WEEK 2: ANATOMY AND PHYSIOLOGY OF THE BREAST AND LACTATION

Question 1

Where are breasts located?

Why do women’s breasts become more prominent than those of men?

State the hormones during pregnancy that the breast is responsive.

How many lobes does each breast contain?

Answer 1

The breast is the upper ventral region of the torso of a human, bilaterally.

Both men and women develop breasts from the same embryological tissues.
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At puberty, female sex hormones, mainly estrogen, promote breast development which does not occur in men due to the higher amount of testosterone. As a result, women’s breasts become far more prominent than those of men.

During pregnancy, the breast is responsive to a complex interplay of hormones estrogen, progesterone, human Chorionic somatomammatropin and prolactin, which cause glandular tissue in the breast to change.

Breast tissue develops and enlarges in order to produce milk.

Each breast contains 15–20 lobes and subcutaneous adipose tissue.

Question 2

State the basic anatomical components of the breast.

Answer 2

Includes the nipple and areola, mammary tissue, supporting connective tissue and fat, blood and lymphatic vessels, and nerves

Question 3

Each breast is a mammary gland, which is a modified ____________ in females that produces the milk.

Externally it has the nipple with a series of closely packed openings of ducts which are called _____________ where milk emerges.

The areola which contains modified sebaceous glands known as ______________.

Strands of connective tissues called _________________run between the skin and fascia which support the breast.

A mammary gland consists of 15 -20 lobes or compartments separated by adipose tissue, each lobe is then divided into smaller units called _____________.

Each lobule is composed of many grape-like clusters of milk secreting glands ____________ which are embedded in the connective tissue.

Between the alveoli present the ____________, by the contraction of which can help the ejection of the milk.

The alveoli are connected by ______________, then to ___________ which expands to form the __________________where the milk is stored before draining into the _______________. This duct opens in the nipple.

Answer 3

Each breast is a mammary gland, which is a modified apocrine sweat gland in females that produces the milk.

Externally it has the nipple with a series of closely packed openings of ducts which are called lactiferous ducts where milk emerges.

The areola which contains modified sebaceous glands known as Montgomery glands.

Strands of connective tissues called cooper’s ligaments run between the skin and fascia which support the breast.

A mammary gland consists of 15 -20 lobes or compartments separated by adipose tissue, each lobe is then divided into smaller units called lobules.

Each lobule is composed of many grape-like clusters of milk secreting glands alveoli which are embedded in the connective tissue.

Between the alveoli present the myoepithelial cells, by the contraction of which can help the ejection of the milk.

The alveoli are connected by secondary tubules, then to mammary ducts which expands to form the lactiferous sinuses where the milk is stored before draining into the lactiferous duct.

This duct opens in the nipple.

Question 4

State the function of mammary gland.

Answer 4

*To produce and secrete milk

Question 5

State the function of the areola.

Answer 5

*Its primary function is to contain the openings of the Montgomery glands, also known as areolar glands. These glands secrete oils that lubricate and protect the nipple during breastfeeding.

*The areola also plays a role in providing a contrast in color between the darker pigmented area and the surrounding breast tissue, which can aid in the visual identification of the nipple.

*Additionally, the areola contains smooth muscle fibers that can cause the nipple to become erect when stimulated.

Question 6

Name the connective tissue found in the breast.

Answer 6

*Collagen and elastin

Question 7

Describe the evolution of the breast at PUBERTY and in PREGNANCY.

Answer 7

1. Puberty

*Estrogen stimulates ductal growth and branching -Fat deposition to increase the size of the breast

*Progesterone stimulates Alveoli growth

2. Pregnancy

*Estrogen and Progesterone:
Estrogen contributes to further growth and development of the ductal system.

Progesterone, along with estrogen, prepares the alveoli for milk production.

*Prolactin:
Prolactin stimulates the mammary glands to produce milk, but its full lactogenic effect is inhibited by high levels of progesterone during pregnancy.

*Placental Lactogen:
Stimulation of Mammary Gland Growth by promoting the proliferation of mammary epithelial cells, which are essential for the formation of alveoli and ducts within the breast tissue.

-Enhancement of Ductal Development:

-Increased Blood Flow:
PL has vasodilatory effects, meaning it can widen blood vessels. This increased blood flow to the mammary glands is important for the delivery of nutrients and oxygen, supporting the metabolic needs of the rapidly growing breast tissue.

-Promotion of Mammary Gland Differentiation:
This process involves the specialization of cells for specific functions, such as milk production. It is essential for the successful initiation of lactation.

