Lecture 8- Blood Vessels

Question 1

Different types of blood vessels

Answer 1

Elastic artery
Muscular artery
Arteriole
Capillary
Venice
Vein
(Coronary artery)

Question 2

Elastic artery function and structure?

Answer 2

Function:
-Very large arteries near the heart witch have ELASTIC WALLS. Expand during systole to store the bolus and push blood to arterial tree in diastole by ELASTIC RECOIL. Smoothing out pulsating flow.

Structure:
-many think sheets of elastin(50-60) in the middle Tunic. Finger sized

Question 3

Muscular artery

Answer 3

Function:

• distribute blood around the body at high pressure and lungs at medium pressure. Rate of flow is adjusted using smooth muscle(vasoconstriction/dilation).
• flow is proportional to the 4th power of radius so small change has big effect

Structure:
Many layers of circular smooth muscle wrapped around the vessel in the middle tunic. Pencil–pin sized

Question 4

Arteriole?

Answer 4

Function:
Control blood flow into capillary beds. They have thicker muscular walls relative to lumen than any other. Greatest pressure drop due to greatest resistance to flow.
-degree of resistance determines the TOTAL PERIPHERAL RESISTANCES and this affects the MEAN ARTERIAL BLOOD PRESSURE.

Structure:
- between 1-3 layers of circular smooth muscle wrapped around the vessel in the middle tunic. About the size of hair (15-300um).

Question 5

Capillary?

Answer 5

Function:

• tiny vessel which are thin walled to allow exchange.
• blood flow is slow to allow exchange and for plasma to escape. Most plasma immediately returns due to osmosis.

Structure:

• diameter just wide enough for RBC( 5-10um)
• single layer of endothelium w. external basement membrane
• no smooth muscle or connective tissue.
• have precapillary sphincters

Question 6

Venule?

Answer 6

Function:

• low pressure vessels that drain capillary beds
• site of WBC leaving blood during infection

Structure:

• small venues have usual endothelium + little connective tissue
• larger ones also have a single layer of smooth muscle
• upto 100 RBC diameter

Question 7

Vein?

Answer 7

Function:

• thin walled low pressure vessels which drain blood to atria.
• thin, soft easily stretched walls
• small change in venous blood pressure causes large change in venous volumes
• 64% of blood is in systemic venues compared to 13% in systemic arteries and arterioles

Structure:

• similar to muscular artery but much thinner walls for their size.
• larger veins have valves
• venous skeletal muscle pump helps return blood.

Question 8

Coronary arteries?

Veins?

Answer 8

-arise from the aorta just down stream from the Aortic valve
-critically important
Right and left coronary artery

Cardiac veins drain back to atria but have no clinical importance

Question 9

Problems with coronary artery if narrowed by 20%?

Answer 9

20% reduction of its normal cross sectional area by an atheroma causes significant obstruction.
During exercise the myocardium supplied by this artery runs low on oxygen (ISCHEMIA) causing chest pain (ANGINA). Serious ischemia results in death(INFARCTION) of the local area.

Question 10

Artery-artery junction?

Answer 10

Called ANASTOMOSES and provide collateral circulation to the body. In the case of ischemia in the heart can widen slowly and provide an alternative pathway.

Question 11

Deoxygenated blood from the heart?

Answer 11

Cardiac Veins drain blood into the Atria but are if no clinical importance.

Question 12

Endothelium?

Answer 12

Inner most layer of tunica interna and is continuous with the endocardium lining of the heart.

Question 13

Basement membrane

Answer 13

Middle layer of the tunica interna and provides physical support for endothelial layer.
Framework of collagen gives significant tensile strength providing resilience for stretching and recoil.