Respiratory Tract
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Questions and Answers

List the several functions of the respiratory system. (Hint : 8)

Acid/base regulation, phonation, olfaction, hormonal conversion, heat regulation, protection, air conduction/gas exchange, “air conditioning”

The transitional system is the same as the respiratory zone

True

What are the three FUNCTIONAL structures in the respiratory tract ?

The conductive system, the transitional system and the gas exchange system.

Which of the following structures is NOT part of the conductive system?

<p>Respiratory bronchioles</p> Signup and view all the answers

Which of the following structures within the respiratory system is noted in BOTH the Transitional system (aka respiratory zone) and the gas exchange system?

<p>Respiratory bronchioles</p> Signup and view all the answers

List the structures that are within the conductive system.

<p>The nasal cavity, pharynx, larynx, trachea and bronchi</p> Signup and view all the answers

What is the primary function of the conducting system in the respiratory tract?

<p>Bringing air to the respiratory portion and conditioning it</p> Signup and view all the answers

Healthy bronchioles contain goblet cells.

<p>False</p> Signup and view all the answers

What are the outpocketings of gas exchange tissue found in respiratory bronchioles called?

<p>Alveoli</p> Signup and view all the answers

The thin-walled structures in the exchange system are known as ______.

<p>alveoli</p> Signup and view all the answers

Match the following cell types with their relevant descriptions:

<p>Type I pneumonocytes = Thin-walled epithelial cells involved in gas exchange Type II pneumonocytes = Cells that produce surfactant Club cells = Non-ciliated secretory cells in bronchioles Ciliated cells = Cells that help move mucus in the respiratory tract</p> Signup and view all the answers

Which of the following is a non-specific defense mechanism of the respiratory system?

<p>Phagocytosis</p> Signup and view all the answers

Mucociliary clearance is classified as a specific (immune-mediated) defense mechanism.

<p>False</p> Signup and view all the answers

What is the primary function of the mucociliary escalator?

<p>To trap and clear mucus and pathogens from the respiratory tract.</p> Signup and view all the answers

The process by which antibodies facilitate the destruction of pathogens is known as _______.

<p>antibody-mediated phagocytosis</p> Signup and view all the answers

Match the following defense mechanisms of the respiratory system with their categories:

<p>Mucous trapping = Non-specific (non immune-mediated) Antibody production = Specific (immune-mediated) Cell-mediated immunity = Specific (immune-mediated) Air turbulence = Non-specific (non immune-mediated)</p> Signup and view all the answers

Histologically the nasal cavity, pharynx, larynx trachea and bronchi are mostly lined with ….

<p>Pseudostratified ciliated columnar epithelium</p> Signup and view all the answers

Which type of epithelium primarily lines the nasal cavity and bronchi?

<p>Pseudostratified ciliated columnar epithelium</p> Signup and view all the answers

Which cells are responsible for secreting mucus in the respiratory tract?

<p>Goblet cells</p> Signup and view all the answers

What type of cells are found submucosally in the nasal cavity and trachea?

<p>Serous cells</p> Signup and view all the answers

Which anatomical structure is NOT lined by pseudostratified ciliated columnar epithelium?

<p>Alveoli</p> Signup and view all the answers

What category of epithelia is Pseudostratified columnar epithelium?

<p>Simple epithelia</p> Signup and view all the answers

What type of glands are primarily found in the lamina propria of the nasal cavity?

<p>Serous tubule-alveolar glands</p> Signup and view all the answers

What is the main function of Bowman's glands located in the nasal cavity?

<p>Production of odorant-binding proteins</p> Signup and view all the answers

Which structure supports the lamina propria within the nasal cavity?

<p>Submucosa</p> Signup and view all the answers

What type of cells are found in the olfactory epithelium?

<p>Olfactory sensory cells</p> Signup and view all the answers

What type of glands have lesser numbers compared to serous glands in the nasal cavity?