*Other Hormones:
Corticotropic hormone (ACTH), growth hormone (GH), and thyroid-stimulating hormone (TSH) also play roles in supporting overall physiological changes during pregnancy, including breast development.

Question 8

PHYSIOLOGY OF MAMMARY GLAND

Human infants are provided with milk produced from the mammary glands of the mother-lactation-the formation and synthesis of milk is also called _____________.

Non pregnant mammary gland is incapable of lactation.

The mammary glands develop during pregnancy.

The ________ are the primary site of milk production.

Lactation is triggered by the fall in ___________that follows delivery.

The composition of the human milk changes gradually during the first weeks after delivery.

Breast milk synthesis is hormonally controlled.

After delivery the milk production is maintained by __________.

Prolactin output is a direct consequence of nipple stimulation.

Milk ejection is a direct response to the suckling stimulus.

After weaning, the cessation of suckling suppresses the milk production.

Answer 8

Human infants are provided with milk produced from the mammary glands of the mother-lactation-the formation and synthesis of milk is also called (lactogeneis) galactopoiesis.

Non pregnant mammary gland is incapable of lactation.

The mammary glands develop during pregnancy.

The alveoli are the primary site of milk production.

Lactation is triggered by the fall in steroid secretion that follows delivery.

The composition of the human milk changes gradually during the first weeks after delivery.

Breast milk synthesis is hormonally controlled

After delivery the milk production is maintained by regular suckling.

Prolactin output is a direct consequence of nipple stimulation

Milk ejection is a direct response to the suckling stimulus

After weaning, the cessation of suckling suppresses the milk production.

Question 9

Discuss the physiology of mammary glands under the following sub-headings.

1. Development of Mammary Glands at puberty and in pregnancy.
2. Lactation
   *Hormonal regulation
   *Milk synthesis
   *Milk ejection
   *Maintained milk production
3. Involution

Answer 9

1. Development of Mammary Glands:

a. Puberty:

*During puberty, hormonal changes, particularly the rise in estrogen, stimulate the development of mammary glands.

*Estrogen promotes the growth and branching of ductal structures within the breast tissue.

b. Pregnancy:

The mammary glands undergo further development and preparation during pregnancy.

Progesterone, along with estrogen, stimulates the growth of alveoli, which are small, grape-like clusters that will produce milk during lactation.

2. Lactation:

a. Hormonal Regulation:

*Prolactin: Produced by the anterior pituitary gland, prolactin is a key hormone in initiating and maintaining milk production. It stimulates the alveoli to produce milk.

*Oxytocin: Produced by the hypothalamus and released by the posterior pituitary gland, oxytocin is essential for the ejection of milk (letdown reflex) during breastfeeding.

b. Milk Synthesis:
Mammary glands produce milk in alveoli, which are composed of milk-secreting cells.

Milk synthesis involves the uptake of nutrients, including proteins, fats, and sugars, from the bloodstream and their incorporation into milk.

c. Milk Ejection:
Oxytocin is released in response to stimuli such as suckling or other sensory signals associated with breastfeeding.

Oxytocin causes the contraction of myoepithelial cells surrounding the alveoli, leading to the ejection of milk from the alveoli into the ducts, making it available for the infant.

d. Maintenance of Milk Production:

Continued milk production is dependent on regular and effective breastfeeding. The removal of milk signals the mammary glands to produce more milk.

Prolactin levels remain elevated as long as milk removal continues, maintaining the production of milk.

3. Feedback Mechanisms:

a. Negative Feedback:
The removal of milk from the breast serves as a negative feedback mechanism. As milk is removed, the signal to produce more milk is maintained, and as the breast fills, the signal diminishes.

b. Hormonal Changes Postpartum:
After childbirth, there is a decrease in estrogen and progesterone levels, allowing prolactin to exert its full effect on milk production.

4. Involution:

a. Weaning or End of Lactation:

When breastfeeding ceases, there is a process called involution, where the mammary glands return to a non-lactating state.

The glandular tissue regresses, and the breast returns to a state similar to its pre-pregnancy condition.

Question 10

What is lactogenesis?

Answer 10

Lactogenesis is a series of cellular changes whereby mammary epithelial cells are converted from a non-secretory state to a secretory state.

Lactogenesis refers to the process of milk production in the mammary glands.

It encompasses the stages leading to the synthesis, secretion, and maintenance of milk production.

Question 11

State the two hormones that directly affect breastfeeding.

When a baby suckles at the breast, sensory impulses pass from the nipple to the brain.

