Respiratory System & Tissues Flashcards
Name three major functions of the respiratory system
- gas exchange
- filtration of particulate matter
- thermoregulation
Explain the relationship between gas exchange and cellular metabolism
- Aerobic cellular respiration requires oxygen and releases carbon dioxide as a waste product. Gas exchange removes this unwanted CO2 from the cells and replaces it with O2 from the environment
- Specifically, O2 is required for the electron transport chain, while CO2 is produced mainly during the Krebs cycle
List the structures of the respiratory tract in order, beginning at the entrance for incoming air and ending at the site of gas exchange
- nasal passage
- pharynx
- larynx
- trachea
- bronchi
- bronchioles
- alveoli
Lung
- the major organ in the respiratory system, acting to provide a site for gas exchange
- humans have two lungs that are connected to the outside environment via the respiratory tract
Larynx
- cartilagenous structure that contains the vocal cords
- sits directly below the pharynx and above the trachea
Pulmonary Alveoli
- In the lungs, alveoli are small sacs at the ends of bronchioles
- each alveolus is enclosed by an epithelial lining and surrounded by pulmonary capillaries
- alveoli are the site of gas exchange between the environment and the bloodstream
- oxygen moves from the alveoli to the capillaries, while carbon dioxide travels in the opposite direction
In which pulmonary structure(s) is the activity of surface tension most relevant?
- Surface tension, or the tendency of liquid molecules to associate with each other, is related to the alveoli
- Surface tension causes liquids to form spherical droplets, maximizing their contact with other liquid particles. Since the alveoli contain fluid, this property would tend to make alveoli collapse and is countered by the action of surfactant
What substance serves to decrease surface tension in the alveoli?
- Surfactant decreases surface tension and prevents the alveoli from collapsing
- Pulmonary surfactant is amphipathic, meaning that its molecules possess both hydrophobic and hydrophilic groups
Premature infants often suffer from respiratory distress syndrome, a condition that involves insufficient surfactant production. What effect will this condition likely have on the alveoli?
- It will cause the alveoli to collapse
- Surfactant serves to lower surface tension in the fluid associated with the alveolar lining
- Without surfactant, this fluid will tend to minimize its own surface area, collapsing into the hollow interior of the alveolus and making inhalation very difficult
What type of transport is used by gases to travel between alveoli and pulmonary capillaries?
- the gases travel via diffusion
- since gases are small and nonpolar, they are easily able to diffuse through cell membranes
- gas exchange is a passive process, meaning that oxygen and carbon dioxide move down their concentration gradients without using ATP
Compare the partial pressure of carbon dioxide in the pulmonary capillaries to that in the alveoli
- pulmonary capillaries have a higher partial pressure of CO2
- pulmonary capillaries bring deoxygenated blood, which is CO2-rich, in close contact with the alveoli
- if CO2 is to diffuse from the bloodstream to the alveolar interior, it must travel down its concentration gradient. The alveoli, then, must contain comparatively less carbon dioxide than the capillaries
Place the following terms in order according to their oxygen partial pressures, from the lowest PO2 to the highest:
- Alveolar air
- Atmospheric air
- Blood from the pulmonary artery
- blood from the pulmonary artery < alveolar air < atmospheric air
- pulmonary artery carries deoxygenated blood from the heart to the lungs, so it contains a comparatively low amount of O2. It’s easy to assume that the alveoli contain only atmospheric air, but they also hold residual carbon dioxide from the previous respiration, resulting in a slightly lower oxygen partial pressure than that of atmospheric air.
What are the steps involved in inspiration?
- diaphragm and external intercostal muscles contract, expanding the thoracic cavity
- lungs expand along with the surrounding cavity, lowering their internal pressure
- air flows from the comparatively high-pressure environment to the low-pressure lungs
What is the significance of the term “negative pressure breathing?”
- It describes the mechanism of inspiration. The pressure inside the lungs becomes lower than atmospheric pressure, causing air to flow inward.
- Negative pressure also relates to MCAT physics. Remember that absolute pressure can never have a negative value. Instead, it is the gauge pressure that is negative, meaning simply that it is lower than ambient pressure.
Name the main muscles involved in inspiration
- Inspiration involves both the diaphragm and the external intercostals
- Both muscles contract to enlarge the thoracic cavity. The diaphragm flattens downward, while the external intercostals push outward.
The diaphragm is composed of which of the three types of muscle?
- diaphragm consists of skeletal muscle.
