Histology of the Blood Flashcards
Constituents of Blood
Plasma
Serum
Plasma (makes up 56%- other44% is blood))
Plasma is blood minus the cells and comrpisises of
Water
Salts and minerals
Plasma proteins (albumins, globulins, fibrinogen)
Hormones
Signal molecules
Clotting factors dissolved in water
Serum
Serum is plasma minus the clotting factors
Erythrocytes
4-6 million per mL blood
Lifespan of 4 months
Produced in the liver (fetus) and bone marrow
Enucleate, boconcave discs aprrox 6.5-8.5 micrometres in diamtere (180 km end to end). Slightly larger in diameter than very smallest of capillaries
Major protein is haemoglobin
Destroyed in the liver and spleen after 120 days
Cell membrane has important endoskeleton attached (major protein- spectrin) to maintain cell shape
3 categories that white cell series (Leucocytes) are divided into
Granulocytes (contain visible granules)
Agranulocytes (no visible granules)
Platelets (cell fragments)
Which are most common types of Leucocytes?
Granulocytes are more common than arganulocytes
Neutrophils (polymorphonuclear leucocytes)
Commonest white blood cell and commonest granulocyte
Structure of neutrophils
Multi lobed nucleus
Granular cytoplasm
12-14 micrometres in diamtere (larger than red blood cells)
Role of neutrophils
Primary phagocytes- engulf and destroy bacteria and other foreign macromolecules. They do this by using the respiratory burst
Due to this function the cytoplasm contains the enzyme myeloperoxidase in order to conduct respiratory burst
What tye of cells are neutrophils?
Mobile and motile cells- they can circulate in blood and also invade through the walls of the blood vessels and through the glycosaminoglycan matrix of the tissues
What 3 types of cytoplasmic granules do neutrophils contain when seen using the nked eye/light microscope?
Primary granules
Secondary granules
Tertiary granules
Primary granules
Are lyzosomes
These contain the enzymes myeloperoxidase and acid hydrolases
Secondary granules
Contain specific granules that are secreted to mobilise inflammatory mediators
Tertiary granules
Contain gelatinases which break down proteins and adhesion molecules which break down proteins and adhesion molecules
These substamces are necessary to aid the neutrophil in its passage out of blood vessels and through tissue.
Eosinophils numbers/commoness
Makes up 1% of total number of white cells
Numbers increase in parasatic infections
Structure and size of eosinophils
12-17 micrometres in diameter
Bi-lobed nucleus
Distinctive large red cytoplasmic granules with crystaline inclusions
Role of eosinophils
-Play a role in phasgocytosis and in our response to parasites and in our response to other allergens
As they are phagocytic with partciular affinity for antigen/ antibody complexes
-They have an antagonistic action to basophils and mast cells
They inhibit mass cell secretion
They neutralise histamine- therefore restricting inflammatory responses
Structure of eosinophils in electron microscopy
Contain characteristic lozenge-shaped granules with crystalline cores
Bare recpetors for immunoglobulin E on their surface.
Basophils structure and size
Rare as they make up 0.5% of white cell series
14-16 micrometres in diameter
Bi lobed nucleus and prominent dark blue-staining cytoplasmic granules
Granules contain histamine
Basophils are another from, circukating form, of the tissue mast cell.
They have receptors for IgE
Role of basophils
Involved in inflammatory reactions and act to prevent coagulation and agglutination
Release histamine and vaso-active agents in response to allergens
This results in immediate hypersensitivty reactions, also known as anaphylaxis
Two types of lymphocytes
B cells
T cells
B cells
Become plasma cells and secrete antibodies
T cells
Are involved in cell-mediated immunity
Structure of lymphocytes
Very small cells- approx 10 microns in diameter
They appear on light microspcopy with almost all nucleus
The central haemotoxyphilic nucleus is surrounded by a very thin rim of cytoplasm, almost clear (greyish blue colour) with very few organelles wuthin it
B cells and T cells can be split further
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- supress TH cells and hence suppress the immune response
Natural Killer (NK) cells- mainly kill virus infected cells
Monocytes- strcuture and size
Immature cells, circulate briefly in blood
Characteristic reniform/kidney bean shaped nucleus
15-20 micrometres in diameter
Differenciate into one of several cell types within tissue
Although monocytes are classified as non- granulated, they do contain small cytoplasmic granules, mostly lysosomes
Role of monocytes
Major phagocytic and defensive role
Some become antigen presenting cells, passing antigen fragments to lmphocytes
Monocytes can differenciate into:
Tissue macrophage- everywhere
Kupffer cells- liver
Osteoclasts- bone, play a role in absorbing bone
Antigen presenting cells- everywhere
Alveolar mecrophages- lung
Platelets- what are they and structure?
Fragments of cells derived from large multi-nucleated Megakaryocytes in the bone marrow
1-3 micrometres in diameter, surrounded by cell membrane and containing vesicles with coagulation factors.
Role of platelets
Responsible for clotting of blood, particularly when the endothelium lining all blood vessels is breached
Hematopoiesis in humans
Blood cells derive from a single common stem cell that gives rise to 2 broad lineages/ 2 daughter cells
Haematopoiesis in adults
In adults, all blood cells form in the haematopoeitic bone marrow
However, in children this process begins in fetal life in the liver
Erythropoeisis
Erythropoeisis is characterised by a gradual reduction in cell size from the proerythroblast to the reticulocyte (these are the cells just before the production of red blood cells)
1-As the cell matures theres an increase in the prodcution of haemoglobin in the cytoplasm
2-Theres a gradual loss of organelles from the cytoplasm
3-In the early precursors of erythrocytes they are basophilic and this then changes to eosinophilia in late precursors as the amount haemoglobin in the cytoplasm increases
4-Loss of nucleus
5-Mediated by the hormone erythropoeitin (EPO) produced in kidney
Granulopoeisis
Morphology similar for neutrophils, eosinophils and basophils
Bone marrow holds a large pool of stored mature neutrophils that can be released into the circulation during times of infection
There is no stored pool of monocytes and lymphocytes precursors complete their maturation at other sites, either in lymph nodes or in the thymus
This process of Granulopoeisis is characterised by
-an increasing number of granules
-incrwasingly complex shape of nucleus
Which is the only type of mature blood cell is capable of cell division?
lymphocytes
