Blood Vessels

Page 1: Blood Vessels

• Overview of blood vessels and their roles in the circulatory system.

Page 2: Structure of Blood Vessels

Layers of Blood Vessels

• Tunica intima: Innermost layer.

• Tunica media: Middle layer consisting of smooth muscle.

• Tunica adventitia: Outer layer (also called tunica externa).

Types of Blood Vessels

• Veins: Carry blood toward the heart.

• Arteries: Carry blood away from the heart.

• Venule: Small veins that collect blood from capillaries.

• Arteriole: Small arteries leading to capillaries.

• Capillaries: Sites of exchange between blood and tissues.

Page 3: Blood Vessel Anatomy and Hemodynamics

• In both systemic and pulmonary circuits, blood vessels transition from large to small and back to large:

  • Arteries → Arterioles → Capillaries → Venules → Veins

Page 4: Structure of Blood Vessels

Layers of Blood Vessels

1. Tunica externa (Adventitia)

   • Composed of collagen and elastic fibers (loose connective tissue).

   • Anchors blood vessels to surrounding tissues.

2. Tunica media

   • Contains smooth muscle, plays a role in vasomotor functions.

3. Tunica intima (interna)

   • Endothelium (simple squamous epithelium).

   • Basement membrane beneath the endothelium.

Page 5: Blood Vessel Layer Overview

• Tunica externa

• Tunica intima

• Tunica media

Page 6: Functional Differences in Blood Vessels

Structure and Function

• Structural differences between arteries and veins due to their functional roles:

  • Arteries: Thicker walls, smaller lumen.

  • Veins: Thinner walls, larger lumen, contain valves to prevent backflow.

• Capillaries: Composed of tunica intima only, facilitating gas exchange (O2 and CO2).

Page 7: Characteristics of Blood Vessels

Visual Representation

Artery

• Thick outer wall, small lumen.

Vein

• Thin layer of muscle and elastic fibers, large lumen.

Capillary

• Very small lumen, thin outer wall comprised of a single cell layer.

Page 8: Blood Flow Mechanisms

Valve Function

• Valves open in the direction of blood flow toward the heart and close to prevent backflow when the muscle contracts.

Page 9: Arteries Overview

Types of Arteries

• Elastic arteries:

  • Close to the heart, large diameter, lots of elastic fibers.

  • Function to maintain pressure (pressure reservoir).

  • Examples: aorta, common carotid, subclavian.

Page 10: Muscular Arteries

Characteristics

• Smaller in diameter than elastic arteries.

• Located further from the heart, contain more muscle, with thicker walls.

• Examples: brachial artery, radial artery, femoral artery.

Page 11: Arterioles

Function

• Smaller than arteries, control blood flow to tissues through vasodilation and vasoconstriction.

• Considered resistance vessels.

Page 12: Elastic Artery Structure

• Internal elastic membrane present, surrounded by layers of smooth muscle and connective tissue.

Page 13: Blood Vessel Types

Summary of Types

• Elastic artery

• Muscular artery

• Veins

• Venules

• Capillaries

Page 14: Vasoconstriction and Vasodilation

Visualizing Blood Vessel Changes

• Normal state, vasoconstricted state, and vasodilated state illustrated.

Page 15: Capillaries Overview

Characteristics

• Smallest blood vessels (~20 billion in the body).

• Very thin-walled (tunica intima only).

• RBCs pass through in single file, serving as sites for exchange between blood and tissue.

Page 16: Capillary Structure

Components

• Basement Membrane

• Endothelial Layer (Tunica Intima)

Types of Capillaries:

• Continuous, fenestrated, sinusoidal.

Page 17: Continuous Capillaries

Characteristics

• Most common type.

• Composed of endothelium with small gaps allowing for fluid passage and immune cell diapedesis.

Page 18: Fenestrated Capillaries

Characteristics

• Contain pores in their walls for greater permeability.

• Found in high absorption and filtration areas (e.g., intestines, kidneys).

Page 19: Sinusoidal Capillaries

Characteristics

• Very leaky with large gaps between endothelial cells.

