34. Respiratory tracts, respiratory movements, panting

Question 1

What should be mentioned?

Answer 1

Upper respiratory tract
Lower respiratory tract
Mechanism of respiration: Inspiration and expiration
Difference in ventilation
Fluid film
The "mouse-elephant" curve
Panting

Question 2

Upper respiratory tract

Answer 2

Nasal cavity – The surface is covered by ciliated cylindrical epithelium. These with the blood vessel capillaries play a defensive, air conditioning and heat transfer role.
• Defending the organism: Mechanical (mucus motion coughing) and immunological
• Air conditioning: saturates the inspired air with water vapor, warms up the air
• Heat transfer: heat let down
Oral cavity – contributes significantly to ventilation in case of the increased respiration.
Pharynx – Primarily it has a defensive function with a mucous layer and with well-developed lymphatic vessels and lymphatic gland system.
Larynx – The site of voice formation, with a mechanism significantly differing from species to species.

Question 3

Lower respiratory tract

Answer 3

Function: filtering and protective function.
Trachea – main bronchous, the upper part of the lower respiratory tract, defensive role. The epithelium contains goblet cells. Cilia of epithelium are moving in sol phase.

Terminal bronchioles – without ciliary epithelium
Bronchiolus respiratorius – respiratory epithelium appears, and from here gas exchange takes place.

Alveoli – the basic unit of ventilation. Here the distance between the air and the blood cell extremely decreases, the wall of the alveolus becomes closely attached to the individual red blood cell.

Between the blood and the atmospheric air there are only four histological layers that create a barrier:
1. Surfactant layer
2. Alveolar layer
3. Membrane basalis
4. Capillary endothel
The alveolar wall is built up by two types of pneumocytes. The epithel providing the actual gas exchange. The second type of cells (T2) produce the surface active material (surfactant) layer.

Question 4

The mechanism of respiration: Inspiration

Answer 4

Inspiration (active process)
• Participants are diaphragm, external intercostal muscles and abdominal muscles.
• The diaphragm has the major role during inspiration. It expands the inner space of the chest.
• The mm intercostales externi raise the ribs, helps the inspiration. Lung sections close to diaphragm and pariental region can dialate more easily and ventilate much better.
• The lung has a collapsing tendency due to the surface tension of alveoli and elastic elements of the lung. During inspiration active muscle work is needed against the collapsing tendency.

Question 5

The mechanism of respiration: Expiration

Answer 5

Expiration (inactive process)
• It is driven by the collapsing tendency of the lung. Returning of ribs to resting position and passive pressure from abdominal direction help the process.
• The total collaps is prevented by adhesional forces, provided by a fluid-film between the visceral and the parietal pleura.

Pause of respiration: is a balanced status, chest in rest. The retractive force of the lung is balanced with the tension of the muscles and joints of the chest.

Rate of respiration: breaths/min, breathing frequency depends on the metabolic activity of the animal.

Question 6

Difference in ventilation (picture)

Answer 6

• The figures show the role of the diaphragm in respiration. Notice that the roundness of the diaphragm is changing, not its diameter. This expands the inner space of the chest.
• The part indicated with red represents the central muscle elements of the diaphragm, while the blue represents the tendon-lamella.
• In large animals the diaphragm plays the most important role at inspiration

Question 7

Fluid film

Answer 7

the total collapse of the lung is prevented by the adhesional forces (fluid film) between the parietal and visceral plates of the pleura.

A water layer between two glass panels eases the sliding of plates over each other, but makes the pulling apart of them difficult. The same way the liquid between the plates of the pleura do not let the lung to collapse.

Question 8

The “mouse-elephant” curve (picture)

Answer 8

The relationship of body size and breathing frequency. The breathing frequency depending on metabolic activity is the greatest in animals of the smallest body size.

Question 9

Panting

Answer 9

• During panting only physiological gas exchange happens (gas pressure changes only slightly). The major role of panting is heat exchange (thermoregulation).
• A parietal and a central air flow can be observed in ventilation during panting.
• Parietal gas exchange is slow, the gas pressure is maintained, elimination of CO2 (release) will not increase despite of the high panting frequency.
• Central gas stream is fast and serves heat exchange, and also stimulates water release in the mouth (perspiration insensibilis, which also takes considerable amount of heat away from the body).
• Such high frequency(hyperventilation) would create serious alkalosis in other species (without two types of air flow) due to the high loss of CO2.