Chapter 23 - Respiratory System Flashcards
4 Components of Respiration
- Air movement into & out of lungs
- Gas exchange: air to & from blood
- Gas transport in blood
- Gas exchange: blood to & from tissues
Otorhinolaryngology
Study of the diseases of the nose ears, + throat
Pulmonology
Study of the diseases of the lungs
Nose
- Most anterior part is cartilage
- Lined inside w/ mucous membrane
- 2 nostrils (AKA “external nares/anterior nares”) = openings into each half of nasal cavity from outside
Nasal Cavity
- Internal nares (AKA “posterior nares/choanae”) connect each half of nasal cavity into nasopharynx
- Nasal cavity partitioned into right & left half by nasal septum (anterior part = “vestibule”)
- Olfactory receptors in mucosae of inferior surface of cribiform plate and upper surfaces of superior nasal conchae (“Olfactory epithelium”)
- Nasolacrimal (tear) ducts open into each half of nasal cavity
- Hard palate separates oral & nasal cavities
- Soft palate separates nasopharynx from rest of pharynx
Nasal Conchae (AKA “Turbinates”)
- Bony projections which increase surface area
- Covered by mucous membrane (pseudostratified ciliated columnar epithelium)
- Functions: filters, warms & humidifies air
Paranasal Sinuses
- Air-filled spaces in maxillary, frontal, ethmoid & sphenoid bones
- Mucous membrane lined
Sinusitis
Inflammation of mucous membrane of paranasal sinuses
Path of Incoming Air
External nares -> Vestibule -> Superior, middle & inferior meatuses -> Internal nares -> Nasopharynx
Rhinoplasty
Surgical re-shaping of the nose
3 Functions of the Nose
- Warm, moisten & filter air
- Olfaction
- Speech (Structures aid in vocal resonance)
Pharynx
- Muscular tube lined by mucous membrane connecting nasal & oral cavities to larynx & pharynx
- Has 3 subdivisions
3 Subdivisions of the Pharynx
- Nasopharynx
- Oropharynx
- Laryngopharynx
Nasopharynx
- Connects throat to nasal cavity via internal nares
- Site of openings to auditory (Eustachian) tubes
- Contains pharyngeal tonsil (AKA “Adenoid”)
Oropharynx
- Middle portion of pharynx
- Communicates w/ oral cavity via the fauces
- Contains palatine tonsils in anterior lateral wall & lingual tonsils at base of tongue
- Tonsils = Part of immune system
Laryngopharynx
- AKA “Hypopharynx”
- Space between epiglottis/hyoid & mouth of esophagus
- Connects to larynx & esophagus
4 Functions of the Pharynx
- Common passage for air & food/drink
- Routes these substances to either larynx/trachea or esophagus
- Immune functions
- Vocal resonance
Larynx
- AKA “Voicebox”
- Passageway connecting pharynx to trachea
Thyroid Cartilage
- Apex of the larynx
- AKA “Adam’s apple”
- Located at anterior neck
- Contains thyrohyoid membrane (a broad, fibro-elastic sheet of the larynx; attached below to the upper border of the thyroid cartilage)
3 Unpaired Cartilages in Larynx
- Thyroid Cartilage
- Epiglottis
- Cricoid Cartilage
Epiglottis
- Covers glottal opening of larynx during swallowing
- Glottis = true vocal cords (AKA “Vocal folds”) + rima glottidis
Cricoid Cartilage
Connects larynx to trachea via cricotracheal ligament
Tracheotomy
Incision of cricotracheal ligament
3 Paired Cartilages of the Larynx
- 2 Arytenoid Cartilages (Sites of attachment of true vocal cords & intrinsic laryngeal muscles)
- 2 Corniculate Cartilages
- 2 Cuneiform Cartilages
True Vocal Cords (AKA “Vocal Folds”)
- Mucous membrane folds supported by elastic ligaments & are strung across rima glottidis
- Contraction of lateral cricoarytenoid muscles -> adduction
- Contraction of posterior cricoarytenoid muscles -> abduction
- When air passes over true vocal cords -> vibration -> sound (phonation)
- Tightening cords -> Higher pitch
- Relaxing cords -> Lower pitch
4 Factors Affecting Pitch of Voice
- True vocal cord length
- Vocal cord thickness
- Vocal cord elasticity
- Vocal cord tension
Whispering
Only occurs when the small posterior portion of the rima is open
Loudness/Intensity of Voice
- Determined by the amplitude of true vocal cord vibrations
- Amplitude of vibration corresponds to distance of travel of cords
Pitch/Frequency of Sound
- Is the speed of vocal cord vibration
- Corresponds to transit time, which is regulated by tension at which the cords are held by intrinsic laryngeal muscles