• Found in bone marrow, liver, and lymphatic tissues, allowing whole blood cells to enter and exit.

Page 20: Capillary Beds

Network Structure

• Capillary networks with pre-capillary sphincters determine blood flow.

• Vasomotion: Ability of sphincters to constrict or dilate based on need (e.g., exercise vs. rest).

Page 21: Capillary Bed Functionality

Precapillary Sphincters

• Relaxed vs. constricted states illustrated with blood flow direction.

Page 22: Venules and Veins

Characteristics

• Venules: Formed by the joining of capillaries.

• Veins: Formed by joining of venules. – Return blood to the heart with stretchy walls and valves preventing backflow. – Reservoir for 60% of blood at rest.

Page 23: Blood Vessel Anatomy Overview

Structural Layers

• Tunica externa, tunica media, tunica intima details reiterated.

Page 24: Blood Volume in Percentages

• Illustrative description of blood volume content in various scenarios (volunteer donations, etc.).

Page 25: Blood Flow Mechanics

Definitions

• Blood flow: Volume of blood moving through a vessel per time (ml/min).

• Blood pressure: The force against vessel walls (mmHg), generated by ventricular contraction and influenced by volume.

• Resistance: Opposition to flow due to friction.

Page 26: Sources of Resistance

Factors Influencing Resistance

• Blood viscosity: Higher viscosity equals higher resistance, influenced by cell count.

  • Anemia reduces viscosity, while polycythemia increases.

Page 27: Viscosity Comparison

Comparisons of Materials

• Water, olive oil, and honey as examples of varying viscosity levels.

Page 28: Resistance Related to Vessel Length

Length Influence

• Resistance increases as total length of blood vessels increases, though generally constant unless weight affects length.

Page 29: Blood Vessel Width

Diameter and Resistance Relation

• Not constant; smaller diameter leads to greater resistance (related to r in 1/r^4).

• Capillaries have the greatest resistance, larger vessels generally have lower resistance.

Page 30: Flow vs Diameter

Vessel Dynamics

• Relationship illustrated between friction, diameter, and flow rates in blood vessels.

Page 31: Relationship Dynamics

Diameter, Area, Pressure, and Flow Velocity

• Vessel diameter: Decreases from arteries to capillaries, increases from capillaries to veins.

• Pressure: Decreases from arteries to veins, with the largest drop occurring at arterioles.

• Velocity of flow: Decreases with increased cross-sectional area.

Page 32: Blood Pressure Measurement

Dynamics of Blood Pressure

• Overview of average pressures at different vessel types and their diameters.

Page 33: Arterial Pressure Mechanics

Influencing Factors

• Dependent on elasticity of arteries, blood volume, determined by heartbeats and pressure gradients.

Systolic Pressure

• The maximum pressure during ventricular contraction.

Page 34: Blood Flow Derived from Pressure Changes

Movement Mechanics

• Blood flows due to pressure differences; the relaxation phase of the heart allows valves to prevent backflow.

Page 35: Blood Flow Dynamics

Aortic Functionality

• Blood motion explained during contraction and relaxation of the left ventricle, including effects on arterial walls.

Page 36: Pressure Measurement

Pressure Types

• Overview of systolic, diastolic, and mean arterial pressures across different vessel types.

Page 37: Mean Arterial Pressure (MAP)

Calculation and Importance

• MAP calculations and their significance in indicating overall arterial pressure.

Page 38: MAP Details

Surface Operations

• Defines MAP's significance in organ and tissue perfusion.

Page 39: Capillary Pressure Dynamics

Pressure Variation

• Describes the pressure drop from aorta through arterioles to capillaries, necessary for capillary function.

Page 40: Capillary Functionality

Exchange Mechanics

• Importance of capillary hydrostatic pressure and the role of small solutes in nutrient exchange.

Page 41: Venous Pressure Dynamics

Overview

• Steady, low venous pressure and pressure gradients, emphasizing factors aiding venous return.

Page 42: Valvular Function

Illustrative Mechanism

• Shows operational mechanism of valves in facilitating blood return towards the heart.

