Detailed Notes on the Respiratory System PT 1

Major Functions of the Respiratory System

• Respiration:

  • Supplies the body with O_2 for cellular respiration.

  • Disposes of CO_2, a waste product of cellular respiration.

• Additional Functions:

  • Olfaction (sense of smell).

  • Speech production.

  • Acts as a physiological buffer to help maintain pH homeostasis.

Anatomy of the Respiratory System

Main Structures

• Upper Respiratory System:

  • Nasal cavity.

  • Oral cavity.

  • Pharynx.

  • Larynx.

• Lower Respiratory System:

  • Trachea.

  • Bronchi and bronchioles.

  • Lungs and alveoli.

Major Organs

• Nose, nasal cavity, paranasal sinuses.

• Pharynx:

  • Connects nasal cavity and mouth to larynx and esophagus; composed of skeletal muscle.

  • Divided into three regions:

  • Nasopharynx.

  • Oropharynx.

  • Laryngopharynx.

• Larynx:

  • Connects to hyoid bone; continuous with trachea.

  • Functions:

  • Provides a patent airway.

  • Routes air and food into proper channels.

  • Voice production (houses vocal folds).

Specific Components and Functions

Larynx Details

• Composed of hyaline cartilage except for the epiglottis (elastic cartilage).

• Epiglottis covers glottis during swallowing, preventing food from entering the airway.

• The Adam's apple is a prominent cartilage in males, thickened after puberty.

Trachea

• Known as the "windpipe" connecting larynx to mediastinum.

• Lined with pseudostratified ciliated columnar epithelium with goblet cells to trap particles.

• Features C-shaped cartilage rings for structural support, allowing flexibility and preventing collapse.

Conducting Zone Structures

• Includes bronchi, bronchioles, and their branches.

• Changes Occurring:

  • Cartilage rings become irregular plates in bronchioles.

  • Epithelium transitions from pseudostratified columnar to cuboidal.

  • Increased smooth muscle relative to cartilage, facilitating bronchiole constriction (significant in asthma).

Respiratory Zone

• Composed of alveoli (~300 million).

• Functions as the site of gas exchange, featuring:

  • Simple squamous epithelium for efficient diffusion.

  • Surfactant-secreting cells to decrease surface tension and keep alveoli open.

Gas Exchange Mechanism

• External Respiration: Gas exchange at lungs (Oxygen from alveoli to blood, Carbon Dioxide from blood to alveoli).

• Internal Respiration: Gas exchange at tissues (Oxygen from blood to cells, Carbon Dioxide from cells to blood).

• Gas exchange relies on diffusion through simple squamous epithelium.

Breathing Mechanics

• Pulmonary Ventilation: Two phases - Inspiration and Expiration.

• Inhalation (Active Process):

  • Diaphragm contracts, increasing lung volume, leading to decreased intrapulmonary pressure.

  • Air flows into lungs until pressure equilibrium is reached.

• Exhalation (Passive Process):

  • Elastic recoil of lungs decreases volume, increasing intrapulmonary pressure.

  • Air expels from lungs until pressure equilibrium is restored.

Lung Volumes

• Tidal Volume (TV): Volume of air in normal breathing.

• Inspiratory Reserve Volume (IRV): Air forcibly inhaled above tidal volume.

• Expiratory Reserve Volume (ERV): Air forcibly exhaled beyond tidal volume.

• Vital Capacity (VC): VC = IRV + TV + ERV.

• Residual Volume (RV): Air left in lungs post-exhalation.

• Total Lung Capacity (TLC): TLC = VC + RV ext{ (approximately 6 liters for fit individuals)}.

Summary of Nonrespiratory Air Movements

• These include reflex actions or voluntary actions like:

  • Coughing: clears lower respiratory system.

  • Sneezing: clears upper respiratory system.

  • Hiccups, crying, laughing, yawning: might modify normal breathing rhythm.

Additional Notes

• The pleural cavity creates surface tension, promoting lung inflation.

• Pneumothorax results from air in pleural space, leading to lung collapse.

• Pulmonary circulation crucial for oxygenation:

  • Pulmonary arteries deliver deoxygenated blood to lungs.

  • Pulmonary veins return oxygenated blood to the heart for systemic circulation.

Major Functions of the Respiratory System

• Respiration:

  • Supplies the body with O_2 for cellular respiration, which is a critical process for energy production in cells.

  • Disposes of CO_2, a waste product of cellular respiration, maintaining acid-base balance in the body.

• Additional Functions:

  • Olfaction: The sense of smell is enabled by olfactory receptors located in the nasal cavity that detect airborne chemicals.

  • Speech production: The respiratory system supports the production of sound through voice and modulation by exhalation of air over the vocal folds contained within the larynx.

  • Acts as a physiological buffer to help maintain pH homeostasis: The respiratory system regulates blood pH by controlling carbon dioxide levels; an increase in CO_2 results in increased carbonic acid and a decrease in blood pH.

Anatomy of the Respiratory System

Main Structures

• Upper Respiratory System:

  • Nasal cavity: Warms, moistens, and filters incoming air, housing olfactory receptors.

  • Oral cavity: Acts as an alternative air passage, especially during heavy breathing.

  • Pharynx: A muscular wall that connects the nasal cavity and mouth to the larynx and esophagus.

  • Larynx: Contains the vocal cords and protects the airway during swallowing.

• Lower Respiratory System:

  • Trachea: A tubular structure that directs air to the bronchi.

