Transcript Thrombocytes (Platelets)

Thrombocytes
(Platelets)
&
Plasma
Structure
• Fragments of giant cells
(megakaryocytes) (each produces
b/t 5-10,000 platelets)
• Pieces break off these
cells in bone marrow
• Enter circulation – live for approx.
1 wk.; destroyed by spleen & liver
• Disk-shaped, w/o nucleus
• ½ the size of an RBC
• Release serotonin to contract
blood vessel walls.
Function
• Normal platelet count –
130,000-360,000/mm³
• Stem blood flow (hemostasis) 2 ways:
1. Form a platelet plug
2. Initiate the clotting
process
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 adhere
5. Eventually platelet plug is formed & bleeding stops
Clotting Process - Coagulation
• Cascade effect series of steps,
each one
activating the
next step
• Extrinsic clotting –
occurs when b.v.
are damaged; platelets
1st release serotonin
Hemostasis
• Blood coagulation uses biochemicals
called clotting factors.
– Coagulants vs. anticoagulants
• During an injury coagulants prevail.
• Final portion of hemostasis is conversion
of protein fibrinogen into insoluble protein
threads called fibrin.
– Fibrin forms network of threads that attaches
to exposed surfaces. Prevents blood loss.
Animation
• hemostasis animation
Blood Clots
• Thrombus – blood clot that forms in a b.v.
abnormally
• 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. transport
2. maintain fluid balance
3. maintain pH
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 – Accounts for 36%
of all plasma proteins
- transports lipids & vitamins
3. Fibrinogen – Accounts for 4% of all
plasma proteins
- responsible for blood clotting
Other Substances
Plasma also contains:
• nonprotein nitrogenous substances –
amino acids, urea, uric acid
• 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
• Determined by genes
• Determines blood type
• Possible antigens – A or
B
• Antibody – protein in
plasma
• 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 – RBC’s burst,
hemoglobin released
• 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)
• Termed Rh+
• Remaining 15% of humans don’t have this
protein
• Termed Rh• Rh- individuals cannot receive Rh+ blood
Erythroblastosis Fetalis