Cardiovascular and Respiratory Systems: Anatomy & Physiology Study Guide

Cardiovascular System

Layers of the Heart

The heart wall consists of three distinct layers, each with specific functions:

• 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.

Heart Chambers and Valves

The heart contains four chambers and four main valves that regulate blood flow:

• Chambers: Right atrium, right ventricle, left atrium, left ventricle.

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

Blood flows through the chambers in a specific sequence, ensuring oxygenation and circulation throughout the body.

Pulmonary and Systemic Circuits

The heart supports two major circulatory pathways:

• Pulmonary Circuit: Carries deoxygenated blood from the right ventricle to the lungs and returns oxygenated blood to the left atrium.

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

Each circuit has distinct vessels and functions, supporting gas exchange and nutrient delivery.

Blood Vessels: Structure and Function

Blood vessels are classified by structure and function:

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

• Veins: Return blood to 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 connective tissue layer.

• Tunica media: Middle smooth muscle layer.

• Tunica interna: Inner endothelial lining.

Types of Capillaries

Type	Structure	Function
Continuous	Uninterrupted lining	Most common; allows selective exchange
Fenestrated	Pores in endothelium	Found in kidneys, intestines; allows rapid exchange
Sinusoidal	Large gaps	Found in liver, spleen; allows passage of large molecules

Coronary Circulation

The heart receives its own blood supply via the coronary arteries:

• Right Main Coronary Artery

• Left Main Coronary Artery

• Left Anterior Descending (LAD)

• Left Circumflex

These arteries supply oxygen and nutrients to the myocardium.

Cardiac Myocyte Structure

Cardiac muscle cells (myocytes) have specialized regions:

• Cell membrane

• Sarcoplasmic reticulum

• T-tubule

• Sarcomere: Contains contractile proteins myosin and actin.

• Z-discs: Define boundaries of sarcomeres.

Regulatory proteins include troponin and tropomyosin.

Cardiac Conduction System

The heart's electrical system coordinates contraction:

• SA Node: Pacemaker, initiates impulse.

• AV Node: Delays impulse.

• Bundle of His, Bundle Branches, Purkinje fibers: Distribute impulse through ventricles.

EKG (electrocardiogram) records electrical activity:

• 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):

• Atrial Systole: Atria contract, pushing blood into ventricles.

• Ventricular Systole: Ventricles contract, ejecting blood.

• Atrial Diastole: Atria relax and fill with blood.

• Ventricular Diastole: Ventricles relax and fill.

Heart sounds:

• S1: Closure of AV valves ("lub")

• S2: Closure of semilunar valves ("dub")

Cardiac Output and Ejection Fraction

Cardiac output is the volume of blood pumped per minute:

• Formula: $CO = SV \times HR$

• SV: Stroke volume

• HR: Heart rate

Ejection fraction measures the percentage of blood ejected from the ventricle per beat.

Blood Pressure and Perfusion

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

• Systolic: Pressure during ventricular contraction

• Diastolic: Pressure during ventricular relaxation

Mean Arterial Pressure (MAP) is a key indicator of tissue perfusion:

• Formula: $MAP = DBP + \frac{1}{3} (SBP - DBP)$

• Or $MAP = \frac{SBP + 2 \times DBP}{3}$

Vascular Resistance and Regulation

Blood flow is affected by vessel diameter, length, and viscosity:

• Vasoconstriction: Narrowing of vessels increases resistance and blood pressure.

• Vasodilation: Widening of vessels decreases resistance and blood pressure.

Pulse pressure is the difference between systolic and diastolic pressures:

• Formula: $Pulse\ Pressure = SBP - DBP$

Shock and Perfusion

Shock is a state of inadequate tissue perfusion. Types include:

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

Upper Airway Anatomy

The upper airway includes:

• Pharynx: Nasopharynx, oropharynx, laryngopharynx

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

• Trachea: Cricoid cartilage, carina

These structures conduct air and protect the lower airway.

Lung Anatomy and Lobes

The lungs are divided into lobes:

• Right lung: 3 lobes

• Left lung: 2 lobes

Bronchi branch into bronchioles, ending in alveoli where gas exchange occurs.

Pleura and Pleural Cavity

The lungs are covered by two pleural membranes:

• Parietal pleura: Outer membrane

• Visceral pleura: Inner membrane

• Pleural cavity: Space between membranes, contains lubricating fluid

Ventilation and Pressure

Ventilation involves inspiration and expiration, driven by pressure changes:

• Negative pressure: Pressure below atmospheric, draws air in

• Positive pressure: Pressure above atmospheric, pushes air out

• Intrapleural pressure: Pressure within pleural cavity

• Intrapulmonary pressure: Pressure within alveoli

When intrapleural pressure exceeds intrapulmonary pressure, lung collapse (atelectasis) can occur.

Respiratory Volumes and Capacities

Key volumes:

• 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 is transported bound to hemoglobin; carbon dioxide is transported dissolved, as bicarbonate, or bound to hemoglobin.

Transport Form	Oxygen	Carbon Dioxide
Dissolved	Small amount	7-10%
Bound to Hemoglobin	98%	20-23%
Bicarbonate	N/A	70%

Oxyhemoglobin dissociation curve shows the relationship between oxygen saturation and partial pressure of oxygen.

Control of Respiration

Respiratory centers in the brainstem regulate breathing rate and depth:

• Medullary respiratory center

• Pontine respiratory center

Chemoreceptors respond to changes in CO2, O2, and pH.

Pathophysiology

Common respiratory and cardiovascular pathologies include:

• Pneumothorax: Air in pleural space

• Hemothorax: Blood in pleural space

• Shock: Inadequate perfusion

• Heart failure: Inability of heart to pump effectively

• Chronic Obstructive Pulmonary Disease (COPD): Chronic airflow limitation

• Lung cancer: Squamous cell carcinoma, small cell carcinoma, adenocarcinoma

Fetal Circulatory Adaptations

Structure	Function
Ductus Venosus	Shunts blood from umbilical vein to inferior vena cava
Foramen Ovale	Allows blood flow between right and left atria
Ductus Arteriosus	Connects pulmonary artery to aorta

Additional info:

• Some content inferred for completeness, such as definitions and examples of pathologies.

• Tables reconstructed for clarity and comparison.