<p>Mucous glands</p> Signup and view all the answers

What type of epithelium lines the vestibular region of the nasal cavity?

<p>Stratified squamous keratinized epithelium</p> Signup and view all the answers

Which region of the nasal cavity is primarily responsible for the clearance of inhaled particles?

<p>Respiratory region</p> Signup and view all the answers

What cells are responsible for producing mucus in the respiratory region?

<p>Goblet cells</p> Signup and view all the answers

How do the conchae turbinates function within the nasal cavity?

<p>Regulate air contact with the mucous membrane</p> Signup and view all the answers

Which of the following best describes the olfactory region of the nasal cavity?

<p>Lacks ciliated cells</p> Signup and view all the answers

What occurs in response to injury in the respiratory epithelium?

<p>Hyperplasia of goblet cells</p> Signup and view all the answers

What is the primary characteristic of the respiratory epithelium?

<p>It includes goblet cells for mucus production</p> Signup and view all the answers

In the nasal cavity, what happens to the quality of inhaled air due to the presence of the mucociliary apparatus?

<p>It is filtered to remove particulate matter</p> Signup and view all the answers

What type of epithelium lines the initial part of the larynx?

<p>Stratified squamous epithelium</p> Signup and view all the answers

Which of these structures is primarily found in the larynx?

<p>Cartilage</p> Signup and view all the answers

What type of epithelium replaces the lining after the vocal cords in the larynx?

<p>Pseudostratified ciliated columnar epithelium</p> Signup and view all the answers

Which of the following statements about the larynx is true?

<p>The larynx includes both cartilage and vocal folds.</p> Signup and view all the answers

Which of the following components is NOT part of the larynx?

<p>Trachea</p> Signup and view all the answers

What type of epithelium lines the trachea?

<p>Ciliated pseudostratified columnar epithelium</p> Signup and view all the answers

What type of cartilage supports the bronchi?

<p>Plates of hyaline cartilage</p> Signup and view all the answers

What distinguishes terminal bronchioles from bronchi?

<p>Lack of cartilage and glands</p> Signup and view all the answers

What is a function of Club cells in the bronchioles?

<p>Secretion of surfactant-like substances</p> Signup and view all the answers

What are seromucous glands primarily responsible for?

<p>Secreting mucin, lactoferrin, and lysozyme</p> Signup and view all the answers

Which structure serves as the connection between the trachea and lungs?

<p>Bronchi</p> Signup and view all the answers

What characteristic of the tracheal wall supports its structure?

<p>Rings of incomplete cartilage</p> Signup and view all the answers

Where are Club cells predominantly located?

<p>Terminal and respiratory bronchioles</p> Signup and view all the answers

What type of epithelium lines the respiratory bronchioles?

<p>Ciliated cuboidal epithelium</p> Signup and view all the answers

What distinguishes alveolar ducts from respiratory bronchioles?

<p>Presence of simple squamous epithelial cells</p> Signup and view all the answers

What is the primary function of alveolar sacs?

<p>Facilitate gas exchange</p> Signup and view all the answers

What feature do the lip edges of the alveoli in alveolar ducts exhibit?

<p>Presence of smooth muscle cells</p> Signup and view all the answers

Which structure lacks smooth muscle in its composition?

<p>Alveolar sacs</p> Signup and view all the answers

What do the alveolar (septal) pores of Kohn allow for?

<p>Equalization of pressure and collateral ventilation</p> Signup and view all the answers

What is the composition of the pulmonary interstitium?

<p>Network of interstitial stromal tissue supporting various structures</p> Signup and view all the answers

What is the histologic appearance of the respiratory bronchioles primarily characterized by?

<p>Interruption of the epithelium by alveoli</p> Signup and view all the answers

What is the primary function of Pneumocyte Type I cells?

<p>Gas permeability</p> Signup and view all the answers

Which cell type accounts for 5% of alveolar surface area?

<p>Pneumocyte Type II</p> Signup and view all the answers

What condition is associated with the absence of surfactant in newborns?