- For the MCAT, skeletal muscle can usually be considered to be voluntary. The diaphragm is a notable exception, since it can be consciously contracted but is usually under involuntary control.
Name the main muscles involved in expiration
Normal expiration is passive, requiring no muscular involvement. Expiration that is consciously forced involves the internal intercostals.
During exhalation, the diaphragm must be in which state?
- diaphragm must be relaxed.
- When relaxed, the diaphragm becomes rounded, pushing upward and decreasing the volume of the thoracic cavity. Lower volume results in increased pressure, forcing air outward.
What measurement describes the volume of air inhaled per breath during normal breathing?
- Tidal volume
- tidal volume of an average human is approximately 500 mL
What is the difference between inspiratory and expiratory reserve volume?
- Inspiratory reserve volume (IRV) refers to the maximum volume of air that can be inhaled in addition to a normal inhalation
- Expiratory reserve volume (ERV) refers to the maximum volume that can be exhaled in addition to a normal exhalation
The sum of IRV, ERV, and tidal volume can be described by which lung measurement?
- IRV, ERV, and tidal volume combine to form the lungs’ vital capacity
- Vital capacity is the largest volume that can possibly be inhaled or exhaled
What measurement describes the volume of air that always remains in the lungs, regardless of the force of exhalation?
Residual volume
-this volume never leaves the lungs so it cannot be directly measured but can be calculated using other lung volumes
What is the difference between total lung capacity and vital capacity? What is the difference between total lung capacity and vital capacity?
- Total Lung Capacity (TLC) includes the entire volume of air that can be held in the lungs; it is equal to the sum of vital capacity and residual volume
- Vital Capacity (VC) only includes the volume that can be inhaled or exhaled
If inspiratory reserve volume and tidal volume are known, what additional measurements are needed to calculate residual volume?
Total Lung Capacity and Expiratory Reserve Volume
-ERV, IRV, and TV can be added to find vital capacity; from there residual volume can be found by subtracting VC from TLC
Which substance, secreted by membranes in the nasal passages, helps protect the lungs from foreign particles?
this protective substance is mucus
-in the respiratory tract, mucus functions as part of the innate immune system; these membranes also exist in the stomach
Which organelle associated with respiratory epithelium would be seriously impaired by the inhibition of microtubule synthesis?
Cilia
- these are small hairlike organelles that line much of the respiratory tract and are composed of microtubules
- these function to protect the lungs by moving mucus and particles toward the throat
Which type of immune cell is highly active in the alveoli of the lungs?
Macrophages
-specialized cells known as alveolar macrophages are present only in the lungs and can perform phagocytosis and release factors that activate other immune cells when exposed to a pathogen
Hypoxia
-the condition of oxygen deprivation usually due to low oxygen levels in the blood
What homeostatic system relates to the equation below?
H2O + CO2 ⇔ H2CO3 ⇔ H+ + HCO3-
Bicarbonate Buffer
-this is the main homeostatic method of maintaining constant pH in the blood
In the first step of the bicarbonate buffer, dissolved carbon dioxide reacts with water in the plasma. Which acid is produced by this reaction?
Carbonic Acid (H2CO3) -the conjugate base of this is bicarbonate (HCO3-)
How does the respiratory system respond to low blood pH levels?
Increased respiratory rate
-acidic blood has a high proton concentration which will shift the bicarbonate buffer equation to the left to regain equilibrium ( H2O + CO2 ⇔ H2CO3 ⇔ H+ + HCO3- ) which results in the production of water and CO2; to excrete this additional CO2 the breathing rate must increase
Rapid or excessive breathing, commonly known as hyperventilation, results in an abnormally high rate of CO2 exhalation. What condition can be caused by prolonged hyperventilation?
High Blood pH (Alkalosis)
-when respiratory rate is increased above normal levels, more CO2 will be exhaled than usual and the bicarbonate buffer equilibrium will shift away from the production of hydrogen ions which means the blood will be more basic/alkaline
What factor does blood pH depend most on?
CO2 concentration
If a normal individual suddenly began inhaling air with a significantly higher partial pressure of O2, what immediate effect would this have on her plasma pH?
(Assume that her rates of respiration, carbon dioxide exhalation, and carbon dioxide production remain unchanged.)
Plasma pH would not be affected
- while blood pH depends directly on CO2 concentration, its relationship with O2 levels is much more indirect
- Oxygen is not part of the bicarbonate buffer system so if all else remained the same it would have no immediate effect on pH
