Flashcards in WEEK 2 Deck (182):
What is interstitial fluid?
It is fluid trapped amongst filaments
About 1% is water & 95-99% is gel
What are (i) crystalloids (ii) colloids?
(i) low molecular weight solutes e.g. Na+, Cl-, K+
(ii) plasma proteins - exists within interstitial & capillaries but more prominent in plasma (capillaries)
What are the boundaries of the anterior mediastinum?
Between the sternum & pericardium
What are the boundaries of the superior mediastinum?
Between the thoracic inlet & sternal angle at T4-5; posterior to the manubrium; anterior to T1 - T4; oblique from the manubrium upwards to T1
What is the location of the thymus?
From the jugular notch to the 4th CC (& possibly beyond). It is a bi-lobed structure in the anterior mediastinum between the manubrium, sternum & pericardium
What is the function of the thymus?
It is active throughout life, particularly in childhood & puberty, with age fibro-fatty infiltration increases. Its function is to programme T-lymphocytes; recognise “self”
What is the blood supply of the thymus?
Int thoracic & inf thyroid arteries. Venous drainage to L.brachiocephalic vein
Structures on the left of the mediastinum are related to what?
Arteries & then the LV. (Left common carotid artery, left subclavian artery, arch of aorta & thoracic aorta)
What do the vagus & phrenic nerves lie between?
The venous & arterial planes
What can the superior mediastinum be considered as?
As a series of planes moving from anterior to posterior (once the thymus has been removed)
What are the 5 bony landmarks of the venous plane?
1. Internal jugular and subclavian veins join to form right and left BCVs - Posterior to the sternoclavicular joint
2. Left BCV passes anterior to the arch of the aorta; posterior to the manubrium
3. RBCV & LBCV join to form the SVC - posterior to the 1st R CC
4. Arch of the azygous vein joins SVC - posterior to the 2nd R CC
5. SVC enters the RA - posterior to the 3rd R CC
What can happen with the LBCV in children?
It receives the thyroid vein & may protrude above the manubrium where it may be at risk in tracheostomy
What does the (i) azygous (ii) subclavian (iii) internal jugular veins(s) drain?
(i) posterior chest wall (ii) upper limb (iii) head & neck
In what mediastinum does the thoracic (descending) aorta lie?
What 2 things is the trachea “clasped” by?
the left common carotid artery & brachiocephalic trunk
At what vertebral level is the jugular notch located?
Where is the pulmonary trunk located?
Within the pericardium to the left of the ascending aorta
At T5, what does the pulmonary trunk do?
the R.pulmonary artery (posterior to the asc Ao & SVC) & enters the R lung.
the L.pulmonary artery (inferior to the arch of Ao & anterior to the thoracic aorta) & enters the left lung
What is the difference between the location of the pulmonary artery & bronchus on the left & right lung roots?
On the right the artery is inferior to the bronchus whilst on the left the artery is superior to the bronchus
In what mediastinum is the ligament arteriosum located?
Where is the trachea palpable? Where does it start & end?
anteriorly in the midline of the neck. Starts at C6 & ends at T4/5 (sternal angle) at carina
What is the location & function of trachealis?
Found posteriorly, between the ends of the C-cartilages. It alters tracheal diameter
In the superior mediastinum, what is the position of the trachea, the oesophagus & the left recurrent laryngeal nerve?
the trachea is anterior to the oesophagus - with the left recurrent laryngeal nerve between
What difference(s) is there between the right & left main brochi?
the right is shorter, wider & more vertical than the left
At rest, what does smooth muscle contraction do to tracheal diameter? What does this in turn do?
It decreases tracheal (& bronchial) diameter to decrease respiratory dead space.
What effect does cigarette smoke have on cilia?
It paralyses them
What is the function of the oesophagus?
transport of food & fluid through the thorax & diaphragm to the stomach
Where is the oesophagus located?
It starts at C6, passes immediately posterior to the trachea, anterior to the vertebral column, with the arch of the arch of the aorta to its left
What is the thoracic duct a continuation of? What does it lie between & in what mediastinum?
The cisterna chyli
Lies between the aorta & azygous vein in the posterior mediastinum
Describe the route of the thoracic duct.
At T4/5 it crosses behind the oesophagus to ascend on its left side
The duct then arches over the apex of the left lung & pleura to enter the junction of the left internal jugular & the left subclavian vein
What can left lung tumours affect?
