Cardiovascular and Respiratory Systems: Study Guide

Cardiovascular System

Overview of the Cardiovascular System

The cardiovascular system is responsible for the circulation of blood throughout the body, delivering oxygen and nutrients to tissues and removing waste products. It consists of the heart, blood vessels, and blood.

• Heart: Muscular organ that pumps blood through the circulatory system.

• Blood vessels: Arteries, veins, and capillaries that transport blood.

• Blood: Fluid that carries oxygen, nutrients, hormones, and waste products.

Blood Flow Through the Heart and Major Vessels

• Tracing Blood Flow: Blood enters the right atrium (RA) from the superior and inferior vena cava (SVC, IVC), passes through the tricuspid valve to the right ventricle (RV), then through the pulmonary valve to the pulmonary artery and lungs. Oxygenated blood returns via the pulmonary veins to the left atrium (LA), passes through the mitral (bicuspid) valve to the left ventricle (LV), and is pumped through the aortic valve into the aorta and systemic circulation.

• Abbreviations: RA, RV, LA, LV, SVC, IVC, PA (pulmonary artery), PV (pulmonary vein), Ao (aorta).

Cardiac Output and Its Regulation

• Cardiac Output (CO): The volume of blood pumped by each ventricle per minute.

• Formula: $CO = HR \times SV$ Where $HR$ is heart rate (beats per minute) and $SV$ is stroke volume (mL/beat).

• Factors Affecting CO: Venous return, cardiac contractility, and heart rate.

• Cardiac Reserve: The difference between resting and maximal cardiac output; relates to the Frank-Starling mechanism, which states that increased venous return stretches the heart muscle, increasing contractility and output.

• Functional Bradycardia in Athletes: Marathon runners may have a lower resting heart rate due to increased cardiac efficiency and reserve.

Cardiac Conduction System and ECG

• Conduction Pathway: SA node → AV node → AV bundle (bundle of His) → right and left bundle branches → Purkinje fibers.

• Action Potentials: Initiate and coordinate heart contractions.

• ECG Deflections:

  • P wave: Atrial depolarization

  • QRS complex: Ventricular depolarization

  • T wave: Ventricular repolarization

  • Isoelectric line: Baseline between P and Q waves

• Arrhythmias:

  • Heart block: Impaired conduction between atria and ventricles

  • Ectopic pacemaker: Abnormal pacemaker site outside the SA node

  • Premature ventricular contraction (PVC): Early heartbeat from the ventricles

  • Fibrillation: Rapid, irregular contractions

Blood Pressure, Blood Volume, and Vessel Compliance

• Blood Pressure (BP): The force exerted by blood on vessel walls; directly related to blood volume.

• Compliance: The ability of blood vessels to expand and contract with pressure changes; arteries are less compliant than veins.

Systemic vs. Pulmonary Circulation

• Systemic Circulation: Delivers oxygenated blood to the body; higher pressure system.

• Pulmonary Circulation: Carries deoxygenated blood to the lungs for oxygenation; lower pressure system.

Structure and Function of Blood Vessels

• Arteries: Thick-walled, high-pressure vessels carrying blood away from the heart.

• Arterioles: Small arteries that regulate blood flow into capillaries.

• Capillaries: Thin-walled vessels for exchange of gases, nutrients, and wastes.

• Veins: Low-pressure vessels returning blood to the heart; contain valves to prevent backflow.

Microcirculation and Autoregulation

• Microcirculation: Blood flow through arterioles, capillaries, and venules.

• Autoregulation: Local control of blood flow by tissues; factors include oxygen, carbon dioxide, pH, adenosine, and nitric oxide.

• Endothelium: Releases factors (e.g., nitric oxide) that control vessel dilation.

Autonomic Nervous System and Circulatory Control

• Sympathetic stimulation: Increases heart rate and contractility, constricts vessels.

• Parasympathetic stimulation: Decreases heart rate.

