Histological Structure of Human Ovary

    The ovaries are solid and composed of connective tissue called stroma

    It shows following elements.

a)    Germinal epithelium:

    i) The surface of the ovary is covered with surface epithelium. It is simple epithelium called germinal epithelium.

    ii) It changes from squamous to cuboidal with age.

    ii) It is further covered by visceral peritoneum.

    iv) It is parent tissue which proliferates thousands of primordial follicles in embryonic condition.

b)    Tunica albuginea:

    i) Beneath the germinal epithelium a layer of connective tissue is present called Tunica albuginea.

    ii) Stroma consists of central ovarian medulla and ovarian cortex.

    iii) Cortex is region where development of oocytes take place.

    iv) Primordial follicle is also called egg nest which changes into primary follicle.

c)    Primary follicle or primary oocyte:

    i) It is lined by single layer of epithelium cell called follicular cells.

    ii) Primary oocyte only at the time of puberty.

d)    Developing follicle / secondary follicle:

    i) These are also called growing follicle.

    ii) It is lined by double layer of follicular cells.

e)    Graafian follicles:

1)   It is matured follicle in which ovum is present in secondary oocyte stage.

2)  It is eccentric,

3)  Matured follicle in mammal is known as Graafian follicles as it is discovered by Dutch scientist Regnier de Graaf.

4)  A Graafian follicle measures about 10 - 20 mm in diameter.

5)  It contains mature oocyte or ovum with a diameter of 120.

6)  Around the ovum there is few layers of cells called Cumulus oophorous or cumulus ovaricus. It is also called discus oophorous, discus ovigerous, and discus proligerous.

7)  Ovum itself is externally covered by thin vitelline membrane.

8)  Non-cellular layer is zona pellucida and outer cellular layer is corona radiata.

9)  Zona pellucida: The ovum is surrounded by the thick hyaline transparent glucoprotein layer called Zona pellucida.

10)               It is performed membrane.

11)  Zona pellucida develops as a jelly coat around the primary oocyte & is surrounded by the granulosa cells.

12)               The corona radiata is a well-defined radially arranged layer of columnar cells, immediately surrounding the zona pellucida.

13)               Antrum: A mature follicle inside contains a cavity called antrum. Antrum is filled is filled by fluid called liquor folliculi or antral folliculi.

14)               It is viscous fluid that is rich in steroid reproductive hormones particularly estrogens.

15)               Theca externa and theca interna: Membrana granulosa is surrounded by outer layer called theca externa and inner layer is called theca interna.

    Thus the follicle has 3 distinct layers:

    a) Outer theca externa: (epithelial cells with connective tissue)

   b) Middle theca externa: (fibrous s& highly vascularized)

    c) Inner - Membrana granulosa: (multilayered granular)

1)   Germ hill is the region where ovum with cumulus oophorous is present and it helps to keep the ovum within antrum.

2)  Theca interna secretes a hormone called estrogen.

3)  Estrogen controls secondary sexual characters in female.

4)  It stimulates secretion of LH, due to LH amount of liquor follicles in antrum increases.

5)  Mature follicles moves towards the surface of ovary and burst to release ovum, this is called ovulation.

6)  The spot on the ovarian surface where Graafian follicle rupture for ovulation is called stigma.

7)  After ovulation empty follicle changes into corpus luteum by luteinisation of granulosa cells.

8)  Corpus luteum:

    i. It is yellowish colour temporary endocrine gland. It is also yellow body.

    ii. It absorbs yellowish lutein pigment.

    iii. It secretes hormones progesterone which maintain endometrium and pregnancy

    iv. If the egg is not fertilized corpus luteum degenerates into corpus albicans (corpus - body, albicans - white)

f) Medulla:

    The central part of ovary is called medulla. It is formed of fibrous connective tissue, blood vessels and nerves.

        Degenerative process of follicles or egg in ovary is called Atresia.