Physiology of pregnancy + Space medicine Flashcards
functions of the following hormones released by the placenta during pregnancy
HCG
Progesterone
Estradiol
Relaxin
Human chorionic gonandotropin (HCG): releases progesterone and estradiol
Progesterone: controls uterine smooth ms; also affects renal function and heart function
Estradiol impacts uterine contractility in an opposing manner to progesterone; and it influences blood vessel function, and it activates RAAS
Relaxin only produced in an existing pregaz; affects blood vessel function and stimulates ADH secretion
cardiovascular response to pregnancy (what happens to the following:
TPR
BV
CO
MAP
progesterone/estradiol levels)
Increased blood volume
Increased cardiac output
Decreased mean arterial pressure
Decreased total peripheral resistance
Increased progesterone/estradiol
what happens during the 1st and 2nd trimester as it relates to the decrease in TPR?
describe the concept of arterial underfill
1st trimester: Arterial underfill: vessels are vasodilating, which increases vascular capacity, and increasing filling capacity
2nd trimester: continued arterial vasodilation; increased placental size is accompanied by increase in vasculature, and change in reactivity of blood vessels to circulating substances
Mechanisms of altered vessel reactivity
Increased synthesis of vasodilators from endothelium
Increased vessel reactivity to vasodilators
Decreased vessel reactivity to vasoconstrictors
Decreased myogenic response to pressure
what are the changes to the following during early pregnancy?:
CO, SV, HR
Progesterone stimulates what changes to heart morphology?
Changes in cardiac function: increased cardiac output, stroke volume, HR
Physiological hypertrophy: when heart wall hypertrophies (reversible)
why does your arterial blood pressure decreases early in pregnancy?
what are the changes to venous blood pressure in the upper vs lower extremities?
Drop in mean arterial pressure is due to the fact that the decrease in TPR is greater than the increase in CO
venous blood pressure in upper extremities doesn’t change, increases in the lower extremities
what promotes the increase in blood volume during pregnancy? (hint: bloody salt water)
Increase in blood volume that occurs during pregnancy is driven by:
Na and water retention, which increases plasma volume
RBC production, which increases RBC volume
what is the effect of the RAAS on blood volume expansion during pregnancy?
what increases first, RBC volume or plasma volume?
how could you get “physiological anemia” when you have an increase in blood volume during pregnancy?
Blood volume increases about 50% above non pregnant values
Increase in plasma volume occurs before increase in red blood cell volume
Physiological anemia: decrease in hematocrit due to increased plasma volume
4 ways the blood volume expansion during pregnancy is important
define autotransfusion
Fills expanded vascular system via arterial underfilling; secondary to systemic vasodilation
Protects against blood loss at delivery through vaginal delivery or C section or autotransfusion
Protects against thrombotic events
Maintains uterine/placental perfusion
Autotransfusion of laboring uterus – return of uterine blood back to the heart
what are the hematologic changes that cause pregnancy to be considered a hypercoagulable state?
whatis the benefit of decreased blood viscosity?
Decrease in hematocrit (driven by physiological anemia and decreased blood viscosity)
-Decreases viscosity of blood helps with decreasing resistance and increasing flow
Coagulation factors important to balance to prevent blood clotting (because increased coagulation factors increases risk of blood clotting)
Platelet aggregation increases; may increase risk of deep vein thrombosis
Effects of pregnancy on the uterus
Growth and metabolism
Increases vascularization
Uterine blood flow
changes in renal function during pregnancy
Increased filtered load
Increased reabsorption
Increased excretion
(the whole point is to retain sodium in the presence of plasma volume expansion)
what drives the increase in renal plasma flow?
what elase increases along with RPF?
Increase in renal plasma flow (result of increase in arterial vasodilation; mainly thru relaxin-mediated release of nitric oxide, estradiol can increase prostacyclin)
Increase in GFR
mechanism for increased sodiuma dn water reabsorption
what happens to the effects on ANP?
Increased ENAC channels and sodium transporters
Effects of ANP are inhibited so we can retain sodium and water
