Vessels Flashcards
What is an artery?
Blood vessel with thick walls made of collagen that resist the high pressured blood that takes blood away from heart.
It has a narrow liken to maintain the pressure.
It has a lot of elastic tissue to allow for it to stretch to accommodate to surge of blood from ventricles and recoil to maintain pressure
Atereioles fan adjust in diameter to adjust blood supply to certain areas of body by contracting or relaxing smooth muscle
What is a vein?
A blood vessel with little elastic tissue in wall so the walls are thin as blood is travelling at a lower pressure.
Large diameter of lumen to decrease resistance in blood flow to aid returning at low pressure to heart
Outer layer of collagen to resist stretching
Valves prevent back flow of blood
What is a capillary?
A blood vessel with a single endothelium cell thick wall with no elastic tissue to provide short diffusion pathway for exchange of molecules.
Small lumen diameter causes friction with walls and slows blood flow, allowing all molecules to diffuse into surrounding tissue.
Large no. In body to provide large SA for exchange
Small gaps between cells to allow solutes to leak out.
Pressure changes in cardiovascular system
The greatest pressure is in the arteries and pressure fluctuates due to systole and diastole of the ventricles. Then pressure drops from arteries to arterioles to capillaries to veins.
Why do pressure decrease?
A drop in pressure is caused as as the blood is distributed through an ever increasing number of vessels with the arterielles and capillaries having a large cross sectional area due to the extensive network of them.
The arteriolar also have a narrow lumen so resistance from the vessel walls also decreases prsssure.
As pressure drops so does velocity of blood flow, allowing more time for discussion of fluids and oxygen into tissue fluid.
How does pressure graph work?
Nearer to the heart, the greater the pressure, and in arteries and arterioles it fluctuates as it’s synonymous with hearbeat.
As it goes along it rapidly decreases and in vines as muscles context and relax, the pressure begins to increase again
What is tissue fluid?
Tissue fluid is found in space between cells/tissues (interstitial space). Water, O2, nutrients, hormones etc provide the cells with everything they need.
There are no plasma proteins or red blood cells in tissue fluid as too large, but WBC can change shape and enter through pores.
How does tissue fluid leave and enter capillaries?
Fluid moves from cappiliries to interstitial space at the arterial end via high hydrostatic pressure.
Then fluid moves back from interstitial space to venue by osmosis due to water potential difference and water potential is lower in capillaries due to plasma proteins.
Also pressure is lower at venue end so fluid can move back in.
What happens to excess fluid?
Flows into lymph vessels
90% of tissue fluid flow back into circulatory system, but 10% seeps to lymph vessel
The lymphatic system is a weird of blind ended vessels allowing excess fluid to drain and valves prevent the back flow of the tissue fluid
What is lymph fluid?
It consists of tissue fluid from cells.
Also consists of fatty acids and glycerol from digestive tract
Also lymphocytes are found in lymphonodes
Lymph fluid flows back into the bloodstream via the thorasic duct
