Week 1 Flashcards
Thoracic cage is comprised of?
- 12 thoracic vertebrae
- 12 pairs of ribs
- Sternum
Function of thoracic cage
House and protect the internal organs
Thoracic cavity is limited superiorly by?
First ribs (surrounding the thoracic inlet)
Thoracic cavity is limited inferiorly by?
Muscular diaphragm (closing off the thoracic outlet)
Domes of the diaphragm lie at approximately the?
5th intercostal space during expiration
Between the ribs, the intercostal space is bridged by?
External, internal and innermost intercostal muscles
Between internal and innermost intercostal muscle layers resides a neurovascular bundle consisting of?
- Intercostal vein
- Intercostal artery
- Intercostal nerve
Intercostal vein drains into?
Azygous and hemi-azygous venous systems
Intercostal artery is supplied by the?
Aorta
Intercostal nerve branches off the _____ and passes through the _______.
Thoracic spinal cord segments; sympathetic trunk
Principle muscle of respiration
Diaphragm
Diaphragm is innervated by?
2 phrenic nerves (left and right)
2 phrenic nerves originates from?
Cervical spinal cord segments C3-5
Pneumonic for C3-5
C3-4-5 keeps the diaphragm alive
What happens to diaphragm during quiet inspiration?
Diaphragm descends to increase the thoracic volume and produce a corresponding decrease in intrathoracic pressure
Decrease in intrathoracic pressure promotes?
Promotes passage of air into the lungs
During passive expiration, what happens to diaphragm?
Diaphragm recoils to decrease the thoracic volume producing a corresponding increase in intrathoracic pressure causing air expulsion.
Contraction of the intercostal muscles causes?
Increases intrathoracic volume by elevating and separating the ribs
During periods of increased oxygen requirement (e.g. exercise, airway obstruction), which muscles become active?
Accessory muscles of inspiration activate and elevate the ribs to further increase intrathoracic volume.
Accessory muscles of inspiration include
- Pectoralis minor
- Scalenes
- Sternocleidomastoid
- Intercostal muscles
During forced expiration (e.g. blowing up a balloon, playing a trumpet), which muscles activate?
Contraction of abdominal muscles increases intrathoracic pressure facilitating air exit from the lungs
Air passes to the lungs from the upper respiratory system via the?
Trachea
Trachea begins at ?
At the inferior border of the larynx (CV6)
Trachea is kept patent (held open) by?
16-20 C-shaped rings of hyaline cartilage that are open posteriorly and completed by the trachealis muscle (smooth).
C-shaped rings of hyaline cartilage and trachealis muscle permits what?
Permits expansion of the posteriorly related oesophagus during swallowing
Trachea bifurcates at?
At the carina to form 2 cartilage ring reinforced primary bronchi behind the manubriosternal joint (sternal angle)
Two primary bronchi is located behind?
Behind the manubriosternal joint
Inhaled objects are more likely to be trapped in which bronchus?
Right primary bronchus as it is shorter, wider and more vertically oriented than the left.
Cartilage-containing primary bronchi further divide to form?
Cartilage-containing secondary bronchi
Cartilage-containing secondary bronchi further divide to form?
Cartilage-containing tertiary bronchi
Cartilage-containing tertiary bronchi divide to form?
Cartilage-deficient terminal bronchioles
Terminal bronchioles go on to form?
Respiratory bronchioles
Respiratory bronchioles ultimately end in the?
Alveoli
Left lung comprises an?
Upper and lower lobe separated by an oblique fissure
Right lung comprises an?
Upper, middle and lower lobe separated by oblique and transverse fissures
Bronchi and pulmonary vessels form the?
Lung root
Lung root passes through the?
Pulmonary hilum of the lung
Space between lungs is the?
Mediastinum
Lungs and thoracic wall are intervened by?
2 layers of pleura
Parietal pleura lines?
Lines the inner aspect of the thoracic wall
Visceral pleura invests the?
Lungs, intervening betweent he lobes
2 layers of pleura are held together by ?
