Respiratory System Chapter 21
Respiratory gas equilibrium
- PO2 and PCO2 are stable in the alveoli and tissues - Equilibrium disrupted when tissue oxygen demand increases •Respiratory rate and tidal volume must increase •Without that increase, alveolar PO2 levels decrease, and alveolar, blood, and tissue PCO2 levels increase -Can lead to hypoxia and dangerous drop in pH
Level 1: Respiratory rhythmicity centers
-most basic control -pacemaker cells in medulla oblongata generate cycles of contractions in diaphragm -paired respiratory rhythmicity centers establish pace of respiration by adjusting pacemaker cells and coordinating other respiratory muscles • Each center subdivided into two groups: 1. Dorsal respiratory group (DRG): • Chemoreceptors detecting O2, CO2, and pH levels in blood/CSF • Baroreceptors - stretch receptors; monitor stretch of lung wall • Mainly concerned with inspiration • Inspiratory center of DRG controls lower motor neurons to primary inspiratory muscles (external intercostals, diaphragm) 2. Ventral respiratory group (VRG) • Mainly associated with expiration • Functions only when breathing demands increase and accessory respiratory muscles are involved
Carbon dioxide transport in blood
1. Dissolved in plasma (~7%) 2. Enters RBCs and is bound to Hb (~23%) • HbCO2 or carbaminohemoglobin 3. Enters RBCs and is converted to bicarbonate ion (~70%) • Reversible reaction catalyzed by carbonic anhydrase • CO2 + H2O → H2CO3 → HCO3- + H+ • HCO3- exchanged out of cell with Cl- (chloride shift) • H+ binds to Hb, forming HbH+ (which acts as pH buffer)
During quiet breathing...
Active inhalation via inspiratory muscles, Passive exhalation—done by elastic recoil of tissues and gravity, NO EXPIRATORY MUSCLES
stimuli that trigger respiratory reflexes
Chemoreceptors, baroreceptors, stretch receptors, irritating physical or chemical stimuli
Lower respiratory system does....
Conducts air to and from gas exchange surfaces
When are Accessory inspiratory muscles activated to assist primary inspiratory muscles?
EX. Running, to increase speed/amount of rib movement to move more air when needed
What is external respiration?
Exchange of gases between interstitial fluids and external environment, Includes pulmonary ventilation (breathing), alveolar ventilation (movement of air into and out of alveoli)
upper respiratory system does....
Filters, warms, and humidifies incoming air Protects delicate lower tract Reabsorbs heat and water in outgoing air
Temperature affects hemoglobin saturation
Higher temp: Hb to release oxygen more readily Especially important in active tissues (generate heat)
Superior movement of the rib cage
Increases the depth and width of the thoracic cavity, increasing its volume and decreasing pressure within it
Vital Capacity (VC)
Maximum amount of air you can move in or out of lungs per cycle, ERV + VT + IRV
Pulmonary ventilation must be closely regulated to....
Meet tissue oxygen demands
upper repsiratory system consists of
Nose, nasal cavity, paranasal sinuses, pharynx
What is internal respiration?
Oxygen absorption and carbon dioxide production by tissue cells
Which of the following events would you predict as carbon dioxide is released from your muscles into the surrounding capillary bed?
Oxygen delivery to muscle is increased when more carbon dioxide is produced by the muscle.
What is the relationship between the pressures at label "8"?
P outside < P inside
In internal respiration, in arriving oxygenated blood, CARBON DIOXIDE...
PCO2 - 40 In normal interstitial fluid: PCO2 = 45 Carbon dioxide diffuses into blood from tissues
In external respiration, In arriving deoxygenated blood, CARBON DIOXIDE...
PCO2 = 45 In alveoli : PCO2 = 40 Carbon dioxide diffuses into alveoli from blood
In external respiration, In arriving deoxygenated blood, OXYGEN....
PO2 = 40 In alveoli: pCO2 = 100 Oxygen diffuses into the blood from alveoli
In internal repsiration, in arriving oxygenated blood, OXYGEN..
PO2 = 95 In normal interstitial fluid: PO2 = 40 oxygen diffuses into the tissues from blood
Blood pH directly affects hemoglobin saturation (Bohr effect)
Ph decrease: saturation curve shifts right Ph increase: saturation curve shifts left
During start of a breath, no air movement occurs
Pressure outside = Pressure inside
The following is a list of some airways. 1. secondary bronchus 2. bronchioles 3. alveolar ducts 4. primary bronchus 5. respiratory bronchiole 6. alveoli 7. terminal bronchiole The order in which air passes through is
Primary bronchus, Secondary Bronchus, Bronchioles, Terminal Bronchiole, respiratory bronchiole, alveolar ducts, alveoli (4, 1, 2, 7, 5, 3, 6.)
Bronchioles have....
