ANATOMY AND PHYSIOLOGY - Blood Flashcards
- Erythrocytes - Thrombocytes and Coagulation - Leukocytes - Blood types and transfusions
What are the three main plasma proteins?
Albumin
Fibrinogen
Immunoglobulins (antibodies)
Where are albumin and fibrinogen plasma proteins produced?
Albumin and fibrinogen are produced in the liver
Where are immunoglobulin plasma proteins produced?
Immunoglobulins are produced by B-lymphocytes
What are the three blood cell types?
Erythrocytes
Leukocytes
Thrombocytes
What is the structure of erythrocytes?
Erythrocytes are anucleated biconcave discs with four haemoglobin binding sites
What is the function of erythrocytes?
The delivery of O2 via haemoglobin and removal of CO2 from the tissues
What is erythropoiesis?
Erythropoiesis is the process which produces erythrocytes through the development from erythropoietic stem cells into mature red blood cells
Describe the physiologcial regulation of erythropoiesis?
Decreased O2 delivery to the kidneys stimulates the production and secretion of the erythropoietin (EPO) hormone into the bloodstream. This hormone stimulates erythropoiesis
Where are erythrocytes produced and how does this differ as the animals ages?
Foetus: erythrocytes are produced in the liver, spleen and bone marrow (all)
Young animal: erythrocytes are produced in the bone marrow (all)
Adult animal: erythrocytes are produced in the bone marrow (red marrow)
What is haemolysis?
The breakdown (lysis) of erythrocytes
Describe the process of extravascular haemolysis
Erythrocytes are lysed outside of the blood vessels and engulfed by macrophages in the bone marrow (domestic animals) or the liver (birds). The erythrocytes will eventually be regenerated/recycled
Describe the process of intravascular haemolysis
Erythrocytes are lysed inside the blood vessels. Haptoglobin proteins in the blood bind to haemoglobin in the bloodstream and are quickly cleared from the bloodstream via the liver. The remaining erythrocyte structures are engulfed by macrophages and eventually regenerated/recycled
Where do non-circulating erythrocytes accumulate?
Spleen
Define haemostasis
Haemostasis is the spontaneous arrest of bleeding from a ruptured vessel
What are the three physiological haemostasis processes?
Vascular response
Platelet plug formation
Coagulation cascade
Describe how the vascular response achieves haemostasis
The contraction of the smooth muscle (vasoconstriction) of the damaged blood vessel to prevent further loss of blood through the damaged endothelium
How does the vascular response differ depending on the severity of the damage to the blood vessel endothelium?
More damage to the endothelial cells (e.g. crush injury) = more vasoconstriction, less blood loss
Less damage to the endothelial cells (e.g. cut injury) = less vasoconstriction, more blood loss
Describe the process of platelet plug formation
- When damage to the blood vessel endothelium occurs, platelets move out of the blood vessel and are activated through coming into contact with collagen
- Activated platelets contract causing exocytosis of enzymes and growth factors
- One of these enzymes converts arachidonic acid into thromboxane A
- Thromboxane A activates more platelets
- Activated platelets aggregate together as well as to Von Willebrands factors present on the blood vessel endothelium - forming a platelet plug at the site of blood vessel injury
Describe the physiological regulation of platelet plug formation
Healthy blood vessel endothelium secretes an enzyme which converts arachidonic acid into prostacyclin which inhibits the formation of platelet plugs
Give an example of a common haemostatic platelet disorder
Von Willebrands disorder
How does aspirin act as an anti-clotting agent?
Aspirin inhibits thromboxane A production in platelet plug formation
What is the difference between the intrinsic and extrinsic coagulation pathway?
Intrinsic: all of the factors required are contained within the bloodstream
Extrinsic: external tissue factors can enter the break in the bloodstream and bypass the initial steps for the intrinsic pathway
Describe the process of the final common pathway (the final stage of the coagulation cascade)
- Extrinsic or intrinsic coagulation pathway stimulates the conversion of prothrombin to thrombin
- Thrombin activates factor 13 as well as converts soluble fibrinogen into insoluble loose fibrin threads
- Activated factor 13 connects the loose fibrin threads to form and stabilise a fibrin network
- Fibrin network contracts, pulling the erythrocytes together (erythrocytes go from a biconcave to tetrahedral shape) to form a blood clot
What are the two stages of clot dissolution?
Clot retraction
Fibrinolysis
