W1 Haematopoietic System and Component Parts Part 1 Flashcards
what are the functions of the haematopoietic system?
- provide the cells for dissemination of oxygen and removal of carbon dioxide
- provide the cells that mediate protection against infection with pathogens, tumours and toxins
- provide the cells that contribute to the repair of injury and maintenance of tissues and organs
where do blood cells arise from?
bone marrow
myeloid progenitor cells differentiate into what myeloid cells (colony forming units)?
erythroid, megakaryocytes, basophils, eosinophils and granulocyte-monocyte
what do erythroid CFU produce?
erythrocytes (red blood cells)
what do megakaryocytes produce?
platelets
what do granulocyte-monocyte CFU produce?
neutrophils and monocytes
what is erythropoiesis?
the production of red blood cells
what is a erythrocyte?
a red blood cell - consisting mainly of haemoglobin, a complex metalloprotein which contains heme groups where the iron temporarily binds to the oxygen (from lungs/gills) and releases them throughout the body
haemoglobin in erythrocytes carries some waste carbon dioxide back from the tissues - what happens to the rest?
most is transported in plasma as dissolved bicarbonate ions
what is the most common cell in the body (makes up 25%)?
erythrocytes
where are erythrocytes restricted to?
blood vessels of the body
erythrocytes are small rounded cells with a small area of central pallor (6-8microns) - what is their half life?
50 days
are erythrocytes nucleated?
they are non-nucleated in mammals but nucleated in other vertebrates, they lack most organelles
what percentage of erythrocytes are haemoglobin (the iron containing ocygen-transport metalloprotein)?
96%
the production of platelets mediate blood coagulation - what does this allow?
allows the clotting of damage to a blood vessel
tissues recruit what to a site of injury to remove bacteria?
leukocytes (initially neutrophils and the macrophages)
what process removes bacteria and cell debris from a wound?
phagocytosis (promotes wound healing)
how do phagocytic leukocytes fulfil homeostatic functions beyond cell defence?
tissue remodelling and removal of dead cells/cellular debris as part of normal cell turnover
do platelets have a nucleus in mammals?
no
what is the second most abundant cellular component of blood?
platelets
how long do platelets circulate in the blood for?
7-10 days
where is 1/3 of platelet mass normally sequestered?
in the spleen
what are platelets?
non-nucleated fragments of cytoplasm which are derived from megakaryocytes in bone marrow
what are unactivated platelets?
biconvex discoid structures with a maximum diameter of 2-3 microns
where are platelets restricted to?
blood vessels
what type of animal are platelets unique to?
mammals
what cell in birds share properties with mammalian platelets, what are they unable to do?
nucleated thrombocytes, but they are unable to form plugs to block damaged arteries (high pressure)
what are GPs?
glycoproteins
what surface GP binds to collagen?
GPIa
what surface GP binds to Von Willebrand Factor?
GPIb and IIb/IIIa
what surface GP binds to fibrinogen?
GPIIb/IIIa
what are storage granules released by?
the canalicular system
what do alpha granules contain many of?
clotting factors
what do dense granules contain?
adenosine di and triphophates (ADP/ATP) and calcium
what do lysosomes store?
hydrolytic enzymes and catalase
what do platelets contain that allow them to quickly change state to activated following blood vessel damage?
cytoskeletal proteins
what are granulocytes?
polymorphonuclear leukocytes - neutrophils, eosinophils and basophils (white blood cells)
what percentage of granulocytes make up white blood cells in blood?
60-70%
monocytes are blood borne, what do they become in tissues?
macrophages
what are neutrophils?
large cells (10-20microns) with multilobed nuclei, they only live 2-3 days, they are cells of the innate immune system and have neutral staining cytoplasmic containing enzymes
what percentage of granulocytes are neutrophils?
