Respiratory Session 2- Anatomy, Ventilation & Mechanics Of Breathing Flashcards
What are the 3 parts of the sternum and what do they articulate with?
Manubrium- 1st & part of 2nd costal cartilages
Body- part of 2nd & 3rd-7th costal cartilages
Xiphesternum
What is the sternal angle?
Junction of the manubrium and body- felt as a transverse ridge on palpating of sternum
How do the ribs articulate with the vertebral column posteriorly?
Costovertebral joints
How do the ribs articulate anteriorly?
Ribs 1-7 are connected to the sternum via costal cartilages
Ribs 8-10 articulate with costal cartilage above
Ribs 11-12 end free in abdominal muscles
Describe the 3 main features of a typical rib
Head- 2 articular facets for articulation with vertebra
Tubercle- 1 articular facet for articulation with transverse process of corresponding vertebra
Shaft- thin, flat and curved. Shaft has a costal groove close to its lower border to protect intercostal vessels and nerves
Describe the 2 synovial joints that connect the ribs with thoracic vertebrae
Joint of the rib head- head of rib articulates with body of corresponding vertebra and vertebra above
Cost transverse joint- articular facet on tubercle of rib articulates with transverse process of corresponding vertebra
Name the 3 intercostal muscles
External intercostal
Internal intercostal
Innermost intercostal
Describe the external intercostal muscles
Fibres run downwards and anteriorly from inferior margin of rib above to superior margin of rib below
What movement are the external intercostal responsible for?
Elevation of ribs in ‘bucket handle’ movement to increase anteroposterior and transverse diameters of the chest
Responsible for 30% of chest expansion in quiet respiration
Describe the internal intercostal muscles and how this relates to their function
Fibres run downwards and posteriorly form the rib above to rib below
Action pulls the ribs down from position of chest expansion
Active during forced expiration
Innermost assist with the movement
What are the contents of the neurovascular bundle from above to below?
Intercostal vein
Intercostal artery
Intercostal nerve
Where is the neurovascular bundle found?
In the intercostal groove of the rib, between internal and innermost intercostal muscles
What do the intercostal arteries supply?
Intercostal muscles
Parietal pleura
Overlying skin
Where does the anterior intercostal artery arise from?
Internal thoracic artery and its continuation, the musculophrenic artery
Where does the posterior intercostal artery arise from?
Aorta and intercostal artery
How many intercostal veins per space?
3
2 anterior and 1 posterior
Where do the intercostal veins drain into?
Anterior veins drain via internal thoracic vein into the subclavian vein
Posterior veins drain via azygos vein on the right and hemiazygos vein on the left into SVC
What are the nerve roots of the intercostal nerves and what do they supply?
Anterior rami of thoracic spinal nerves T1-T12
Supply intercostal muscles, parietal pleura and overlying skin
Describe the shape of the diaphragm and its anatomical position
Dome shaped muscle which divides thoracic cavity from the abdominal cavity. Right dome of the diaphragm lies at level of 5th rib and left dome at 5th intercostal space.
What 2 parts does the diaphragm consist of?
Peripheral muscular part
Central tendon
What are the attachment sites of the diaphragm?
Inner aspects of the xiphisternum
Inner aspects of the 7-12 costal cartilages
Arcuate ligaments
Crura of the diaphragm
Where are the openings in the diaphragm and what are they for?
T8- IVC
T10- Oesophagus
T12- Aorta
What is the innervation of the diaphragm and nerve roots?
Phrenic nerve
C3, 4, 5 (keep the diaphragm alive)
What parts does the thoracic cavity consist of?
2 lateral pulmonary cavities and the central mediastinum
What are the 4 compartments of the mediastinum?
Superior
Middle
Anterior
Posterior
What are the contents of the superior mediastinum?
Arch of aorta SVC Vagus nerve Phrenic nerve Thymus Trachea Thoracic duct Muscles Oesophagus
What are the contents of the middle mediastinum?
Heart Ascending aorta Pulmonary trunk SVC L&R phrenic nerves Cardiac plexus Tracheobronchial lymphnodes
What are the contents of the anterior mediastinum?
