Respiratory System and Gas Exchange part 1 (slides 1-50) Flashcards
Respiratory system structure
-The respiratory system consists of three portions:
- An air-conducting portion (also conditions inspired air)
- A respiratory portion for gas exchange between blood and air
- A mechanism of ventilation controlled by the inspiratory and expiratory movements of the thoracic cage
Respiratory system functions
- Olfaction
- Phonation
Conducting versus respiratory portions
- Conducting
- A series of tubes cavities-function?
-Carry air to and from site of gas exchange
Conducting versus respiratory portions
- Conducting portion
- comprised of?
-Comprised of nasal cavity, nasopharynx, larynx, trachea, bronchi, bronchioles, and terminal bronchioles
Conducting versus respiratory portions
- Conducting portion
- Located in?
Located in head and neck
Conducting versus respiratory portions
- Respiratory portion
- Function?
- Extends from what to what?
- Where gas exchange (O2 and CO2) occurs
- Extends from respiratory bronchioles to alveoli
Nasal cavity and paranasal sinuses
-Functions?
- Warming and moistening of air
- Filtering of dust particles present in inspired air
Nasal cavity and paranasal sinuses
- Respiratory portion histology?
- Supported by?
- Respiratory portion is lined by pseudostratified ciliated epithelium with goblet cells
- Supported by a lamina propria with seromucous glands, and rich superficial venous plexus
Nasal cavity and paranasal sinuses
-What happens to incoming air?
Incoming air is warmed by blood in the venous plexus and moistened by secretions of the seromucous glands and goblet cells
Nasal cavity and paranasal sinuses
-Function of conchae (sup, mid, inf)?
Create turbulence to help warm and moisten air
Histology of paranasal sinuses?
Lined by a thin pseudostratified columnar ciliated epithelium with few goblet cells
Respiratory system: wall structure
- "Respiratory epithelium"- lines most of the tract
- histology?
- Respiratory epithelium lines most of the tract
- Histology-ciliated pseudostratified columnar epithelium with goblet cells
Respiratory system: wall structure
- Lamina propria
- description?
- Composition relative to length?
- Loose C.T. containing (sero)mucous glands, elastic fibers, bone/cartilage, and smooth muscle
- COMPOSITION CHANGES THROUGHOUT LENGTH
Respiratory system: wall structure
-Advenitia-2 types of fibers?
Collagen and elastic fibers
Respiratory epithelium
-Type of cell that predominates?
Ciliated columnar cells
Respiratory epithelium
-Function of coordinated cilia movement?
-Coordinated cilia movement moves mucus and/or particulate matter towards the pharynx
Describe the granules in goblet cells
Large and light-staining
Respiratory epithelium
-Mucins-what are they and what do they do?
- Hydrophilic glycoproteins
- Form mucus
Respiratory epithelium
-Where are mucins hydrated?
Extracellularly
Respiratory epithelium
-Where does the cell population taper off?
-Cell population tapers off in terminal bronchioles
Respiratory epithelium-mucus secretion?
- Airway mucus traps inhaled particles and transports them out of the lungs by ciliary beating and cough
- Excessive mucus or deficient clearance are characteristics of all common airway diseases
Respiratory epithelium-mucus secretion?
-Airway mucus is produced by what three secretory cell types?
- Goblet cells
- Clara cells of the terminal bronchioles
- Serous cells of the submucosal glands
Respiratory epithelium-Mucus secretion
-Mucus contains what 4 components?
- Mucins
- Antimicrobial molecules
- Immunomodulatory molecules
- Protective molecules
Respiratory epithelium-Mucus secretion
- Mucus contains 4 components
- Antimicrobial molecules such as?
Defensins, lysozyme, IgA
Respiratory epithelium-Mucus secretion
- Mucus contains 4 components
- Immunomodulatory molecules such as?
Secretoglobin and cytokines
Respiratory epithelium-Mucus secretion
- Mucus contains 4 components
- Protective molecules such as?
Trefoil proteins and heregulin
Goblet cells produce what specific type of mucin?
MUC 5AC
Ciliated cells produce what specific types of mucins?
MUC 1, MUC 4, and MUC 16 (possibly)
Mucus glands produce what specific types of mucin?
MUC 5B and MUC 16
MUC 1, MUC 4, and MUC 16 are know as what type of mucin?
-Found in 2 different forms?
- Tethered mucins
- Found in a cell associated form and a secreted form
Mucin molecules are designed for?
Optimum binding and trapping of inhaled bacteria and particles for clearance from the lung, this is because of the diverse carbohydrate side chains
-It has been suggested that mucins bind most bacteria, viruses, and inhaled particles
2 specific types of mucins that are the main components of the mucin raft?
MUC 5AC and MUC 5B
Respiratory epithelium-Mucus secretion
- normal airway mucus composition? - The hydration of the mucus determines its?
