PHYSIOLOGY 001 - Chapter 16: Respiratory System
What is atmospheric pressure?
(760mmHg) the pressure exerted by the weight of air/gas in the atmosphere (outside) that drives respiration
What is the pathway of air?
(the way air goes in, is the same way air goes out) oxygen-rich air from the environment → nasal cavities → pharynx → trachea → bronchi → bronchioles → alveoli → bronchioles → bronchi → trachea → pharynx → nasal cavities → carbon dioxide-rich air to the environment
What is acidosis and alkalosis?
- Acidosis: pH below 7.35 (acidic), when there are high levels of CO2 and H+ and low levels of O2 - Alkalosis: pH above 7.45 (basic), when there are low levels of CO2 and H+ and high levels of O2
How is CO2 unloaded from the RBCs/blood to the alveoli?
- CO2 dissolved in plasma diffuses into the alveoli - Carbaminohemoglobin (HbCO2) dissociates and releases CO2 which diffuses into the alveoli - HCO3- diffuses back into RBCs in exchange for Cl- (reverse chloride shift), and through the reaction HCO3- + H+ --> H2CO3 --> H2O + CO2, the free CO2 diffuses into the alveoli (to be exhaled)
What is squamous cell carcinoma?
- Cancer cells invade bronchial walls and cause bleeding lesions (often presented with coughing up blood) - Additionally, keratin replaces respiratory tissue, making them fibrotic - Tumor cells then invade bronchial walls and compress airways, leading to potential atelectasis (lung collapse) - By the time of diagnosis, rapid metastasis (spread of cancer cells) occurs, potentially spreading to the heart (pericardium), bones, liver, and brain
What are the 2 divisions of the respiratory system?
- Conductive division: only the passage of air from the nose to the bronchioles - Respiratory division: exchange of gasses, O2 and CO2, between the alveoli and capillaries
What is chronic bronchitis?
- Exposure to irritants in the airway causes inflammation and hyperplasia (increased cell division) of the bronchial mucosa - As a result, cilia are immobilized and reduce in number, and goblet cells enlarge and produce excess mucus - The excess mucus accumulates due to immobilized cilia and becomes sputum - Sputum provides ideal bacterial growth which impairs alveolar macrophages - Leading to chronic infection and bronchial inflammation
What is emphysema?
- Exposure to irritants leads to the breakdown of alveolar walls and results in larger but fewer alveoli which reduces the respiratory membrane for gas exchange to occur - Additionally, the lungs become fibrotic and less elastic and air passages collapse which obstruct air outflow and trap air - Lastly, thoracic muscles weaken and demand 3 to 4 times more energy to breathe
How does COVID-19 destroy Type II cells?
- Infected/damaged Type II cells release cytokines (IL-1,IL-6,TnF-α) to recruit macrophages and neutrophils to destroy viruses, but neutrophil-released proteases damages Type I and Type II cells - Macrophages release more cytokines (cytokine storm) that causes vasodilation which increases permeability of the capillaries and accumulates fluid in the alveoli (alveolar edema) - This fluid build-up dilutes surfactant, and hence, increases surface tension, causing alveoli to collapse, decreasing gas exchange and creating sensations of shortness of breath - High concentration of cytokines also signals the hypothalamus to increase body temperature, causing fever through prostaglandin release from ILs
What is the structure of coronaviruses?
- Nucleocapsid protein (N): bound to RNA genome - Spike protein (S): binds to host cell receptors to enter and hence infect host cells - Envelope protein (E): with M, helps form the viral envelope - Membrane protein (M): organises the assembly of COVID and determines the shape of the viral envelope
How is O2 unloaded from the RBCs/blood to the cells/tissue?
- O2 dissolved in plasma diffuses into the cells/tissue - Oxyhemoglobin (HbO2) dissociates and releases O2 which diffuses into the cells/tissue, in which the free Hb binds to H+ and forms deoxyhemoglobin (HHb)
What are the pleura (layer/membrane) of the lungs?
- Parietal pleura: outer membrane that attaches to the inner surface of the thoracic cavity - Visceral pleura: inner membrane that covers the external lung surface
What muscles are used in relaxed and forced exhalation/expiration?
- Relaxed: no muscles contract as the diaphragm and external intercostals relax and passively recoil back to their original shape - Forced: internal intercostals and abdominal muscles contract to force more air out the lungs
What muscles are used in relaxed and forced inhalation/inspiration?
- Relaxed: the diaphragm contract to flatten and external intercostals contract to expand the rib cage for the lungs to inflate - Forced: accessory neck muscles (scalenes, sternocleidomastoid) and external intercostals contract to force more air into the lungs
What's the difference between the right and left lung?
