Topic 3 Circulatory System: Blood Vessels

Question 1

• Blood transported via arteries, veins, and capillaries rather than soaking organs in blood bath which is seen in organisms with open circulatory systems

Answer 1

Note

Question 2

• Thich-walled, muscular, elastic vessels that pump oxygenated blood away (except for pulmonary arteries that transport deoxygenated blood from heart to lungs)
• Wrapped in smooth muscle, they are typically innervated by the sympathetic nervous system
• Large arteries: have less smooth muscle (per volume) than medium; also less affected by sympathetic nervous system, but medium sized can constrict enough to reroute blood
• Three layers (tunics):
  1. Endothelial lining (inner)
  2. Smooth muscle and elastic tissue (middle)
  3. Connective tissue (outer)

Answer 2

1. Arteries

Question 3

• Small vessels wrapped in smooth muscle and constrict or dilate to regulate blood pressure or reroute blood
• Major determinant of blood pressure as they have greater resistance to blood flow

Answer 3

2. Arterioles

Question 4

• Smallest diameter and have single layer of endothelial cells across which gasses, nutrients, enzymes, hormones, and waste diffuse
• 4 methods for materials to cross the capillary wall
  a. Endo or exocytosis (proteins)
  b. Diffusion through capillary cell membrane (O2 and CO2)
  c. Movement through pores called fenestrations
  d. Movement through space between cells (ions)
• Sometimes you see pericytes (contractile cells) around capillaries and venules throughout the body

Answer 4

3. Capillaries

Question 5

• Capillaries are exchanging with interstitial fluid that surrounds tissue cells
  a. Blood hydrostatic pressure: pressure from flow of blood pushing outward
  b. Blood colloid osmotic pressure: osmotic pressure exerted by blood proteins, usually in plasma; wants to pull water into capillary (oncotic pressure)

Answer 5

Capillary Exchange

Question 6

• Tissue has osmotic and hydrostatic pressure, but they play minor roles

Answer 6

Note

Question 7

• Blood flowing in from capillaries has a high blood hydrostatic pressure, so high that it overcomes the blood colloid osmotic pressure working against it

Answer 7

Capillary

Question 8

• At the capillary end of the bed is fluid moving outward, but towards the end of the end of the capillary bed, blood hydrostatic pressure has decreased enough that blood colloid osmotic pressure overcomes it and fluid flows back inward (net reabsorption) at the venous end

Answer 8

Net Filtration

Question 9

• Regulate passage of blood into capillary beds

Answer 9

Pre-capillary Sphincters

Question 10

• Small blood vessels that lead back to veins and are thin and porous
• Drain blood from capillary bed -> venules combine -> veins

Answer 10

4. Venules

Question 11

• Larger veins have valves to aid in transport of deoxygenated blood back to heart due to fighting gravity (except for pulmonary vein and umbilical veins that carry oxygenated blood)

Answer 11

5. Veins