AG

Respiratory System

Respiratory System Overview

  • The respiratory system includes:

    • Nose

    • Nasal cavity

    • Pharynx

    • Larynx

    • Trachea

    • Bronchi

    • Smaller passageways

    • Alveoli (sites of gaseous exchange)

  • Divided into:

    • Upper Respiratory Tract

    • Lower Respiratory Tract

  • Functions:

    • External Respiration ❖ exchange of gases with the environment.

    • Internal Respiration ❖ exchange of gases at the cellular level.

Functions of the Respiratory System

  • In addition to gas exchange, the respiratory system serves various functions:

    • Phonation: Production of sounds via air movement across vocal folds.

    • Olfaction: The sense of smell through inhalation of gaseous materials which are then dissolved in the nasal cavity's mucous layer.

    • Heat Regulation: Regulates body temperature through panting.

    • Acid-Base Regulation: Helps maintain pH balance in the body.

Anatomy of the Canine Respiratory System

  • Dog Respiratory Tract Components:

    • Caudal Lung Lobe

    • Larynx: Voice box and air passageway, supported by hyroid bone.

    • Trachea: Extends from larynx to lungs, bifurcating into bronchi.

    • Lung Lobes: Cranial, Middle, and Caudal Lobe.

Tracheal Anatomy

  • The Trachea: Known as the wind pipe, connects larynx to bronchi:

    • Bifurcation: Splits into left and right bronchi.

    • Carina: The ridge where bifurcation occurs.

  • Variations Across Species:

    • In horses, tracheal rings are incomplete dorsally.

    • In ruminants, ends of tracheal rings create a dorsal ridge.

    • In dogs, tracheal rings are U-shaped and membranous posteriorly.

Respiratory System Components

  • Nasal Anatomy:

    • External Nose: Comprising the rostral part of the face.

    • Nostrils (Nares): External openings for air intake.

    • Bony Nasal Aperture: Movable parts supported by nasal cartilages.

    • Philtrum: Groove between the nostrils.

Vomeronasal Organ

  • Jacobson’s Organ:

    • Located at the base of the nasal septum.

    • Involved in olfactory functions and detection of pheromones, affecting social and sexual behavior.

    • Associated with Flehmen Response.

Nasal Cavity Structure

  • Components:

    • Median Nasal Septum: Divides the nasal cavity.

    • Three Main Parts: Vestibule, Nasal Conchae, and Ethmoturbinates.

    • Presence of Turbinates (Nasal Conchae): Increases surface area for air processing.

    • Distinction between Nasal Meatus vs Conchae.

  • Paranasal Sinuses: Air-filled spaces that enhance the function of the nasal cavity.

Other Nasal Functions

  • Nasolacrimal Duct: Channels tears from the eyes to the nasal cavity.

  • The anterior nose is supported by cartilages which assist in respiration and heat regulation.

  • Lateral Nasal Glands: Supplies moisture for temperature control during panting.

Pharyngeal Anatomy

  • Nasopharynx: Common passageway for respiratory and digestive systems.

    • Contains Auditory Tube (Eustachian tube) connects the middle ear to the nasopharynx.

Trachea and its Functionality

  • Trachea: Continuous air passage to lungs, divided into left and right bronchi at bifurcation.

    • Reinforced by tracheal rings for structural support while allowing flexibility.