Primary Hemostasis

• Tunica intima (inner tubular cavity) made of simple squamous called endothelium
• Tunica media (middle layer cavity) ~Thickest coat ~composed of smooth muscle and elastic fiber
• Tunica adventitia (outer layer cavity) ~Consist of fibrous tissue ~Supplies nutrient to the tissue of the wall
• Arteries: carries the blood from heart to capillaries
• Veins: Return blood to heart from capillaries
• Capillaries: Thinnest walled and most numerous of the blood vessel
• When small vessels (artereole, venule or capillary) is injured, contraction occurs to control bleeding. This is VASOCONTRICTION.
• Angiotensin -Affects the movement of fluid across the endothelium
• Bradykinin -Inflammation
• -Injured vessel -Initiated by serotonin and Thromboxane A2 -Quickly cuts down on blood loss -Helps platelets and coagulation factors to come into contact with each other

  VASOCONTRICTION
• Angiotensin- Affects the movement of fluid across the endothelium
• PLATELETS -smallest of the formed elements in blood -a disk-shaped -2-3 um in size -formed from fragmentation of -megakaryocytes in the bone marrow -trigger and control blood coagulation
• Sl units is 150-450 x 10^9
• Conventional units is 150,000-450,000/uL
• VWF - is formed in "endothelial cells"
• DTS or Dense tubular system provides a site for Calcium sequestration and localization of enzymes needed for prostaglandin synthesis.
• OCS or Open canalicular system provides a passage for externalization of pit secretory products
• GP1a (binds collagen)
• GP 1b (binds VWF)
• GP IIb - Illa (binds fibrinogen)
• 1. Maintains platelet integrity. 2. Receive and transmit stimuli triggering pit responses.

  Peripheral Zone
• 1. Serve as cytoskeletal elements of the plt. 2. Maintain the discoid shape of the plt. 3. Form contractile system 4. Microfilaments in clot retraction

  Sol-gel zone
• 1. Responsible for metabolic activities of the platelet.

  Organelle zone
• 1. DTS provides a site for Calcium sequestration and localization of enzymes needed for prostaglandin synthesis. 2. OCS provides a passage for externalization of pit secretory products

  Membranous System
• Microfilaments: Actin and Myosin
• Microtubules: Tubulin
• ALPHA GRANULE DEFICIENCY Gray platelet syndrome
• DENSE GRANULE DEFICIENCIES CHE-CHEdiak Higashi syndromes

  WAS-Wiskott-Aldrich Syndrome HER-HERmansky-Pudlak
• ACTIVATION

  Morphologic and functional changes in platelets
• ADHESION

  Plts roll and cling to non-platelet surfaces GP1a (binds collagen) GP 1b (binds VWF) -GP IIb Illa (binds fibrinogen) - Occurs in the presence of VWF
• AGGREGATION - Platelet attachment to each other -Required fibrinogen and Calcium Platelet Plugs form -Secretion of all pit contents
• SECRETION - Plts discharge the contents of their granules

  -Occurs during adhesion and aggregation a. Alpha granules b. Dense granules
• Alpha granules -consist of Platelet factor, Platelet Derived Growth Factor (PDGF), Fibrinogen, V, VWF, Thrombospadin, Albumin, Fibronectin
• Dense granules C-alcium A-denosine Diphosphate (ADP) S-Serotonin
• Serotonin- Affects blood pressure regulation
• Aspirin inhibit cyclooxygenase
• TXA2 promotes VASOCONTRICTION and stimulate PLATELET SECRETIONS