BMS1058 - Haemotology and the Lymphatic System Flashcards by Anya Anderson

Describe the compositionof blood.

55% blood plasma
45% red blood cells
<1% biffy coat - white blood cells and platelets

Blood plasma:
- proteins, water, solutes

Proteins: Albumins, globulins and fibrinogen

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What are the functions of blood?

Transportation
- oxygen, CO2, nutrients, hormones, heat and waste products

Regulation
- pH, body temperature, water content

Protection
- clotting, immune response, blood proteins

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What is Haematopoiesis?

The process by which the formed elements of the blood develop.

Sites of haematopoiesis vary according to stage of life.

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Approx ____% of cells in bone marrow are haematopoietic _____ cells. Why is this essential?

0.05-0.01%

stem cells

essential as they produce, differentiate etc to give rise to RBCs, which have a short half-life.

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How are stem cell important in bone, cartilage and msucle tissue?

Because they can form osteoblasts, chondroblasts and muscle cells.

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How is haematopoiesis regulated?

By growth factors, including:
- Erythropoietin
- Thrombopoietin
- Cytokines

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What do myeloid and lymphoid stem cells produce?

Lymphoid: lymphocytes (T, B, and killer)

Myeloid: RBCs, platelets, granular leukocytes, mast cells, monocytes

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How are RBCs adapted to function?

No nucleus and biconcave disc shape - increased SA for O2

Lack mitochondria and generate ATP anaerobically - so don’t use up O2

Strong and flexible plasma membrane - allows cells to squeeze through blood capillaries

Antigens - account for diff blood groups

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To maintain normal levels of RBCs, new mature cells must enter circulation at rate of __ million per second.

Haemoglobin found in cyctoplasm of RBCs consitute approx __% of cell weight.

Hb carries approx __ of total CO2 in the body. CO2 binds to the ____ part of the Hb as blood travels through capillaries.

_______ _______ produced by endothelial cells lining blood vessels can also bind to Hb, causing vasodilation.

2 million

33% weight

23% of CO2

globin part

Nitric Oxide

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RBCs contain which enzyme? What does it do?

Carbonic anhydrase

Catalyses conversion of CO2 and H2O into carbonic acid, which then dissociates into H+ and HCO3-.

Serves as a buffer in the extracellular fluid.

Allows 70% of CO2 to be transported into plasma in the form of HCO3-.

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RBCs survive for approx 120 days due to what? Where are they broken down?

Damage to plasma membranes as moving through capillaries.
They cannot synthesise new components to repair damage due to lack of nucleus and other organells.
They becomes increasingly fragile with age and more prone to rupture.

RBCs breakdown in the liver and spleen. Products recycled and reused in other processes.

Formation and destruction of RBCs should occur at same pace.

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When RBCs are broken down, what is globin recyled as and for?

Amino acids to be reused for protein synthesis.

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What are RBCs also known as?

Erythrocytes

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When RBCs are broken down, how is the Heme group broken down to be excreted as waste?

Either converted into Biliverdin, then Bilirubin to be processed in the liver and reused in bile.

In the small intestine, Bilirubin broken down by bacteria into Urobilogen, which is converted either to Urobilin to form urine or Stercobilin to form feces.

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When RBCs are broken down, how is the Heme group recycled and reused in haematopoiesis?

Converted to Fe3+, which is bound to transferrin and transported to the liver where it binds instead to Ferritin for storage.

Some Fe3+ is rebound to transferrin and transported to bone marrow where Erthropoiesis (formation of RBCs) occurs.

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How are RBCs formed? (Erthropoiesis)

Begins in bone marrow with proerythroblast (precursor cell). This divides several times to become a reticulocyte, which ejects its nucleus.

Reticulocytes enter blood stream and become RBCs within 1-2 days.

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How is Erythropoiesis controlled?

Stimulus = hypoxia (insufficient oxygen)

Stimulates kidneys to increase release of Erythropoietin (EPO).

EPO increases production of proerythroblasts in bone marrow.

Increasing RBC production and thus oxygen delivered to tisssues.

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How is EPO sometimes used in sports? Any risks to this?

Blood doping

To increase RBC production and therefore oxygen reaching tissues for respiration.

Enhancing endurance and performance of athletes.

Risks: could increase risk of strkes/high b.p. due to increase in blood viscosity

Why might altitude training benefit athletes?

Stimulates release of EPO from kidneys (as low O2), increasing RBC production.

Normal levels of RBC production resumes unless this process is repeated.

What is Anaemia? Causes? Symtoms?

A condition where the oxygen carrying capacity of the blood is reduced.

Characterised by reduced numbers of RBCs or Hb in blood.

Caused by:
- impaired RBC production
- increased RBC destruction
- blood loss/increased demand

Symptoms:
fatigue, cold tolerance, headaches, shortness of breath, pallor of mucous membranes and nail beds.

Different types of anaemia. e.g. iron deficiency anaemia, VitB12 deficiency anaemia etc

What deficiencies can affect the formation of erythrocytes? What can they be caused by?

[Iron deficiency]
Caused by inadequate intake, malabsorption, increased demands or blood loss

[Vitamin B12 deficiency - essential for production of RBCs and has key role in DNA synthesis.]

Caused by inadequate intake or malabsortion due to IB Diseases, surgery, drugs or defective secretion of intrinsic factor (needed to absorb VitB12).

[Folate (B9) deficiency - important as a co-enzyme in synthesis of DNA/RNA and RBC formation.]

Caused by inadequate intake, malabsorbtion due to Crohn’s or Coeliac disease, increased demand due to pregancy/lactation, blood diseases, cancer etc

How do RBCs with iron deficiecy anaemia and B12/folate deficiency anaemia look different under the microscope?