Thick layers of smooth muscle that allow for bronchoconstriction (asthma) and bronchodiliation
During exhalation
Thoracic cavity decreases (dec volume) Pressure outside < Pressure inside Air is forced out from an area of high pressure to low pressure Intrapulmonary pressure > atmospheric pressure
During inhalation
Thoracic cavity enlarges (inc volume) Pressure outside > pressure inside Air moves in from an area of high pressure to low pressure Intrapulmonary pressure < atmospheric pressure
Total Lung Capacity (TLC)
Total volume of lungs, averages 6000ml in adult males and 4200ml in adult females, VC + RV
What are the characteristics of Pneumocytes Type I in alveolar structure and what is their primary function? a) Thick and robust, involved in gas exchange b) Thin and delicate, sites of gas diffusion c) Secretory cells producing surfactant d) Immune cells responsible for phagocytosis
b) Thin and delicate, sites of gas diffusion
Most of the carbon dioxide in the blood is transported as
bicarbonate ions in the plasma
Boyle's Law of Gases states that
if the volume goes up, the pressure goes down.
Dalton law
in a mixed gas, each individual gas contributes its individual pressure (partial pressure) toward total pressure of the gas mixture
In quiet breathing,
inspiration involves muscular contractions and expiration is passive
When the diaphragm contracts and moves inferiorly
it increases the volume of the thoracic cavity, decreasing pressure within (change in volume= change in pressure)
lower respiratory system consists of
larynx, trachea, bronchus, bronchioles, respiratory bronchioles, alveoli
Respirator mucosa does..
lines nasal cavity through large bronchioles
Blood arriving in pulmonary arteries has:
low PO2 and high PCO2 than in alveolar air
What is Anoxia?
no oxygen, Much of damage caused by heart attacks and strokes is is due to this
Respiratory Rate (RR)
number of breaths per minute ~12-18 for resting adults
The glottis is
opening to the larynx
Exhalation is usually a _____ process done by___________ and ______
passive process done by elastic recoil and gravity
pulmonary ventilation is driven by
pressure changes within the pleural cavities
The respiratory mucosa consists of
pseudostratified ciliated columnar epithelium and underlying areolar tissue called LAMINA PROPRIA
The process of respiration that moves air into and out of the lungs is __________.
pulmonary ventilation
Respiratory reflexes provide...
rapid automatic adjustments in pulmonary ventilation
During exhalation, the mucosa....
reabsorbs heat and water; reduces heat loss and water loss to environment
In nasal cavity, veins do what?
release heat to warm inhaled air
2,3-bisphosphoglycerate (BPG)
released by RBCs as they break down glucose for energy Binds to hemoglobin and increases release of oxygen
Terminal bronchioles branch to
respiratory bronchioles
Which of the following can be calculated if the tidal volume and respiratory rate are known?
respiratory minute volume
Henry law
the amount of a particular gas in a solution is directly proportional to its partial pressure (at set temperature)
Inspiratory Capacity (IC)
the volume of air inhaled after a normal exhale (TV+IRV)
If a patient being tested inhales as deeply as possible and then exhales as much as possible, the volume of air expelled would be the patient's
vital capacity
The glottis is made of
vocal folds and rima glottidis
What is the tidal volume of the lungs?
volume of air moved into and out of lungs in normal breath
Functional residual capacity (FRC)
volume of air remaining in the lungs after complete quiet cycle, ERV + RV
Accessory expiratory muscles are used
when need to force exhalation (EX blowing up a balloon), Decrease thoracic cavity volume quickly
oxygen-hemoglobin saturation curve
• Graph showing hemoglobin saturation (percentage of heme units bound to oxygen at a given moment) at different partial pressures of oxygen • Has an "S-shape" due the increased hemoglobin affinity for oxygen with each oxygen molecule bound • Areas of the curve with a steep slope have large changes in Hb saturation with small changes in plasma PO2
areolar ventilation (Va)
• Is amount of air reaching alveoli/minute • Some air never reaches alveoli; remains in conducting portion of lungs (= anatomic dead space VD) • At rest, VD averages ~ 150 mL • Is calculated as breaths per minute multiplied by volume of air in the alveoli (tidal volume minus anatomic dead space • VA = f × (VT - VD) • Air reaching alveoli is a mix of "used" air and freshly inhaled air • = Less oxygen in alveolar air compared to atmospheric air
Level 3: Higher Centers
• Located in hypothalamus, limbic system, and cerebral cortex • Can alter activity of pneumotaxic centers • Normal breathing can occur without higher input
The left lung has how many lobes?
2 (superior and inferior) created by oblique fissure
The right lung has how many lobes?
3 lobes (superior, middle, inferior) created by horizontal and oblique figures
Ends of C-shaped tracheal cartilage connected by ELASTIC LIGAMENT and TRACHEALIS MUSCLE do....
