Anatomy Flashcards
How thick is the respiratory membrane?
0.5 - 1 micrometre thick
Basic nasal structural anatomy
- Based on what type fo structure? Supported by? 2
Covered in?
- Basic structural anatomy: Cartilaginous structure, supported by hyaline cartialge and nasal bones. Beyond the vestibule of the nostrils, some anterior skin transitions into a respiratory mucous epithelium at the mucocutaneous junction
3 areas in the nasal cavity? Where are they in relation to each other?
◦ Vestibular area, lined by skin (extends 1cm into the cavity)
◦ Respiratory area, lined by respiratory mucous membrane with pseudostratified ciliated columnar epithelium. Contains the three concha which project into the cavity.
◦ Olfactory area, at the roof of the cavity (lower boundary is the superior conchae)
Relations of the nasal cavity
◦ Floor of the nose is the roof of the mouth
◦ Roof is the narow junction of the lateral walls
◦ Lateral wall superiorly is the medial wall of the orbit
◦ Lateral wall inferiorly is the medial wall of the maxillary sinus
◦ Medial wall is the septum
Blood supply of the nasal cavity?
◦ sphenopalatine artery (terminal branch of the maxillary artery)
◦ septal branch of the superior labial artery
◦ ascending branch of the greater palatine artery
◦ All of these come together into an anastomosis in the lower anterior septum (Little’s area), which is called Kieselbach’s Plexus (where epistaxis commonly occurs)
Lymphatic drainage of the nose?
Submandibular, deep cervical, retropharyngeal nodes
Innervation fo the nasal cvity?
Infraorbital nerve (bestibular, olfactory to olfactory, and multiple nerves to respiratory area
Function of the nasal cavity 4
◦ Humidification and warming of inspired air
◦ Reclamation of expired moisture and heat
◦ Olfaction and sense information about air temperature
◦ Speech (nasalisation)
◦ Sneezing (protective reflex)
How long is the pharynx
12cm
Walls of the pharynx have 4 layers
‣ mucous membrane
‣ submucous layer (or fibrous layer)
‣ muscular layer
‣ buccopharyngeal fascia
What level does the oesophagus start
C6
What si the posterior relation of the pharynx?
◦ Posteriorly: slides freely along the prevertebral fascia (separated by the retropharyngeal potential space)
Surface anatomy of the larynx
Adams apple or larygneal prominence is the thyroid cartilage
Cricothyroid membrane easily palpable
What lines the larynx?
◦ Lined by pseudostratified columnar ciliated epithelium
Relations of the larynx
◦ Superiorly: bounded by the hyoid bone - thyrohyoid membrane and muscle suspend the larynx
◦ Anteriorly, covered by skin and protected by the thyroid cartilage
◦ Inferiorly: becomes continuous with the trachea at the level of C6
◦ Posteriorly: projects into the laryngopharynx
Where vertebrally does the larynx become the trache
C6
Laryngeal inlet faces what direction?
Backwards and upwards
What binds the laryngeal inlet anteriorly
Epiglottis
What binds the laryngeal inlet laterallly and posteriorly
Aryepiglottic folds
◦ Ary-epiglottic fold - lateral epiglottis –> arytenoid cartilages fold of mucosa forms the laryngeal inlet
‣ Round bump on either side is the cuneiform cartilage, with the arytenoids medially to this
‣ The laryngeal inlet is often depicted from an oblique angle
What binds the laryngeal inlet posteriorly
Interarytenoid fissure
What is the vallecula?
◦ Vallecula - 2x reflections of mucosa, with medial and lateral epiglottic folds
What is the vestibular fold
Mucosal fold over the vestibular ligament, false vocal ligament
What divides the infraglottic and supraglottic space? What type of epithelium lines it? Why is this relevant?
