LGS A-Level OCR Biology - Unit 3 - Blood and Blood Vessels
Plasma is the pale yellow liquid component of blood that makes up about 55% of its volume. It transports blood cells, nutrients, hormones, waste products, and heat around the body. Plasma also helps maintain blood pressure and volume.
What is plasma?
Liquid component of blood
Key Terms
What is plasma?
Liquid component of blood
What is the function of plasma?
Transports dissolved substances e.g glucose, amino acids, mineral ions, hormones, albumin and fibrinogens
Why is albumin important?
It helps to maintain osmotic pressure
Why are fibrinogens important?
Involved in blood clotting
What are platelets?
Small fragments of cells
Which is the function of platelets?
Start the process of blood clotting
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| Term | Definition |
|---|---|
What is plasma? | Liquid component of blood |
What is the function of plasma? | Transports dissolved substances e.g glucose, amino acids, mineral ions, hormones, albumin and fibrinogens |
Why is albumin important? | It helps to maintain osmotic pressure |
Why are fibrinogens important? | Involved in blood clotting |
What are platelets? | Small fragments of cells |
Which is the function of platelets? | Start the process of blood clotting |
What triggers blood clotting? | a rough surface - exposure to air |
What is the function of erythrocytes? | -carry oxygen and carbon dioxide around the blood |
What are the characteristics of granulocytes? | lobed nucleus - granular cytoplasm |
What are the characteristics of monocytes? | kidney bean shaped nucleus - cytoplasm not granular |
What are the characteristics of lymphocytes? | large round nucleus - cytoplasm not granularr |
What is the function of granulocytes? | some phagocytic - involved in allergy/inflammation |
What is the function of monocytes? | -involved in defence against pathogens |
What is the function of lymphocytes? | -produces new antibodies |
What are the functions of blood as a whole? | transport of oxygen and carbon dioxide to and from respiring cells transport hormones transport nitrogenous waste products from cells to excretory organs transporting cells and antibodies involved in the immune response helps to maintain steady body temperature acts as a buffer to minimise pH changes |
What are the 3 layers of arteries called? | Tunica intima Tunica media Tunica externa |
What makes up the tunica initima? | squamous epithelial |
What are the functions of the arteries? | Carry oxygenated blood away from the heart apart from the pulmonary artery |
What is bloodflow into arteries like? | high pressure pulsatile fast |
Why do arteries need to maintain high pressure of the arteries? | So that blood can reach tissues in the body |
What makes up the tunica media of the arteries? | Smooth muscle and elastic fibres |
What makes up the tunica externa of the arteries? | Collagen |
What do the elastic fibres in the tunica media of the arteries do? | Stretch to receive blood and recoil between contractions of the heart which helps to maintain pressure and even out bloodflow |
What is the function of collagen in the tunica externa of arteries? | Prevents blood vessels from bursting under high pressure |
Why is the tunica initmia of arteries smooth? | So blood flows over it easily |
What does contact of blood with artery walls cause? | friction slows blood down evens out pulsatile flow |
What is the function of laminas? | Separate the inner from middle and the middle from outer |
What is the function of basement membranes? | Anchors the endothelium to the connective tissue and supports endothelial cells |
What is the function arterioles? | regulate the flow of blood into capillaries |
Do arterioles have a higher proportion of smooth muscle than arteries? | Yes |
What is the function of the smooth muscle? | It is neuronally stimulated causing vasoconstriction of vasodilation which controls the flow of blood into capillaries e.g during body temperature regulation |
Why do arterioles have a lower proportion of elastin in their walls compared to arteries? | The blood flow isn't very pulsatile |
Why is blood slower in the arterioles? | Due to friction with the vessel walls |
How does the slightly wider lumen in arterioles affect pressure? | Reduces it slightly |
What is the function of capillaries? | To exchange substances between the blood and tissues |
What is the advantage of capillaries being one cell thick? | Gives a short diffusion path |
What is the advantage of blood flow being slow through capillaries? | Gives a longer time for the exchange of substances |
Why is the blood flow low pressure through capillaries? | Prevents them from bursting | Pressure is spread across many vessels |
What is blood flow like through capillaries? | Smooth, low pressure, slow |
What is the function of venules? | to link capillaries to veins |
What are the walls of venules mostly made of? | Collagen |
Why do venules have a thin tunica media? | low pressure flow doesn't require muscle or elastic fibres |
Why do veins have a wide lumen? | To accommodate the large volume of blood carried |
What is the blood flow through veins like? | Very slow, low pressure, smooth |
Why are valves present in veins? | Prevent backflow |
What 3 mechanisms aid blood flow back to the heart? | -Movement of skeletal muscles contract/relax and push blood through veins as they lie near the surface -Pocket valves prevent backflow -Breathing mechanism causes negative pressure in the thorax so pulls blood towards the heart |