CVS- 1 and 2 Flashcards
How to single celled organisms obtain O2 and nutrients?
Diffusion
Why is diffusion not efficient in larger organisms?
Would take too long to obtain nutrients so they need a gas exchange and circulatory system
How does the CVS work?
A mechanism that transporting substances close to the cells to allow diffusion to take place.
How does blood exchange oxygen and nutrients with cells?
Diffusion - the CVS provides the correct conditions for diffusion to occur at tissues and lungs.
Where does diffusion take place? What are the type of cells and what are they surrounded by?
Capillaries - single endothelial cells surrounded by basal lamina
What molecules can diffuse directly through the bilayer? (2)
Oxygen and Carbon dioxide
How do large molecules such as glucose, amino acids and lactate (water soluble molecules) diffuse into capillaries?
Through pores in the capillaries.
What effects the rate of diffusion? (3)
Explain how they effect the rate.
Area - determined by how many capillaries per unit volume (capillary density). Large area = greater diffusion. Tissues that are more metabolically active have more capillaries.
Diffusion Resistance - nature of molecule (large molecule = slower), nature of barrier (hydrophillic diffuse more readily if there’s pores) and path length (Shortest path = greatest diffusion).
Concentration gradient - greater gradient = greater diffusion
What must be maintained for diffusion to continue?
Concentration gradient
If there is a lower blood flow, would there be an increase or decrease in the number of capillaries?
Decrease - lower capillary concentration
What is the rate of blood flow called?
Perfusion rate
What is the blood flow at rest in litres.min-1?
5 l.min-1
What is the blood flow to the brain, heart and kidneys? And describe the flow?
Brain 0.5ml min -1 g-1 (High, constant flow)
Heart 0.9 to 3.6 ml min-1 g-1 (High flow, increases with exercise)
Kidneys 3.5ml min-1 g-1 (High, constant flow)
What is the rate of blood flow during exercise in l.min-1?
25 l.min-1
What four components make up the CVS?
Pump = heart
Distribution system = vessels and blood
Exchange mechanism = capillaries
Flow control = arterioles and pre capillary sphincters
What are the resistance vessels in the CVS?
Arterioles and pre capillary sphincters
What does blood flow through when it leaves the heart?
Heart - arteries - arterioles - capillaries - venules - veins - heart
Where is the temporary store of blood kept? And why?
Veins - thin walls, easily distend/collapse, act as a variable reservoir.
Why does the body require a temporary blood store?
What is the store of blood called?
To meet the requirements of the body, blood flow is flexible
Capacitance
What store of blood is kept in the veins, heart, arteries/arterioles and capillaries?
Veins = 67% Heart = 17% Artery/arterioles = 11% Capillaries = 5%
When does blood flow fastest, when cross sectional is at greatest or least?
In what vessels does blood flow fastest and slowest?
Cross section is least
Fastest = Aorta Slowest = Capillaries
What are the three major arterial trunks?
Brachiocephalic artery
Left common carotid artery
Left subclavian artery
What happens to blood pressure in systole? And what part of the heart causes this change?
Blood pressure rises (120mmHg) due to the left ventricle contracting
What happens in diastole? (4)
Aortic semilunar valve closes
Walls of aorta recoil
Blood pressure maintained - moves towards smaller vessels
Aortic pressure drops (70-80mmHg)
What are the three layers of the arteries and veins from inside out?
Tunica intima
Tunica media
Tunica adventitia
Describe the tunica media of the large elastic arteries?
40-70 fenestrated elastic membranes, smooth muscle cells and collagen between lamellae
What is the vasa vasorum?
A network of small blood vessels that supply large blood vessels
What makes up the tunica adventitia in elastic and muscular arteries?
Thin fibroelastic connective tissue containing;
Vaso vasorum
Lymphatic vessels
Nerves
Describe the tunica media of muscular arteries?
40 smooth muscle cells connected by gap junctions for coordinated contraction
What are end arteries?
Terminal artery supplying all or most of the blood to a body part. Undergo progressive branching without development of channels connecting other arteries
Give 4 examples of end arteries.
Main examples = Coronary artery, Splenic artery, Renal artery
Anatomically true = Central artery to retina, Artery of inner ear
What is bridging?
Compression of segment of coronary artery during systole resulting in the narrowing that reverses during diastole