Question

The membrane investing the ovum just outside the membrane granulosa is
A. Zona pellucida
B. Theca Interna
C. Vitelline membrane
D. Discus proligerus

Answer 1

Oogenesis takes place in the ovaries. Granulosa cells are the primary cell in the ovary that provides the physical support and microenvironment required for the developing embryo.

Complete answer:

The ovum is enclosed by two additional egg coats: inner thin, transparent, noncellular zona pellucida, and outer thick radiata.

Zona pellucida is secreted by the ovum itself and is thus a primary egg membrane.

The membrane granulosa cells surrounding the follicular fluid are covered by two membranes called theca interna and theca externa.

So, the correct answer is “Option B”.

Additional Information:

The ovum is a rounded, non motile cell.

1. It is much larger (0.1mm) than most body cells (under 0.01mm ) of the parents.

It is almost free of yolk and is said to be alecthical.

2. It has abundant cytoplasm called ooplasm, having a large nucleus termed a germinal vesicle, with a prominent nucleolus, at the center and surrounded by a plasma membrane, also called oolema.

3. The latter gives off microvilli to absorb food materials from the follicular cells during growth.

4. Tiny vesicles, called cortical granules, lie just under the egg’s plasma membrane.

There is no centriole in the ovum.

5. The ovum shows polarity. Its side which extrudes polar bodies is called the animal pole.

The opposite side is termed as an animal pole.

Note: Granulosa cells can also have a different name depending upon the location within the ovarian follicles-membrane granulosa also called mural granulosa cells forming the layer within the follicle antral wall; discus proligerus can refer to the attachment between cumulus oophorus and membrane granulose, and mural granulosa that line the follicular wall.