‣ The larygneal vestibule is this space - the vestibule is the space between the two folds, the infraglottic space and supraglottic space are either side of the vestibule
* Supraglottic space - respiratory epithelium with mucous
* The laryngeal saccule releases secretions into this space to lubricate the vocal folds
What is the vocal fold
Mucosal fold over the vocal ligament
What does the vocal cord attach to
Thyroid cartilage at anterior commisure, and the posterior commisure is mobile as the vocal folds attach tot he arytenoids which can abduct and adduct
What is the space between the vocal cords called
rima glottidis
What lines the vocal folds
free edge stratified squamous epithelium
What is the blood supply to the larynx
◦ Upper half: superior laryngeal branch of the superior thyroid artery
◦ Lower half: inferior laryngeal branch of the inferior thyroid artery
What si the veinous drainage to the larynx
◦ Upper half: superior laryngeal veins which empty into the superior thyroid veins
◦ Lower half:inferior laryngeal veins to the inferior thyroid veins, which drain into the brachiocephalic veins
What is the lymphatic drainage to the larynx
◦ upper and lower groups of deep cervical nodes
What are the 3 paired cartilages
arytenoid, corniculate and cuneiform
What are the 3 unpaired cartilages
epiglottis, thyroid and cricoid
Where do the arytenoid cartilages sit? Articulate with? Major attachements 2
‣ Arytenoids - sit superior to cricoid and base which articulates with cricoid , vocal process anteriorly, and posterior process for cricoarytenoid muscules
Corniculate cartilage sites where
horns on top of the arytenoids
Cuneiform cartilages sit where
Suspended in the quadrangular membrane
The bump in the aryepioglottic fold
Epiglottis joins what structure? Major ligaments 2
leaf like structure connected to posterior portion of the anterior ring of the thyroid by thyro-epiglottic ligament. Also joined to the hyoepiglottic ligament
Cricoid cartilage significant structural features
‣ Cricoid - complete ring, narrow anterior arch, posterior cricoarytenoid ligaments, synovial joint circothyroid joint with joint capsule and ligaments
What is the laryngeal skeleton composed of
‣ Hyoid bone - attachment for epiglottis and strap muscules
‣ Thyroid cartilage - anterior attachment of vocal folds, posterior articulation with cricoid cartilage
‣ Cricoid cartilage - signet ring shaped, articulates with thyroid and arytenoid cartilage
‣ Arytenoids - two cartilages which glide along the posterior circoid and attach to posterior ends of vocal folds
Intrinsic ligaments 2
cricothyroid ligament and quadrangular membrane
Extrinsic ligaments 4
thyrohyoid membrane, median and lateral thyrohyoid ligament, hyo-epiglottic ligament, cricotracheal ligament.
Intrinsic muscles to the larynx
Cricothyroid
Thyroarytenoid
Posterior and lateral cricoarytenoid
Transverse and oblique arytenoids
Innervation of the larynx
‣ recurrent laryngeal nerve - sensation of subglottis, motor fibres to intrinsic fibres
* branches fromt he vagus in the mediastinum then turns back up the neck, on the right it travels inferior to the subclavian artery and on the left the aorta
‣ Superior laryngeal nerve - sensation of the glotttis and supraglottis, motor fibres of the cricthyroid muscle which tenses the vocal folds, leaves the vagus high in the neck. It has a smaller external branch which supplies the cricothyroid muscle on the external surface
Distribution of the recurrent laryngeal nerve to the larynx
‣ recurrent laryngeal nerve - sensation of subglottis, motor fibres to intrinsic fibres
* branches fromt he vagus in the mediastinum then turns back up the neck, on the right it travels inferior to the subclavian artery and on the left the aorta
‣ Superior laryngeal nerve - sensation of the glotttis and supraglottis, motor fibres of the cricthyroid muscle which tenses the vocal folds, leaves the vagus high in the neck. It has a smaller external branch which supplies the cricothyroid muscle on the external surface
Distribution of the nervous supply of the superior laryngeal nerve
‣ recurrent laryngeal nerve - sensation of subglottis, motor fibres to intrinsic fibres
* branches fromt he vagus in the mediastinum then turns back up the neck, on the right it travels inferior to the subclavian artery and on the left the aorta
‣ Superior laryngeal nerve - sensation of the glotttis and supraglottis, motor fibres of the cricthyroid muscle which tenses the vocal folds, leaves the vagus high in the neck. It has a smaller external branch which supplies the cricothyroid muscle on the external surface
What is the purpose of the larynx 5
◦ Respiration (conductive airway)
◦ Swallowing - prevneting aspiration
◦ Phonation
◦ Cough reflex
◦ Valsalva
What is the pharyngeal dilator reflex? Why is it relevant? What is the receptor? What is the afferent? What is the most important effector?
◦ During inspiration as the upper airway pressure drops secondary to intra-thoracic pressure drop by a few cm H20 and the upper airway would collapse without any support
◦ This coordinated muscle contraction is called the pharyngeal dilator reflex
‣ arc is activeated by mucosal strentch receptos responding to negative intrapharyngeal pressure
‣ Trigeminal, superior laryngeal and glossopharyngeal reflex afferents
‣ Genioglossus is the most important effector
Paediatric airway differences
- Bone 2
- Larger features 3
- Laryngeal opening 1
- Trachea 3
How wide is the trachea
2cm
How long is the trachea?
How much is in the chest?
- A fibrocartilaginous tube 10cm long, approx 5cm in neck and 5cm in the thorax
How high can the liver be in the chest wall?
- Liver right - at its superior edge can be at the level of the nipple with the lower margin from above the tenth rib on the right to the nipple on the left.
How high can the spleen be on the chest wall?
- Spleen left - relative to the 9th-11th ribs underneath the left part of the diaphragm
Where does the diaphragm arise from?
◦ Lumbar and arcuate ligaments, costal cartilages of ribs 7-10 (directly to ribs 11 and 12), and xiphoid process of the sternum
◦ Right crus - arises from L1-3
◦ Left crus arised from L1-2 and their intervertebral discs
◦ When fully relaxed moves upwards and the upper limits of normal are - 4th intercostal space for right dome, 5th intercostal space fo left dome, xiphisternum centrally, when contracted approximates tendinous origins
Where can the diaphragm sit at its most superior
◦ Lumbar and arcuate ligaments, costal cartilages of ribs 7-10 (directly to ribs 11 and 12), and xiphoid process of the sternum
◦ Right crus - arises from L1-3
◦ Left crus arised from L1-2 and their intervertebral discs
◦ When fully relaxed moves upwards and the upper limits of normal are - 4th intercostal space for right dome, 5th intercostal space fo left dome, xiphisternum centrally, when contracted approximates tendinous origins
What order are the artery, vein and nerve in for intercostals?