The left recurrent laryngeal nerve
Nodes in the lungs & lung hilum drain to where?
Where are the mediastinal nodes located?
Clustered around the trachea & oesophagus in the superior mediastinum, consequently, these nodes may be involved in the spread of lung tumour
What are the mediastinal nodes called if they are (i) above (ii) below the tracheal bifurcation?
(i) Superior tracheobronchial nodes
(ii) Inferior tracheobronchial nodes
Where are the anterior mediastinal nodes found? Where do all the mediastinal nodes drain to?
Around the brachiocephalic veins
They all drain to the thoracic duct on the left OR the lymph duct on the right BUT they communicate with the deep cervical nodes
Why is the consistency of interstitial fluid more like a gel than a free flowing liquid?
Collagen fibres and proteoglycan filaments (interstitium) are dispersed in the interstitial fluid, increasing viscosity
Why do colloids (plasma proteins) not move out of the capillaries?
In a nutshell, they are too large - barred from crossing by capillary walls. A few however, may escape
What is the average hydrostatic pressure at the arterial end of circulation?
Negative hydrostatic pressure in the interstitial space leads to...?
Water drawn out of capillaries
Positive hydrostatic pressure in the interstitial space leads to...?
Water pulled into capillaries
What is the average hydrostatic pressure at the venous end of circulation?
What would be the result of having purely hydrostatic pressure pushing water out?
Give 4 methods which increase venous pressure and hence increase venous return.
(1) Increase blood volume e.g. haemorrhage, fluid challenge
(2) Increase inspiration movements (diaphragm descends, decreased pressure in thorax => increased pressure diff btween peripheral veins & heart)
(3) Increase skeletal muscle movement (as a pump)
(4) Increase activity of sympathetic nerves to veins
Venous return is a major determinant of...
Cardiac output due to myogenic response of the ventricles
What 4 features is the lymphatic system in control of?
1. Concentration of proteins in interstitial fluids 2. Volume of interstitial fluid 3. Interstitial pressure 4. Immune response
What is orthostatic (postural) hypotension?
A decrease in BP (due to decreased venous return & => decreased CO) when going from supine to upright. Reflex vasoconstriction in legs and lower abdomen (NOTE: it takes a few seconds to kick in)
Which is lower, the plasma or interstitial osmotic pressure?
What substances generates the Colloid Osmotic/Oncotic Pressure?
Plasma proteins (mainly albumin) This creates a difference in the abundance (and consequently pressures) between capillaries and extracellular fluid
When standing completely still, what is the mean arterial pressure at (i) the level of the heart (ii) feet?
(i) approx 100mmHg
(ii) approx 190mmHg
What is the venous system in terms of volume & pressure?
High-volume low pressure system
How can compliance of veins be adjusted?
By sympathetic innervation
In what 8 scenarios should a check x-ray be requested?
1. Shortness of breath
2. Acute chest pain
3. Investigation for malignancy
4. Following severe trauma
6. Chronic lung diseases
7. Pleural diseases
What is the lingula?
A combined term for the 2 lingular bronchopulmonary segments of the left UPPER lobe. Made up of: Inferior lingular segment, superior lingular segment.
What is the process for reviewing a chest XR?
1. Check patient identity and date of CXR
3. Mediastinum/ airways
4. Lungs + pleural reflections
6. Soft tissues
7. Review areas ** -Apices -Behind the heart -Below the diaphragm
What is the carina?
The ridge of cartilage of the trachea at the bifurcation
What is possible reason for a missing rib from a CXR?
Tumour grown around the rib. If the CXR is PA then the tumour is posterior to rib
What are the review areas of the CXR?
Behind the heart
Below the diaphragm (Space between liver = gas)
What are the 4 areas of error that can occur when taking a CXR?
P-A vs A-P Film: PA preferred as the magnification of heart is reduced = film more reliable Rotation: For optimum rotation, there must be an equal distance between the medial ends of the clavicle and the spinous processes of the vertebrae Penetration: Over-penetration appears dark, Poorly penetrated appears light/fuzzy Inspiration vs Expiration: Inspiration preferred as structures more densely packing into thorax
Why are feedback systems required to control the heart & blood vessels?
Required to maintain tissue perfusion across the whole of the body
- to keep a relatively constant arterial BP
- to control distribution of the total cardiac output
If the arterial blood pressure is (i) too high (ii) too low, what happens?
