Lecture: Respiratory System Flashcards
What are the 7 functions of the respiratory system?
1) gas exchange
2) speech and vocalization
3) olfaction
4) controls pH
5) angiotensin II generation (regulates BP)
6) flow of lymph and venous blood
7) valsalva maneuver (equalizes pressure)
What are the 2 major divisions of the respiratory system?
1) conducting zone
- passageway for air
- warms, humidifies, cleanses
- nose, pharynx, larynx, trachea, bronchioles
2) respiratory zone
- actual site of gas exchange
- respiratory bronchioles, alveolar ducts, alveoli
What are the features and functions of the nose?
features:
- anterior naris
- nasal cavity
functions:
- warms, cleanses, humidifies air
- detects odor
- amplifies voice
What is the pharynx? What are its 3 divisions?
muscular funnel from nasal cavity to larynx nasopharynx
-airborne passages
oropharynx
-palatine and lingual tonsils
laryngopharynx
What are the features and functions of the larynx?
features:
epiglottis, cartilage, vestibular folds (includes vocal cords), glottis;
functions:
- food and drink out of airway
- sound production (phonation)
Describe the macro-anatomy of the trachea.
“windpipe”
C-shaped hyaline cartilage;
trachealis muscle controls airflow
Describe the micro-anatomy of the trachea.
inner layer of pseudostratified epithelium
-mucus-secreting goblet cells
-cilitated cells
mucociliary escalator mechanism
connective tissue
- lymphatic nodules
- mucus/serous glands
- tracheal cartilage
Define: mucociliary escalator.
mechanism of debris removal in the trachea in which the mucus traps inhaled particles, and the upward beating of the cilia drives the debris-laden mucus toward the pharynx, where it is swallowed
Describe the exterior anatomy of the lungs.
costal surface (pressed against rib cage);
mediastinal surface (face medially);
-hilum (slit through which the lung receives the main bronchus, blood vessels, lymphatics, and nerves)
-cardiac impression: depression where heart presses against medial surface of left lung
right lung: 3 lobes
left lung: 2 lobes
Describe the anatomy of the bronchial tree.
primary bronchi
-similar to trachea
-elastic CT
secondary or tertiary bronchi
-irregular cartilage plates
bronchioles
-no cartilage
-ciliated cuboidal epithelium
-smooth muscle
terminal bronchioles
-no mucus or goblet cells
respiratory bronchioles
-respiratory division
-lead into alveolar ducts
Describe the macroscopic anatomy of the alveoli.
alveolar sac: cluster of alveoli;
pulmonary capillaries;
alveolus (singular of alveoli)
Describe the microscopic anatomy of the alveoli.
squamous (type I) alveolar: allow for rapid gas diffusion;
great (type II) alveolar: repair type I cells and secrete surfactant, a mixture of phospholipids and protein that decreases surface tension;
alveolar macrophages
What is the respiratory membrane? What are its components?
alveolar air-blood barrier
components:
-squamous alveolar cell
-capillary endothelial cell
-basement membrane
What are the features and functions of the pleurae?
double layered membrane
- visceral pleura
- pareital pleura
- pleural cavity filled w/ pleural fluid;
functions:
- reduction of friction
- creation of pressure gradient
- compartmentalization of thoracic organs
Explain pulmonary ventilation. What muscles are used?
“breathing”
respiratory cycle: inspiration & expiration;
-quiet vs. forced;
respiratory muscles:
- diaphragm
- intercostal muscles
- scalenes
- others with forced breathing
Describe the neural control for breathing.
brainstem respiratory centers located in the medulla and pons;
receptors receive both central and peripheral input
Name and explain the 3 brainstem respiratory centers.
1) dorsal respiratory group (DRG)
- inspiratory neurons
- relaxed, quiet inspiration
2) ventral respiratory group (VRG)
- inspiratory and expiratory neurons
- heavy breathing
3) pneumotaxic area
- shortens breath
- increases respiratory rate
Explain the 4 types of central and peripheral input to the respiratory centers.
1) central chemoreceptors
- brainstem
- respond to pH changes in cerebrospinal fluid
2) peripheral chemoreceptors
- carotid and aortic bodies of large arteries above heart
- O2, CO2, and pH content of blood
3) stretch receptors
- smooth muscle of bronchi and bronchioles
- Hering-Breuer reflex
4) irritant receptors
- epithelial cells of airway
Define: Hering-Breuer reflex.
inhibits inspiration in response to extreme stretching of lungs
For what is voluntary control of breathing important? What is it controlled by? What is it limited by?
important for singing, speaking, breath-holding, etc;
controlled by motor cortex of frontal lobe;
high CO2 levels (kids can’t hold breath and die)
What is the formula which describes flow?
change in pressure / resistance
Explain the 2 different types of pressure which affect respiration.
1) atmospheric pressure
- weight of air above us
- 760 mmHg at sea level
2) intrapulmonary pressure
- internal pressure of lungs
Define: Boyle’s Law.
pressure is inversely proportional to volume
Explain the physical process of inspiration.
thoracic cavity expands
-diaphragm contracts
lungs expand
-pleura (lung surface) clings to rib cage
-intrapleural pressure is created between parietal and visceral pleurae
Define: pneumothorax.
presence of air in the pleural cavity
Define: Charles’ Law.
volume is directly proportional to temperature
Explain the physical process of expiration.
passive process
-muscles relax
-achieved by elastic recoil of thoracic cage
“respiratory braking” = muscles relax gradually rather than abruptly; controlled by phrenic nerve
How is resistance related to airflow?
resistance is inversely proportional to airflow
What 2 factors determine resistance to airflow?