Surface tension due to a small amount of fluid in the pleural space (pleural cavity)
Pleural fluid allows?
The visceral and parietal pleura to slide over one another but resists separation of the pleural layers.
Liquid surface tension between the pleural layers counteracts the tendency for?
For thoracic wall to expand outwards and the elastic lungs to recoil inwards.
The presence of air in the thoracic cavity is referred to as a ?
Pneumothorax
Pneumothorax is due to a?
Direct communication of the pleural space with atmospheric air
Pneumothorax disrupts?
Disrupts the fluid surface tension and results in separation of the pleural layers and a consequential recoil or collapse of the related lung
Lungs and visceral pleura only receive autonomic innervation with the parasympathetic control arising from?
Vagus nerves (cranial nerve X)
Sympathetic control of lungs and visceral pleura is governed by?
Sympathetic trunks
The parietal pleura is innervated by?
Nociceptors (detectors of noxious stimuli, usually perceived as painful)
Nociceptors send signals regarding?
Pleural stretch, inflammation or trauma to the brain via the intercostal nerves (within the intercostal space) and the phrenic nerves (around the hilum)
Sub-pleural lymphatic plexus drains to the?
Hilar lymph nodes
Lungs receive deoxygenated blood from the heart via the?
Pulmonary arteries
Oxygenated blood return to the heart via the?
Pulmonary veins
Surface of the lungs is covered by a?
Thin layer of connective tissue and mesothelial cells which is in close contact with a similar layer of tissue covering the interior surface of the chest wall
Between the parietal pleura and visceral pleura, what is the total volume of the pleural space?
2 ml in total volume which spreads over the surface area of the lungs
Thickness of pleural layer is only about?
10-30 um
Surface mesothelial cells of the visceral pleura have a ?
High density of microvilli to enhance absorption
Parietal mesothelial cells have a?
Lower density of microvilli
Microvilli function on mesothelial cells?
They also trap glycoproteins which act as a lubricant between the surfaces of the constantly moving lungs and chest wall
Pleural pressure changes with lung volume during the breathing cycle because?
Lung becomes stiffer (less compliant) with expansion
In the erect position, lower thoracic pleural changes from?
-0.5 to -33 cm H2O
In erect position, upper thoracic pleural pressure changes from?
-8.5 to -40 cm H2O as the lung expands from functional residual capacity (FRC) to total lung capacity (TLC).
The lower parts of the lung expand more during
Inspiration, because they operate on a more compliant part of the volume pressure relationship
Volume change for a given pressure change is greater in the lower parts because they?
They are less ‘stretched’ than the upper parts at low lung volumes.
A gradient of ventilation - perfusion ratios exists from high at the apex to low at the base of the lung because?
Because the blood flow gradient is considerably steeper than the ventilation gradient
Graded increase in ventilation from top to bottom is disturbed if?
If the subject inspires from residual volume (RV) because there is a small positive pleural pressure at the base of the lung at this lowest possible volume due to airway closure at the lung bases.
Until the basal pleural pressure becomes negative again at about FRC, the ventilation will be directed to?
Upper parts of the lung
List the precise mechanisms giving rise to the negative pleural pressure gradient around the lung
- shape and mechanical properties of the chest wall (which can be altered by changes in lung volume, changes in body posture and contraction of the respiratory muscles.
- inherent stress-free shape of the lung
- the weight of the lung
- elastic properties of the lung
- possible friction between the two pleural surfaces
Autonomic nervous system innervates?
Smooth muscle, cardiac muscle and glands that participate in process of homeostasis
Autonomic nervous system is usually considered to be a _____ system only.
Motor
Peripheral part of the sympathetic division arises from the ___ and _____ spinal cord forms the sympathetic trunk
Thoracic; upper lumbar
Preganglionic cell bodies are located in the _____ horn of the spinal cord grey matter
Lateral
Post-ganglionic cell bodies in either the sympathetic trunk or peripheral ganglia such as the ______ ganglia.
Coeliac
Peripheral part of the parasympathetic system arises from either?
