Blood Flashcards by Scarlett Enright

Constituents of blood

Cellular component = 44%
Plasma - blood minus the cells and comprises: 56%
• water
• salt and minerals
• plasma proteins (albumins, globulins, fibrinogen)
• hormones, signal molecules
• other clotting factors etc
Serum - plasma minus clotting factors

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Lifespan of erythrocytes

120 days

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Where are erythrocytes produced

liver (foetus) and haematopoetic bone marrow of axial skeleton/ long bones (adults)

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Structure and size of erythrocytes

• enucleated, biconcave discs - 6.5-8.5um in diameter
• major protein in cytoplasm = haemoglobin
• destroyed in liver and spleen
• cell membrane has important endoskeleton attached (major protein- spectrin) to maintain shape

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How many erythrocytes per ml of blood

4-6 million

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3 types of white cell series

Granulocytes, agranulocytes and platelets

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Types of granulocyte

• 40-75% neutrophils
• 5 % eosinophils
• 0.5% basophils

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Types of agranulocytes

• 20-50% lymphocytes
• 1-5% monocytes

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Structure and size of neutrophils

• multi-lobed nucleus, granular cytoplasm, 12-14um diameter
• phagocytotic - engulf and destroy bacteria and other foreign macromolecules using the respiratory burst
• mobile and motile cells- circulate in blood and invade tissue spaces
• contain myeloperoxidase- enzyme needed to conduct respiratory burst
• able to operate in hostile environments (e.g. low oxygen tensions).

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3 types of cytoplasmic granules in neutrophils

Primary granules- lysosomes (myeloperoixdase and acid hydrolases) that digest phagocytosed foreign material
Secondary granules- specific granules that secrete substances that mobilise inflammatory mediators
Tertiary granules- gelatinases (which break down proteins) and adhesion molecules (aid neutrophil out of blood vessels and through tissue)- faciliatate insertion of proteins into cell membrane

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Examining cellular composition of blood

cellular composition of blood can be readily examined in a smear of whole cells produced by spreading a small drop of blood over a glass slide, allowing it to dry and then staining it with a Romanowsky stain/ Leishman’s stain

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Structure and size of eosinophils

• 12-17um in diameter
• Bi-lobed/ tri-lobed nucleus
• Distinctive large red cytoplasmic granules with crystalline inclusions

• Charcot-Leyden crystals- Characteristic lozenge-shaped granules with crystalline cores (proteinaceous)
• Receptors for IgE (immunoglobulin E)

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Role of eosinophils

Play a role in phagocytosis with particular affinity for antigen/antibody complexes and response to parasites and allergens

• Receptors for IgE (immunoglobulin E)
• Inhibit mast cell secretion
• Neutralise histamine so restrict inflammatory responses
• They remain in the circulation for only a few hours and show a diurnal fluctuation in numbers, being highest in the morning.
• 1% of total number of white blood cells
• Numbers increase in parasitic infections or allergic conditions

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Mast cells

important role in inducing the inflammatory cascade eg release histamine. Innate or adaptive immune mechanisms can induce the mast cell to degranulate, releasing inflammatory mediators into the extracellular space.
Use a meta chromatic stain

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Structure and size of basophils

• 0.5% of white cell series
• 14-16um in diameter - largest granulocyte
• Bi-lobed nucleus
• Prominent dark blue-staining cytoplasmic granules
• Granules contain histamine

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Role of basophils

• involved in inflammatory regulations and act to prevent coagulation and agglutination
• Circulating form of the tissue mast cells
• Receptors for IgE
• Release histamine and vaso-active agents in response to allergens
• Results in immediate type 1 hypersensitivity reaction- anaphylaxis

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Role of neutrophils

• phagocytotic - engulf and destroy bacteria and other foreign macromolecules using the respiratory burst
• mobile and motile cells- circulate in blood and invade tissue spaces
• contain myeloperoxidase- enzyme needed to conduct respiratory burst
• able to operate in hostile environments (e.g. low oxygen tensions).