In response, the anterior lobe of the pituitary gland secretes ______, and the posterior lobe secretes __________.

Answer 11

There are two hormones that directly affect breastfeeding: prolactin and oxytocin. A number of other hormones, such as oestrogen, are involved indirectly in lactation .

When a baby suckles at the breast, sensory impulses pass from the nipple to the brain. In response, the anterior lobe of the pituitary gland secretes prolactin, and the posterior lobe secretes oxytocin.

Question 12

Lactogenesis is the process of developing the ability to secrete milk and involves the maturation of alveolar cells.

It takes place in 2 stages:

State them.

Answer 12

Secretory initiation and secretory activation.

Question 13

Describe Lactogenesis I (Secretory Initiation)

Answer 13

Lactogenesis I (Secretory Initiation):

*This phase begins during pregnancy, around the second half, and continues into the early postpartum period.

*During pregnancy, the mammary glands undergo structural development in preparation for milk production. Hormones such as progesterone and estrogen play a role in this phase.

*The placenta supplies high levels of progesterone which inhibit further differentiation. Milk secretion is inhibited by high levels of progesterone.

*In this stage, small amounts of milk can be secreted by week 16 gestation.

*By late pregnancy, some women can express colostrum.

Question 14

Describe Lactogenesis II (Transitional milk)

Answer 14

Voluminous Milk production

*At birth, the delivery of the placenta results in a sudden drop in progesterone/estrogen/HPL levels. Causing start of Lactogenesis II

*Other hormones (insulin, thyroxine, cortisol) are also involved, but their roles are not yet well understood.

*Lactogenesis II commences approximately 30-40 hours after birth.

*During this phase, the composition of the milk changes from colostrum to transitional milk, which is higher in volume and contains increasing amounts of lactose, fat, and water.

*The milk becomes more mature and is better suited to meet the growing nutritional needs of the infant.

Question 15

Usually, at days 2 or 3 postpartum, most women experience swelling of the breast along with copious milk production.

Outline some of the factors that can result in delayed milk production in Lactogenesis II.

Answer 15

*In primiparous women, the secretory activation stage is slightly delayed, and early milk volume is lower.

*Lower milk volume is also observed in women who had cesarean births compared with those who delivered vaginally.

*Late onsetof milk production has also been seen in women who have had retained placental fragments.
-With retained placental fragments, lactogenesis stage II could be inhibited by the continued secretion of progesterone and would continue to be inhibited until removal of the remaining placental.

*Diabetes

*Stressful vaginal deliveries

Question 16

Describe Lactogenesis III (Mature Milk).

Answer 16

Lactogenesis III (Mature Milk):

Lactogenesis III is the final phase during which the milk composition becomes relatively stable.

Mature milk is produced, containing the appropriate balance of nutrients for the infant’s growth and development.

This phase typically begins around the second week postpartum and can continue as long as breastfeeding continues.

The mature milk is composed of foremilk, which is the thinner milk at the beginning of a feeding, and hindmilk, which is richer in fat and is released later during a feeding.

Question 17

Describe the hormonal control of lactation.

Answer 17

Estrogen: stimulate the growth of the ductal system to grow and branch, simultaneously the stroma increases in quantity and large amount of fat are laid down.

Progesterone: is required for the full development of the lobule –alveolar system. Final development of the breast into milk secreting organ, it works synergistically with estrogen and other hormones.

Prolactin: promotes lactation, this is secreted by the anterior pituitary and its concentration in the blood raises steadily from the 5th week of pregnancy until the birth of the child. At that time, it has risen to 10-20 times.

Immediately after the childbirth, there is a sudden loss of estrogen and progesterone allows the lactogenic effect of prolactin to produce the milk and continue for two three years.

Prolactin inhibitory hormone: it is secreted by the hypothalamus which plays an important role in controlling prolactin secretion. Dopamine is antagonistic to prolactin.

Oxytocin: helps in the ejection of milk from the alveolar region into the ducts.

This is caused by a combined neurogenic and hormonal reflex. The oxytocin carried by the blood causes the myoepithelial cells to contract, thereby forcing the milk to ejection or milk let-down.

In addition to prolactin, four more hormones are involved in ongoing milk production: cortisol, insulin, parathyroid and growth hormone..

Question 18

In addition to prolactin, four more hormones are involved in ongoing milk production.

Outline them.

Answer 18

*Cortisol
*Growth hormone
*Parathyroid hormone
*Insulin

Question 19

Prolactin is a polypeptide hormone synthesized by _____________ in the anterior pituitary and is structurally similar to growth hormone and placental lactogen.