Brain stem or sacral spinal cord segments
Cranial part distributes through which nerves?
Oculomotor, facial, glossopharyngeal, and vagus nerves and the sacral part in peripheral nerves, splanchnic nerves or along blood vessels
Cranial preganglionic nerve cell bodies are located in the?
Cranial nerve nuclei
Sacral preganglionic cell bodies are in the?
Intermediate region of sacral spinal cord grey matter segments two to four.
Postganglionic parasympathetic neurons are usually ___ and have their cell bodies in or near the structures innervated.
Short
Peripheral neurotransmitter for the sympathetic system is ____ (except for sweat glands).
noradrenalin
Peripheral neurotransmitter for the parasympathetic division is ______.
Acetylcholine
Additional part of the visceral motor system controls the intrinsic action of the gut and is termed?
Enteric system
Major structures in the thorax to receive an autonomic nerve supply are?
- Oesophagus
- Lungs
- Heart
- Blood vessels (located throughout the cavity and its walls).
The walls of the thorax including the skin receive only a?
Sympathetic supply via the sympathetic trunk and the intercostal nerves
Preganglionic sympathetic supply to the heart and lungs derives from?
Spinal cord segments T1 to T5.
T1 to T5 postganglionic fibres distribute via nerves which leave the sympathetic trunk in the?
Upper thoracic and lower cervical regions
T1 to T5 postganglionic fibres act to?
Dilate the respiratory airways and for the heart increase rate and force of contraction
Preganglionic parasympathetic supply to the oseophagus, lungs and heart originate from which cranial nerve nuclei?
dorsal motor nucleus of the vagus, nucleus ambiguous
Parasympathetic system acts to stimulate?
Peristalsis in the oesophagus, narrow airways and increase secretion in the lungs and to decrease heart rate.
where are nerve collections termed plexuses found?
Oesophagus, arch of the aorta and the root of the lungs
Most muscular arteries and arterioles only receive a _____ supply which when activated causes vasoconstriction.
Sympathetic
Large veins have an ____ innervation.
Autonomic
Some blood vessels within the body receive both a sympathetic and parasympathetic innervation which may cause either?
Vasodilatation or constriction
Primary survey for thoracic trauma is for?
Life threatening chest injuries are identified
Initial resuscitation for thoracic trauma is for?
Restoration of vital functions
Secondary survey for thoracic trauma is for?
Detailed examination of chest and whole patient
Pneumothorax is a condition that occurs when?
Gas collects in the pleural space, resulting in partial or complete collapse of the lung, depending upon the volume of gas in the pleural space.
Under normal physiologial conditions, the pressure in the pleural space is?
Slightly negative compared with atmospheric pressure
Why is pleural space pressure slightly negative compared with atmospheric pressure?
Because of the tendency for the chest wall to recoil in an outward direction, and the lung due to intrinsic elasticity to recoil in an inward direction
How does the lung progressively collapse?
When air enters the pleural space, either through a rupture of the lung or bronchial tissue or through a leak in the chest wall, there is no longer negative pressure in the pleural space.
What is a tension pneumothorax?
This may occur if there is a one-way leak of air into the pleural space (a so called “ball valve leak”), which leads to a marked increase in pleural pressure, complete collapse of the lung, substantial shift of the mediastinum and compromised cardiac function.
Pneumothoraces may occur spontaneously, which is most commin in?
Young people
Pneumothoraces can be in association with?
Asthma or COPD
Chest trauma, particularly associated with fractured ribs, can result in?
Pneumothorax
How does mechanical ventilation result in pneumothorax?
High positive pressures are generated within the airways
What happens in patients with spontaneous pneumothorax?
Small blebs on the surface of the visceral pleura (of uncertain aetiology) rupture, allowing the escape of air from the lungs into the pleural space.
Spontaneous pneumothorax has a tendency to?
Recur
Common symptoms of pneumothorax?
Pleuritic chest pain and dyspnoea
Typical physical signs of pneumothorax?
