Blood Vessels Flashcards
Name the 5 types of blood vessel
-arteries
-arterioles
-capillaries
-venules
-veins
What is the function of arteries?
Carry blood AWAY from the heart at high pressure to the rest of the body.
What is the function of arterioles?
Carry blood, still at relatively high pressure, to the tissues.
What is the function of capillaries?
Carry blood as close as possible to individual cells within tissues and organs
What is the function of venules
They carry blood, now at very low pressure, away from the tissues. (Similar to arterioles)
What is the function of the veins?
Carry blood, at very low pressure, back to the heart
Explain the structure of arteries and how this helps to carry out their function.
-lumen: the sace where blood flows, is relatively small = keeps the blood under pressure
-túnica íntima: the lining of the artery, is a thin and smooth layer = helps blood flow along with as little friction as possible
-tunica media: made of smooth muscle and elastin = elastin allows walls to stretch outwards as a pulse of blood is forced into it. As blood pressure falls, elastin recoils inwards again
-tunica externa: a tough fibrous layer around the outside of the artery = protects artery from damage as we move around and our skeletal muscles contract and relax
Explain the structure of arterioles and how this helps to carry out their function.
-have very little elastic tissue in their walls
-have relatively more smooth muscle then in larger arteries = allows for vasoconstriction and vasodilation, controlling amount of blood to tissues
-lumen is made smaller when muscle contracts = can be used to divert blood from one area to another and impact blood pressure
Explain the structure of capillaries and how this helps to carry out their function.
-very tiny: red blood cells have to pass through in single file = red blood cells get as close as possible to the cells in surrounding tissue speeding up diffusion AND rate of blood flow is reduced as blood moving more slowly so more opportunity for gas exchange to occur
-thin: capillary made of single layer of thin, squamous endothelial cells = speeds up gas exchange with tissues
-tiny gaps between endothelium cells: allow for substances to be exchanged between the capillaries and tissues and for phagocytic monocytes to leave circulation when they become macrophages when they migrate into tissues
What is the blood brain barrier?
Capillaries in the brain are less permeable than capillaries found elsewhere in body = this is a protective measure which makes the brain less vulnerable to blood-borne infections/ drugs. The lack of permeability only allows glucose to be used as a respiratory substrate and explains the need for a minimum blood-glucose concentration to remain conscious
Explain the structure of venules and how this helps to carry out their function.
-have a thin wall of muscle and elastic tissue = speeds up collection of blood from capillaries
Explain the structure of veins and how this helps to carry out their function.
-the lumen: larger than the lumen of the artery = provides less resistance to blood therefore easing its journey back to the heart, as blood is under low pressure and flows more slowly
-tunica intima: the lining of the vein is a thin, smooth layer = helps blood flow with as little friction as possible
-tunica media: layer of smooth muscle and elastin is much thinner in a vein compared to in the artery = walls don’t have to withstand blood at high pressure and no stretch or recoil effect
-tunica externa: tough fibrous layer around outside of vein = protects vein from damage as we move around and our skeletal muscles contract and relax
What is the importance of veins having valves?
-valves are found at intervals meaning that the length is divided into sections with valves controlling the the flow of blood from section to section
-because of the large lumen, blood is under low pressure and subject to gravitational forces when returning to the heart from the legs
-the valves ensure that the blood can only go one way towards the heart
How do the valves in the vein work?
-pressure of any kind from the surrounding body tissues squeezes the vein
-any blood moving back towards the capillaries, and not to the heart, closes the nearest valve, preventing backflow
-valves close when the pressure in front of them is greater
-valves open when the pressure behind them is greater