Superior to inferior
Vein
Artery
nerve
Which artery/vein runs along the anterior traceho sometimes
- Branches of the superior thyroid artery run along the superior aspect of the thyroid isthmus anterior to the trachea
- Anterior jugular veins are often connected by a vein that runs superficially across the lower neck
Tracheal course - origin, termination anatomically
- Larynx connects to the superior part of the trachea at C6 into the thorax and terminates at the level of the sternal angle, where it divides into the right and left mainstem bronchi.
- Initially anterior, then moves posteriorly as it descends to move behind the sternal notch
How many rings are there in the trachea
18-22
Describe the structure of tracheal rings
Incomplete fibrocartilagenous rings
What joins the incomplete tracheal rings together
- The tracheal rings are joined by fibroelastic tissue.
- They are deficient posteriorly where the trachea lies anterior to the oesophagus; the posterior gap is spanned by the involuntary smooth trachealis muscle
Relationships of the laryngx
- Superior - cricoid cartilage
- Lateral - carotid sheaths (common carotid arteries, vagus and internal jugular veins), thyroid lobes, inferior thyroid arteries, posterolaterally either side of the oesophagus are the recurrent laryngeal nerves (posterior to the sheath)
- Inferior to the isthmus of the thyroid gland are the inferior thyroid veins
- Posterior – oesophagus, vertebral column
- Posterior - oesophagus
Draw a face on view of the inbtubation view and label
Innervation of the larynx internally
- Glossopharyngeal - sensory posterior third of the tongue, calculated and anterior surface of the epiglottis
- Larynx innervated by the vagus - recurrrent laryngeal and superior laryngeal innervation
◦ Posteiror epiglottis is from superior laryngeal
◦ The airway itself below the glottis is the RLN
Sagital diagram of anatomy relevant to intubation
What anatomical location distinguishable on a radiograph indicates where the trachea bifurcates
C6
At full inspiration does the trachea move?
move down by 5cm and the length stretches
What are the layers of the tracheal microanatomy
- Mucous
- Lined with pseudostratified columnar ciliated epithelium and goblet cells
◦ Mucous glands branch off the main lining as dead ends
◦ Pseudostratigied because nuclei positioned at different depths in the cell - Lamina properia connective tissue
◦ Within which mast cells, deep mucous glands reside - Perichondrium
- Hylaline cartilage
Superior boundary of the trachea
cricoid
Blood supply of the trachea
Blood supply:
* Inferior thyroid and bronchial arteries (bronchial arteries supply the walls of the large airways)
* Veinous drainage - inferior thyroid plexus
* Lymphatic drainage - to posteroinferior group of deep cervicalnodes and to paratracheal nodes
Innervation fo the trachea
Innervation - vagus and T2-6 sympathetic chain
* Sensory: fibres from the vagi and recurrent laryngeal nerves
* Sympathetic fibres from upper ganglia of the sympathetic trunks supply the smooth muscle and blood vessels.
* Trachealis muscle is innervated by the vagus
How many generations of cartilagenous bronchi are there?
4
When there is no cartilage to an airway what is it then called
bronchiole
How many bronchiole generations are there
5 - 14
After bronchioles what is the next generation of conducting airways
Respiratory bronchioles from generation 15 -18
Some gas exchange
What are the respiratory portions of the airways
Respiratory bronchioles starting at generation 15 - 18
Alveolar ducts generation 19 -22
Alveolar sacs gen 23
Where does innervation of the airways come from
- Innervated by the vagus and T2-6 sympathetic fibres
Describe the anatomical progression of the right main bronchus
◦ RUL bronchus takes off anterolaterally - divides into 3
‣ Anterior
‣ Posterior
‣ Apical (upper point of triangle)
◦ Bronchus intermedius from RUL take off to RML take off
‣ RML - takes off anteromedially
* Medial segment
* Lateral segment
‣ RLL
* Superior RLL - at the level of the RML bronchus on the far right
* Medial basal segment - medial take off
* RLL bronchus continues caudally
◦ Basallar segmental bronchi
‣ Anterior
‣ Lateral
‣ Posterior
Describe the path of the left main bronchus
- Left - breaks from the carina more acutely, 2x longer, runs more horizontal
◦ Upper lobe - branches anterolaterally from the left main stem. Branches into 3
‣ Lingula - the most rightward on entering (upwards is anterior). Branches into
* Inferior
* Superior
‣ Anterior - middle
‣ Apicoposterior
◦ Lower lobe
‣ Superior segment - takes off Posteriorly just beyond the LUL bronchus
* Can be difficult to enter
‣ Then divides
* Anteromedial
* Lateral
* Posterior
Bronchial artery sypply
◦ Bronchial arteries (three: two on the left coming off the aorta, and one on the right coming off the third right posterior intercostal artery).