90%
are neutrophils phagocytic?
yes - they kill bacteria by microbicidal mechanisms
what are macrophages?
large differentiated monocytes (>20microns), their function differs between tissues, this includes phagocytosis, stimulation of adaptive immune system response, tissue repair and iron homeostasis
what are eosinophils?
large granulocytes (12-17 microns) that circulate for 8-12h and in tissues for up to 12 days, they contain prominent granules which stain red and have a crystalline core
what percentage of white blood cells do eosinophils represent?
2-3%
what infections are eosinophils important for?
helminth infections
eosinophils contain a crystalline core of major basic protein cytotoxic for what?
parasites
eosinophils have receptors for IgE antibodies and contribute to what?
allergic reactions
what are basophils?
white blood cells that contain large cytoplasmic granules which obscure the cell nucleus under a microscope when stained with basic dyes, they make up 0.01-0.3% of circulating WBCs
what do basophils play a role in?
they participate in inflammatory reactions and play a role in responses to parasites and allergens (IgE) receptors, release histamine, leukotrienes and prostoglandins)
what are basophils most closely related to?
to tissue resident mast cells
what are monocytes?
mononuclear phagocytes (12-15microns) that respresent 5-10% of white blood cells, identified by stained smears by their kidney shaped nucleus, found primarily in the blood and spleen
monocyte progenitors/precursors circulate in the blood for how many days before migrating to tissues?
1-3 days
what are monocytes for?
rapid response to inflammatory stimuli and migrate in large numbers to infected/injured tissues
what are dentritic cells?
closely related to monocytes/macrophages, they continuously sample the environment for antigens, they are irregularly long shaped with long cytoplasmic dendrites
plasmacytoid dendritic cells are specialised in inducing what?
anti-viral responses
conventional dendritic cells are professional antigen presenting cells where they present foreign antigens to what?
T lymphocytes (adaptive immune response)
dendritic cell precursors are present in low numbers in blood, where do they migrate to?
both lymphoid and non-lymphoid tissues
monocytes can differentiate into what dendritic cells?
inflammatory
what are mast cells important for?
response to a range of pathogens (helminths), in wound healing and in allergies - they release many activating factors like histamine and have receptors for IgE
what passes through blood as immature cells and migrate into tissues where they then mature?
mast cells
where are mast cells found?
in connective and mucosal tissues - types vary with location and contents of granules
lymphoid cells represent what percentage of white blood cells in blood?
30%
how are lymphoid cells distingusihed?
they have a large nucleus that may be eccentric (not central) and a relatively small amount of cytoplasm
what are the major constituents of the adaptive immune system?
T and B cells
what do most T lymphocytes express?
alpha-beta T cell receptors - they recognise foreign peptides presented to them by histocompatibility complex (MHC) molecules on other cells
do T cells have a small or broad range of T cell receptors?
they have a broad range that are capable of recognising very distinct antigenic peptides
what are T cells broadly characterised into?
helper T cells (CD4) - specialised in helping drive immune responses against different types of pathogens
cytotoxic T cells (CD8) - recognise and kill infected/transformed cells
what are B lymphocytes name derived from?
derives from their maturation in birds in the bursa Fabricus
what do B lymphocytes express?
express B cell receptors - immunoglobulin that recognises foreign molecules (proteins or carbohydrates)
what happens when B lymphocytes are activated?
plasma cells secrete immunoglobulin - antibodies that mediates a broad range of effects against pathogens
B lymphocytes can act as antigen-presenting cells, what response is this?
2degree response
what do both B and T cells have that enables the basis of immunity to reinfection and vaccination?
the ability to require memory
what are the four innate-like lymphocytes?
- natural killer (NK) cells
- natural killer T (NKT) cells
- γδ T cells
- innate lymphoid cells
what do the innate-like lymphocytes do?
they play a role in a protective immunity and the regulation of homeostasis and inflammation, their disregulation can lead to immune pathology such as allergy and autoimmune disease
are γδ T cells a minor or major component?
minor in humans, major in ruminants, pigs and chickens - they do not recognise MHC present peptides in humans (recognise pathogen metabolites or stress molecules on cell surfaces)
