Histology 6 (Blood) Flashcards
What is blood?
Fluid connective tissue
Comprises cellular component making up 44% of the blood, and a fluid component (Plasma) making up remaining 56%.
What is plasma?
Blood minus the cells
Comprises:
water
salts & minerals
plasma proteins (albumins, globulins, fibrinogen)
hormones, signal molecules
other clotting factors etc.
What is serum?
Plasma minus clotting factors
What are the most common cells within the blood?
Erythrocytes (Red blood cells)
How many erythrocytes in the blood?
4 to 6 million per ml blood
What is the lifespan of an erythrocyte?
Lifespan of 4 months/120 days
What shape do erythrocytes have?
Enucleate bioconcave discs
What is the size of erythrocytes?
Approximately 6.5 to 8.5 microns in diameter
Where are erythrocytes produced?
Liver in the fetus
Haematopoietic bone marrow in adults
Where are erythrocytes destroyed?
Liver and spleen
What is the major protein in erythrocytes?
Haemoglobin
How is the cell shape of erythrocytes maintained?
Endoskeleton attached via a major protein called spectrin
What are the 3 categories of white blood cells?
Granulocytes (contain visible granules)
Agranulocytes (no visible granules)
Platelets (cell fragments)
What are the most common white blood cells?
Neutrophils
40-75% of WBC
What percentage of WBC are eosinophils?
5%
What percentage of WBC are basophils?
0.5%
What percentage of WBC are lymphocytes?
20-50%
What percentage of WBC are monocytes?
1-5%
What makes neutrophils easy to identify?
Multi lobed nucleus
Faintly granular cytoplasm
How big are neutrophils?
12 to 14 microns in diameters
Are neutrophils phagocytes?
Yes, they engulf and destroy bacteria and other foreign macromolecules using the respiratory burst
What does the cytoplasm of neutrophils contain?
Enzyme myeloperoxidase needed in order to conduct the respiratory burst
Are neutrophils mobile?
Yes they circulate in blood and invade through walls of blood vessels through the glycosaminoglycan matrix of the tissues
What are the 3 types of granules?
Primary - lysosomes containing enzyme myeloperoxidase and acid hydrolases
Secondary - contain specific substances that are secreted to mobilise inflammatory mediators
Tertiary - contain gelatinases which break down proteins and adhesion molecules that aid neutrophils out of blood vessels and through tissue
In which patients do eosinophils numbers increase?
Patients with parasitic infections or a number of other allergic conditions
What is the size of eosinophils?
12-17 microns in diameter
What characteristics doe eosinophils have?
Bi lobed nucleus
Cytoplasm stuffed with distinctive large red granules containing crystalline inclusions
What do eosinophils do?
Play a role in phagocytosis in our response to parasites and other allergens
Antagonistic actions to basophils and mast cells
What do eosinophils bear receptors for?
Immunoglobulin E
What do eosinophils neutralise?
Histamine
What size are basophils?
14-16 μm in diameter
What characteristics do basophils have?
Bi-lobed nucleus and prominent dark blue-staining cytoplasmic granules
What do basophils granules contain?
Histamine
What do basophils do?
Involved in inflammatory reactions and act to prevent coagulation and agglutination
What do basophils have receptors for?
Immunoglobulin E
What are the two sub types of lymphocytes?
B Cells - become plasma cells and secrete antibodies
T Cells - are involved in cell-mediated immunity
Why do lymphocytes have a clear blue/grey cytoplasm?
Very few cytoplasmic inclusions
What size are are lymphocytes?
Approx 10 microns in diameter
What are the types of lymphocytes?
B Cells – produce antibodies
T Helper (TH) Cells – help B cells and activate macrophages
T Cytotoxic (TC) Cells – kill previously marked target cells
T Suppressor (TS) Cells – suppress TH cells and hence suppress the immune response
Natural Killer (NK) Cells – mainly kill virus infected cells
What size are monocytes?
15-20 μm in diameter
What are monocytes?
Immature cells, circulate briefly in blood
What characteristic nucleus do they have?
Characteristic reniform nucleus
Kidney bean shaped nucleus
What can monocytes do?
Differentiate into one of several cell types within tissue
What do monocytes do?
Major phagocytic and defensive role
Some become antigen presenting cells, passing antigen fragments to lymphocytes
What can monocytes differentiate into?
Tissue macrophages - everywhere
Kupffer cells – liver
Osteoclasts – bone
Antigen presenting cells - everywhere
Alveolar macrophages – lung
What are platelets?
Fragments of cells derived from large multi-nucleated Megakaryocytes in the bone marrow
What size are platelets?
1-3 microns in diameter
What are platelets surrounded by?
Surrounded by cell membrane and containing vesicles with coagulation factors
What do platelets do?
Responsible for clotting of blood, notably when the endothelium lining all blood vessels is breached
What is the formation of blood cells called?
Haematopoeisis
What do all blood cells derive from?
Multi-potential haematopoietic stem cell know as a haemocytoblast
What is the bony trabeculum?
Hematopoietic bone marrow originated from an adult
Where do all blood cells in adults form?
Haematopoietic bone marrow
Where do all blood cells in children form?
Process begins in fetal life in liver
What are the 3 broad cell series?
Myelon 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
What happens in Erythropoeisis?
•Reducing cell size
•Haemoglobin production increases
•Reduction and loss of organelles
•Basophilia in early precursors changes to eosinophilia in late precursors
•Loss of nucleus
•Mediated by erythropoeitin (EPO)
What happens in Granulopoeisis?
•Morphology similar for neutrophils, eosinophils and basophils
•Increasing number of granules within cytoplasm
•Increasingly complex shape of the nucleus
•Large pool of stored mature neutrophils in marrow that can be release into the circulation during times of infection
