Exam #3_Semester 2 Flashcards
blood - general roles
Transport vehicle: long distance
Defense: B-cells and phagocytes
Homeostatic role
- buffering capacity: protein buffers; acid-base balance
- osmotic balance: ECF oncotic pressure
- heat distribution (disseminating heat load or conserving heat to core)
oncotic pressure
contribution made by proteins to overall osmotic pressure
multipotential hematopoietic stem cells
precursors to all cellular components of the blood (RBCs, WBCs, platelets)
- produced by bone marrow
- differentiate into myeloid precursors (RBCs and WBCs) and lymphoid precursors (lymphocytes - B’s, T’s, and NKC’s (natural killer cells))
functions of EPO (erythropoietin)
maintain constancy of HgB concentration
maintain constant of RBC mass
Ensure and speed recovery form hemorrhage
Note: great variation b/t individuals; diurnal fluctuations; higher at altitude (low PO2)
influences of EPO release
Hypoxia-inducible factor (HIF) synthesis is triggered by reductions in local PO2 and this is a function of:
o O2 carrying capacity: function of hemoglobin concentration (ex. anemia)
o O2 saturation: degree to which hemoglobin is saturated with O2
o O2 affinity: affinity of hemoglobin for O2 (factors that promote high affinity = low free O2 in plasma)
hemoglobin and glucose - HgB-A1c
erythrocytes, which contain hemoglobin, are entirely dependent on glucose to drive diffusion
Hgb can be irreversibly glycosylated with glucose (purely dependent on conc. of glucose in ECF), forming HgB-A1c
- does not affect function in terms of O2 binding
- marker of glycemic control
agglutinogens
cell surface glycosylated entities (sphingoipids) that define “blood type” phenotype
- all sphingolipids are glycosylated (have carbohydrates attached), but A and B groups have a single, additional group attached
- O group does not have an extra carbohydrate group attached
form of iron that can reversibly bind O2
ferrous form (Fe2+)
Note: ferric form (Fe3+) cannot bind O2
two things that affect blood O2 carrying capacity
- amount of O2 bound to Hgb - major contributor!
- depends on degree Hgb is saturated with O2 (ability to associate with 4 O2) which depends on PO2
- depends on amount of Hgb in system - partial pressure of O2 (amount of O2 dissolved in plasma) - minor contributor!
fetal Hgb (HgbF)
γ/a (gamma/alpha) – alpha 2, gamma 2 expression: has higher affinity for O2 than adult
adult Hgb (Hgb A1)
a/b (alpha/beta) - beta chain increases following birth (gamma decreases); alpha chain remains
- can be conjugated with glucose (Hgb-A1c)
adult Hgb A2
when alpha chain associated with delta chain (usually small amount)
P50 value for Hgb
partial pressure of O2 at which 50% saturation of Hb exists
deoxyhemoglobin
no O2 bound
- 2,3-BPG can bind more readily to this form
alpha thalassemia
defect in alpha subunits (should be very high in fetus)
Left with gamma subunits only (gamma 4) – called Bart’s Hemoglobin
• P50 of 3 mmHg PO2 (vs. 21 mmHg normally)
• Hb Bart’s has a very high affinity for O2 - will not let go of it
Devastating to newborn (fetus starved of O2)
Bart’s hemoglobin (Hb Bart’s)
Hb Bart’s has a very high affinity for O2 - will not let go of it
P50 of 3 mmHg PO2 (vs. 21 mmHg normally)
Devastating to newborn (fetus starved of O2)
- see in alpha thalassemia
methemoglobinemia
excess metHb (methemoglobin) - possesses oxidized iron in ferric state (Fe3+) instead of ferrous state (Fe2+) - Fe3+ state does not bind O2 (no reversible association occurs)
metHb typically present at 1% of total Hgb
Chemical agents can oxidize iron in Hb to ferric state and cause too much metHb = methemoglobinemia
effect of Hb mutation increasing affinity for O2
decreased P50 = increased affinity
- more O2 bound tightly to Hb = blood not releasing enough O2 to body = tissues starved of O2
effect of Hb mutation decreasing affinity for O2
increased P50 = decreased affinity
- less O2 bound to Hb = less saturation = lower blood oxygen carrying capacity = blood not supplying enough O2 to body
haptoglobin
“suicide” protein that is a weak binder of hemoglobin in plasma (versus bilirubin synthesis in liver and spleen)
- creates a non-reactive complex once bound to Hb
- low levels = elevated hemolytic activity since most bound with heme
Can iron be cleared by body?
no, iron is an element - we cannot metabolize it
body has not evolved mechanisms to clear excess iron
fluid compartments of body
ECF: consists of blood and interstitial fluid (ISF)
- Exchange with external environment mainly though ISF
- kidney is only organ in steady stage with blood
ICF: largest volume of fluid (2/3)
- in stead state with transcellular fluids
secretion
active process of moving substances across membrane
excretion
ridding from body
substance handling - how are substances introduced into our systems and leave our systems?
ingested
produced via metabolism
consumed via metabolism
excreted
balance concept
To maintain balance in our systems (fluid volume homeostasis and electrolyte homeostasis):
substance amount produced and ingested = substance amount consumed and excreted
intake = output
“mu”
normal
ex. mu natremic state = normal homeostatic state for Na
types if nephrons
Superficial nephrons: have glomerulus/bowmen’s capsule at the more distal regions of the cortex
• Short loop of Henle – does not extent far into medulla
Mid-cortical nephrons:
• Loop of Henle is a bit longer
Juxtamedullary nephrons: glomerulus/bowman’s capsule very close to the medulla (still in cortex)
• Very lengthy loop of Henle that dips far into the medulla