Key Clinical Skills and Landmarks

• Auscultation: Listening to heart valves for murmurs at specific chest locations.

• Pressure Points: Sites to palpate pulses or control bleeding.

• CPR Landmarks: Correct hand placement for effective compressions.

Major Cardiovascular Structures (Lab)

• Heart Layers: Endocardium, myocardium, pericardium

• Valves: Tricuspid, mitral (bicuspid), pulmonary, aortic

• Major Vessels: SVC, IVC, aorta, pulmonary trunk, pulmonary veins, and arteries

• Other Structures: Papillary muscles, chordae tendineae, interventricular septum

Key Terms and Definitions

Term	Definition
Afterload	Resistance the left ventricle must overcome to circulate blood
Preload	Degree of stretch of cardiac muscle fibers at the end of diastole
Cardiac Contractility	Strength of heart contraction at a given preload
Frank-Starling Mechanism	Relationship between stroke volume and end-diastolic volume
Baroreceptor Reflex	Autonomic response to changes in blood pressure
RAAS	Renin-Angiotensin-Aldosterone System; regulates blood pressure and fluid balance

Lymphatic System

Structure and Function

The lymphatic system returns interstitial fluid to the bloodstream, absorbs fats from the digestive tract, and provides immune defense.

• Lymph Vessels: Transport lymph fluid.

• Lymph Nodes: Filter lymph and house immune cells.

• Organs: Spleen, thymus, tonsils.

Respiratory System

Overview of the Respiratory System

The respiratory system is responsible for gas exchange, supplying oxygen to the blood and removing carbon dioxide. It includes the airways, lungs, and respiratory muscles.

Airway Anatomy and Air Movement

• Conducting Airways: Nose, pharynx, larynx, trachea, bronchi, bronchioles (no gas exchange).

• Respiratory Airways: Respiratory bronchioles, alveolar ducts, alveoli (site of gas exchange).

• Air Flow Path: Nose → nasopharynx → oropharynx → laryngopharynx → larynx → trachea → mainstem bronchi → bronchioles → alveoli.

Clinical Considerations

• Risk of Aspiration: Right lower lobe (RLL) is most at risk due to the anatomy of the right mainstem bronchus.

• Auscultation: Listen to right middle lobe (RML) anteriorly.

• Cricoid Pressure: Used during intubation to prevent aspiration.

• Jaw Thrust: Opens airway by moving tongue away from the posterior pharynx.

Mucociliary Blanket (Ciliary Elevator)

• Function: Traps and moves particles out of the airways via ciliary action.

Pulmonary and Respiratory Circulation

• Pulmonary Circulation: Delivers deoxygenated blood to the lungs for oxygenation.

• Bronchial Circulation: Supplies oxygenated blood to lung tissue.

Alveolar Cells

• Type I Cells: Thin, facilitate gas exchange.

• Type II Cells: Produce surfactant to reduce surface tension.

Gas Laws and Pressures

• Partial Pressure: Pressure exerted by a single gas in a mixture.

• Relationship to Volume: Boyle's Law: $P_1V_1 = P_2V_2$

Pressures in the Thorax

• Intrathoracic Pressure: Pressure within the thoracic cavity.

• Intrapleural Pressure: Pressure between pleural layers; always negative relative to alveolar pressure.

• Intra-alveolar Pressure: Pressure within alveoli; changes with inspiration and expiration.

Lung Compliance and Surfactant

• Lung Compliance: Measure of lung expandability; high compliance means lungs expand easily.

• Surfactant: Reduces surface tension, preventing alveolar collapse; especially important in premature infants.

Airway Resistance

• Major Determinant: Airway diameter; resistance decreases as lung volume increases.

Lung Volumes and Capacities

Term	Definition
Inspiratory Reserve Volume (IRV)	Maximum volume inhaled after a normal inspiration
Expiratory Reserve Volume (ERV)	Maximum volume exhaled after a normal expiration
Vital Capacity (VC)	Total volume exhaled after maximal inspiration
Residual Volume (RV)	Volume remaining in lungs after maximal expiration

Internal vs. External Respiration

• External Respiration: Gas exchange between alveoli and blood.

