Chapter 22- The respiratory system Flashcards
Gas exchange
Body tissues must be supplied with oxygen, carbon dioxide waste must be disposed of. Gasses only move in one direction during gas exchange (might not be in the same direction for every gas)
4 processes involved with gas exchange
- Pulmonary ventilation
- External respiration
- Transport of respiratory gasses to/from tissues- does not occur in the respiratory system
- Internal respiration- does not occur in the respiratory system
External respiration
Gas exchange occurring in the lungs (alveoli)
Internal respiration
Gas exchange occurring in the tissues (does not occur in the respiratory system). If PCO2 in tissues is greater than PCO2 in blood- carbon dioxide leaves tissues and enters blood. If PO2 in blood is greater than PO2 in tissues- oxygen leaves blood and enters tissue. Partial pressure and diffusion gradients are opposite to external respiration
2 zones of the respiratory system
- Conducting zone
2. Respiratory zone
Conducting zone
Respiratory passages leading from the nose to the respiratory bronchioles. Transports air to/from the lungs- no gas exchange, just movement of air
Respiratory zone
Actual site of gas exchange. Found in respiratory bronchioles, alveolar ducts, and alveoli
Upper conducting zone (2 parts)
- Nasal cavity
2. Pharynx
Nasal cavity function
Air is warmed and humidified as it passes through this cavity. Inhaling cool/dry air slows down respiration overall- warming and humidifying ensures a normal respiratory rate
Mucous membranes of the nasal cavity
Consists of the respiratory mucosa- contains 2 different types of cells. Nerve endings in membrane- invading debris triggers a sneezing reflex
2 cell types of the respiratory mucosa
- Goblet cells
2. Seromucous nasal glands
Goblet cells
Mucus producing cells. We usually only notice mucus during a cold
Seromucous nasal glands
“Mucus” portion traps particles and debris- immune function- clears pathogens. “Serous” portion secretes watery fluid containing lysozyme
Vascularization of the mucous membranes of the nasal cavity
Capillaries and veins located superficially to help warm air as it passes through- they sit very close to the surface of the membrane. This is why damage to these vessels can cause severe nosebleeds
3 regions of the pharynx
- Nasopharynx
- Oropharynx
- Laryngopharynx
Nasopharynx
Contains pharyngeal tonsils and tubal tonsil. Closes during swallowing by soft palate and uvula (dangling thing at back of throat)- stops food/liquid from getting in
Oropharynx
Meets oral cavity at the isthmus of the fauces. Contains palatine tonsils and lingual tonsils
Laryngopharynx
Where respiratory and digestive passages split. The lower conducting zone divides the laryngopharynx from the respiratory passages
Parts of the lower conducting zone (4)
- Epiglottis
- Larynx
- Trachea
- Bronchi
Epiglottis
Cartilage flap that closes off lower conducting zone. Function- separates food and air passageways
Larynx composition
Composed of cartilage- provides an open airway. Consists of thyroid cartilage and cricoid cartilage- XY individuals tend to have an Adam’s apple (testosterone makes thyroid cartilage larger and thicker). The larynx contains vocal cords for sound production
Glottis
Open passageway surrounded by vocal cords. Vocal cords are ligaments composed of elastic fibers, the fibers vibrate as we exhale to produce sound
Sound pitch vs sound loudness of vocal cords
If chords are tense, they vibrate more quickly- higher pitch. Increased testosterone usually causes the chords to be longer and looser, causing a deeper voice. Loudness increases as air is passed across the cords with greater force. Many sound properties are created by other structures- tongue, lips, etc.
Trachea composition
Windpipe. Composed of elastic fibers and cartilage rings. Elastic fibers provide flexibility- trachea can stretch/relax while breathing cartilage rings prevent the trachea from collapsing. Without the cartilage rings, the trachea and larynx would collapse between breaths. It would take a large amount of work to breathe
Trachealis
Smooth muscle tissue of the trachea, innervated. Contraction leads to diameter of the trachea decreasing and air forced upward . Ex- coughing reflexes remove things from the lungs
Bronchi
Allow air to reach the respiratory zone. The trachea branches to form 2 main bronchi, bronchi branch 20-25 times to eventually form bronchioles. Smallest of the bronchioles in the conducting zone are terminal bronchioles.