◦ The smallest airways (from respiratory bronchioles down) also receive blood supply from the pulmonary arteries and veins
Bronchial veinous supply
◦ Veins are collateral with the arteries,
◦ Drainage is to bronchial veins; eg. veins of the right lung drain to the azygos vein and those of the left to the accessory hemiazygos vein.
For each bronchus how many bronchi does it break into
2
What is the model of generations of airways called
Weibel model
Generation weibel zero
trachea
When does the respiratory weibel zone start
16 terminal bronchioles
How much air is in the conducting airways at any one time
150mls between zone 0 - zone 15
How much air is in the respiratory zone at any one time
3L between weibel zone 15 and 23
3 branches of the respiratory zone
Respiratory bronchiole
Alveolar ducts
Alveolar sacs
What is an acinus
A functional unit of an airway
From Weibel zone 15 and airway is an acinar airway
What lines bronchial airways
- The bronchial airways are lined by pseudostratified columnar ciliated, with mucous glands, and the walls contain cartilaginous rings.
How wide is a bronchiole
1mm
How do we know when respiratory bronchioles start
No longer lined by cilia
What is the function of the mucociliary elevator?
Clearing material from the lower airways
What is mucous
◦ 97% water, 3% mucin a glycoprotein which is 90% carbohydrate and highly anionic
◦ When well hydrated the mucin slides politely along each other but with dehydration it becomes viscous, sticky and elastic preventing clearance
◦ Average daily production 18-36ml/day
4 Macrostructural elements of an alveolus and how it affects function
- 500 million alveoli forming spherical structures in distension and polyhedral spaces with pleated folds in collapse –> maximising surface area for diffusive gas transfer
- Alveolar size decreases in distal areas account for slower rate of diffusion of gas to distal airways
- Alveoli are interconnected via Pore of Kohn which are defects in the septae of the walls allowing equalisation of pressure and gas flow to maximise V/Q condcordance and maximise recruitment for gas exchange
- Interconnected network of walls share emchanical stresss across a large surfaece area of lung parenchyma assisting elastic recoil, resisting collapse through alveolar interdependence
Alveoli microstructure vs function
- Minimising diffusion distance - Respiratory membrane of alveoli 1/3 of a micrometre - very thin trilamellar membrane
- Capillaries have their thinner layer on alveoli side AND Blood vessels encase the alevoli as sheets maximising the proximity to diffusion
- Maximises diffusion (Ficks law)
- Basal lamina with extracellular matrix and interstitium with type 4 collagen contributing to the strength while maintaining amximal thinness - On the non blood/aveolar membrane area the basal lamina is thicker with elastic and collagen fibres from hilum along bronchial to alveolar ducts maximising strength and elasticity of lung tissue architecture
- The elasticity allows for utilisation of potential energy –> reducing work on expiration - Avoiding alveolar fluid transfer
- Lipid bilayer of alveolar of alveolar cells membranes reducing permeability of alveoli to water
- Pulmonary lymphatic drainage faciliated by low intrathoracic pressures, lower pulmonary vascular bed pressures - Surfactant production
- type 2 pneumocytes rings of microvilli secreting surfactant to reduce surface tension avoiding collapse and atelectasis which worsens V/q mismatch
- Optimises ventilation via improving compliance
- Reduces work of breathing
5/. Alveolar macrophages
Describe type 1 pneumocutes
‣ central small nucleus and then spreading protoplasmic extensions/extended cytoplasm plates with no organelles
‣ Barrier function with tight junctions - poor water solubility
‣ High permeability to gasses
‣ The main cell for the structure of the alveoli.
