This set of Class 12 Biology Chapter 3 Multiple Choice Questions & Answers (MCQs) focuses on “Human Reproduction – Structure of an Ovary”.
1. What cells, along with primary oocyte, make a primary follicle?
a) Granulosa cells
b) Sertoli cells
c) Secondary oocytes
Explanation: Oogonium initiates the first round of meiosis but ends up getting arrested at Prophase I resulting in primary oocytes. These primary oocytes are then enveloped by a single layer of granulosa cells, thus forming a primary follicle.
2. The number of primary follicles at birth and puberty is the same.
Explanation: Primary follicles are formed as a result of enveloping of primary oocytes by a layer of granulosa cells. These are formed during embryonic development and undergo a process of degeneration as the female matures to puberty. Hence the number of primary follicles that survive to puberty is far less, reaching only about 60,000-80,000 in each ovary.
3. In addition to granulosa cells, what additional component is added to a primary follicle to transform it into a secondary follicle?
d) Secondary oocyte
Explanation: Upon undergoing meiosis, the primary follicle is formed from the oogonium. These follicles are then surrounded by a protective coating of the theca, which supports further development and division of primary oocyte. This stage of the follicle is called the secondary follicle.
4. The distinguishing characteristic of a tertiary follicle is a fluid-filled cavity called ________
c) Zona pellucida
Explanation: Primary follicle is formed by the primary oocyte arrested at Prophase I and enveloped by a layer of granulosa cells. These are then enveloped by a theca resulting in a secondary follicle, which further undergoes development resulting in the formation of a fluid-filled cavity called the antrum. This mature follicle is a tertiary follicle.
5. The first round of meiosis of oogonium is completed in which follicle?
a) Graafian follicle
b) Primary follicle
c) Secondary follicle
d) Tertiary follicle
Explanation: The oogonium starts meiosis but is arrested at Prophase I, thereby forming primary oocyte. This oocyte then forms a primary, then secondary, and finally a tertiary follicle with the addition of granulosa cells, theca and antrum. This stage of follicle promotes further division of primary oocyte. Thus the first division of meiosis is completed in the tertiary follicle.
6. The mature follicle that holds the secondary oocyte before release from the ovary is called _________
a) graafian follicle
b) primary follicle
c) secondary follicle
d) tertiary follicle
Explanation: Primary oocyte completes the first round of meiosis in the tertiary oocyte, thus forming a secondary oocyte. The tertiary follicle further matures to form a Graafian follicle which ruptures and releases the secondary oocyte in the fallopian tube for fertilization.
7. What are the white remains of the Graafian follicle left after its rupture called?
a) Corpus luteum
b) Corpus callosum
c) Corpus delicti
d) Corpus handi
Explanation: The Graafian follicle ruptures to release the egg into the fallopian tube. The ruptured Graafian follicle results in the filling of its lumen with theca and granulosa cells, which pigment it white. This degrading follicle is hence called corpus luteum, which is then transformed into corpus albicans.
8. The ovarian stroma is composed of which two components?
a) External cortex and internal medulla
b) External medulla and internal cortex
c) External epithelium and internal medulla
d) External epithelium and internal cortex
Explanation: An envelope of epithelial tissue covers the ovarian stroma. The stroma is composed of two distinct parts. The outer part called cortex is composed of follicles and oocytes. The internal part is called the medulla and is composed of blood vessels, lymphatic ducts, and nerves.
9. Which of the following is not the function of the ovary?
a) Release the female gamete for fertilization
b) Produce female sex hormones
c) Provide a hostile environment for the development of the embryo
d) Protection and development of the egg
Explanation: The ovary is the place where the oocyte is developed from the oogonia. It houses follicles that nourish and protect eggs before they are released in the process of ovulation for fertilization. It also produces sex hormones like estrogen, which are essential for the development of secondary sexual characteristics in females. It does not hold the developing embryo. The embryo is held in the uterus.
10. Onkar was attending a Biology exam where the teacher drew a diagram of an ovary with numerous follicles. Onkar was able to identify the following four follicles in the ovary. Which of the mentioned follicles by him is incorrect?
a) Primary follicle
b) Secondary follicle
c) Tertiary follicle
d) Hair follicle
Explanation: Ovary has four different types of follicles, namely: Primary follicle, secondary follicle, tertiary follicle, and Graafian follicle. Hair follicles are present beneath the epithelium under the skin.
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