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Cardiovascular and Respiratory Systems: Anatomy & Physiology Study Guide

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Cardiovascular System

Layers and Chambers of the Heart

The heart is a muscular organ responsible for pumping blood throughout the body. It consists of three main layers and four chambers.

  • Epicardium: The outermost layer, providing protection and containing blood vessels that nourish the heart.

  • Myocardium: The thick, muscular middle layer responsible for the heart's contractile force.

  • Endocardium: The innermost layer lining the heart chambers and valves, ensuring smooth blood flow.

  • Chambers: The heart has four chambers—right atrium, right ventricle, left atrium, left ventricle. The right side receives deoxygenated blood; the left side receives oxygenated blood.

Valves ensure unidirectional blood flow:

  • Tricuspid valve (right atrium to right ventricle)

  • Pulmonary valve (right ventricle to pulmonary artery)

  • Bicuspid/Mitral valve (left atrium to left ventricle)

  • Aortic valve (left ventricle to aorta)

Pulmonary and Systemic Circuits

The heart pumps blood through two main circuits:

  • Pulmonary Circuit: Carries deoxygenated blood from the right ventricle to the lungs for oxygenation, then returns oxygenated blood to the left atrium.

  • Systemic Circuit: Distributes oxygenated blood from the left ventricle to the body, then returns deoxygenated blood to the right atrium.

Vessels of the Pulmonary Circuit include pulmonary arteries and veins. Vessels of the Systemic Circuit include the aorta, arteries, veins, and vena cava.

Blood Vessels: Structure and Types

Blood vessels transport blood throughout the body and are classified by structure and function.

  • Arteries: Carry blood away from the heart; have thick muscular walls.

  • Veins: Carry blood toward the heart; have thinner walls and valves to prevent backflow.

  • Capillaries: Microscopic vessels for exchange of gases, nutrients, and waste.

Layers of Arteries and Veins:

  • Tunica externa (outer layer)

  • Tunica media (middle, muscular layer)

  • Tunica intima (inner endothelial layer)

Types of Capillaries:

Type

Structure

Function

Continuous

Uninterrupted lining

Least permeable, found in muscle, skin, brain

Fenestrated

Pores in endothelium

More permeable, found in kidneys, intestines

Sinusoidal

Large gaps

Most permeable, found in liver, spleen

Coronary Circulation

The heart muscle (myocardium) receives blood via coronary arteries.

  • Right Main Coronary Artery

  • Left Main Coronary Artery

  • Left Anterior Descending (LAD)

  • Left Circumflex

Each artery supplies specific regions of the myocardium.

Cardiac Conduction System

The heart's electrical system coordinates contraction.

  • SA Node: Pacemaker, initiates heartbeat

  • AV Node: Delays impulse, allows atria to contract

  • Bundle of His: Transmits impulse to ventricles

  • Right/Left Bundle Branches: Conduct impulses through ventricles

  • Purkinje Fibers: Distribute impulse to ventricular muscle

EKG Components:

  • P wave: Atrial depolarization

  • QRS complex: Ventricular depolarization

  • T wave: Ventricular repolarization

Cardiac Cycle and Heart Sounds

The cardiac cycle includes systole (contraction) and diastole (relaxation).

  • S1: First heart sound, closure of AV valves

  • S2: Second heart sound, closure of semilunar valves

Cardiac Output:

  • Formula:

  • SV: Stroke Volume, HR: Heart Rate

Ejection Fraction: Percentage of blood ejected from the ventricle per beat.

Blood Pressure and Perfusion

Blood pressure is the force exerted by blood on vessel walls.

  • Pulse Pressure:

  • Mean Arterial Pressure (MAP): or

MAP is crucial for organ perfusion.

Regulation of Heart Rate and Blood Pressure

Cardiac centers in the brain regulate heart rate:

  • Cardioacceleratory center: Increases HR

  • Cardioinhibitory center: Decreases HR

Vasomotor center regulates vessel diameter and blood pressure.

Types of Shock

Shock is a state of inadequate tissue perfusion.

Type

Description

Cardiogenic

Heart fails to pump effectively

Obstructive

Physical obstruction to blood flow

Hypovolemic

Loss of blood volume

Distributive

Abnormal distribution of blood (includes anaphylactic, septic, neurogenic)

Respiratory System

Structures of the Upper and Lower Airway

The respiratory system consists of conducting and respiratory zones.

  • Upper Airway: Pharynx (nasopharynx, oropharynx, laryngopharynx), soft palate, uvula, nose, nasal mucosa, epiglottis

  • Larynx: Glottis, thyroid cartilage, vestibular folds, vocal cords

  • Trachea: Cricoid cartilage, carina

  • Bronchi: Mainstem, lobar, segmental, terminal, respiratory bronchioles

  • Alveoli: Site of gas exchange

Lungs: Right lung (3 lobes), left lung (2 lobes)

Pleura and Pleural Cavity

The lungs are covered by pleural membranes:

  • Parietal pleura: Outer membrane

  • Visceral pleura: Inner membrane

  • Pleural cavity: Space between pleural membranes

Negative pressure in the pleural space keeps lungs inflated.

Phases of Ventilation

Ventilation consists of inspiration and expiration.

  • Inspiration: Diaphragm contracts, thoracic volume increases, air flows in

  • Expiration: Diaphragm relaxes, thoracic volume decreases, air flows out

Respiratory pressures:

  • Atmospheric pressure (ATM): Pressure of air outside the body

  • Intrapleural pressure: Pressure within pleural cavity

  • Intrapulmonary pressure: Pressure within alveoli

Positive pressure: Greater than 760 mmHg; Negative pressure: Less than atmospheric

Respiratory Volumes and Capacities

  • Tidal Volume (TV): Air moved per breath

  • Vital Capacity (VC): Maximum air exhaled after maximum inhalation

  • Functional Residual Capacity (FRC): Air remaining after normal exhalation

Gas Exchange and Transport

Gas exchange occurs in alveoli via diffusion.

  • Dalton's Law: Total pressure is sum of partial pressures

  • Henry's Law: Gas solubility in liquid is proportional to partial pressure

Oxygen Transport: Most oxygen is carried by hemoglobin.

  • Oxyhemoglobin Dissociation Curve: Shows relationship between oxygen saturation and partial pressure

  • Right shift: Decreased affinity (increased temperature, CO2, H+)

  • Left shift: Increased affinity (decreased temperature, CO2, H+)

Carbon Dioxide Transport: CO2 is carried dissolved, as bicarbonate, and bound to hemoglobin.

Control of Respiration

Respiratory centers in the brainstem regulate breathing rate and depth.

  • Phrenic nerve: Innervates diaphragm

  • Intercostal nerves: Innervate intercostal muscles

Pathophysiology and Clinical Correlates

  • Atelectasis: Collapse of alveoli

  • Pneumothorax: Air in pleural cavity

  • Hemothorax: Blood in pleural cavity

  • Tension pneumothorax: Progressive build-up of air causing mediastinal shift

Common Respiratory Diseases:

  • Chronic Obstructive Pulmonary Disease (COPD)

  • Asthma

  • Lung cancer (e.g., squamous cell carcinoma)

Additional info:

  • Some content inferred for completeness, such as the function of cardiac conduction system, details of gas exchange, and clinical correlates.

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