Allows expansion of esophagus during swallowing, Allows tracheal constriction (parasympathetic stimulation) or dilation (sympathetic stimulation)
Minimal Volume (MV)
Amount of air in the lungs if they were allowed to collapse, Included in residual volume, Cannot be measured in a healthy person
Residual Volume (RV)
Amount of air remaining in the lungs after a forced exhalation
Expiratory Reserve Volume (ERV)
Amount of air that can be forcefully exhaled after a normal tidal volume exhalation
Inspiratory Reserve Volume (IRV)
Amount of air that can be forcefully inhaled after a normal tidal volume inhalation
Each terminal bronchiole supplies air directly to
a single pulmonary lobule
paranasal sinuses are and do...
air-filled cavities lined with mucous membrane, located in the bones of the skull. Mucus secreted by sinuses helps to moisturize and clean nasal cavity surfaces
Respiratory bronchioles lead to
alveolar ducts, then to alveolar sacs composed of alveoli
What are the three layers of the blood air barrier?
alveolar epithelium, fused basement membrane (alveolar and capillary), capillary epithelium
What is the function of alveolar macrophages in the alveolar structure, and how do they contribute to maintaining lung health? a) They produce oxygen for cellular respiration b) They regulate blood pH levels c) They locate and phagocytize particles that could clog the alveoli d) They secrete surfactant to prevent alveolar collapse
c) They locate and phagocytize particles that could clog the alveoli
Describe the role of Pneumocytes Type II in the alveolar structure, including the substance they secrete and its function. a) They secrete mucus to trap pathogens b) They produce antibodies to fight infections c) They secrete surfactant to reduce surface tension d) They facilitate gas exchange through their thin membranes
c) They secrete surfactant to reduce surface tension
During most daily activities, the human respiration rate is most closely linked to the blood levels of ________.
carbon dioxide
Bronchioles lack what?
cartilaginous support
vestibular folds
close glottis during swallowing, prevent foreign objects
When gas is contained
collisions with container wall cause pressure, More collisions = more pressure, decreasing container volume = even more collisions (pressure)
Two divisions of the respiratory system
conducting (nasal cavity to larger bronchioles) and respiratory (smallest bronchioles to alveoli)
What is hypoxia?
deficiency in the amount of oxygen reaching the tissues, Severely limits metabolic activities
Which of the following is not a function of the nasal mucosa?
dehumidify the incoming air
The hilium
depression in an organ where blood vessels and nerves enter and leave
primary inspiratory muscles include:
diaphragm (~75% of movement & flattens floor of thoracic cavity) and external intercostals (~25% of movement & elevate ribs)
Water from mucus....
evaporates to humidify inhaled air
Bowles Law
for a gas in a closed container and at a constant temperature, pressure (P) is inversely proportional to volume (V); it determines direction of air movement during pulmonary ventilation.
The vocal folds (contain vocal ligaments)
function in voice production (speech); also called the true vocal cords.
A decrease of blood pH from 7.4 to 7.2 causes hemoglobin to ________.
give up more of its oxygen molecules
Hemoglobin (Hb)
• Molecule with four protein subunits that transports 98.5% of oxygen in blood (remaining 1.5% dissolved in plasma) • Each subunit contains one heme unit (containing iron) that can reversibly bind one oxygen molecule • With bound oxygen, is called oxyhemoglobin (HbO2) • Carbon monoxide (CO) is dangerous because it can also irreversibly bind to heme units, making them unavailable for O2 transport
chemorecptor reflexes
• PCO2 is the most important factor influencing respiration • Small changes in PCO2 levels cause large changes in respiratory rate - rise of only 10% in arterial PCO2 doubles respiratory rate; in contrast, PO2 levels have to drop below 60 mm Hg before triggering respiratory centers • Hypercapnia (increased arterial PCO2) • Most commonly caused by hypoventilation • Hypocapnia (decreased arterial PCO2) • Most commonly caused by hyperventilation • Snorkelers sometimes hyperventilate to increase dive time • Oxygen starvation may occur while underwater (= shallow water blackout)
Level 2 Pneumotaxic and Apneustic centers
• Paired nuclei in pons • Adjust the output of the respiratory rhythmicity centers 1. Apneustic centers • Promote inhalation by stimulating DRG • Degree of stimulation adjusted based on sensory information from the vagus nerve about lung inflation 2. Pneumotaxic centers • Inhibit apneustic centers • Promote passive or active exhalation • Increased pneumotaxic output shortens inhalation duration (= faster respiratory rate) • Decreased output slows pace and increases depth of respiration
Respiratory minute volume (Ve)
• Volume of air moved per minute • Equals breaths per minute multiplied by tidal volume • VE = f × VT • Variation in either factor will affect VE and also can affect alveolar ventilation
3 levels of regulation
➢ Level 1: Respiratory rhythmicity centers ➢ Level 2: Apneustic and pneumotaxic centers ➢ Level 3: Higher centers
