topic 5 pt 1

• What percentage of blood circulation is attributed to systemic circulation?

  84%
• What is the composition of the tunica intima in blood vessels?

  Endothelium, basement membrane, lamina propria, and internal elastic membrane
• What is the function of smooth muscle cells in the tunica media?

  They regulate blood flow through vasoconstriction and vasodilation
• What happens during vasoconstriction?

  Smooth muscles contract, leading to a decrease in blood flow
• What is the role of the tunica externa/adventitia?

  It provides connective tissue support for lymphatic vessels and nerves
• What are elastic arteries characterized by?

  Large diameter and abundant elastic fibers
• How do muscular arteries differ from elastic arteries?

  Muscular arteries have thick walls with ≥25 layers of muscle
• What is the primary function of arterioles?

  To regulate blood flow to capillaries
• What are veins characterized by?

  Thick tunica externa, thin tunica intima and media, and large lumens
• What is the function of valves in veins?

  To prevent backflow of blood
• What are capillaries primarily designed for?

  Rapid exchange of nutrients between blood and interstitial fluid
• How do substances move through capillary walls?

  Through diffusion and filtration
• What are the three types of capillaries and their characteristics?

  • Continuous: No gaps, found in brain, muscle, skin
  • Fenestrated: Highly permeable with pores, found in kidneys, endocrine glands
  • Sinusoids: Large diameter and fenestrae, found in liver, bone marrow, spleen

  
• What regulates blood flow through capillary beds?

  The opening and closing of pre-capillary sphincters
• What is the net filtration pressure (NFP) at the arterial end of a capillary?

  NFP is greater than 0, causing fluid to move out of the capillary
• What is the formula for net filtration pressure (NFP)?

  NFP = net hydrostatic pressure - net osmotic pressure
• What is the average cardiac output at rest?

  ~5 L/min
• How does resistance to blood flow relate to vessel diameter?

  Resistance is inversely proportional to vessel diameter raised to the fourth power
• What happens to blood flow during vasodilation of arterioles?

  Blood flow increases due to decreased resistance
• What is laminar flow?

  Streamlined flow with a smooth interior of the blood vessel
• What is turbulent flow and its significance?

  Interrupted flow that can indicate constriction in arteries
• How does the velocity of blood flow relate to vessel diameter?

  Velocity is inversely proportional to the total cross-sectional area of blood vessels
• What are the two types of control for blood flow to tissues?

  • Intrinsic (local) control: Blood flow proportional to metabolic needs
  • Extrinsic control: Integrated control for maintenance of mean arterial pressure (MAP)

  
• What causes localized vasodilation in tissues?

  Increased levels of CO2, H+, K+, adenosine, temperature, and nitric oxide
• What is the role of nitric oxide in blood flow?

  It is a potent vasodilator synthesized by vascular endothelial cells
• What are the local vasoactive substances that affect blood flow?

  • Vasodilators: histamine, bradykinins, prostacyclins
  • Vasoconstrictors: endothelin-1, leukotrienes, thromboxane-A2
• How does myogenic control affect blood flow?

  Passive stretch causes vasoconstriction, while decreased stretch causes vasodilation
• What is the role of sympathetic vasoconstrictor fibers?

  They innervate arterioles to regulate vasoconstriction and vasodilation
• How does venous return occur?

  Due to the pressure gradient between venules and the right atrium
• What hormones are involved in extrinsic control of blood flow?

  Epinephrine, norepinephrine, angiotensin II, ADH, and ANP
• What effect does adrenaline have on blood vessels?

  It causes vasoconstriction in some vessels and vasodilation in others
• What is the effect of angiotensin II and ADH on blood vessels?

  They act as vasoconstrictors