Lungs
Organ where external gas exchange occurs. Lungs composed of air space and elastic connective tissue. Lungs are elastic in nature- ensures that the lungs don’t become permanently stretched out with breathing- you would need more and more air to fill them
Hilum
Each lung has a hilum- point at which the bronchi and any blood/nerve supply enter/leave the lung
Blood supply to lungs
Pulmonary artery brings oxygen poor blood to lungs- artery branches in a similar pattern as bronchi. The pulmonary vein moves oxygenated blood away from the lungs. The pulmonary capillary network immediately surrounds alveoli- where external gas exchange takes place
Pulmonary plexus
Where nerve fibers enter the lungs
Innervation of the lungs
Lungs have both parasympathetic and sympathetic fibers. Parasympathetic causes the air tubes to constrict- if resting, you don’t need to bring in a huge amount of air. Sympathetic causes the air tubes to dilate- using your skeletal muscle tissue more, use more oxygen
Pleurae function
Thin, double layered serous membrane (visceral and parietal layers). Produces pleural fluid, which fills cavity between visceral and parietal layers. Also creates chambers for each lung.
Parietal pleura
Covers the thoracic wall and the upper portion of the diaphragm
Visceral pleura
Covers external lung features
Importance of pleural fluid
Pleural fluid fills the cavity between visceral and parietal layers. Importance- lungs can “slide” over structures as they change in size. There is a very small amount of fluid between the layers- difficult to get the layers apart. Visceral and parietal pleura are “stuck” together.
What are the benefits of having a chamber for each lung? (2)
- As organs move/shift with breathing, etc.- organs cannot interfere with others
- Prevents spread of infection from one organ to another- prevents spread to another lung or heart
Branching pattern of respiratory bronchioles
Branch from the terminal bronchioles of the conducting zone, lead into alveolar sacs composed of multiple individual alveoli.
Alveoli
Multiple alveoli are grouped into each alveolar sac. Alveoli are covered with capillary beds. Gas exchange occurs via diffusion- the walls of the alveoli are made of simple squamous epithelium, and are very thin to facilitate gas exchange. Individual alveoli connected to “neighbors” via alveolar pores- ensures that all alveoli in the sac are able to fill with air
3 cell types of alveoli
- Type 1 alveolar cells
- Type 2 alveolar cells
- Alveolar macrophage
Type 1 alveolar cells
Squamous epithelial cells. Function- creates walls of alveoli- where gas exchange and diffusion occurs
Type 2 alveolar cells functions (2)
Cuboidal cells scattered among type 1 cells, less common. Functions:
- Secrete surfactant, a detergent like substance. Surfactant prevents alveoli from collapsing as air leaves during exhalation
- Secrete antimicrobial proteins- innate immunity
Alveolar macrophage
Mobile cells, travel through the lung tissue. Function- consume debris, pathogens, etc.- protect internal alveolar surfaces
2 processes involved with respiratory physiology
- Pulmonary ventilation
2. Gas exchange
Pulmonary ventilation
The flow of air into and out of the lungs. Air flows according to a pressure gradient, from high pressure to low pressure
Gas exchange
The exchange of respiratory gasses across the alveolar wall. Respiratory gasses can move from air space in lungs to blood, or from blood to air space in lungs. The same gas will always move in the same direction.
3 gas laws influence the process of gas exchange and pulmonary ventilation
- Boyle’s law
- Dalton’s law of partial pressures
- Henry’s law
Boyle’s law
The volume of a gas is inversely proportional to the pressure exerted by the gas on the walls of its container. A gas always fills a container- as gas molecules move around and bump into each other, they create pressure. More moving around= more pressure. If you change the volume of a container filled with gas, the pressure within the container will change
How is Boyle’s law important for pulmonary ventilation?