(i) damage to vessels & organs
(ii) blood flow to organs would fail
Nervous control of arterial pressure is rapid, by how much (& how fast) can pressure both increase & decrease?
Can increase to 2x normal within 5-10s
Can decrease arterial pressure to 50% normal within 10-40s
What are the 6 fundamental components of a reflex control system?
1. Internal variable to be maintained
2. Receptors sensitive to change in the variable
3. Afferent pathways from the receptors
4. An integrating centre for the afferent inputs
5. Efferent pathways from the integrating centre
6. Target effectors that alter their activities
What are the nature and location of the baroreceptors which detect changes in blood pressure?
(1) Walls of aorta - afferent fibres follow vagus (Xth cranial) nerve
(2) Carotid artery - afferent fibres follow (IXth cranial) glossopharyngeal nerve
- their firing rate increases when BP increases & vice versa
- they are sensitive around a "set-point" which can change e.g. hypertension
What is the primary purpose of baroreceptor reflex control?
To reduce the minute-to-minute variations or arterial pulse
What is the function of cardiopulmonary baroreceptors? If their rate of firing decreases (ie signalling less blood volume) then what happens?
They sense CENTRAL blood volume - atria, ventricles, veins & pulmonary vessels
Sympathetic nerve activity to the heart & BVs increases
Parasympathetic nerve activity to the heart decreases
What is the Bainbridge Reflex?
A sympathetic-mediated reflex in response to increased blood in atria
- increases HR & contractility
- prevents damming of blood in veins etc
If aortic/carotid baroreceptors sense high pressure what can happen?
The bainbridge reflex can over-ride
What is the (i) sensory area (ii) lateral portion (iii) medial portion of the Medullary cardiovascular control "vasomotor" centre?
(i) input from baroreceptors
(ii) efferent sympathetic nerves
(iii) Efferent parasympathetic (vagal) nerves
What effect does (i) sympathetic (ii) parasympathetic system have on cardiac output?
(i) can significantly effect stroke volume & rate
(ii) predominate tone at rest
What effects does the sympathetic system have on the blood vessels?
continuous low-level tone affects total peripheral resistance => are kept partially constricted
What happens to veins when sympathetic effects are increased?
=> Increased venous return
=> increased stoke volume
=> increased cardiac output
What happens when blood flow to the medullary CV control centre is decreased?
(1) Increase in peripheral vasoconstriction - almost completely occludes some peripheral vessels
(2) Increase sympathetic stimulation of the heart
(3) Large increase in systemic arterial pressure (as high as 250 mmHg for 10 mins)
How is BP regulated long term?
Via blood volume
Why do neuronal reflex mechanisms exist?
To maintain BP in the immediate/short term
Which nerve do afferent fibres from the walls of the aorta follow?
Vagus nerve (Xth cranial)
Which nerve do afferent fibres from the carotid artery follow?
Glossopharyngeal nerve (IXth cranial)
Describe the (i) myogenic theory (ii) metabolic theory.
(i) Stretch-induced vascular depolarisation of smooth muscle due to increase in arterial pressure
(ii) An increase in arterial pressure increases O2 & "washes out" local factors - LESS FAVOURED THEORY
Where is the thoracic aorta located?
From T4/5 or angle of Louis, the 2nd CC to the aortic hiatus in the diaphragm (T12) between the crura & behind the median arcuate ligament
Lies on the left of the thoracic vertebral bodies but moved to the midline in the lower thorax
What are the branches of the thoracic aorta?
1. Oesophageal arteries supply the middle 3rd of the oesophagus
2. 9 posterior intercostal arteries supply the lower 9 intercostal spaces (3-11)
3. Subcostal arteries that lie inferiorly to the 12th rib & supply the posterior abdominal wall
4. Bronchial arteries vary - usually 2 left & 1 right
5. Other small branches (to diaphragm, pericardium etc)
What is the middle oesophagus supplied by? What does it drain to?
Branches from the aorta
Drains to the azygous vein
What does the internal thoracic give rise to?
What does the anterior intercostal arteries anastomose with? What may this anastomosis form?
Posterior intercostals that have arisen from the aorta
- it may form a collateral circulation in coarctation of the aorta (aortic narrowing)
What is the function of the oesophagus? What is its route within the body?
