CHAPTER 18 – CARDIOVASCULAR SYSTEM: HEART ANATOMY

Overview of Heart Anatomy

The heart is a muscular organ that functions as a dual pump, circulating blood through two distinct circuits: the pulmonary and systemic circuits. Its structure and function are essential for maintaining homeostasis and supporting cellular metabolism.

• Right side of the heart:

  • Receives de-oxygenated blood from body tissues.

  • Pumps blood to the lungs via the pulmonary circuit for oxygenation.

• Left side of the heart:

  • Receives oxygenated blood from the lungs.

  • Pumps blood to body tissues via the systemic circuit.

Chambers of the Heart

The heart contains four chambers that facilitate blood flow and separation of oxygenated and de-oxygenated blood.

• Atria (receiving chambers):

  • Right atrium

  • Left atrium

• Ventricles (pumping chambers):

  • Right ventricle

  • Left ventricle

Location and Orientation of the Heart

• Mediastinum: Central compartment of the thoracic cavity.

• Base position: Superior aspect of the heart.

• Apex position: Inferior, pointed end of the heart.

Heart Coverings

The heart is enclosed by protective membranes called the pericardium.

• Fibrous pericardium: Tough outer layer.

• Serous pericardium: Double-layered membrane (parietal and visceral pericardium).

• Homeostatic imbalances:

  • Pericarditis: Inflammation of the pericardium.

  • Cardiac tamponade: Compression of the heart due to fluid accumulation.

Layers of the Heart Wall

• Epicardium: Outer layer.

• Myocardium: Muscular middle layer responsible for contraction.

• Endocardium: Inner lining of the heart chambers.

Distinct Features of the Heart

• Coronary sulcus: Groove marking the division between atria and ventricles.

• Interventricular sulci: Grooves separating the ventricles.

• Auricles: Ear-like extensions of the atria.

• Interatrial septum: Wall separating the atria.

• Fossa ovalis/Foramen ovale: Remnant of fetal circulation.

• Trabeculae carneae: Muscular ridges in ventricles.

• Papillary muscles: Anchor the heart valves.

Major Veins Entering the Heart

• Superior vena cava

• Inferior vena cava

• Coronary sinus

Heart Valves

Valves ensure unidirectional blood flow through the heart.

• Atrioventricular (AV) valves:

  • Tricuspid (right AV valve)

  • Bicuspid/Mitral (left AV valve)

• Semi-lunar valves:

  • Pulmonary valve

  • Aortic valve

• Homeostatic imbalances:

  • Incompetent valves: Do not close properly, causing regurgitation.

Coronary Circulation

• Function: Supplies blood to the heart muscle.

• Coronary arteries and veins: Main vessels of coronary circulation.

• Homeostatic imbalances:

  • Angina pectoris: Chest pain due to reduced blood flow.

  • Myocardial infarction (heart attack): Death of heart muscle tissue.

Cardiac Muscle Fibers vs. Skeletal Muscle

• Cardiac muscle fibers are striated, branched, and interconnected by intercalated discs.

• Functional syncytium: Cells contract as a unit.

• Requires extracellular calcium for contraction.

• Longer absolute refractory period than skeletal muscle.

• Requires oxygen via aerobic respiration.

Intrinsic Conduction System

The heart's electrical system coordinates contraction.

• Pacemaker cells: Generate action potentials spontaneously.

• Sequence of excitation: SA node → AV node → Bundle of His → Bundle branches → Purkinje fibers.

• Homeostatic imbalances:

  • Arrhythmias: Irregular heart rhythms.

  • Fibrillation: Uncoordinated contraction.

  • Heart block: Impaired conduction.

• Modifications of the basic rhythm:

  • Cardiac centers in the medulla oblongata:

    • Cardioacceleratory center

    • Cardioinhibitory center

  • Autonomic nervous system innervation

• Electrocardiogram (ECG):

  • P wave: Atrial depolarization

  • QRS complex: Ventricular depolarization

  • T wave: Ventricular repolarization

  • PR interval, ST segment: Diagnostic intervals

Cardiac Cycle and Heart Sounds

• Systole: Contraction phase.

• Diastole: Relaxation phase.

• Heart sounds:

  • "Lub": Closure of AV valves.

  • "Dup": Closure of semilunar valves.

  • Heart murmurs: Abnormal sounds due to valve defects.

Regulation of Cardiac Output

• Cardiac output (CO): Volume of blood pumped per minute.

  • SV: Stroke volume; HR: Heart rate

• Regulation of stroke volume and heart rate: Influenced by autonomic nervous system, hormones, and venous return.

• Homeostatic imbalances:

  • Ion imbalances (Ca2+, K+)

  • Tachycardia: Fast heart rate

  • Bradycardia: Slow heart rate

  • Congestive heart failure: Inability to pump sufficient blood

  • Congenital heart defects

CHAPTER 19 – THE CARDIOVASCULAR SYSTEM: BLOOD VESSELS

Blood Vessel Structure

Blood vessels are classified based on structure and function. They consist of three layers (tunics):

• Tunica intima: Innermost layer, endothelium.

• Tunica media: Middle layer, smooth muscle and elastic fibers.

• Tunica externa: Outer layer, connective tissue.