Describe the structure and function of platelets. Life span? How are dead/aged platelets they removed?

Irregular discs.
No nucleus but contains many vesicles (contain chemicals which promote blood clotting).

Form platelet plugs to stop blood loss from damaged vessels.

Short life span of approx 5-9 days.
Aged and dead platelets removed by macrophages in the liver and sleen.

How are platelets formed?

Under the influence of thrombopoletin, myeloid stem cells differentiate into megakaryoctye colony forming cells.

These turn into megakaryoblasts (precursor cells) which then for into megakaryocytes.

Megakaryocytes splinter into 2000-3000 gragments enclosed by plasma membranes, called platelets. Break off and enter blood.

What 3 key mechanisms are involved in stopping bleeding when a blood vessel is damaged?

Vascular spasm Platelet plug formation Blood clotting (coagulation)

What happens in Vascular spasm?

When an artery or arteriole is damaged, smooth muscle in the wall contracts immediately. Reducing blood loss. Caused by - Damage to smooth muscle - Substances released from activated platelets - Reflexes initiated by pain receptors

What occurs in Platelet plug formation?

Platelets contact and stick to damaged parts of vessel. Platelets activated after adhesion by extending projections to contact and interact, and release content of their vesicles. Other platelets in area become mroe 'sticky' and adhere to original platelets forming a mass (platelet plug).

What occurs in blood clotting?

Series of chemical reactions results in the formation of fibrin threads to stabilise the platelet plug. Involves clotting factors. Divided into 3 stages: - formation of prothrombinase (intrinsic and extrinsic pathways) - converstion to thrombin and promthrombinase - conversion of soluble fibrinogen to insoluble fibrin, forming threads of clot.

Describe the extrinsic pathway of forming prothrombinase.

Tissue factor (thromboplastin) leaks into blood from outside blood vessels to initiate prothrominase formation.

Describe the intrinsic pathway of forming prothrombinase.

Activators in direct contact with blood initiate prothrominase formation.

Prothrombinase and ___ catalyse the conversion of prothrombin into thrombin. Thrombin (in the presence of ___) converts fibrinogen into loose ____ threads, which are insoluble. Thrombin also activates factor ___ which strengthens and stabilises the threads into a sturdy clot.

Ca2+ Ca2+ fibrin factor XIII

Wat type of feedback system is blood clotting? What issue could this cause? What other system deals with this?

Positive feedback system - can cause clots to enlarge too much. Dealt with by the fibrinolytic system.

How does the fibrinolytic system dissolve clots once damage is repaired? Other methods of control involved release of ______ and presence of ___________ in the blood.

Plasminogen is incorportated into clot during its formation. This can be activated into plasmin which dissolves clot by digesting fibrin threads and inactivating other substances. ----------- release of prostacyclin anticoagulants

Lymphatic vessels begin as lymphatic _______, located between _____. These are more __________ than blood capillaries and so can absorb large molecules like _____ and ______. These campillaries converge to form larger lymphatic _____. Fluid fows through lymph ______ at intervals along these. As lymphatic vessels exit lymph nodes, they unite to form lymph ______.

Capillaries between cells permeable proteins and lipids vessels nodes trunks

What are the functions of the lymphatic system?

Drainage of excess interstitual fluid. Immune reponse. Transport of dietary lipids and lipid soluble vitamins.

Why does the lymphatic system need to return fluid to the blood?

because more fluid filters out of blood capillaries than returns to them by reabsorption. To maintain blood volume.

Fluid is returned to the bloodstream via which two lymphatic ducts?

The thoracic (left) lymphatic duct and the right lymphatic duct.

What is the sequence of fluid flow from blood back to blood?

Blood campillaries --> interstitual spaces (interstitual fluid) --> lymphatic capillaries --> lymphatic vessels --> lymphatic trunks/ducts --> junction of the internal jugular and subclavian veins

How do primary and secondary lymphatic organs affect the immune system?

Primary Lymphatic organs: - sites where stem cells divide to become immunocompetent - e.g. red bone marrow and thymus Secondary lymphatic organs: - sites where majority of immune responses occur - e.g. lymph nodes and nodules and spleen

Where is the thymus lcoated? What does it do?

Located between sternum and aorta. Primary lymphatic organ. Stem cells in bone marrow give rise to pre-T cells, which migrate to the thymus, multiply and begin to mature - helped by dendritic cells. Thymic macrophages clear debris of dead cells as only 2% of developing T cells are thought to survive. T cells then move to blood and migrate to secondary lymphatic organs.

What are lymph nodes? How many in the body? What do they function as? What do they contain?

Secondary lymphatic organ. Bean-shaped organs, located along lymph vessels. Approx 600 in the body, occur in groups. Function as filters - foreign substances are trapped by fibres. Macrophages destroy some substances by phagocytosis. Lymphocytes destroy other substances, initiating immune response. Contain a number of different immune cells - e.g. B and T cells, macrophages and plasma cells.

What is the spleen? Where is it situated? Blood flowing into the spleen comes in contact with what? What else is the spleen responsible for?

Secondary Lymphatic organ Largest mass of lymphatic tissue in the body, situated on the left, between the stomach and dipharagm. Blood comes into contact with B and T cells. Spleen macrophages also, which destroy blood-borne pathogens by phagocytosis. Responsible for the removal of defective blood cells and platelets.

What are lymphatic nodules? What are they normally referred to as? Where are they found?

Egg-shaped masses of lymphatic tissue. Referred to as mucosa-associated lymphatic tissue (MALT) Found in lamina propria of mucous membranes lining: - GI, urinary, reproductive and respiratory tract. Some occur in large aggregations e.g. tonsils