Transport of food & fluid, through thorax & diaphragm to stomach
It starts in the midline as the continuation of the pharynx at C6, 25cm long x 2cm diameter
Passes posterior to the trachea, anterior to the vertebral column, with the arch of the aorta to its left in the superior mediastinum
Inferiorly it swings forwards & to the left (ant to Ao) before piercing the diaphragm at T10
What is the Ba (barium) swallow? What is its function?
An indentation caused by the normal function of the cricopharyngeal sphincter between the pharynx & the oesophagus
It is to prevent air being sucked into the stomach during inhalation
What muscle makes up the (i) upper 1/3 (ii) middle 1/3 (iii) lower 1/3 of the oesophagus?
(i) striated muscle as swallowing is voluntary & rapid
(iii) smooth muscle, involuntary
There are 3 parts of the oesophagus; the Superior/cervical, the Middle (thoracic) third & the inferior (abdominal) third. Give the arterial, venous, nerve supply & lymphatic drainage for each of them respectively.
SUPERIOR - begins at C6
- A = inferior thyroid arteries
- V = brachiocephalic veins
- NS = branches of vagus (recurrent laryngeal)
- L = deep cervical nodes
- A = thoracic aorta & bronchial arteries
- V = azygous system
- NS = oesophageal plexus ( vagus & sympathetic)
- L = tracheobronchial nodes
- A = left gastric
- V = left gastric (& => to portal vein)
- NS = branches of oesophageal plexus (vagus & symp)
- L = left gastric & coeliac nodes
What is the porto-systemic/portocaval anastomosis?
When submucosal veins in the oesophagus form an anastomosis between the middle & lower thirds
I.e. this anastomosis is between the portal & systemic circulations
Cirrhotic liver disease does what?
It raises the portal venous pressure (portal hypertension) & blood escapes via the submucosal veins in the oesophagus & in to the systemic azygous vein
This results in the veins becoming dilated & toruous: oesophageal varices which may cause fatal haemorrhage
What structures are (i) anterior (ii) posterior to the oesophagus?
(i) trachea, right PA, L main bronchus, LA, diaphragm
(ii) vertebral bodies (C6-T12), thoracic duct (partly), thoracic aorta (inferiorly)
When performing thoracic surgery, why must great care be taken to avoid damage to the thoracic duct?
As leakage of lymph will cause a chylothorax
On the left side (i) what does the thoracic duct drain lymph from? (ii) where does it enter into? (iii) what has it received?
(i) from the lower limbs & abdomen
(ii) enters the left brachiocephalic vein
(iii) (left) jugular lymph trunk (head & neck)
(left) subclavian lymph trunk (UL)
(left) bronchomediastinal trunk (l.thorax)
There is no thoracic duct on the right side of the thorax, so how is lymph filtered/collected?
The r.jugular lymph trunk (head&neck), R.subclavian lymph trunk (UL) & R.bronchomediastinal trunk enter the right brachiocephalic vein separately, but may all fuse to form the Right Lymphatic Duct
What does the azygous system connect?
connects IVC & SVC
What does the azygous vein drain? Where does it begin & what is its path? What veins does it receive?
The posterior walls of the thorax & part of the abdomen
Begins from lumbar & subcostal veins and/or direct branch of the IVC, it passes through the diaphragm with the Ao & thoracic duct
Lies on the vertebral column, in the midline or slightly to the right
Passes posterior to the right lung hilum, then superior to it as it arches in to the SVC at the 2nd Rt CC
It receives veins equivalent to the branches of the descending thoracic aorta
What are the names of the two hemi-azygos veins? Where are they located?
Accessory (upper) hemi-azygous vein - descends from the 4th intercostal space & crosses to the right at approx T8
Hemi-azygous (lower) vein has connections with the left renal vein, it passes through OR behind the left crus of the diaphragm - joins with AV at approx T9
What are the 6 reasons that Sokol & Bergson give for basic errors occurring?
3. covering for colleagues (too little locum support)
4. Professional culture (unwillingness to use support structures)
5. Feeling that decisions must be made alone
6. Unable to admit to uncertainty
What is the Francis Report? Explain VERY briefly.
Public enquiry into Stafford hospital
- Pts were failed by a system which ignored the warning signs & put corporate self-interest & cost control ahead of patients & their safety
290 recommendations including the Duty of Candour
What is Duty of Candour? (2015)
A statutory (legal) obligation on Drs & nurses for a duty of candour so they are open with pts about mistakes
- to inform people when they have been harmed as a result of the care or treatment they have received.
