Respiration

Question 1

Pulmonary Respiration

Answer 1

Ventilation (breathing) and the exchange of gases (O2 & CO2) in the lungs

Question 2

cellular respiration

Answer 2

Relates to O2 utilization and CO2 production by the tissues

Question 3

Major Functions of the Respiratory System

Answer 3

To supply the body with oxygen and dispose of carbon dioxide
Respiration – four distinct processes:
Pulmonary ventilation – moving air into and out of the lungs
External respiration – gas exchange between the lungs and the blood
Transport – transport of oxygen and carbon dioxide between the lungs and tissues
Internal respiration – gas exchange between systemic blood vessels and tissues

Question 4

Exchange of Oxygen and Carbon dioxide between
the environment and the cells of the body

Answer 4

respiration

Question 5

The Human Respiratory System

Answer 5

Respiratory Pump- lungs, airways, thoracic cavity, respiratory muscles
Gas Exchange System- alveoli- big SA, pulmonary Capillaries, local regulation of ventilation and perfusion
02 &CO2 Transport- Hb and other blood components

Question 6

Protective function of the upper Airways

Answer 6

• Major Function = To ‘condition’ inspired air
• Nose – function to filter, entrap and clear particles
  greater than 10μM
• Nasal resistance increases with viral infections and
  increased airflow eg: during exercise
• Nasal secretions contain important immunoglobulins,
  inflammatory cells and Interferons

Question 7

Lungs

Answer 7

Mainly air spaces
Together weigh about 1kg
Blood is delivered via the pulmonary arteries and is transported back the heart via pulmonary veins
Surrounded in a double layered wall the pleura which are separated by pleural fluid which allows for low friction movement of the lungs during breathing
Pleurisy: inflammation of the pleura, is caused by decreased secretion of pleural fluid

Question 8

Lung lobes

Answer 8

Two lungs: left and right:
Right lung has 3 lobes - (Superior, Middle, Inferior)
Left lung has 2 lobes – (superior and Inferior)

Question 9

Tissue Surrounding Lungs

Answer 9

Parietal Pleura- Lines the inner walls of the chest cavity, 10ml occupies the pleural space

Visceral Pleura- Membrane that lines the outer surface of the lungs, contain lymphatics that drain the blood from pleural space (space between parietal and visceral
pleura)

Question 10

Structure vs Function

Answer 10

Lungs are anatomically shaped to fit the thoracic cavity

Lungs are ventilated with atmospheric air by a
‘tree like’ airway

- Conducting zone
- Respiratory zone

Question 11

Conducting Zone

Answer 11

Airflow by convection, relatively fast

Warm, humidify, clean air

Defense system (mucous and cilia)

No gas exchange

Dead space (100 – 150 mL)

Question 12

Respiratory Zone

Answer 12

All airways beyond the
terminal bronchioles
(respiratory bronchioles, alveolar ducts and alveoli)
Total ~ 300 million alveoli
In both lungs
Supplied by Pulmonary circulation
Airflow by diffusion (slow- important for gas exchange)
Participate in Gas exchange

Dual Blood Supply to lungs, bronchial and pulmonary

Question 13

Respiratory Zone

Answer 13

Defined by the presence of alveoli; begins as terminal bronchioles feed into respiratory bronchioles
Respiratory bronchioles lead to alveolar ducts, then to terminal clusters of alveolar sacs composed of alveoli
Approximately 300 million alveoli:
Account for most of the lungs’ volume
Provide tremendous surface area for gas exchange

Question 14

Thoracic cavity

Answer 14

The thoracic cage is a closed compartment.
Diaphragm: Sheets of striated muscle divides anterior body
cavity into 2 parts
Above diaphragm:
Thoracic Cavity. Contains heart, lungs, blood vessels, trachea, oesophagus, thymus and lungs
Below diaphragm:
Abdominopelvic cavity. Contains liver, pancreas, GI tract, spleen and genitourinary tract.

