NEET Biology Human Reproduction MCQs Set 09

Answer: (b) Seminal vesicles

Explanation:
1. Seminal vesicle secretes seminal fluid containing fructose and prostaglandins. Polar bodies are formed by meiosis-I and meiosis-II before and after fertilisation respectively. Polar bodies serves both as dumping ground for extra sets of chromosomes and ensures that the ovum will have most of the cytoplasm

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

Explanation:
1. Hormonal level during menstrual cycle
2. 1-5 days (menstrual phase) Level of progesterone and LH decreases.
3. 6-13 days (follicular or proliferative phase) FSH and LH level increases that also stimulates the level of oestrogen.
4. 14 days (ovulatory phase) Both LH and FSH attains a peak level.
5. 15-20 days (secretory phase) Level of progesterone increase

Answer: (a) 32-celled stage

Explanation:
1. Zygote is implanted in human female at 32-celled stage because fertilized egg in human are not divide beyond 32-celled stage in natural zygote.

Answer: (a) Nucleus and acrosome

Explanation:
1. Nucleus and acrosome.
2. Structure of a sperm (spermatozoa) It consists of four parts i.e., Head, Neck, Middle piece and tail, enveloped by a plasma membrane.
3. Head It is the enlarged end of a sperm, containing the large haploid nucleus, i.e., condensed chromatin body and is capped by acrosome. The acrosome contains hydrolytic enzymes that help in dissolving membranes of the ovum for fertilization.
4. Neck It contains proximal centriole which is necessary for the first cleavage division of zygote and the distal centriole that is connected to the tail filament.
5. Middle piece It contains a number of mitochondria that provide energy for the movement of the tail that facilitate sperm motility essential or fertilization.
6. Tail It consists of axial filaments surrounded by the plasma membrane. It helps the sperms to swim in a fluid medium

Answer: (b) Postnatal

Explanation:
1. Postnatal.
2. Development periods It includes embryonic or prenatal and post embryonic or postnatal (natal concerning birth)
3. (i) Embryonic period (prenatal period) In human beings is passed in mother’s womb (uterus). It includes the events from the formation of an embryo till the time of birth
4. (ii) Post embryonic period (postnatal period). This period is passed outside the mother’s womb. It includes events from birth to the death

Answer: (c) A-spermatogenesis, B-spermatogonia, C-mitosis

Explanation:
1. A-Spermatogenesis, B-Spermatogonia, C-Mitosis

Answer: (c) Ejaculatory duct

Explanation:
1. The vas deferens loops over urinary bladder, where it is joined by duct from seminal vesicle to form ejaculatory duct. Vasa deferentia carry sperms

Answer: (a) Vasopressin

Explanation:
1. Oxytocin hormone is secreted from neurohypophysis of pituitary. It stimulates the contraction of the smooth muscles of uterus inducing labour pain for child birth.

Answer: (a) Towards the end of pregnancy

Explanation:
1. Lactation is, produring milk towards the end of pregnancy

Answer: (a) Testosterone

Explanation:
1. Testosterone.
2. Region outside the seminiferous tubules is called interdigital space, which is lined by interstitial cells also called Leydig cells. Leydig cells secretes testosterone and also called endocrine part of the testis

Answer: (b) Fusion of sperm and ova

Explanation:
1. Fusion of sperm and ova
2. Fertilization
3. The process of fusion of a sperm (male gamete) with an ovum (female gamete) is called fertilization
4. Steps
5. (i) During coitus, semen is released by the penis into the vagina (insemination)
6. (ii) The motile sperms swim rapidly through the cervix, enter into the uterus and reach the ampullary isthmic junction of the oviduct (site of fertilization)
7. (iii) A sperm comes in contact with the zona pellucida layer of the ovum and induces changes in the membrane to block the entry of additional sperms
8. (iv) The enzymes of the acrosome of sperm help to dissolve zona pellucida and plasma membrane of the ovum and sperm head is allowed to enter into the cytoplasm of the ovum, i.e., secondary oocyte
9. (v) Ultimately diploid zygote is produced by the fusion of a sperm and an ovum

Answer: (b) Womb

Explanation:
1. In uterus the development of foetus takes place and this development lasts till parturition. Generally, in common language uterus is called womb