<p>Hyaline Membrane Disease</p> Signup and view all the answers

Which component is NOT part of the Blood-Air Barrier?

<p>Cytoplasm of Type II pneumocyte</p> Signup and view all the answers

How is surfactant characterized?

<p>A mono-molecular layer of phospholipoprotein</p> Signup and view all the answers

What triggers the production of surfactant in fetuses just prior to birth?

<p>Cortisol</p> Signup and view all the answers

Which structure primarily acts as a secretory cell in the alveoli?

<p>Pneumocyte Type II</p> Signup and view all the answers

What percentage of the alveolar surface area is composed of Pneumocyte Type I cells?

<p>95%</p> Signup and view all the answers

Which of the following is part of the air-blood barrier?

<p>Type 1 alveolar epithelial cells</p> Signup and view all the answers

What type of blood do pulmonary arteries carry from the right ventricle?

<p>Unoxygenated blood</p> Signup and view all the answers

Which of the following arteries provides oxygenated blood to the major pulmonary vessels?

<p>Bronchial arteries</p> Signup and view all the answers

What role do pulmonary veins play in the pulmonary circulation?

<p>Return oxygenated blood to the heart</p> Signup and view all the answers

What system innervates bronchial smooth muscle to cause contraction?

<p>Parasympathetic nervous system</p> Signup and view all the answers

Which type of capillaries are present in the pulmonary blood supply?

<p>Continuous type</p> Signup and view all the answers

Which of the following statements about bronchial arteries is true?

<p>They originate from the aorta.</p> Signup and view all the answers

Study Notes

Conducting System

  • Delivers air to the respiratory areas, essential for efficient gas exchange.
  • Cleans, moistens, and warms incoming air for optimal conditions.
  • Blood in venous plexuses of the nasal cavity regulates the temperature of inhaled air.
  • Nasal cavity features hair and secretions that trap particulate matter, enhancing filtration.

Transitional System

  • Acts as a transition zone between conducting and gas exchange areas of the respiratory system.
  • Consists exclusively of respiratory bronchioles, which have walls featuring outpocketings called alveoli.
  • Contains specific cells, including Club cells (formerly Clara cells), that are non-ciliated secretory cells.
  • Healthy bronchioles are characterized by the absence of goblet cells, maintaining airflow efficiency.

Exchange System

  • Composed of alveoli, which are crucial for oxygen and carbon dioxide exchange.
  • Alveoli are thin-walled structures surrounded by pulmonary capillaries, facilitating gas diffusion.
  • Lined by two types of epithelial cells: type I pneumonocytes (membranous) for structural support and type II pneumonocytes for surfactant production.

Non-Specific (Non Immune-Mediated) Defense Mechanisms

  • Mucous Trapping: Mucus in the respiratory tract traps particles, pathogens, and allergens, preventing them from entering the lungs.
  • Mucociliary Clearance (Mucociliary Escalator): Cilia move in a coordinated manner to transport trapped mucus up to the throat, where it can be expelled or swallowed, maintaining clear airways.
  • Phagocytosis: Immune cells, such as macrophages, engulf and digest foreign particles and pathogens that reach the alveoli.
  • Air Turbulence: Physical mechanisms like coughing and sneezing create turbulence in airflow, dislodging and expelling unwanted particles and microorganisms from the respiratory system.

Specific (Immune-Mediated) Defense Mechanisms

  • Antibody Production: B-lymphocytes produce antibodies specific to pathogens, enhancing the immune response by targeting and neutralizing invaders.
  • Antibody-Mediated Phagocytosis: Antibodies coat pathogens, promoting their recognition and ingestion by phagocytic cells, enhancing the clearance of infections.
  • Cell-Mediated Immunity: T-lymphocytes directly attack infected cells and coordinate the immune response, playing a crucial role in defending against intracellular pathogens.

