Week 7 (haematology and lymphatic system) Flashcards
What are the key components of the blood?
Blood plasma
Platelets
Proteins
Water
What are the key functions of blood?
Transportation of oxygen, carbon dioxide, nutrients, hormones, heat and waster products.
Regulation of pH, body temperature and water content of cells.
Protection: clotting, immune response, blood proteins
What is haematopoiesis?
The process by which the formed elements of the blood develop.
How many cells in the bone marrow are haematopoietic stem cells?
0.05-0.1%
What are haematopoietic stem cells?
Cells that are able to reproduce themselves, proliferate and differentiate into cells that give rise to blood cells.
Describe red blood cells
Biconcave discs with a diameter of 7-8um.
Plasma membrane is strong and flexible which allows cells to squeeze through narrow blood capillaries.
No nucleus or other organelles.
Cannot reproduce or carry out extensive metabolic activities.
Describe the physiology of RBCs
Highly specialised for oxygen transport.
All internal space available for oxygen transport as no nucleus.
Lack mitochondria and generate ATP anaerobically so do not use up oxygen.
Large surface area for diffusion of gas molecules.
Name the functions of RBCs
Transportation of carbon dioxide
Transportation of oxygen
Regulation of blood flow and blood pressure
Name the enzyme that is contained with RBCs
Carbonic anhydrase
What does carbonic anhydrase do?
Catalyse the conversion of carbon dioxide and water into carbonic acid, which then dissociates into H+ and HC03-.
How long can RBCs survive for?
Approx 120 days, due to damage to plasma membranes from moving through narrow capillaries.
Why can’t RBCs synthesis new components?
Due to lack of nucleus and other orgnelles.
Where does RBC breakdown occur?
In the liver and spleen, with breakdown products being recycled and reused in a number of other processes.
Explain the formation of erythropoiesis
- begins in the bone marrow with a precursor cell.
- proerythroblast divides several times to become a reticulocyte, which ejects its nucleus.
- reticulocytes leave the bone marrow and enter the bloodstream.
- reticulocytes develop into red blood cells within 1-2 days of their release from the bone marrow.
Describe the control of erythropoiesis
Stimulus = hypoxia
Hypoxia stimulates the kidneys to increase the release of EPO.
EPO increases production of pro-erythroblasts in the bone marrow.
Production of RBCs increases = increased oxygen delivered to tissues.
What does blood doping do?
Increase the number of circulating red blood cells and haemoglobin in the body.
How does blood doping work?
Administration of erythropoietin mimics natural release from kidneys to stimulate increased RBC production.
Increase in circulating RBCs allows increased oxygen carrying capacity and delivery to muscles.
This improves aerobic capacity, endurance and performance.
How does altitude training work?
At high altitudes, oxygen content of the air is lower.
This stimulates release of erythropoietin from the kidneys which increases RBC production.
Increase in circulating RBCs allows increased oxygen carrying capacity and delivery to muscles.
Normal levels of RBC production will resume unless the process is repeated.
What is anaemia?
A condition in which the oxygen carrying capacity of the blood is reduced.
What is anaemia characterised by?
Reduced numbers of circulating red blood cells or a decreased amount of haemoglobin.
What is anaemia caused by?
Impaired erythrocyte production.
Increased erythrocyte destruction.
Blood loss/increased demand
What are the signs and symptoms of anaemia?
Fatigue
Cold intolerance
Headaches
Palpitations/tachycardia
Shortness of breath
Pallor of mucous membranes and nail beds
Describe iron deficiency anaemia
Most common cause of anaemia worldwide.
Leads to impaired red blood cell production due to lack of iron.
Causes include inadequate intake of iron rich foods, malabsorption, increased requirements, and increased iron loss through bleeding.
What is vitamin B12 essential for?
Production of RBCs
Key role in DNA synthesis
What are the causes of vitamin B12 deficiency?
Inadequate intake of vitamin B12
Malabsorption
What is folate (B9) essential for?
Co-enzyme in the synthesis of DNA/RNA and in the formation of blood cells in bone marrow.
What are the causes of folate (B9) deficiency?
Inadequate intake of folate
Malabsorption
Increased demand
Describe the anatomy of platelets
Irregular discs
Diameter = 2-4um
No nucleus
Contains many vesicles
Short life span (5-9 days)
What is the function of platelets?
Vesicles contain chemicals which promote blood clotting when released.
Also form a platelet plug to stop blood loss from damaged vessels.
Describe the formation of platelets
- under the influence of thrombopoietin, myeloid stem cells differentiate into megakaryocyte colony forming cells.
- these in turn develop into precursor cells called megakaryoblasts.
- these cells transform into megakaryocytes, which splinted into 2000-3000 fragments enclosed by a plasma membrane (platelets).
- platelets break off and enter the circulation.
