Respiration

Front 1

Functions of the Conducting Airways

Back 1

1. Defence via mucociliary defence system
2. Warm and moisten inhaled air
3. Production of sound and speech
4. Regulation of airflow

Front 2

Alveolar Cell Types

Back 2

Three alveolar cell types:
1. Epithelial type I and II cells: form epithelial layer sealed by tight junctions. Type II cells produce pulmonary surfactant.
2. Endothelial cells: pulmonary capillaries.
3. Alveolar macrophages: foreign particles that escape the mucociliary defence system.

Front 3

Inspiratory Muscles

Back 3

Diaphragm:
- innervated by phrenic nerves from cervical segments 3, 4 and 5.
- contraction leads to longitudinal expansion
- elevates the lower rib cage due to attachments of the costal margins

External Intercostal Muscles:
- raises rib cage - anterior-posterior and transverse expansion
- usually only when during high levels of ventilation or obstruction in asthma etc.

Parasternal Intercartilaginous Muscles:
- upper most part of rib cage, elevate sternum
- anterior-posterior and longitudinal expansion

Front 4

Expiratory Muscles

Back 4

- During quiet breathing: recoil of lungs and the chest wall, passive.
- Higher levels of ventilation: internal intercostal muscles and abdominal muscles.

Front 5

Minute Ventilation

Back 5

Ve is the amount of air inspired (or expired) during one minute.
Minute Ventilation = Tidal Volume x Breaths/minute
Ve = Vt x f

Front 6

Alveolar Ventilation

Back 6

Amount of air that reaches the respiratory zone per minute and is available for gas exchange.
In normal adult male, alveolar ventilation Va: 4200mL/min

Front 7

Physiological Dead Space

Back 7

The sum of alveolar and anatomical dead space. Difference between minute and alveolar ventilation is the dead space ventilation that is wasted from the gas exchange point of view.
Vd = Ve - Va

Front 8

Pulmonary Vascular Resistance

Back 8

Increasing Resistance by Vasoconstriction:
- drugs: serotonin, histamine, norepinephrin
- reflex vasoconstriction in regions that are poorly oxygenated.
- Above FRC when alveolar vessels are stretched longitudinally
- Below FRC when extra alveolar vessels collapse

Decreasing Resistance by Vasodilation:
- drugs: acetylcholine, isoproteranol
- nitric acid produced by the endothelial cells

Front 9

Measuring Pulmonary Blood Flow

Back 9

Q = Vo2/(CaO2 - CvO2)

Front 10

Henry's Law

Back 10

Henry's law states that the number of gas molecules dissolved in a liquid is proportional to the partial pressure of the gas above the liquid.

Front 11

Oxygen Consumption at Rest
Carbondioxide Production at Rest

Back 11

300 mL O2/min
250 mL CO2/min

numbers go up 20 times during exercise

Front 12

Oxygen Dissociation Curve

Back 12

Determines the amount of oxygen carried by Hb for a given partial pressure of O2.

Front 13

Bohr Effect

Back 13

The shift of the HbO2 dissociation curve to the right when blood CO2 or temperature increases, or blood pH decreases.
Also occurs when 2,3-diphosphoglycerate increases. (lung disease or high altitude)

CO shifts it to the left

Front 14

Carbondioxide Transport

Back 14

1. Physically dissolved in blood (10%)
2. Combined with Hb to form HbCO2 (11%)
3. As bicarbonate (79%) - CO2 and H2O combine to give carbonic acid (H2CO3) aided by carbonic anhydrase which then dissociates into HCO3- and H+

Front 15

Haldane Effect

Back 15

Mixed venous blood can carry more CO2 than arterial blood.

Front 16

Respiratory Failure

Back 16

1. Gas exchanging capabilities of the lungs
2. Neural control of ventilation
3. Neuromuscular breathing apparatus.

Front 17

Causes of Hypoxia

Back 17

1. low PO2 - high altitude
2. hypoventilation: disease of CNS, neuromuscular diseases, barbiturates, other drugs and narcotics
3. ventilation/perfusion imbalance in the lungs
4. shunts of blood: venous blood bypasses gas exchange areas
5. O2 diffusion impairment: thickening of membrane, pulmonary edema

Front 18

Voluntary vs. Involuntary Breathing

Back 18

Voluntary: Cerebral hemisphere
Involuntary: Brain stem: pons and medulla

Front 19

Breathing Pattern

Back 19

Medulla: pacemaker cells in two groups:
- ventral respiratory group: contains the pre-Botzinger complex, generates basic rhythm.
- dorsal respiratory group: receive sensory inputs

Pons:
- rostral (upper) pons: called pneumotaxic center - turn off inspiration, increasing frequency and decreasing tidal volume (deep and slow breathing if cut it - same for vagus)
- lower pons: called the apneustic center - sends excitatory impulses to medulla, promoting inspiration.

Front 20

Chemoreceptors

Back 20

1. Central chemoreceptors:
- located on ventral surface of the medulla
- detect pH of the CSF
- increase minute ventilation

2. Peripheral chemoreceptors:
- mainly sensitive to changes in PO2 but also stimulated by increase PCO2 and decreased pH
- located in carotid bodies and aortic bodies (made up of:
a. blood vessels
b. structural supporting tissue
c. nerve endings of sensory neurons of glossopharyngeal and vagus nerves.

carotid bodies: IX nerve
aortic bodies: X nerve

- afferent fibers project to dorsal group of respiratory neurons in the medulla

Front 21

Pulmonary Vagal Receptors

Back 21

1. Pulmonary stretch receptors:
- located in smooth muscle from trachea to terminal bronchi
- innervated by large myelinated fibers
- Hering-Breuer Inflation Reflex: mostly in infants and animals - decrease in frequency after increase in lung volume

2. Irritant receptors:
- located between airway epithelial cells from trachea to respiratory bronchioles
- stimulated by noxious gases, cigarette smoke, histamine, dust, cold air.
- innervated by myelinated fibers
- leads to bronchoconstriction and hypernea (deep breathing)

3. Juxta-capillary or J-receptors (C-fibers):
- located in the alveolar walls close to the capillaries
- innervated by non myelinated fibers
- stimulated by increased pulmonay interstitial fluid (in pulmonary congestion or edema) and have short bursts of activity
- induce rapid and shallow respiration - intense stimulation causes apnea
- may play a role in dyspnea (difficulty in breathing) in left heart failure and lung edema/congestion

Front 22

Pneumothorax

Back 22

Hole punctured through the chest - chest springs outward and the lungs collapse

Front 23

Recoil Pressure of Chest Wall

Back 23

Pw = Ppl - Pbs

Front 24

Recoil Pressure of the Lungs

Back 24

Pl = Palv - Ppl

Front 25

Recoil Pressure of the Total Respiratory System

Back 25

Prs = Palv - Pbs
Prs = Pl + Pw

Front 26

Compliance

Back 26

Refers to the ease with which a structure can be distended.

Front 27

Compliance of the Lungs

Back 27

Cl = dV/(dPalv-dPpl)
E = 1/C
E = (dPalv-dPpl)/dV

Front 28

Compliance of the Chest Wall

Back 28

Cw = dV/dPpl

Front 29

Compliance of the Respiratory System

Back 29

Crs = dV/dPrs
Crs = dV/d(Pl + Pw)
1/Crs = 1/ Cl + 1/Cw

Front 30

Force of Inspiration

Back 30

F = (Palv - Patm)/R

Front 31

Resistance of the Airways

Back 31

Raw = (Palv-Pao)/Flow

Front 32

Laplace's Law

Back 32

P = 4T/R