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Thrombocytes(Platelets)
&Plasma
Structure
• Fragments of giant cells(megakaryocytes) (each producesb/t 5-10,000 platelets)
•
• Enter circulation – live for approx. 1 wk.; destroyed by spleen & liver
• Disk-shaped, w/o nucleus• ½ the size of an RBC
Function
• Normal platelet count – 130,000-360,000/mm³
• Stem blood flow (hemo-stasis) 2 ways:1. 2.
Platelet Plug Formation 1. B.V.damaged 2. Some blood escapes 3. Platelets adhere to each other & rough
surfaces 4. When platelets come
in contact w/collagen from connective tissue, they develop spiny projections; helps them adhere5. Eventually platelet plug is formed & bleeding stops
Clotting Process - Coagulation
• Cascade effect -
• Extrinsic clotting –occurs when b.v.are damaged; platelets
1st release serotonin
Blood Clots
• Thrombus –
• Embolus – blood clot or fragment of one that dislodges & travels to major organ
Plasma
• Clear, straw-colored fluid; matrix of blood
• 92% water• Functions:
1. 2. maintain fluid balance
3.
Contents of Plasma• Contains 3 plasma proteins (all produced in
the liver):
1. Albumin – accounts for 60% of all plasma proteins - maintains osmotic pressure (keeps concentration of H2O & solutes in plasma stable
- example – a decrease in albumin causes cells to lose H2O; it collects in interstitial spaces (b/t cells) & causes edema
Plasma Proteins
2. Globulins –
3. Fibrinogen – Accounts for 4% of all plasma proteins- responsible for blood clotting
Other Substances
Plasma also contains:• nonprotein nitrogenous substances –
• electrolytes – release ions when dissolved in H2O; maintain osmotic pressure & pH;include Na, K, Cl, Ca Mg, bicarbonate, PO4 & SO4 ions
Blood Types
• Antigen – protein on surface of RBC’s• • Determines blood type• Possible antigens – A or
B• Antibody –
• Possible antibodies – A or B
Human Blood Types
Intrinsic Clotting (Agglutination)
• Occurs when antigen comes in contact with foreign antibody (example – b.t. A receiving a transfusion of b.t. B)
• Effects –
• Symptoms – anxiety, difficulty breathing, chest pain, pain in neck & lumbar area
Rh Blood Group
• 85% of humans have an additional protein on their RBCs; called the Rh factor
• Named after the species of monkey it was discovered in (Rhesus)
• • Remaining 15% of humans don’t have
this protein • • Rh- individuals cannot receive Rh+ blood
Erythroblastosis Fetalis