Within the duty, it says that an apology does not amount to an admission of negligence
What 4 points has the GMC released in accordance with the Duty of Candour (2015)
1. Tell the pt when something has gone wrong
2. Apologise to the pt
3. Offer an appropriate remedy or support to put matters right (if poss)
4. Explain fully to the pt the short & long term effects of what has happened
What might happen in response to errors or inadequate care? (HINT: 3 things)
Negligence (legal approach) - the pt might take legal action
NHS complaints procedure - pt might make a complaint
GMC (professional body) - disciplinary action or removal from register
If someone wants to claim that a Dr is negligent what 3 things must they establish?
1. He/she is owed a duty of care by the defendant
2. That the defendant breached that duty by failing to provide reasonable care; and
3. That the breach of duty caused the claimant's injuries (causation), and that those injuries are not too remote (proximity)
What is the (i) Bolam test (ii) Bolitho test?
(i) you call in other healthcare professionals (Drs) & ask them what they would have done in the same situation
(ii) it modified the bolam test to add that the professional opinion must be capable of withstanding logical analysis
What is causation?
There must be a clear link between the action (or inaction) of a doctor, & the harm the pt experienced
- a key factor is also proximity
This is often where a pts case may fail
- is it due to their condition OR their treatment
In order to prove causation you have to prove probability, not just possibility
What are the 2 stages of the NHS complaints procedure? What happens after these 2 stages?
(1) local resolution
(2) Scottish public services ombudsman
Then, finally, judicial review
What are the 2 best ways to learn from errors?
(1) PERSON-CENTRED APPROACH
- focussed on the individual Dr
(2) SYSTEMS-BASED APPROACH
- considers the environment, & seeks to minimise opportunities for error
How has medicine sought to address some of the failures in the current system? (HINT: there's 6 points)
1. Dedicated centres
- beneficial for less common & uncommon procedures
2. Requirement to retrain
- new procedures & techniques
3. Data collection of incidents
4. Improved instrument design
5. Protocols & guidlines
Out of the things that medicine has done to address some of the failures in the current system, what ones have a growing understanding of the "human factors" approach?
Data collection of incidents
Improved instrument design
Protocols & guidlines
Which organ is largely involved in blood volume and hence long term blood pressure control?
Is kidney function modifiable?
Where is angiotensin released from?
What is the enzyme to angiotensins substrate?
What is the MoA of (i) angiotensin I (ii) angiotensin II?
(i) Converted to angiotensin II by an enzyme in the lungs
(ii) Constricts renal arteries (vasoconstriction), decreasing blood flow through kidneys and also is involved in renal retention of salt & water
When arterial pressure (i) increases (ii) decreases, what happens to urine production?
What are the 2 primary determinants of blood pressure?
1. The renal output curve for salt & water
2. The level of salt & water intake
ADH (arginine vasopressin) is released by the pituitary gland in response to what 3 things?
1. Increased osmotic pressure
- hypothalamic osmoreceptors
2. Hypovolemia (10% loss or greater)
- atrial baroreceptors normally inhibit ADH release
- decreased volume leads to decreased firing rate & therefore decreased ADH release
3. Angiotensin II
How does ADH increase blood volume?
By increasing water permeability in renal collecting ducts, therefore decreasing urine production
What cells is renin released from?
Kidney juxtoglomerular cells
What 2 things does angiotensin II cause release of?
Causes release of aldosterone from the adrenal glands, therefore increasing Na & water reabsorption
Also stimulates the release of ADH from the pituitary
What is atrial-natriuretic hormone? What is its function(s)?
28 - amino acid peptide synthesised & stored in muscle cells of the atria
- is released in response to the stretch of the atria
- helps oppose the effects of the Renin-angiotensin-aldosterone system
It may also help counteract volume overload
What is hypovolaemia?
A decreased volume of circulating blood in the body
- decrease in whole blood (e.g. haemorrhage)
- decreased plasma e.g. burns
- decreased sodium e.g. vomiting
A large decrease in BP is recorded
How is the shock of hypovolaemia classified?
CLASS 1 = 10-15% blood loss
CLASS 2 = 15-30% blood loss
CLASS 3 = 30-40% blood loss
CLASS 4 = > 40% blood loss
What is the immediate reflex response to hypovolemia? (state what happens to SV, HR, CO, TPR, MABP)
Stroke volume decreases at haemorrhage, it then increases during relex compensation to around half of its initial level
HR stays constant but increases during reflex compensations
CO decreases at haemorrhage & then increases to around half its initial level
TPR stays constant & then increases during compensation
MABP decreases at haemorrhage & then returns to normal level during compensation
What is the later response to hypovolemia?
