Pulmonary 1: Functional Anatomy of the Respiratory System

Question 1

Draw a diagram of the respiratory system. Include arterial and venous PaO2/PaCO2 and PvO2 and PvCO2 levels. Describe the 5 basic steps starting with Step 1: Exchange of air in the lungs.

Which step is internal respiration? Which step is external respiration?

Answer 1

1. Exchange of air in the lungs
2. O2 and CO2 are exchanged in alveoli
3. O2 and CO2 are transported in blood
4. O2 and CO2 are exchanged with cells
5. Mitochondria consume O2 and produce CO2

Step 5 is termed internal respiration.
Step 1 (external respiration) and step 2 
are accomplished by the respiratory system

Question 2

Describe the function of the respiratory system. What are the barrier, immune, and metabolic functions?

Answer 2

Gas exchange is the function… O2 in, CO2 out

barrier function- mucocilliary clearance

metabolic function- angiotensin I, serotonin

host defense- immune functions

Question 3

Describe the structure/anatomy of the upper and lower airways.

Describe the portion of resistance to airflow in the nose.

Why doesn’t the trachea collapse when pressure outside is greatly increased?

Answer 3

upper: nose, pharynx, glottis, vocal cords
lower: trachea, bronchial tree, alveoli

(terminal bronchiole, respiratory bronchiole, alveolar sac)

Resistance to airflow in the nose - 50 % of total air flow resistance

trachea -constructed of cartilaginous rings. these rings prevent trachea from collapsing when pressure outside it is greatly increased (like during cough)
posterior part of trachea is membranous and there is some invagination of posterior part when pressure is increased

Question 4

What is the carina?

Answer 4

bifurcation of trachea into R and L main stem bronchus.

Question 5

Describe/draw the differences between the airway walls in the trachea/bronchus to bronchiolus to alveolus.

Answer 5

Slide 16.
trachea/bronchus- mucus/surfactant, epithelium, basement membrane (lamina propia), smooth muscle layer, gland, cartilage, fibro-cartilaginous layer, capillaries

bronchiolus- less endothelium, less smooth muscle, basement membrane, fibro-cartilaginous layer, capillaries

alveolus- capillary, surfactant, type I endothelial cell, Type II endothelial cell, intraaveolar septum.

Question 6

Describe the conducting zone of the airway wall. For each component give the number, whether or not has cilia, smooth muscle, or cartilage.

Which is the only component of the conducting zone that does not have cartilage?

Answer 6

trachea- 1, has cilia and smooth muscle and cartilage

bronchi- 2,4,8 - has cilia and smooth muscle, has patchy cartilage

bronchioles- have cilia and smooth muscle but no cartilage

Question 7

Describe the respiratory zone of the airway wall. For each component give the number, whether or not has cilia, smooth muscle, or cartilage.

Which have smooth muscle? Which have cilia?

Answer 7

respiratory bronchioles- some cilia, some smooth muscle, no cartilage

alveolar ducts- no cilia, some smooth muscle, no cartilage

alveolar sacs- (6x10^8) no cilia, no smooth muscle, no cartilage

Question 8

Describe the lobes of the lungs. How are they partitioned? What purpose does this serve?

What is a pneumothorax? What could cause it?

Answer 8

LOWER AIRWAYS
Lobes of the Lung
The human lung is partitioned into 5 lobes with 3 lobes on the right (RUL, RML, RLL) and 2 lobes on the left (LUL, LLL), leaving room for
projection of the left ventricle.
Lobulation of the lung allows for greater flexibility and movement of the torso without producing excessive stress/strain forces on
the lung tissue. As the lobes slide and glide over each other the lung is protected from ripping and tearing, resulting in a pneumothorax (lung
collapse).

Question 9

Describe the conducting airways.

Do they participate in gas exchange?

Describe the trachea, C rings and purpose. Are the C rings more important during inspiration or expiration?

Describe the back wall of the trachea. Does the muscle contain sarcomeres? Describe the function of the muscle. What does it protect from?

Describe the R and L mainstream bronchus and how they bifurcate.

Answer 9

(do not participate in gas exchange):
The human trachea: A single open tube; the C-shaped cartilaginous rings keep the trachea from collapsing (especially during exposure to negative pressures during inspiration).

The back wall of the tracheal consists of non-striated muscle, behind which lies the esophagus. The flexible smooth muscle can change the cross-sectional area of the trachea (e.g. as during coughing) and protects from over-distension.

The right mainstem bronchus divides into three airways that penetrate the 3 right lobes of the lung. The left mainstem bronchus divides into two airways that penetrate the 2 left lobes of the lung. Within each of the 5 lobes, the airways continue to bifurcate, become shorter and narrower

Question 10

Diagram the conducting airways/respiratory unit.

