2. Lactation

3. Development of the breast
Breast development begins at puberty
Estrogen and progesterone produced in each ovarian cycle affect the breast tissue
Stromal tissue
Adipose tissue
Glandular tissue

4. Hormones in pregnancy

5. Growth of ductile tissue
Function of estrogen
Ductile system laid down even in non gravid female due to estrogen from ovaries starting at puberty
Very high level of estrogen in pregnancy
Further growth of the ductile system
Branching of the ductile system
Stromal cell proliferation
Deposition of fats
GH, Prolactin, Cortisol & insulin are also required for proper growth of the breast

6. Growth of lobule-alveolar system
Function of progesterone
Further proliferation
Budding of alveoli from the ducts
Formation of lobules
Development of secretory characteristics
Secretory changes comparable to effects of progesterone on endometrium

7. Mammary gland

8. Mammary gland

9. Initiation of lactation
Functions of Prolactin
Prolactin causes milk secretion
Prolactin production starts at 5th week of pregnancy and continues to increase for rest of the pregnancy
Human chorionic somatomammotrophic hormone also has lactogenic effects

10. Initiation of lactation
But estrogen and progesterone inhibit actual milk secretion
Only a few ml/day secretion in pregnancy
This secretion is free of fats and concentrated with proteins and lactose
Colostrum
Colostrum is very rich in antibodies and imparts passive immunity against many organisms

11. Initiation of lactation
After parturition estrogen and progesterone levels fall
Prolactin now causes copious milk secretion in next 1-7 days
Other maternal hormones like GH, Parathyroid hormone, Cortisol, and insulin etc are also required for milk secretion
Within a few weeks Prolactin level will return to basal level
Breast feeding → stimulation of Prolactin secretion

12. Initiation of lactation
Suckling by the baby → signals to hypothalamus → inhibition of PIH → ↑ Prolactin 10 – 20 fold
This prolactin will produce milk for subsequent nursing period
Without breast feeding breast stop producing milk within 1-2 weeks
Continued breast feeding is capable of causing milk secretion even for years

13. Prolactin secretion after parturition

14. Hypothalamic control Prolactin secretion is controlled by hypothalamus
Prolactin inhibitory hormone (PIH) which is constantly being produced
Prolactin releasing hormone (PRH)
Suckling stimulation → ↓PIH and ↑ PRH
→ milk secretion
PIH is most probably dopamine

15. Suppression of ovarian cycle
50 % of the nursing mother have lactational amenorrhea
No ovulation
No pregnancy
Suckling signals → suppression of GnRH
Prolactin → ↓ GnRH
Absence of gonadotrophic hormones (FSH & LH)
No ovarian cycle
No menstrual cycle
Adaptation after a few months
Natural WAQFA

16. Ejection of milk
Function of Oxytocin

17. Posterior Pituitary Gland
Neurohypophysis
Develops as an outgrowth of Hypothalamus
Glial cells or Pituicytes- do not secrete hormones
Support terminal nerve endings of neurons in Hypothalamus
Supraoptic Nuclei
Paraventricular Nuclei
Nerve fiber pass through Hypophyseal stalk
Two Hormones
ADH or vasopressin
Oxytocin

18. Hypothalamic control of posterior pituitary

19. Posterior Pituitary Gland
Cutting of Hypophyseal Stalk
Transient fall in both hormones
Normal secretion from cut nerve endings after a few days
Hormones synthesized in nerve cell bodies in hypothalamus
Transported in combination with carrier protein “Neurophysins” along the nerve fibers in axoplasm
Stored in bulbous nerve endings
Released by exocytosis due to nervous impulses from the hypothalamus

20. Chemical structure
Both Oxytocin and ADH are polypeptides having Nine amino acids
ADH
Cys-Tyr-Phe-Gln-Asn-Cys-Pro-Arg-gly
Oxytocin
Cys-Tyr-Ile-Gln-Asn-Cys-Pro-Leu-gly
Only two amino acids differ
Functions also overlap

21. Functions of Oxytocin Produced mainly in Paraventricular nuclei
Milk ejection or milk let down
Milk expressed out of alveoli into the ducts
Suckling stimuli → signals through sensory nerves to cortex → signals to Paraventricular nuclei →signals to posterior pituitary →release of Oxytocin into the blood →contraction of myoepithelial cells around the alveoli → expression of milk into the ducts

22. Stimulation & Inhibition of Oxytocin and milk ejection
Stimuli for Oxytocin release
Sucking sensation from areola and nipple
Crying of the baby
Fondling of the baby by the mother
(Uterine cervical stretch or irritation)
Oxytocin release may be inhibited by
Many psychogenic factors
Anxiety
Tension
Other conditions of generalized sympathetic stimulation

23. Thank-you
Questions ??