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