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Parturition & Lactation | Biology Class 12 - NEET PDF Download

Parturition


Parturition is a hormonal process. Many hormonal changes take place during it.

Parturition & Lactation | Biology Class 12 - NEET

1. The progesterone secretion stops, so the placenta dissolves and the foetus is separated from the walls of the uterus.

2. The pituitary gland secretes Oxytocin in more amount. This hormone induces intense contractions in the uterus.
Due to these contractions, the foetus starts moving towards the vagina. The labour pain during child-birth is due to this hormone. Oxytocin is the main parturition hormone. After parturition, Oxytocin stimulates milk-let down by milk ejection reflex.

3. Relaxin hormone is secreted by the placenta and the ovary. This hormone relaxes the pubic-symphysis i.e. the joint between the pelvic-girdles. So more space is available to the foetus to move out.

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Which hormone is responsible for inducing contractions in the uterus during parturition?
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Gestation Period

1. The time from fertilization to parturition is termed as gestation-period. Rabbit has gestation-period of 28-30 days.Parturition & Lactation | Biology Class 12 - NEET

2. They become normal in next 4-5 days. The young-ones of Hare are normal at the time of birth. In humans, the actual gestation period is months+7 days.

3. In human expected date of delivery (EDD) = Ist day of last menstrual cycle+ 9 months + 7 days.


Lactation

“Lactation is the process of milk secretion from the mammary glands of a female after childbirth.”

Lactation is the process of milk secretion from the mammary glands of a mother soon after childbirth. The milk, thus produced provides nutrition and immunity to the young one. Galactopoiesis is the stage that maintains milk production and requires prolactin and oxytocin.

Preparation for Lactation

The female is ready to produce milk during the fifth or sixth month of pregnancy. During the later stages of pregnancy, the female enters the first stage of lactogenesis. At this stage, the breasts make colostrum, a thick, yellow fluid, also known as the first milk a baby receives.Colostrum is highly rich in immunoglobulin A that boosts the immunity of the newborn. It prevents any pathogens from invading the baby’s body and also prevents food allergies.

Lactation Process

  1. Due to the impact of ovarian hormones and placental hormones, breast growth begins during the period of pregnancy and it continues to get larger in size after the childbirth.
  2. During this period, a certain amount of milk is produced in the breast.
  3. The milk secretion increases only after the baby’s birth.
  4. During the process of lactation, the milk is secreted from the mammary glands.

Lactation Hormones

  • Usually hormones, like estrogen, placental lactogenic, progesterone, prolactin and oxytocin are involved in the process of lactation.
  • Estrogen hormone helps in increasing the size of the breast during pregnancy causing the growth of breast tissue.
  • The presence of a placental lactogenic hormone is higher during pregnancy as this hormone helps in stimulating the growth of the nipple, areola and breast tissue.
  • Progesterone hormone helps in increasing the size of the breast tissue along with boosting milk production. During the post-pregnancy period, the progesterone hormone level tends to decrease, which stimulates milk production.
  • Prolactin hormone helps in differentiating the cells that perform their own specific functions. The alveoli, which is responsible for producing milk after the baby’s birth is active mainly because of the prolactin hormone. The prolactin hormone is produced once exposed to cortisol hormone.
  • Once the nipples are stimulated, the oxytocin hormone is released, causing the alveoli to contract. These help in squeezing the milk out into the duct system. The entire process is called as a letdown. The letdown process begins only when the nerves of breasts are stimulated.

Can Lactation Happen without Pregnancy?

There are three hormones, which play an important role in stimulating the milk production in mammary glands of a lactating mother. Consuming medicines of these three hormones in the form of supplements would help women to produce breast milk in their mammary glands without pregnancy.

There are certain other natural tendencies were lactation happens without pregnancy. These include:

  1. Imbalance of hormone.
  2. Side effects from drugs/medicines.
  3. Health disorders.
  4. Nerve irritation in the breast region.
  5. Overproduction of prolactin hormone in the brain.

Properties of Milk

  1. The milk produced in an initial stage of lactation varies from the milk after maturation viz. produced when lactation is well established.
  2. The early milk produced in the initial stage of lactation is known as colostrum.
  3. The composition of milk changes gradually after childbirth. The colostrum changes to transitional milk within four-five days from the childbirth.
  4. After 14 to 15 days of childbirth,  matured milk is produced in mammary glands.

The termination of lactation slowly stops with the reduced demand from the baby.

The document Parturition & Lactation | Biology Class 12 - NEET is a part of the NEET Course Biology Class 12.
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FAQs on Parturition & Lactation - Biology Class 12 - NEET

1. What is parturition?
Ans. Parturition refers to the process of giving birth to offspring in mammals. It involves the expulsion of the fetus and placenta from the uterus.
2. How long is the gestation period in mammals?
Ans. The gestation period in mammals varies depending on the species. It can range from a few days in some small mammals to several months in larger mammals. For example, elephants have a gestation period of around 22 months, while dogs have a gestation period of about 9 weeks.
3. What is lactation?
Ans. Lactation is the process of producing and secreting milk from the mammary glands of female mammals. It typically occurs after parturition and is essential for nourishing the newborn offspring.
4. How long does lactation last in mammals?
Ans. The duration of lactation in mammals also varies depending on the species. It can last from a few weeks to several months. For example, in humans, lactation often continues for the first six months after childbirth, but it can be extended for a longer period if breastfeeding is continued.
5. What are the benefits of lactation for both the mother and the offspring?
Ans. Lactation provides numerous benefits for both the mother and the offspring. For the mother, breastfeeding helps in bonding with the newborn, stimulates the release of hormones that promote maternal behavior, and aids in postpartum recovery. For the offspring, breast milk provides essential nutrients, antibodies for immune protection, and helps in the development of the digestive and immune systems.
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