- During puberty, larynx & vocal cord growth is rapid in males -> prominent thyroid cartilage & deeper voice
- Vocal resonance from pharynx, oral & nasal cavities & paranasal sinuses
Vestibular Folds (AKA “False Vocal Cords”)
- 2nd pair of folds, spanning the larger laryngeal opening (Rima Vestibuli)
- Capable of full adduction
- Inelastic & less delicate
Epithelial Lining of Larynx
Non-keratinized stratified squamous epithelium above vocal cords & “respiratory epithelium” below
Intrinsic Laryngeal Muscles
- Regulate tension on true vocal cords
- Open & close rima glottidiis
- Posterior cricoarytenoid muscles -> abduction of true vocal cords
- Lateral cricoarytenoid muscles -> adduction of true vocal cords
Extrinsic Laryngeal Muscles
- Raise & lower thyroid cartilage
- Sternothyroid muscles -> Depression of thyroid cartilage
- Thyrohyoids muscles -> Elevation of thyroid cartilage
- Ext. & int. laryng. muscles prevent food from entering the rima glottidis during swallowing
- Coughing reflex expels foreign substances from entering rima glottidis
Heimlich Maneuver (AKA “Abdominal Thrust”)
First aid procedure for clearing obstructing objects from air passages
Laryngitis
Inflammation of the larynx
Laryngeal Cancer
- A disease in which malignant (cancer) cells form in the tissues of the larynx
- Can be caused by excessive alcohol & tobacco use
- Sings & symptoms include sore throat & ear pain
Trachea (AKA “Windpipe”)
- Rigid tube extending from C6 - T5, connecting larynx to primary bronchi at the carina
- Composed of C-shaped hyaline cartilage rings (stiffening tracheal walls to prevent collapse)
- Carina = last tracheal cartilage
- Posterior tracheal wall contains “trachealis muscle” and no cartilage
“Respiratory Epithelium” Lining (Trachea)
- Consists of pseudostratified ciliated columnar epithelium
- Goblet cells produce mucous
- Cilia help w/ mucociliary clearance of dirt, debris & microorganisms
Tracheostomy
An incision in the windpipe to relieve an obstruction in breathing
Intubation
The placement of a flexible plastic tube (“Endotracheal Tube”) into the trachea to maintain an open airway
Bronchial Tree
Consists of:
Trachea -> Right & left primary bronci -> Secondary lobar bronchi -> Tertiary segmental bronchi -> Bronchioles (20 generations) w/ the final generation = terminal bronchioles
*Primary bronchi = extrapulmonary
*Secondary & tertiary bronchi = intrapulmonary
*Each primary bronchus enters lung at hilum
4 Occurrences When Bronchioles Branch
- Amount of wall cartilage decreases
- Amount of bronchiolar smooth muscle increases
- Lumenal diameter decreases
- Epithelial type of mucosa changes
Broncho-constriction
- Contraction of bronchioles
- Parasympathetic effect
Bronchodilation
- Relaxation of bronchioles
- Sympathetic effect
4 Different Types of Epithelia (Bronchi & Bronchioles)
- Respiratory Epith. - Primary, secondary & tertiary bronchi
- Simple ciliated columnar epith. - Larger Bronchioles
- Simple ciliated cuboidal epith. - Smaller Bronchioles
- Simple cuboidal epith. - Terminal Bronchioles
Lungs
Organs of respiration separated by mediastinal structures
Parietal & Visceral Pleurae
- The 2 pleural membranes surrounding each lung
- Visceral = inner membrane surrounding the surface of each lung
- Parietal = outer membrane attached to the inner surface of the thoracic cavity & diaphragm
Pneumothorax
The presence of air/gas in the cavity between the lungs and the chest wall, causing collapse of the lung
Hemothorax
A type of pleural effusion in which blood accumulates in the pleural cavity
Pleuritis
Inflammation of the membranes that surrounds the lungs and line the chest cavity
Pleural Effusions
Excess fluid accumulation the pleural cavity
Atelectasis
Partial/complete collapse of the lung (due to inflation)
Thoracentesis
A procedure to remove excess fluid in the space between the lungs and the chest wall
Primary Bronchi
- Form secondary (lobar) bronchi which lead to each lobe of lung
- Lung lobes separated by fissures
Secondary Bronchi
- Form tertiary (segmental) bronchi
- Each tertiary bronchus -> air to a single bronchopulmonary segment
Differences Between Right & Left Lungs
