Primary Homeostasis (Final Exam) Flashcards
hemostasis defintition
process by which the body spontaneously stops bleeding and maintains blood in the fluid state within the vascular compartment
Homeostasis strives to keep the body in blance and maintain homeostasis
an imbalance causes
bleeding that doesn’t stop = hemorrhage
too much coagulation = thrombosis
primary hemostasis
- injury
- vasuclar phase
- platelet adhesion
- platelet aggresgation
- temporary plug
second hemostasis
- coagulation cascade
- fibrin clot forms
- healing
- fibrinolysis
major systems involved with hemostasis
vascular
platelets
coagulation
fibrinolytic
minor systems
kinin
serine proteas
complement
primary homeostasis
vascular phase and components
platelet plug formation
secondary hemostasis
coagulation factors form fibrin clot
fibronolysis
blood vessel
smooth, continious endothelial lining
- “nonwettable”
- facilitiates blood flow
Under normal conditions, hemostasis is prevent by
- endothelium as a physical barrier
- endothelial secretions of platelet inhibitors prostacyclin (PGI2) and Nitric Oxide (NO)
blood vessel layer
inside out:
Tunica intima
Tunica media
Tunica adventitia
tunica initima
- broad flat endothelial cells
- supports migration of cells
- subendothelium = collages, connective tissue, fibroblasts
Tunica media
- elastic tissue and snooth muscle
- vasoconstriction
Tunica adventitia
- connective tissue
- support
vasoconstruction
smooth muscle constricts
diverts blood flow around damaged vasculature
Breached blood vessel
- sub-membranous collagen is exposed
- platelet and coagulation factors are able to be activated = contact activation
Blood vessels secrete cytokines
ADP releases from endothelium
- promotes platelet aggregation (platelet plug)
Tissue thromboplastin (aka tissue factor / factor III) released from vessel wall
- initiaties fibrin formation through extrinsic cascade (initiates secondary hommeostasis)
Platelet facts
normal count: 150,000-400,000 micro L
30% are sequestered in spleen as functional reserve
Aged or non-viable platelets are removed by the spleen and liver
platelet function
adhesion and aggregation
Coagulation factors and proteins absorb into platelet
open canalicular system
helps in releasing granules
glycoprotein on surface coat called
Glycocalyx
- Contains blood group and tissue compatability antigens
Surface of platelet help with fibrin clot formation
type V and VIII
former demarcation membrane of parent
membrane
Platelet membrane
Phospholipids
Adhesion receptors
aggregation receptors
Phospholipids (platelet membrane)
- helps make platelet sticky
- Platelet 3 (PF3) - allows assembly of vitamin K dependent coagulation –> secondary homeosasis
Adhesion receptors
GP1b - Von Willebrand factor (vWF)
Fibronectin
Aggregation receptors
- GPIIb/Illa (normally inaccessible) - binds fibrinogen
- ADP
- Thrmobin
- Epinephrine
- Collagen
- Thromboxane A2 (TXA2)
- Serotonin
Sol-gel zone , Platelet
Function: help support membrane
Cytoskeleton contains:
- Microfilaments and microtubiles
contractile proteins: actin, myosin, actomyosin and “thrombosthenin”
Capable of contracting within seconds
platelet - organelle zone
Function: Metabolic reserve
Contains storage granules
Aid in Prostaglanding/Thromoxane A2 synthesis
Dense tubular system
Mitochondria
- 10-16 / platelet
- has glycogen (storage form of glucose)
most numerous granules
alpha, up to (200/plt)
Alpha granules
PLT specifc proteins (stays on membrane post secretion)
- platelet factor 4 - inhibits heparin
- beta-thromboglobulin and platelet derived growth factor - promotes vessel smooth muscle vessel
- thrombospondin - promoties PLT-PLT interaction
- factor V - coagulation
alpha granules
Plasma protiens
become soluble post secretion
- albumin
- vWF - promotes adhesion
- Fibrinogen, factor V, Factor VIII, high molecylar weight kininogen - coagulation
- plasminogen - fibrinolysis
- a2 antiplasmin - inhibits fibrinolysis
dense granules
- 2-10/plt
- nonmetabolic ATP
- nonmetabolic ADP - promotes aggregation
- calcium - regulates PLT activation/aggregation
- seretonin - vasconstriction
lysosomes
proteases - breaks down protein/peptide
hydrolases - used water to break chemical bond
bactericidal enzymes
platelet plug - adhesion (GPIb-vWF)
Reverseible process where platelets stick to foreign surfaces
Subendothelium is exposed due to injury
- composed of adhesive molecules: collagen, vWF and others
vWF attaches to platelet membrane GPIb = adhesion
platelet plug shape
platelets become activated and changes from circle disc to “spiny” spherepseudopods
Shape change allows GPIIb/IIIa and platelet factor 3 (platelets thromboplastin) to be accessible
Platelet plug - aggregation - 1st wave
GPIIb/IIIa-fibrinogen-GP IIb/IIIA
Energy dependent process - requires ATP
Fibrinogen binds the now usable GPIIb/Illa receptors
Briges of fibrinogen and Ca2+ form between GPIIb/Illa receptors on adjacent platelets = aggregation
platelet plug secretion - 2nd wave
secretion requires a strong stimulus
- thrombin (from coagulation) is great candidate
platelets secrete their granueles
- promote
