PHYSIOLOGY OF LACTATION
DEVELOPMENT OF BREAST
Present in both the sexes but rudimentary in males and well developed in females.
PHASES OF DEVELOPMENT OF BREAST
In intrauterine life
At birth
At puberty
In pregnancy
During lactation
BREAST IN INTRA UTERINE LIFE ( EMBRYOGENESIS )
•Mammary bud – at 18-19 weeks of gestation thickened mass of epithelium develop.
•16-20 solid outgrowths arises and project into dermis.
•Then this thickened mass andoutgrowth canalized – form Rudimentary duct system.
•Terminal part of outgrowth proliferate into secretory elements, Occurs at puberty.
•Proximal end of each duct opens into common pit by cavitation of thickened mass
•Growth of mesodermal tissue pushes wall of the pit outwards as Nipple.
BREAST AT BIRTH
* At birth rudimentary as tiny nipples and few ducts radiating from it.
BREAST AT PUBERTY
*Upto puberty remain quiescent and then changes occurs.
1)Thelarche – (9-11 yrs of age) at the time of puberty before menses.
*Breast gets enlarged and only duct system proliferate and shows branching.
2) At Menarche – after menses cyclical growth correspond with menstrual cycle.
*In proliferative phase – duct cells proliferate.
*In luteal phase – progesterone stimulate proliferation of terminal ductules – glandular tissue forms.
*At Menstruation –as both oestrogen and progesterone levels , no proliferation of duct cells and glandular tissue.
*With further cycles progressive growth occurs with fat deposition in adipose tissue.
BREAST IN PREGNANCY
*Growth of both - Glandular & Ductal tissue occurs.
*Only during first pregnancy glandular tissue develops fully.
*In first half – Duct system proliferate and shows sprouting and branching along with growth of stroma and deposition of fat.
*In second half – growth of glandular tissue occurs.
BREAST DURING LACTATION
*After child birth alveolar cells get enlarged and distended and starts forming milk (Lactogenesis)
*Involution – after normal period of lactation (7-9 months) alveolar epithelium undergoes apoptosis and glands revert back to non- pregnant state.
FUNCTIONAL ANATOMY OF BREAST
Gross anatomy – round elevated structure present over pectoral region, with central dark pigmented area areola and projected above surface - Nipple.
Histological structure.
*The fascia covering mammary gland is connected by suspensory ligaments to overlying skin and underlying muscle.
*It Consists of 15-20 lobes and each lobe has number of lobules.
*Glandular tissue – consists of alveoli having secretary cells.
*Secretion – Apocrine in nature by exocytosis into ducts.
*About 15-20 ducts opens at summit of nipple, just before opening lactiferous ducts shows dilatation called – Lactiferous sinus.
*Smaller ductules lined by single columnar epithelial cells and near opening at nipple lined by squamous cells.
*Around alveoli ductules and lobules are present in myoepithelial cells – so squeeze and pour content into ductules.
Electron microscopically
*Secretory cells contains rough and smooth endoplasmic reticulum, numerous mitochondria, Golgi apparatus and Lysosomes.
*Protein as membrane bound vesicles & fat as large globule.
CONTROL OF BREAST DEVELOPMENT AND GROWTH
OESTROGEN –
It is essential mainly for ductal growth and fat deposition, also causes thickening of nipple.
PROGESTERONE
It is essential for Glandular tissue development.
Other hormones – Growth hormone, thyroxine, cortisol and insulin cause growth and development.
Corpus luteal & placental hormones – during pregnancy
PROLACTIN
Structure and secretion :
Single peptide chain secreted by acidophilic cells of anterior pituitary gland.
Placental concentration
Pulsatile
Shows diurnal variations
During pregnancy – start at 8th week & peak (200-400 ng/ml) at term
Sources – placenta, amniotic fluid & maternal anterior pituitary gland.
During pregnancy & lactation – affected by oestrogen.
Control of prolactin secretion
Hypothalamic control – Prolactin inhibitory factor from Arcuate nucleus of hypothalamus acts on anterior pituitary gland.
PHASES OF LACTATION
1)Mammogenesis
2)Lactogenesis
3)Galactokinesis
4)Galactopoiesis.
MAMMOGENESIS
•Breast develops fully and prepared for milk secretion after delivery.
•Hyperplasia of ductal & alveolar tissue
•Areola – Pigmented.
•Sebaceous glands becomes prominent in areola.
•Nipples become larger and pigmented.
LACTOGENESIS
Human milk contains
Colostrum – Deep yellow colour fluid during postpartum
Contains – high protein, immunoglobulins & lactoferrins
Granular bodies – colostrum corpuscle (alveolar cells, Leucocytes with fats)
Transition milk or intermediate milk – 6-15th day.
Mature milk – after 15th day
FORMATION OF MILK
Mammary gland – metabolically active
Amino acids , FA, glucose & Ca derived from plasma into alveolar cells.
Process involved are :
1)Fat synthesis and secretion
2)Ion and water secretion
3)Transcytosis of immunoglobulins
4)Exocytosis.
GALACTOKINESIS
It is nothing but expulsion of milk
Milk ejection
Milk expulsion
Milk let down
Suckling effect. (Psychological
component)
GALACTOPOIESIS
It is nothing but maintenance of milk secretion.
Depend on surge in prolactin secretion.
In nursing mothers reflex causes 10-20 fold rise in prolactin secretion for 1 hr & it occurs at every feeding.
It depend on infants demand.
IMPORTANCE OF LACTATION
Advantages of breastfeeding to the baby
Advantages of breastfeeding to the mother.
ADVANTAGES OF BREAST FEEDING TO BABY
1)Balanced diet – contains proteins, minerals, fats, carbohydrates and vitamins
2)Protection against infection – high lymphocytes, neutrophils, macrophages, lysozymes & immunoglobulins.
3)Easily digestible.
4)Growth factors – epidermal growth factors, insulin and somatostatin C are present.
5)Other – sterile, convenient, inexpensive, no allergy.
ADVANTAGES OF BREAST FEEDING TO MOTHER
•Lactational ammenorrhoea (natural contraception)
•Involution of uterus.
•Protection against breast engorgement.
•Protection against obesity – body fat used for milk synthesis.
•Emotional bonding.
•Protection against cancer.
