Respiratory Module 1 Part 2

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Questions and Answers

What is the likely consequence of damage to the external branch of the superior laryngeal nerve (SLN)?

Inability to breathe normally

Severe airway obstruction

Total loss of voice

Weakness and huskiness of voice (correct)

In the event of bilateral recurrent laryngeal nerve (RLN) injury, what position do the vocal cords assume?

Fully open position

Fully closed position

Intermediate position

Floppy or together position (correct)

Which of the following conditions can cause stridor after a thyroidectomy?

Unilateral RLN injury

SLN damage

Bilateral RLN injury (correct)

Tetany due to hypercalcemia (correct)

How many divisions or generations does the tracheobronchial tree consist of?

23 Signup and view all the answers

What type of airways solely serve to conduct air between the external environment and sites of gas exchange?

Cartilaginous airways Signup and view all the answers

What is the primary function of the Posterior Cricoarytenoid muscle?

Abducts the vocal cords Signup and view all the answers

Which muscle is responsible for adducting the vocal cords?

Lateral Cricoarytenoid muscle Signup and view all the answers

What effect does the Cricothyroid muscle have on the vocal cords?

Tenses the vocal cords Signup and view all the answers

What is the role of the Thyroarytenoid muscle in relation to the vocal cords?

Relaxes the cords Signup and view all the answers

Which muscle opposes the action of the Posterior Cricoarytenoid muscle?

Lateral Cricoarytenoid muscle Signup and view all the answers

What is the primary function of the transverse arytenoid muscles?

Pull arytenoid cartilages together Signup and view all the answers

How does the contraction of thyroarytenoid muscles affect phonation?

Lowers frequency of phonation Signup and view all the answers

Which nerve branch provides motor innervation to the cricothyroid muscle?

External branch of superior laryngeal nerve Signup and view all the answers

What happens to the voice if the recurrent laryngeal nerve is paralyzed?

Voice becomes weak and rough Signup and view all the answers

Which part of the larynx receives sensory innervation from the internal branch of the superior laryngeal nerve?

Laryngeal side of the epiglottis to true cords Signup and view all the answers

What role does the cricothyroid muscle play in phonation?

Tenses the vocal cords Signup and view all the answers

Which nerve is responsible for providing sensory innervation to the laryngeal mucosa inferior to the vocal cords?

Inferior laryngeal nerve Signup and view all the answers

What is the primary action of the external branch of the superior laryngeal nerve?

Lengthen the vocal cords Signup and view all the answers

What type of epithelium primarily lines the tracheobronchial tree?

Pseudostratified columnar ciliated epithelium Signup and view all the answers

Which of the following factors is known to decrease mucociliary transport?

General anesthetics Signup and view all the answers

What is the composition of the mucous layer that covers the epithelial lining of the tracheobronchial tree?

95% water and 5% glycoproteins Signup and view all the answers

What contributes to the production of mucus in the tracheobronchial tree?

Goblet cells and submucosal glands Signup and view all the answers

What role do the cilia in the tracheobronchial tree play?

Propel mucus and foreign particles towards the larynx Signup and view all the answers

Which of the following is a component of the lamina propria in the tracheobronchial tree?

Loose fibrous tissue Signup and view all the answers

What increases the volume of tracheal mucus flow in individuals with COPD?

Increased number of mucus-producing goblet cells Signup and view all the answers

Which types of cells are found along the basement membrane of the epithelial lining?

Basal cells and mucous cells Signup and view all the answers

Which antibody is primarily involved in the allergic response?

IgE Signup and view all the answers

What response does mast cell degranulation trigger upon exposure to an allergen?

Increased vascular permeability Signup and view all the answers

What is the angle of the right mainstem bronchus relative to the trachea?

25° Signup and view all the answers

What causes bronchial edema during an allergic asthmatic attack?

Inflammatory response to histamine Signup and view all the answers

Which layer is absent in bronchioles smaller than 1 mm in diameter?