‣ Minimal metabolism
How is the respiratory membrane optimised for gas diffusion
- Minimising diffusion distance - Respiratory membrane of alveoli 1/3 of a micrometre - very thin trilamellar membrane
- Capillaries have their thinner layer on alveoli side AND Blood vessels encase the alevoli as sheets maximising the proximity to diffusion
- Maximises diffusion (Ficks law)
- Basal lamina with extracellular matrix and interstitium with type 4 collagen contributing to the strength while maintaining amximal thinness - On the non blood/aveolar membrane area the basal lamina is thicker with elastic and collagen fibres from hilum along bronchial to alveolar ducts maximising strength and elasticity of lung tissue architecture
- The elasticity allows for utilisation of potential energy –> reducing work on expiration - Avoiding alveolar fluid transfer
- Lipid bilayer of alveolar of alveolar cells membranes reducing permeability of alveoli to water
- Pulmonary lymphatic drainage faciliated by low intrathoracic pressures, lower pulmonary vascular bed pressures - Surfactant production
- type 2 pneumocytes rings of microvilli secreting surfactant to reduce surface tension avoiding collapse and atelectasis which worsens V/q mismatch
- Optimises ventilation via improving compliance
- Reduces work of breathing
5/. Alveolar macrophages
Type 2 pneumocytes
‣ Ring of microvilli
‣ Holes through which it secretes surfactant —>reducing surface tension on alveolar walls and preventing collapse (stored in lamellae bodies)
‣ Stem cells for type 1 pneumocytes - cannot themselves replicate
Dry mass composition of surfactant
◦ 85-90% is phospholipid
‣ DPPC/lecithin - dipalmoitoyl phosphatidylcholine 2/3 of content ; then heterogenous group and contribute to the stability and solubility in water
‣ Hydrophilic head, hydrophobic tail - aligning themselves in monolayers on interior alveolar surface with hydrophilic heads buried in the water and the hydrophobic tail chains pointing out into the airspace of the alveolus reducing intermolecular forces
◦ 8-10% is protein - mainly SP proteins A B and C, all small (~4-5 kDa )
◦ 2-5% is neutral lipid, eg. cholesterol
Carbohydrate
Specific surfactant proteins
What is the dominant lipid in surfacant
◦ 85-90% is phospholipid
‣ DPPC/lecithin - dipalmoitoyl phosphatidylcholine 2/3 of content ; then heterogenous group and contribute to the stability and solubility in water
‣ Hydrophilic head, hydrophobic tail - aligning themselves in monolayers on interior alveolar surface with hydrophilic heads buried in the water and the hydrophobic tail chains pointing out into the airspace of the alveolus reducing intermolecular forces
◦ 8-10% is protein - mainly SP proteins A B and C, all small (~4-5 kDa )
◦ 2-5% is neutral lipid, eg. cholesterol
Carbohydrate
Specific surfactant proteins
What is the dominant substance in surfactant
◦ 85-90% is phospholipid
‣ DPPC/lecithin - dipalmoitoyl phosphatidylcholine 2/3 of content ; then heterogenous group and contribute to the stability and solubility in water
‣ Hydrophilic head, hydrophobic tail - aligning themselves in monolayers on interior alveolar surface with hydrophilic heads buried in the water and the hydrophobic tail chains pointing out into the airspace of the alveolus reducing intermolecular forces
◦ 8-10% is protein - mainly SP proteins A B and C, all small (~4-5 kDa )
◦ 2-5% is neutral lipid, eg. cholesterol
Carbohydrate
Specific surfactant proteins
What is the structure of DPPC
◦ 85-90% is phospholipid
‣ DPPC/lecithin - dipalmoitoyl phosphatidylcholine 2/3 of content ; then heterogenous group and contribute to the stability and solubility in water
‣ AMPHIPATHIC Hydrophilic head (charged choline head), hydrophobic tail - aligning themselves in monolayers on interior alveolar surface with hydrophilic heads buried in the water and the hydrophobic tail chains pointing out into the airspace of the alveolus reducing intermolecular forces
◦ 8-10% is protein - mainly SP proteins A B and C, all small (~4-5 kDa )
◦ 2-5% is neutral lipid, eg. cholesterol
What does DPPC satnd for?
◦ 85-90% is phospholipid
‣ DPPC/lecithin - dipalmoitoyl phosphatidylcholine 2/3 of content ; then heterogenous group and contribute to the stability and solubility in water
‣ Hydrophilic head, hydrophobic tail - aligning themselves in monolayers on interior alveolar surface with hydrophilic heads buried in the water and the hydrophobic tail chains pointing out into the airspace of the alveolus reducing intermolecular forces
◦ 8-10% is protein - mainly SP proteins A B and C, all small (~4-5 kDa )
◦ 2-5% is neutral lipid, eg. cholesterol
What protein in is surfactant
◦ 8-10% is protein - mainly SP proteins A B and C, all small (~4-5 kDa )
4 specific proteins have been found
- SP - A - D
SP B and C are hydrophobic proteins that spread phsopholipids into a monolayer lining the alveoli
SPA and SPD are more hydrophilic
- Facilitate the spread action of SPB by promoting the breakup of secreted lamellae bodies
- Preventings plasma protein entry into alveolar fluid
- ENhanced macrophage activity
- Regulating surfactant turnover by endhancing uptake and inhibiting secretion of phsopholipids by type 2 cells
What are the 4 functions of lung surfactant
- Surface tension and the Law of Laplace:
◦ Surface tension is the force of attraction between liquid molecules at the liquid-gas interface, expressed in Newtons per meter, which tends to minimise surface area.
◦ The surface tension of the alveolar fluid, in its tendency to minimise surface area, is a force promoting the collapse of the alveolus - it is reduced by heat, and increased when intermolecular forces are stronger
◦ The relationship of this force to sphere size is described by the Law of Laplace.
