Chapter 103 Lungs Flashcards
How many paris of ribs do dogs and cats have and how may sternebrae?
13 pair of ribs and 8 sternebrae
List the subdivisions of bronchi, from mainstem bronchus –> alveloi
- Two principal bronchi
- Lobar bronchi that supply each lung lobe
- Segmental bronchi that supply bronchopulmonary segments.
- Dichotomous branching of the airway continues through subsegmental bronchi, terminal bronchioles, and respiratory bronchioles. Respiratory bronchioles give rise to alveolar ducts, alveolar sacs, and pulmonary alveoli.
Along which aspect of bronchi do arteries run? Where is oxygenated supple received from?
Arteires run cranial and dorsal (veins caudal/ventral).
Bronchooesophageal arteries supply oxygenated blood
Name the principla mechanisms responsible for normal inspiration and expiration?
Inspration due to diaphragmatic contraction, expiration due to elastic recoil
List 4 muscles that assist with inspiration when necessary
And expiration?
Inspiration
- External intercostal muscles
- Scalenus
- Serratus ventralis
- Sternocleidomastoid
Expiration
- Internal intercostals
- Rectus abdominis
Define elastance and compliance
- Elastance* (recoil) degree to which lung can return to its dimensions after removal of distending forces. Pressure change required to elicit a unit volume change (ΔP/ΔV)
- Compliance* measure of lung distensibility (reciprocal of elastance) (ΔV/ΔP). Can be estimated from pressure-volume loops (steeper slope = greater compliance). Normally lung compliance os lowest at high and low volumes.
What type of cells secrete surfactant?
Type 2 alveolar cells
What is normal PaO2?
What is considered hypoxaemic?
>90 mmHg (N.B. should be approx x5 Fi oxygen)
<80 mmHg moderate hypoxaemia
<60 mmHg severe hypoxaemia (approx SpO2 of 90%)
List the percentage contribution of nares/nasal, larynx and small airways to inpiration.
And to expiration
Inspiration
Nares 79%
Larynx 6%
Small airways 15%
Expiration:
Nasal 74%
Larynx 3%
Small airways 23%
What are the most important regulators of ventilation?
Chemoreceptors (central in medulla of brain) and carotic and aortic bodies (peripheral. Usually have more rapid but smaller magnitude of response)
Change in ventilation has the greatest response to PaCO2 (as opposed to PaO2 or pH), but if PaO2 falls below 60 mmHg ventilation increases - what is the name of this response?
Hypoxic ventilation drive
What is typical canine and feline tidal volume?
10 ml/kg
What does Fick’s law state?
Fick’s law states that rate of transfer of a gas through a sheet of tissue is proportional to surface area available for diffusion, diffusion coefficient of the gas, and difference in gas partial pressure between the two sides and inversely proportional to the tissue thickness (distance the gas must travel).
What id the approx surface area of the lungs?
An thickness of at blood-gas interface?
At the blood-gas interface, the lungs have a surface area of 50 to 100 m2
0.3-µm thickness
How does the diffusion coefficient of CO2 differ from O2?
The diffusion coefficient of CO2 is 20 times greater than that of oxygen; CO2 therefore diffuses more rapidly
i.e. if limited space for diffusion and diffusion distance inreased, hypoxaemia can occur before evidence of hypercapnia