Test : Previous Year - 2 - Class 12 MCQ

In human, at the end of the first meiotic division, the male germ cells differentiate into the secondary.

Amnion is an extraembryonic membrane in human prevents desiccation of the embryo inside the uterus. Amnion is a membrane that encloses the embryo of reptiles, birds and mammals within the amniotic cavity. This cavity is filled with amniotic fluid, in which the embryo is protected from dessication and from external pressure.

In human female, the periodic discharge of blood, mucus and cellular debris from uterine wall from non-pregnant women of sexual maturity is known as menstrual cycle. Few hours before the start of mensuration, the spiral arterioles constrict one by one resulting into the blanch mucosa. The mucosa shrinks and the death of the blood deprived tissues takes place.

The corpus luteum is essential for establishing and maintaining pregnancy in females. In the ovary, the corpus luteum secretes estrogens and progesterone, which are steroid hormones responsible for the thickening of the endometrium and its development and maintenance, respectively

Seminal plasma is composed of the fluid and sperms from the vas deferens The major components of the seminal plasma in the male reproductive system are mucus, spermatozoa, and various secretions of accessory glands. The seminal plasma is rich in fructose, calcium, ascorbic acid, and certain enzymes. It provides nourishment and protection to sperms.

The human male reproductive system consists of a number of sex organs that are a part of the human reproductive process. In diagram of male reproductive system of human, the point indicated by A,B,C,D are vas deferens, seminal vesicle, prostate and bulbourethral gland.

Foetal ejection reflex in human female is induced by fully developed foetus and placenta. When a woman is in a lithotomy or semi-sitting position, the Foetal Ejection Reflex is impaired and the increased pain caused by the sacrum’s inability to move as the baby descends can be intolerable.

The formation of sperms in mature human testes completed in three important phases in gametogenesis- multiplication, growth and maturation phase. During these phases primarily germ cells change into spermatogonia then spermatocyte during growth phase which change into spermatoids and spermatids into sperms

Fertilization of ovum is the most likely root cause why menstruation is not taking place in regularly cycling human female. In order for fertilization to occur, one of these sperm must attach itself to the ovum and penetrate its outer surface. The fertilized ovum will then continue travelling down the fallopian tube, taking several days until it reaches the uterus. When it arrives, it attaches itself to the lining of the uterus and continues to grow. If the ovum is not fertilized it will die and the progesterone and oestrogen hormone levels will drop. Without these hormones the prepared uterus lining breaks up and is released through the vagina. This is known as a ‘period’.

A change in the amount of yolk and its distribution in the egg will affect pattern of cleavage. The pattern of cleavage is influenced by the amount of yolk in the egg. In eggs with less yolk, cleavages are equal, and the resulting blastomeres are of similar size. If the yolk is localized, such as in frog eggs, then clevages are unequal, the cells derived from the yolky region (the vegetal pole) are larger than those derived from the region without yolk (the animal pole).

In vitro fertilization (IVF) or test-tube baby technique involves fertilizing one or more eggs outside the body and then transferring the fertilized eggs known as pre-embryos back into the uterus. Zygote Intra Fallopian Transfer (ZIFT) is an example of IVF. In this, the zygote or early embryos upto 8 blastomeres are transferred into the Fallopian tube. If the embryo has more than 8 blastomeres then it is transferred into uterus called as IUT.

Sertoli cells are found in the walls of seminiferous tubules of the testes. They anchor and provide nutrition to the developing germ cells especially the spermatids.

Rete testis is connected to caput epididymis by 12-20 fine tubules called vasa efferentia or ductuli efferens. These collect sperms from inside the testis and transfer them to the epididymis. Vas deferens arises from caudal epididymis, conducts sperms from epididymis to urethra.

Seminal plasma in human males are rich in fructose, calcium and certain enzymes. They provide a medium for transport of sperms, nourishes and activates sperms.

Amniocentesis involves prenatal diagnosis of metabolic error and other genetic abnormalities.
 

Parturition is the process of delivery of the foetus. The signals for parturition originate from the fully developed foetus and placenta that induce uterine contraction called foetal ejection reflex. This triggers the release of oxytocin hormone from pituitary. This in turn leads to expulsion of the baby out of uterus.
 

In human beings, after one month of pregnancy, the embryo’s heart is formed. By end of second month pregnancy, the foetus develops limbs and digits. By end of 12 weeks, major organ systems are formed. After fifth month, the first movement off foetus and appearance of hair on its head are observed. By the end of 24 weeks, the body is covered with hairs, eye lids separate and eyelashes are formed.

In Oogenesis, the second maturation division occurs until after the ovum has been penetrated by a sperm. Oogenesis involves the formation of haploid female gametes, ova, from this diploid egg mother cells, oogonia of ovary of female organism.

Acrosome a small pointed structure at the tip of nucleus. It breaks down just before fertilization, releasing hydrolytic enzymes that assist penetration between follicle cells that surrounds the ovum, thus facilitating fertilization

Morula is a solid ball contained within the zone pellucida. It has almost equal quantity of cytoplasm as an uncleaved zygote but much more DNA.

The part of fallopian tube closest to the ovary is infundibulum. Infundibulum possess finger-like projections called fimbriae that help in collection of ovum after ovulation. It leads to wider part of oviduct called ampulla. The last part of oviduct is isthmus that has a narrow lumen and joins the uterus.

If the vasa efferentia in the human reproductive system get blocked the gametes will not be transformed from testes to epididymis.

The testes are present in the scrotum which maintains the scrotal temperature below 2ºC of the internal body temperature.

In the given figure
III - marked portion is Infundibulum
IV - marked portion is Fimbriaa
V - marked portion is Cervix

During fertilisation in humans, many sperms reach close to the ovum. As sperm comes in contact with the zona pellucida layer of the ovum it induces changes in the membrane that blocks the entry of additional sperm. The secretions of acrosome helps one sperm enter cytoplasm of ovum through zona pellucida.