Structure and Function of the Lung Lecture 1 Flashcards
Discuss the dimensions of the trachea and main bronchi
- Adult trachea diameter is 1.8 - 2.5 cm, length 11-13 cm
- Supported by “U” shaped cartilages joined posteriorly by smooth muscle bands
- External pressure of 40 cm H20 is sufficient to compress the trachea
Identify clinical significance of the dimensions for the trachea and bronchi
- Trachea
- 18mm
- Main Bronchi
- 12 mm
- Lobar Bronchi
- 5-8 mm
- Segmental Bronchi
- 4 mm
- Small Bronchi
- 1-3 mm
- Terminal Bronchioles
- 0.7-1 mm
List three factors affecting upper airway tone
- Mouth
- Nose
- Oropharynx
Identify the three areas from teeth to bronchi with the smallest cross-sectional area
Trachea
- 2.54 cm2
Bronchi 1
- 2.33 cm2
Bronchi 2
- 2.13 cm2
Bronchi 3
- 2.0 cm2
Describe the anatomy of the laryngeal cavity and vocal cords
Abductors
- Posterior crycoarytenoids
Adductors
- Lateral Crycoarytenoids
Regulators of tension
- Cricothyroid
- Thyroarytenoid
Larynx and Vocal Cords
- Larynx extends from the epiglottis to cricoid
- True vocal cords attatch anteriorly to thyroid and posteriorly to the arytenoids
- Larynx has poor lymphatic drainage, prone to edema
- Triangular fissure between cords is the glottic opening.
Abductors
Posterior Crycoarytenoids
Adductors
Lateral Crycoarytenoids
Regulators of tension
- Cricothyroid
- Thyroarytenoid
Identify the most narrow portion of thelower airway in adults
- Glottis is the most narrowest part of the lower airway in adult
- Epiglottis is a life threatening condition (Supraglottic croup)
Discuss the effects of recurrent laryngeal nerve damage
- Provides sensation below the cords
- Damage may cause vocal cord palsy (Intermediate position between abducted and adducted state)
- Occurs with radical neck dissection, paroridetomy, and thyroidectomy
- NO muscle relaxant use
What occurs during superior laryngeal nerve damage?
- Provides sensation above the cords and to cricothyroid
- Stimulation may provoke larnygospasm
Descrive the mucosa of the nasopharnx and the trachea
- Trachea
- columnar ciliated epithelium
- Small bronchi
- columnar ciliated epithelium
- Terminal Bronchioles
- cuboidal
- Respiratory Bronchioles
- cubodal between the alveoli
Discuss the intrathoracic section of the trachea and its significance
- Trachea bifurcated assymetically, the right bronchus being wider, shorter, and making a smaller angle, the left being thing and longer
- Foreign bodies tend to enter the right main stem bronchus
- Generations 1-4 have full cartilaginous support
Tracheal Dimensions
- Teeth to cords 13 cm, adult trachea 11 - 13 cm
- Orifice of RUL 1-2.5 cm from the carina, while that of the LUL is 5cm distal
- Right bronchus 25 degrees, left bronchus 45 degrees
- Diameter is 1.8 - 2.5 cm
What are the conducting zones
- Generations 0-16
- Trachea, left and right mainstem bronchi, lobar bronchi, segmental bronchi, terminal broncioles, comprise an anatomic dead space fo 150 ml
What are the respiratory zones
- Generations 17- 23
- Respiratory bronchioles
- Alevelolar ducts and alveoli
Compare and Contrast Epithelium and cartilage in different generations of the lung
- Pseudofied columnar ciliated epithelium
- From nasal cavity to bronchioles
- Mucous is propelled forward by ciliated epithelial cells
- Cuboidal epithelium
- Bronchioles to alveolus
- Goblet cells
- Produce mucous that lines all airways (increased in asthma and cystic fibrosis)
- Other cells found in the respiratory epithelium include basal, mast, nonciliated bronchiolar epithelial, and APUD cells
Epithelium Generation 1-11
Columnar ciliated epithelium
Epithelium Generation 12-18
Cuboidal
Epithelium level 19-23
Cuboidal between alveoli
Identify which bronchus generations have cartilaginous support
- Trachea - U shaped cartilage
- Main Bronchi - U Shaped cartilage
- Lobar Bronchi - Irregular shaped cartilage
- Segemental Bronchi - Irregular shaped cartilage
- Small bronchi - Irregular shaped cartilage
- Terminal Bronchi - NO CARRTILAGE
At what level does the cartilage become absent
Terminal bronchioles
- last site with cartilage are the small bronchi
Identify the cells reponsible for bronchospasm in asthmatics
Mast cells
- Activation is the main cause of immediate bronchospasm seen in allergen induced asthma
Identify the mechansim responsible for maintaining patency of generations 5-11
Patency relies partially on some cartilage in walls and postive transmural pressure gradient
- pressure gradient must exist between pleural space and airway or airway collapse occurs.