Inhalation and exhalation changes the volume of the lungs. Changing the volume of lungs changes the pressure of air in the lungs- air moves according to pressure gradient
Pressure in the lungs always described relative to
Atmospheric pressure. At sea level, atmospheric pressure (Patm)= 760 mm Hg
Intrapulmonary pressure (Ppul)
Pressure in the alveoli. Changes as you inhale or exhale, but always equalizes Patm at some point
Which 2 muscles initiate inspiration?
- Diaphragm
2. Intercostal muscles
Diaphragm function during inspiration
During contraction, diaphragm flattens and is pulled down- thoracic cavity increases in size. Gives the lungs room to increase in size
Intercostal muscles function during inspiration
During contraction, intercostal muscles pulls ribs outward- thoracic cavity increases in size
How does air pressure in the lungs change during inspiration?
As thorax increases in size during inhalation, lungs are naturally pulled outward. Volume of the lungs increases- intrapulmonary pressure decreases, and Ppul is less than Patm. Then, air flows into lungs along the pressure gradient (high to low pressure). Inspiration ends when Ppul = Patm
Damage to pleura can cause
A collapsed lung
How does expiration occur?
Expiration mostly due to lung elasticity. Respiratory muscles relax, return to resting length. Elastic fibers of the lungs recoil- lungs become smaller in size
How does pressure in the lungs change during expiration?
Lungs recoil, pull thorax walls with them- thoracic and intrapulmonary volume decrease. Decrease in intrapulmonary volume= increase in pressure in the lungs, and Ppul is greater than Patm. Air flows out of lungs along the pressure gradient. Expiration ends when Ppul= Patm
Respiratory volumes
The amount of air that can be pushed into/out of lungs during ventilation
Types of respiratory volumes (4)
- Tidal volume (TV)
- Inspiratory reserve volume (IRV)
- Expiratory reserve volume (ERV)
- Residual volume (RV)
Tidal volume (TV)
Normal volume of air that moves into and out of lungs during normal breathing at rest. Restrictive respiratory diseases prevent the lungs from filling as they should. Causes by lack of elasticity in the lungs or by problems with the respiratory muscles
TV normal value
In healthy individuals- 500 ml air
Inspiratory reserve volume (IRV) and normal value
Amount of air that can be inspired forcibly past the tidal volume. 2100-3000 ml air
Expiratory reserve volume (ERV)- normal value
Amount of air that can be forced from lungs after a normal tidal volume expiration. 1000-1200 ml air
Residual volume (RV)- normal value
Amount of air left in the lungs after forced expiration, 1200 ml air. The lungs are never completely empty of air- ensures that they stay inflated
Respiratory capacities
The sum of two or more respiratory volumes. Give an idea about the health of the lungs, whether a person is sufficiently ventilating
Inspiratory capacity (IC)
Total amount of air that can be inspired after a normal tidal volume expiration. Restrictive lung diseases decrease inspiratory capacity-can’t get enough air into the lungs
IC equation
IC= TV + IRV
Functional residual capacity (FRC)
Amount of air remaining in the lungs after a normal tidal volume expiration. High FRC indicates a person can’t remove enough air from the lungs- can cause buildup of carbon dioxide. Can also be caused by loss of elasticity in the lung, not recoiling like they should means that air can’t get out
FRC equation
FRC= RV + ERV
Vital capacity (VC)
Total amount of exchangeable air, RV is not involved here. Increase in vital capacity means a person has more exchangeable air- is exchanging more oxygen and carbon dioxide.
VC equation
VC= TV + IRV + ERV
Total lung capacity (TLC)
The total amount of air the lungs can hold after a maximum inhalation. More based on lung size overall than health. The lungs can only get so big and the thoracic cavity can only expand so much- smaller people will generally have a smaller lung capacity
TLC equation
TLC= IRV + TV + ERV + RV
Dead space
The air that fills the conducting zone, but never contributes to gas exchange- larger conducting zone structures never contribute to gas exchange
Anatomical dead space value
150 ml air for a healthy individual- 1 ml of air per pound of ideal body weight. Remember- TV is 500 ml, air used for gas exchange: 500 ml - 150 ml= 350 ml
Alveolar dead space
Air reaches the alveoli, but no gas exchange occurs- don’t want to have this dead space. This is due to localized damage or collapse of alveoli, can be damaged by certain diseases. Example- blockage from mucus. Also, not being able to produce surfactant makes the alveoli collapse
Total dead space
Anatomical dead space and alveolar dead space. These are considered “Non-useful volumes”
Dalton’s Law of Partial Pressures
Atmospheric pressure is the sum of the pressures of the different gasses that make up air that we breathe. The pressure of each individual gas in the mixture is the partial pressure (PP). The PP of one gas is independent of the PP of a different gas in the mixture. Importance- if we know partial pressures of each gas, we can see pressure gradients that drive diffusion into and out of the blood
Which gasses contribute to atmospheric pressure?
