vasculature and blood cells Flashcards
what is vasculature
network of blood vessels in the body or within an organ
types of blood vessels
arteries, veins and capillaries
where does the gas exchange happen
in capillary bed (O2 and CO2)
layers of an artery and a venule
tunica interna (intima), tunica media and tunica externa (tunica adventitia)
what type of cells line the lumen
endothelium
what forms the tunica interna (intima)
layer of epithelial cells (endothelium)
what forms the tunica media
smooth muscle and elastic tissue
what forms the tunica externa (tunica adventitia)
connective tissue
what is the difference between the layers of arteries and venules
tunica media in arteries:
- thicker because it has to pump blood around body
- less elastic fibres, mostly smooth muscle
- small lumen compared to wall thickness
what happens if arteries are constricted
blood pressure goes up
what is an anastamosis
point where 2 blood vessels join/merge
there is communication between arterial branches
what is the advantage of anastomosis
it gives an alternative route for blood supply if one fails - collateral circulation
what is the circle of willis
anastomoses at the base of the brain - very important for brain blood supply - blood can come from another vessels if one is blocked
what is atherosclerosis
an inflammatory disease where cholesterol enters the vessel wall - build up of fat in the vessel wall
what are the consequences of atherosclerosis
it narrows lumen and render wall less elastic
more resistance to blood
less blood circulation
myocardial infarction or stroke
what causes myocardial infarction or stroke
fat particles on the vessel wall fall off and get into the bloodstream - can cause a blockage - embolia
what are capillaries
smallest blood vessels, exchange vessels
wall of capillaries
only tunica intima:
single layer of endothelial cells and basement membrane - this makes them very permeable for gas exchange
the 3 structural type of capillaries
continous, fenestrated and sinusoid
characteristics of continuous capillaries
complete basement membrane endothelial layer (tunica intima) has intercellular clefts to allow proteins in
characteristic of fenestrated capillaries
complete basement membrane
fenestrations in endothelial layer
in kidneys and luver for nutrient exchange
characteristics of sinusoid capillaries
incomplete basement membrane intercelular
two types of venules
post capillary and muscular
characteristics of post capillary venules
smallest, no tunica media, sparse tunica externa very porous site of white blood cell migration
characteristics of muscular venules
microscopic
tunica media 1-2 layer of smooth muscle
sparse tunica externa
no more exchange with interstitial fluid
how is pressure in veins
low pressure
layers of veins
large lumen
poorly developed tunica media
what causes varicose veins
vein walls loose elasticity -> they weaken and dilate
incompetent valves so backflow can’t be prevented
abnormal blood flow so veins dilate even more
what is blood
the fluid of the circulatory system (plasma and cells)
functions of blood
- transportation: nutrients and waste (co2)
- protection: immune system
- regulation: hormones, proteins, etc
what is haematopoiesis
blood production
what is haemorrhaging
blood loss
blood components (4)
- red blood cells (erythrocytes)
- white blood cells (eukocytes) less than 1%
- platelets (thrombocytes) involved in clotting - block a leakage
- plasma
where are blood cells produced
in bone marrow (inner bone) and in kidney
what forms the red blood cells
haemoglobin protein
no nucleus
what is anaemia
low number of erythrocytes - low iron
functions of white blood cells (leukocytes)
protection and phagocytosis
major classes of leukocytes
- granulocytes: neutrophils, eosinophils and basophils
2. agranulocytes: lymphocytes and monocytes
abnormal leukocyte levels
leukopenia: low white blood cell count -> infection
leukocytosis: high white blood cells -> inflammation
what are platelets (thrombocytes)
cell fragments which control blood loss
platelet counts
normal: 150,000-450,000 platelets/uL
thrombocytosis: >450,000 - blood test
thrombocytopenia: <150,000 - they’ll bleed out and take longer to clot
what is plasma
is the straw-coloured liquid in which the blood cells are suspended
half of our blood is made of plasma
composition of plasma
- water: 92%
- proteins - major protein= albumin involved in water regulation
- glucose
- electrolytes