What is the anatomical “dead space”? Describe. Volume?
Describe the transition zone.

Answer 10

Slide 18.

Airway generations 1-16 do not have alveoli (gas conduction only “dead space”
The anatomical dead space has a volume of about 150mL. Airway generations 17 and higher are alveolated and participate in gas exchange. Airways between the terminal bronchioles and respiratory bronchioes that are only partially alveolated constitute the transition zone. On average transition zones occur around generations 17 to 19.

(bronchopulmonary segment is functional anatomic unit of lung and respiratory unit is the basic physiological unit)

Question 11

Graph how airway generation changes with increases in total cross sectional area.

Describe the fundamental working unit of the lung.

What is the volume of lung that participates in gas exchange?

Answer 11

Slide 19.

alveolus is the fundamental working unit of the lung. (slide 19 picture). the overall volume of the lung that participates in gas exchange is about 2500mL and the surface area is 70m^2.

The cross sectional area increases exponentially w increases in airway generation.

Question 12

Describe/draw the alveolar-capillary network.

Type I and II alveolar cells, alvolar fluid lining with pulmonary surfactant. alveolar macrophage, erethrycyte, pulmonary capillary, interstitial fluid.

How much of the alveolar sufrace is Type I or Type II?

Answer 12

Normal lung has 5x10^8 alveoli.

95-97% of alveolar surface consists of squamous epithelial cells (alveolar type I cells) that are very thin (25 nm) with a large surface area (70m^2) which are ideal for diffuse gas exchange with the pulmonary capillary bed.

2-4 percent of alveolar surface consists of type II cells, which produce surfactant.

alveolar macrophages- participate in host defense

Question 13

Describe the shape of pulmonary capillaries and the implications of this.

Answer 13

are wider than they are long, meaning that the blood passes through the lungs as a sheet flow.

Question 14

Describe the capillary-pulmonary endothelium.

Answer 14

At all times and on all sides the capillary blood is in contact with the alveolar space through the ultra-thin alveolar-capillary membrane.

Sandwiched together with the alveolar epithelium is the pulmonary capillary endothelium that is very thin (60nm) with a large surface area (70-70m^2).

Question 15

What are alveolar macrophages?

Answer 15

host defense

innate immune response.

alveolar macrophage- like an aneba, phagocytose particles, engulf foreign particles. job to keep surface clean. alveolar don’t have mucociliary escalator so another mechanism needed req. to keep alveolar surface clean and thats the macrophage

Question 16

Describe the surface tension on the lungs.

What is the effect of surface tension? What would happen if surface tension was the only involved force?

Answer 16

attractive forces between H2O molecules are very large, preventing other molecules from coming “in-between” thereby creating an opposing force at the surface allowing heavier than water objects to “float”

(H2O molecules attract each other more than H2O - air on the surface)

• creates surface tension
• resists being stretched
• tends to reduce surface area (= volume)
• creates tendency to recoil after stretch

Surface tension is so high, alveoli/lungs would collapse. Lung w absence of surfactant? surfactant produced late in fetal life. some babies born w absence of surfactant… collapsed lung in some areas, unstable lung. lung stuff, difficult to expand, has alveolar edema, surfactant is essential for healthy lung. recognition of surfactant, its composition and that now its possible to produce surfactant from animals, make it, and administer it to babies without it..

surfactant
-makes lung less stiff, -increases compliance of the lung
-increases stability of the lung
reduces tendency of alveolar edema (bc got alveolus which contracts, reduces pressure around capillaries in alveolar wall, when reduce pressure around capillaries, causes edema fluid to go out, reduce surface tension and reduce tendency of alveolar edema to occur)

Question 17

Describe the Law of Laplace.

What would the surface tension (T) be when R=1, R=2?

Answer 17

magnitude of inward directed pressure (P) in a bubble (alveolus) = 2x surface tension (T)/ Radius (r) of bubble (alvolus)

Radius =1, surface tension so P=2T
Radius =2, P= 1T

small bubbles would collapse, large bubbles would become over-distended.

Question 18

Because surface tension is so high, small alveoli would collapse and large alveoli would become over-distended due to the Law of Laplace. Why does this not actually happen?

Answer 18

Surfactant produced by alveolar type II cells, a lipoprotein complex (phospholipids: dipalmitoylphosphatidylcholine), surfactant associated proteins (SP-A, B, C, D), and neutral lipids all reduce surface tension and stabilize alveoli.

Question 19

Which has more surfactant per surface area; large or small alveoli? Why?

Show with equation, the change.

Answer 19

Small alveoli contain more surfactant per surface area than larger alveoli, which permits maintenance of alveoli with different sizes.

(so with a smaller alveoli, surface tension changes T to 1/2 T so P= 1 T and P1=P2) …see slide 24

Question 20

Describe the stability of alveoli and how that is maintained.

