Parturition & Lactation | Biology Class 12 - NEET PDF Download

Parturition

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.

Gestation Period

1. The time from fertilization to parturition is termed as gestation-period. Rabbit has gestation-period of 28-30 days.

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 9 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.