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2 types of lymphocytes

2 functional subtypes:
1. B cells (become plasma cell and secrete antibodies)- develop in bone marrow
2. T cells (involved in cell mediated immunity)- develop in thymus

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Structure and size of lymphocytes

• Very few cytoplasmic inclusions so clear blue/grey cytoplasm
• Relatively small cells - 10um (grow in size as mature)

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B cells

Produce antibodies

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T helper cells

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Activate B cells
Activate macrophages

T cytotoxic cells

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Kill previously marked target cells

T supressor cells

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Suppress TH cells so suppress immune response

Natural killer cells

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Mainly kill virus infected cells

Structure and size of monocytes

• immature cells- circulate briefly in blood (a few hours) • Characteristic reniform nucleus • 15-20um in diameter

Role of monocytes

• Differentiate into one of several cell types within connective tissue • Major phagocytotic and defensive role • Some become antigen presenting cells- passing antigen fragments to lymphocytes • Small cytoplasmic granules- mostly lysosomes

What do monocytes differentiate in to

• Tissue macrophages- everywhere • Kupffer cells- liver, present in sinusoids • Osteoclasts- bone, play a role in absorbing bone • Antigen presenting cells- everywhere • Alveolar macrophages- lung

Which viscera have fixed macrophages derived from circulating monocytes

Spleen Liver

Structure and size of Platelets

• anucleated fragments of cells derived from large multi-nucleated megakaryocytes in bone marrow • 1-3um in diameter surrounded by cell membrane and containing vesicles with coagulation factors

Role of platelets

• Responsible for clotting of blood- particularly when endothelium lining of blood vessels is breached

3 types of platelet granules

1. Alpha granules- contain clotting factors 2. Delta granules- contain serotonin absorbed into them from plasma following the discharge of clotting factors 3. Peroxisomes- contain catalase (enzyme used in elimination of oxygen radicals)

Haematopoesis

formation of blood cells in bone marrow • all blood cells derived from a common multi potential haematopoetic stem cell (haemocytoblast)

Haemocytoblast divides to form 2 different types of daughter cells:

1. Common myeloid progenitor- ultimately gives rise to platelets, red blood cells, basophils, neutrophils, eosinophils, monocytes and mast cells 2. Common lymphoid progenitor- ultimately gives rise to lymphocytes

Myelin

series lies next to bone and gives rise to white blood cells

Erythron

series lies in between bony trabeculae and gives rise to erythrocytes

Megakaryocytes

lie in between bony trabeculae and give rise to platelets

Erythropoesis

• reducing cell size • Haemoglobin production • Reduction and loss of organelles • Basophilia in early precursors changes to eosinophilia in late precursors • Loss of nucleus • Mediated by erythropoeitin (EPO)- hormone produced in kidneys • Reticulocyte → erythrocytes

Reticulocyte

contain blue-staining remnants of cytoplasmic organelles, notably the remains of the ribosomes used to synthesize the haemoglobin Reticulocyte levels increase due to severe loss of blood

Granulopoesis

• morphology similar for neutrophils, eosinophils and basophils • Increasing number of granules • Increasingly complex shape of nucleus • Large pool of stored mature neutrophils in marrow

How are erythrocytes removed

removed in spleen, liver, bone marrow (reticuloendothelial system) and through blood loss

What is Erythropoesis regulated by

the hormone erythropoietin (a heavily glycosylated polypeptide)- secreted by the kidney in response to hypoxia • It stimulates Erythropoesis by increasing the number of progenitor cells

Haematocrit

Haematocrit (PCV) = ratio of volume of red blood cells to total volume (45%)

Anaemia

haemoglobin level in blood below the normal level for age and sex • male <130g/L + female <110g/L

In which bones does haemopoesis occur in adult

Axial skeleton

Innate immunity

neutrophils, eosinophils, basophils, macrophages, mast cells- non-specific immunity (cytokines, phagocytosis, cytotoxicity)

Adaptive immunity

B cells, T cells- antigen-specific immunity (cytokines, antibodies, cytotoxicity)

Myelopoiesis

production of white blood cells, hormonal factor: granulocyte-macrophage colony stimulating factor (GM-CSF)- only stimulate production of myeloblastic white blood cells not lymphoid cells

Which hormone controls Myelopoiesis

Granulocyte-macrophage colony stimulating factor GM-CSF

Lifespan of platelets

7-10 days

Membrane blebbing process

platelets break off from the megakaryocytes. 1 megakaryocyte can produce up to 4000 platelets • Stimulated by thrombopoietin

Blood Flashcards

(50 cards)