Nitrogen (79%) and oxygen (20.9%) account for about 99% of atmospheric pressure. Small amounts of carbon dioxide, water vapor, and other gasses make up remaining
Henry’s law
A gas will dissolve in a liquid in proportion to its partial pressure. Higher PP= more gas dissolves in liquid. Gasses dissolve in liquid best under high pressure, low temperature, and high solubility. Ex- carbonated beverages
Factors affecting rate at which gas exchange occurs between alveoli and capillaries (3)
- Partial pressure gradients and gas solubility
- Thickness and surface area of respiratory membrane
- Ventilation-perfusion coupling
How do partial pressure gradients and gas solubility affect rate of gas exchange?
PO2 in alveoli is greater than PO2 in capillaries- oxygen moves into alveoli and into the blood, while carbon dioxide moves in the opposite direction. Carbon dioxide diffuses at a slower rate than oxygen, but equal amounts are exchanged. This is because carbon dioxide is a more soluble gas than oxygen. Consider size of molecules in solubility- carbon dioxide is larger in size than oxygen, and therefore moves more slowly
How does thickness and surface area of respiratory membrane affect the rate of gas exchange?
The respiratory membrane is exceptionally thin- gas exchange occurs quickly. The greater the surface area, the greater amount of gas that can diffuse in a given amount of time. Surface area of the lungs is large, but alveolar surface area is huge. Ex- in a healthy male, alveolar surface area is 40-50X greater than the surface area of his skin
Ventilation-perfusion coupling
Optimal gas exchange results from equal amounts of gas reaching alveoli (via ventilation) and blood supply to pulmonary capillaries (via perfusion)
Perfusion
Flow of fluid through blood vessels
How does the partial pressure of oxygen influence perfusion (occurring at the lungs)?
If local PO2 is low- local arterioles to those alveoli constrict. Blood is redirected to respiratory areas with high PO2. Importance- ensures adequate oxygen uptake
If local PO2 is high- local arterioles to those alveoli dilate. Area is flooded with blood, takes up oxygen
How does the partial pressure of oxygen influence ventilation?
If local PCO2 levels are high, bronchioles dilate. Carbon dioxide is eliminated by the body faster. Importance- increased carbon dioxide affects blood pH and makes it more acidic. If local PCO2 levels are low, bronchioles constrict. If too low, blood becomes basic
Composition of alveolar gas
Atmospheric gasses mostly nitrogen and oxygen, but alveolar gasses are mostly carbon dioxide and water vapors
Why is the composition of atmospheric gasses and alveolar gasses different? (3)
- Gas exchange is occurring in alveoli- oxygen diffuses into blood, carbon dioxide diffuses into alveoli
- Conducting passages humidify air- creates water vapor
- Mixture of air in alveoli- inspiration brings in new gasses, but there is still gasses left over (reserve volume)
How is oxygen transported in the blood?
Oxygen transported primarily by hemoglobin (4 oxygen molecules per hemoglobin molecule)
How does hemoglobin work to bind oxygen?
Binding first oxygen molecule facilitates binding of other 3. Doesn’t take a lot of work, so oxygen binding can occur faster- as each oxygen binds, it’s easy for the next one to be added. Unloading first oxygen molecule facilitates unloading of remaining 3. Effect- loading and unloading of oxygen by hemoglobin is fast and efficient
What is the oxygen saturation of arterial blood?
