y3.2: human circulatory system ❣ Flashcards
composition of blood
55% plasma, 45% blood cells and platelets
functions of blood plasma
- plasma transports respiratory gases, nutrients, metabolic waste, hormones
- maintain homeostasis of the body (pH, water potential, temperature)
red blood cells have a weird name.. what is it??
erythrocytes!
structural adaptations of red blood cell to function
1) presence of haemoglobin: binds reversibly with oxygen
2) biconcave shape: increases surface area to volume ratio, increase rate of diffusion of gases
3) no nucleus: allows more haemoglobin to be packed in the cell
4) elastic: to squeeze through blood vessels smaller than itself without breaking
what are white blood cells’ weird name and what are the types of white blood cells?
leucocytes: phagocytes and lymphocytes
structure and function of phagocytes
- irregular in shape, with lobed nucleus so it can squeeze through capillary walls
- engulfs and ingests foreign particles such as bacteria by phagocytosis
- after phagocytosis, vesicles containing pathogens are formed
- vesicles fuse with lysosomes in phagocytes
- the hydrolytic enzymes in lysosomes digest the engulfed pathogen
structure and function of lymphocytes
- round in shape, large nucleus
- lymphocytes produce antibodies, which causes identify and neutralise the pathogen
what are platelets’ weird name?
thrombocytes!
mechanism of blood clotting
- when blood tissues are damaged, damaged tissue and platelets produce thrombokinase
- thrombokinase converts prothrombin into thrombin
- thrombin converts soluble fibrinogen into insoluble fibrin threads that trap blood cells, forming a clot or scab
- fibrin clot tightens as platelets pull on fibrin threads, pulling edge of damaged vessels together to prevent further damage
- strengthen and stablise the fibrin clot, allowing repair of blood vessels to take place
how does body prevent blood clots?
it has a anti-clotting substance called heparin
- thrombokinase neutralises heparin to allow clotting to take place
why cant you donate to incompatible blood types?
antibodies in the recipients’ blood bind to antigens on the donor’s blood cells, causing the blood cells to agglutinate and rupture
what are the advantages of double circulation?
1) complete separation of oxygenated and deoxygenated blood
- ensures only oxygenated blood can reach tissue cells, transported at a high efficiency
2) blood passes through the heart twice in a complete circuit
- blood enters the lungs at a lower pressure, hence flows more slowly through lungs and ensures sufficient time for the blood to be well-oxygenated
- oxygenated blood is distributed to the rest of the body tissues more quickly; maintains high metabolic rate
structure and function of artery
structure
- thick, muscular, elastic walls
- no semi-lunar valves
- small lumen relative to diameter
function
- blood flows AWAY from the heart
- oxygenated except pulmonary and umbilical (2 umbilical arteries)
structure and function of vein
structure
- thinner elastic and muscular wall
- semi-lunar valves present
- large lumen relative to diameter
function
- blood flows TO heart
- deoxygenated blood except pulmonary and umbilical
structure and function of capillary
structure
- one-cell thick epithelium
- very small lumen
function
- allow for exchange of nutrients and waste between blood and tissue fluid
artery structural adaptations to function
1) arterial wall can withstand high blood pressure generated by contraction of ventricles
2) elastic tissue in walls enables it to stretch and recoil under high blood pressure
3) muscular tissue in walls allows for constriction and dilation of artery
structural adaptations of vein
1) large lumen offers low resistance to blood flow
2) semi-lunar valves prevent backflow of blood at low blood pressure to ensure blood flow in one direction
structural adaptations of capillary
1) one-cell thick wall allows oxygen, nutrients, carbon dioxide and waste products to easily diffuse through
2) blood pressure falls to low pressure in capillaries to ensurre sufficient time for exchange of substances to take place
why is there a blood pressure drop from arteries to capillary?
1) due to increase in total cross-sectional area due to extensive branching of capillary
2) blood is further from heart
what are the four main blood vessels?
(left)
- pulmonary veins (from lungs)
- aorta
(right)
- vena cava
- pulmonary artery (to lungs)
why is there a difference in thickness between walls of left and right ventricle
- blood has to be pumped across a longer distance to rest of body compared to lungs
- blood going to lungs should be at a lower pressure to allow blood to flow more slowly and ensure sufficient time for gaseous exchange to take place
- hence, walls of the left ventricle are thicker than right ventricle in order to generate more pressure to pump blood
describe the flow of blood in the left side of the heart from the lungs to the rest of the body
- blood enters the left atrium via the pulmonary artery
- when the pressure in the left atrium is higher than the pressure in the left ventricle, the bicuspid valve opens and blood flows into the left ventricle
- left atrium contracts to force the remaining blood into the left ventricle
- left ventricle contracts and the pressure in the left ventricle increases, pushing against the bicuspid valve and forcing it shut
- when the pressure in the left ventricle is higher than the pressure in the aorta, the semi-lunar valve opens and blood flows to the rest of the body via the aorta
[refer to cardiac cycle graph] what is the order of valves opening and closing?
A: bicuspid/tricuspid valve closes (ventricle > atrium)
B: semi-lunar valve opens (ventricle > aorta/pulmonary vein)
C: semi-lunar valves closes
D: bicuspid/tricuspid valve opens
what are the causes, effects and treatment of atherosclerosis (coronary heart disease)?
- causes: high salt and sugar intake, lack of exercise, family history
- effects: patient may experience angina (heart pain) because heart tissues do not get sufficient oxygen and nutrients due to narrowing of coronary artery lumen; this results in tissue death and heart attack
- treatments: use a stent or coronary artery bypass grafting
