Respiratory and Circulatory Systems

Systemic Arteries and Veins

The circulatory system transports blood throughout the body via arteries and veins, each serving specific regions and functions.

• Systemic arteries carry oxygenated blood from the heart to various body parts.

• Systemic veins return deoxygenated blood from the body back to the heart.

• Example: The femoral artery supplies blood to the lower limb, while the jugular vein drains blood from the head and neck.

Portal System

A portal system is a unique circulatory pathway where blood passes through two capillary beds before returning to the heart.

• Hepatic portal system: Transports blood from the digestive organs to the liver for processing.

• Significance: Allows nutrients and toxins absorbed from the gut to be metabolized before entering systemic circulation.

Vascular Resistance and Blood Flow

Blood flow through vessels is influenced by resistance, which is determined by vessel diameter, length, and blood viscosity.

• Resistance: Opposition to blood flow; higher resistance reduces flow.

• Equation: , where is flow, is pressure difference, and is resistance.

• Factors: Vasoconstriction increases resistance; vasodilation decreases resistance.

Blood Pressure Regulation

Blood pressure is regulated by neural, hormonal, and local mechanisms to ensure adequate tissue perfusion.

• Baroreceptors: Detect changes in blood pressure and initiate reflexes to maintain homeostasis.

• Renin-angiotensin system: Hormonal pathway that increases blood pressure via vasoconstriction and sodium retention.

Capillary Exchange: Filtration and Reabsorption

Capillaries allow exchange of gases, nutrients, and wastes between blood and tissues through filtration and reabsorption.

• Filtration: Movement of fluid out of capillaries due to hydrostatic pressure.

• Reabsorption: Movement of fluid into capillaries due to osmotic pressure.

• Starling's Law: Net filtration is determined by the balance of hydrostatic and osmotic pressures.

Respiratory System Anatomy

The respiratory system consists of organs and structures that facilitate gas exchange.

• Basic divisions: Upper respiratory tract (nose, pharynx, larynx) and lower respiratory tract (trachea, bronchi, lungs).

• Parts of pharynx: Nasopharynx, oropharynx, laryngopharynx.

• Structure of larynx: Contains vocal cords; connects pharynx to trachea.

• Trachea and bronchi: Conduct air to lungs; bronchi branch into bronchioles and alveoli.

• Alveoli: Site of gas exchange; surrounded by capillaries.

Mechanics of Breathing

Breathing involves inspiration and expiration, driven by changes in thoracic volume and pressure.

• Inspiration: Diaphragm contracts, thoracic cavity expands, pressure decreases, air flows in.

• Expiration: Diaphragm relaxes, thoracic cavity contracts, pressure increases, air flows out.

• Boyle's Law: ; pressure and volume are inversely related.

• Dalton's Law: Total pressure of a gas mixture equals the sum of partial pressures of individual gases.

Gas Exchange and Transport

Oxygen and carbon dioxide are exchanged in the alveoli and transported in the blood.

• Oxygen transport: Mostly bound to hemoglobin; small amount dissolved in plasma.

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

• Equation for CO2 conversion:

Respiratory Volumes and Capacities

Respiratory volumes measure the amount of air moved during breathing; capacities are combinations of volumes.

• Tidal volume (TV): Air inhaled or exhaled in a normal breath.

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

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

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

• Vital capacity (VC):

Control of Respiration

Respiratory rate and depth are regulated by neural centers and chemical signals.

• Medullary respiratory centers: Control basic rhythm of breathing.

• Chemoreceptors: Respond to changes in CO2, O2, and pH levels.

• Factors: Increased CO2 or decreased pH stimulates increased ventilation.

Functions of Cilia in Respiratory System

Cilia line the respiratory tract and help protect the lungs from inhaled particles.

• Function: Move mucus and trapped debris upward toward the pharynx for removal.

• Clinical relevance: Smoking damages cilia, increasing risk of respiratory infections.

Upper vs. Lower Respiratory Tract

The respiratory tract is divided into upper and lower regions, each with distinct functions.

• Upper respiratory tract: Nose, nasal cavity, pharynx, larynx; filters, warms, and humidifies air.

• Lower respiratory tract: Trachea, bronchi, bronchioles, alveoli; conducts air and facilitates gas exchange.

Oxygen-Hemoglobin Dissociation Curve

The oxygen-hemoglobin dissociation curve describes the relationship between oxygen partial pressure and hemoglobin saturation.

• Curve shape: Sigmoidal; reflects cooperative binding of O2 to hemoglobin.

• Factors affecting curve: pH, temperature, CO2 levels, and 2,3-BPG.

• Clinical application: Shifts in the curve affect oxygen delivery to tissues.

Baroreceptors and Chemoreceptors

Baroreceptors and chemoreceptors monitor blood pressure and chemical composition, influencing cardiovascular and respiratory responses.

• Baroreceptors: Located in carotid sinuses and aortic arch; detect changes in blood pressure.

• Chemoreceptors: Located in carotid and aortic bodies; detect changes in blood O2, CO2, and pH.

Lymphatic System

The lymphatic system returns excess tissue fluid to the bloodstream and provides immune defense.

• Lymph nodes: Filter lymph and house immune cells.

• Structure: Capsule, cortex (with follicles), medulla.

• Function: Removal of pathogens and debris from lymph.

Summary Table: Respiratory Volumes

The following table summarizes key respiratory volumes and their definitions.

Additional info: Some content was inferred and expanded for completeness and clarity, including definitions, equations, and clinical relevance.