Conducting System

  • Responsible for delivering air to the respiratory portion.
  • Cleans, moistens, and warms incoming air through mucous membranes.
  • Blood in venous plexuses within the nasal cavity regulates the temperature of inhaled air.
  • Nasal cavity contains hair and secretions that trap particulate matter.

Transitional System

  • Serves as a transition between the conducting (ciliated) area and the gas exchange (alveolar) area of the respiratory tree.
  • Composed entirely of respiratory bronchioles, which have walls with outpocketings of gas exchange tissue (alveoli).
  • Lined primarily by club cells (formerly Clara cells), non-ciliated secretory cells, and a few ciliated cells.
  • Healthy bronchioles lack goblet cells, distinguishing them from other bronchial structures.

Exchange System

  • Comprises alveoli, which are thin-walled and surrounded by a dense network of pulmonary capillaries for gas exchange.
  • Alveoli are lined with two types of epithelial cells:
    • Type I pneumonocytes (membranous) for structural support.
    • Type II pneumonocytes (pneumocytes) responsible for surfactant production.

Defense Mechanisms of the Respiratory System

  • Non-specific (non immune-mediated) defenses include:

    • Mucous trapping of particles and pathogens.
    • Mucociliary clearance, also known as the mucociliary escalator, which helps expel trapped material.
    • Phagocytosis by immune cells to eliminate pathogens.
    • Air turbulence generated by coughing and sneezing to remove irritants.

  • Specific (immune-mediated) defenses involve:

    • Antibody production to target specific pathogens.
    • Antibody-mediated phagocytosis that enhances immune responses.
    • Cell-mediated immunity, involving T cells to attack infected cells.

Epithelial Lining

  • Nasal cavity, pharynx, larynx, trachea, and bronchi are mainly lined by pseudostratified ciliated, columnar epithelium.
  • This lining features secretory goblet cells and submucosal serous cells for mucus and enzyme production.

Nasal Cavity Structure

  • The lamina propria is rich in tubulo-alveolar glands, primarily serous, contributing to nasal secretion.
  • Contains a minor quantity of mucous and mixed glands, aiding in moisture and protection.
  • Olfactory function is supported by Bowman's glands, which produce odorant-binding proteins essential for the sense of smell.
  • The submucosa serves as a supportive layer beneath the lamina propria, providing structural integrity and containing blood vessels and nerves.
  • Olfactory epithelium houses olfactory sensory cells, which are critical for detecting airborne scents and initiating the olfactory signal pathway.

Nasal Cavity Overview

  • The nasal cavity is a bone-supported space in the skull, divided by the nasal cartilaginous septum into left and right halves.
  • Each half contains three distinct regions: Vestibular, Respiratory, and Olfactory.

Vestibular Region

  • This is the external part of the nasal cavity, characterized by a cutaneous mucous membrane with haired skin and glands.
  • Lined with stratified squamous keratinized epithelium, providing initial protection.

Respiratory Region

  • The largest section, lined with pseudostratified columnar ciliated epithelium containing goblet cells.
  • The Mucociliary apparatus is formed by these cells, facilitating the clearance of inhaled particles.
  • Lateral wall projections, known as Conchae Turbinates, narrow the lumen, enhancing the contact area between inhaled air and the respiratory mucous membrane for better air quality control.

Mucociliary Apparatus

  • Composed of pseudostratified ciliated columnar epithelium and goblet cells that produce mucinogen granules.
  • Cilia work to remove mucus laden with airborne particles such as dust and microorganisms, effectively cleaning the upper respiratory passages.

Goblet Cells

  • Present along the airway up to large bronchioles, these cells secrete mucus that traps particulate matter.
  • In response to injury (such as smoking), there is an increase in the number of goblet cells (hyperplasia) and a potential change from ciliated pseudostratified epithelium to squamous stratified epithelium (metaplasia).

