Respiratory Physiology (Day 1)

Question 1

Ventilation (breathing)

Answer 1

mechanical process that moves air into and out of the lungs

Question 2

Where does gas exchange occur?

Answer 2

between blood and lungs

between blood and tissues

Question 3

Cellular Respiration

Answer 3

oxygen utilization by tissues to make ATP

Question 4

External respiration

Answer 4

ventilation and gas exchange in lungs

Question 5

Internal respiration

Answer 5

oxygen utilization and gas exchange in tissues

Question 6

Gas Exchange in Lungs

Answer 6

Occurs via diffusion

O2 concentration is higher in the lungs than in the blood, so O2 diffuses into blood.

CO2 concentration in the blood is higher than in the lungs, so CO2 diffuses out of blood.

Question 7

Respiratory System Functions

Answer 7

GAS EXCHANGE between the atmosphere and the blood—brings in O2, eliminates CO2

Homeostatic REGULATION OF BODY PH—via selective retention vs excretion of CO2

PROTECTION from inhaled pathogens and irritating substances—via trapping & either expulsion or phagocytic destruction of potentially harmful substances, pathogens

VOCALIZATION—vibrations created by air passing over vocal cords

Question 8

Conduction Zone

Answer 8

–>gets air to respiratory zone

trachea
primary bronchus
terminal bronchioles

Question 9

Respiratory Zone

Answer 9

–> site of gas exchange

respiratory bronchioles
alveolar sacs
alveolus

Question 10

What is the passage of inspired air?

Answer 10

nasal cavity

pharynx

larynx (through glottis and vocal cords)

trachea

R/L primary bronchi

Secondary bronchi

more branching

terminal bronchioles

respiratory zone (respiratory bronchioles)

terminal alveolar sacs

Question 11

What does mucus do?

Answer 11

traps small particles

Question 12

What do cilia do?

Answer 12

move small particles away from lungs by mucus

Question 13

What is the structure of a lung lobule?

Answer 13

Each cluster of alveoli is surrounded by elastic fibers and a network of capillaries

Question 14

Alveoli

Answer 14

Air sacs where gas exchange occurs

300 x 10^6 ; provide large surface area (760 ft^2) to increase diffusion rate

Each alveolus: one-cell layer thick

Form clusters at the ends of respiratory bronchioles

Question 15

What are the two types of alveolar epithelial cells?

Answer 15

Type I: 95−97% total surface area where gas exchange occurs

Type II: secrete pulmonary surfactant and reabsorb sodium and water, preventing fluid buildup

Question 16

Thoracic Cavity

Answer 16

• Contains the heart, trachea, esophagus, and thymus within the central mediastinum
• -> The lungs fill the rest of the cavity.

Question 17

Pleura

Answer 17

parietal pleura: lines thoracic wall

visceral pleura: covers the lungs

normally pushed together, with a fluid-filled space between called the intrapleural space (pleural cavity).

Question 18

diaphragm

Answer 18

a dome-shaped skeletal muscle of respiration that separates the thoracic and abdominal cavities

Question 19

Physical aspects of ventilation

Answer 19

Air moves from higher to lower pressure.

Pressure differences between the two ends of the conducting zone occur due to changing lung volumes.

Compliance, elasticity, and surface tension are important physical properties of the lungs.

Question 20

What are the types of pressure?

Answer 20

1. Atmospheric pressure: pressure of air outside the body
2. Intrapulmonary or intraalveolar pressure: pressure in the lungs
3. Intrapleural pressure: pressure within the intrapleural space (between parietal and visceral pleura); contains thin layer of fluid to serve as a lubricant

Question 21

Pressure differences when breathing

Answer 21

1. Inspiration (inhalation): Intrapulmonary pressure Pressure atmospheric pressure (generally about +3mmHg)

Question 22

Intrapleural Pressure

Answer 22

LESS than P(intrapulmonary) and P(atmospheric) in both inspiration and expiration

P(intrapulmonary) - P(intrapleural) = P(transpulmonary)

Keeps lungs against thoracic wall, allowing lungs to expand during inspiration

Question 23

Pneumothorax

Answer 23

If the sealed pleural cavity is opened to the atmosphere, air flows in. The bond holding the lung to the chest wall is broken, and the lung collapses, creating a pneumothorax
(air in the thorax).

Question 24

Boyle’s Law

Answer 24

↑ lung volume during inspiration ↓’s P(intrapulmonary) to  Air flows in.

↓ lung volume during expiration  –> P(intrapulmonary) > P(atmospheric) –> Air flows out.

Question 25

Lung compliance

Answer 25

Lungs expand when stretched.

Defined as change in lung volume per change in transpulmonary pressure: ΔV/ΔP

Index of the ease with which the lungs expand under pressure—> high compliance: easily stretched
–> low compliance: requires more force, restrictive lung diseases (e.g. pulmonary fibrosis, surfactant deficiency)

Question 26

Lung elasticity

Answer 26

Return to initial size after being stretched (recoil)

Lungs have elastin fibers.