- Right lung: shorter wth 3 lobes (superior, middle, and inferior, separated by a horizontal and oblique fissure) due to the liver - Left lung: taller/narrower with 2 lobes (superior and inferior separated by a oblique fissure) due to the heart
What are the functions of the respiratory system?
- Ventilation (breathing) - O2 and CO2 exchange between blood and air - Speech and vocalization - Sense of olfaction (smell) - Affects pH levels of body fluids by eliminating (exhaling) CO2 - Breathing promotes the flow of lymph and venous blood
How is CO2 transported as bicarbonate ion?
- When CO2 diffuses into RBCs, it forms carbonic acid (H2CO3) through the reaction CO2 + H2O --> H2CO3 (which also occurs in plasma, but slower) - H2CO3 dissociates through the reaction H2CO3 --> HCO3- + H+ into bicarbonate ion (HCO3-) - HCO3- exits RBCs while Cl- enters through an anion exchanger (antiporter) in a process called chloride shift - HCO3- then travels in the plasma to reach the alveoli
How is CO2 loaded from the cells/tissue to the RBCs (/transported by blood)?
CO2 is dissolved in plasma and travels in the blood or is transported as carbaminohemoglobin or (primarily) as bicarbonate ion
What happens when COVID-19 infects a cell?
COVID-19 attaches its S-spike proteins to ACE-2 receptor on Type II alveolar cells, and uses the host cell machinery to insert its viral RNA and make its viral proteins via mRNa and ribosomes, leading to the production of new viruses released from the host cell which also damages the cell in the process
What is Boyle's Law?
The inverse relationship between volume and pressure, as: - When the volume of a gas increases, gas molecules have more space to move around and collide less, hence decreasing pressure - When the volume of a gas decreases, gas molecules have less space to move around and collide more, hence increasing pressure
What is the bronchial tree?
a branching system of tubes that conduct air to each lung
What is a spirometer?
a device that recaptures expired breath and records variables such as rate and depth of breathing, speed of expiration, lung capacity, and rate of oxygen consumption (overall condition of the lungs)
What does the respiratory system consist of?
a system of tubes that delivers air to the lungs to facilitate the diffusion of O2 into the blood and CO2 out of the blood
What is compliance?
ability of the lungs and alveoli to stretch and expand (distensible) during respiration
What is tachypnea?
accelerated, rapid, and shallow breathing often associated with hyperventilation
What is residual volume (RV)?
air remaining in lungs after maximum exhalation (ERV)
What are dust cells?
alveolar macrophages that keep the alveoli free from debris by phagocytizing inhaled dust particles
What is functional residual capacity (FVC)?
amount of air remaining in lungs after a normal tidal exhalation (ERV + RV)
What is ACE-2 receptor?
an enzyme attached to the surface of Type II alveolar cells that (lowers BP and) serves as an entry point for viruses like COVID-19
What is carbonic anhydrase?
an enzyme in RBCs that allow for rapid interconversion of CO2 and H2O to H2CO3 to HCO3- and H+
What does the future hold for COVID-19?
antiviral drugs, vaccines, blood plasma transfers, and immune suppresant drugs are being research to develop potential treatments for SARS-CoV-2, the virus that causes COVID-19
What causes deoxyhemoglobin (HHb) to dissociate?
as Hb binds to O2, its affinity for H+ decreases, causing HHb to dissociate and release H+ which will bind to HCO3-
What is cyanosis?
blue discoloration of the skin due to lack of oxygen (a symptom of chronic bronchitis)
What is respiration?
breathing, the cycle of inhalation and exhalation
What are the characteristics of the lungs?
compliance, elasticity, surface tension
What is Kussmaul respiration?
deep, rapid breathing often induced by acidosis (low pH) as the body is trying to restore pH levels, as this is commonly seen in people with Type I Diabetes (ketone bodies)
What are chemoreceptors?
detects and responds to changes in concentrations of H+, CO2, and O2 in blood to monitor pH
What are cortical controls?
direct signals from the cerebral motor cortex that bypass medullary controls to control voluntary breathing, like when taking a deep breath or holding in your breath
What is the DRG?
dorsal respiratory group of neurons in the medulla that receives input from peripheral stretch and chemoreceptors via CN XI, X and regulates the VRG
How does pulmonary surfactant reduce surface tension, and ultimately, prevent the alveoli from collapsing?
due to surfactant's amphiphilic nature, its hydrophilic head attaches to the thin layer of water that lines the alveoli while its hydrophobic tails face the air, this forms a barrier between water and air which disrupts the attractive force between water molecules, hence keeping the alveoli open
What are the variations in respiratory rhythm?
