Comparative Vertebrate Physiology

Blood and hemodynamics

Blood composition Plasma and formed elements Formed elements

Erythrocytes, leukocytes, platelets Hematocrit

<45% anemia (O2 delivery problems) >45% polycythemia (circulation problem)

Plasma

WBC’s, platelets

RBC’s

Plasma Contents

90% water Protein (albumin) Fats, amino acids, salts, gases, enzymes,

hormones Narrow osmolality range in mammals only

Erythrocytes Most verts. have a nucleus (exceptions some fish, amphibians, humans) Shape (oval in Aves,spherical, elliptical to biconcave disc in mammals)

Leukocytes Protection against invasion Granulocytes

Neutrophils, eosinophils, basophils

• Agranulocytes• No cytoplasmic granules• Lymphocytes, monocytes

Platelets Fragments of bone marrow

(megakaryocytes) Clotting function Age quickly (enucleate)

Erythropoiesis1. Ribosome manufacturing

2. Hb synthesis and accumulation

3. Nucleus and organelle ejection

Erythropoiesis

Rheology Relationship between pressure and flow

of fluid 1. Viscosity

Rheology Flow rate = 1/viscosity

Rheology Flow rate is directly proportional to

differences in pressure

Rheology Flow rate is indirectly proportional to

vessel length

Rheology Flow rate is directly proportional to the

fourth power of the radius of the vessel

Hemodynamics Rate of blood flow slowest in highest cross sectional

areas Functional significance

Blood flow Laminar flow

Continuous (small vessels) Pulsatile (large vessels)

Blood flow Turbulent flow

Definition (obstruction, sharp turns, high flow rate)

Occurs after aortic and pulmonary valves

Blood flow

Reynold’s number determines whether flow is laminar or turbulent

Re Directly proportional to velocity Directly proportional to the radius Inversely proportional to viscosity

Blood flow