CVS

Question 1

What regulates blood flow to tissues?

Answer 1

Control of the Total peipheral resistance. This can be regulated at the arterioles and pre-cappillary sphincters. This is due to the smooth muscle contraction leading to vasodilation. The contraction is regulated by noradrenaline, adrenaline, hydrogen and pottasium ions and adenosine.

Question 2

Describe the distribution of blood in the body

Answer 2

-veins (65%) -arteries (10%) -pulmonary circulation (25%) -cappilaries (5%)

Question 3

What influences rate of diffusion?

Answer 3

-distance that the species must be able to cross over (this includes membrane width) -The size/charge/polarity of the species -The permeability of the membrane to the species -the available surface area for species to pass through

Question 4

What is the max cardiac output approximetly?

Answer 4

25litres/minute

Question 5

Why does being multicellular necessitate a cardiovascular system?

Answer 5

Multicellular organisms have many cells and so only a few are on the peripheral of the organism and able to gain oxygen. The time it would take for the nutrients to reach the innermost cells would result in their death. This is overcome by using the CVS to pump nutrients from the outside to the innermost cells.

Question 6

Why do veins require capacitance?

Answer 6

Ability to store blood in its distencible vessell walls allows for a varying cardiac output.

Question 7

Where does diffusion occur in the human body?

Answer 7

At the lungs and tissues.

Question 8

How does the CVS system force blood to travel around the body?

Answer 8

Creating a pressure difference between the beginning and end of the circulation.

Question 9

What systems have a constant demand for blood?

Answer 9

The kidney and the brain.

Question 10

What must the perfusion rate be for any given tissue and why?

Answer 10

The perfusion rate must meet the demand of the tissues. So that any blood supply must be able to increase to match this demand as it varies.

Question 11

Describe the histology of an elastic artery

Answer 11

Tunica intima: Endothelium (the cells are arranged with long axis in the direction of blood flow). Tunica media: there are 40-60 layers of fenestrated elastic lamella and layers of smooth muscle. Tunica adventitia: Thick elastic lamella and contained within the layers of fibroelastic fibres are vaso vasurum.

Question 12

Describe the histology of a muscular artery

Answer 12

tunia intima is endothelium tunica media has 50 layers of smooth muscle. the adventitia contains unmyellinated nerve fibres for sympathetic stimulation.

Question 13

What is the significance of end arteries? give examples of these.

Answer 13

end arteries are the only source of blood for a particular tissue. There is no collateral circulation and no anastomoses. So occlusion results in ischaimic necrosis of the tissue. 3 such examples are coronary, renal and retina (the retina is the only true end artery with zero collateral circulation.

Question 14

Describe the histology of arterioles

Answer 14

Lumen diameter is less than 0.1mm, Tunica media: thinner with less smooth muscle and in the adventitia lacks the external elastic lamella.

Question 15

Describe the histology of metarterioles

Answer 15

diameter is below 0.1mm, smooth muscle is intermittant, there is also no elastic lamella.

Question 16

Describe the histology of capillaries and the types of and common locations of these types.

Answer 16

cappilaires are one cell thick with a diameter of 7micrometres, media and adventitia are absent entirely. The 3 types of are continuous (standard), fenestrated (like in the kidney and gut) and sinusoidal (like in the liver, spleen and bone marrow).

Question 17

Describe the histology of post cappilary venules

Answer 17

small diameter, low levels of smooth muscle and a thin adventitia.

Question 18

Describe the histolgy of veins and venules

Answer 18

Adventitia is well developed. Smooth muscle is present in the media. Can vary from 50-1000micrometres and contain semilunar valves to facilate venous return.

Question 19

What are venus commitantes? Why are they located where they are?

Answer 19

Venus commitantes are paired veins that travel back up the path of an artery. They are in the same sheath so the pulsatile contraction of the artery aids the venous return.

Question 20

What is the exception to the typical structure of large veins?

Answer 20

The superfical veins of the leg has a muscular tunica media.

Question 21

where are pericytes? what is their function?

Answer 21

They are contractile cells of the endothelium that are involved in angiogenesis (by orchestrating enodothelial differentiation) and are key in the blood brain barrier. They are are also able to differentiate themselves into smooth muscle, fibroblasts and other mesenchymal stem cells.

Question 22

Describe the change in blood velocity are the cardiovascular system

Answer 22

blood is fastest in arteries (50cm/s), slowest in cappilaires (0.35cm/second) and slow in veins.

Question 23

What is the role the 2 elastic lamella around the tunica media in large elastic arteries?

Answer 23

they store elastic potential energy from the injected blood which drives the blood down the artery.