chapter 15 puerperium and lactation avs 222. puerperium the period after parturition when...
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PuerperiumPuerperium• 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
Events of PuerperiumEvents of Puerperium
1. Myometrium contraction and expulsion of lochia
2. Endometrial repair
3. cyclcity:
4. Elimination of bacterial contamination
Stage 2 & 3:Stage 2 & 3: Endometrial repair Endometrial repairResumption of ovarian function
– Necrosis of caruncular tissues
– Sloughing of the caruncular tissues
– Reorganization of uterine endometruim
– First postpartum ovulation
• Continuation of uterine contraction
• Rise in Estradiol and increase in leukocytes
• High degree of
Stage 4:Stage 4: Elimination of bacterial contamination
The Mammary GlandThe Mammary Gland
• Exocrine gland; common to all mammals
• Function: nourish the neonate
- Food source: fat, protein, sugar (CHO),vitamins, minerals, water
- Protection: immunoglobulins
• 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 GlandThe Mammary Gland
Secretory Tissues:
• Glandular; secreting tissue =
– Alveoli: – Duct system; lined by epithelial cells
– Lobules & lobes; clusters of alveolar tissuesupported by connective tissue
The Mammary GlandThe Mammary Gland
Alveolus:– basic secretory unit; lined by epithelial cellswhich 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 GlandThe Mammary Gland
Milk SynthesisMilk 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– –
Example:What volume of blood would a 1400 lb. Holstein pump per day?
Blood Flow (cattle)
Blood ComponentsBlood 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
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 ComponentsBlood Components
Steroid Hormones and MammogenesisSteroid Hormones and Mammogenesis
• Estrogens:– follicle, placenta,
• Progesterone:– corpus luteum, placenta,
• Corticoids:– adrenal cortex
• Estrogens (E2) (follicle, placenta)
1)
2)
3) synergize with progesterone & prolactin tostimulate protein synthesis and duct growth
Steroid Hormones and MammogenesisSteroid Hormones and Mammogenesis
• 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 MammogenesisSteroid Hormones and Mammogenesis
Lactogenesis; CortisolLactogenesis; Cortisol
• Action of cortisol:( from adrenal cortex)(dexamethasone is synthetic cort.)
1) synthesis stimulated by maternal, fetal ACTH
essential to lactogenesis (adrenalectomy > nolactogenesis)
2)
• Placental E2 + luteal P4 =
– duct development
– lobulo-alveolar development
– suppression of milk synthesis
(P4 suppresses
-lactalbumin; lactose synthesis
MammogenesisMammogenesis
(Mammary Growth and Development) (Mammary Growth and Development)
• Action of cortisol + PRL:
– increase PRL receptor synthesis
–
–
– increase protein transcription/translation
–
• cortisol is permissive to action of PRL
MammogenesisMammogenesis
(Mammary Growth and Development) (Mammary Growth and Development)
LactogenesisLactogenesis(Milk Synthesis)(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 synthesisthus, retards milk synthesis
Endocrine Glands SupportingEndocrine Glands SupportingMammary FunctionMammary 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
Endocrine Glands SupportingEndocrine Glands SupportingMammary FunctionMammary Function
• GH (STH, BST):
– increases milk yield
Action:
•
•
•
• increases gluconeogenesis
• increases blood glucose
• increases efficiency of
production (greater lbs. of
milk/ lb. DMI)
Endocrine Glands SupportingEndocrine Glands SupportingMammary FunctionMammary 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
• 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