1) diameter of bronchioles
bronchoconstriction
-stimulated by parasympathetic nerves & histamine bronchodilation
-stimulated by sympathetic nerves
2) pulmonary compliance
-ease of lung expansion
-compliance = change in volume / change in pressure
What is a major limitation of pulmonary compliance?
surface tension
surfactant disrupts hydrogen bonds, reduces surface tension, and prevents parts of the airway from collapsing during expiration
Define: eupnea.
relaxed, quiet breathing;
12-15 breaths/min
Define: apnea.
temporary cessation of breathing
Define: dyspnea.
labored, gasping breath;
shortness of breath
Define: hypernea.
increased rate and depth of breathing in response to exercise, pain, or other conditions
Define: hyperventilation.
increased pulmonary ventilation in excess of metabolic demand
Define: hypoventilation.
reduced pulmonary ventilation
Define: alveolar gas exchange.
O2 enters bloodstream, CO2 enters lungs;
exchange occurs across respiratory membrane
What are the 3 processes of gas exchange and transport?
1) alveolar gas exchange
2) gas transport
3) systemic gas exchange
Define: Dalton’s law.
total pressure = sum of partial pressures of constituent gases
Define: Henry’s law. How does it relate to alveolar gas exchange?
at the air-water interface, for a given temp, the amt of gas that dissolves in the water is determined by its solubility in water and its partial pressure in the air;
PO2 of alveolar air higher than PO2 of blood arriving at alveolus;
PCO2 of arriving blood higher than PCO2 of alveolar air;
equilibrium reached in 0.25 seconds
What 5 variables affect the efficiency of alveolar gas exchange?
1) pressure gradients
2) solubility of gases: CO2 is about 20x more soluble in water
3) membrane thickness
4) membrane area
5) ventilation-perfusion coupling
Define: ventilation-perfusion coupling.
physiological responses that match airflow to blood flow and visa versa;
occur in pulmonary arteries and bronchioles
Define: gas transport.
carrying gases from alveoli to tissues;
carrying gases from tissues to alveoli;
gases: O2 and CO2
How is oxygen transport accomplished?
accomplished by hemoglobin of RBC
-carries 4 molecules of O2
Define: oxyhemoglobin.
hemoglobin with ≥ 1 O2 molecule bound to it
Define: deoxyhemoglobin.
hemoglobin with no O2 molecules bound to it
Explain the oxyhemoglobin dissociation curve.
relationship between hemoglobin saturation and PO2
In what 3 forms is carbon dioxide transported?
1) bicarbonate ion in plasma
CO2+ H2O < - > H2CO3< - > H++ HCO3-
-catalyzed by carbonic anhydrase
2) chemically bound to Hb
-carbaminohemoglobin (HbCO2)
Hb + CO2 → HbCO2
3) Dissolved in blood plasma
Define: carbaminohemoglobin.
HbCO<sub>2</sub> carbamino compound (CO<sub>2</sub>bound to amino groups of plasma proteins and hemoglobin)
What are the 2 processes of systemic gas exchange?
loading & unloading
Explain the the loading process of systemic gas exchange.
diffusion of CO2 from tissues into blood stream b/c of concentration gradient;
-CO2 produces HCO3- in RBC (catalyzed by carbonic anhydrase);
HCO3- pumped out of cell in exchange for Cl- (called chloride shift)
Define: chloride shift.
exchange of HCO3- out of RBC into blood plasma and Cl- into cell from blood plasma
Explain the the unloading process of systemic gas exchange.
diffusion of O2 from bloodstream into tissue b/c of concentration gradient;
utilization coeffecient;
venous reserve
Define: utilization coeffecient.
proportion of O2 in the blood which diffuses into tissues as it passes through the capillaries
Define: venous reserve.
O2 remaining in blood after it passes through the capillary bed;
4-5 minutes of oxygen reserve
How is the amount of O2 unloaded by hemoglobin to tissues adjusted? What 4 factors determine the rate of O2 unloading?
hemoglobin adjusts unloading based on needs of tissue;
1) ambient PO2:at low PO2, hemoglobin releases more oxygen
2) temperature: high temp promotes O2 unloading
3) Bohr effect: decrease in pH promotes unloading
4) Biphosphoglycerate (BPG): by-product of RBC metabolism that promotes unloading
Define: Haldane effect.
rate of CO2 loading adjusted according to needs of tissue;
low levels of oxyhemoglobin increase CO2 transport
What 3 physical characteristics of arterial blood is breathing adjusted to maintain normel levels of?
pH = 7.40
PCO2 = 40 mmHg
PO2 = 95 mmHg
(listed in order of importance)
Ultimately, pulmonary ventilation is adjusted to maintain what?
brain pH;
High [H+] in CSF stimulates central chemoreceptors
Define: acidosis. What is the most common cause? What is the corrective homeostatic response?
blood pH < 7.35;
most common cause = hypercapnia (PCO2 > 43 mmHg);
hyperventilation occurs to “blow off” CO2 faster than the body produces it
What is the direct effect of CO2 on respiration? Indirect effect?
increased PCO2 stimulates peripheral chemoreceptors;
-stimulate increase in ventilation;
indirectly related to pH levels
What is the effect of oxygen on respiration?
little effect (normally);
hemoglobin saturation fairly constant;
< 60 mmHg arterial PO2:
-peripheral chemoreceptors stimulated, causing an increase in ventilation and O2 loading
