NEET Biology Human Reproduction MCQs Set 14

Answer: (a) 6-13 days

Explanation:
1. 6-13 days.
2. Menstrual cycle

Answer: (d) Progesterone

Explanation:
1. Menstruation is caused by the reduction of oestrogen and progesterone, especially progesterone at the end of monthly ovarian cycle.

Answer: (d) A- antrum, B- secondary follicle, C-tertiary follicle

Explanation:
1. A- Antrum, B- Secondary follicle, C-Tertiary follicle

Answer: (b) LH

Explanation:
1. In a 28 day menstrual cycle, the menses takes place. For 3-5 days, the production of LH from the anterior lobe of the pituitary gland considerably reduced. The withdrawal of this hormone causes degeneration of the corpus luteum and therefore, progesterone production is reduced.
2. Production of oestrogen also reduced in this phase (menstrual). The endometrium of the uterus breaks down and menstruation begins. The cells of endometrium secretions and the unfertilized ovum constitute the menstrual flow

Answer: (c) Foetus and uterine wall

Explanation:
1. Placentation is a connection between foetus and uterine wall.
2. Gametes. The major reproductive events in human beings are as follows
3. (i) Gametogenesis It is the formation of gametes. It includes spermatogenesis (formation of sperms) and oogenesis (formation of ova/eggs)
4. (ii) Insemination It is the transfer of sperms by the male into the genital tract of the female
5. (iii) Fertilization Fusion of male and female gametes to form zygote is called fertilization
6. (iv) Cleavage It is rapid mitotic divisions of the zygote which convert the single celled zygote into a multicellular structure called blastocyst (blastula)
7. (v) Implantation It is the attachment of blastocyst to the uterine wall
8. (vi) Placentation It involves the formation of placenta which is the intimate connection between the foetus and uterine wall of the mother to exchange the materials
9. (vii) Gastrulation It is the process by which blastocyst is changed into gastrula with three primary germ layers
10. (viii) Organogenesis It is the formation of specific tissue, organs and organ systems from three primary germ layers
11. (ix) Parturition (child birth) it involves expelling of the baby from the mother’s womb (uterus)

Answer: (a) Blastula

Explanation:
1. Embryologist can draw the fate maps of future organ of embryo in blastula stage using natural colour patten or vital dyes to show the fate of various germ layers.

Answer: (b) A-Amnion; B-Amniotic cavity

Explanation:
1. A-Amnion; B-Amniotic cavity

Answer: (a) Oral contraceptive for females

Explanation:
1. Saheli is a new oral contraceptive for the females. It contains a non-steroidal preparation. It is once a weeks’ pill with very low side effects and high contraceptive value.

Answer: (a) Centrolecithal

Explanation:
1. In centrolecithal eggs, the yolk is surrounded by cytoplasm, e.g., eggs of insects.

Answer: (d) Menarche

Explanation:
1. Menarche is the starting of menstruation in girl at about 13 year of age, whereas menopause is the period of life, when menstruation naturally stops.

Answer: (c) Holoblastic

Explanation:
1. Holoblastic cleavage is complete division of zygote, e.g., frog.

Answer: (d) Both (b) and (c)

Explanation:
1. Nucleus of ovum is called female pronucleus.
2. Capacitation takes about 5-6 hours.
3. Capacitation of Sperm The sperms in the female is genital tract are made capable of fertilizing the egg by the secretion of female genital tract. These secretions of the female genital tract removes the coating substances deposited on the surface of the sperms, particularly those on acrosome. Thus, the receptor sites on the acrosome are exposed and sperm become active to penetrate the egg. This phenomenon of sperm activation in mammals is called capacitation. It takes about 5-6 hr for capacitation of sperm

Answer: (b) Anti-fertilizin and sperm lysin

Explanation:
1. At the time of fertilization, the sperm secretes sperm lysin and anti-fertilizin.