‣ P = 2γ/r
‣ States that the pressure difference between the inside and the outside of an elastic sphere (“Laplace pressure”) is inversely proportional to the radius, proportional to surface tension
‣ γ is the surface tension - Consequences of Laplace’s law for alveoli
◦ Smaller partially deflated alveoli will have lower compliance and higher Laplace pressure at any given surface tension –> more prone to collapse emptying into neighbouring larger alveoli
◦ Alveolar surface tension adds to the pulmonary capillary hydrostatic gradient (i.e. it promotes the ultrafiltration of oedema fluid) - Effects of surfactant
◦ Alveolar surface tension decreases virtually to zero, particularly when alveoli deflate and phospholipid particles are brought closer together (At the very least when measured it causes 1/2 surface tension, and its effects become greater in smaller alveoli where particles are closer together) - preventing collapse at low volumes, reducing work of breathing
◦ When the alveoli are fully inflated, surfactant phospholipid molecules are farther apart and surface tension rises preventing overdistension
◦ It produces hysteresis - as compliance varies with volume as a consequence of surfactant concentration at the airlung interface being higher at lower volumes - Increased lung compliance results from decreased surface tension
◦ Decreased surface tension results in a decreased capillary-alveolar hydrostatic pressure gradient, decreasing ultrafiltration of fluid
Explain the law of laplace and how surfactant affect this
- Surface tension and the Law of Laplace:
◦ Surface tension is the force of attraction between liquid molecules at the liquid-gas interface, expressed in Newtons per meter, which tends to minimise surface area.
◦ The surface tension of the alveolar fluid, in its tendency to minimise surface area, is a force promoting the collapse of the alveolus - it is reduced by heat, and increased when intermolecular forces are stronger
◦ The relationship of this force to sphere size is described by the Law of Laplace.
‣ P = 2γ/r
‣ States that the pressure difference between the inside and the outside of an elastic sphere (“Laplace pressure”) is inversely proportional to the radius, proportional to surface tension
‣ γ is the surface tension - Consequences of Laplace’s law for alveoli
◦ Smaller partially deflated alveoli will have lower compliance and higher Laplace pressure at any given surface tension –> more prone to collapse emptying into neighbouring larger alveoli
◦ Alveolar surface tension adds to the pulmonary capillary hydrostatic gradient (i.e. it promotes the ultrafiltration of oedema fluid) - Effects of surfactant
◦ Alveolar surface tension decreases virtually to zero, particularly when alveoli deflate and phospholipid particles are brought closer together (At the very least when measured it causes 1/2 surface tension, and its effects become greater in smaller alveoli where particles are closer together) - preventing collapse at low volumes, reducing work of breathing
◦ When the alveoli are fully inflated, surfactant phospholipid molecules are farther apart and surface tension rises preventing overdistension
◦ It produces hysteresis - Increased lung compliance results from decreased surface tension
◦ Decreased surface tension results in a decreased capillary-alveolar hydrostatic pressure gradient, decreasing ultrafiltration of fluid
Explain the law of laplace
P = 2gamma / T
- γ is the surface tension
- r is the radius of the spherical alveolus, and
- P is the Laplace pressure, or the pressure difference between the inside and the outside of the curved fluid surface, i.e. the difference in pressure between the fluid layer and the gas inside the sphere.
◦ at any given surface tnesion smaller spheres with smaller radii have higher transmural pressures and want to collapse
‣ Smaller alveoli are more difficult to inflate than large alveoli - low compliance at small lung volumes
‣ Smaller alveoli are prone to collapse by emptying into larger neighbouring alveoli
‣ Filtration of fluid across the pulmonary membrane depends on hydrostatic pressure gradient - alveoli surface tension adds to that (promotes ultrafiltration of oedema fluid)
Give the equation for pressure related to surface tension
P = 2surface tension/radius
What is the primaru component of the dry mass of surfactant?
Dipalmitoyl Phosphatidylcholine
‣ Hydrophilic head, hydrophobic tail - aligning themselves in monolayers on interior alveolar surface with hydrophilic heads buried in the water and the hydrophobic tail chains pointing out into the airspace of the alveolus reducing intermolecular forces
Define surface tension
◦ Surface tension is the force of attraction between liquid molecules at the liquid-gas interface, expressed in Newtons per meter, which tends to minimise surface area.
What doe surface tension do in the alveolus
◦ The surface tension of the alveolar fluid, in its tendency to minimise surface area, is a force promoting the collapse of the alveolus - it is reduced by heat, and increased when intermolecular forces are stronger
Define the law of Laplace
‣ States that the pressure difference between the inside and the outside of an elastic sphere (“Laplace pressure”) is inversely proportional to the radius, proportional to surface tension
What effect does the law of laplace have for smaller alveoli
◦ Smaller partially deflated alveoli will have lower compliance and higher Laplace pressure at any given surface tension –> more prone to collapse emptying into neighbouring larger alveoli
◦ Alveolar surface tension adds to the pulmonary capillary hydrostatic gradient (i.e. it promotes the ultrafiltration of oedema fluid)
What si the alveolar surface tension in the context of surfactant? What happens as alveoli collapse? When is it most effective?
◦ Alveolar surface tension decreases virtually to zero, particularly when alveoli deflate and phospholipid particles are brought closer together (At the very least when measured it causes 1/2 surface tension, and its effects become greater in smaller alveoli where particles are closer together) - preventing collapse at low volumes, reducing work of breathing
When is surfactant least effective
When alveoli are fully inflated surfactant molecules are farther apart and surface tension rises –> produces hysteresis
Draw a pressure volume curve for the lung illustrating compliance and hysteresis
Surfactant is created how?