Types of Arteries

• Elastic arteries: Large, close to the heart, stretch and recoil.

• Muscular arteries: Distribute blood to organs.

• Arterioles: Smallest arteries, regulate blood flow into capillaries.

Capillaries

• Structure: Thin walls for exchange.

• Function: Exchange of gases, nutrients, and wastes.

• Types:

  • Continuous: Most common, uninterrupted lining.

  • Fenestrated: Pores for increased permeability.

  • Sinusoidal: Large gaps, found in liver and spleen.

Veins and Venous Adaptations

• Structure: Thinner walls, larger lumen than arteries.

• Function: Return blood to the heart.

• Types: Veins and venules.

• Adaptations:

  • Venous valves: Prevent backflow.

  • Anastomoses: Interconnections between vessels.

• Homeostatic imbalance: Varicose veins.

Flow, Pressure, and Resistance

• Blood flow: Volume of blood moving through a vessel.

• Blood pressure: Force exerted by blood on vessel walls.

• Resistance: Opposition to flow, mainly from vessel diameter.

• Relationship:

  • F: Flow, ΔP: Pressure difference, R: Resistance

Blood Pressure Regulation

• Systolic pressure: Peak pressure during ventricular contraction.

• Diastolic pressure: Lowest pressure during relaxation.

• Pulse pressure: Difference between systolic and diastolic.

• MAP (Mean Arterial Pressure): Average pressure in arteries.

• Venous blood pressure: Lower than arterial pressure, aided by muscular and respiratory pumps.

• Regulation:

  • Short-term: Neural and hormonal controls.

  • Long-term: Renal regulation.

• Homeostatic imbalances:

  • Hypertension: High blood pressure

  • Hypotension: Low blood pressure

  • Circulatory shock: Inadequate blood flow

Capillary Exchange

• Velocity of blood flow: Slowest in capillaries for exchange.

• Colloid osmotic pressure: Pulls fluid into capillaries.

• Homeostatic imbalance: Edema.

CHAPTER 22 – RESPIRATORY SYSTEM

Functions of the Respiratory System

The respiratory system supplies oxygen for cellular respiration and removes carbon dioxide, a metabolic waste. It also aids in olfaction and speech.

• Works closely with the circulatory system for gas transport.

Four Processes of Respiration

• Pulmonary ventilation: Movement of air into and out of lungs.

• External respiration: Gas exchange between lungs and blood.

• Transport: Movement of gases in blood.

• Internal respiration: Gas exchange between blood and tissues.

Major Organs of the Respiratory System

• Upper respiratory tract:

  • Nose and nasal cavity: Filters, warms, and moistens air.

  • Paranasal sinuses: Lighten skull, produce mucus.

  • Pharynx: Passageway for air and food; three regions (nasopharynx, oropharynx, laryngopharynx).

• Lower respiratory tract:

  • Larynx: Voice production, airway protection.

  • Trachea: Windpipe, conducts air to bronchi.

  • Bronchi and branches: Conducting and respiratory zones.

  • Alveoli: Site of gas exchange; respiratory membrane.

  • Lungs and pleura: Main organs of respiration; pleura reduces friction.

Respiratory Physiology

• Pulmonary ventilation:

  • Inspiration: Diaphragm and external intercostals contract.

  • Expiration: Muscles relax; forced expiration uses accessory muscles.

• Pressure relationships:

  • Atmospheric pressure

  • Intrapulmonary pressure

  • Intrapleural pressure

  • Transpulmonary pressure

• Physical factors influencing ventilation:

  • Airway resistance

  • Alveolar surface tension

  • Lung compliance

Respiratory Volumes and Capacities

• Tidal volume (TV): Amount of air inhaled or exhaled per breath.

• Inspiratory reserve volume (IRV): Extra air inhaled after normal inspiration.

• Expiratory reserve volume (ERV): Extra air exhaled after normal expiration.

• Residual volume (RV): Air remaining after maximal exhalation.

• Capacities:

  • Inspiratory capacity (IC):

  • Functional residual capacity (FRC):

  • Vital capacity (VC):

  • Total lung capacity (TLC):

Gas Exchange and Transport

• Oxygen transport: Bound to hemoglobin; affected by temperature, pH, CO2, and BPG.

• CO2 transport: Dissolved in plasma, bound to hemoglobin, or as bicarbonate ions.

Controls of Respiration

• Neural mechanisms: Medullary and pontine respiratory centers.

• Chemical factors: CO2, O2, and pH levels.

• Higher brain centers: Voluntary control.

• Pulmonary irritants: Trigger protective reflexes.

Homeostatic Imbalances and Diseases

• Hypoxia: Inadequate oxygen delivery.

• COPD: Chronic obstructive pulmonary disease (emphysema, chronic bronchitis).

• Asthma: Reversible airway constriction.

• Tuberculosis: Infectious lung disease.

• Lung cancer: Includes adenocarcinoma, squamous cell carcinoma, small cell carcinoma.

• Sleep apnea: Intermittent cessation of breathing during sleep.

• Cystic fibrosis: Genetic disorder affecting mucus production.

Example Table: Types of Capillaries

Additional info: Academic context and definitions have been expanded for clarity and completeness. Equations are provided in LaTeX format as required.