LACTATION

LACTATION

is the process by which milk is synthesized and secreted from the mammary glands of the postpartum female breast in response to an infant sucking at the nipple.

Breast milk

provides ideal nutrition and passive immunity for the infant, encourages mild uterine contractions to return the uterus to its pre-pregnancy size (i.e., involution), and induces a substantial metabolic increase in the mother, consuming the fat reserves stored during pregnancy.

Mammary glands 

• are modified sweat glands. 

• is composed of milk-transporting lactiferous ducts, which expand and branch extensively during pregnancy in response to estrogen, growth hormone, cortisol, and prolactin.

Mammary glands 

• The non-pregnant and non-lactating female breast is composed primarily of adipose and collagenous tissue, with mammary glands making up a very minor proportion of breast volume.

Breast alveoli

are balloon-like structures lined with milk-secreting cuboidal cells, or lactocytes. Milk is secreted from the lactocytes, fills the alveoli, and is squeezed into the ducts.

Lobules

are clusters of alveoli that drain to a common duct. The lactating female has 12–20 lobules organized radially around the nipple.

 Nipple Pores

Milk drains from lactiferous ducts into lactiferous sinuses that meet at 4 to 18 perforations in the nipple

Montgomery glands

The small bumps of the areola (the darkened skin around the nipple). They secrete oil to cleanse the nipple opening and prevent chapping and cracking of the nipple during breastfeeding.

PROLACTIN

• Pituitary hormone. Instrumental in the establishment and maintenance of breast milk supply.

• Important for the mobilization of maternal micronutrients for breast milk.

• 10–20 times

• Near the fifth week of pregnancy, the level of circulating prolactin begins to increase, eventually rising to approximately ____________ the pre-pregnancy concentration.

After childbirth

• baseline prolactin level drops sharply, but it is restored for a 1- hour spike during each feeding to stimulate the production of milk for the next feeding.

OXYTOCIN

• Released from the posterior pituitary.

• stimulates myoepithelial cells to squeeze milk from the alveoli so it can drain into the lactiferous ducts, collect in the lactiferous sinuses, and discharge through the nipple pores.

• prolactin

• oxytocin

• growth hormone

• cortisol

• parathyroid hormone

• insulin

These hormones help facilitate the transport of nutrients like amino acids, fatty acids, glucose, and calcium into breast milk during lactation

Human milk

• is low in protein and mineral content and high in lactose.

• suits the needs for growth, development, and training of the large brain at first

• Protein – 4 kcal/g (17 kJ/g)

• Carbohydrates – 3.8 kcal/g (16 kJ/g)

• Fat – 8.8 kcal/g (37 kJ/g)

Energy yield of human milk per gram of nutrient:

753 kcal/liter (3150 kJ/L)

On average, mature human milk yields approximately _________.

500g/day

How much breast milk per day is needed in the second year of life to cover about 30% of energy, 45% of Vitamin A, and 95% of Vitamin C daily requirements in children?

• Lactose

• Fat

• Proteins

• Minerals 

• Vitamins

Major constituents of human milk:

Iron Content of Human Milk

Despite the low content of iron in human milk, its bioavailability is exceptionally high (the low iron content may limit the growth of microbes and so protect the infant from gastrointestinal infections).

50%

Iron absorption from human milk is about _____

Colostrum

Which specific type of breast milk is especially high in Vitamin A and supports the infant’s growth, gut maturation, and nervous system development?

Colostrum

What is the thick, yellowish substance that fills the alveoli in the final weeks of pregnancy, high in protein but lower in fat and glucose compared to mature breast milk?

Mature milk

does not leak during pregnancy and is not secreted until several days after childbirth.

colostrum

Before childbirth, some women experience leakage of ________ from the nipples.

Cow’s milk

• is not a substitute for breast milk. It contains less lactose, less fat, and more protein and minerals.

• difficult for an infant’s immature digestive system to metabolize and absorb.

COLOSTRUM

• is secreted during the first 48–72 hours postpartum. (approximately 3 ounces in a 24-hour period).

• is rich with immunoglobulins, which confer gastrointestinal, and also likely systemic, immunity as the newborn adjusts to a nonsterile environment. 