- Normal airway mucus is 97% water and 3% solids (mucins, non-mucin proteins, salts, lipids, and cellular debris)
- The hydration of the mucus determines its viscosity and elastic properties, two essential characteristics for normal clearance of mucus by ciliary action and cough
Respiratory epithelium-Mucus secretion
- Airway mucus consists of two layers?
- What is the position of the layers relative to each other?
- Periciliary layer
- Mucus gel layer atop the periciliary layer
Which mucins are continuously synthesized and secreted to replenish gel layer cleared by ciliary beating to eliminate inhaled particles, pathogens, and dissolved chemicals that might damage the lungs?
Polymeric MUC5AC and MUC5B
Basal cells and neuroendocrine cells (NE, cells of Kulchitsky)
-Where are they located?
They rest on the basal lamina but do not extend into the lumen
Bronchial carcinoid tumors (including small cell lung carcinoma) arise from what type of cell?
-Where do these tumors to metastasize to?
- Neuroendocrine cells (of Kulchitsky)
- Metastasize to regional lymph nodes
What substances are secreted by neuroendocrine cells?
Peptide hormones-serotonin, somatostatin, calcitonin, ADH, and adrenocorticotropic hormone (ACTH)
Trachea-What lines most of the tract?
- “Respiratory epithelium”-lines most of the tract = ciliated pseudostratified columnar with goblet cells
- Lamina propria-loose C.T. containing (sero)mucous glands, elastic fibers, bone/cartilage, and smooth muscle
Trachea-type of cartilage?
15-20 C-shaped rings of hyaline cartilage
Trachea
- Fibroelastic ligament
- types of fibers?
- function?
- Collagen and elastic fibers
- Prevents overdistension of the lumen
Trachea
- Trachealis muscle
- type of muscle?
- Function
Smooth muscle that results in narrowing during cough reflex
When coughing-smaller diameter of trachea causes?
Smaller diameter of trachea increases the velocity of expired air
-Helps to clear the air passage
Bronchi
- As bronchi divide into intrapulmonary bronchi, the tracheal C-shaped rings break down into cartilage plates (distributed around the lumen) and smooth muscle bundles shift between the mucosa and the cartilage plates
- Aggregates of lymphoid tissue are in the wall of intrapulmonary bronchi (known collectively as BALT, bronchial associated lymphoid tissue)
Bronchi
-Secondary (lobar) bronchi
Wall structure similar to main bronchi except:
-Supporting cartilages form irregular plates or islands rather than rings
Bronchi
-Tertiary (segmental) bronchi
- Smaller diameter than mainstream bronchi
- Multiple branchings leading to smaller bronchi and eventually bronchioles
Bronchioles
-Respiratory epithelium?
- Gradually reduces in thickness
- The number of goblet cells is reduced
- Epithelium becomes simple ciliated columnar without goblet cells in the terminal bronchioles
Bronchioles
-Goblet cells are replaced by?
Goblet cells are replaced by clara cells in the bronchioles
Bronchioles
-Clara cells compared to goblet cells?
-Clara cells produce a less viscous secretion
Bronchioles
-Lamina propria becomes dominated by?
The lamina propria of the bronchioles becomes dominated by a spiraling layer of muscularis mucosa in the terminal bronchioles
At what level do glands and cartilage disappear?
-What remains?
- At the level of the bronchioles
- Only a thin layer of adventitia remains in the terminal bronchioles
Bronchioles
-With further divisions and reduction in the diameter of the bronchioles the conducting airways end with?
terminal bronchioles
Asthma
-Characterized by?
-Characterized by reversible bronchoconstriction of the smooth muscle bundles encircling the bronchiolar lumen and mucus hypersecretion by goblet cells
Asthma
- Can be triggered by?
- This leads to?
- Classic symptoms?
- Can be triggered by allergens or autonomic neural factors leading to a reduction in the lumen of the airways
- Classic symptoms-wheezing, cough and dyspnea (shortness of breath)
Terminal bronchiole
- Pulmonary lobule?
- Pulmonary acinus (on slide 24 but doesn’t say what it is)???
A terminal bronchiole and the associated regions of pulmonary tissues that it supplies
Clara (club) cells
- Clara cells are epithelial cells with a dome-shaped apical domain lacking cilia
- They represent 80% of the epithelial cell population of the terminal bronchiole
- Clara cells secrete surfactant that differs from that produced by type II alveolar cells
Clara (club) cells
-After airway injury-Alveolar bronchialization
-After airway injury, clara cells can proliferate and migrate to replenish alveolar epithelial cells
Clara (club) cells
-What happens to airborne toxins?
- Clara cells engulf airborne toxins and break them down via their cytochrome P-450 enzymes (particularly CYP4B1, which is only present in the clara cells)
- Cytochrome P-450 is present in the smooth ER of the clara cells
Cystic fibrosis
-Pathology?