eupnea, apnea, dyspnea, hyperpnea, tachypnea, kussmaul respiration, respiratory arrest
What are coronaviruses, and some types?
family of large, enveloped RNA viruses characterized by their spiky surface proteins that can cause respiratory illnesses, and includes SARS, MERS, COVID-19
What is hyperventilation?
fast and deep breaths, when you inhale more air than your body needs and exhale too much CO2
What is the pleural cavity?
fluid-filled space between the pleura that reduces friction to prevent damage during lung inflation (inhalation) and creates a pressure gradient to facilitate breathing
What is hypercapnia, and it's negative feedback loop?
high blood CO2 levels due to hypoventilation, leading to increased partial pressure of CO2, H+, and thus, decreased pH (acidosis) in which chemoreceptors detect this imbalance and respond by increasing ventilation to restore pH levels
What is elasticity?
high content of elastic proteins that allows the lungs and alveoli to return to its initial size (recoil) after distension
What is hyperpnea?
increased rate and depth of breathing in response to exercise, pain, or other conditions
What is the inflation reflex?
inhibtory signals from stretch receptors are sent to the medullary inspiration center to prevent overexpansion of the lungs by ending inhalation when the lungs are too inflated with air to allow for exhalation
Why do you breathe in a paper bag when hyperventilating?
it allows you to rebreathe some of the CO2 that you exhaled, as this can help restore pH levels
What is dyspnea?
labored (painful) or gasping breathing, creating a sensation of shortness of breath due to heart disease or asthma
What is hypoxia?
low O2 levels in the cells/tissue (a symptom of chronic bronchitis)
What is hypocapnia, and it's negative feedback loop?
low blood CO2 levels due to hyperventilation, leading to decreased partial pressure of CO2, H+, and thus, increased pH (alkalosis) in which chemoreceptors detect this imbalance and respond by decreasing ventilation to restore pH levels
What is inspiratory capacity?
maximum amount of air that can be inhaled after a normal tidal exhalation (TV + IRV)
What is total lung capacity (TLC)?
maximum amount of air the lungs can contain (RV + VC)
Which part of the brain controls unconscious breathing?
medulla oblongata and pons
What is ventilation?
movement of O2 in and CO2 out the lungs (one inhalation and one exhalation)
What are the organs of the upper respiratory tract?
nose (breathes in air), pharynx (where air enters), larynx (voice box)
What is respiratory arrest?
permanent cessation or absence of breathing
What is pulmonary surfactant?
phospholipids that coats the alveoli and prevents them from collapsing when exhaling by reducing surface tension inside the alveoli
What is the PRG?
pontine respiratory group of neurons in the pons that fine tunes breathing rhythms and sends signals to the DRG and VRG
The flow of air in and out the lungs depends on what?
pressure difference between air pressure inside the lungs and outside the body, as air flows from higher pressure to lower pressure
Where did SARS, MERS, and COVID-19 come from?
primarily from bats passed to an intermediate host then to humans
What does COVID-19 do to your body?
protein-rich fluid (alveolar edema) can enter the bloodstream, travel to other places in the body, and cause systemic inflammatory response syndrome (SIRS) which can lead to kidney, liver, or heart failure and progress towards septic shock (systemic infection), and potentially, death
What are peripheral chemoreceptors?
receptors found in the aortic arch that detect O2 and CO2 levels, and in the internal carotid that also detect O2 and CO2 levels, along with pH levels
What are irritant receptors?
receptors found in the bronchus, trachea, and lungs that respond to irritants such as dust or smoke by decreasing respiration and promoting reflexive constrictions of air passages to prevent breathing in irritants
What are central chemoreceptors?
receptors found in the medulla oblongata that are sensitive to hypercapnic hypoxia and detects pH of CSF
What is eupnea?
relaxed quiet breathing (TV = 500 mL and respiratory rate is 12-15 bpm)
What are Type II alveolar (pneumocytes) cells?
repair the alveolar epithelium when Type I cells are damaged by differentiating and giving rise to new Type I cells and also secrete pulmonary surfactant
What other organ system is associated with respiratory system?
respiratory and cardiovascular systems, considered jointly as the cardiopulmonary system, work together to deliver O2 to and remove CO2 from the cells/tissue
What are Type I alveolar cells?
simple squamous cells that allow for rapid diffusion of O2 and CO2 between alveolus and bloodstream (capillaries)
What is hypoventilation?
slow/fast and shallow breaths, when you inhale less air than your body needs and exhale less CO2
What is apnea?
temporary cessation or absence of breathing (like when sleeping)
What is expiratory reserve volume (ERV)?
