PBL 3 Flashcards
What is blood?
A suspension of cells in a solute of water, water-soluble proteins and electrolytes.
What is plasma?
Anticoagulated blood from which the cellular components (RBCs,WBCs and platelets) have been removed by centrifugation.
It contains the coagulation proteins
What is serum?
The liquid in blood that has been collected without an anticoagulant.
The coagulation proteins have clotted and formed a precipitate along with the cellular components of the blood
What is plasma?
The liquid component of blood. It is made up of about 90% water with the rest being ions, proteins, nutrients and dissolved gases
What is the function of Plasma?
Responsible for maintaining blood pH and osmotic balance. Lipids, such as cholesterol, are also carried in plasma but must travel with escort proteins as they are not water soluble.
What are RBCs?
Red Blood Cells, also known as erythrocytes are specialised cells. They don’t have a nucleus or mitochondria and have a biconcave structure
What is the function of RBCs?
To travel throughout the body and deliver oxygen/CO2 to tissues
What are platetlets?
Aslo known as thrombocytes, platelets are cell fragments which are produced when large cells called megakaryocytes break into pieces, each ones making 2000-3000 platelets as it breaks apart
What is the structure of platelets?
Platelets are roughly disc shaped about 2-4 micrometers in diameter. Their cytoplasm contains granules with substances such as fibrinogen
What is the function of platelets?
They have a large role in blood clotting
What are WBCs?
White Blood Cells, also known as leukocytes are larger than RBCs and contain a normal nucleus and and mitochondria
What is the function of WBCs?
WBCs are primarily involved in immune responses
What is endomitotic synchronous replication?
Megakaryocytes grow and grow until eventually fragments come off.
What happens after damage to a blood vessel?
Immediate vasocontriction to slow blood flow
What is extanguination?
The action of draining a person, animal, or organ completely of blood
What happens after breakage of the endothelial cell barrier?
Recruitment of platelets from the circulation to form a plug
What is platelet adhesion?
When platelets interact with other cells. This is caused by collagen exposure
What is platelet aggregation?
When platelets interact with each other, forming clots
What does platelet adhesion lead to?
The activation of platelets
What does platelet activation follow?
stimulation by agonists such as ADP and thromboxane A2 interacting with surface repceptors or by direct interaction with the subendothelial matrix.
What change occurs in platelets (change in shape etc.)
platelets convert from a compact disc to an irregular sphere shape, their surface receptors become activated, and granules in the cytoplasm secrete their contents
How is the loose plug formed?
Other circulating platelets adhere to the initial layer of platelets
What is coagulation?
The mechanism that directly leads to the conversion of the soluble plasma protein fibrinogen to the insoluble rigid polymer fibrin
What is the clotting (or coagulation) cascade?
The mechanism by which fibrinogen is converted into fibrin
What are most activated coagulation factors?
Proteolytic enzymes which in the presence of cofactors cleave other factors in an ordered sequence
How is the intrinsic pathway activated?
Exposed collagen and other negatively charged components of the subendothelium
What does activation of factor XII lead to?
The sequential activation of factors XI, IX,VIII(cofactor),X and prothrombin
What leads to the activation of the extrinsic pathway?
Tissue factor complexes with factor VII leading to sequential activation of factors VII, X and prothrombin
What do both pathways result in?
The final common pathway, where activated factor X, in association with the cofactor Va in the presence of phospholipid and calcium, converts prothrombin into thrombin
How is fibrinogen converted into fibrin?
Thrombin splits the fibrinogen molecule and creates a polymer.
What is prothrombin time?
A measure of the function of the extrinsic pathway
What is the activated partial thromboplastin time?
A measure of the function of the intrinsic pathway
How is blood coagulation modulated?
Anti-thrombin, Proteins C and S and TFPI
How does anti-thrombin modulate blood coagulation?
Inhibits the terminal proteins of the cascade, particularly factor Xa and thrombin. Its activity is increased by interaction of heparin in the microvasculature nad on the surface of endothelial cells
How do proteins C and S modulate blood coagulation?
Protein C is a vitamin K dependent plasma protein which inactivates the cofactors Va and VIIIa and stimulates fibrinolysis. Protein C is converted to its active form by interaction with thrombin.
Protein S acts as a cofactor for protein C
How does TFBI modulate blood coagulation?
Tissue factor pathway inhibitor inactivates factor Xa and then the TFBI/Xa complex inhibits factor VIIa within the VIIa/ tissue factor complex.
When does fibrinolysis occur?
When damaged epithelium is repaired.
Why must the fibrin thrombus be removed?
To restore blood flow
What facilitates thrombus removal?
A fibrin-splitting protease, plasmin
What leads to the conversion of plasminogen to plasmin?
Release of tissue plasminogen activator (t-PA)
What does Release of tissue plasminogen activator (t-PA) lead to?
The conversion of plasminogen to plasmin and then clod breakdown.
What is circulating plasmin inactivated by?
α2- antiplasmin
What is the function of red blood cells?
To carry respiratory gases to the lungs
Where does oxygen go after the lungs?
Tissue where it is exchanged for CO2
What happens to RBCs before they leave the bone marrow?
They shed their nuclei
What is the advantage of the loss of RBCs nuclei?
Reduced weight and transformation into a biconcave disc shape with increased manoeuvrability
What is erythropoiesis?
The production of RBCs
What regulates erythropoiesis?
Erythropoietin
What is RBCs function dependent on?
The specialised protein haemoglobin
What does the normal adult haemoglobin molecule consist of?
four polypeptide chains- 2 α chains and two β chains. often notated as α2β2.
What is combined with each of the polypeptide chains in haemoglobin?
A ‘haem’ molecule which contains ferrous iron (Fe2+) and protoporphyrin
What forms the oxygen carrying part of the molecule?
The iron combines irreversibly with oxygen and thus haem forms the oxygen carrying part
What is the affinity for oxygen in haemoglobin like?
In the lungs haemoglobin has a high affinity for oxygen.
In the tissue haemoglobin has a lower affinity for oxygen in the tissues
The development of haematopoietic elements, the cells and other formed elements of the blood known as?
Haematopoiesis
What is Haematopoiesis?
The development of haematopoietic elements, the cells and other formed elements of the blood
What happens to bone marrow as people age?
The bone marrow in the peripheral bones becomes gradually replaced by fat.
Where are haematopoietic cells found?
Packed between fat spaces and bony trabeculae, or surrounding the vascular sinuses, meaning the mature cells can be released into the blood
How are different lineages of haematopoietic cells found?
Compartmentalised. E.g. Lymphocytes tend to surround small radial arteries while erythrocytes form islands around the sinus walls
Where is Erythropoietin synthesised?
Mainly by endothelial cells in the kidney
What is production of RBCs (erythrocytes) triggered by?
Tissue hypoxia
What is the role of the triage nurse?
To assess patients and determine an order of severity/urgency of the patients. They ensure that patients that need care first/most urgently receive this
What are the primary aims in treating a wound with severe bleeding?
to control bleeding
prevent/minimise the effects of shock
minimise the risk of infection
How should a wound with severe bleeding be treated?
A sterile dressing or a non-fluffy clean pad. If there is an object in the wound pressure should be applied on either side. A dressing that is tight enough to maintain pressure (but not restrict circulation) should be applied
Where are most growth factors produced?
Bone marrow
What is GMCSF?
A growth factor for general stimulation of hemopoietic stem cells