Answer: (b) Low oestrogen production

Explanation:
1. During ovulation the oestrogen level do not remain the low.
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.
14. (d) Oestrogen and progesterone levels rise during this phase. It lasts for only 1 day. (e) During pregnancy all events of the menstrual cycle stop and there is no menstruation. The menstrual cycle permanently stops in females at the age of around 50 years. This is called menopause

Answer: (c) Human – Mesolecithal, centrolecithal

Explanation:
1. In isolecithal eggs, yolk is uniformly distributed (e.g., mammals). In centrolecithal eggs, yolk is in the centre of the egg (e.g., insects). In polyleithal eggs, yolk is in patches, (e.g., insects) and in telolecithal eggs, yolk is concentrated at one of the egg (e.g., frog, birds). Eggs of human being are microlecithal and isolecithal.

Answer: (c) Reduction in oestrogen and progesterone

Explanation:
1. The corpus luteum plays an important role in the preparation of endometrium for the implantation of fertilized egg by secreting oestrogen and progesterone hormones. But if the egg is not fertilized then the corpus luteum begins to degenerate and it stops the production of progesterone and oestrogen hormones, which causes shedding of the endometrium lining menstrual bleeding.

Answer: (d) All of the above

Explanation:
1. As a result of gastrulation, ectoderm, mesoderm and endoderm are formed.

Answer: (b) Spermiation

Explanation:
1. Spermiation.
2. The transformation of spermatids into spermatozoa is called spermiogenesis or spermateliosis. The spermatids are later on known as sperms. After spermiogenesis head becomes embedded in the Sertoli cells and are finally released from the seminiferous tubules by process called spermiation

Answer: (c) Corpus luteum

Explanation:
1. After the release of ova, the remaining structure left is called corpus luteum. Corpus luteum secretes progesterone which maintains the endometrium wall and pregnancy

Answer: (d) A- alveoli, B- milk, C-mammary duct

Explanation:
1. A-Alveoli, B-Milk, C-Mammary duct

Answer: (c) Cleavage

Explanation:
1. Cleavage is the series of rapid mitotic division of the zygote, which converts the single celled zygote into a multicellular structure called blastula.

Answer: (b) Oestrogen

Explanation:
1. Oestrogen concentration remains almost constant and produce throughout the menstrual cycle
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.
14. (d) Oestrogen and progesterone levels rise during this phase. It lasts for only 1 day. (e) During pregnancy all events of the menstrual cycle stop and there is no menstruation. The menstrual cycle permanently stops in females at the age of around 50 years. This is called menopause

Answer: (b) Blastomeres

Explanation:
1. The cells formed by cleavage are called blastomere.
2. Implantation
3. (i) Zygote divides rapidly by mitotic division. This is called cleavage. As a result 2, 4, 8, 16 daughter cells are produced which are termed as blastomeres
4. (ii) Embryo with 8-16 blastomeres is called a morula
5. (iii) The morula changes into a large mass of cells called blastocyst, which passes further into the uterus
6. (iv) Blastomeres in the blastocyst are arranged into an outer layer called trophoblast and an inner group of cells attached to trophoblast called inner cell mass
7. (v) The trophoblast layer gets attached to the cells of the endometrium and the inner cell mass gives rise to the embryo
8. (vi) The cells of endometrium divide rapidly and cover the blastocyst
9. (vii) So, the blastocyst gets embedded in the endometrium of the uterus. This is called implantation, which leads to pregnancy

Answer: (a) Subtentacular cells

Explanation:
1. Sertoli cells are also called subtentacular cells

Answer: (c) It provides temperature that is slightly lower than body temperature required for formation of functional sperms

Explanation:
1. In mammals, the primary male sex organs, testes are located in the extra-abdominal scrotal sacs. Scrotum maintains a low temperature of \(2-4℃\) below the temperature of abdominal cavity. As higher abdominal temperature kills the spermatogenic tissue So, testes in mammals are contained scrotal sacs present outside the abdominal cavity to have the low temperature that is needed for the formation and maturation of functional sperms.

Answer: (b) Seminal vesicle

Explanation:
1. Seminal vesicle produce 60% of the semen and gives alkaline medium to the sperm for the nutralisation of vaginal acidic medium