Test: Parturition and Lactation (NCERT) - NEET MCQ

• Parturition starts with the signal released by the fetus and the placenta.
• These act on the pituitary to release oxytocin.
• Oxytocin acts as a stimulant leading to contractions of the uterine muscles.
• The uterine contractions feedbacks to release more oxytocin from the pituitary.
• This results in more powerful contractions of the uterus until the baby is delivered in the process of parturition.

Signal for parturition comes from fully developed fetus and placenta. Oxytocin and relaxis play major role in parturition fetus shows movements first time during fifth month pregnancy. Embryo's hearth is formed after the first month pregnancy.

(A) In human beings, the menstrual cycle ceases around 50 years of age; this is termed as "menopause." Menopause is a natural biological process that marks the end of a woman's reproductive years. During menopause, the ovaries stop releasing eggs, and the levels of certain hormones, such as estrogen and progesterone, decrease. 

(B) The milk produced during the initial few days of lactation is called "colostrum." Colostrum is a specialized form of breast milk that is rich in essential nutrients and antibodies. It contains several bioactive compounds absolutely essential to develop resistance for newborn babies. These antibodies help protect the infant from infections and provide important nutrients for their early growth and development.

(C) At the completion of the "meiosis I" division, the primary oocyte divides into the "secondary oocyte" and a smaller cell called the "first polar body." Meiosis is the process by which germ cells (eggs and sperm) are formed. In meiosis I, the primary oocyte undergoes a reduction in chromosome number, resulting in the formation of the secondary oocyte and the first polar body. The secondary oocyte is the cell that can potentially be fertilized by a sperm, while the first polar body usually degenerates and does not play a direct role in reproduction.

Third stage of parturition (placental stage) is the time after the delivery until the placenta or after birth is expelled by powerful uterine contractions. Umbilical cord is cut close to the baby's navel. It lasts for 10−15 minutes after the birth of child.

After birth, the first milk released by mammary glands is called colostrum. It is released for 2−3 days. It is thin, yellowish fluid containing cells from the alveoli of glandular tissue of mammary glands and is rich in protein, antibodies, but low in fat.

• Prolactin and Breastfeeding:
  • During breastfeeding, the hormone prolactin is released in higher amounts. Prolactin's primary role is to stimulate milk production, but it also affects reproductive hormones.
• Effect on FSH and LH:
  • Prolactin inhibits the release of follicle-stimulating hormone (FSH) and luteinizing hormone (LH) from the pituitary gland. These hormones are crucial for ovarian follicle development and ovulation.
• Inhibition of Ovulation:
  • By inhibiting FSH, prolactin prevents the development of ovarian follicles and thus suppresses ovulation. This is why breastfeeding can delay the return of menstrual cycles and reduce the likelihood of pregnancy during this period.

Summary:

Breastfeeding suspends pregnancy mainly because of increased prolactin levels, which inhibit FSH release and prevent follicle development and ovulation.

Fertilization is the process in which a sperm cell (from the male) combines with an egg cell (from the female) to form a zygote. This fusion of genetic material results in the formation of a single diploid cell, which will eventually develop into an embryo. It typically occurs in ampulla of fallopian tube.

Cleavage is a series of rapid cell divisions that occur shortly after fertilization. These divisions lead to the formation of a multicellular structure called a blastula. Cleavage takes place of isthmus of oviduct.

Morula is a solid mass of cells that results from several rounds of cleavage divisions. It is the early-stage embryo consisting of 16 or more cells. It is formed in the later part of oviduct.

Blastocyst is a more advanced stage of embryonic development. It is a hollow, fluid-filled structure with two distinct cell layers: the inner cell mass, which will develop into the embryo, and the outer trophoblast, which will form the placenta. The blastocyst reaches the uterus and typically implants into the uterine wall during this stage.

Parturition refers to the process of childbirth or labor. It involves the series of events that lead to the expulsion of the developing fetus from the mother's uterus, ultimately resulting in the birth of the baby. It occurs via cervix and vagina, combinely knon as 'birth canal'.

Parturition is the act of expelling the full-term young one from the mother's uterus at the end of gestation. Gestation (pregnancy) is completed in about 266 days from the mother's last menstruation.

Mammary gland cells develop the potential to produce milk towards the end of pregnancy. This process is termed as lactation.

The milk produced during the initial few days of lactation is called colostrum which contains several antibodies absolutely essential to develop resistance for the new born babies.