Cardiovascular - Blood Vessels

The Lymphatic System

• Components:

  • Cervical, inguinal, pelvic, lumbar lymph nodes

  • Right and thoracic lymph ducts

  • Spleen, thymus

• Functions:

  • Returns fluids and proteins to circulation

  • Transports absorbed fats

  • Acts as a filter for pathogens

• Features:

  • Vessels contain valves to aid in fluid flow

  • Drains through collecting nodes into large veins and vena cava, and back into heart

Blood Vessels

• Arteries:

  • Function: Carry blood away from the heart and acts as a pressure reservoir

  • Structure: Thick elastic walls with smooth muscle

• Veins:

  • Function: Return blood to the heart and acts as volume reservoirs

  • Structure: Thinner walls of vascular smooth muscles

Blood Pressure and Its Components

• Definitions:

  • Pulse pressure = Systolic pressure - Diastolic pressure

  • Mean arterial pressure (MAP) = Diastolic pressure + 1/3 (Pulse pressure)

• Blood pressure measurement via sphygmomanometry.

• Hypertension is higher than normal MAP

• Hypotension is lower than normal MAP

• MAP ∝ Cardiac output * Resistence_arterioles

• Pressure Change

  • Created by contracting muscles is transferred to blood

  • Driving pressure is created by e ventricles

    • Vessels dilate - bp decreases

    • Vessels constrict - bp increases

  • Volume changes affect bp in cardiovascular system

Factors Influencing Blood Flow

• Blood flow depends on:

  • Pressure gradients (F ∝ ΔP/R)

  • Resistance factors (length, radius, viscosity)

  • Higher the pressure gradient, the greater the fluid flow

• Hydrostatic pressure

  • exerted on the walls of the container by the fluid within, proportional to the height of the water column

  • Once fluid begins to flow through the system, pressure falls w/ distance as energy is lost due to friction

• Fluid flows only if there is positive pressure gradient

  • Depends on the gradient not the absolute pressure. If ΔP is the same, flow is the same

• Resistance Opposes Flow

  • Inversely proportional to resistance F ∝ 1/R

  • resistance increases → flow decreases

  • resistence decreases → flow increases

Poiseuille’s Law

• R = 8Ln/(pi)r⁴ or R ∝ Ln/r⁴

  • Resistance proportional to length of tube; increases as length increases

  • Resistance proportional to viscosity (n); increases as viscosity increases

  • Resistance inversely proportional to radius⁴; decreases as as radius increases

    • small change in radius has a large effect on resistance to blood flow

    • vasoconstriction - decrease in radius; decrease flow

    • vasodilation - increase in radius; increase flow

  • Flow rate = volume of blood that passes a given point in the system/unit time

  • Velocity of the flow is the distance a fixed volume of blood travels ina given period of time

  • MAP ∝ CO * peripheral resistance

Aorta

• Ventricular contraction pushes blood into the elastic arteries causing them to stretch

  • Ventricle contracts

  • SL valve opens, blood ejected from ventricles flows into the ateries

  • Aorta and arteries expand and store pressure in elastic walls (systole)

Arteriolar Resistance

• Control mechanisms:

  • Myogenic autoregulation

    • Role of Calcium

  • Paracrines

    • Active hyperemia vs. reactive hyperemia

    • Adenosine

  • Neural and hormonal signals

  • Sympathetic activity (release of norepinephrine).

  • Local and systemic controls regulate blood flow

    • Vasoconstriction = decreased radius → increased resistance

    • Vasodilation = increased radius → decreased resistance

Local Control

• Endothelial cells

  • lining of all blood vessels

  • act as an ___ organ:

    • paracrine - systemic stimulation

    • autocrine - self-stimulation

  • create a signal to act on vascular smooth muscle

    • Relaxation

      • endothelium-dependent hyperpolarization factor (EDHF/EDRFs)

        • Nitric Oxide (NO)

        • Prostacyclin

      • Mechanotransduction (shear)

    • Constriction

      • endothelium-dependent constriction factor (EDCF)

        • Endothelin-1

        • Thromboxane A2

      • Mechanotransduction (pressure)

Capillary Exchange

• Absence of vascular smooth muscle and elastic tissue reinforcement in capillaries allows for easy exchange of materials:

  • One-cell-thick walls facilitate diffusion

  • Density related to metabolic activity of cells

  • Types: Continuous, fenestrated, and sinusoidal capillaries

Regulation of Cardiovascular Function

• Key components:

  • Cardiovascular control center (CVCC)

  • Baroreceptors monitor blood pressure

  • Responses involve adjusting cardiac output and peripheral resistance

Cardiovascular Disease Risk Factors

• Uncontrollable:

  • Age, sex, genetic predisposition

• Controllable:

  • Lifestyle choices: smoking, diet, exercise

  • Hypertension and diabetes can worsen risks

Atherosclerosis and Its Development

• Characterized by:

  • Hardening of arteries, plaque buildup

  • Factors increasing risk: high cholesterol, obesity, smoking

• Process:

  • LDL accumulation, inflammation, plaque formation

  • Can lead to heart attacks or strokes