Lecture 2 blood vessels

Blood Vessels

• Introduction to blood vessels encompassing arteries, veins, and capillaries.

Hemodynamics of Blood Flow

• Systemic Circuit: Supplies blood to the head, upper limbs, trunk, lower limbs, and digestive tract.

• Pulmonary Circuit: Responsible for blood flow to and from the lungs.

Hemodynamics Explained

• Definition: Hemodynamics refers to the physical principles governing pressure, flow, and resistance in the cardiovascular system.

  • Terms:

    • Hemo - Greek for blood

    • Dynamic - Relates to motion and forces.

Components and Functions of the Vascular System

• Functions:

  • Delivery of oxygen and nutrients.

  • Removal of waste from tissues.

• Components:

  • Arteries and arterioles

  • Capillaries

  • Venules and veins

Composition of Blood Vessels

• Tunica Externa (Adventitia):

  • Outermost layer made of fibrous and connective tissues for support.

• Tunica Media:

  • Middle layer largely made of smooth muscle, regulates vessel diameter.

• Tunica Intima:

  • Inner elastic layer with adjacent endothelial cells.

Types of Blood Vessels: Comparison

• All Blood Vessels: Have three layers except capillaries and venules.

  • Tunica Intima: Has smooth, slippery endothelium.

  • Tunica Media: Contains smooth muscles capable of vasoconstriction and vasodilation.

  • Tunica Adventitia: Merges with surrounding connective tissue.

Composition of the Arterial System

• Arteries: Thick-walled, elastic fibers that stretch and recoil with cardiac cycles.

• Arterioles: Function as resistance vessels, controlling blood flow into capillaries.

Effects of Peripheral Resistance and Regulation of Blood Flow

• Equation: Blood pressure (BP) = Cardiac Output (CO) × Peripheral Vascular Resistance (PVR).

  • CO: Variable with changes in physical activity and physiology.

  • PVR: Regulated by baroreceptor reflexes.

• Factors Affecting Hemodynamics:

  • Volume

  • Pressure

  • Resistance

Understanding Blood Volume & Bleeding

• Venous Bleeding: Darker red blood, slower but can be life-threatening.

Blood Vessel Structures

• Capillaries:

  • Made of a single endothelial layer.

  • Site for gas and nutrient exchange.

• Veins:

  • Thin-walled and compliant with various diameters, including large, medium, and small.

Venous System

• Low-pressure system returning blood to the heart; central venous pressure (CVP) measured near right atrium (8-12 mmHg).

• Function of Valves: Prevent retrograde blood flow, assists in forward movement against gravity.

Compliance in Blood Vessels

• Definition: Ability to change volume with minimal increase in transmural pressure.

  • Formula: Compliance (C) = Volume (V) / Pressure (P).

  • Veins are significantly more compliant than arteries.

Heart Failure and Cardiomyopathy

• Impacts peripheral regions, may lead to manifestations like edema.

Detailed Analysis of Heart Failure Dynamics

• Right-Sided Heart Failure: Leads to venous congestion and peripheral edema.

• Increased pressure in pulmonary circulation can be caused by chronic lung disease.

The Importance of the Microcirculation

• Components:

  • Arterioles, capillaries, and venules facilitate nutrient and waste exchange.

• Capillary Exchange Functionality: Guided by hydrostatic and osmotic pressures.

Regulation of Blood Flow

• Autoregulation: Driven by blood vessel tone under local tissue conditions (Oxygen levels, metabolites).

• Humoral Regulation: Involves various substances like norepinephrine and epinephrine.

The Lymphatic System Overview

• Derived from interstitial fluids, filters through lymph nodes to remove pathogens.

Fluid Movement Determinants

• Influenced by various pressures including intracapillary fluid and interstitial fluid pressures.

Edema Awareness

• Defined as excess interstitial fluid caused by several factors including capillary pressure imbalances.

Autonomic Control of Cardiovascular Function

• Control centers located in the medulla oblongata consist of vasomotor and cardioinhibitory centers.

Baroreceptors and Chemoreceptors

• Monitor changes in blood pressure, oxygenation, carbon dioxide, and pH.

Key Summary Points

• Blood vessel structure and function tied to hemodynamics, peripheral resistance, and regulation of blood flow.