• Internal Respiration: Gas exchange between blood and tissues.

Ventilation-Perfusion Matching

• Importance: Efficient gas exchange requires matching air flow (ventilation) and blood flow (perfusion).

• Clinical Example: Pulmonary embolism disrupts perfusion, causing mismatch.

Factors Affecting Gas Diffusion in Alveoli

• Surface area

• Thickness of alveolar-capillary membrane

• Partial pressure gradients

• Diffusion coefficient of gases

Neural Control of Ventilation

• Dorsal Respiratory Group (DRG): Controls inspiration.

• Ventral Respiratory Group (VRG): Controls expiration and forced breathing.

• Pons: Modulates rhythm and smooths transitions.

• pH Measurement: Central and peripheral chemoreceptors respond to changes in CO2 and pH.

Chemoreceptors and Lung Receptors

• Chemoreceptors: Detect changes in CO2, O2, and pH to regulate ventilation.

• Lung Receptors: Respond to stretch, irritants, and chemicals.

Cough Reflex

• Integration: Stimulus (e.g., irritant) → sensory nerves → medulla → motor response → forceful expulsion of air.

Major Respiratory Structures (Lab)

• Upper Airways: Nasal cavity, nasopharynx, oropharynx, laryngopharynx, larynx, epiglottis, glottis, thyroid cartilage, cricoid cartilage, hyoid bone

• Lower Airways: Trachea, mainstem bronchi, bronchioles, alveoli

• Lung Lobes: RUL (right upper lobe), RML (right middle lobe), RLL (right lower lobe), LUL (left upper lobe), LLL (left lower lobe)

Key Terms and Definitions (Respiratory)

Term	Definition
Asthma	Chronic airway inflammation and bronchoconstriction
COPD	Chronic obstructive pulmonary disease; includes emphysema and chronic bronchitis
Emphysema	Destruction of alveolar walls, reducing surface area for gas exchange
Pneumonia	Infection of the lung parenchyma
TB	Tuberculosis; infectious disease caused by Mycobacterium tuberculosis
Influenza	Viral infection of the respiratory tract
Lung Cancer	Malignant tumor of lung tissue

Additional Clinical and Anatomical Landmarks

• Medulla Oblongata, Pons, Midbrain: Brainstem centers for autonomic and respiratory control.

• Phrenic Nerve: Innervates the diaphragm, essential for breathing.

• Femoral Nerve, Femoral Triangle: Important for lower limb innervation and vascular access.

• Sinuses, Nasal Concha, Auditory Tube: Structures of the upper respiratory tract.

• Liver, Spleen: Abdominal organs with roles in metabolism and immunity.

• Foramen Ovale, Ligamentum Arteriosum: Fetal circulatory structures that close after birth.

Summary Table: Major Blood Vessels

Vessel	Function/Location
Aorta	Main artery from the heart to the body
Pulmonary Artery	Carries deoxygenated blood from RV to lungs
Pulmonary Vein	Returns oxygenated blood from lungs to LA
Superior/Inferior Vena Cava	Return deoxygenated blood to RA
Femoral Artery/Vein	Major vessels of the thigh
Renal Artery/Vein	Supply and drain the kidneys
Circle of Willis	Arterial circle at the base of the brain
Great Cardiac Vein	Drains blood from the heart muscle
Additional info:	See full vessel list above for more details.

Vocabulary: Selected Terms

Term	Definition
ANP	Atrial natriuretic peptide; hormone regulating blood pressure
CAD	Coronary artery disease
MI	Myocardial infarction (heart attack)
HTN	Hypertension (high blood pressure)
CVA	Cerebrovascular accident (stroke)
ECG	Electrocardiogram
EDV/ESV	End-diastolic/systolic volume
S1/S2/S3/S4	Heart sounds