Human Reproduction: NEET PYQs and weightage

(a) Placenta also acts as an endocrine tissue and produces several hormones like human chorionic gonadotropin (hCG), human placental lactogen (hPL), estrogens, progestogens, etc. (b) The secondary oocyte forms a new membrane called zona pellucida surrounding it. (c) The male accessory glands include paired seminal vesicles, a prostate and paired bulbourethral glands. Secretions of these glands constitute the seminal plasma which is rich in fructose, calcium and certain enzymes. The secretions of bulbourethral glands also helps in the lubrication of the penis. (d) The regions outside the seminiferous tubules called interstitial spaces, contain small blood vessels and interstitial cells or Leydig cells synthesise and secrete testicular hormones called androgens.

Both Statement I and Statement II are true.

In human females, meiosis II is not completed until fertilisation takes place when the ovum is released and the sperm cell contacts the plasma membrane of the oocyte.

The extraembryonic membranes are amnion, chorion, allantois, and Yolk sac. Amnion is formed from mesoderm on the outer side and ectoderm on the inner side. Chorion is formed from trophectoderm and mesoderm whereas allantois and yolk sac membranes have mesoderm on the outer side and endoderm on the inner side.

Gonadotropin-releasing hormone (GnRH) is produced by the hypothalamus. It stimulates the pituitary gland to produce luteinizing hormone (LH) and, to a lesser extent, follicle-stimulating hormone (FSH). However, with depletion of follicular number, estrogen levels decrease with subsequent loss of negative feedback and resultant increases in GnRH secretion. Progesterone also decreases GnRH secretion at the level of the hypothalamus.

Mons pubis is the rounded mass of fatty tissue lying over the joint of the pubic bones, in women typically more prominent and also called the mons Veneris. The antrum is a fluid-filled space that develops among the follicle cells; it starts as multiple small spaces that eventually coalesce into a single large antrum. Trophoblast are cells that form the outer layer of a blastocyst, and are present four days post fertilization in humans. Trophoblast invasion of the uterus is a necessary step at implantation of the human blastocyst. The zona pellucida is a glycoprotein layer surrounding the plasma membrane of mammalian oocytes. Hence correct matching is: a) - iii), b) - iv), c) - i), d) - ii)

Ectopic pregnancies are referred to as implantation of embryos at sites other than uterus, either in the fallopian tubes, cervix or ovary.

When sperm nucleus enters into the secondary oocyte during fertilization, it provides the anaphase promoting factor that induces the completion of meiosis in the secondary oocyte.