Olfactory Region

  • Lined with olfactory epithelium that is significantly thicker than the respiratory epithelium and does not contain goblet cells.
  • Located in the dorsal part of the nasal cavity, it is involved in the sense of smell (olfaction).
  • Comprising olfactory neurons (axons correspond to Cranial Nerve I), sustentacular cells for support, and basal cells that function as stem cells for regeneration.

Venous Plexuses

  • Both the olfactory and respiratory regions feature rich venous plexuses known as "swell bodies," which can become engorged with blood, potentially influencing nasal congestion and airflow.

Larynx Structure

  • Composed of cartilage, vocal folds, and skeletal muscle, which contribute to its functionality and support.
  • The initial part of the larynx is lined with stratified squamous epithelium, providing protection against friction and abrasion from airflow and sound production.

Epithelium Transition

  • Past the vocal folds, the lining transitions to pseudostratified ciliated columnar epithelium, which aids in filtering and moistening incoming air.
  • This change in epithelial type reflects the differing roles of each section of the larynx, with the initial section focused on protection and the subsequent section emphasizing airway function.

Trachea

  • Lined by ciliated pseudostratified columnar epithelium for effective mucus clearance and protection.
  • The lamina propria and submucosa appear indistinct, reflecting a unique structural feature.
  • Presence of serous glands within the lamina propria/submucosa contributes to moisture and enzyme secretion.
  • Supported by incomplete rings of cartilage, which are not fully formed on the dorsal side to allow flexibility; birds possess complete cartilage rings.
  • The connective tissue adventitia encases the trachea, providing additional structural support.
  • The trachea bifurcates into bronchi, which lead into the lungs and undergo extensive branching.
  • Bronchi are lined with ciliated pseudostratified columnar epithelium similar to the trachea.
  • Surrounding the lamina propria is smooth muscle and connective tissue, containing mixed bronchial glands.
  • Mixed seromucous glands secrete mucin, lactoferrin, and lysozyme, which possess bacteriostatic and cidal properties.

Bronchioles

  • Bronchioles arise from the branching of bronchi and are characterized by the absence of cartilage and glands.
  • Classified into terminal bronchioles and respiratory bronchioles based on their function and structure.

Terminal Bronchioles

  • Lined by ciliated cuboidal or columnar cells, with a reduced presence of goblet cells.
  • Contain muscularis mucosae, which aids in regulating airflow.

Club Cells (Bronchiolar Exocrine Cells)

  • Located in terminal and respiratory bronchioles, identifiable by surface bulging.
  • Serve secretory functions, producing a surfactant-like substance that maintains airway patency.
  • Play a role in metabolizing airborne toxins and may have immune functions.
  • Involved in metabolizing xenobiotic compounds, which are substances foreign to the body or ecological systems.

Respiratory Bronchioles

  • Predominantly developed in cats and dogs, lined with ciliated cuboidal epithelium that flattens distally.
  • Possess incomplete muscularis mucosae, leading to a histological appearance similar to terminal bronchioles, with interruptions by alveoli.
  • Subdivide into alveolar ducts.

Alveolar Ducts

  • Integral to the respiratory exchange system, emptying into alveolar sacs and alveoli.
  • Composed entirely of alveoli, lined with simple squamous epithelial cells.
  • Edges of alveoli contain smooth muscle cells, giving them a knob-like appearance in sections.

Alveolar Sacs

  • Formed by branches of alveolar ducts, lack smooth muscle.
  • Consist of two distinct types of epithelial cells: pneumocytes type I (thin for gas exchange) and type II (produce surfactant).

Alveolar Pores (Pores of Kohn)

  • Connect neighboring alveoli, facilitating pressure equalization and collateral ventilation in case of bronchiole obstruction.
  • Allow macrophage passage between alveoli.

Interstitium

  • Refers to the stroma, or space between cells, filled with an extracellular matrix (ECM) that includes structural, adhesive, and absorptive components.
  • Pulmonary interstitium supports blood and lymphatic vessels, nerves, bronchi, bronchioles, and alveoli.
  • Divided into three compartments:
    • Bronchovascular interstitium surrounding main bronchi and pulmonary vessels.
    • Interlobular interstitium providing support to small blood and lymph vessels.
    • Alveolar interstitium supporting alveolar walls containing pulmonary capillaries with no lymphatic vessels.

