Respiratory System Theme 1

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  • Created by: Splodge97
  • Created on: 21-05-17 13:11
What occurs in emphysema?
Alveoli become larger as a result of smoking breaking down their walls, increasing their SA/V ratio so gas exchange less efficient
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What occurs in fibrosis?
Walls of lung tissue are thickened, increasing the diffusion pathway so gas exchange reduced
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What occurs in cystic fibrosis?
Genetic condition causing excess mucous that is thick and viscous; leads to infection as cilia can't sweep mucous. Large increase in resistance so lungs work harder to ventilate (damaging their tissues).
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What occurs in bronchitis?
Infection irritates and inflames the bronchi, causing them to produce more mucous. The body tries to shift the extra mucous by coughing, which damages the lung tissues.
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What is COPD?
Chronic obstructive pulmonary disease (as in emphysema and bronchitis) where their is a difficulty breathing - expiring especially - as the airways are narrowed and airflow is reduced
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What forms the upper respiratory tract? What is its function?
Pharynx, larynx, vocal cords and nasal cavity. Shape of nose conchae slows the air flow by making it turbulent, so cilia trap more pathogens/debris. Warms and humidifies the air so alveoli not damaged (don't dry out). Also functions in vocalisation.
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What forms the lower respiratory tract? What is its function?
Comprised of trachea, bronchi, bronchioles and alveoli. Allows conduction of air into lungs by stabilising the conducting airways and regulating flow.
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What is the role of the cartilage rings of the trachea?
Incomplete U shaped rings so still protective/prevent collapse whilst still allowing expansion of the oesophagus in peristalsis
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What causes bronchoconstriction?
Local factors like histamine and/or the sympathetic nervous system releasing nor-adrenaline (binds to beta-2 receptors)
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What causes bronchodilation?
Occurs when more CO2 returns to the lungs (plasma CO2 is high). Parasymapthetic nervous system releases Ach (binds to M3 receptors).
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What is the role of the bronchial circulation?
Bronchial arteries supply additional oxygenated blood to the smooth muscle of the bronchioles - lung still functions without it. Bronchial veins remove most of the deoxygenated blood the smooth muscle makes, but not all (some enters pulmonary veins).
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How are alveoli adapted to gas exchange?
Only a single cell layer thick, side facing capillaries leaky (for gas exchange) whilst supporting side is robust and distensible (expands/retracts), has macrophages and a dense capillary network
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Describe type I pneumocytes
Larger, squamous and rounded; fused to the endothelial cell layer of capillaries at the basal membrane, which (along with their thin cytoplasm layer) reduces the diffusion distance.
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Describe type II pneumocytes
Smaller (still rounded), release surfactant (two lipid arms which anneal) to reduce surface tension and prevent the collapse of smaller alveoli
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Describe Wiebel's bronchial tree
Trachea generation 0, then converted to bronchi-->bronchioles-->terminal bronchioles in conductive zone (to 16). Transitional zone (17-19) has roughened respiratory bronchioles. Then true respiratory zone (alveolar ducts 20-22, alveolar sacs 23).
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What is airway resistance?
The force opposing the flow through the airways - is is highest in the bronchioles due to their large SA/V ratio generating friction (so flow slow here). Modelled by Poiseuille's law; increased if flow turbulent, airways inflamed or excess mucous.
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What is the role of the intercostal muscles
Stiffen the intercostal surfaces so thorax size not reduced upon inspiration (enables necessary pressure changes)
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How can all muscles of the thorax aid ventilation?
By straightening the vertebral column to increase thoracic volume
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Describe the external intercostals
Outermost layer. Attach between the tubercles of the ribs behind to the cartilages of the ribs in front (so pass anterio-inferiorly). Anteriorly present as the external aponeurosis.
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Describe the internal intercostals
Middle muscle layer. Attach between the inferior border of the ribs above to the superior border of the ribs below (so pass anterio-superiorly). Anteriorly present as the internal aponeurosis.
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Describe the innermost intercostals
Internal layer, attach to the internal aspect of the ribs above and below (fibres horizontal). Anteriorly present as an aponeurosis.
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Where are intercostal neurovascular bundles present?
In the costal groove of each rib as the intercostal vein, artery and nerve (VAN) between the internal and innermost intercostals
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What is the thoracic inlet?