Transitional milk

What type of milk is secreted by the mother after about the third postpartum day, serving as an intermediate between colostrum and mature milk?

first few weeks of breastfeeding

may involve leakage, soreness, and periods of milk engorgement as the relationship between milk supply and infant demand becomes established. Once this period is complete, the mother will produce approximately 1.5 liters of milk per day for a single infant.

Foremilk

the early milk, is watery, translucent, and rich in lactose and protein. Its purpose is to quench the infant’s thirst.

Hindmilk

is delivered toward the end of a feeding. It is opaque, creamy, and rich in fat, and serves to satisfy the infant’s appetite.

meconium , bilirubin

During the first days of a newborn’s life, it is important for ________ to be cleared from the intestines and for ________ to be kept low in the circulation.

bilirubin

a product of erythrocyte breakdown, is processed by the liver and secreted in bile. It enters the gastrointestinal tract and exits the body in the stool.

Bilirubin

What substance, when present at high concentrations in the blood, causes jaundice and can lead to brain damage in newborns?

Hyperbilirubinemia

 a high level of circulating bilirubin, is the most common condition requiring medical attention in newborns.

phototherapy

Newborns with hyperbilirubinemia are treated with _________ because UV light helps to break down the bilirubin quickly.

Infants not breastfed

• have a higher risk of childhood diabetes, childhood lymphomas, celiac disease, Crohn’s disease, and are more prone to asthma and other atopic diseases.

Early breastfeeding

• facilitates uterine contraction and decreases postpartum hemorrhage.

• Also ensure the saving of iron stores, as iron loss associated with menstruation is higher compared with lactation.

STAGE 1: MAMMOGENESIS

• Occurs when the breasts are formed, right from birth, through to puberty and, then, the process is completed during pregnancy.

• This stage of lactation begins in a woman when she is still in her own mother’s womb, as a tiny embryo. 

STAGE 1: MAMMOGENESIS

• At 12 weeks of gestation, the breasts have grown nipples, areolae, alveoli (milk-producing cells), and mammary buds. Sex hormones will then further develop the breasts until she is born.

Estrogen and pituitary growth factors

During puberty, ________________ will prompt the breasts to grow. More and more breast tissue is stored with every monthly ovulation cycle, up until the age of 35.

• Prolactin,

• Placental lactogen

• Estrogen 

• Progesterone

• Adrenocorticotropic hormone

Which hormones are responsible for the final breast changes during pregnancy that prepare a woman to produce milk?

STAGE 2: LACTOGENESIS

The second stage of lactation: (making of milk) (stages 1 and 2). This is when a mother starts to adequately produce milk.

Lactogenesis — Stage 1

• is between mid pregnancy and two days postpartum ( after the birth).

• the mother's breasts may feel enlarged; this is because of the alveoli that have begun to create colostrum.

Lactogenesis — Stage 2

• is between day three and day eight postpartum.

• the alveoli cells become restricted and tightly spaced. This improves the production of lactose, glucose, and milk lipids and lessens the production of protein, sodium, chloride, nitrogen, and magnesium.

hormones

• Lactogenesis stages one and two are controlled by ________.

Lactogenesis — Stage 2

During this stage, the breasts may feel warm and become engorged if they are not emptied frequently enough. If the mother does not breastfeed, her breasts will start producing mature milk and start providing colostrum once again. Eventually, they will stop producing milk altogether. The breasts will begin to produce colostrum after three days of no milk extraction from them.

STAGE 3: GALACTOPOIESIS / GALACTOGENESIS

• This is the creation and sustaining stage of mature milk from day nine post partum until the baby besides to wean.

autocrine system

• Lactogenesis stage 3 is controlled by the ___________ but hormones do still play a part.

FIL (Feedback Inhibitor of Lactation).

What whey protein in breast milk acts as a feedback inhibitor, slowing milk production when the alveoli are full?

STAGE 4: INVOLUTION

This is when the breasts cease to produce milk after weaning.

500 kcal

• The RENI specify by how many kcal increase per day in the diet to normalize body composition progressively and to provide for adequate lactation.

23 grams per day in the first six months and 18 grams per day in the second six months.

How much additional protein per day is recommended during the first and second six months of lactation?