Unit 1 Study Guide: The Cardiovascular System

Unit 1 Study Guide: The Cardiovascular System

WEEK 1: Circuits of Blood Flow

  • Systemic Circuit: Carries blood to and from the tissues of the body; primarily associated with the left side of the heart.
  • Pulmonary Circuit: Carries blood to and from the lungs; primarily associated with the right side of the heart.
  • Bonus: Coronary Circuit: Carries blood to and from the heart tissues; associated with the left side of the heart.

Location of the Heart

  • Body Cavity: The heart is located in the mediastinum.

Protective Membranes Surrounding the Heart

  • Fibrous Pericardium:

    • Made of dense irregular connective tissue.
    • Functions as a tough outer sac that protects and anchors the heart.

  • Serous Pericardium: Consists of two layers:

    1. Parietal (Serous) Pericardium: Most superficial layer that contacts the thoracic cavity.
    2. Visceral (Serous) Pericardium: Most deep layer that contacts the heart.

  • Pericardial Sac: Structure formed by the fusion of the fibrous and serous pericardium.

  • Pericardial Fluid:

    • Found between the parietal and visceral pericardium.
    • Function: Prevents friction when the heart beats.

Layers of the Heart Wall

  • Epicardium:
    • Contains blood and lymphatic vessels that supply the heart.
  • Myocardium:
    • Made up of cardiac muscle fibers; nutrients are supplied by the coronary arteries of the epicardium.
  • Endocardium:
    • Lines heart chambers and valves.

Gross Anatomy of the Heart

  • The heart is composed of four chambers and several vessels. Specific structures include:
    • Right Atrium: Contains the interatrial septum, fossa ovalis, and pectinate muscles.
    • Tricuspid Valve: Gateway between the right atrium and right ventricle (Right Atrioventricular Valve).
    • Right Ventricle: Contains the interventricular septum and pulmonary semilunar valve.
    • Trabeculae Carne: Bundles of cardiac muscle in the ventricles.
    • Papillary Muscles: Prevent blood backflow into the atria.
    • Chordae Tendineae: Attach to papillary muscles; prevent valve prolapse.
    • Left Atrium: Collects oxygen-rich blood from the pulmonary veins.
    • Bicuspid Valve: Gateway between the left atrium and left ventricle (Mitral Valve).
    • Left Ventricle: Contains the aortic semilunar valve.
    • Has the thickest myocardium to generate pressure for systemic circulation.

Blood Flow Through the Heart

  1. Blood enters the right atrium from the SVC, IVC, and Coronary Sinus (systemic circulation).
  2. Blood moves through the right atrioventricular (tricuspid) valve into the right ventricle.
  3. Right ventricle contracts, opening the pulmonary valve, leading to the pulmonary trunk.
  4. Pulmonary trunk divides into right and left pulmonary arteries.
  5. Blood is distributed to lungs to deposit CO2 and load O2.
  6. Oxygen-rich blood returns to the left atrium via pulmonary veins.
  7. Blood moves through the left atrioventricular (bicuspid/mitral) valve to the left ventricle.
  8. Left ventricle contracts, forcing the aortic semilunar valve open, ejecting blood into the aorta.
  9. Blood travels through the aorta's branches to tissues, facilitating gas exchange (O2 unloads, CO2 loads).

Oxygenation Status of Blood

  • Pulmonary Arteries: Oxygen poor.
  • Pulmonary Veins: Oxygen rich.
  • Right Atrium: Oxygen poor.
  • Right Ventricle: Oxygen poor.
  • Left Atrium: Oxygen rich.
  • Left Ventricle: Oxygen rich.
  • Aorta: Oxygen rich.
  • Superior/Inferior Vena Cava: Oxygen poor.

Myocardium of the Heart

  • Thickest Myocardium: Found in the left ventricle, necessary for strong contractions to propel blood throughout the body.

Heart Valves

  • Primary Function: Ensure one-way blood flow; prevent backflow (regurgitation).
  • Pressure Differences:
    • Blood flows from high pressure to low pressure areas; contraction raises chamber pressure to open valves.
Types of Valves

  • Atrioventricular (AV) Valves: Located between atria and ventricles.

    • Bicuspid Valve (Mitral): Between left atrium and left ventricle.
    • Tricuspid Valve: Between right atrium and right ventricle.
    • Open: Blood moves from atria to ventricles when relaxed.
    • Closed: Papillary muscles contract to tighten chordae tendineae, preventing valve inversion.

  • Semilunar (SL) Valves: Located between ventricles and major arteries.

    • Pulmonary: Between right ventricle and pulmonary arteries.
    • Aortic: Between left ventricle and aorta.
    • Open: Ventricular pressure exceeds arterial pressure.
    • Closed: Ventricular pressure is less than arterial pressure.
Valvular Pathologies
  • Valve Stenosis:
    • Valves cannot open fully, restricting blood flow; valves become thickened.
  • Valve Regurgitation:
    • Incomplete valve closure leads to backflow; can arise from damaged papillary muscles.