How is the tendency to collapse opposed?

Answer 20

1. surfactant
2. interdependence

Alveoli are mechanically tethered together.

The tendency to collapse is opposed by the traction exerted by the surrounding neighbor alveoli.

Question 21

What role do the interbronchiolar channels of Martin, Lambert and pores of Kohn serve? Draw.

Answer 21

Slide 26.

Interbronchiolar channels of Martin, bronchiole-alveolar channels of Lambert and pores of Kohn permit collateral ventilation.

Question 22

Describe the bronchial circulation to the lungs.

Answer 22

bronchial circulation arises from aorta and provides nourishment to lung parenchyma. (circulation to lung is unique in its ability to accommodate large volumes of blood at low pressure)

Slide 27/ (h/o)
Bronchial arteries:
-from aorta to terminal bronchioles
-merge with pulmonary arteries and capillaries
-1-2% of total CO
-nourish walls of bronchi, bronchioles, blood vessels and nerves

Bronchial veins:

• 1/3 blood returns to the R atrium through bronchial veins (v. azygous, v. hemiazygous, intercostal veins) from the first 2-3 generations of bronchi, whereas the remainder drains into L atrium via pulmonary veins
• 2/3 drain into pulmonary circulation
• contributes to “venous admixture” or “anatomic shunt”

Question 23

Describe the pulmonary circulation to the lungs.

Answer 23

• primary purpose is to deliver blood to the lung for gas exchange
• largest vascular bed in the body (70m^2)
• capillary volume - at rest; 70mL; during exercise: 200mL

Question 24

What are the metabolic functions of the pulmonary circulation?

Answer 24

conversion of angiotensin I to angiotensin II, inactivation of bradykinin, removal of serotonin, norepinephrine, prostaglandins, leukotrienes, drug metabolism

Slide 29, 30.
expression of enzymes important for drug metabolism (Phase 1 and Phase 2 enzymes)
expression of major drug transporters

Question 25

Describe deposition of inhaled material (impaction, sedimentation, diffusion)

Describe the particle size and representative site.

Answer 25

Impaction: large particles (>5 micrometers), nasopharynx

Sedimentation: medium particles (1-5 micrometers), small airways

Diffusion: small particles (

Question 26

Describe the three components of the mucociliary clearance system.

Answer 26

mucus layer- lies on top of periciliary fluid and entraps inhaled particles (healthy individuals produce about 100mL of mucus per day)

periciliary fluid

cilia- embedded in periciliary fluid and only their tips contact the mucus layer, beat approx. 1000 strikes per minute, in the trachea they propel mucus toward the pharynx, where it is swallowed.

Question 27

Walk through the clearance of inhaled particles from nasopharynx to lymphatics.

Answer 27

in nasopharynx the particles are swallowed, then in the bronchi the mucociliary system transports particles

in alveoli the alveolar macrophages engulf particles

then lymphatics

Question 28

Key concepts review:

What filters warm and humidify air?

How are airways divided?

What is the volume of anatomic dead space?

What is the volume of the respiratory region?

Answer 28

Upper airways filter, warm and humidify air

Airways are divided into a conducting zone (down to terminal 
bronchioles, generation 16) and a respiratory zone 
(generations 17-23)

Volume of the anatomic dead space: ~ 150 mL

Volume of the respiratory region: ~ 2.5 – 3 L, surface area 50-100 m2

Question 29

Key concepts review:

What is the functional anatomic unit and basic physiological unit?

Describe the alveolar capillary network.

What stabilizes alveloi?

Answer 29

The broncho-pulmonary segment is the functional anatomic unit, 
the respiratory segment (respiratory bronchi and alveolar ducts) 
is the basic physiological unit.

The alveolar capillary network is extremely thin, ideal for gas 
exchange.

Surfactant (reduction of surface tension), interdependence 
and collateral ventilation stabilize alveoli

Question 30

Key concepts review:

What are the 2 circulations in the lung?

Where does the lung receive input from?

What is the largest vascular bed in the body?

Describe the shape of the capillary segments and the implications.

Does the lung have metabolic functions?

What does the mucociliary transport system do?

Answer 30

The lung has 2 circulations (bronchial/pulmonary)

The whole of the output of the right heart goes to the lung

The pulmonary circulation is the largest vascular bed in the body

The capillary segments are very short and blood forms an almost 
continuous sheet

The lung has also metabolic functions 

The mucociliary transport system removes inhaled particles

Question 31

How does blood supply change in the presence of diseases like CF?

Answer 31

bronchial arteries, which normally receive 1-2 percent of CO, increase in size (hypertrophy) and receive as much as 10 to 20 percent of CO. The erosion of inflamed tissue into these vessels secondary to bacterial infection is responsible for the hemoptysis (coughing up blood) that occurs in this disease