the amount of air after tidal volume that can be exhaled with maximum effort (forced exhalation)
What is inspiratory reserve volume (IRV)?
the amount of air after tidal volume that can be inhaled with maximum effort (forced inhalation)
What is partial pressure?
the amount of force each gas exerts in a mixture
What is surface tension?
the attractive force between water molecules (H2O) that resist distension and can cause the alveoli to shrink and collapse
What is chronic obstructive pulmonary disorder (COPD)?
the combination of chronic bronchitis and emphysema when there is damage to the alveoli and bronchi, making it harder to breathe due to risk factors like smoking, air pollution, or occupational exposure to airborne irritants (smoke, toxins, and chemicals)
What causes oxyhemoglobin (HbO2) to dissociate?
the high concentration of CO2 in the cells/tissue lowers pH, which decreases the affinity of hemoglobin for O2, causing HbO2 to dissociate and release O2
What is pulmonary gas exchange?
the loading of O2 from the alveoli to the RBCs and the unloading of CO2 from the RBCs to the alveoli
What is spirometry?
the measurement of pulmonary function that aids in diagnosis and assessment of restrictive and obstructive lung disorders
What is the hilum?
the slit through which the lung receives the main bronchus, blood vessels (pulmonary arteries and veins), lymphatics, and nerves
What is systemic gas exchange?
the unloading of O2 from the RBCs to the cells/tissue and the loading of CO2 from the cells/tissue to the RBCs
What happens to the volume and pressure of the lungs when you exhale?
the volume of the lungs decrease (recoil) and partial pressure inside the lungs increases (763mmHg) and is higher compared to the atmospheric pressure (760mmHg), causing air to move outside the lungs
What happens to the volume and pressure of the lungs when you inhale?
the volume of the lungs increases (expand) and partial pressure inside the lungs decreases (758mmHg) and is lower compared to the atmospheric pressure (760mmHg), causing air to move inside the lungs
What are obstructive disorders?
those that interfere with airflow by narrowing or blocking the airway, making it harder to inhale or exhale a given amount of air as this includes diseases like asthma and chronic bronchitis
What are restrictive disorders?
those that reduce pulmonary compliance, limitting the amount to which the lungs can be inflated, as this includes any disease, like black-lung and tuberculosis, that produces pulmonary fibrosis
What are the respiratory volumes and capacities?
tidal volume (TV), inspiratory reserve volume (IRV), expiratory reserve volume (ERV), residual volume (RV), inspiratory capactiy, functional residual capacity, vital capacity, total lung capacity
What is the alveoli?
tiny air sacs in the lungs that are the sites of gas exchange, in which O2 from the alveoli diffuses into RBCs while CO2 from RBCs diffuses into the alveoli to be exhaled
Why does each lung have so many alveoli (150 million)?
to give a large surface area for gas exchange (O2 and CO2) to occur
Why do we need to the breathe?
to take in O2 which is necessary for the synthesis of ATP, the fuel for all cellular processes and to eliminate CO2, the waste product of all cellular processes
What is vital capacity (VC)?
total amount of air that can be exhaled after inhalation with maximum effort (IRV + TV + ERV)
What are the organs of the lower respiratory tract?
trachea (cartilaginous tube), bronchi (bifurcates), lungs/alveoli (where gas exchange occurs)
What is the bronchial tree composed of?
trachea bifurcates into the primary bronchi and divides into smaller branches called bronchioles when it enters the lungs, which divide into terminal bronchioles which divide into respiratory bronchioles which connect to the alveoli/aveolar sac
What is the VRG?
ventral respiratory group of (inspiratory and expiratory) neurons in the medulla responsible for normal respiratory breathing rate (12-15 bpm) and exciting/inhibiting inspiratory muscles like the diaphragm via phrenic and intercostal nerves to contract/relax when breathing
What is tidal volume (TV)?
volume of air inhaled and exhaled in one cycle during quiet, resting breathing (500 mL)
How is CO2 transported as carbaminohemoglobin?
when HbO2 dissociates and releases O2, CO2 binds to the free Hb and forms carbaminohemoglobin (HbCo2)
What is the role of peripherial and central chemoreceptors in the respiratory system?
when O2 levels are low but CO2 levels are high, chemoreceptors send signals to the PRG to increase respiration to get rid of CO2 and take in more O2
How is O2 loaded from the alveoli to the RBCs?
when deoxyhemoglobin (HHb) dissociates and releases H+, O2 binds to the free Hb and forms oxyhemoglobin (HbO2)
What is pulmonary fibrosis?
when the lungs (alveoli) become scarred and stiff, making it difficult to breathe