Loose connective tissue
What are the contents of the posterior mediastinum?
Oesophagus Descending aorta Thoracic duct Azygos system of veins Thoracic sympathetic trunks
Describe the pleura
Serous membrane consisting of a parietal and visceral layer
Visceral lines outside of lungs
Parietal lines inside of each hemithorax and is continuous at the hilum of the lung with visceral pleura
What is the pleural space and its fuction?
Potential space between the 2 layers of pleura lined with pleural fluid to allow the parietal and visceral pleura to slide on one another
What is the blood supply of the pleura?
Parietal- intercostal arteries and internal thoracic arteries
Visceral- bronchial arteries
What is the nerve supply of the pleura?
Parietal- somatic innervation from intercostal and phrenic nerves
Visceral- only autonomic innervation
What are the boundaries of the trachea?
Lower border of the cricoid cartilage and terminates by dividing into right and left main bronchi at sternal angle
Define carina
Angle between left and right bronchi
How is the trachea held open?
18-22 U shaped cartilages
What epithelium is the trachea lined by?
Pseudostratified columnar ciliated epithelium
What are the differences between the left and right bronchi?
Right main bronchus is wider, shorter and more vertical, 2.5cm long
Left main bronchus is 5cm long
Describe the path of the left main bronchi
Passes below arch of aorta, anterior to descending aorta and oesophagus
Describe the bronchial tree
Primary bronchi divide into lobar bronchi for each lobe
Lobar bronchi divide into segmental bronchi
What is a bronchopulmonary segment?
Pyramid shaped area of lung with its apex facing towards helium and base towards lung surface
Each supplied by a segmental bronchus and its own segmental branch of the pulmonary artery and vein
What do the bronchial arteries supply and where do they arise?
Bronchial tree from carina up to the respiratory bronchioles, visceral pleura and connective tissue
Arise from aorta on the left and 3rd intercostal artery on the right
What do the pulmonary veins drain?
Most of the blood supplied by the bronchial arteries and alveoli
What does the superficial group of veins drain and where to?
Visceral pleura and bronchi in the hilar region to azygos vein on the right, and hemiazygous on the left
What does the deep group of veins drain and where to?
Rest of the bronchi (deep in lung) into the main pulmonary vein or directly into left atrium
Where is the apex of the lungs?
Extends above level of 1st rib into the root of the neck
What are the 3 surfaces of the lungs?
Costal surface
Diaphragmatic surface
Mediastinal surface
How many lobes dies each lung have?
Left has 2 (upper and lower)
Right has 3 (upper, middle and lower)
What separates the lobes of the right lung?
Oblique fissure separates upper and middle from lower
Horizontal fissure separates upper and middle lobes
Visceral pleura extends into fissures
Which structures enter the lung via the hilum on the medial surface?
Principal bronchus
Pulmonary artery
2 pulmonary veins
Bronchial vessels, nerves and lymphatics
What do the pulmonary arteries carry and where do they transport it?
Mixed venous blood from RV for gas exchange at alveoli
Do the pulmonary arteries supply the bronchi?
No, but they do supply the alveoli
How is blood supply maintained to lung parenchyma after PE?
Some anastomoses between the bronchial and pulmonary arteries at precapillary and capillary level
Where do the pulmonary veins run?
In intersegmental septa
Where does the nerve supply of the lungs originate?
Vagi and sympathetic trunk via pulmonary plexuses
What function do parasympathetic fibres have in different areas of lung?
Motor to bronchial smooth muscle (bronchoconstrictor)
Inhibitory to pulmonary vessels (vasodilator)
Secretomotor to mucous glands
What are the vagal afferent fibres for?
Cough reflex and some subserving pain
Where is the superficial sub pleural lymphatic plexus found and what does it drain?
Deep to the visceral pleura and drains lung parenchyma and visceral pleura- drain along surface to the hilar lymph nodes to tracheobronchial nodes
Where is the deep bronchopulmonary lymphatic plexus found and what does it drain?