Cartilage layer Signup and view all the answers

What is the primary characteristic of the trachea's cartilage structures?

They are C-shaped and incomplete posteriorly Signup and view all the answers

What is a major chemical released from mast cells during an allergic response?

Histamine Signup and view all the answers

How many IgE receptor sites can be estimated per mast cell?

100,000-500,000 Signup and view all the answers

Which condition involves airway constriction and increased mucus production?

Asthma Signup and view all the answers

What structural characteristic of the trachea allows it to remain flexible?

Fibroelastic membrane posteriorly Signup and view all the answers

Study Notes

Intrinsic Muscles of the Larynx

Control the movement of vocal cords
Posterior Cricoarytenoid Muscle: Abducts the cords (dilates the cords)
Lateral Cricoarytenoid Muscle: Adducts the cords, positions them to close the rima glottis allowing air to pass
Transverse Cricoarytenoid Muscle: Adducts the cords causing air to pass through, closes the rima glottis
Thyroarytenoid Muscle: Relaxes the vocal cords, reduces cord tension, shortens the cords
Cricothyroid Muscle: Tenses the vocal cords, elongates the cords

Intrinsic Muscles and Function

Posterior Cricoarytenoid Muscle: Pulls the inferior and lateral angles of the arytenoids causing the cords to pull apart, ABDUCTION
Lateral Cricoarytenoid Muscle: Pulls laterally on the lateral angles of the arytenoids causing the cords to move together, ADDUCTION, opposes the action of the Posterior Cricoarytenoid muscle.
Transverse Arytenoid Muscle: Pulls the arytenoid cartilages together, positions the cords for vibration as air passes through during exhalation, generates sound, speech, and singing.
Thyroarytenoid Muscle: Lies within the vocal cords and lateral vocal ligaments, contraction pulls the arytenoids forward, loosens the vocal cord ligaments, allows for lower frequency phonation.
Cricothyroid Muscle: Located on the anterior surface of the larynx, swings the entire thyroid cartilage anteriorly, tenses the cords, changes the frequency of phonation.

Nervous Innervation

Vagus Nerve (CN X): Innervates the larynx, has two branches:
- Superior Laryngeal Nerve: Arises from the ganglion nodosum of the vagus nerve, divides into two branches:
  - Internal Branch: Provides sensation to the laryngeal side of the epiglottis to true cords (tongue side is innervated by the glossopharyngeal nerve), innervates the interarytenoid muscle (phonation).
  - External Branch: Motor nerve to the inferior constrictor muscle of the pharynx and the cricothyroid muscle, lengthens or increases tension of the cords.
- Inferior Laryngeal Nerve (Recurrent Laryngeal Nerve): Left side descends with the vagus and loops around the aorta and comes back up. Right side travels with the vagus along the subclavian artery loops around the artery and comes up. Supplies sensation to the larynx (except the cricothyroid part).

Nervous Innervation: Motor & Sensory

Motor Innervation:
- External Branch of the Superior Laryngeal Nerve: Innervates the cricothyroid muscle (tenses the cords)
- Recurrent Laryngeal Nerve: Major motor nerve of the larynx
Sensory Innervation:
- Internal Branch of the Superior Laryngeal Nerve: Major sensory nerve of the larynx, supplies laryngeal tissue from the vocal cords upward.
- Recurrent Laryngeal Nerve: Supplies sensory innervation to the laryngeal mucosa inferior to the cords.

Laryngospasm

Sensory: Internal Branch of the Superior Laryngeal Nerve (branch of the vagus)
Motor: External Branch of the Superior Laryngeal Nerve (branch of the vagus)
Muscle involved: Cricothyroid Muscle, tenses the cords.