Question 15

Pulmonary Ventilation

Answer 15

Air flows: atmosphere lungs due to difference in pressure related to lung volume

– Lung volume changes : respiratory muscles

Inhalation: Active
Diaphragm + external intercostals
- Diaphragm contracts (moves downward) ­
- External intercostals move ribs upwards and outwards

Exhalation : Passive
Exercise – internal intercostals contract to bring about forceful expiration

Question 16

Inspiration

Answer 16

always an active process involving contraction of the muscles of breathing

Question 17

Expiration

Answer 17

is a purely passive process involving relaxation
of the muscles of breathing together with elastic recoil of the lungs
During forced breathing, as in exercise, expiration becomes an active process

Question 18

Inspiration and Expiration

Answer 18

Inspiration - the volume of the thoracic cavity is increased by the actions of:
the diaphragm contracting and flattening out
the contraction of the external intercostal muscles which elevates the rib cage and thrusts the sternum forward
Expiration:
quiet expiration is largely passive and depends upon the natural elasticity of the lungs
forced expiration however is active and is produced via the contraction of the abdominal wall

Question 19

Respiratory Pressures

Answer 19

Alveolar Pressure : Pressure within the alveolus

Intrapleural pressure : pressure between the 2 layers of the pleura

Transpulmonary pressure: Pressure across the wall of the alveolus

Atmospheric pressure : 760 mm Hg

Question 20

ventilation

Answer 20

Air moves by ‘bulk flow’ from high pressure to low pressure.
Air moves in and out of the lungs because the alveolar pressure is made alternately less than and greater than atmospheric pressure.

Question 21

Pressure Changes during Inspiration

Answer 21

inspiratory muscles contract
thoracic cavity expands in volume
pleural pressure falls -5 to -8
transpulmonary pressure gradient increases PTP = PA – PIP
↑ PTP causes alevolar expansion
Alveoli expand in volume
alveolar pressure falls 0 to -1
air flow down the gradient from PATM to PA

Question 22

Relationship of Lungs PLeura and Thoracic wall

Answer 22

The intrapleural space is at a low pressure to keep lungs expanded. (pneumothorax)
Inspiration: From contraction of the diaphragm intrapleural and alveolar pressure fall, allowing air flow into lungs
Expiration: Stretched lung tissue recoils, releasing air passively (during quiet breathing)

Question 24

compliance

Answer 24

changes in pressures lead to changed in lung volume
lungs and thoracic wall can expand
relative change V/P = compliance
-elasticity
-surface tension

Answer 25

at the air-water interface of the airways accounts for half or more of the elastic recoil of the lungs. The EC matrix (anatomic) components eg elastic & collagen, account for less than half of the lung’s elastic recoil. a spherical bubble surrounded by water (fig 26-7D, Boron), unbalanced forces acting on surface molecules causes them to dive into the bulk (tend to pull away from the surface of the bubble), decreasing the surface area, and creating tension in the air-water interface (like a belt tightening around one’s waist, decreasing the volume of the compressible gas and increasing the P). at equilibrium the tendency of increased P to expand the gas bubble balances the tendency of the surface tension to collapse it. Laplace’s equation describes this equilibrium: P = 2T/r. P is the dependent variable, T is constant for a particular interface, and the bubble radius R is the independent variable. Therefore the smaller the bubble’s radius, the greater the P to keep it inflated. The bubble-water analysis is imp for the lung, because thin layer of water covers the inner surface of the alveoli. The surface tension at the air-water interface causes the bubble to constrict; it also causes alveoli and other airways to constrict contributing greatly to elastic recoil. The analogy between the bubble and alveolus is not complete as:The alveolus is not a complete sphere. Not all alveoli are the same size (some diameters may be 3-4x larger than others). Alveoli are interconnected.