Respiratory rate, hyper-resonance to percussion and diminished breath sounds on the affected side and tracheal deviation, if there is a mediastinal shift.
How is pneumothorax diagnosed?
Chest x-ray confirms it, which demonstrates the visceral pleural edge and no lung markings between the edge and the bony structures of the chest wall.
Treatment of pneumothoraces depends upon ?
Size
Small pneumothoraces in which the leak has sealed spontaneously, will?
Will resolve without intervention because the air in the pleural space will be absorbed progressively over a period of days or weeks.
Larger pneumothoraces require what treatment?
Aspiration of the air from the pleural space, either via a canula and syringe, or the insertion of an indwelling intercostal catheter.
Intercostal catheter is connected to an underwater drain to allow the air in the pleural cavity under positive pressure to escape but prevent the re-entry of air into the pleural cavity.
Pulmonary circulation is a?
High flow, low resistance and low pressure circulation.
What constitutes pulmonary flow?
Entire venous return to the right atrium entering the lungs via the pulmonary artery
Bronchial arteries provide?
Small flow (1-2% of cardiac output) of fully oxygenated blood which provides the metabolic needs of the tissues
Pulmonary artery pressure is about?
25/10 mm Hg (systolic/diastolic)
Capillary pressure averages about?
6-8 mm Hg
Pressure in the pulmonary veins is about?
1-3 mm Hg
Entire cardiac output flows through the lungs with?
Lower pressure gradients
Pulmonary resistance is about?
17-20% of the systemic system
Compare pulmonary arterioles and capillaries to their systemic counterparts
Pulmonary arterioles and capillaries are shorter and have less smooth muscle and less muscular tone than systemic ones.
Lungs are roughly _____ in height.
30cm
Because the lungs are roughly 30cm in height, pressures in the arteries, capillaries and veins are?
All lower at the apex of the lungs by about 10 mm Hg and greater at the base of the lungs by about 10 mm Hg (in the upright human).
Because the pressures inside the vessels compared with alveolar pressure are much lower at the apex of the lungs, what happens to the capillaries and small vessels?
Capillaries and small vessels tend to collapse, while the capillaries are maximally dilated at the base of the lungs.
Because pressures inside the vessels compared with alveolar pressure are much lower at the apex of the lungs, what happens to blood flow?
Blood flow is higher at the base of the lungs, and lower at the apex (though this distrubtion of flow is eliminated when lying down
Because the capillary pressure is lower in the lungs, lungs are less susceptible to?
Oedema (plasma oncotic pressure is 25 mm Hg while the capillary pressure is only 6-8 mm Hg)
If oedema of the lungs progresses to fluid in the alveoli, and consequent impairment gas transport, it can result in?
Potentially lethal hypoxaemia.
Benefits of reduced capillary pressure in the lungs are partly offset by?
Larger interstitial oncotic pressure and a more negative interstitial hydrostatic pressure.
Gradient of capillary pressure from apex to base of the lungs means that?
Means oedema production is greater at the base of the lungs
Likewise in the pleura space, gravity ensures what in the upright human?
Fluid accumulation is first noticeable around the base of the lungs
Commonest causes of pulmonary oedema are?
Left sided heart failure
Left sided heart failure results in?
Results in an increase in left atrial pressure and therefore pulmonary venous pressure and pulmonary capillary pressure
Infection of the lungs tissue (pneumonia) causes increased?
Increased pulmonary capillary and alveolar wall permeability so that interstitial oedema and alveolar flooding occur.
Describe hypoxic pulmonary vasoconstriction as a key reflex
Sympathetic vasoconstriction maintains peripheral resistance and blood pressure.
If a region of the lungs is underventilated (low PO2), then efficient gas exchange requires a reduction of blood flow to this poorly ventilated region.
The smooth muscle of pulmonary vessels vasoconstricts in response to low PO2, in contrast to systemic vessels.
Sympathetic nerve supply to pulmonary vessel smooth muscle is minimal
Hypobaric hypoxia is?