Clinical Application

Damage to the External Branch of the SLN: Weakness and huskiness of voice. The cricothyroid muscle is paralyzed, preventing the cords from being tensed.
Unilateral Right RLN Injury: Hoarseness as the paralyzed cord assumes an intermediate position.
Bilateral RLN Nerve Damage: Each cord is paralyzed and assumes an intermediate position, the cords can flop together causing airway obstruction, aphonia (loss of voice), and is a rare life threatening emergency, requiring immediate intubation.
Hoarseness after Subtotal Thyroidectomy: Can be caused by either Unilateral RLN injury or SLN damage (rarely).
Stridor Following Thyroidectomy: Caused by either Hypocalcemia (tetany) or Bilateral RLN injury (floppy cords).

Tracheobronchial Tree

The pathway air travels after passing through the larynx, a series of branching airways.
Consists of 23 divisions or generations.
Airways progressively become:
- Narrower
- Shorter
- More numerous

Tracheobronchial Tree: Airways

Cartilaginous Airways: Serve only to conduct air between the external environment and sites of gas exchange.
Non-Cartilaginous Airways: Serve as both conductors and sites of gas exchange.

Histology of the Tracheobronchial Tree

Composed of three layers
- Epithelial Lining: Primarily pseudostratified ciliated columnar epithelium (extends from the trachea to the bronchioles)
 - 200 cilia per ciliated cell
 - As bronchioles become smaller, columnar cells become more cuboidal with less cilia, disappearing in respiratory bronchioles.
 - Mucous Glands: Separated by the lamina propria by the basement membrane (along which are basal and mucous cells), prominent in bronchioles; disappear in terminal bronchioles.
 - Brush Cells: Found in the epithelial lining.
- Lamina Propria: The submucosal layer of the tracheobronchial tree, composed of loose fibrous tissue. Contains:
 - Tiny blood vessels
 - Lymphatic vessels
 - Branches of the vagus nerve
 - Two sets of smooth muscle fibers that wrap around the tracheobronchial tree
 - The outer portion is surrounded by a thin connective tissue layer called the peribronchial sheath
- Cartilaginous Layer: Outermost layer, progressively diminishes in size, absent in bronchioles < 1mm in diameter.

Tissue Cell Types

Stratified Squamous Epithelium: Found in the trachea
Pseudostratified Columnar Ciliated Epithelium: Found in the trachea and bronchi
Simple Cuboidal Epithelium: Found in the bronchioles
Simple Squamous Epithelium: Found in the alveoli

Mucous Layer

Covers the epithelial layer of the tracheobronchial tree.
Composed of:
- 95% water
- 5% glycoproteins, carbohydrates, lipids, DNA, cellular debris, and foreign particles
Mucus Produced By:
- Goblet Cells: Found within the epithelium
- Submucosal Glands: Innervated by the vagal parasympathetic nerve fibers (CN X), produce 100 ml bronchial secretions per day, increased sympathetic activity decreases gland secretion.

Mucous Blanket

Two distinct layers
- Sol Layer: Cilia move in a wavelike motion propelling mucus and foreign particles toward the larynx, also known as Mucociliary Transport.
- Gel Layer: More viscous.

Factors That Decrease Mucociliary Transport

Cigarette smoke
Dehydration
Positive pressure ventilation
Endotracheal suctioning
High inspired O2 concentrations
Hypoxia
Atmospheric pollutants (sulfur dioxide, nitrogen dioxide, ozone)
General anesthetics
Parasympatholytics (atropine)
Exposure to irritants (tobacco smoke), increases the number of mucus producing goblet cells and decreases the number of ciliated cells, resulting in increased volume of tracheal mucus flow which is seen in COPD.