Prolactin is both positively and negatively regulated, but its main control comes from hypothalamic inhibitory factors such as dopamine which act on the D2 subclass of dopamine receptors present in lactotrophs.

Prolactin stimulates mammary gland ductal growth and epithelial cell proliferation and induces milk protein synthesis.

Emptying of the breast by the infant’s suckling is thought to be the most important factor.

Prolactin concentration increases rapidly with suckling of the nipple which stimulates nerve endings located there.

Answer 19

Prolactin is a polypeptide hormone synthesized by lactotrophic cells in the anterior pituitary and is structurally similar to growth hormone and placental lactogen.

Question 21

Describe the nervous system control of lactation.

Answer 21

1. Hypothalamus Stimulation:

The process begins in the hypothalamus, a region of the brain that senses various stimuli, including those related to the infant’s feeding and suckling.

Sensory stimuli, such as the baby sucking at the breast, activate nerve endings in the nipple. These signals are transmitted to the hypothalamus.
Release of Oxytocin and Prolactin:

The hypothalamus responds to the sensory stimuli by releasing oxytocin-releasing hormone (OTRH) and prolactin-releasing hormone (PRH).

OTRH stimulates the release of oxytocin from the posterior pituitary gland, while PRH stimulates the release of prolactin from the anterior pituitary gland.

2. Oxytocin and Milk Ejection (Letdown):

Oxytocin is released in response to suckling or other stimuli, causing the contraction of myoepithelial cells surrounding the alveoli and ducts in the mammary glands.

These contractions result in the ejection of milk from the alveoli into the ducts, making it available for the infant to consume during breastfeeding.

3. Prolactin and Milk Synthesis:

Prolactin stimulates milk synthesis in the alveolar cells of the mammary glands. It promotes the production of milk components such as lactose, lipids, and proteins.

The continuous and effective suckling by the infant helps maintain high prolactin levels, supporting ongoing milk production.

Feedback Mechanism:

Both oxytocin and prolactin release are subject to a feedback mechanism.

As milk is removed from the breast during breastfeeding, nerve signals are sent back to the hypothalamus to inhibit further release of oxytocin and prolactin temporarily.

This feedback loop helps regulate the amount of milk produced based on the infant’s demand.

Question 22

Describe the milk let down reflex.

Answer 22

1. Stimulation of Nipple and Areola:

The sensory nerves in the nipple and areola are stimulated when the baby latches onto the breast and begins to suckle.

The stimulation can also be triggered by other factors, such as the sound of the baby crying or even thinking about the baby.

2. Nerve Signals to the Hypothalamus:

The sensory signals from the nipple and areola travel to the hypothalamus, a region in the brain that regulates various bodily functions.

3. Release of Oxytocin:

In response to the nipple stimulation, the hypothalamus signals the posterior pituitary gland to release oxytocin into the bloodstream.

Oxytocin is a hormone that plays a key role in the milk letdown reflex.

4. Contraction of Myoepithelial Cells:

The released oxytocin causes the myoepithelial cells to contract rhythmically around the alveoli and ducts.

This contraction squeezes the milk from the alveoli into the ducts, moving it toward the nipple.

Milk Ejection:

As the milk is forced into the ducts, it becomes available for the baby to suck and swallow.

This phase is often referred to as the “letdown” or “milk ejection” phase, and it ensures that the baby receives a steady flow of milk during breastfeeding.

5. Sensation of Milk Flow:

The mother may feel a tingling or mild discomfort in the breasts as the milk begins to flow. This sensation is sometimes described as a “letdown” feeling.

6. Feedback Loop:

The milk letdown reflex is subject to a feedback mechanism. As the baby continues to suck and consume milk, there is low milk hence the sensory signals from the breast to the brain reduce the release of oxytocin, allowing the milk ejection reflex to diminish until the next breastfeeding session.

When the baby stops suckling, the feedback loop is broken hence milk letdown ceases.

Question 23

State the nutritional needs of a lactating woman.

Answer 23

1. Calories:
   Lactating women generally require additional calories to support milk production. The exact amount varies, but an additional 500 calories per day is a common recommendation.
2. Protein:
   Adequate protein intake is essential for the production of breast milk and the overall health of both the mother and the infant.

Good sources of protein include lean meats, poultry, fish, eggs, dairy products, legumes, and nuts.