Arterial blood is 98% saturated. Typically drops with health issues with the blood or the lungs. We always have a small amount of older and less efficient blood cells that won’t bind oxygen
What is the oxygen saturation of venous blood?
Venous blood is 75% saturated. This not 0% so we can have a venous reserve of oxygen- body can use it if needed. If ventilation decreases or you’re not exchanging enough air, you can use the venous reserve if needed
3 ways of transporting carbon dioxide
- Dissolved in plasma
- Bound to hemoglobin
- As bicarbonate ions (HCO3) in plasma
How does hemoglobin transport carbon dioxide?
Carbon dioxide does not bind heme, it binds amino acids of globulin. Importance- oxygen and carbon dioxide do not compete with one another for a “spot”. Deoxygenated hemoglobin binds carbon dioxide more readily than oxygenated hemoglobin
How does carbon dioxide form bicarbonate ions in plasma?
When carbon dioxide diffuses into erythrocyte- combines with water to form carbonic acid (H2CO3). Carbonic acid split to form hydrogen and bicarbonate ions (HCO3). This reaction is reversible- we don’t really do anything with bicarbonate, needs to be converted back to carbon dioxide
How can carbon dioxide change blood pH?
Conversion of carbon dioxide to bicarbonate causes release of hydrogen ions, which would decrease blood pH. Normally, this is buffered by red blood cells- maintains 7.35-7.45 pH of blood
An increase in carbon dioxide in the blood causes blood pH to
Decrease. Respiratory acidosis, caused by slow, shallow breathing
A decrease in carbon dioxide in the blood causes blood pH to
Increase. Respiratory alkalosis, caused by rapid, deep breathing
Which areas of the CNS control the respiratory system? (2)
- Medullary respiratory center- two areas that set the normal respiratory rhythm.
- Pontine respiratory center (PRC)
2 sets of neurons used by the medullary respiratory center?
- Ventral respiratory group (VRG)
2. Dorsal respiratory group (DRG)
Ventral respiratory group (VRG)
Part of medullary respiratory center. Some neurons in this group fire during inspiration, others fire during expiration- one set inhibits the other (they cannot fire at the same time). When the pressure in the lungs balances out, the inspiration neurons stop firing. During inspiration, impulses excite the diaphragm and external intercostals. During expiration, impulses stop and muscles relax
Dorsal respiratory group (DRG)
Part of medullary respiratory center, modifies rhythm set by VRG. Smooths out the respiratory pattern, makes sure the transition is smooth between inspiration and expiration. Integrates information from other structures (chemoreceptors, etc), delivers it to VRG
Pontine respiratory center (PRC)
Interact with medullary respiratory centers to “smooth” the respiratory pattern. Transition from inspiration to expiration (and vice versa)
Which 2 factors does the CNS measure to determine breathing rate and depth?
- Carbon dioxide is the most potent and most closely controlled
- PO2 of arterial blood
Hypercapnia
An increase in PCO2 levels in blood, causing respiratory acidosis. Depth and rate of breathing increase
Hypocapnia
A decrease in PCO2 levels in the blood, causing respiratory alkalosis.
How does PO2 affect ventilation?
PO2 must drop substantially to stimulate increased ventilation- therefore, carbon dioxide is most important in this situation. Venous reservoir of saturated hemoglobin (about 75%)- body can use this if PO2 drops slightly. If PO2 drops substantially, respiratory centers are stimulated. Ventilation increases- oxygen levels increase
Higher brain centers influencing respiration (2)
- Hypothalamic control
2. Cortical controls
Hypothalamic control
Strong emotion (excited increases RR, anger decreases RR), pain send information from hypothalamus/limbic system to respiratory centers (decreases RR). Ex- excitation stimulates respiratory rate, anger suppresses it, substantial drop in temperature can cause apnea
Cortical controls
We can override the respiratory centers to control our own breathing depth/rate. Cerebral motor cortex sends impulses to motor neurons that stimulate respiratory muscles. This only goes so far, since you can’t hold your breath forever. The respiratory centers will automatically initiate respiration due to rising carbon dioxide levels
Which activities require alteration of the normal pattern of respiration? (2)
- Exercise
2. High altitude
How does exercise change the pattern of respiration?
