91 Lactation Flashcards
What is lactation?
Secretion of milk by breasts (mammary glands)
What is the colostrum?
First milk produced
What is the recommendation for breast feeding?
Exclusively for first 6 months for optimal lifetime benefits
Benefits of breast feeding for baby?
- Reduced incidence of GI, respiratory and middle ear infection
- Decreased risk of childhood diabetes, asthma and eczema
- Reduced risk of lactose intolerance
- Improved intellectual and motor development
- Decreased risk of obesity in later life
- Possible reduced autoimmune diseases
- 27% reduced risk of sudden infant death syndrome
Benefits of breast feeding for mother?
- Promotes recovery from childbirth
- Promotes return to ‘normal’ body weight
- Promotes a period of infertility
- Reduces risk of premenopausal breast cancer
- Reduces risk of ovarian cancer
- Possibly improves bone mineralisation
Role of prolactin in lactational amenorrhoea?
• Prolactin suppresses hypothalamic release of GnRH and therefore pituitary FSH and LH
=> Prevents follicular growth, ovulation and menstruation
• Women who exclusively breast feed their baby will delay the onset of menstrual cycles
Lactational amenorrhoea method (LAM) is effective so long as:
- Must be ammenorrhoeic
- Baby must be exclusively breast fed
- Baby < 6 months old
Breast structure at birth?
Breast consists of lactiferous ducts without any alveoli
Changes to breast at puberty?
- Under influence of oestrogen the ducts proliferate and masses of alveoli form at the ends of the branches
- Each cycle involves proliferative changes in the alveoli and there may be secretory activity
Changes to breasts during pregnancy?
- Under the influence of oestrogen, progesterone and prolactin the glandular portion of the breast undergoes hypertrophy replacing adipose tissue
- From week 16 the breast tissue is fully developed for lactation but is quiescent awaiting activation
- After parturition the breast produces colostrum before mature milk production begins
Breast alveoli development?
- Prior to pregnancy, ducts with few alveoli exist
- In early pregnancy, alveoli grow
- In mid pregnancy, alveoli enlarge and acquire lumen
- During lactation the alveoli dilate
- After weaning, gland regresses
Pathways of alveoli (modified sebaceous glands) emptying in breast?
Via lactiferous ducts that are dilated to form lactiferous sinuses which open on the surface of the nipple
Tissue change in pregnant breast?
- Adipose tissue is dominant in non-lactating breast
* Glandular tissue only develops fully during pregnancy
What are the secretory alveoli/ acini - the milk producing cells, stimulated by?
Prolactin
What is each alveolus surrounded by? Stimulated by?
- Each alveolus surrounded by contractile myo-epihtelial cells
- Stimulated by oxytocin
What happens to the fat in lactating breast?
Replaced by glandular tissue
Hormonal control of lactation?
1
2 stages of lactation?
- Milk production
2. Let down
What is lactation (milk production + let down) controlled by?
- By neurohumoral reflexes
* Prolactin is hormone responsible
What is lactation (milk production + let down) controlled by?
By neurohumoral reflexes
• Prolactin is hormone responsible
Hormonal changes when nursing/ not nursing?
• Prolactin surges each time mother nurses baby due to nerve impulses from nipples to hypothalamus
– Without nursing stimulation, no prolactin surge and loss of milk production
• When not nursing:
Hypothalamus produces prolactin inhibitory hormone
What does lactation inhibit? Interferes with?
Inhibits FSH and LH
=> Interferes with reproductive function
How is lactation inhibited during pregnancy?
- Prolactin controls/ promotes milk production
- Prolactin is secreted during pregnancy (anterior pituitary), but its action is inhibited by high levels of progesterone, oestrogen and hPL (human placental lactogen)
- These steroid levels fall after parturition and milk production begins
2 reflexes of lactation?
- Suckling reflex
2. Milk ejection reflex
Role of prolactin in the suckling reflex?
Suckling stimulus inhibits the hypothalamic release of dopamine (PIF) and prolactin is released in proportion to the strength and duration of the suckling
Role of oxytocin in the milk ejection reflex?
- Suckling stimulates neurones in the hypothalamus to synthesise oxytocin which is carried to posterior pituitary
- Release of oxytocin into the blood stream acts on myo-epithelial cells in the alveoli - causing the ‘let down’ of milk
How does milk ejection become a conditioned reflex?
- Let down in response to the cry of the baby
* Oxytocin release is inhibited by catecholamines: stress can inhibit reflex
What can inhibit oxytocin release?
- Catecholamines
* Stress
Between 32-35 weeks gestation for coordination of ______, ______ and _____
suckling, swallowing and breathing
Why is correct attachment important?
Important to suckle effectively
• Avoid engorgement/ blocked ducts for mum
• Ensure sufficient intake for baby
Movement of milk as an apocrine secretion?
- Synthesised milk fat moves through the cell to the surface membrane. Enclosed lipid droplet is pinched off into the duct lumen
- Milk protein passes through the Golgi apparatus and is released by exocytosis
- Composition varies within a feed and within the lactation period
Difference between colostrum and mature milk production?
1. Colostrum/ 100ml: • Produced for ~ a week • 58 calories • 5.3 g carbohydrates • 2.9g fat • 3.7 g protein • Fewer water-soluble vitamins • More fat-soluble vitamins (particularly A) • More zinc and sodium • Greater amounts of immunoglobulins (IgG , IgA) and a number of growth factors - conferring passive immunity
2. Mature milk/ 100ml: • After 21 days pp • 70 calories • 7.4g carbohydrates • 4.2g fat • 1.3g protein • Relatively low protein and fat compared to other mammals means that human babies don't grow as fast
What 2 things happen in the composition changes of milk?
Over 2 or 3 weeks the composition changes through transitional to mature milk:
- Total calorific value increasing
- IgG and total proteins declining
Why does the baby invariable lose weight over the 1st week when composition of milk changes from transitional to mature milk?
Initially the baby’s GI tract cannot digest nutrients efficiently
How much milk does a woman produce per day? Energy content?
Woman produces 800ml of milk per day with an energy content of 270kJ/ 100mL (will vary through the lactation)
Composition of mature milk?
1. Fat • Main energy source 2. Carbohydrate • Lactose 3. Proteins • Casein • Lactalbumin 4. Fat soluble vitamins • A, D, E, K 5. Water soluble vitamins • B6, B12, C, Folate, Niacin, Riboflavin, Thiamine
Describe the fat which is a composition of mature milk
- Main energy source
- Easily digested emulsified globules
- 4.2 gm/ 100mls polyunsaturated fat
What does lactose (main carbohydrate in mature milk) do?
- Promotes the growth of Lactobacillus bifidus
* Provides galactose for myelin formation
What proteins are in mature milk?
- Casein
* Lactalbumin
What fat soluble vitamins are in mature milk?
- A
- D
- E
- K
What water soluble vitamins are in mature milk?
- B6
- B12
- C
- Folate
- Niacin
- Riboflavin
- Thiamine
How is immunity promoted by mature milk composition?
- Gut is initially sterile
- First feeds will contain acute dose of antigens and bacteria
(600 sp of bacteria identified in breast milk including beneficial Bifidobacterium sps)
