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Key Structures of the Cardiovascular and Respiratory Systems

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Heart

Major Chambers and Valves

The heart is a muscular organ responsible for pumping blood throughout the body. It consists of four chambers and several valves that ensure unidirectional blood flow.

  • Right Atrium: Receives deoxygenated blood from the body via the superior and inferior vena cava.

  • Right Ventricle: Pumps deoxygenated blood to the lungs through the pulmonary artery.

  • Left Atrium: Receives oxygenated blood from the lungs via the pulmonary veins.

  • Left Ventricle: Pumps oxygenated blood to the body through the aorta.

  • Tricuspid Valve: Located between the right atrium and right ventricle; prevents backflow.

  • Pulmonic Valve: Between right ventricle and pulmonary artery.

  • Mitral (Bicuspid) Valve: Between left atrium and left ventricle.

  • Aortic Valve: Between left ventricle and aorta.

Internal Structures and Conduction System

  • Fossa Ovalis: Remnant of fetal foramen ovale in the interatrial septum.

  • Ligamentum Arteriosum: Remnant of fetal ductus arteriosus between pulmonary artery and aorta.

  • Trabeculae Carneae: Muscular ridges in ventricles.

  • Papillary Muscles & Chordae Tendineae: Prevent valve prolapse during contraction.

  • Myocardium: Muscular layer of the heart wall.

  • Conduction System: Includes the Sinoatrial (SA) node, Atrioventricular (AV) node, Bundle of His, bundle branches, and Purkinje fibers, which coordinate heart contractions.

Coronary Circulation

  • Coronary Arteries (Right and Left): Supply blood to the heart muscle.

  • Coronary Sinus: Collects deoxygenated blood from the myocardium.

Major Blood Vessels

Arteries

Arteries carry blood away from the heart. The aorta is the largest artery, branching into systemic arteries.

  • Aorta: Includes ascending aorta, arch, and descending aorta.

  • Brachiocephalic Trunk: First major branch of the aortic arch.

  • Carotid Arteries: Right and left common carotid arteries supply the head and neck.

  • Subclavian Arteries: Supply the upper limbs.

  • Axillary, Brachial, Radial, Ulnar: Major arteries of the upper limb.

  • Femoral, Popliteal, Tibial, Dorsalis Pedis: Major arteries of the lower limb.

  • Circle of Willis: Arterial circle at the base of the brain.

  • Coronary Arteries: Supply the heart muscle.

Veins

Veins return blood to the heart. Major veins include:

  • Superior Vena Cava (SVC): Drains blood from the upper body.

  • Inferior Vena Cava (IVC): Drains blood from the lower body.

  • Brachiocephalic Veins: Merge to form the SVC.

  • Hepatic Portal System: Transports blood from the gastrointestinal tract to the liver.

  • Great Saphenous Vein: Longest vein in the body, located in the leg.

Major Arteries and Veins Table

Artery

Region Supplied

Vein

Region Drained

Carotid

Head/Neck

Jugular

Head/Neck

Subclavian

Upper limb

Subclavian

Upper limb

Femoral

Lower limb

Femoral

Lower limb

Coronary

Heart

Coronary sinus

Heart

Hepatic

Liver

Hepatic

Liver

Respiratory System

Upper Respiratory Tract

The upper respiratory tract includes structures that conduct air into the lungs and filter, warm, and humidify it.

  • Nasal Cavity: Entryway for air; filters and humidifies.

  • Nares: External openings of the nose.

  • Pharynx: Divided into nasopharynx, oropharynx, and laryngopharynx.

  • Larynx: Contains vocal cords; passageway to the trachea.

  • Epiglottis: Flap that prevents food from entering the trachea.

  • Glottis: Opening between the vocal cords.

  • Thyroid and Cricoid Cartilage: Support the larynx.

Lower Respiratory Tract

  • Trachea: Windpipe; conducts air to the bronchi.

  • Bronchi: Primary (main), secondary (lobar), and tertiary (segmental) bronchi branch into the lungs.

  • Right and Left Lungs: Right lung has three lobes; left lung has two lobes.

  • Lobes and Fissures: Right lung: superior, middle, inferior lobes; left lung: superior, inferior lobes.

  • Hilum: Entry/exit point for bronchi, vessels, and nerves.

Microscopic Structures

  • Alveolus (plural: alveoli): Tiny air sacs where gas exchange occurs.

  • Alveolar Sac: Cluster of alveoli.

  • Terminal Bronchiole: Last part of the conducting airway.

  • Alveolar Duct: Connects respiratory bronchioles to alveolar sacs.

  • Pulmonary Capillary: Surrounds alveoli for gas exchange.

Gas Exchange Equation

Gas exchange in the alveoli is governed by partial pressure gradients:

Where: k = diffusion constant A = surface area P1 - P2 = difference in partial pressures D = thickness of the membrane

Additional info:

  • Some terms (e.g., 'Circle of Willis', 'Hepatic portal system') are included for completeness and are important for understanding systemic and special circulations.

  • Students should be able to identify these structures on diagrams and describe their functions.

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