Borders are the 1st thoracic vertebra, 1st rib and manubrium sterni. Roofed by pleura (projects 2cm above). Transmits the trachea, oesophagus, carotid and subclavian arteries, internal jugular and brachial veins and the phrenic and vagus nerves.
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What is the thoracic outlet?
Closed by the diaphragm, bordered by the body of T12, costal margin and xiphoid process. Transmits the oesophagus, descending aorta, inferior vena cava and the vagus and phrenic nerves.
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How do the ribs cause expansion of the thorax?
Work via a lever action and their arrangement of rings increasing in size to expand in both the transverse and anterior-posterior dimensions
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Which ribs only move slightly?
T1 and T2 (as attached directly to the sternum) and T11 and T12 (as hang free in the abdomen)
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Which ribs form the costal margin?
T8-T10 (cartilages join before connecting to the sternum)
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What are the symphysis joints of the thoracic cage?
Manubriosternal (between manubrium and body of the sternum, forms sternal angle, prevents projection of sternum on inspiration) and xiphisternal joint (between xiphoid process and body of sternum)
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Describe the 1st sternocostal joint
This is perculiar as it is a synchrondrosis (between the notch for the 1st rib on the manubrium sterni and the 1st rib); mainly cartilagenous so strong, preventing disarticulation
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How are the other sternocostal joints arranged?
These are single synovial joints between the ribs and sternum (experienced by T3-T7); T2 expericences a sternocostal joint but it is double, reducing its movement
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What are the vertebro-sternal ribs?
T3-T6, directly attached to the sternum and move by rotation as they have concave necks. Act to increase the anterior-posterior dimensions of the thorax.
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What are the vertebro-chondral ribs?
T7-T10 which are indirectly attached to the sternum via cartilages (though T7 still experiences a sternocostal joint as its cartilage attaches to the sternum directly); move via sliding (as flat necks) to increase the transverse thoracic dimensions.
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What are the interchondral joints?
Synovial joints experienced between the costal cartilages of T8-T10 (where they form the costal margin)
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What are costochondral joints?
Strong synchrondrosis joints between the ribs and the costal cartilages (except T1, T2 (attach directly) T11 and T12 (don't attach))
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What are costovertebral joints?
Two synovial joints between the costovertebral demi-facets of the vertebra and the two facets on the head of the rib. Note T1, T10, T11 and T12 have one joint not two.
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What are costotransverse joints?
Synovial joints between the facet on the rib tubercle and the transverse process of the corresponding vertebra
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Why are joints between the ribs and thoracic vertebra so strong?
Despite shallow facets of transverse vertebra they are held by strong ligaments, so ribs break as opposed to disarticulating
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Where do thoracic joints occur?
As synovial joints between the articular processes of thoracic vertebra and as symphysis joints between vertebral bodies of the thoracic vertebra
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What is the pleural fluid?
Present between the parietal and visceral pleura in the pleural space, allows sliding so the thorax can expand/compress whilst preventing separation of the layers. It is necessary to overcome the low pressures in the thorax upon inspiration.
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What is pneumothorax?
Separation of the pleura by air (when the cut edge of a rib rips the parietal pleura or due to alveolar collapse in emphysema). Repairs in 2-3 weeks as the pressure of the gas is higher than in venous system (diffuses into veins so lung reinflates).
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What is haemostasis?
Blood (or any fluid) accumulates in the pleural space (leads to difficulty inflating/lung collapse
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What is the costodiaphragmatic recess?
Increase in the space between the visceral and parietal pleura at the base of the lung upon expiration
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What is the hilum?
Area where vessels enter and leave the pleural cavity; on the posterior surface of the lung it is viewed as the opening for the bronchus (around which the broncial vessels enter/lymph nodes lie) and the pulmonary arteries/veins
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How is the left lung divided?
Into an upper and lower lobe by an oblique fissure (follow the line of the 6th rib)
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How is the right lung divided?
Oblique and horizontal (following the 4th cartilage to meet the oblique) fissures split it inuto upper, middle and lower lobes
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Describe the course of the pleura
Extend 2cm above clavicle, pass behind sternoclavicular joint, meet at sternal angle (2nd cartilage). Extend to 4th cartilage, left forms cardiac notch (right continues to 6th cartilage). Both narrow to lung apex (10th rib) then level of 12th rib.