Because the lungs are stuck to the thoracic wall, they are always under elastic tension.

Tension increases during inspiration and is reduced by elastic recoil during expiration.

Question 27

Surface Tension

Answer 27

“force holding fluid molecules together in an air-fluid interface… due to strong attractive force of H bonds between H2O molecules”

Resists distension, promotes collapse of alveolar space

Exerted by fluid secreted on the alveoli

Fluid is absorbed by active transport of Na+ and secreted by active transport of Cl-
–> any imbalance between these can result in viscous fluid that is difficult to clear –> raises the pressure of the alveolar air as it acts to collapse the alveolus

Ex. People with cystic fibrosis have a genetic defect that causes such an imbalance of fluid absorption and secretion

Question 28

Law of Laplace

Answer 28

Pressure is DIRECTLY proportional to surface tension and INVERSELY proportional to radius of alveolus.

Small alveoli would be at greater risk of collapse without surfactant.

Question 29

Surfactant

Answer 29

SURFACE ACTIVE AGENT

Secreted by type II alveolar cells

Consists of hydrophobic protein and phospholipids

REDUCES surface tension between water molecules by reducing the number of hydrogen bonds between water molecules

More concentrated as alveoli get smaller during expiration to equalize pressure.

Prevents collapse

Allows a residual volume of air to remain in lungs

Question 30

Respiratory Distress Syndrome

Answer 30

Production of surfactant begins late in fetal life, so premature babies have higher risk for alveolar collapse–respiratory distress syndrome (RDS)
–> treated with surfactant

Similar problem may occur in adults with septic shock
–↓ lung compliance, ↓ surfactant—acute respiratory distress syndrome (ARDS); NOT treatable with surfactant

Question 31

Muscles of Inspiration: Sternocleidomastoid, Scalenes

Answer 31

used for forced inspiration

Question 32

Muscles of Inspiration: External Intercostals

Answer 32

raises rib cage during inspiration

Question 33

Muscles of Inspiration: Parasternal intercostals

Answer 33

works w/external intercostals

Question 34

Muscles of Inspiration: Diaphragm

Answer 34

contracts in inspiration - lowers –> enlarging thoracic cavity

relaxes in expiration - raises –> thoracic cavity smaller

Question 35

Muscles of Expiration: Internal Intercostals

Answer 35

lowers rib cage during forced expiration

Question 36

Muscles of Expiration: External Abdominal Obliques, Internal Abdominal Oblique, Transversus Abdominus, Rectus Abdominus

Answer 36

abdoominal muscles are also used in forced expiration

Question 37

Quiet Expiration

Answer 37

occurs with the relaxation of the inspiratory muscles (PASSIVE)

Question 38

Inspiration

Answer 38

Volume of thoracic cavity (and lungs) increases vertically when diaphragm contracts (flattens) and laterally when parasternal and external intercostals raise the ribs.

–Thoracic & lung volume increase –> intrapulmonary pressure decreases –> air in

–occurs when alveolar pressure decreases

1. thoracic cage expands outwards
2. diaphragm drops down- contracts and flattens
   - -> both of these lead to increased thoracic volume and decreased thoracic (alveolar) pressure

Question 39

Expiration

Answer 39

Volume of thoracic cavity (and lungs) decreases vertically when diaphragm relaxes (dome) and laterally when external and parasternal intercostals relax for quiet expiration or internal intercostals contract in forced expiration to lower the ribs.

–Thoracic & lung volume decrease –> intrapulmonary pressure increases –> air out

Question 40

Regulation of Ventilation

Answer 40

Unlike cardiac muscle, skeletal muscles are NOT spontaneously active, so they must be stimulated by nerve signals.

Rhythmic pattern of contraction & relaxation of breathing muscles arises from a neural network of spontaneously discharging motor neurons from:

1. CEREBRAL CORTEX (voluntary breathing)
2. MEDULLA OBLONGATA and PONS (Involuntary breathing)

Motor neurons– innervate diaphragm/other breathing muscles; regulated by descending neurons from the brainstem (Medulla & Pons).

Question 41

Control of Breathing: Medulla

Answer 41

Two rhythmicity centers: excitatory inspiratory neurons vs neurons which inhibit those inspiratory neurons—intrinsic rhythmicity, but influenced by other factors.

1) Involuntary breathing (e.g. at rest)
- intrinsic to medulla
2) Voluntary (“forced,” e.g. exercise)
- input from cerebral cortex

Question 42

Control of Breathing: Pons

Answer 42

Two resp control centers:

1) apneustic (stimulates inspiratory neurons in medulla)
2) pneumotaxic (antagonizes apneustic to inhibit inspiration)