovarian follicles during oogenesis  . Watch the video for better understanding.  click here Development of oocyte inside ovary:  1. on the over wall the germinal epithelial cells develop into oogonium cells by mitotic cell division. It occurs before the birth of the female. 2. In puberty the oogonium develops into oocyte that is primary oocyte which gets surrounded by follicular cells in the ovary at first it gets surrounded by single layer of follicular cells . at this stage it is called primordial follicle  . 3. now more layers of follicular cells develop surrounding the oocyte .These developing follicles are called growing follicle.   4. Now the follicular cells form an antrum or cavity in between the cells and with this antrum the follicle is called the antral follicle. 5. the antral follicle develops into the most mature follicle that is Graafia