Histology 2 - Haematology and anaemia Flashcards
What is blood?
Specialised supportive or connective tissue
What components does blood consists of?
Plasma
Dissolved fibrinogen
Circulation blood cells are the cellular component - leucocytes (WBCs), platelets (thrombocytes), erythrocytes (RBCs)
What is the function of the plasma and the fibrinogen?
The plasma acts as a watery ground substance
The fibrinogen polymerises to form insoluble fibrin fibres during coagulation
What is the function of leucocytes?
These are immune and defence cells of the blood
Primary function is to protect the body against infection
Work with immunoglobulins and complement
Produce cytokines - augment function or stimulate proliferation of other cells
What are the three classes of leucocytes and where do these develop?
Granulocytes
Lymphocytes
Monocytes
All three classes develop from the haematopoietic stem cells in the bone marrow
What are the general functions of the different leucocyte classes? (v brief)
Granulocytes and Monocytes - these are phagocytes SO they ingest and destroy pathogens and cell debris - they are attracted to sites of inflammation by chemotactic substances released by damaged components or by complement components
Lymphocytes (along with their precursor cells and platelets) are immunocytes
Describe granulocytes and give the different types
Can see cytoplasmic granules in standard blood films/smears
Characterised by the presence of nuclei with several lobes
Motile and Phagocytic
Neutrophils
Eosinophils
Basophils
Describe the appearance and function of neutrophils
Majority of leucocytes
Segmented nuclei - 2 to 5 lobes
Fine, pinkish cytoplasmic granules
Have very few organelles
First line of defence
Highly phagocytic and remove damaged tissue after injury e.g. acute inflammation
Greatly increase in number during inflammation
Enzymes within their granules act to kill/degrade ingested microbes or debris via e.g. hydrogen peroxide
Describe the appearance and function of eosinophils
Very small number - 1 to 4% of circulating leucocytes
Bilobed nuclei
Red-orange granules
Defence against parasitic infection especially helminths and protozoa
Lysosomal granules contain cytotoxic compounds and lysosomal enzymes
Pro-inflammatory cells
Attracted to the site by products released from basophils, mast cells, lymphokines and allergy related antigen/antibody complexes
These are increased in allergic diseases such as asthma, hayfever and exzema
Describe the appearance and function of basophils
Occasionally seen in the peripheral - less than 1%
Large dark purple cytoplasmic granules
Bilobed nucleus - can often be obscured by the large granules
Granules contain histamine (vasoactive) and heparin (anticoagulant)
Mast cells are the tissue equivalent of basophils and these mediate their response
Have membrane receptors for IgE - when IgE attaches to the receptor, the cell is activated and degranulation is initiated - release of enzymes that are vasoactive, bronchoconstrictive and chemotactic and this release is classical sign of immediate hypersensitivity
Give the appearance and function and different types of Lympohocytes
Make up 20-40% of circulating leucocytes
Round, condensed nuclei
Cytoplasm forms only a narrow rim around the nucleus
Assist phagocytes
Comprised of B and T cells
Have the longest lifespan of any leucocytes
What is the function of B cells?
These are lymphocytes
Process primarily in the bone marrow
Mediate humoral or antibody-mediated immunity
What is the function of T cells?
These are lymphocytes
Processed in the thymus
Mediate cell-mediated immunity i.e. protection against extracellular infection e.g. viruses and fungi
Describe the appearance and function of monocytes
Make up 2-6% of ciruculaitng leucocytes
Largest of the leucocytes
Indented, horseshoe shaped nuclei
Abundant blue-grey cytoplasm
Circulate the blood for 20-40 hours
Then enter tissues where they matures into macrophages
These phagocytose and destroy pathogens and cellular debris
Present antigens to lymphoid i.e. T cells
Produce cytokines to regulate and participate with inflammation
What are platelets and what are their functions?
Aka. thrombocytes
Small, non-nucleated cells