What is haemostasis?
A sequence of responses that stops bleeding in response to blood vessel damage or rupture.
Name the 3 key mechanisms involved in haemostasis
Vascular spasm
Platelet plug formation
Blood clotting (coagulation)
Describe the vascular spasm mechanism
When an artery or arteriole is damaged, smooth muscle in the wall contracts immediately.
Effect of this contraction is to reduce blood loss for several minutes to several hours.
Vascular spasms are likely caused by damage to smooth muscle, substances released from activated platelets and reflexes initiated by pain receptors.
Describe the platelet plug formation mechanism
Platelets contact and stick to damaged parts of the blood vessel.
Platelets become activated after adhesion by extending projections to contact and interact, and release contents of their vesicles.
Other platelets in the area become more ‘sticky’ and adhere to original platelets, forming a mass called a platelet plug.
Describe the process of the blood clotting mechanism
A process during which a series of chemical reactions results in the formation of fibrin threads to stabilise the platelet plug.
Clotting involves a number of clotting factors.
Clotting is divided into three stages:
1. Formation of prothrombinase, involving an extrinsic and an intrinsic pathway
2. Conversion of prothrombin into thrombin by promthrombinase
3. Conversion of soluble fibrinogen into insoluble fibrin, which forms the threads of the clot.
What does the fibrinolytic system do?
Dissolve small, inappropriate clots and dissolves clots once damage is repaired.
Explain the role of vitamin K in blood clotting
It is essential for the production of several clotting factors (II, VII, IX and X).
Normal clotting is dependent on vitamin K levels.
Name the components of the lymphatic system
Lymph (fluid)
Lymphatic vessels
Lymphatic organs and tissues
Give examples of lymphatic organs and tissues
Red bone marrow
Thymus
Lymph nodes
Spleen
Lymphatic nodules
How are lymphatic vessels formed?
Lymphatic vessels begin as lymphatic capillaries, located in the spaces between cells.
Capillaries are more permeable than blood capillaries and can absorb large molecules like proteins and lipids.
These capillaries then unite converge to form larger lymphatic vessels.
Where does fluid flow through the lymph nodes?
At intervals along the lymphatic vessels.
What happens why lymphatic vessels exit lymph nodes?
They unite to form lymph nodes.
What are the functions of the lymphatic system?
Drainage of excessive interstitial fluid.
Immune response.
Transport of dietary lipids and lipid soluble vitamins.
Name the two ducts where lymph fluid is returned to the bloodstream.
Thoracic (left) lymphatic duct.
Right lymphatic duct.
What would happen if the excess interstitial fluid wasn’t drained?
Maintenance of circulating blood volume would not be possible.
Name the sequence of fluid flow in blood capillaries
Blood capillaries (blood)
Interstitial space (interstitial fluid)
Lymphatic capillaries (lymph)
Lymphatic vessels (lymph)
Lymphatic trunks/ducts (lymph)
Junction of the internal jugular and subclavian veins (blood).
What are the primary lymphatic organs? (give examples)
Sites where stem cells divide to become immunocompetent.
(e.g. red bone marrow and the thymus)
What are the secondary lymphatic organs? (give examples)
Sites where majority of immune response occur.
(e.g., lymph nodes, spleen and lymphatic nodules)
Describe the thymus
- located in mediastinum, between sternum and aorta.
- pluripotent stem cells in bone marrow give rise to pre-T cells, which migrate to the thymus, proliferate and begin to mature.
- process is helped by dendritic cells.
- thymic macrophages clear debris of dead cells.
- T cells are able to leave the thymus via the blood and migrate to secondary lymphatic organs.
Describe the lymph nodes
- bean shaped organs located along lymph vessels
- approximately 600 in the body and usually occur in groups.
- the parenchyma of a lymph node contains a number of different immune cells, including B cells, T cells, macrophages and plasma cells.
- lymph nodes function as a filter.
- as lymph enters one end of a node, foreign substances are trapped by fibres in the node.
- macrophages destroy other substances by initiating an immune response.
- the filtered lymph then leaves the other end of the lymph node.
- all lymph flows through multiple lymph nodes on its pathway through lymph vessels.
Describe the spleen
Larges mass of lymphatic tissue in the body.
Situated on the left hand side of the body, between the stomach and diaphragm.
Blood flowing into the spleen comes into contact with B and T cells, which carry out immune functions.
Spleen macrophages destroy blood-borne pathogens by phagocytosis.
The spleen is also responsible for the removal of defective blood cells and platelets.
Describe the lymphatic nodules
Egg shaped masses of lymphatic tissue.
Normally referred to a mucosa-associated lymphoid tissue (MALT).
Found in the lamina propria of mucous membranes lining the GI tract, urinary tract, reproductive tract and respiratory tract.
Some occur in large aggregations (e.g., tonsils)
