Formed Elements in Blood
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Transcript of Formed Elements in Blood
Hemopoiesis Production of most formed elements found
in the blood
First occurs in the yolk sac of an embryo and later in the liver, spleen, thymus, and lymph nodes of a fetus.
Last three months before birth, red bone marrow becomes primary site of hemopoiesis and continues as the source of blood cells after birth and throughout life.
Erythrocytes
A.k.a. red blood cells (RBCs)
Amount in blood: 4-6 million
Life Span: 120 Days
Biconcave disc without nucleus
Function: transport oxygen in hemoglobin
Leukocytes
A.k.a. white blood cells (WBCs)
Amount in blood: 4,000 to 10,000
Life Span: 13-20 Days
Nucleated? Yes
Function: fight viruses and bacteria-immunity-move out of capillaries to site of infection
Classified as granular or agranular
Granulated - Neutrophil Respond 1st to
bacterial invasion
Function: Phagocytosis (engulf bacteria) and releasing enzymes (i.e. lysozyme)
Multi-lobed nucleus
54 - 62% of white cells present
Granulated - Eosinophil orange histamine granules
– released during allergic reactions
Effective against certain parasitic worms
Helps to detoxify foreign substances
Secretes enzymes that break down clots
1 - 3% of white cells present
Agranulated cells - lymphocytes
Large nucleus
Makes antibodies
Fights viruses
B cells, T cells, and natural killer (NK) cells
20 - 40% of white cells
Platelets - thrombocytes Amount in
blood: 150 to 400,000
Life Span: 5-9 Days
Nucleated? In bone marrow – not peripheral blood
Function: enable clotting
Blood Clotting A.k.a. coagulation
Clotting factors: Ca2+, enzymes made by liver cells, and various molecules associated with platelets or released by damaged tissues
Three stages:1. Prothrombinase is formed.2. Prothrombinase converts prothrombin into
the enzyme thrombin.3. Thrombin converts soluble fibrinogen into
insoluble fibrin. Fibrin forms the threads of the clot.
Blood Vessel Repair Once a clot is formed, it plugs the ruptured
area of the blood vessel and thus stops blood loss.
Clot retraction- consolidation or tightening of the fibrin clot. Fibrin threats attached to the damaged
surfaces of the blood vessel gradually contract as platelets pull on them.
As the clot retracts, it pulls the edges of the damaged vessel closer together.
Fibroblasts form connective tissue. Endothelial cells repair vessel lining.