Chapter 16: Respiratory System Flashcards
Functions of the Respiratory System
Ventilation
Gas exchange
Oxygen utilization
Alveoli
Air sacs where gas exchange occurs in the lungs
300 million (760 square feet of surface area)
One-cell layer thick
Type I Alveolar Cells
95-97% total SA, where gas exchange occurs
Type II Alveolar cells
secrete pulmonary surfactant, reabsorb sodium and water, prevent fluid buildup
Conduction zone
gets air to the respiratory zone
- transports air
- voice production
- warms, humidifies, filters, and cleans the air (by mucus, cilia)
Respiratory zone
site of gas exchange
Atmospheric pressure
pressure of air outside the body
Intrapulmonary/Intra-alveolar pressure
pressure in the lungs
Intrapleural pressure
pressure within the intrapleural space
- contains a thin layer of fluid to act as a lubricant
- lower than intrapulmonary and atmospheric pressure
- keeps lungs against the thoracic wall and allows them to expand
Inspiration
intrapulmonary pressure < atmospheric pressure
Expiration
intrapulmonary pressure»_space; atmospheric pressure
transpulmonary pressure
difference between intrapulmonary and intrapleural pressure
- positive during inspiration and expiration
Lung compliance
Lungs can expand when stretched
- change in lung volume per change in transpulmonary pressure
Boyle’s Law
The pressure of a gas is inversely proportional to its volume
Pulmonary Fibrosis
reduce lung compliance due to resistance to distention
- scarring of lungs due to aging
Elasticity
Ability of the lungs to return to initial size after being stretched
Tension ________ during inspiration and ________ during exhalation due to _______ ________
Tension INCREASES during inspiration and DECREASES during exhalation due to ELASTIC RECOIL
Surface Tension
Resists distension by surfactant secreted by Type II alveolar cells
- raises pressure of alveolar air to prevent collapse
Law of Laplace
Pressure is directly proportional to surface tension and inversely proportional to radius of the alveolus
P = 2T/r
Small alveoli are more/less at risk of collapse
MORE at risk (without surfactant)
Pneomothorax
Lung collapse due to air entering the pleural space which raises the intrapleural pressure.
- spontaneous (puncture from broken rib, lung disorders like COPD, cystic fibrosis, lung blister rupture)
Surfactant
secreted by type II alveolar cells
- hydrophobic protein and phospholipid
- reduces surface tension of water (decreases H bonds)
- prevents alveolar collapse
RDS
Respiratory Distress Syndrome
- lack of surfactant
- in premature babies and adults with septic shock or pneumonia (produces hypoxemia)
Spirometry
records volume and frequency of air movement from subject
- measures lung volumes and capacities
Anatomical Dead Space
Volume of air in the conducting zone that “hangs out”, not used for gas exchange, not fully replaced with each breath
Restrictive Pulmonary Disorders
Lung tissue is damaged, vital capacity is reduced
- forced expiration is NORMAL
pulmonary fibrosis, emphysema
Obstructive Pulmonary Disorders
Lung tissue is NORMAL, vital capacity is NORMAL
- forced expiration is reduced
Asthma
FEV1 Test
Forced Expiratory Volume Test
- diagnose obstructive lung disorders
- percentage of vital capacity that can be exhaled in 1 second
- <80% = obstructive disorder
Barometer
measures atmospheric pressure
- sea level = 760 mmHg OR 1 atm
Dalton’s Law
total pressure of a gas mixture is = sum of the pressures of gas in it
Partial pressure
pressure of an individual gas
- measured by multiplying the % of that gas by the total pressure
Effect of water vapor on atmospheric total pressure
Takes away from it, at 37*C water pressure = 47 mmHg
- so for atmospheric partial pressure in the lungs: 760 - 47 = 150 mmHg
The amount of gas dissolved in liquid depends on:
- the solubility of the gas (constant)
- Temperature of the fluid (constant for blood)
- Partial pressure of the gases (DETERMINING FACTOR)
Pulse Oximeters
measures % oxyhemoglobin saturation (via a noninvasive fingertip clip)
- uses light to measure absorbance (different between oxyhemoglobin and deoxyhemoglobin)
Regulation of breathing (neurons in 2 areas)
