Anatomy & Physiology Study Guide: Respiratory, Cardiovascular, and Lymphatic Systems

Respiratory System

Overview of the Respiratory System

The respiratory system is responsible for the exchange of gases (oxygen and carbon dioxide) between the body and the environment. It consists of upper and lower respiratory tracts, specialized structures for air conduction, filtration, and gas exchange.

• Upper Respiratory Tract: Includes the nasal cavity, pharynx, and larynx.

• Lower Respiratory Tract: Includes the trachea, bronchi, bronchioles, and alveoli.

• Function: Conducts air, filters particles, humidifies, and warms incoming air.

Structures and Functions

• Nasal Cavity: Warms, humidifies, and filters air; contains olfactory receptors for smell.

• Pharynx: Shared passageway for air and food; divided into nasopharynx, oropharynx, and laryngopharynx.

• Larynx: Contains vocal cords; functions in sound production and airway protection.

• Trachea: Windpipe; supported by C-shaped cartilage rings to prevent collapse.

• Bronchi and Bronchioles: Conduct air to alveoli; bronchioles control airflow via smooth muscle.

• Alveoli: Site of gas exchange; lined by simple squamous epithelium (Type I cells) and surfactant-producing Type II cells.

Gas Exchange and Transport

Gas exchange occurs in the alveoli by diffusion across the respiratory membrane. Oxygen is transported primarily bound to hemoglobin in red blood cells, while carbon dioxide is carried dissolved in plasma, as bicarbonate, or bound to hemoglobin.

• Boyle's Law: Pressure and volume of a gas are inversely related in a closed system. $P_1V_1 = P_2V_2$

• Partial Pressure: The pressure exerted by each gas in a mixture; total pressure is the sum of partial pressures (Dalton's Law).

• Surfactant: Reduces surface tension in alveoli, preventing collapse.

Respiratory Volumes and Capacities

• Tidal Volume (TV): Amount of air moved in or out during normal breathing.

• Vital Capacity (VC): Maximum amount of air exhaled after maximal inhalation.

• Residual Volume (RV): Air remaining in lungs after maximal exhalation.

• Inspiratory/Expiratory Reserve Volume (IRV/ERV): Additional air inhaled/exhaled beyond normal breathing.

Control of Breathing

• Medulla Oblongata: Primary respiratory control center in the brainstem.

• Diaphragm: Main muscle of inspiration; contracts to increase thoracic volume.

• Accessory Muscles: Sternocleidomastoid, scalenes (active during forced breathing).

Clinical Considerations

• Hypoxia: Low oxygen in tissues.

• Hypercapnia: Elevated carbon dioxide in blood.

• Apnea: Temporary cessation of breathing.

• Bronchodilation/Bronchoconstriction: Regulation of airway diameter by smooth muscle.

Cardiovascular Conducting System & Vessels

Overview of the Cardiovascular System

The cardiovascular system transports blood, nutrients, gases, and wastes throughout the body. It consists of the heart, blood vessels, and the conducting system that regulates heart rhythm.

• Heart: Muscular organ with four chambers (atria and ventricles).

• Blood Vessels: Arteries, veins, and capillaries.

• Conducting System: Specialized cardiac tissue that generates and propagates electrical impulses.

Cardiac Conducting System

• Sinoatrial (SA) Node: Pacemaker of the heart; initiates action potentials (typically 60-100 per minute).

• Atrioventricular (AV) Node: Delays impulse to allow atrial contraction before ventricular contraction.

• Bundle of His (AV Bundle): Conducts impulses from AV node to ventricles.

• Purkinje Fibers: Distribute electrical impulses throughout ventricular myocardium.

Electrocardiogram (ECG) Interpretation

• P wave: Atrial depolarization.

• QRS complex: Ventricular depolarization.

• T wave: Ventricular repolarization.

• PR interval: Time between onset of atrial and ventricular depolarization; prolonged PR indicates conduction delay.

Blood Vessel Structure and Function

• Arteries: Thick walls, high pressure, carry blood away from heart.

• Veins: Thinner walls, lower pressure, carry blood toward heart; contain valves to prevent backflow.

• Capillaries: Thin walls (single layer of endothelium) for exchange of gases and nutrients.

• Layers of Vessel Walls:

  • Tunica intima: Innermost layer, endothelium.

  • Tunica media: Middle layer, smooth muscle (vasoconstriction/vasodilation).

  • Tunica externa: Outer layer, connective tissue.

Clinical Considerations

• Arrhythmias: Abnormal heart rhythms; SA node dysfunction may lead to slower heart rates.

• Ventricular Septal Defect (VSD): Opening between ventricles causing abnormal blood flow.

Lymphatic System & Immunity

Overview of the Lymphatic System

The lymphatic system returns excess tissue fluid to the bloodstream, absorbs dietary fats, and is integral to immune defense. It consists of lymph, lymphatic vessels, lymph nodes, and lymphoid organs.

• Lymph: Fluid containing white blood cells, proteins, and fats.

• Lymphatic Vessels: Transport lymph; contain valves to prevent backflow.

• Lymph Nodes: Filter lymph and house immune cells.

• Lymphoid Organs: Spleen, thymus, tonsils.

Immune System Function

• Lymphocytes: White blood cells (B cells and T cells) involved in adaptive immunity.

• Antibodies: Proteins produced by B cells to neutralize pathogens.

• Phagocytes: Cells that engulf and destroy pathogens (e.g., macrophages).

Clinical Considerations

• Anoxia: Absence of oxygen supply to tissues.

• Edema: Swelling due to accumulation of lymph or tissue fluid.

• Immunodeficiency: Impaired immune response.

Key Table: Comparison of Blood Vessel Types

Vessel Type	Wall Thickness	Valves Present	Function
Arteries	Thick	No	Carry blood away from heart
Veins	Thin	Yes	Carry blood toward heart
Capillaries	Very thin (single cell layer)	No	Exchange of gases and nutrients

Key Table: Respiratory Volumes

Volume/Capacity	Description
Tidal Volume (TV)	Air moved in/out during normal breathing
Vital Capacity (VC)	Max air exhaled after maximal inhalation
Residual Volume (RV)	Air remaining after maximal exhalation
Inspiratory Reserve Volume (IRV)	Extra air inhaled beyond normal inspiration
Expiratory Reserve Volume (ERV)	Extra air exhaled beyond normal expiration

Additional info:

• Boyle's Law and Dalton's Law are fundamental to understanding respiratory mechanics and gas exchange.

• Surfactant is produced by Type II alveolar cells and is essential for reducing alveolar surface tension.

• Valves in veins and lymphatic vessels prevent backflow and ensure unidirectional flow.