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23 Cards in this Set
- Front
- Back
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What are the 4 phases of lung development, including the rough timing of each period? |
- Embryonic period ( 0-7 weeks) - Pseudoglandular phasde (5-17 weeks) - Cannicular phase (13-27 weeks) - Terminal Sac Period (24-40 weeks) |
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What occurs during the embryonic period of lung development? |
Development of airways occurs (0-7 weeks) - Outpouching of foregut forms primitive respiratory tube - Primitive lung buds form - Branches down to lobar branches - Pulmonary vasculature begins to form |
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What occurs during the pseudoglandular phase? |
Multiplication of airways occurs (5-17 wks) - Bronchial branching completes - Formation of muscle fibres, elastic - diaphragm develops (hernias arise in this period) |
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What occurs during the cannicular phase? |
Alveolar buds begin to form (13 - 27 weeks) - cilia form in conducting airways - alveolar buds and saccules form - vascularisation of respiratory portion of lung |
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What happens during the terminal sac period? |
Cilia, surfactant and alveoli development - Terminal sacs appear and divide in to alveolar ducts - Epithelial cells of alveoli differentiate in to type 1 and 2 - at term, only primitive alveoli are formed - surfactant production begins to occur |
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Are alveoli fully formed at birth? What are the implications of this? |
No, only primitive alveoli (saccules) are present at birth. These will continue to mature for several months after birth. The implications of this is there is a decreased surface area for gas exchange |
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How many generations of bronchi are present at birth? |
16. The final generations (23rd) don't form until around 14 years of age |
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How many divisions of bronchi form in a mature lung? When are the final divisions formed? |
23 divisions in a mature lung. Final division occurs at around 14 years of age. |
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When does alveoli formation end? |
Alveoli continue to form until around 8-11 years of age |
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Diameter of infant airways is much smaller than adult airways. What is the functional implication of this? |
The narrower lumen of the infant airway means there will be much more resistance to flow (remember R=1/r^4) It also means that infant airways are much more effected by oedema and other things that might narrow the lumen. |
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What is ratio of heart to ribcage in adults vs infants? |
Adults: 1/3 of ribcage Infants: 1/2 of ribcage |
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What is the orientation of the infant ribs in comparison to adult ribs? What is the implication of this? |
Oriented horizontally, meaning the bucket handle movements of the adult lungs can't occur. Instead, movement is directly out in a piston fashion, which is a less efficient movement and therefore less efficient ventilation results. |
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What is the difference in composition of the diaphragm in the infant and the adult? What is the implication of this? |
The percentage of slow twitch muscle fibres is far less in the infant diaphragm. The implication of this is that the diaphragm is much more easily fatiguable. |
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What is the percentage of slow twitch muscle fibres in an adult, new born and preterm infant? |
Adult = 55% New born = 25% Preterm = 10% |
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How many breaths per minute for: - preterm infants - infants - children - adult |
Preterm: 50-70 breaths Infant: 40 breaths Children: 18-30 breaths Adult: 12-15 breaths |
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How long do infants spend in REM sleep compared to adults? Why is this relevant for respiration? |
Preterms spend 80% in REM sleep vs 20% in adults. REM sleep has irregular respiration and may have apnoea |
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What are the metabolic demands of an infant vs an adult? What is the implication of this? |
Newborn has 2x the rate of oxygen consumption of adults. As a result, infants will progress to hypoxaemia much more quickly. |
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What is collateral ventilation? |
The movement of air between alveoli, through pores of kuhn. |
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What is the difference between Haemoglobin concentration in infant vs adult blood? |
Haemoglobin concentration is higher in infants, therefore higher O2 saturation. O2 dissociation curve moves to left |
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Where is the haemoglobin saturation curve of an infant relative to an adult dissociation curve? |
Infant curve is shifted to the left. Therefore higher saturation in infants. |
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What are the functional implications to consider in infant respiration? |
- higher resistance to airflow (due to narrow airways) - dynamic compression of trachea (due to weak cartilage) - Increased risk V/Q mismatch - Increased work of breathing |
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What are the clinical signs of 6 respiratory distress? |
- Increased respiratory rate - Grunting on expiration - Cyanosis - Nasal flaring - Head bobbing - Apnoea |
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What is the difference between adults and infants in terms of work of breathing? |
Work of breathing much higher in infants - 40% at rest compared to 1-2% of adult |
