U2 KA5 - The Structure And Function Of Arteries, Capillaries And Veins Flashcards
State the direction of blood through heart and body
Blood is circulated from the heart to the lungs and back. This allows for the deoxygenated blood to become oxygenated before passing throughout the body to meet the respiratory demand of the cells
Describe the Blood Pressure as the Blood Mover Away From The Heart
Decreases
Describe the Function and Function Of Arteries
They carry blood away from the heart
They have a thick middle layer of smooth muscle in the vessel wall
The inner and outer layer of connective tissue surrounding the smooth muscle contains elastic fibres
This enables the walls of the artery to pulsate (allowing stretch and recoil)
The lumen of the artery is narrow in comparison to veins
Describe the Function and Function Of Veins
Veins carry blood towards the heart.
Veins have much thinner layers than arteries. The smooth muscle and layers of elastic fibres are much thinner. This is due to the pressure in arteries being lower.
The lumen of the vein is wider in comparison with arteries, reducing the resistance of blood flow
Valves are present in veins to prevent backflow of blood (necessary due to the low pressure)
Describe the Function and Function Of Capillaries
Capillaries allow exchange of substances with tissues.
Referred to as the exchange vessels
It is only at the capillaries that substances are exchanged (e.g. Oxygen, Carbon Dioxide) between blood and cells take place through the thin walls
The capillary walls are composed of only endothelium which are only one cell thick (allowing efficient exchange)
What is the Smooth Muscle In Arteries Made Of?
Connective tissue and Elastic fibres
Describe Vasodilation and Vasoconstriction
Smooth muscle in arteries can contract or relax depending on the body’s requirements. This results in causing vasoconstriction or vasodilation to control blood flow.
Arteries become dialated increasing blood flow to muscles -> Vasodilation
Arteries constrict, reducing blood flow -> Vasoconstriction
Components of Blood
*Red blood cells
*White blood cells
*Platelets
*Plasma
Describe Pressure Filtration
Blood arriving at capillaries from the arteries is at a higher pressure than that found inside the capillary itself.
This pressure difference causes much of the plasma in the blood to be forced through thin walls
This pressure filtration results in a fluid called tissue fluid.
What is The Main Difference between Tissue fluid and Blood plasma?
Blood contains plasma
proteins which are too large to be filtered through the capillary walls
Name dissolved substances carried in blood plasma
*oxygen
*carbon dioxide
*glucose
*amino acids
*urea
*vitamins
Describe The Movement of fluid in and out of the blood
Fluid moves because of pressure differences.
Fluid leaves blood because hydrostatic pressure exceeds osmotic pressure.
Hydrostatic pressure is the pressure that is exerted by a fluid
Fluid re-enters blood because osmotic pressure exceeds hydrostatic pressure.
Fluid leaves capillaries by pressure filtration.
describe the exchange of materials in tissue fluid
Tissue fluid flows over cells providing substances in high concentration like oxygen and glucose.
At the same time, carbon dioxide and other excreted waste products diffuse out of the cells into the tissue fluid
Products of cells are passed back into the blood e.g. Hormones
What happen to Excess Tissue Fluid
Excess tissue fluid is also absorbed by thin-walled tubes known as lymphatic vessels which are blind-ended tubes located amongst living cells. Tissue fluid that is returned via the lymphatic vessels is known as Lymph fluid.