-Cystic fibrosis results in the production of abnormally thick mucus by glands lining the respiratory and GI tracts
Cystic Fibrosis
-Mutation?
-Inherited mutations of cystic fibrosis transmembrane conductance regulator (CFTR) result in defective Cl- transport and increased Na absorption
Cystic Fibrosis
-Bacterial infections are associated with?
Bacterial infections are associated with the thick mucus plugs consisting of entangled MUC5AC and MUC5B polymers and dehydrated mucus
Cystic Fibrosis
-Typical symptoms?
Cough, purulent secretions, and dyspnea
So, what’s happening physiologically in the conducting portion?
- Control of bronchiole diameter (airway resistance)
- When air flows through a tube, the airway resistance makes airflow more difficult
If airway resistance is high, what happens to airflow and the muscle effort it take to produce the airflow?
- If airway resistance is high, the airflow decreases and it takes more muscle effort to produce this airflow
- Opposite if resistance is low
So, what controls the airway resistance?
-Equation?
radius is the main factor
Resistance = (8 x viscosity x L)/r ^4
Why do we want to change the airway resistance?
- “I want to send the air in my lungs to the ‘right’ places
- For right now, that means the air goes to the alveoli that have a good blood supply
Describe how the resistance of the airways is controlled and the consequences of changes in airway resistance
- Contraction of smooth muscle produces changes in radius
- Since resistance is inversely proportional to the radius to the fourth power, a small change in radius –> BIG change in resistance
Decrease radius–>?
Increased resistance to airflow (opposite for increased radius)
We use the changes in resistance to?
We use the changes in resistance to direct the air to the ‘right’ part of the lung-the part with the blood!
Physiology: Dead space
-When you inhale air travels into?
When you inhale, air travels into:
-Trachea–>bronchi–>bronchioles–>eventually to alveoli (gas exchange)
When you inhale, air travels into trachea, bronchi, and bronchioles, however?
The trachea, bronchi, and bronchioles are not designed for gas exchange (wasted)
Physiology: dead space
- The conducting airways dead space because no gas exchange occurs there
- In a normal person, anatomical dead space holds about 150 ml of air
Alveolar dead space
- Occasionally we have alveoli that do not participate in gas exchange
- This alveolar dead space occurs when either there is no blood flow to the alveolus getting air
Physiologic dead space =?
Physiologic dead space = anatomic dead space + alveolar dead space
How does physiologic dead space compare to anatomic dead space in normal, healthy individuals?
In normal healthy individuals physiologic dead space is not that much greater than anatomic dead spaces
Anatomic Dead Space
- Definition?
- Examples?
- Areas of the respiratory system that do not participate in gas exchange by design
- Examples-trachea, bronchi
- Air must travel through them to get to the gas exchange surface in the alveoli
Alveolar Dead Space
-Definition?
- Alveoli that do not participate in gas exchange (despite the fact that they should be)
- Results when an alveoli GETS AIR BUT NO BLOOD
- We all have some, but shouldn’t have too much
Respiratory portion-Characteristics of the wall of a respiratory bronchiole?
-Discontinuous-interrupted by the saccular outpocketing of alveoli
Respiratory portion-the wall of terminal bronchioles is not associated with?
Alveoli
Respiratory portion
- Contains?
- Lining?
- Bundles of smooth muscle fibers that form knobs bulging into the lumen
- Lining epithelium is cuboidal-to-simple squamous
- Elastic fibers
Respiratory portion-Elastic fibers are important components of?
Elastic fibers are important components of the bronchioles and alveolar walls
Pores of Kohn
-Function?
- Connect adjacent alveoli
- Responsible for collateral respiration when blockage of a small bronchiole occurs
Alveolar ventilation
- definition?
- What is it called if it is per minute?
- average value?
- Volume of air reaching the alveoli
- If per minute: VA(dot)
- Average value is 4 L/min
Perfusion (Q)
- Blood that comes from?
- Average value?
- The right ventricle
- Avg value= 5 L/min
Alveolar ventilation
- Definition?
- Calculation?
- How much air actually gets to alveoli
- Alveolar ventilation = (tidal volume-dead space) x resp. rate
- units: ml air/min
Perfusion (Q)
- Definition?
- How should the values of the left and right ventricles compare?
- How much blood to the lungs
- Cardiac output (SV x HR)
- Left and right ventricles should match
The points of the lungs is to?
bring perfusion and ventilation together
Smoker’s respiratory epithelium
-Changes in cell populations characteristic to this?
- Metaplasia
- Change to stratified squamous for better protection
- Decrease in ciliated columnar cells-decrease in movement of mucus
- Increase in goblet cells to protect against pollutants
- Congestion of smaller airways
Smoker’s respiratory epithelium
-Smoker’s melanosis
- Benign focal pigmentations of oral mucosa
- Tends to increase significantly with tobacco consumption