- Preformed surfactant is stored in the lamellar bodies inside the Type 2 cells; these are bell-shaped structures which, upon sectioning, reveal a concentric internal structure like an onion. These bodies have a relatively acidic internal pH and also contain some surprisingly lysosomal enzymes, eg. hydrolases.
- Lamellar bodies appear in Type 2 cells at around the 20th week of gestation
- Each cell has about 150 lamellar bodies, and about 15 of these are exocytosed every hour
Release of surfactant is increased by 4
Catecholamines (Beta)
Cholinergic drugs
Vasopressin
Adenosine
Release of surfactant is inhibited by
◦ High concentrations of surfactant proteins
◦ Lectins (eg. plant lectin), which are homologous with surfactant proteins
◦ Inflammatory mediators
How long does surfactn last
half life of 5-10 hours
Each hour 10-30% of surfactant is removed
How is surfactant turned over/removed? 5
◦ Resorption into Type 2 cells (this accounts for 95% of the removal)
◦ Transport up the airways and elimination as exhaled aerosol
◦ Degradation in alveolar macrophages
◦ Extracellular enzymic degradation in the alveoli
◦ Clearance via lymph or blood
* Alveolar proteinosis is overproduction of surfactant
What is the most important pharyngeal muscle in elevating the hyoid and base of tongue?
Genioglossus
What inspiratory function do pharyngeal muscles have? What is this called?
Dilate the upper airway as a reflex response to negative pressure
◦ As during inspiration as airway pressure becomes negative this soft musclular tube may collapse - therefore their contraction maintains airway patency by contraction
◦ Pharyngeal dilator reflex - mediated by stretch receptors in upper airway via trigeminal, superior laryngeal and hypoglossal nerves
What si the pharyngeal dilator reflex
Dilate the upper airway as a reflex response to negative pressure
◦ As during inspiration as airway pressure becomes negative this soft musclular tube may collapse - therefore their contraction maintains airway patency by contraction
◦ Pharyngeal dilator reflex - mediated by stretch receptors in upper airway via trigeminal, superior laryngeal and hypoglossal nerves
What do laryngeeal muscles do on inspiration and expiration?
- Vocal cords abduct to decrease resistance to airflow on inspiration
◦ Thyroaretenoid muscles - Expiration - Vocal cords adduct to increase airway resistance (and prevent lower airway collapse)
What are the relations of the intercostal muscles
- Intercostals - relations - infeiror and superior rib, intercostal nerve bundle, internally parietal pleura and externally skin. both are supplied by intercostal nerves, and anteiror and posterior intercostal arteries.
External intercostals - how many
11 pairs
What is the origin and insertion fo the external intercostals
origin from inferior border of above rib (tubercles) to superior border of below rib at the costochondral junction - fibres run in caudal - ventral direction
External intercostal function
‣ Bucket handle movement causing elevation of the ribs towards each other to elevate the rib cage
‣ Innervated by intercostal nerves
‣ Anteriorly the external intercostal are replaced by fibrous aponeurosis
Internal intercostals - how many
11 pairs
How are internal intercostal related to external intercostals
right angles
from superior border of the below rib off the sternocostal junction to the inferior border of the above rib tubercle
Contract and depress the ribs
What is the function of the internal intercostals? What do they share this with?
‣ Expiratory role as they contract and depress the ribs
‣ Synergist to quadratus lumborum, abdominal muscles, obliques
What is the levator costae?
small thin muscle joining upper edge of a rib with corresponding tran sverse process of a verterbre
Transverse thoracis is what? Connects where? Does what?
◦ Costal cartilages of the last 3-4 ribs/body of sternum and xiphoid projecting to the ribs 2-6
◦ Separates thoracic cage from pariatel pleura
◦ Forceful expiration by decreasing transverse diamtre of thoracic cage
What function do the scalenes have in inspiration?
Elevate the rib cage counteracting the downward motion fo the diaphragm
What is the diaphragm? What is unique about its structure? What important two structural elements does it have?
◦ Thin sheet of skeletal muscle, oval in shape, composed of a central noncontractile tendon and two discrete muscular portions, the costal and crural diaphragm.
In what direction do the fibres arch?
◦ From the circumference, fibres arch upwards into a pair of domes and then descend to a central tendon which has no bony attachment.
