microcirculation

• microcirculation: is the blood flow through blood vessels smaller than 100 micrometer (arterioles, capillaries, and venules)
• blood flow coming from the arterioles to the capillaries, at the capillaries we have the exchange and then leave to the venules.
• function of the microcirculation: transporting blood cells and substance to/from the tissues. 
• vasomotion: is theregulationg of blood flow to the capillaries depend on the tissue need by opening and closing of the precapillary sphincter
• oxygen (O2) is the most important factor affects precapillary sphincter, when the tissues need O2, the precapillary will dilate and relax vice versa. 

blood cells

• blood is a fluid connective tissue because of its mesenchymal origin and low cell to liquid intercellular substance (blood plasma)
• in human adult about 5 liter \(7-8%) of the weight.
• blood made up of two parts: formed elements (blood cells) and plasma
• plasma: the liquid in which formed elements suspended 

pathology of WBCs:

• leukopenia: is a decrease in white blood cell number. its a characteristics of the initial stage of viral infection. it may also be due to other condition.
• leukocytosis: is an increase in the number of leukocytes, principally neutrophils, and it may occurs as a response to bacterial infection.
• leukemia: is a pathologic increase in number of WBCs. the term denotes a type of neoplastic disease.