what is the function of antrum in the grafian follicle?

The antrum is the cavity around the ova which develops later in the development of the graafian follicle. It is the combination of blood plasma and secretory product of granulosa and theca cell.

Following are its functions:
(1) It provides microenvironment specific for the the development of the oocyte. 
(2) It has many female hormone like estradiol, progesterone and nutrients essential for the development of the oocyte.
(3) It provides the required osmolarity for the oocyte development.
(4) When graafian follicle mature and release oocyte, it is the fluid in the antrum which take it to the fallopian tube.