HND-304 - Lecture 2-Lactation

Biology of Lactation (HND-304)

• Course Details: 3 credits (3-0 lectures)

• Instructor: Saleha Khan, Lecturer, Management and SFAS, UMT

Anatomy and Physiology of Lactation

Hormonal Influences on Breast Development

• Key Hormones: Estrogen, Progesterone, Prolactin, Human Chorionic Somatomammotropin (HCS), Cortisol, IGF1, Thyroid and Growth hormones.

• Breast Development During Pregnancy:

  • Hormones involved: Estrogen, Progesterone, Prolactin, HCS

  • Results in lobuloalveolar and ductal growth.

Physiology of Lactation

• Breast Milk Composition:

  • Complex mixture of nutrients essential for infant health.

• Secretory Pathways: Different mechanisms allow for nutrient secretion:

  1. Transcellular Endocytosis/Exocytosis

  2. Lipid Pathway

  3. Transcellular Salt and Water Transport

  4. Paracellular Pathway

Structure of Alveoli

• Components:

  • Adipose tissue

  • Proceum

  • Myoepithelial cells

  • Lactiferous ducts

  • Lumen of alveoli

  • Laminar cells

Lactation Secretion Routes

• Types of Secretory Pathway Components:

  • Water

  • Lactose

  • Milk Proteins (e.g., Phosphate, Calcium)

Lactation and Immunity

• Mechanism:

  • Secretion involves:

    • Transcellular endocytosis/exocytosis

  • Immunoglobulins from mother’s milk confer immunity to infant until its immune system matures.

• Receptor Involvement: IgA receptor plays a key role.

Lactation Pathways of Nutrient Transport

1. Lipid Pathway:

   • Involves secretion of milk lipids and membrane-bound short-chain fatty acids (SCFA) and long-chain fatty acids (LCFA).

2. Salt and Water Transport:

   • Concentrations: Lactose typically around 200 mM; involved key ions: K, Ca2+, Na.

3. Paracellular Pathway:

   • Passage of nutrients through tight junctions, allowing fluid transfer (e.g., NaCl, H2O).

Summary of Lactation

• Milk Production:

  • Occurs in lobules; ducts merge into main ducts draining to the nipple.

• Roles in Lactation:

  • Lymphatic system, hormonal regulation (estrogen, progesterone, prolactin, oxytocin), sucking reflex are crucial for development, production, and ejection of milk.

• Secretion Pathways: Enable nutrients and fluids to be secreted effectively into breast milk.

Quote of the Day

• "If you cannot do great things, do small things in a great way." - Napoleon Hill