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BIO 265 – Human A&P II. Chapter 19 Blood Vessels. Blood Vessels. Amazing fact about blood vessels: 60,000 miles in an adult! Earth’s circumference is 24,902 miles What are the different types of blood vessels? Arteries - elastic, muscular, and arterioles Capillaries

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bio 265 human a p ii

BIO 265 – Human A&P II

Chapter 19

Blood Vessels

blood vessels
Blood Vessels
  • Amazing fact about blood vessels:
    • 60,000 miles in an adult!
    • Earth’s circumference is 24,902 miles
  • What are the different types of blood vessels?
    • Arteries - elastic, muscular, and arterioles
    • Capillaries
    • Veins – venules and veins
  • Figures 19.1 and 19.2 and Table 19.1
blood vessels1
Blood Vessels
  • The inside of a blood vessel is called the lumen
  • All blood vessels have an internal lining called endothelium (it lines the lumen)
    • Simple squamous epithelium
    • This layer is continuous with the endocardium
  • Capillaries:
    • Composed of endothelium with a basement membrane
    • Figure 19.3 and others
structure of arteries and veins
Structure of Arteries and Veins
  • Three tunics or layers:
    • Tunica intima – primarily endothelium
    • Tunica media – location of circular smooth muscle and elastin
      • Functions?
    • Tunica adventitia – layer of connective tissue
      • Merges with other connective tissue around the vessel
      • Also contains the vasa vasorum
    • Figure 19.1 and other figure
structure of arteries and veins1
Structure of Arteries and Veins
  • Veins have valves that only allow blood to flow toward the heart
    • The valve structure and function is very similar to the semilunar valves in the heart
  • Figure 19.1 and other figure
structure of arteries and veins2
Structure of Arteries and Veins
  • The valves in the veins are critical for returning blood to the heart because there is almost no blood pressure in the veins
    • Blood is pumped through the veins by respiration (breathing) and by skeletal muscle contractions
  • Figure 19.6
structure of arteries and veins3
Structure of Arteries and Veins
  • Varicose veins result from these valves not functioning properly
    • Pot-bellies, pregnancy, standing, hemorrhoids
    • Figure 19.6
capillaries
Capillaries
  • What is the function of capillaries?
    • Capillary Exchange
      • gases, nutrients, wastes, etc.
    • Capillary exchange is driven by 2 things:
      • Concentration gradients (diffusion)
        • Most solutes move this way
      • Fluid movement (primarily moves water to the tissues)
        • Tissue swelling and the lymphatic system
    • Figures 19.14, 19.15, 19.2 and others
capillaries1
Capillaries
  • Capillaries are organized into networks called capillary beds
    • Figure 19.4
capillaries2
Capillaries
  • The structure of the capillary beds allows the regulation of blood flow through the tissues
    • This involves the precapillary sphincters
    • Figure 19.4
control of blood flow
Control of Blood Flow
  • Blood flow through tissues (tissue perfusion) is tightly controlled
    • It is related to the metabolic rate and function of the tissue (muscle, liver, kidney, etc.)
    • O2 (and other nutrients) are the key
      • They are required for smooth muscle contraction
    • Figure 19.4
control of blood flow1
Control of Blood Flow
  • Long-term control involves the number of blood vessels and capillaries
    • Muscle and heart attack examples
  • The growth of new blood vessels is called angiogenesis
  • The density of capillaries primarily depends upon O2 concentration
aging of arteries
Aging of Arteries
  • Changes in arteries:
    • Arteriosclerosis – loss of elasticity in the arteries
      • What effects does this have?
    • Atherosclerosis – deposition of material in the arterial walls to form plaques
      • Effect?
      • Figure from other text
blood pressure regulation
Blood Pressure Regulation
  • Blood Pressure depends on 3 primary factors:
    • Cardiac output
    • Peripheral resistance (this is determined by blood vessel diameter)
    • Blood volume
blood pressure regulation1
Blood Pressure Regulation
  • There are two types of regulation:
    • Short-term and Long-term
  • Short-term
    • Baroreceptors – get with a partner and discuss how this mechanism could affect blood pressure.
      • They affect the cardiovascular center in the medulla
      • This can change heart rate and peripheral resistance to raise and lower BP!
      • Figure 19.8
blood pressure regulation2
Blood Pressure Regulation
  • Chemoreceptor Reflexes
    • When oxygen, pH, or carbon dioxide levels change dramatically, the cardiovascular center can increase blood pressure.
  • Adrenal Medulla Hormones
    • What hormones are produced here?
    • These affect heart rate and peripheral resistance
      • Increase heart rate
      • Vasodilation in cardiac vessels
      • Vasoconstriction in vessels to the skin and viscera
blood pressure regulation3
Blood Pressure Regulation
  • Atrial Natriuretic Peptide (ANP)
    • Released when atria are stretched
    • Increases Na+ loss in the urine
    • Also causes vasodilation
    • Effect?
  • ADH (vasopressin) – at very high levels causes vasoconstriction
  • Angiotensin II – vasoconstriction
  • Inflammatory chemicals (like histamine) cause vasodilation
  • Alcohol – inhibits ADH and causes vasodilation
blood pressure regulation4
Blood Pressure Regulation
  • Long-Term Regulation (these alter blood volume):
  • Direct renal filtering
    • High BP causes more fluid to get filtered and lost
    • Low BP slows filtration and loss down
  • Atrial Natriuretic Peptide – effect?
  • Renin-Angiotensin-Aldosterone Mechanism
    • When BP decreases, the kidneys secrete renin
    • Renin activates a plasma protein called angiotensin II
    • Active angiotensin II causes vasoconstriction and the release of aldosterone from the adrenal cortex
blood pressure regulation5
Blood Pressure Regulation
    • Aldosterone increases Na+ and Cl- absorption by the kidney which increases water retention
    • Angiotensin can also stimulate the release of ADH
    • This mechanism is very important for daily regulation of BP and in countering circulatory shock
  • ADH – effect?
alterations in blood pressure
Alterations in Blood Pressure
  • Hypotension (BP below 100 mm Hg) – usually no problem
  • Hypertension (BP over 140/90 mm Hg)
    • Temporary high BP can be normal
    • Strains the heart
    • Contributes to atherosclerosis
    • Can lead to heart failure
    • Cause is usually unknown
circulatory shock
Circulatory Shock
  • Shock is a condition where blood flow is not adequate to meet the body’s needs
    • (Low blood pressure)
    • Hypovolemic shock – blood loss, dehydration, extensive burns
    • Vascular shock – extreme vasodilation
      • Anaphylactic shock
      • Septic shock – bacterial toxins
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