The Respiratory System

Question 1

Describe the journey of air into the nose and through the lungs.

Answer 1

1. Air enters through the nares –> nasal cavity –> filtered by mucous membranes and nasal hairs (vibrissae)
2. Air passes into pharynx and larynx
3. Air goes from larynx to trachea, and then one of the two bronchi (trachea and bronchi are ciliated to catch non-air particles)
4. Bronchi divide into bronchioles and then alveoli in the lungs, lots of surface area
5. Capillaries around each alveolus carry O2 and CO2

Question 2

Where are the pharynx and larynx located? Describe features of the larynx.

Answer 2

• Pharynx: behind nasal cavity and at back of mouth; for air and food
• Larynx: below pharynx; only for air
• Larynx opening (glottis) covered by epiglottis during swallowing to keep food out of trachea
• Larynx has two vocal cords that are controlled by skeletal muscle

Question 3

What are alveoli coated in?

Answer 3

Surfactant, a detergent that lowers surface tension and keeps the alveolus from collapsing on itself

Question 4

What cavity are the lungs contained in, and what membranes surround them? What is between the membranes?

Answer 4

• Thoracic cavity
• Pleurae surround each lung - visceral pleura sticks to lung, parietal pleura to chest wall
• In between is intrapleural fluid, filled with fluid that lubricates

Question 5

What is the role of the diaphragm? Is it under autonomic or somatic control?

Answer 5

• Divides thoracic cavity and abdominal cavity
• Helps create negative pressure for lung expansion
• Breathing is under autonomic control, but diaphragm is under somatic

Question 6

Describe the process of inhalation. Is it active or passive? What muscles are used? What happens to intrapleural space volume and pressure?

Answer 6

Active process

• Diaphragm and external intercostal muscles expand thoracic cavity as diaphragm flattens
• Intrathoracic volume increases, meaning intrapleural space increases, meaning pressure decreases

Question 7

What happens to lungs during inhalation?

Answer 7

• The lungs are originally at atmospheric pressure, which is now higher than the pressure in the IP space
• So the lungs expand into the IP space, decreasing pressure in them
• Air will then be sucked in from a higher-pressure environment - the outside world

Question 8

Why is inhalation called negative-pressure breathing?

Answer 8

The driving force for the breathing is the lower (relatively negative) pressure in the IP space compared with the lungs

Question 9

Describe the process of exhalation. Is it active or passive?

Answer 9

Does not have to be active, can just relax intercostal muscles and diaphragm

• This will decrease chest volume, making IP volume decrease too, which will cause IP pressure to increase
• Now IP pressure is higher than atmospheric pressure in the lungs, so air will be pushed out

Question 10

How can exhalation be made active?

Answer 10

Using the internal intercostal muscles and abdominal muscles, which oppose the external intercostals and can pull the rib cage down, actively decreasing cavity volume

Question 11

What tool is used to measure lung capacities? What can’t it measure?

Answer 11

Spirometer

Can’t measure RV so can’t measure TLC

Question 12

What is the total lung capacity (TLC)?

Answer 12

The maximum volume of air in the lungs when one inhales completely (about 6-7 L)

Question 13

What is residual volume (RV)?

Answer 13

The volume of air remaining in the lungs when one exhales completely

Question 14

What is vital capacity (VC)?

Answer 14

The difference between the minimum and maximum volume of air in the lungs: TLC - RV

Question 15

What is tidal volume (TV)?

Answer 15

The volume of air inhaled or exhaled in a normal breath

Question 16

What is expiratory reserve volume (ERV)?

Answer 16

The volume of additional air that can be forcibly exhaled after a normal exhalation

Question 17

What is inspiratory reserve volume (IRV)?

Answer 17

The volume of additional air that can be forcibly inhaled after a normal inhalation

Question 18

What region in the brain regulates breathing, and how does it do it?

Answer 18

• Ventilation center, a collection of neurons in the medulla oblongata
• The neurons fire rhythmically to cause regular contraction of respiratory muscles
• They contain chemoreceptors that are very sensitive to CO2 concentration

Question 19

How does the ventilation center respond to too much CO2 in the blood? Too little oxygen?

Answer 19

• As partial pressure of CO2 in the blood rises (hypercarbia/capnia), the respiratory rate will increase so more CO2 leaves
• Respond to oxygen only during hypoxemia (low O2)

Question 20

What is the mathematical relationship between vital capacity, inspiratory reserve volume, expiratory reserve volume, and tidal volume?

Answer 20

VC = IRV + ERV + TV

Question 21

What do the capillaries around the alveoli bring? What do they take away?

Answer 21

• Receives deoxygenated blood from pulmonary arteries (from right ventricle)
• Sends oxygenated blood from pulmonary veins (to left atrium)

Question 22

How do capillaries engage in gas exchange with alveoli?

Answer 22

Pressure differential
-When blood arrives at alveoli, it has a relatively low partial pressure of O2 and relatively high partial pressure of CO2, so they transfer down their concentration gradients

Question 23

What would occur at high altitudes?

Answer 23

• Less O2 available
• Rapid breathing to avoid hypoxia
• Hemoglobin would change its binding abilities
• Body would make more RBCs
• Long term: body would make more blood vessels

Question 24

Describe the respiratory system’s role in thermoregulation. What structures specifically are used?

Answer 24

System is very vascular

• Vasodilation: capillaries expand, heat is lost
• Vasoconstriction: capillaries contract, heat is saved
• Nasal and tracheal capillaries are most frequently used within the system, but skin/muscles used mostly in humans

Question 25

What is the nasal cavity’s role in defense?

Answer 25

• Has small hairs (vibrissae) that help trap potentially dangerous things
• Contains lysozyme which can attack G+ bacteria walls
• Mucociliary escalator: lined with mucus that can trap invaders, and then cilia push it to oral cavity where it can be expelled or swallowed

Question 26

What are the lungs’ role in defense?

Answer 26

• Contain macrophages
• Mucosal surfaces have IgA antibodies that can help protect against invaders that touch the mucous membrane
• Have mast cells with antibodies

Question 27

What is the bicarbonate buffer system equation?

Answer 27

CO2(g) + H2O(l) H2CO3(aq) H+(aq) +HCO3-(aq)

Question 28

What occurs in the body if pH drops below 7.35-7.45?

Answer 28

Acidemia

• Acid-sensing chemoreceptors outside blood-brain barrier send signals to brain to increase respiratory rate
• An increased H+ concentration will cause a left shift in the equation, creating more CO2
• Brain receptors will sense the increased CO2 and promote an increase in respiratory rate
• This causes another shift left in the equation, lowering H+ concentration

Question 29

What occurs in the body if pH rises above 7.35-7.45?

Answer 29

Alkalemia

• Respiratory rate slowed so more CO2 is retained
• Causes right shit in equation and producing more H+

Question 30

Which other organs help lungs maintain blood pH?

Answer 30

Kidneys - modulate secretion and reabsorption of acid and base
-Much slower process