- Right lung: 3 lobes (superior, middle & inferior); separated by 2 fissures. Contains 10 bronchopulmonary segments
- Left lung: 2 lobes (superior & inferior); separated by 1 fissure. Has 8 or 9 bronchopulmonary segments
Bronchopulmonary Segments
- Branch into bronchioles
- Bronchioles branch to about 6,500 terminal bronchioles (Each -> single pulmonary lobule)
- Approx. 124,000 terminal bronchioles or lobules/ 2 lungs
- Elastic C.T. trabeculae extend into lung parenchyma from hilum & from visceral pleura -> branching -> elastic interlobar septa -> lobules
4 Components of a Pulmonary Lobule
- A lymphatic vessel
- An arteriole
- A venule
- A terminal bronchiole & gas exchange airway
Terminal Bronchioles
- Branch into respiratory bronchioles
- Epithelium changes from simple cuboidal -> simple squamous
- Subdivide into 10 alveolar ducts, which end at alveolar sacs (composed of several individual alveoli
Alveoli
- Blind pockets composed of simple squamous epithelium
- Surrounded by capillary network
Exchange of Respiratory Gases
Occurs when gases diffuse across alveolar-capillary (“respiratory”) membrane (Approx. 0.5 micrometers thick)
4 Cell Types Associated w/ the Alveolus
- Type 1 Alveolar Cells: Squamous Pulmonary Epithelium
- Type 2 Alveolar Cells: Septal cells, secrete surfactant (decreases surface tension)
- Alveolar Macrophages: Provide immune defense
- Fibroblasts: Provide structural support
Respiratory Distress Syndrome of the Newborn
A syndrome in premature infants caused by developmental insufficiency of pulmonary surfactant production and structural immaturity in the lungs
Blood Supply to Lungs
- Pulmonary Arteries: Carries O2-poor blood from heart to lungs
- Bronchial Arteries: Supplies O2-rich blood to lungs
Pulmonary Thromboembolism
- A moving blockage of artery in the lungs
- Can lead to hemoptysis (coughing up of blood)
Tissue Hypoxia
- Lack of O2 supply to lung tissue
- Leads to reflex vasoconstriction, increasing afterload on R. Ventricle -> possible congestive heart failure
- Not logical to perfuse alveoli that are not ventilated (counterproductive)
Ventilation-perfusion Coupling
- The relationship between the amount of air reaching the air sacs of the lungs and the amount of blood reaching the lungs
- Ventilation: Amount of O2 reaching alveoli
- Perfusion: Amount of blood getting to the alveoli
Pulmonary Ventilation
- Movement of air in & out of lungs
- Consists of Inspiration (Inhalation) & Expiration (Exhalation)
External Respiration
- AKA “Pulmonary Respiration”
- Gas exchange across respiratory membranes in lungs
Internal Respiration
- AKA “Tissue Respiration”
- Gas exchange between capillary blood & peripheral tissue cells
3 Components of the Thoracic Cavity
- Ribs
- Intercostal Muscles
- Diaphragm
Respiratory Control Center
- Primary nervous control of respiration
- Found in the reticular formation of the brain stem
3 CNS Nuclei for Respiration
- Dorsal Respiratory Group
- Ventral Respiratory Group
- Pontine Respiratory Group
Dorsal Respiratory Group
- Stimulates inspiratory muscles: diaphragm & ext. intercostal muscles
- For “quiet” breathing
- DRG inactivity -> passive expiration
- Found in medulla
Ventral Respiratory Group
- Pre-Botzinger neuron complex = pacemaker; this area determines the rate of firing of DRG neurons -> inspiratory muscles
- Some VRG neurons -> forceful inhalation, causing accessory muscles of inhalation to contract (Driven by DRG)
- Other VRG neurons -> forceful exhalation, causing accessory muscles of exhalation to contract
* Found in medulla
Pontine Respiratory Group
PRG neurons target DRG neurons to alter basic rhythm of breathing
*Found in pons
Central Chemoreceptors
- Detect CO2 & H+ levels in CSF; determines breathing rate
- When CO2 levels increase, H+ levels increase -> stimulation of medullary DRG -> Increased depth & rate of respiration
- Not sensitive to normal decrease in O2 levels
Peripheral Chemoreceptors
- Carotid & aortic chemoreceptors detect hypoxemia, hypercapnia & acidosis
- Any of the 3 above conditions cause peripheral chemoreceptors to stimulate DRG -> Increased rate & depth of respiration
Hyperventilation
- Increased ventilation depth & rate -> alkalosis
