Chapter 15 Chapter 15 Puerperium and Lactation Puerperium and Lactation AVS 222 AVS 222
Dec 16, 2015
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