1. Chapter 15 Puerperium and Lactation AVS 222

2. Puerperium The period after parturition when reproductive tract repairs itself and returns to its non-pregnant condition (Uterine involution) Become prepared for another pregnancy Begins immediately after parturition and recovery period varies among species Short and smooth recovery period is desirable

4. Events of Puerperium 1.Myometrium contraction and expulsion of lochia 2.Endometrial repair 3.cyclcity: 4.Elimination of bacterial contamination

6. Stage 1: Myometrium contraction and expulsion of lochia

7. Stage 2 & 3: Endometrial repair Stage 2 & 3: Endometrial repair Resumption of ovarian function –Necrosis of caruncular tissues –Sloughing of the caruncular tissues –Reorganization of uterine endometruim –First postpartum ovulation

8. Continuation of uterine contraction Rise in Estradiol and increase in leukocytes High degree of Stage 4: Stage 4: Elimination of bacterial contamination

11. Lactation

13. The Mammary Gland Exocrine gland; common to all mammals Function: nourish the neonate - Food source: fat, protein, sugar (CHO), vitamins, minerals, water - Protection: immunoglobulins

14. Loosely considered part of the reproductive system: Serves a “reproductive function”; nourishment of the neonate = survival of species. Relies on same endocrine (hormonal) support for development and function. Example: gonadal steroids, prolactin, etc. The Mammary Gland

15. Embryo Origin: The mammary gland is a skin gland – The Mammary Gland

16. Secretory Tissues: Glandular; secreting tissue = – Alveoli: – Duct system; lined by epithelial cells – Lobules & lobes; clusters of alveolar tissue supported by connective tissue The Mammary Gland

19. Alveolus: – basic secretory unit; lined by epithelial cells which synthesize and/or secrete: lipid - triglycerides & free fatty acids (FFA) protein - lactose – minerals & vitamins - Ca, P, K; Vits. A, B, C, D water The Mammary Gland

20. Milk Synthesis Milk synthesis is dependent on: – no. secreting cells – – supply of milk precursor – – milking frequency No. secreting cells is dependent on: – genetics – endocrine support for mammogenesis –

21. Example: What volume of blood would a 1400 lb. Holstein pump per day? Blood Flow (cattle) Blood Components 1400 lb. Cow ~.9 liters/ heart stroke Volume/day =.9 x 70 strokes/min = 63 liters/min 63 liters/min x 1440 min/day = 90,720 liters/day = ~ 22,600 gal/day

22. Blood Flow (cattle) Volume of blood/ volume of milk synthesized = (this is an approximation; actual ratio is affected by stage of lactation, efficiency, etc.) Blood Components

23. Steroid Hormones and Mammogenesis Estrogens: – follicle, placenta, Progesterone: – corpus luteum, placenta, Corticoids: – adrenal cortex

24. Estrogens (E2) (follicle, placenta) 1) 2) 3) synergize with progesterone & prolactin to stimulate protein synthesis and duct growth Steroid Hormones and Mammogenesis

25. Progesterone (P4) (corpus luteum, placenta) 1) stimulates lobulo-alveolar growth– retards milk synthesis 2) retards synthesis of enzymes (a-lactalbumin) necessary for lactogenesis in the prepartum mammary gland Steroid Hormones and Mammogenesis

26. Lactogenesis; Cortisol Action of cortisol:( from adrenal cortex) (dexamethasone is synthetic cort.) 1) synthesis stimulated by maternal, fetal ACTH essential to lactogenesis (adrenalectomy > nolactogenesis) 2)

27. Placental E2 + luteal P4 = – duct development – lobulo-alveolar development – suppression of milk synthesis (P4 suppresses  -lactalbumin; lactose synthesisMammogenesis (Mammary Growth and Development)

28. Action of cortisol + PRL: – increase PRL receptor synthesis – – – increase protein transcription/translation – cortisol is permissive to action of PRLMammogenesis (Mammary Growth and Development)

29. Lactogenesis (Milk Synthesis) How does P4 retard milk synthesis in the nonlactating mammary gland? Blocks glucocorticoid (cortisol) receptors Cortisol + PRL stimulates synthesis of PRL receptors on mammary cells P4 blocks induction of PRL receptors Retards synthesis of a-lactalbumin, casein mRNA Retards casein, a-alactalbumin, lactose synthesis thus, retards milk synthesis

30. Endocrine Glands Supporting Mammary Function Posterior pituitary (protein hormones): Oxytocin Synthesized in the hypothalmus Ttransferred to post. pit. Secreted into blood > acts on myoepithelial cells Contraction of myoepithelial, smooth muscle

32. Endocrine Glands Supporting Mammary Function GH (STH, BST): – increases milk yield Action: increases gluconeogenesis increases blood glucose increases efficiency of production (greater lbs. of milk/ lb. DMI)

33. Endocrine Glands Supporting Mammary Function Pancreas (islets of Langerhans; protein hormones) (responsive to blood glucose concentration) Glucagon (alpha cells): increases lipolysis increases glycogenolysis depresses cellular glucose uptake catabolic to adipose, muscle, liver tissue increases blood glucose concentration

37. Lactogenesis = initiation of milk synthesis – initiated in the E2/P4 “primed” mammary gland when: corpus luteum regresses P4 declines cortisol increases PRL, GH increase – these circumstances occur at parturition Lactogenesis