Immune Response

Humoral Immune Response: Occurs in the lamina propria, involves circulating antibodies, and is involved in allergic responses like allergic asthma.
Antibodies (Immunoglobulins): Serum globulins or proteins that defend against antigens (pollen/dander)
- IgG: Involved in secondary immune responses
- IgA: Found in mucosal membranes
- IgM: First antibodies produced in response to infection
- IgD: B cell receptor
- IgE: Reaginic antibody, involved in allergic response

IgE antibody Antigen Reaction

Susceptible individual exposed to an antigen.
Lymphoid tissue releases IgE antibodies.
IgE antibodies attach to surface receptors on mast cells (estimated 100,000-500,000 IgE receptor sites per mast cell). Individuals are considered “sensitive” to the specific antigen once the IgE antibodies attach to the mast cell.
Each mast cell contains 1000 secretory granules containing chemical mediators.
Continued exposure or re-exposure to the same antigen creates an antigen-antibody reaction on the surface of the mast cell, which works to destroy or inactivate the antigen.
This response causes the mast cell to degranulate (break-down).

Mast Cell Releases

Chemicals Released: During the antigen-antibody-IgE response, mast cells release:
- Histamine
- Heparin
- Slow-reacting Substance of Anaphylaxis (SRS-A)
- Platelet activating factor (PAF)
- Eosinophilic chemotactic factor of anaphylaxis (ECF-A)
Chemical Release from Mast Cells:
- Increases vascular permeability.
- Smooth muscle contraction (bronchial)
- Increased mucus secretion
- Vasodilation
- Edema

Allergic Asthma

Bronchial edema
Bronchospasms
Wheezing
Increased mucus production
Air trapping
Lung hyperinflation

Cartilaginous Airways (Conducting Airways)

Trachea
Main Stem Bronchi
Lobar Bronchi
Segmental Bronchi

Trachea

11-13 cm long (10-12 cm Barash)
- Incisors to carina  26 cm
1.5-2.5 cm in diameter (20 mm Barash)
Extends from the cricoid cartilage of the larynx to the level of the second costal cartilage or T4-T5.
At the level of the carina, the trachea divides into the right and left mainstem bronchi.
Contains 15-20 "C" shaped cartilage rings that are incomplete posteriorly.
Shares a fibroelastic membrane posteriorly with the esophagus.
Tracheal epithelial layer: pseudostratified columnar ciliated epithelium (damaged by exposure).

Trachea: Key Facts

Blood Supply: Inferior thyroid artery (branch of the subclavian artery)
Incisors to carina: 26 cm
Incisors to larynx: 13 cm
Innervated by: Vagus nerve
Diameter: Approximates the index finger.
Not a fixed structure: Moves with head flexion and extension.

Tracheostomy vs. Cricothyrotomy

Tracheostomy: Incision is below the cricoid cartilage
Cricothyrotomy: Incision is between the cricoid cartilage and the thyroid cartilage

Main Stem Bronchi

First generation.
- Right: Branches off at a 25° angle, wider, more vertical, 5 cm shorter than the left.
- Left: Branches off at a 40-60° angle (45° M&M), less steep.

Lobar Bronchi

Second generation of the tracheobronchial tree.
- Left:
  - Upper
  - Lower
  - Branches off trachea at a 45° angle.
- Right:
  - Upper
  - Middle
  - Lower
  - Greater diameter than the left.
  - Branches off the trachea at a 25° angle.
  - More likely for aspiration or endobronchial intubation to occur.
C-shaped cartilages that support the trachea and mainstem bronchi progressively form cartilagenous plates around the bronchi.

Right Mainstem Bronchus

Leaves the trachea at a 25° angle.
More likely for aspiration or endobronchial intubation to occur in the right.
Right upper lobe bronchus drives almost directly posterior at a 90° angle.
Foreign bodies and aspirated material generally end up in the right upper lobe.

In Children

Foreign bodies are more likely to lodge in the right main stem bronchus.
This is due to the fact that the right mainstem bronchus is shorter, wider, and more vertical than the left mainstem bronchus, and the right upper lobe bronchus is more horizontal than the left.
As such, more careful attention should be paid to the airway in children with signs of airway obstruction.

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Test your knowledge on the intrinsic muscles of the larynx and their functions. This quiz covers the various muscles, including their roles in controlling vocal cord movement through abduction and adduction. Understand how each muscle contributes to speech and breathing.