  • Bronchi and bronchioles: Branching tubes through which air is conducted to the lungs.

  • Lungs and alveoli: Major sites of gas exchange consisting of millions of tiny air sacs.

Major Organs

• Nose, nasal cavity, paranasal sinuses: These structures help in filtering, warming, and humidifying the air.

• Pharynx:

  • Connects the nasal cavity and mouth to the larynx and esophagus; composed of skeletal muscle to facilitate swallowing.

  • Divided into three regions:

  • Nasopharynx: Located above the soft palate, serves as a passageway for air.

  • Oropharynx: The middle portion that serves as a passage for both air and food.

  • Laryngopharynx: The lower part that opens into the larynx and esophagus.

• Larynx:

  • Connects to the hyoid bone and is continuous with the trachea.

  • Functions:

  • Provides a patent (open) airway.

  • Routes air and food into proper channels, directing air solely into the trachea during breathing and food to the esophagus during swallowing.

  • Voice production: Houses vocal folds, which vibrate to produce sound.

Specific Components and Functions

Larynx Details

• Composed primarily of hyaline cartilage except for the epiglottis, which is made of elastic cartilage, allowing it to be flexible during swallowing.

• The epiglottis functions as a flap, covering the glottis during swallowing to prevent food from entering the airway and directing it to the esophagus.

• The Adam's apple, or laryngeal prominence, is a notable cartilage in males, typically becoming more pronounced after puberty due to hormonal changes.

Trachea

• Known as the "windpipe," it connects the larynx to the mediastinum and branches into the bronchi.

• Lined with pseudostratified ciliated columnar epithelium with goblet cells that produce mucus, trapping particulate matter and pathogens.

• Features C-shaped cartilage rings which provide structural support; they are open at the back, allowing the trachea to flex and expand during breathing.

Conducting Zone Structures

• Comprises the bronchi, bronchioles, and their branches, facilitating air conduction.

• Changes Occurring:

  • The cartilage rings become irregular plates in smaller bronchi and bronchioles, allowing greater flexibility.

  • The epithelium transitions from pseudostratified columnar in the larger airways to cuboidal in the smaller branches, as the respiratory passage becomes more involved in gas exchange.

  • There is an increase in smooth muscle relative to cartilage, which allows for the constriction and dilation of bronchioles; this is particularly significant in conditions like asthma.

Respiratory Zone

• Composed of alveoli (approximately 300 million), these tiny sacs are the primary sites for gas exchange.

• Features simple squamous epithelium, optimized for efficient gas diffusion.

• Contains surfactant-secreting cells (type II alveolar cells) that reduce surface tension, helping prevent alveolar collapse and enhancing lung compliance.

Gas Exchange Mechanism

• External Respiration: Occurs at the lungs, involving gas exchange where oxygen passes from the alveoli into the blood, and carbon dioxide moves from the blood into the alveoli for exhalation.

• Internal Respiration: Takes place at the tissue level, with oxygen diffusing from the blood into body cells, while carbon dioxide produced by cells diffuses back into the bloodstream for removal.

• Gas exchange relies on diffusion through the simple squamous epithelium of the alveoli, driven by concentration gradients.

Breathing Mechanics

• Pulmonary Ventilation: Involves two phases—Inspiration and Expiration.

• Inhalation (Active Process):

  • The diaphragm contracts and moves downward, increasing thoracic cavity volume and subsequently decreasing intrapulmonary pressure, allowing external air to flow in until the pressure inside the lungs equals atmospheric pressure.

• Exhalation (Passive Process):

  • The elastic recoil of the lung tissue decreases its volume, thereby increasing intrapulmonary pressure.

  • Air is expelled from the lungs until equilibrium in pressure is restored.

Lung Volumes

• Tidal Volume (TV): The volume of air inhaled or exhaled during normal breathing; typically around 500 mL in a healthy adult.

• Inspiratory Reserve Volume (IRV): The additional air that can be inhaled after a normal inhalation, averaging about 3000 mL.

• Expiratory Reserve Volume (ERV): The extra air that can be forcefully exhaled after the end of a normal expiration, approximately 1200 mL.

• Vital Capacity (VC): The maximal volume of air that can be exhaled after maximal inhalation, calculated as VC = IRV + TV + ERV.

• Residual Volume (RV): The volume of air that remains in the lungs after maximal exhalation, around 1200 mL, preventing lung collapse.

• Total Lung Capacity (TLC): The total volume of air the lungs can hold, calculated as TLC = VC + RV (approximately 6 liters for fit individuals).

Summary of Nonrespiratory Air Movements

• Include reflex activities or voluntary actions such as:

  • Coughing: A mechanism to clear the lower respiratory passages of irritants or mucus.

  • Sneezing: An action to expel irritants from the nasal cavity.

  • Hiccups: Involuntary contractions of the diaphragm causing sharp intakes of breath.

  • Crying, laughing, yawning: Each can modify normal breathing patterns and play roles in emotional expression or signaling.

Additional Notes

• The pleural cavity, filled with pleural fluid, creates surface tension that facilitates lung inflation by adhering to the thoracic wall, allowing the lungs to expand during inhalation.

• Pneumothorax is a medical condition resulting from air entering the pleural space, which can lead to lung collapse, often requiring medical intervention.

• Pulmonary circulation is crucial for oxygenation of blood:

  • Pulmonary arteries transport deoxygenated blood from the heart to the lungs for oxygenation.

  • Pulmonary veins return oxygenated blood from the lungs back to the heart to be pumped into systemic circulation.