Lies in submucosa of the bronchi and peribronchial tissue and drain to hilar nodes to tracheobronchial nodes
In which direction do the lungs and chest wall recoil?
Lungs recoil inwards and chest wall recoils outwards
Define resting expiratory level
Equilibrium position where the inward force of elastic recoil of the lungs is balanced by the outward recoil of the chest wall- absence of muscular activity
How is the outer surface of the lungs held to the chest wall?
Pleural seal formed by the pleural space filled with pleural fluid
What is the function of the pleural seal?
To ensure chest wall and lungs move together
Define functional residual capacity
The lung volume the exists at the end of expiration
Which muscles contract during inspiration and expiration?
Breathing in from equilibrium- contraction of diaphragm and external intercostal muscles
Breathing out during quiet expiration- only passive recoil of lungs
Breathing out during forced expiration- contraction of abdominal muscles and internal intercostal muscles
Using Boyles law, explain how air flows into lungs during inspiration
Volume of thorax and lungs increases so pressure in lungs falls below atmospheric pressure. Air flows into lungs so alveolar pressure rises back to atmospheric pressure.
Using Boyles law, explain how quiet respiration occurs
Muscle contraction ceases, elastic recoil of lungs causes decrease in volume of thorax and lung so pressure in terminal and respiratory bronchioles rises above atmospheric pressure. Air flows out until alveolar pressure equals atmospheric pressure.
How does exchange of O2 and CO2 occur?
Diffusion between atmospheric air in terminal and respiratory bronchioles and alveolar gas- this maintains normal composition of alveolar gas
What is the pleural pressure and how is this achieved?
Pressure within pleural cavity is negative due to lungs and chest wall recoiling in opposite directions
Does the pleural pressure ever change?
Yes, during inspiration, as chest wall expands pleural pressure becomes more negative
Which muscles are used during forced inspiration?
Sternocleidomastoid and scalene muscles of the neck, serratus anterior and pec major
Define compliance
Sketchiness- volume change per unit pressure change
What is the equation for specific compliance?
Volume change per unit pressure change/ starting volume of lung
What is the source of elastic properties of the lungs?
Elastic tissues in the lungs
Surface tension forces of the fluid lining the alveoli
Why does the surface tension of the lining fluid increase?
Fluid is increased in area as the lungs expand and area of gas-liquid interface always tends to a minimum
What is the function of surfactant?
To reduce surface tension forces of the alveoli
What is surfactant comprised of and how does this relate to where it is found?
Mixture of phospholipids and proteins- hydrophilic ends lie in alveolar fluid and hydophobic end projects into alveolar gas
How does the surface tension of alveolar fluid vary with surface area of alveolus?
As alveolus expands- surface tension of fluid increases
As alveolus shrinks- surface tension of fluid decreases
What is the law of Laplace?
P = 2T/r
P=pressure in alveolus, T=surface tension, r=radius of alveolus
What happens to radius and surface tension as an alveolus expands/shrinks?
As alveolus expands r+T increase
As alveolus shrinks r+T decrease
What are the 3 min functions of surfactant?
- Increases lung compliance by reducing surface tension
- Stabilises the lungs, by preventing small alveoli collapsing into big ones
- Prevents surface tension in alveoli creating a suction force tending to cause transmutation fluid from pulmonary capillaries
What is respiratory distress syndrome?
Seen in premature babies due to lack of surfactant
Surface tension of alveoli high to tend to collapse
What is Poiseuille’s law?
Resistance = pressure/rate of flow
= 8 x viscosity of air x length of tube/ pi x r^2
Where in the respiratory system has the most resistance and why?
Upper respiratory tract due to Poiseuille’s law
The small airways are connected in parallel so resistance is low
How do the airways narrow in asthma?
Inflammatory mediators due to hypersensitivity reaction cause constriction of bronchial smooth muscle and inflammatory swelling of mucosa
How do the airways narrow in COPD?
Excessive mucus in lumen
Breakdown of elastin leading to destruction of alveolar walls so loss of ‘radial traction’ which is the outward tugging action of the alveolar walls on small bronchioles holding them open
