Functional Classification of Blood Vessels

Question 1

Elastic arteries

Answer 1

• Diameter: 1-2cm
• Tunica media is rich in elastin
• Distensible walls
• Elastic recoil creates diastolic blood pressure
• Examples: aorta, pulmonary artery + iliac arteries

Question 2

Conduit (muscular) Arteries

Answer 2

• Diameter: 0.1-1cm
• Tunica media contains more smooth muscle (prevent collapse at bends)
• Autonomic innervation by ANS
• Limits blood loss in trauma
• Examples: radial, cerebral + coronary arteries

Question 3

Arterioles

Answer 3

• Diameter: <0.1cm
• Main resistance vessels- narrow lumen + large numbers
• Main site of blood flow regulation to tissues
• Proximal arterioles: many layers of smooth muscle + rich sympathetic innervation
• Distal arterioles: 1-3 layers of smooth muscle + poor sympathetic innervation

Question 4

Capillaries

Answer 4

• Diameter: 0.004-0.007cm
• Single layer of endothelial cells
• Greatest total cross sectional area
• Blood flow + pressure is at its lowest
• Facilitates: nutrient, gas + waste product exchange

Question 5

Arteriovenous Anastomosis

Answer 5

• Diameter: 0.020-0.135cm
• Wide shunt vessel- bypass capillary beds
• Rich sympathetic innervation
• Nasal mucosa: warm inspired air
• Skin: temperature regulation

Question 6

Veins + Venules

Answer 6

• Venules diameter: 0.05-0.20cm
• Vein diameter: >20cm
• Thin, distensible tunica media- composed of smooth muscle + collagen
• In limbs: tunic intina has pairs of valves to prevent backflow
• Low resistance, capacitance vessels
• Sympathetic innervation to main veins to displace blood in times of physiological stress