Page 43: Capillary Exchange Mechanisms

Methods of Exchange

• Types of exchange processes: diffusion, transcytosis, bulk flow, filtration, and reabsorption.

Page 44: Filtration Dynamics

Explanation

• Fluid and material movement from capillaries due to hydrostatic pressure; size of pores dictates passage capabilities.

Page 45: Blood Components

Filtered Substances

• Components leaving capillaries illustrated in relation to interstitial environment influences.

Page 46: Reabsorption Dynamics

Fluid Movement

• Movement back into capillaries via osmotic pressure due to plasma proteins; emphasizes importance of reabsorption mechanics.

Page 47: Key Pressures Comparison

Filtration vs Reabsorption

• Illustrates net filtration pressure, showing variations at arterioles and venules, and emphasizing fluid dynamics.

Page 48: Blood Pressure Maintenance

Influencing Factors

• Factors controlling blood pressure: cardiac output, peripheral resistance, and blood volume; changes in any affect overall pressure.

Page 49: Maintenance Mechanism

Cardiac Output Adjustments

• Explains how heart rate and stroke volume variations affect cardiac output.

Page 50: Blood Volume Control

Kidneys’ Role

• Kidneys control blood volume by removing excess fluids and preventing future losses.

Page 51: Peripheral Resistance Dynamics

Regulatory Mechanisms

• Highlights the importance of varying vessel diameter and blood distribution in controlling blood pressure; neural and chemical pathways involved.

Page 52: Exercise Effects on Cardiac Output

Activity Impacts

• Describes changes in cardiac output during rest versus heavy exercise.

Page 53: Exercise Dynamics

Muscle Blood Flow

• How blood flow to muscles adjusts between rest and heavy exercise conditions, indicating high variability in demands.

Page 54: Neural Control Overview

Mechanisms

• Vasomotor center location and function; always active, slightly constricted muscles.

Page 55: Activity-Based Responses

Changes in Neural Control

• Activity levels affect vasoconstriction and vasodilation mechanisms through neural signals.

Page 56: Baroreceptor Reflex Mechanism

Pressure Regulation

• Activation of baroreceptors in response to pressure changes; implications for vasomotor and cardiac centers.

Page 57: Reflex Mechanics

Response to Blood Pressure Changes

• Overview of the body's mechanisms in reaction to blood pressure fluctuations through vasomotor reflex.

Page 58: Homeostasis in Blood Pressure

Disturbances and Restoration

• Explanation of baroreceptor actions in restoring homeostasis after pressure fluctuations.

Page 59: Chemoreceptor Role

Responses Influencing Blood Pressure

• Influence of peripheral chemoreceptors on vasomotor center response to blood gas changes.

Page 60: CO2 and pH Relationship

Chemical Dynamics

• Explains the chemical interaction between CO2, pH, and the regulatory feedback mechanisms.

Page 61: Homeostasis Disturbances

Restorative Processes

• Chemoreceptor feedback loops aiding recovery from imbalances in blood gas levels.

Page 62: Chemical Control Mechanisms

Hormonal Influence

• Roles of epinephrine and norepinephrine in blood pressure modulation and physiological responses.

Page 63: Renin-Angiotensin-Aldosterone System

Hormonal Responses

• Mechanisms governing responses to low blood pressure and resulting systemic changes.

Page 64: Combined Effects on Blood Pressure

Long-term and Short-term Responses

• Overview of mechanisms elevating blood pressure when disturbed; interplay between short and long-term actions.

Page 65: Antidiuretic Hormone (ADH)

Kidney Interaction

• ADH’s role in regulating water retention and its impact on blood pressure through vascular constriction.

Page 66: Natriuretic Peptides

Blood Pressure Regulation

• Mechanisms behind ANP and BNP's roles in lowering blood pressure through kidney function and vasodilation.

Page 67: Natriuretic Peptides Responses

Regulation Dynamics

• Comprehensive effects following natriuretic peptide release and the resulting bodily chemoregulatory shifts.

Page 68: Nitric Oxide Role

Quick Response Mechanism

• Nitric oxide's function in vasodilation and its short-term effects during periods of increased blood flow.