- Often due to severe emotional stress
- Low O2 stimulates DRG less than high CO2
How Proprioceptors Affect Ventilation
Proprioceptors stimulate medullary DRG, increasing breathing rate & depth
Mechanics of Normal Inspiration (Inhalation)
- Medullary DRG -> nerve impulses to:
1. Diaphragm (dome flattens)
2. External Intercostals (moves ribs upwards & outwards)
Forced Inhalation
- Involves diaphragm & external intercostals
- Also involves sternocleidomastoid, scalene & pectoralis minor muscles (accessory muscles)
- The accessory muscles elevate sternum & ribs 1-5
Overall Effect of Inhalation
- Increased thoracic cavity dimensions -> Increased partial vacuum between pleurae -> Expansion of lungs
- Amount of diaphragm flattening -> Increased amount of thoracic volume
- At rest, inspiration = “Active Phase of Breathing” because it requires muscle contraction
Boyle’s Law
- Inverse relationship of gas volume & pressure
- When alveolar pressure decreases below atmospheric pressure, inspiration occurs
Negative Pressure Ventilation
- AKA “Iron Lung”
- A form of medical ventilator that enables a person to breathe when normal muscle control has been lost
2 Possible Causes of Passive Expiration
- Quiet Breathing: Brief inactivity of medullary DRG
- Inflation Reflex: Excessive expansion of lungs -> bronchiolar baroreceptors send nerve impulses to inhibit the medullary DRG
* In either case, diaphragm & ext. intercostal muscles relax
* Expiration is normally considered passive
2 Forces that Propel Air Outward
- Elastic recoil of thoracic wall & lungs
- Intra-alveolar fluid film surface tension (water film surface tension decreases alveolar volumes)
* Decreased alveolar volumes cause increased alveolar pressure -> expiration
* When alveolar pressure > atmospheric pressure -> expiration
* Can also cause collapse of lung
Active Expiration
- Deep rapid breathing -> both inspiration & expiration active
- Internal intercostal muscles -> “Forced Expiration”
- Abdominal wall muscles (external & internal obliques + rectus abdominis) also active during active expiration
2 Mechanisms Preventing Alveolar Collapse
- Surfactant = Detergent made by Type 2 Alveolar cells
- Sub-atmospheric intrapleural pressure (Intrapleural pressure normally < alveolar pressure -> alveoli partially inflated at end of expiration)
3 Factors Affecting Rate of Respiratory Inflow
- Intra-alveolar fluid film surface tension
- Lung & thoracic compliance
- Airway resistance
Lung & Thoracic Compliance
- Ease w/ which lungs & thoracic wall expand
- Decreased compliance -> possible hypoxemia, hypercapnia, acidosis
Airway Resistance
- Exhalation -> Increased intra-thoracic pressure -> Decreased diameter of bronchioles -> Increased airway resistance
- Airway obstruction & bronchoconstriction -> Increased airway resistance
- COPD (emphysema & chronic bronchitis) -> Increased airway resistance
Tidal Volume (TV)
Normally about 500 mL under resting conditions
*Minute ventilation at rest (500 mL x 12 breaths = 6L/min)
Vital Capacity
Sum of inspiratory reserve volume, tidal volume & expiratory reserve volume
Inspiratory Reserve Volume (IRV)
Extra air inspired above tidal volume
Expiratory Reserve Volume (ERV)
Extra volume of air beyond tidal volume that can be exhaled forcibly
Forced Expiratory Volume in 1 Second
- AKA “FEV1”
- Maximal inhalation, then maximal exhalation
Residual Volume (RV)
Volume of air still contained in lungs after a maximal expiration
*Increased in emphysema
Anatomic Dead Space
Air that fills the conducting airways (About 150 mL); never reaches the lungs
*Breathing through a tube increases anatomic dead space & limits air pressure in lungs
Alveolar Ventilation Rate at Rest
12 breaths x 350 mL = 4.2 L/min
3 Other Lung Capacities
- Vital Capacity: IRV + TV + ERV
- Inspiratory Capacity: IRV + TV
- Total Lung Capacity: IRV + TV + ERV + RV
Partial Pressure of a Gas
Pressure exerted by a certain gas in a mixture of gases
Dalton’s Law
Each gas in a mixture exerts its own pressure as if all of the other gases were not present
Atmospheric Pressure
- Sum of all partial pressures of individual constituent gases
- 760 mm Hg at Sea Level = 1 atmosphere
- Nitrogen, oxygen, water vapor, argon and CO2 make up the atmospheric gases (Ordered from highest percentage to lowest)