Identify the generation of bronchioles where the transition from conduction to respiration occurs.
Generations 17-18
- Transition from conduction to gas exchange occurs here
- gradual increase in nubmer of alveoli in walls of bronchioles
- tremendous increase in cross- sectional area.
Describe the approximate number of alveoli
Total number 2 million to 8 million, depending on height
Describe the amount of surface area available for gas exchange.
On one side of the alveolar wall the capillary endothelium and alveolar epithelium are closely opposed
- Total distance from gas to blood is 0.3 micrometers, where gas exchange is more efficient
- This is known as the active side.
Define Pores of Kohn and their significance
- Small holes in the walls of adjoining alveoli (Alveolar septa)
- Between 3 to 14 u in diameter
- Formation of pores may be due to
- Dequamation due to disease
- Normal degeneration due to aging
- Movement of macrophages leaving holes
Aleveolar Septa “Service Side”
- The other side of the capillary “service side” is usually more than 1-2 mm thick
- Sizeable interstitial space containing elastin, collagen, nerve endings, and macrophages
- Service side is more affected by edema and firbous tissue
Alveolar Septa “Active Side”
One side of alveolar wall where capillary endothelium and alveolar epithelium are closely opposed
- Total distance form gas to blood is 0.3 mm, where gas exhagne is more efficient.
Differentiate between Type I and Type II alveolar
- Alveolar Type 1
- 95% of the alveolar surface is made up of squamous pneumocyte cells
- Between 0.1 U and 0.5 U thick
- major site of gas exchange
- Alveolar Type 2
- 5% of surface of alveoli composed of granular pneumocyte cells
- cubodal in shape with microvilli
- primary source of pulmonary surfactant
- involved with reabsorption of fluid in the dry, alveolar spaces.
Discuss the primary funciton of surfactant
- Acts as a detergent to decrease surface tension
- Pulmonary compliance is increased and work of breathing is reduced
- Permits alveolar stability by keeping smaller alveoli from collapsing into large alveoli
List four functions of the lungs
- Allow oxygen and carbon dioxide exhange
- Maintain/ regulate pH
- Metabolizes/ synthesizes/ converts compounds
- Filters unwanted materials from the circulation
- Acts as a reservoir for blood
- Defense against environment.
Describe the difference between the parietal pleura and visceral pleura and their function
- Parietal pleura lines the thoracic wall
- Visceral pleura covers the lung surface
Compare the role of the sympathetic and parasympathetic nervous system in regulating bronchial tone
- Parasympatetic motor fibers (predominate)
- constrict the bronchi
- affected by medication, mechanical
- Sympathetic (weak)
- dilate the bronchi
- affected by medication, agents.
Identify the most important muscle in respiration and its innervation
- Muscles of pharynx and larynx control upper airway resistance
- Diaphragm, ribcage, spine, and neck muscles control inspiration
- Muscles of the abdominal wall, ribcage and spine are utilized for active expiration
- The most important muscle of inspiration is the diaphragm (75%)
- Innervation is solely from the phrenic nerves (C3, C4, C5)
List three metabolic functions of the lungs
- Conversion of angiotensin I to angiotensin II
- Complete or partial inactivation of vasoactive substances (bradykinin, serotonin, prostaglandins)
- Metabolism of several vasoactive and bronchoactive compounds such as arachidonic acid metabolites (Leukotrienes, prostaglandins, prostacyclin)
- Plays a major role in clotting mechanism (mast cells contain heparin) and immune system (IgA production)