Anastomosis

  • Definition:
    • An area where two or more blood vessels join, providing collateral blood supply.
    • Prevents loss of nutrient supply if one vessel becomes blocked.

Coronary Circulation

  • Coronary Arteries: First branches off the aorta; provide oxygenated blood to the myocardium.
  • Coronary Sinus: Drains oxygen-poor blood from coronary veins into the right atrium.
Significant Vessel: Anterior Interventricular Artery
  • Known as the widow maker due to its critical supply for the left ventricle; blockage leads to fatal myocardial infarctions.

WEEK 2: Cardiac Conduction System

  • Sequence of Cardiac Conduction:
    1. SA Node
    2. AV Node
    3. AV Bundle
    4. AV Bundle Branches
    5. Subendocardial Network of Purkinje Fibers
  • Intrinsic Pacemaker: SA Node initiates electrical signals independently.
Cardiac Action Potential Phases
  1. Depolarization: Na+ influx via open Na+ channels.
  2. Plateau Phase: Ca++ influx via open Ca++ channels.
  3. Repolarization: K+ efflux via open K+ channels.
SA Node Action Potential Steps
  1. Cation leak channels allow Na+ to gradually enter, causing depolarization.
  2. Voltage-gated Na+ channels open when threshold is reached, fully depolarizing the SA Node cells.
  3. K+ channels open to repolarize the membrane.
  4. Persistent K+ channel opening results in hyperpolarization, starting the cycle anew.
Cardiomyocyte Action Potential Steps
  1. Depolarization: Voltage-gated Na+ channels open.
  2. Inactivation: Voltage-gated Na+ channels inactivate, voltage-gated K+ channels open.
  3. Plateau Phase: Voltage-gated Ca++ channels open, K+ channels remain open.
  4. Repolarization: Ca++ channels close while K+ channels remain open, causing hyperpolarization.

EKG and Cardiac Cycle

  • EKG Components:
    • P Wave: Atrial depolarization.
    • QRS Segment: Ventricular depolarization with overlapping atrial repolarization.
    • T Wave: Ventricular repolarization.
Cardiac Cycle Events

  1. Atrial Diastole:

    • Atria relax, filling with blood, AV valves are closed, no heart sounds.
    • Corresponds to the QRS complex on EKG.

  2. Atrial Systole:

    • Atria contract, AV valves open, SL valves closed, represented by the P Wave.

  3. Ventricular Diastole:

    • Ventricles relax, AV valves closed initially but open when atrial pressure exceeds ventricular pressure, represented by the T Wave.

  4. Ventricular Systole:

    • Ventricles contract, SL valves open when ventricular pressure exceeds arterial pressure, corresponding to QRS complex on EKG.
Heart Sounds
  • S1 (Lubb): Closure of both AV valves during ventricular contraction.
  • S2 (Dupp): Closure of SL valves during ventricular relaxation.
Cardiac Cycle Volume and Pressure Concepts
  • Isovolumetric Contraction: Ventricles contract without changing volume; all valves are closed at this phase.
  • Isovolumetric Relaxation: Ventricles fully relaxed, no change in blood volume as AV valves are closed.
  • End Diastolic Volume (EDV): Volume of blood in ventricles at the end of diastole.
  • End Systolic Volume (ESV): Volume of blood in ventricles at the end of systole.
  • Ventricular Ejection: Blood pushed from ventricles into arteries; occurs when ventricular pressure exceeds arterial pressure.
  • Ejection Fraction: Measure of pumping efficiency; % of blood volume ejected with each contraction.
Dicrotic Notch (Wave)
  • Represents slight increase and subsequent decrease in aortic pressure after the closure of the Aortic SL valve.
Factors Influencing Cardiac Output
  • Cardiac Output (CO): Volume of blood pumped out per minute; influenced by Stroke Volume (SV) and Heart Rate (HR).
  • Equations:
    • CO=(EDV−ESV)xHRCO = (EDV - ESV) x HR
    • CO=SVxHRCO = SV x HR
  • Inversely Related Variables: If HR decreases, SV must increase to maintain constant CO and vice versa.
Definitions
  • Preload: Stretch exerted on the heart's chambers during filling.
  • Contractility: Force of heart muscle contraction.
  • Afterload: Resistance to blood flow the heart must overcome during ejection.
Influence of Preload, Afterload, and Contractility on Stroke Volume

  • Increase Stroke Volume:

    • Increase Preload: More blood returns to heart, leading to more ejection.
    • Decrease Afterload: Less resistance, facilitating easier ejection.
    • Increased Contractility: Greater force of contraction increases blood ejection.

  • Decrease Stroke Volume:

    • Decrease Preload: Less blood returns to heart.
    • Increase Afterload: Higher resistance reduces ejection.
    • Decreased Contractility: Weaker contractions result in less ejected blood.
Frank-Starling Law of the Heart
  • States that increased preload leads to increased contractility and a larger stroke volume, affecting overall cardiac output when HR is constant.
Regulation of the Heart
  • Sympathetic Regulation: Increases HR, BP, SV, and CO; associated with fight or flight responses.
  • Parasympathetic Regulation: Decreases HR, BP, SV, and CO; associated with rest and digest activities.