Effects of Pulmonary Changes

  • Conditions such as pulmonary edema, emphysema, and inflammation can affect interstitial compartments.

Alveolar Septum and Interstitium

  • Contains fibroblasts, capillaries, and “dust” cells (macrophages).
  • Collagen type III is found in the alveolar walls, while collagen type I is present in conducting airways.
  • Elastic fibers contribute to the structural integrity and function of the pulmonary system.

Pneumocyte Type I

  • Squamous Alveolar Type I Cells form the walls of alveoli.
  • Comprise 95% of the total alveolar surface area, optimizing gas exchange.
  • Extremely thin structure with occluding junctions to prevent fluid infiltration.
  • Function primarily in gas permeability and are not capable of mitosis.
  • Organelles are concentrated around the nucleus for efficient function.

Pneumocyte Type II

  • Granular Alveolar Type II Cells account for 5% of the alveolar surface area.
  • Serve as secretory cells that produce surfactant through lamellar bodies.
  • Capable of mitosis, allowing them to generate both Type I and Type II cells.

Surfactant

  • A mono-molecular layer of phospholipoprotein essential for lung function.
  • Functions to lower surface tension in the alveoli, facilitating inflation and preventing atelectasis (alveolar collapse).
  • Continuously produced by Type II cells; cortisol stimulates surfactant production in fetuses before birth.
  • Lack of surfactant in newborns can lead to Hyaline Membrane Disease.

Blood-Air Barrier

  • Composed of four key components:
    • Vascular endothelium
    • Basement membrane of the endothelial cell
    • Basement membrane of Type I pneumocyte
    • Cytoplasm of the Type I pneumocyte
  • The Air-Blood Barrier includes additional structures:
    • Surfactant covering the cytoplasm of Type I cells
    • Two fused basal laminae from alveolar epithelium and capillary endothelium
    • Endothelial cells facilitating gas exchange.

Air-Blood Barrier Pathway

  • Oxygen travels through the alveolar air, surfactant, and the cytoplasm of Type I cells, passing through the basal laminae of both type I cells and endothelial cells before reaching capillary red blood cells (RBCs).

Pulmonary Macrophages

  • Alveolar Macrophages (PAMs) are key immune cells in the lungs.
  • Intravascular Macrophages (PIMs) play a role in the immune response within blood vessels.

Pulmonary Blood Supply

  • Pulmonary Arteries: Transport unoxygenated blood from the right ventricle, characterized by low pressure.
  • Bronchial Arteries: Supply oxygenated blood to the large bronchi, major pulmonary vessels, and pulmonary lymph nodes; originate from the left heart and aorta.
  • Dual Blood Supply: Representation of functional (pulmonary arteries) and nutritive (bronchial arteries) components in the pulmonary system.
  • Anastomoses: Exist between bronchial and pulmonary arteries within the walls of medium-sized bronchi and bronchioles, particularly notable in horses, cattle, and sheep.

Pulmonary Veins

  • Return all oxygenated blood from the lungs to the left atrium of the heart, occurring at low pressure.

Capillary Structure

  • Continuous Type: Provides a barrier for gas exchange, ensuring the proper function of pulmonary capillaries.

Lymphatic Vessels

  • Drain towards the hilum of the lung; there are no lymphatic vessels within alveolar walls.

Innervation

  • Parasympathetic System: Influenced by the vagus nerve, promotes bronchoconstriction.
  • Sympathetic System: Involves middle cervical and cervicothoracic ganglia, facilitating bronchodilation.
  • Smooth Muscle Contraction: Involuntary process affecting bronchi, bronchioles, and vessels.

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Describe the functions of the respiratory tract, distinguishing features of each section of the respiratory tract etc.

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