3. Calcium:
   Calcium is important for maintaining bone health, both for the mother and the developing infant. Dairy products, fortified plant-based milk, leafy green vegetables, and fortified foods are good sources of calcium.
4. Iron:
   Iron requirements increase during lactation to compensate for iron lost in breast milk. Iron-rich foods, such as lean meats, poultry, fish, fortified cereals, and legumes, are important for preventing iron deficiency.
5. Folate:
   Folate is essential for cell division and the production of DNA. It is important for the growth and development of the infant. Foods rich in folate include leafy green vegetables, legumes, fortified cereals, and citrus fruits.
6. Omega-3 Fatty Acids:
   Omega-3 fatty acids, especially DHA (docosahexaenoic acid), are crucial for the development of the infant’s brain and eyes. Fatty fish, flaxseeds, chia seeds, and walnuts are good sources of omega-3 fatty acids.
7. Vitamin D:
   Vitamin D is important for bone health and immune function. Lactating women may need to ensure adequate sun exposure or take a vitamin D supplement, especially if they have limited sun exposure.
8. Iodine:
   Adequate iodine is important for the development of the infant’s thyroid function. Iodized salt, seafood, dairy products, and seaweed are good sources of iodine.
9. Vitamin B12:
   Vitamin B12 is important for the development of the infant’s nervous system. Good sources include animal products such as meat, poultry, fish, eggs, and dairy.
10. Fluids:
    Staying well-hydrated is essential for milk production. Lactating women should drink plenty of water throughout the day.
11. Zinc:
    Zinc is important for immune function and overall growth. Good sources include meat, dairy products, nuts, and whole grains.
12. Fiber:
    Adequate fiber from fruits, vegetables, whole grains, and legumes helps prevent constipation, a common issue during the postpartum period.

Question 24

State the advantages of breastfeeding to the infant.

Answer 24

1. Nutrient-Rich:

Breast milk provides the ideal balance of nutrients for a baby’s growth and development. It contains the right mix of proteins, fats, vitamins, and carbohydrates.

2. Immune System Support:

Breast milk is rich in antibodies, enzymes, and white blood cells, providing passive immunity to protect infants against infections and illnesses.

3. Digestibility:

Breast milk is easily digestible, reducing the risk of constipation and other digestive issues in infants.

4. Optimal Brain Development:

Breast milk contains essential fatty acids like DHA (docosahexaenoic acid), crucial for brain and nervous system development.

5. Reduced Risk of Infections:

Breastfed infants have a lower risk of ear infections, respiratory infections, gastrointestinal infections, and other illnesses.

6. Lower Risk of Allergies and Asthma:

Breastfeeding has been associated with a reduced risk of allergies, asthma, and eczema in children.

7. Lower SIDS Risk:

Breastfeeding is linked to a lower risk of sudden infant death syndrome (SIDS).

8. Proper Jaw and Tooth Development:

The act of breastfeeding supports the development of the infant’s jaw and helps in the proper alignment of teeth.

Question 25

State the advantages of breastfeeding to the mother.

Answer 25

Advantages for Mothers:

*Bonding and Emotional Well-being:

Breastfeeding fosters a strong emotional bond between the mother and the infant, promoting a sense of security and well-being for both.

*Postpartum Weight Loss:

Breastfeeding burns calories, helping mothers lose pregnancy weight more effectively.

*Uterine Contraction:

Breastfeeding triggers uterine contractions, aiding in postpartum recovery and reducing the risk of postpartum hemorrhage.

*Reduced Risk of Breast and Ovarian Cancer:

Breastfeeding is associated with a reduced risk of breast and ovarian cancers in mothers.

*Natural Contraception (Lactational Amenorrhea Method):

Breastfeeding can act as a natural form of contraception, reducing the likelihood of ovulation and conception during exclusive breastfeeding in the early months.

*Economic and Environmental Benefits:

Breastfeeding is cost-effective as it requires no preparation or equipment, and it contributes to environmental sustainability by reducing the need for formula production and packaging.

Convenience:

Breast milk is always available and at the right temperature, eliminating the need for formula preparation and bottle warming.

*Quicker Postpartum Recovery:

Breastfeeding releases hormones that help the uterus return to its pre-pregnancy size more quickly.

Question 26

Describe 2 ways in which breastfeeding affect the menstrual cycle.

Answer 26

*In addition, suckling suppress the menstrual cycle because prolactin inhibits GnRH there by suppressing FSH and LH. Lactation therefore tends to prevent ovulation and decrease the likelihood of another pregnancy.

*For the mother: breast feeding is also advantageous to the mother. Oxytocin triggered by nursing hastens the uterine involution.