Platelets And Capillaries 10/4 Flashcards
3 functions of platelets
- Monitor blood vessel integrity
- Clot formation
- Tissue repair
What stimulates the maturation of a megakaryoblast to a megakaryocyte?
Thrombopoeitin from liver & kidneys
By stimulating endomitosis
What are the components of the platelet structural zone (3)?
Microtubules
Actin
Myosin II
What are the 2 components of the membrane systems?
- Open canalicular system - forms from platelet demarcation channels. Facilitates release of granule contents
- Dense tubular system - storage of Ca2+ ions. Not connected to surface
What three things does the organelle zone contain centrally?
Mitochondria
Glycogen
Granules
What do alpha granules contain? (5)
Fibrinogen
Coagulation factors
Plasminogen
Platelet derived growth factor
Tissue growth factor
What do delta granules contain?
ADP
serotonin
Histamine
What do lambda granules contain?
Lysosomal hydrolases
What are the glycogen granules used for?
Energy source.
Which protein in the glycocalyx is the receptor for Vonwillebrand factor?
Gp1b
What is the function of seratonin?
Vasoconstriction
What do platelets bind to on damaged endothelial cell basal lamina?
Type IV collagen via actin derived pseudopods
What is the function of ADP released from delta granules?
attracts more platelets, stimulates degranulation
What is released from the PM that promote aggregation, degranulation, and vasoconstriction?
Thromboxane A2
What is released from phospholipids in the PM to synthesize arachadonic acid?
Phospholipase A2
Blocked by cortisol and saids
What converts fibrinogen converted to fibrin and where does this happen?
Thrombin
On the glycocalyx
What does the injured endothelium release to convert plasminogen to plasmin?
t-PA (tissue plasminogen activator)
What are capillaries composed of? (2)
- Single layer of simple squamous endothelium
2. Basement membrane
What 2 prothombogenic agents does the injured endothelium secrete?
- Von willebrand factor: platelet adhesion and activation
2. Tissue factors (VII): blood coagulation
What does the injured endothelium secrete to stimulate smooth muscle contraction and proliferation of endothelial cells and fibroblasts to REPAIR the vessel?
ENDOTHELINS (peptide hormones)
What are the 2 antithrombogenic agents that intact/normal endothelium secretes?
- Prostacyclin (PGI2): inhibits platelet adhesion
2. Nitric oxide (NO): inhibits wbc adhesion