General Gas Law
- Respiratory gases move from areas of higher pressure to lower pressure
- The pressure of a gas determines its rate of diffusion
Henry’s Law
- If temperature is constant. quantity of a gas that will dissolve in a liquid is proportional to (1) its partial pressure and (2) its solubility coefficient
- CO2 is 24x more soluble than O2
- Higher solubility coefficient means better solubility in solution
Hyperbaric Oxygen Therapy
- Using oxygen at ambient pressure higher than atmospheric pressure
- Forces increased oxygen into a patient’s blood
Nitrogen Narcosis
- When nitrogen concentrates in fatty tissues, creating a narcotic effect
- Occurs when scuba divers remain at depths > 100 ft, causing N2 gas to be forced into solution in blood
Decompression Sickness
- A syndrome occurring in people working at great depths
- If ascent too rapid, nitrogen dissolved in blood -> blood in tissues -> painful “bends” & potentially lethal gas embolisms
O2 Partial Pressure in Lungs (External Respiration)
- PO2 of alveolar air = 105 mmHg
- PO2 of O2-poor blood = 40 mmHg
- O2 diffuses from alveolus into pulmonary capillary
CO2 Partial Pressure in Lungs (External Respiration)
- PCO2 in alveolar air = 40 mmHg
- PCO2 in O2-poor blood = 45 mmHg
- CO2 diffuse out of blood into alveoli
4 Factors Influencing External Respiration
- Partial pressures of gases in alveolar air & pulmonary capillary blood
- Large surface area for gas exchange of “respiratory” membrane
- Thickness of respiratory membrane
- Molecular weight & solubility of gases
4 Factors Influencing Partial Pressures of Gases in Lungs
- Ventilation Rate: Rate of air inflow to lungs
- Lung Perfusion
- Metabolic Activity of Tissues: Determines O2 & CO2 levels
- Altitude: As elevation above sea level increases, O2 gradient decreases
O2 Partial Pressure in Lungs (Internal Respiration)
- PO2 of O2-rich arterial blood = 100 mmHg
- PO2 of peripheral tissue cells = 40 mmHg
- O2 diffuses from capillary into peripheral tissues
CO2 Partial Pressure in Lungs (Internal Respiration)
- PCO2 of O2-rich arterial blood = 40 mmHg
- PCO2 of peripheral tissues = 45 mmHg
- CO2 diffuses out of tissues into blood
2 Modes of O2 Transport
- O2 dissolving in plasma (1.5% of O2)
- O2 carried by heme of RBC hemoglobin (98.5% of O2)
* O2 turns hemoglobin into oxyhemoglobin
* Hb w/ reduced O2 -> deoxyhemoglobin
Rule for O2 binding to Hb
- The higher the PO2, the more O2 binds Hb
- At PO2 of alveolar air, Hb is approx. 100% saturated w/ O2
- At PO2 of most peripheral tissues, Hb releases some bound oxygen
- Hb also more readily releases O2 in actively metabolizing tissues (warmer & more acidic)
5 Factors Affecting O2 & Hb association
- PO2 of alveolar air
- Acid pH (Bohr Effect)
- PCO2 of arterial blood
- Temperature
- 2,3, - biphosphoglycerate
- Increase of 1 causes shift to left, causing increased O2-Hb affinity (& vice-versa)
- Increase of 2,3,4 and 5 causes shift to right, causing decreased O2-Hb affinity, leading to more O2 to tissues (& vice-versa)
Fetal Hb (Hb-F)
- Has greater affinity for O2 than adult Hb
- When PO2 is low, fetal Hb carries 20-30% more O2 than maternal Hb
- Allows maternal blood to transfer O2 to fetal blood in the placenta
Carbon Monoxide Poisoning
- CO = by-product of incomplete oxidation of hydrocarbons
- Problem: CO’s affinity for Hb is > 200x O2’s Hb affinity
- 0.1% CO can compete w/ atmospheric O2 (21%)
3 Modes of CO2 Transport
- 7% dissolves in plasma
- 23% combines w/ Hb -> Carbaminohemoglobin
- 70& transported as HCO3-
HCO3- Formation/Equation
CO2 + H2O H2CO3 H+ + HCO3-
- RBC Carbonic anhydrase speeds up the reaction
- H+ ions released by the reaction are buffered by globin portion
- Underlies Bohr effect which states that Hb’s O2 binding affinity is inversely related to acidity
2 Methods of Chloride Shift in Periphery
- HCO3- ions diffuse out of RBCs & carried in plasma
2. Chloride (Cl-) ions from plasma enter RBCs
2 Methods of Chloride Shift in Lungs
- HCO3- ions diffuse back into RBCs
- Cl- diffuses out of RBCs & back into plasma
* CO2 diffuses out of blood into alveoli for expiration
* RBC Hb is again available to transport O2
