Blood Physiology

Blood is that part of extracellular fluid within

 the cardiovascular system

Blood forming

    During animals’ evolution, extracellular fluid 

was gradually shaped from the age-old time 

with ocean which was mainly salty solution. At 

last, extracellular fluid was differentiated 

into plasma and interstitial fluid and blood came 

from plasma and cells.

The role of blood in internal environmental 

homeostasis

    

Blood, the most active component in 

extracellular fluid, display functions as follows:

         

(1) transportation;

         

(2) pH value buffer;

         

(3) temperature or thermal maintenance;

         

(4) immunity and defence

I. Blood composing Blood composing: plasma + blood cells

Hematocrit:

   blood cells occupies the percentage of total blood volume. 

   normal value

   male: 40-50%

   female: 37-48%

   newborn: 55%

Chemical component of plasma :

Water: > 90%

Small molecule: 2%, it is electrolytes, nutriment, metabolic products, hormone, enzyme,etc.

Protein: 60-80 g/L, plasma protein include albumin (40-50 g/L), globulin (20-30 g/L,α1-, α2, β-, γ- ) and fibrinogen. Most of albumin and globulin made from liver. A/G and clinic.

Function of plasma protein:

    (1) transportation, (2) nutrition, (3) forming colloid osmotic pressure, (4) coagulation and anticoagulation, (5) pH value buffer, (6) immunity (globulin) . 

II. Physical and chemical

   characteristics of blood:

Specific gravity: total blood (1.050-1.060) more influenced by red blood cells;  plasma (1.025-1.030) more influenced by plasma protein; RBC (1.090-1.092) more influenced by Hb.

Viscosity:

      Blood relative viscosity (4~5) mainly depends on the    numbers of red blood cells.

      Plasma relative viscosity (1.6~2.4) is mainly involved in plasma protein

Plasma osmotic pressure is 300 mmol/L or 770kPa

     (1) Crystal osmotic pressure results from NaCl and modulates  water distribution between inside and outside of cells.

     (2) Colloid osmotic pressure results from albumin and regulates water distribution between inside and outside of capillary.

Plasma pH value is about 7.35~7.45, and usually buffer systems are NaHCO3/H2CO3 (20:1), protein salt/protein, Na2HPO4/ NaH2PO4, Hb salt/Hb, HbO salt/ HbO2, K2HPO4/ KH2PO4, KHCO3/H2CO3, etc [lungs and kidney mainly regulate Plasma pH value ].

III.Blood Cells:

Blood cells are erythrocyte (red blood cell, RBC), leukocyte (white blood cell, WBC) and thrombocyte (platelet, P).

The  forming processes of erythrocyte (red blood cell, RBC), leukocyte (white blood cell, WBC) and thrombocyte (platelet, P) originating from hematopoietic stem cells are hemopoiesis.

Transfer of blood cells forming place:

    yolk sac hemopoiesis (early embryo period) → liver and spleen (second embryo month) → marrow↑and liver, spleen↓ (after fourth embryo month) → marrow (fetus birth time) and liver, spleen as complementary role.

    During adulthood (after 18), red marrow (flat bones, e.g. vertebra,ilium, sternum, rib, skull and long bone ending) rather than yellow marrow has hematopoietic functions.

1. Hemopoietic,process and  hemopoietic stem cells : Hemopoietic process

    Stage one: Hemopoietic stem cells

    self renewal, steady numbers, active 

differentiation. 

    Stage two: committed progenitors

    

directional differentiation (CFU-GEMM, 

CFU-E, CFU-

    

GM, CFU-MK, CFU-TB).  [CFU: colony- 

forming unit.

    Stage three: precursors

    morphologic occurrence of various original blood cells.