Question

Thick/ follicular cells surrounding oocyte in graafian follicle belong to
(a)Zona pellucida
(b)Corona radiata
(c)Membrane granulosa
(d)None of these

Answer 1

Hint: The layer of several columnar cells which send processes into zona pellucida giving nutrition to the oocyte. These cells are made from granulosa cells. These cells and along with oocytes are attached to the side of the follicle within a larger mass of granulosa cells called the cumulus oophorus.

Complete answer:
Graafian follicle is characterized by a large follicular antrum that makes up most of the follicle. The primary oocyte begins to grow and surrounding follicular cells change from flat to cuboidal and proliferate to produce a stratified epithelium of granulosa cells and the unit is called primary follicle. The secondary oocyte, having undergone the first meiotic division, is found eccentrically. It is surrounded by the zona pellucida and a layer of several cells termed as the corona radiata. When ovum released from the Graafian follicle and into the oviduct, the ovum will contain three layers: oocyte, zona pellucida and corona radiata.

Additional Information:
The Ovary:
-The human ovary consists of an inner medulla and outer cortex with characteristic boundaries.
-The medulla contains the blood vessels and nerves, while the cortex consists of developing follicles.
-A cross-section of an ovary will show follicles in various stages of development.
Primary oocyte:
-This is spherical in shape, about 30 micrometer in diameter.
-It has a large vesicular rounded and eccentric nucleus with large nucleolus.
-It’s cytoplasm is pale acidophilic in nature and the organelles tend to gather close to the nucleus.
-It doubles its size and becomes surrounded by an acidophilic membrane called zona pellucida which is glycoprotein in nature produced by both the oocyte and follicular cells.
Graafian follicle:
-The Graafian follicle is the stage after the first meiotic division has completed but before the ovulation stage.
-The secondary oocyte, having undergone the first meiotic division, is located eccentrically, 120 micrometer, containing 23d-chromosomes.
-It is surrounded by the zona pellucida and a layer of several columnar cells known as the corona radiata which send processes into the zona pellucida giving nutrition to the oocyte.
-The theca folliculi differentiated into: - theca interna: cellular, vascular and secrete estrogen - theca externa: fibrous and less vascular.
Ovulation:
-When the follicular fluid is markedly increased it ruptures and releases the 2ry oocyte on the surface of the ovary.
-The ovum will consist of three structures which are oocyte, zona pellucida and corona radiata.
Corpus luteum:
-After release of the ovum, the remaining cells of the granulosa and theca interna which form the corpus luteum.
-The center contains the remains of the blood clot that formed after ovulation.
-Surrounding the clot are granulosa lutein cells that have an appearance characteristic of steroid-producing cells, with pale cytoplasm.
-These cells produce progesterone and to a lesser extent cholesterol.
Corpus Albicans:
-If fertilization doesn’t occur, the cells of the corpus luteum remain active for roughly 14 days until the levels of LH fall and the corpus luteum involutes to form the corpus albicans.
-The secretory cells of the corpus luteum degenerate, and are phagocytosed by macrophages and replaced by fibrous material.

So, the correct answer is, ‘corona radiata.’

Note: -The follicular cells proliferate to form many layers and they begin to secrete follicular fluid which accumulates in multiple spaces.
-These spaces join together to form a single cavity called antrum which divides the follicular cells into:
Cumulus oophorus: Which surrounds the oocyte, and connects it to one side of the follicle.
Granulosa cells: They line the cavity, which is polygonal in shape with pale acidophilic cytoplasm and central rounded nuclei. They secrete estrogen hormone.
-Theca folliculi is a capsule result from condensation of stroma around the follicles - later they differentiate into theca interna and theca externa.