Low environmental oxygen causing hypoxaemia
Immediate response to the stress of hypoxia and hypercapnia is?
Increased ventilation and cardiac output to maintain adequate tissue oxygen delivery via highly integrated responses that involve both local and reflex mechanisms.
Local effects in vascular beds in response to hypoxia?
They increase perfusion to vital and more hypoxia sensitive organs such as the brain.
Reflex responses are mediated via?
Central and peripheral chemoreflexes, which increases ventilation while maintaining or increasing blood pressure through increases in cardiac output and vasoconstriction in less vital and less oxygen-sensitive tissues (such as skeletal muscle and gastro-intestinal tract).
One major adaptative response to chronic hypoxia include: an increase in ventilation mediated by?
Peripheral chemoreceptors
Compensation for chronic hypoxia via metabolic (including renal) and or respiratory mechanisms is aimed to maintain?
Maintain acid base balance in response to changes in the arterial partial pressure of carbon dioxide (PaCO2) and blood pH
In response to chronic hypoxia, increased cerebral and myocardial blood flow is at the expense of?
Expense of blood flow to less vital organs
In response to chronic hypoxia, increased cardiac output is via?
Via increased peripheral vascular resistance, which aims to maintain blood flow to more vital tissues and organs.
Increased pulmonary arterial pressures in response to chronic hypoxia is due to?
Reflex pulmonary vasoconstriction; pulmonary blood flow also increases as a result of increased cardiac output. Continued or worsening hypoxaemia may lead to cor pulmonale and right heart failure.
Major adaptative response to chronic hypoxia include: increases in _____ concentration with secondary _______. Additionally, a shift occurs in?
haemoglobin; polycythaemia; a shift occurs in the oxyhaemoglobin dissociation curve, which moves to the right due to multiple mechanisms including increases in red cell 2,3-DPG (diphosphoglycerate) concentration as well as any effects of respiratory or metabolic acidosis which may accompany the underlying cause of the hypoxaemia
What changes in the sympathetic nervous system occurs in response to chronic hypoxia?
Increased levels of circulating catecholamines, with further effects on vascular haemodynamics
At a cellular level, increased levels of ________ occurs to maintain levels of ATP needed for cellular function in chronic hypoxia.
Anaerobic metabolism
Release of several endocrine substances such as ___ and ____ which are also vasoactive occur in chronic hypoxia.
Renin and vasopressin.
Road trauma: bilateral mandibular fractures may leave the tongue (attached to the anterior segment of the mandible) to do what?
Free to fall back over the oropharynx leading to airway obstruction and possibly death.
In middle third fractures, the ‘maxilla’ may be found?
found back and down.
________ from middle third fractures and bilateral mandibular fractures can also lead to airway obstruction.
Uncontrolled bleeding
Angiooedema may also involve ______ of the tongue.
Gross swelling
Facial trauma may cause obstruction and/or subsequent infection (pneumonia). Common organisms include:
Staphylococcus aureus and klebsiella pneumoniae
Poorly controlled oral or dental infections may spread via fascial planes producing?
Gross swelling and airway obstruction e.g. Ludwig’s Angina
Surgical emphysema may be seen following?
Following fractures of the middle third of the face involving the air sinuses (e.g. maxillary antrum)
More dangerous is surgical emphysema caused by using ?
Conventional air turbine for surgical extractions
Conventional air turbine causing surgical emphysema is very ?
Very acute and very large, and can involve the mediastinum (pneumo-mediastinum)
Signs of pneumo-mediastinum include?
- Subcutaneous emphysema (crackles on palpation)
- Dull heart sounds
- Mediastinal crepitations with each heart beat
- Distension of neck veins
- Facial engorgements
- Hypotension
- Hypercarbia (high carbon dioxide level)
- Respiratory acidosis
Infection may follow from introduction of organisms such as ____ or _____ via the dental compressed air line.
Pseudomonas; legionella
All patients with severe facial trauma must be assessed for possible spinal damage prior to definitive surgery. What can be missed easily?
A fracture of odontoid peg of C2 can easily be missed.