Voluntary: from cerebral cortex
Involuntary: from respiratory control centers of the medulla oblongata + pons
Apneustic center
promotes inspiration
- stimulates medulla inspiratory centers
Pneumotaxic center
inhibits inspiration
Pons
influence medulla activity via apneustic center to promote inspiration
- pneumotaxic center inhibits inhalation
Chemoreceptors
automatic control of breathing
- monitor pH of brain fluids & pH and partial pressure for O2 and CO2 in the blood
- 2 types
Central chemoreceptors
in retrotrapezoid nucleus of the medulla
Peripheral chemoreceptors
in carotid and aorta arteries
Hypoventilation
CO2 levels rise, pH falls (Hypercapnia)
Hyperventilation
CO2 levels fall, pH rises (hypocapnia)
How to maintain constant levels of CO2 in the blood
Regulation of ventilation
- hypoventilation = increase CO2
- hyperventilation = decrease CO2
PCO2 = 40 mmHg
Hering-Breuer reflex
stimulated by pulmonary stretch receptors to make sure you do not inhale too deeply
- inhibits respiratory centers as inhalation proceeds
Sleep Apnea
Obstructive condition: periods of hypopnea and apnea during sleep = partial/complete collapse of the upper airway
- oxyhemoglobin saturation falls = chemoreceptor reflex stimulated = gasp and jerk to wake up
- may cause pulmonary hypertension
CPAP
continuous positive airway pressure
- worn by those with sleep apnea to keep the oropharynx air passage open
How many hemoglobin per RBC
280 million, each can carry 4 molecules of O2
Percent Oxyhemoglobin Saturation
% oxyhemoglobin to total hemoglobin
- should be 97%, any lower is alarming
- measured via pulse oximeter
Anemia
below-normal hemoglobin levels
Polycythemia
above-normal hemoglobin levels
- adaptation to high altitudes (lack of atmospheric oxygen)
- caused by erythropoietin
Erythropoietin
made in the kidneys, stimulates hemoglobin production in red bone marrow when O2 levels are LOW
- over production = polycythemia
Oxyhemoglobin dissociation curve
Sigmoidal curve, high PO2 = lots of UNLOADING, low PO2 = lots of LOADING
- steep change for maximum unloading in tissues compared to in lungs
pH and Oxygen transport
High pH = greater O2 affinity = more loading
Low pH = less O2 affinity = more unloading
- relates to exercise…
Exercise and O2 transport
Increased metabolism = more CO2 = lower pH = more O2 unloading = more O2 transport to muscles
- temperature increases O2 UNLOADING also
2,3-DPG
2,3 diphosphoglyceric acid is made from anaerobic metabolism of glucose by RBCs
- produced in the anemic or people at high altitudes
- increases O2 UNLOADING
CO2 is carried through the blood:
- Dissolved in plasma
- As carbaminohemoglobin (attached to an amino acid in hemoglobin)
- As bicarbonate ions (Major form)
Carbonic anhydrase
enzyme that catalyzes the formation of carbonic acid (from CO2 and water) at high [CO2]
- later it dissociates into bicarbonate and hydrogen ions
Chloride Shift
Cl- are attracted to H+ ions left in RBCs (attached to hemoglobin) as bicarbonate ions diffuse out of RBC and into the plasma
- keeps electrical neutrality of RBC
Reverse Chloride Shift
In pulmonary capillaries, high [O2] favors oxyhemoglobin production = H+ dissociate from hemoglobin and recombine with bicarbonate to form carbonic acid
- low [CO2] = carbonic acid is converted by carbonic anhydrase into CO2 and water = chloride diffused out of RBC as bicarbonate enters = CO2 is exhaled
Acid-Base Balance
pH = 7.35-7.45
- maintained by lung and kidney functions
Acidosis
blood pH = <7.35
- caused by hypoventilation (rise of CO2) or excessive production of acids or loss of bicarbonate via diarrhea
Alkalosis
blood pH = >7.45
- caused by hyperventilation (blow off CO2) or inadequate production of acids (or vomiting stomach acids) or overproduction of bicarbonates
ROME (acid-base mnemonic)
Respiratory measured by plasma CO2, rise in CO2 = drop in pH (Respiratory Opposite)
Metabolic measured by bicarbonate, rise in HCO3 = rise in pH
(Metabolic Equal)
Ventilation and Acid-Base Balance compensation
Metabolic acidosis = hyperventilate to blow off excess CO2
Metabolic alkalosis = hypoventilate to build up CO2