Answer: (d) Count of less than 20 million/mL semen

Explanation:
1. One time of ejaculation contains about 200 to 300 million sperms. If the sperm become less than 20 million then, it causes infertility

Answer: (c) Oxytocin

Explanation:
1. Oxytocin hormone is secreted by posterior pituitary gland. It helps in ejection of milk from mother’s breasts, when the baby is sucking.

Answer: (a) Labia minora

Explanation:
1. In the given options, only labia minora belongs to the external genitalia of females

Answer: (c) Of endometrium wall

Explanation:
1. Progesterone hormone is the main hormone, which maintains the endometrium wall.
2. Generally, menstrual cycle have four phases
3. (i) Menstrual phase (a) The soft tissue of endometrial lining of the uterus disintegrates causing bleeding.
4. (b) The unfertilized egg and soft tissue are discharged.
5. (c) It lasts 3-5 days.
6. (ii) Follicular Phase/Proliferative Phase (a) The primary follicles in the ovary grow and become a fully mature Graafian follicle.
7. (b) The endometrium of the uterus is regenerated due to the secretion of LH and FSH from anterior pituitary and ovarian hormone, estrogen.
8. (c) It least for about 10-14 days.
9. (iii) Ovulatory Phase (a) Rapid secretion of LH (LH surge) induces rupture of Graafian follicle, thereby leading to ovulation (release of ovum).
10. (b) It lasts for only about 48 hr.
11. (iv) Luteal Phase/Secretor Phase (a) In this phase the ruptured follicle changes into corpus luteum in the ovary and it begins to secrete the hormone progesterone.
12. (b) The endometrium thickens further and their glands secrete a fluid into the uterus.
13. c) If ovum is not fertilized, the corpus luteum undergoes degeneration and this causes disintegration of the endometrium leading to menstruation

Answer: (d) They provide nutrition to developing sperm; they direct morphogenesis of sperm

Explanation:
1. The wall of each seminiferous tubule of testicular lobule is formed of a single layered germinal epithelium. Large pyremidal Sertoli’s cells secrete androgen binding protein that concentrates testosterone in the seminiferous tubule. These cells nourish the developing sperms.

Answer: (a) Head

Explanation:
1. A typical mammalian sperm is flagellated consisting of four pats namely head, neck, middle piece and tail. During fertilization, whole of sperm enters into an ovum but tail is left outside.

Answer: (c) Mitochondria

Explanation:
1. Usually, the cytoplasm of ova is without centrioles, because during the second maturation division, the centrioles are taken away by the second polar body.

Answer: (a) Child birth

Explanation:
1. Parturition
2. (i) The average duration of human pregnancy is about 9 months which is called the gestation period
3. (ii) The act of expelling the full term foetus from the mother’s uterus at the end of gestation period is called parturition
4. (iii) It is induced by a complex neuroendocrine mechanism
5. (iv) Parturition signals originates from the fully developed foetus and the palcenta, which induce mild uterine contractions called foetus ejection reflex
6. (v) This triggers the release of oxytocin from the maternal pituitary
7. (vi) Oxytocin induces stronger uterine muscle contractions
8. (vii) Relaxin increases the flexibility of the pubic symphysis and ligaments that helps to dilate the uterine cervix during labour pain
9. (viii) This leads to the expulsion of baby

Answer: (c) Oestrogen

Explanation:
1. Oestrogen is secreted by the cells of Graafin follicles. It is the principal feminizing hormone responsible for the development of secondary sexual characters and female reproductive organs.

Answer: (b) Trophoblast

Explanation:
1. Trophoectoderm (trophoblast).
2. It is the outer most layer of the cells of blastocyst. It forms the foetal part of placenta and do not form any part of the embryo proper

Answer: (a) Error catastrophe

Explanation:
1. According to the theory of error catastrophe, the damage to mechanisms that synthesize proteins, results in faulty proteins, which accumulate to a level and causes catastrophic damage to cells, tissues and organs.

Answer: (c) Secondary spermatocytes

Explanation:
1. Secondary spermatocytes are haploid as these are formed after meiosis-I (reductional division).