Biology 231: Respiratory System

• Biology 231, Chapter 22 covers the respiratory system.
• The chapter is divided into five parts: an overview, the respiratory tract, gas exchange, control of air flows and lung volumes, and an overview of respiratory problems.
• The respiratory system functions include ventilation, gas exchange, circulation, and cellular respiration.

Unidirectional vs. Bidirectional Flow

• The flow of blood through the human cardiovascular system is unidirectional.
• The flow of air through the human respiratory system is bidirectional.

Overview of the Respiratory Tract

• Two basic distinctions exist: the upper versus lower respiratory system and the respiratory zone versus the conducting zone.

Part 2: Respiratory Tract

• The pharynx serves multiple organ systems.
• The transition from the upper to the lower respiratory system involves two parallel tubes, and one should not accept food.

Larynx

• The larynx is located at approximately C₄ superiorly and C₆ or C₇ inferiorly.
• Structures to identify include the epiglottis, hyoid bone, thyroid cartilage, arytenoid cartilage, vestibular ligament (inside vestibular folds), and vocal ligament (inside vocal folds).

Vocal Cords and Speaking/Singing Pitch

• Two factors determine the pitch of a string on a musical instrument.
• Vocal cord tension can be adjusted to speak or sing with a different pitch.

Trachea

• The trachea has cartilaginous rings for support.
• The cartilaginous rings are incomplete on the posterior side.
• At its inferior end, the trachea branches into two.

Bronchi and Bronchioles

• There is a difference between the primary and secondary (lobar) bronchi.
• The walls of bronchi and bronchioles differ, with bronchioles being more affected by the autonomic nervous system.

Left Lung vs. Right Lung

• The two lungs are not exactly symmetrical.

Lateral and Medial Views of the Lung

• The lungs have both lateral and medial views with different features.

Part 3: Gas Exchange

• Gas exchange occurs at the alveoli.
• The conducting zone transitions into the respiratory zone at a specific point.
• Blood flows in one direction with respect to oxygenation.
• Oxygen and carbon dioxide diffuse independently of each other.

Quantification of Diffusion

• Fick's Law of Diffusion explains gas exchange rates in the lungs.

Respiratory System Classification

• Respiratory structures can be classified as part of the upper or lower respiratory system and/or the conducting zone or the respiratory zone.

Cardiorespiratory System Concentrations

• Concentrations of oxygen and carbon dioxide vary in different locations within the cardiorespiratory system.

Pulmonary Anatomy

• Fick's law of diffusion can predict how changes in pulmonary anatomy affect the diffusion rate.

Part 4: Respiratory Muscles

• Respiratory muscles control air flows and lung volumes.

Thoracic Cavity Volume

• Changes in thoracic cavity volume affect lung volume.
• The diaphragm contracts during a specific process (inspiration or expiration).

Graphing Lung Volume

• Lung volume can be graphed to indicate air flow.
• Technical terms exist for normal quiet breathing and extra/vigorous/forced breathing.
• Forced breathing may involve contracting the same muscles harder.

Muscles and Ventilation

• Different muscles are active during inspiration and expiration.

Accessory Muscles

• Accessory muscles have insertions in common.
• Inspiratory and expiratory muscles act on these insertions.

Respiratory Muscle Actions

• Accessory respiratory muscles have origins, insertions, and actions related to breathing.

Lung Muscle Activity

• Specific respiratory muscles are active during different phases.
• The primary inspiratory muscles may or may not be active at certain times.

Signals for Contraction

• Signals to contract respiratory muscles come from somewhere.

Inspiratory vs. Expiratory Muscles

• The effect of a muscle on thoracic cage or lung volume determines if it's inspiratory or expiratory.

Muscle Contraction

• Origin and insertion can determine whether a muscle contracts during inspiration or expiration.

Respiratory Cycle and Composition

• Given information about a specific part of the respiratory cycle, one can predict air composition and/or direction of flow.

Part 5: Overview of Respiratory Problems

• Respiratory problems can be categorized.

V/Q Mismatch

• The variables V and Q have specific meanings in the context of respiratory problems.
• Blood in the pulmonary veins differs in V/Q mismatch.

Respiratory Problem Determination

• The characteristics of a respiratory problem can determine whether it is a restrictive lung disorder, an obstructive lung disorder, and/or V/Q mismatching.