Where is the central tendon relative to surface anatomy when describing the diaphragm
Xiphisternum
Superior relation of the diaphragm
Pericardium and basal lung segments - central tendon continuous with the pericardium
Inferior relations of the diaphragm
◦ Inferiorly:
‣ Right: liver, adrenal gland, kidney (the central tendon is also blended with the fibrous capsule of the liver)
‣ Left: stomach, adrenal gland, kidney and spleen
Posterior relations of the diaphragm
◦ Posteriorly: crura (right and left crus), plus 3 arcuate ligaments: median (joins the two crura), medial (a thickening over the psoas), and the lateral (a thickening over the quadratus lumborum)
‣ Also aorta, azygos veins, oesophagus, vagus nerve, pleura
What are the 3 arcuate ligaments
◦ Posteriorly: crura (right and left crus), plus 3 arcuate ligaments: median (joins the two crura), medial (a thickening over the psoas), and the lateral (a thickening over the quadratus lumborum)
‣ Also aorta, azygos veins, oesophagus, vagus nerve, pleura
What joins the right and left crus
Median arcuate ligament
Anterior relations of the diaphragm
◦ Anteriorly: tendinous origin is from the lower six costal cartilages and posterior aspect of the xiphoid proces
What are the openings and what levels do they occur at for the diaphragm>
◦ Aortic opening (at the level of T12)
◦ Oesophageal opening (at the level of T10)
◦ Vena cava foramen (at the level of T8)
◦ Smaller openings for the hemiazygos vein, splanchnic nerves, superior epigastric vessels, lymphatics
Blood supply of the diaphragm
◦ Costal margin supplied by the lower five intercostal and subcostal arteries.
◦ Main central mass supplied on their abdominal surface by right and left
◦ inferior phrenic arteries from the abdominal aorta
◦ The phrenic nerve is supplied by the pericardiacophrenic artery
Innervation of the diaphragm
◦ Motor: right and left phrenic nerves (C3, 4 and 5, but mainly C4)
◦ The lower intercostal nerves send some proprioceptive fibres to the periphery of the diaphragm
- * Bilateral nerve supply (i.e. the loss of one phrenic nerve does not adversely affect the function of the entire diaphragm
What type of muscle fibres does the diaphragm have
slow twitch favouring sustained activity
Where does the innervation attach for the diaphragm
Centrally and extends radially
What are the posterior attachments of the diaphragm
◦ Right crus - arises from L1-3
◦ Left crus arised from L1-2 and their intervertebral discs
What are the anterior and lateral attachments of the diaphragm
◦ Lumbar and arcuate ligaments, costal cartilages of ribs 7-10 (directly to ribs 11 and 12), and xiphoid process of the sternum
Diaphragm is responisble for what portion of normal breathing
90%
How does the diaphragm work in concert with abdominal muscles?
‣ Flattening fo the diaphragm against the counterpresure of the abdominla muscles produces an increase in circumference of the lower ribcage
IF the diaphragm contracted without any other muscles involved what would occur?
Decrease in AP diamrtre
What is the zone of apposition with reference to the diaphragm>
◦ Zone of apposition - posteior portion of the pleural space where no lung and diaphragm is directly apposed to the rib cage, at FRC 55% of diaphragms surface apposed tot he ribs. It is a marker of respiratory reserve
At FRC what portion of the diaphragm is against the rib cage? What is this called
◦ Zone of apposition - posteior portion of the pleural space where no lung and diaphragm is directly apposed to the rib cage, at FRC 55% of diaphragms surface apposed tot he ribs. It is a marker of respiratory reserve
Non respiratory functions of the diaphragm 4
◦ Manipulates thoracic pressure for coughing and sneezing
◦ Increases intraabdominal pressure
‣ Expelling urine, faeces
‣ Childbirth
‣ Vomiting
◦ Mechanical barrier to intraabdominal organs and fluid
◦ Functional oesophageal sphincter - right crus loops around the oeosphageal hiatus thus when contracting adds pressure to prevent reflux when abdominal pressure increases during inspiration
What is the most important breathing muscle in the abdomen?
Transverse abdominus and internal oblique
- Apply counterpressure to the flattening diaphragm to facilitate lateral and anteroposterior expansion of the chest
Maintain intra-abdominal pressure during expiration augmentin pasive recoil, more important when standing than supine
How do the abdominal muscles help in inspiration
- Apply counterpressure to the flattening diaphragm to facilitate lateral and anteroposterior expansion of the chest
When do abdominal muscles start helping in forceful expiration
minute volume >40L/min
When do accessory muscles start helping
> 50L/min minute volume
What is the first inspiratory accessory muscle to help?
Scalenes
What does the SCM perform in inspiration
Pump handle mechanism causing elevation of the sternum
What are the muscles that can act as accessory muscles in inspiration
Scalenes first then SCM then others
* Sternocleudomastoid muscle
◦ Pump handle movement causing elevation of the sternum by the sternocleudomastoid muscle
* Trapezius
* Pectoralis group
* Extensors of the vertebral column
* Serratus anterior
* Latissimus dorsi
What are the roles of surfactant proteins
4 specific proteins have been found
- SP - A - D
SP B and C are hydrophobic proteins that spread phsopholipids into a monolayer lining the alveoli
SPA and SPD are more hydrophilic
- Facilitate the spread action of SPB by promoting the breakup of secreted lamellae bodies
- Preventings plasma protein entry into alveolar fluid
- ENhanced macrophage activity
- Regulating surfactant turnover by endhancing uptake and inhibiting secretion of phsopholipids by type 2 cells
Functions of the nose
- Pathway for bulk flow of inspired and expired gas
- Conditionining of ventilated gas - humidification and heating, also preserves water to prevent loss. Faciitated through large area
- Smell
- Eustacian tube