Question 26

Surface Agent

Answer 26

Pulmonary surfactant – lipoprotein rich in phospholipid Secreted by type II cells in the alveolus Hydrophobic and hydrophilic regions (Amphihilic molecule) Reduces surface tension greatly – increasing lung compliance Surfactant prevents small alveoli from collapsing and large alveoli from expanding too much

Question 27

Type I cells –

Answer 27

Flat squamous thin large surface area, ideal for allowing gas diffusion across them

Question 28

Type II cells –

Answer 28

Cuboidal, secrete surfactant  detergent –like fluid, helps lower surface tension of alveoli

Question 29

Deficiency of Surfactant

Answer 29

= RDS (Respiratory Distress Syndrome) of the Newborn = ARDS (Adult Respiratory Distress Syndrome) in adults (eg. TRALI; Transfusion Related Lung Injury)

Question 30

Factors Affecting Lung Mechanics

Answer 30

Lung Compliance: The ‘elasticity’ of the lung tissue The lung compliance may be affected by thickening of lung tissue Surfactant: Phospholipid produced by type II alveolar cells, reduces surface tension in alveoli (Caused by H2O) increases total lung compliance

Question 31

Factors Affecting Lung Mechanics

Answer 31

Airway Resistance: Flow of air depends on pressure gradient (atmospheric pressure, Pa and intra-plural Pi) and the airway resistance, R F = (Pa – Pi)/R Resistance depends primarily on the radius of the conducting airways Parasympathetic stimulation constricts, while sympathetic dilates Narrowing of airways e.g. asthma; thus, more energy is required to inflate lungs.

Question 32

Spirometry

Answer 32

Measurement of Lung Volumes and Capacities – only exhaled vols can be measured

Question 32

Air moves by ‘bulk flow’ from high pressure to low pressure

Answer 32

Air moves in and out of the lungs because the alveolar pressure is made alternately less than and greater than atmospheric pressure.

Question 33

Respiratory Volumes

Answer 33

Tidal volume (TV) – air that moves into and out of the lungs with each breath (approximately 500 ml) Inspiratory reserve volume (IRV) – air that can be inspired forcibly beyond the tidal volume (2100–3200 ml) Expiratory reserve volume (ERV) – air that can be evacuated from the lungs after a tidal expiration (1000–1200 ml) Residual volume (RV) – air left in the lungs after strenuous expiration (1200 ml)

Question 34

Respiratory Capacities

Answer 34

Inspiratory capacity (IC) – total amount of air that can be inspired after a tidal expiration (IRV + TV) Functional residual capacity (FRC) – amount of air remaining in the lungs after a tidal expiration (RV + ERV) Vital capacity (VC) – the total amount of exchangeable air (TV + IRV + ERV) Total lung capacity (TLC) – sum of all lung volumes (approximately 6000 ml in males)

Question 35

FRC

Answer 35

volume remaining in the lungs at end of a quiet expiration (Tidal Volume exhalation)

Question 36

RV

Answer 36

Volume remaining in the lungs at end of a forceful, maximal expiration (Forced Vital Capacity)

Question 37

Anatomic Dead Space

Answer 37

The conducting airways have a volume of about 150ml. Exchanges of gases with the blood only occur in the alveoli and not in the dead space. Tidal volume = 450ml Anatomic dead space = 150ml Fresh air entering alveoli in one inspiration = 450ml - 150ml = 300ml

Question 38

Gas exchange

Answer 38

The flow of O2 across the barrier separating the blood from air or water occurs by diffusion * Pressure gradient from a point of high PO2 to a point of lower PO2. * This gradient exists throughout the respiratory system. 02: air ----Lungs------ Blood----- Cells C02: Cells---- Blood ----Lungs---- air

Question 39

Summary

Answer 39

Gas laws show relationship between partial pressures, solubility and concentration of gases Gases diffuse along their partial pressure gradients from regions of high partial pressure to regions of low partial pressure External respiration : 02 loads from alveoli into pulmonary capillaries C02 unloads from blood into alveoli

Question 40

Central chemoreceptors :

Answer 40

Respond to changes in H+ and Co2 in cerebrospinal fluid

Question 41

Peripheral chemoreceptors :

Answer 41

Respond to changes in H+, PCO2 and O2 in the blood