Cardiovascular 2

Question 1

Examples of capillary types and where they are found

Answer 1

Continuous capillaries: joined by leaky junctions, ex. Muscle, connective, neural tissues (exception: BBB contain tight junctions instead)

Fenestrated capillaries: porous for fluid entry, ex. Kidney and GI

Sinusoids: modified wide, fenestrated capillaries with gaps between cells in bone marrow, liver, spleen

Question 2

Absorption, filtration and bulk flow definitions

Answer 2

Absorption = bulk flow into capillary
Filtration = bulk flow out of capillary

Bulk flow: mass solute movement due to hydrostatic + osmotic pressure gradient

Question 3

Plasma proteins

Answer 3

Albumin (carrier)

Globulins (clotting, enzymes and immuno)

Fibrinogens (clotting)

Transferrin (Fe3+ transport)

Question 4

Cellular elements of blood, functions and subtypes

Answer 4

RBC, WBC (lymphocytes, monocytes, neutrophils, eosinophils, basophils) and platelets

Erythroblast → reticulocyte (expels nucleus) → erythrocyte
Function: Transport O2/CO2
Regulated by: erythropoietin (EPO) in kidneys induced by HIF-1

Lymphocytes function: specific immune response
Monocytes → macrophages function: phagocytosis
Neutrophils function: ingestion of foreign substance/pathogens
Eosinophils: granulocytes release toxic compounds against invaders
Basophils (mast cells) release histamine

Platelets: derived from megakaryocytes and synthesis regulated by TPO from liver

Question 5

Iron/heme metabolism

Answer 5

Active transport (DMT1 H+ cotransport) of Fe in gut → transferrin (transported to liver to be stored with ferritin) → heme → Hb (bind 4 O2)

Hb has 4 heme groups (porphyrin ring + Fe)

Hb metabolized into bilirubin for excretion after RBC dies

Question 6

Hemostasis:

Answer 6

1) vasoconstriction - paracrine induced (5-HT released by platelets)

2) loose plug formation: activated platelets stick to exposed collagen and produce cytokines to upregulate platelets for plug formation (+ feedback)
Produce platelet activating factor (PAF) → thromboxane A-2 & 5-HT (serotonin) for vasoconstriction

3) coagulation cascade: exposed collagen + tissue factor → thrombin → fibrinogen → fibrin → clot
Intrinsic (collagen exposed) vs extrinsic (cell injury pathway) activate different factors which lead to prothrombin → thrombin

Question 7

Definitions of hemostasis, coagulation and fibrinolysis

Answer 7

Hemostasis: keeping blood inside damaged vessel

Coagulation = formation of a clot so that the damaged vessel can be repaired, it is a step in hemostasis

Fibrinolysis: tPA (tissue plasminogen activator) converts plasminogen → active plasmin which dissolves clot

Question 8

Prostacyclin function

Answer 8

Produced by healthy endothelial tissue - protects against unnecessary platelet aggregation