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What lines do the ppleaura cross as they narrow past the 6th cosstal cartilage?
Mid-clavicular line at the 8th rib, mid-axillary line at the 10th rib and mid-scapular line at the 12th rib
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What are bronchopulmonary segments?
Divisions of the lungs seen in cadavers which lave seperate innervations, vessels and bronchi; could be transplanted but not often as not seen in life
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How does intrapleural pressure vary along the lung? Why?
Usually negative as elastic properties of ribcage and recoil of lung generate a negative pressure. However, -4mmHg at apex and -2mmHg at base as effect of gravity on lung weight changes along its length.
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Wht is their no air movement at the end of expiration?
Pressure of the atmosphere and in the alveoli equal (though intrapleural pressure lower); there is therefore a balance between the elastic recoil of the chest wall and lung
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How much air is intaken in quiet ventilation?
1/2 litre 12 times a minute - increases in vigorous resporation, then to 41L a minute (in 20 breaths) when depth of breathing increased against resistance
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What occurs in inspiration?
Diaphragm flattens, external intercostal raise and the interchondral part of the internal intercostals contracts. If forced accessory muscles (scalenes, infrahyoids, quadrus lumborum) recruited. Decreases IPP to -8mmHg so alveoli expand/air enters.
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What occurs in expiration?
Largely passive in quiet breathing (via recoil); interosseous internal intercostals pulls ribs down. If forced abdominal muscles, quadrus lumborum and innermost intercostals contract. Increases IPP to -1mmHg so alveoli deflate/air exits.
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How do we perform vocalisation?
Quick, deep inspiration followed by an extended expiration (by holding back air pressure then contracting abdominals to release) to vibrate the larynx
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What is Boyles law?
States an increase in volume is followed by a decrease in pressure and vice versa; it is modelled by P1xV1=P2xV2
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What is lung compliance?
The distensibility of the lungs, defined as a volume change produced by a pressure change (calculated by volume change/pressure change). In healthy lungs high then decreases as collagen of lungs fixed length. High in enphysema, low in fibrosis.
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What is surface tension?
Elastic tendancy of a fluid surface (air) to acquire the least surface area possible; modelled by P=2T/r. Means without surfactant smaller alveoli would deflate as air moves into larger alveoli along pressure gradient.
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Why can the alveoli not withstand surface tension in emphysema?
As alveoli enlarged force withstood by a single alveolus rather than multiple alveoli so rupture/collapse occurs as pressure not as well distributed. Great force to reinflate often causes pneumothorax.
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What is newborn respiratory distress syndrome?
When premature babies (before 22-23 weeks) don't produce enough surfactant so their alveoli collapse, don't have enough energy to re-inflate; lungs bathed in synthetic surfactant to prevent death.
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What is tidal volume?
Volume expelled from the end of a normal inspiration to the end of a normal inspiration; 500ml in both men and women
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What is expiratory reserve volume?
The maximum volume removed from the lungs during forced expiration below that which is normally removed
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What is inspiratory reserve volume?
The maximum volume which can be taken into the lungs upon forced inspiration above that which is normally inhaled
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What is residual volume?
The volume remaining in the lungs after maximum forced expiration
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What is functional residual capacity?
This is the volume remaining in the lungs at the end of a normal expiration
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What is inspiratory capacity?
The maximum volume which can be taken into the lungs upon forced inspiration, taking into account all the volume gained from normal expiration
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What is vital capaity?
The volume expelled from the lungs in maximal forced expiration followed by maximal forced inspiration
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What is total lung capacity?
The total volume of air in the lungs upon maximal forced inspiration
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What is FEV1 (forced expired volume in one second)?
The maximum loss of volume in the first second of maximal forced expiration (after forced inspiration). If healthy, >70% of vital capacity removed; lower in obstructive disease as harder to deflate quickly (but FVC normal as inspiration same).
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What is forced vital capacity (FVC)?
The total amount of air exhaled during the FEV test (in forced inspiration then expiration); the time for this is measured. It is reduced in restrictive lung disease as normal inspiration difficult (less to exhale), but FEV1 normal as expire easily.
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