WEEK 3: Blood Vessel Structures

  • Arterial Tunica Intima:
    • A: Endothelium
    • B: Basement Membrane
    • C: Internal Elastic Lamina
  • Arterial Tunica Media:
    • D: Smooth Muscle Cells
    • E: External Elastic Lamina
  • Arterial Tunica Externa:
    • F: Arterial Tunica Externa
    • G: Vasa Vasora
    • H: Arterial blood flow
  • Vein Structures:
    • I: Endothelium
    • J: Basement Membrane
    • K: Smooth Muscle Layer
    • L: Tunica Externa of Veins
    • M: Vasa Vasorum
    • N: Venous blood flow
    • O: Capillary Endothelium
    • P: Basement Membrane of Capillary
Blood Vessel Layer Functions
  • Tunica Interna: Thinnest layer, allows vessels to stretch.
  • Tunica Media: Controls vasoconstriction and relaxation.
  • Tunica Externa: Provides structural support.

Blood Vessel Supply

  • Upper Limb: Subclavian Artery
  • Head & Brain: Common Carotid Artery
  • Lower Limb/Pelvis: Common Iliac Artery
  • Intestines: Superior Mesenteric Artery
  • Spine: Vertebral Artery
  • Anterior/Lateral Arm: Cephalic Vein
  • Liver, Spleen, Stomach: Celiac Artery
Unpaired Branches of the Abdominal Aorta
  • Celiac Trunk: Supplies liver, gallbladder, stomach, spleen;
  • Superior Mesenteric Artery: Supplies small intestine and portions of the large intestine;
  • Inferior Mesenteric Artery: Supplies portions of the large intestine.

Differences between Veins and Arteries

  1. Layers: Thinner tunica interna and media in veins; lack elastic lamina.
  2. Valves: Veins have flap-like valves preventing blood backflow.
  3. Muscle Layer: Veins have little smooth muscle and rely on skeletal muscle for venous return.
Control of Blood Flow in Capillary Beds
  • Precapillary Sphincters: Regulate blood flow through capillary beds.
    • When open, blood moves through; closed sphincters redirect flow to areas needing nutrients.

Types of Capillaries

  1. Continuous Capillaries: No fenestrations; create the blood-brain barrier.
  2. Fenestrated Capillaries: Small holes; found in kidneys, facilitating filtration.
  3. Sinusoids: Larger openings; located in spleen and liver.
Define Capillary Exchange
  • Capillary Exchange: Movement of substances between blood and interstitial fluid; dominated by diffusion.

Blood Movement through Veins

  • Skeletal Muscle Activity: Key in aiding blood movement through veins.
Largest Blood Reservoirs
  • Veins and Venules: Serve as the largest blood reservoir in circulation.

Peripheral Resistance Factors

  • Peripheral Resistance: Resistance encountered by blood flow within vessels.
    • Lumen Size: Larger diameter decreases resistance.
    • Blood Viscosity: Higher viscosity increases resistance.
    • Vessel Length: Longer vessels increase resistance.
Blood Pressure Regulation
  • Regulating Center: Medulla Oblongata.
  • Hormonal Mechanisms:
    1. Renin-Angiotensin-Aldosterone System: Increases BP.
    2. Epinephrine/Norepinephrine: Modulates vessel diameter, increasing BP.
    3. Antidiuretic Hormone: Stimulation leads to vasoconstriction and increased BP.
    4. Atrial Natriuretic Peptide: Lowers BP.

Immune System Overview

Innate Immune System Response
  • First Line of Defense: Skin, mucous membranes, secreted fluids;
  • Second Line of Defense: Natural Killer cells, phagocytes, inflammation, and fever.
Comparison of Immune Systems
  • Innate: Nonspecific, present at birth, prevents infection.
  • Adaptive: Specific, memory capacity, responds to established infections, relevant in vaccinations.

Lymphatic System

Lymphatic Capillary Function
  • Drain interstitial fluid to lymph nodes for surveillance.
Lacteals
  • Absorb dietary lipids from the digestive system.
Primary Lymphatic Organs/Tissues
  1. Red Bone Marrow: Produces B and T cells, site of B cell maturation.
  2. Thymus: Site of T cell maturation and proliferation.
Secondary Lymphatic Organs/Tissues
  1. Lymph Nodes: Filter lymph and activate immune response.
  2. Spleen: Filters blood, removes dying red and white blood cells.
  3. Lymphatic Follicles: Immune surveillance patches found in various body regions.
Flow of Lymph Drainage
  • Lymph drains to proximal lymph nodes first; critical for evaluating metastasis in cancer.
Spleen Tissue Types
  • White Pulp: Processes dead white blood cells.
  • Red Pulp: Processes dead red blood cells.

Lymphatic Follicles

  • Lack capsules, functioning as masses of immune surveillance cells.