Session 1 Flashcards
What are the three main factors affecting diffusion?
Area available for exchange, difficulty of movement through the barrier (‘diffusion rate’) and concentration difference (‘gradient’).
Define capillary density
Area available for exchange in a tissue is determined by how many capillaries there are per unit volume
What is the normal cardiac output for a young adult male at rest?
What is the normal cardiac output for a young adult female at rest?
Male - 5.6l/min
Female - 4.9l/min
Avg figure is 5 l/min
What are the key functions of the CVS?
Deliver between 5 & 25 l/min of blood to the body
Maintain a blood flow of 750ml/min to the brain at all times
Maintain blood flow to the heart muscle and kidneys at all times
How does the CVS regulate flow?
Via resistance vessels e.g. arterioles and pre-capillary sphincters
Describe the cardiac output to the major organs
Brain - constant 0.5ml/min/g
Heart - at rest 0.9ml/min/g, can go up to a 4 fold increase
Gut (and liver) - at rest 1ml/min/g, increases during digestion
Skin - 0.01ml/ml/g and can increase to 1.5-2 during thermoregulation
How is the cardiac output split?
11% in arteries and arterioles
5% in capillaries
17% in heart and lungs
67% in veins
Define artery
A vessel that carries blood away from the heart to supply the organs and tissues of the body
What are the two types of arteries?
Elastic (conducting) and muscular (distributing)
Describe how arteries split
Muscular arteries split into arterioles which then split into metarterioles which split into capillaries
What is the function of arterioles?
Regulate the amount of blood reaching an organ or tissue, and more generally in regulating blood pressure.
Describe capillaries
Mostly one cell thick and allow exchange of substances. Can be fenestrated or continuous. Both types can be surrounded by pericytes.
Describe sinusoids
A category of vessels found in the liver, spleen and bone marrow. Generally larger in diameter than capillaries and may contain special lining cells and an incomplete basal lamina.
How does the structure of veins and arteries differ?
Veins have thinner walls and their lumen is wider and more irregular.
Describe veins
Usually contain semilunar paired valve which permit blood flow in one direction. These veins are narrower than 1mm in diameter. Those in thoracic and abdominal cavities don’t have valves.
Give a few examples of places where blood vessels do not reach
Cartilage, epithelia, cornea
Outline how the CVS splits
Heart –> large (elastic/conducting) arteries –> medium arteries –> arterioles –> metarterioles –> capillaries –> post capillary venules –> venules –> medium veins –> large veins –> heart
What vessels enter and leave the heart and where?
Superior/inferior vena cava goes into RA
Pulmonary artery leaves RV
Pulmonary vein enters LA
Aorta leaves LV
Describe the paths of the arteries leaving the heart
Pulmonary trunk bifurcates into left pulmonary arteries that enter the lungs
In abdominal cavity aorta bifurcates into left and right iliac arteries in the pelvis
Define systole
Left ventricle contraction causes increase in blood pressure in aorta. Walls of the elastic aorta stretch.
Define diastole.
Describe the ventricular diastole
Relaxation of the heart.
Aortic semilunar valve closes. Walls of aorta recoil, maintaining pressure on the blood and moving it towards smaller vessels.
What do elastic arteries do?
Conduct blood away from the heart and also act as pressure reservoirs. They act as auxiliary pumps during diastole, giving back elastic energy stored during systole.
Describe the structure of large arteries
Tunica intima - endothelial cells with long axes oriented parallel to long axis of artery, narrow subendothelium of ct with internal elastic lamina
Tunica media - 40-70 fenestrated elastic membranes, SM and collagen between lamellae. Thin external elastic lamina
Tunica adventitia - fibroelastic membranes, vasa vasorum, lymph and nerve fibres
Describe the composition of muscular arteries
Tunica intima - endothelium, subendothelial layer and thick elastic lamina
Tunica media - 40 layers of SM (gap junctions), prominent external elastic lamina
Tunica adventitia - fibroelastic ct, vasa vasorum, lymph and nerves
How does vasoconstriction occur?
Noradrenaline diffuses through fenestrations in external elastic lamina. This depolarises some of the superficial smooth muscle cells. Depolarisation is propagated to all cells of the tunica media via gap junctions
Define the term end artery
A terminal artery supplying all or most of the blood to a body part without significant collateral circulation.
Describe the composition of arterioles
1-3 layers of smooth muscle in tunica media, thin internal elastic lamina (only in larger arterioles)
Small arterioles - single SM cell that completely encircles the endothelial cells. No external elastic lamina, tunica adventitia is scant
Describe the composition of metarterioles
SM layer is not continuous
Where are continuous capillaries found?
Nervous, muscle and connective tissues, exocrine glands and lungs. Cells are joint by tight or occluding junctions
Where are fenestrated capillaries located?
Parts of the gut, endocrine glands and renal glomerulus
What are venae comitantes?
Deep paired veins that (in certain anatomical positions) accompany one of the smaller arteries on each side of the artery. Wrapped together in a sheath. Pulsing of the artery promotes venous return within the adjacent, parallel, paired veins.
What is pericarditis?
Inflammation of the pericardium. If there is a massive build up of fluid it could lead to tamponade.