1. Arteriolar constriction
- an increase in hydrostatic pressure in the capillaries
- this favours fluid reabsorption
- temporary redistribution
2. Decreased renal blood flow
3. Baroreceptors plus thirst
What is severe hypovolemia classed as? What is done to treat it?
If the volume of fluid that has been lost cannot be compensated for
- damage to tissues & organs can occur & the heart fails
Fluid replacement is required
- resuscitation fluids i.e. colloid or Hartmann's or blood
- fluid challenge algorithm: whilst monitoring central venous pressure
What 3 other factors affect blood pressure control?
- conscious effects of emotions: the nerves from cortex to medullary CVC centre
2. TIME OF DAY
- diurnal variations due to hormones & cortical inout
- via mechanical movements
- via chemoreceptors (aortic & carotid bodies detect changes in pO2, if theres a decrease in pO2 then rate of firing increases)
How is blood pressure controlled long term?
Through the control of blood volume
What mediates blood volume?
Hormonal regulation of kidney function, combined with direct effects of flow
What are the structures on the (i) right (ii) left side of the mediastinum related to?
(i) RA & veins
- SVC, arch of azygous, RA, IVC
(ii) LV & arteries
- L.common carotid, L.subclavian, arch of Ao, thoracic aorta, LV
Right and Left Vagus Nerves: 1. Carry _____ fibres to the thoracic and abdominal viscera 2. They are heading for the oesophagus and stomach so they lie.... 3 Carry innervation for the striated muscles of the _____ and _____ 4. Both vagus nerves give preganglioc branches to autonomica plexuses: P_____, C_____ and O_______
1. Carry PARASYMPATHETIC fibres to the thoracic and abdominal viscera 2. -Closer to the mid-line than the phrenic nerves - Pass posterior to the lung root 3. Carry innervation for the striated muscles of the pharynx and larynx 4. Pulmonary, Cardiac and Oesophageal
At what vertebral level do they leave the thorax?
The vagus nerves run between what 2 BVs in the neck?
The internal jugular vein & the internal (then common) carotid artery
When the right vagus reaches the oesophagus, what happens?
Forms the oesophageal plexus with the left vagus. They then reform as anterior (mainly left) and posterior (mainly right) vagal trunks as the oesophagus leaves thorax
What arteries is the left vagus nerve related to? (HINT: there's 3)
Left common carotid
Left side of aortic arch
Recurrent laryngeal nerves come from what? What do their (i) motor (ii) sensory branches supply?
From the vagus nerve
(i) branches to laryngeal muscles
(ii) to mucosa BELOW vocal folds
What is the location of the (i) RIGHT RLN (ii) LEFT RLN?
(i) curves superiorly under the subclavian artery (lies in the neck)
(ii) pulled further down into the thorax & passes under the arch of the aorta, posterior to the ligamentum arteriosum & superiorly in a groove between the trachea & oesophagus to reach the larynx
What is at risk in thyroid surgery? What can this risk result in?
damage to the recurrent laryngeals
- causing a weak or hoarse voice
What are two potential causes for hoarseness of the voice?
Tumour or Enlarged lymph nodes compressing the nerves
What are the postsynaptic neurotransmitters for (i) sympathetic and (ii) parasympathetic innervation?
What is the long "dendrite" of a sensory neurone usually referred to as?
Explain why efferent neurons, of the Autonomic (visceral) effect nervous system, are said to be in a two-neurone chain?
The cell body of the 1st neurone lies in the CNS The cell body of the 2nd neurons is located in a ganglion Axon from first neurone synapsis on cell body of 2nd neurone in the ganglion
Where is the cell body of a (i) motor neurone (ii) sensory neurone located?
(i) the anterior grey horn
(ii) the sensory DRG
Why do somatic afferent neurones give conscious sensations?
They synapse with other neurones leading to he higher, conscious part of the brain
What does the position of the ganglion determine?
The length of the axon
Where are PS nerves distributed to?
Head, neck & viscera
NO supply to skin or limbs
Where do the (i) preganglionic (ii) postganglionic cell bodies of PS neurones lie?