Adjustments are made based on intensity and duration of physical exertion. Active muscles need large amounts of oxygen and produce large amounts of carbon dioxide waste. Ventilation and perfusion during exercise are still balanced. Respiration increases at the beginning of exercise, then plateaus. This is most likely due to rate of carbon dioxide delivery to the lungs
Hyperpnea
Ventilation increases 10-20 times during exercise
Acute mountain sickness
If you move up in elevation fast, acute mountain sickness can occur. Symptoms- headache, shortness of breath, nausea, dizziness. Your body has no time to make an adjustment and you become short on oxygen
What adjustments are made during acclimatization? (3)
- Increased ventilation- decrease carbon dioxide in blood to “match” lower oxygen availability
- Lower hemoglobin saturation rates- less oxygen to bind hemoglobin. Arterial blood is less oxygen saturated compared to lower elevations, but the body still receives what it needs
- Kidneys produce more erythropoietin (EPO)- increase in erythrocyte production/number. Long term adaptation to high altitude living
How does high altitude change the pattern of respiration?
With increases in elevation, atmospheric pressure and PO2 drop. If you move up in elevation slowly, acclimatization occurs and the body makes respiratory and hematopoietic adjustments
Types of COPD (2)
- Emphysema
2. Chronic bronchitis
Chronic obstructive pulmonary disease (COPD)
Group of conditions characterized by a physiological inability to expel air from the lungs- makes normal ventilation difficult. This condition is irreversible. Features/shared characteristics- caused by smoking, labored breathing, coughing, pulmonary infection etc. Coughing can damage the alveoli and cause them to become infected
Emphysema
Permanent enlargement of the alveoli and eventual destruction of their walls. Lungs lose elasticity, and the accessory muscles used to enhance breathing. Bronchioles collapse during expiration- trap air in alveoli. Hyperinflation leads to “barrel chest”- diaphragm flattens. Damage to alveoli results in damage to pulmonary capillaries. Right side of heart has to work harder to move blood to the lungs- right ventricle enlarges and can lead to heart failure
Chronic bronchitis
Chronic production of excess mucus from inhaled irritants. Lower respiratory passages become inflamed over time and eventually fibrose, so ventilation decreases. This mucus is not removed from the lungs. Bacteria and microorganisms thrive in stagnant mucus, so infection is frequent
Asthma
Some similarities to COPD, but asthma is temporary bronchospasm attacks followed by symptom free periods. Allergic asthma is most common form- allergen causes inflammation of airways. Inflammation caused by IgE antibodies and persists between attacks- airways become hypersensitive. Subsequent attacks can be very severe
Asthma treatment
Treatment- inhaled corticosteroids, bronchodilators
Tuberculosis
Bacterial disease spreads (primarily) by inhaled air. Mostly affects lungs, but can spread to other organs- uses lymphatic system to transport. 33% of world population if infected, but it’s not active in most. When inactive, bacteria enters the lungs, but the immune system forms a wall around the bacteria. Forms hardened nodules in the lungs, so the bacteria can’t cause infection
Symptoms of active tuberculosis
If active, symptoms include fever, night sweats, weight loss, racking cough, and coughing up blood (due to lung damage from the cough). The immune system can’t trap the bacteria
Sleep apnea definition
Characterized by temporary cessation of breathing during sleep. People with sleep apnea wake themselves up due to this condition, can be as high as 30 times per hour. Constant fatigue usually results- increased susceptibility to hypertension, heart disease, stroke, etc. Also causes very loud snoring
Forms of sleep apnea (2)
- Obstructive sleep apnea
2. Central sleep apnea
Obstructive sleep apnea
Occurs when upper airways collapse. Muscles associated with pharynx release during sleep, and the airway sags and closes. Most common in men, made worse by obesity. Treatment- CPAP machine- blows air into passages constantly to prevent collapse of pharynx and trachea
Central sleep apnea
Respiratory centers of the brain “slack” during sleep- breathing rhythm/rate not maintained. Also controls heart rate and blood pressure, but these are mostly unaffected. Since the airways are still working, CPAP machines don’t help here