(i) EITHER in the
- nuclei of cranial nerves III, VII, IX, X
- or in the grey matter of the SC S 2, 3, 4
(ii) EITHER in the
- special ganglia of the head & neck
- or close to the viscera they supply, where they contribute to autonomic plexuses (e.g. cardiac, pulmonary, oesophageal)
What is meant by craniosacral outflow?
When the parasympathetic preganglionic neurones "hitch-like" with the cranial or sacral spinal nerves that supply only the head, neck, thoracic and abdominal pelvic viscera.
What is meant by thoracocolumbar outflow?
Sympathetic neurones preganglionic cell bodies lie in a sympathetic ganglion They either
(a) Hitch-hike along somatic nerves and/or arteries and are distributed widely all over the body OR
(b)They supply adjacent viscera through autonomic plexuses
How do neurones enter & leave sympathetic trunks?
1y neurones emerge from the cord in T1 to L2 spinal nerves
They pass to the symp trunk in white rami communicantes (WRC) & either synapse immediately in the adjacent ganglion or they travel up or down in the trunk to be distributed above T1 & below L2
After synapsing in a ganglion the 2y neurone joins a spinal nerve via a grey ramus communicantes (GRC) in which it is distributed to the body wall
What is the difference between WRC (white rami communicantes) and GRC (grey rami communicantes)?
WRC: Spinal cord to sympathetic trunk GRC: Sympathetic trunk to spinal nerve
What is the stellate ganglion a fusion of? Where does it lie?
Inferior cervical ganglion and the T1 ganglion
Lies on the neck of the 1st rib
At which point do the two sympathetic trunks fuse?
The ganglion impar
(opposite the coccyx)
There are sup, middle & inf cervical ganglia
Which sympathetic primary neurones don't synapse in the trunk?
Those passing straight through the trunk to reach the abdominal viscera & adrenal (suprarenal) gland via the greater, lesser, and least splanchnic nerves that synapse in the coeliac, superior mesenteric and inferior mesenteric ganglia (plexuses)
What 3 things may 1y neurones do to reach the body wall & limbs?
1. Synapse straight away & the 2y neurones pass in the GRC to the spinal nerve to be distributed with it to the thoracic wall
2. Travel up trunk to synapse above T1, 2y then pass in GRC to cervical spinal nerves to be distributed with them to UL, head & neck
3. Travel down trunk to synapse in ganglion below L2, 2y pass in GRC to the lumbar & sacral spinal nerves to be distributed with them to the lower limb etc
What spinal cord levels sympathetically innervate (i) the head (ii) ULs (iii) thoracic & abdominal walls (iv) LLs
(i) T1 - 3
(iii) T1 - 12 (this matches the dermatomes as 2y neurones are running with the adjacent spinal nerve)
(iv) T12 - L2
Summarise the thoracic visceral supply, with reference to the cardiac, pulmonary & oesophageal branches.
CARDIAC branches supply SA node & coronary vessels, they include T1 fibres which accounts for reffered pain from the heart to T1 which accounts for referred pain from heart to T1/2 dermatomes
PULMONARY branches from T2 - T4 supply pulmonary plexus
OESOPHAGEAL branches from T4 - T6
What cord levels supply (i) stomach (ii) midgut (iii) hindgut?
(ii) T10 & 11
What is pancoast's tumour?
Located at the apex of the lung & may affect the sympathetic trunk or stellate ganglion on the neck of the 1st rib at the thoracic inlet, compromising the sympathetic supply to the head & neck on the SAME side
What are the signs of horner's syndrome? (HINT: there's 4)
1. Ptosis (drooping) of the upper eyelid
2. Pupillary constriction (miosis)
3. Anhydrosis (lack of sweating)
4. Flushing of the face
What are the 3 vascular changes that come about with age?
Fibrosis of intima & media
Accumulation of ground substance
Fragmentation of elastic lamellae
What does atherosclerosis (atheroma) affect? What is it characterised by?
Affects large & medium sized elastic & muscular arteries
Characterised by lipid deposition, fibrosis & chronic inflammation
What are the 10 risk factors for atherosclerosis?
low socio-economic status
What is the morphology of atherosclerosis?
An atheromatous (fibro-fatty, fibro-lipid) plaque
- patchy & raised white to yellow 0.3-1.5cm
- core of lipid
- fibrous cap
What are the complications that can occur with atherosclerosis? (HINT: there's 6)
1. cerebral infarction
2. carotid atheroma - emboli causing transient ischaemic attacks or cerebral infarcts
3. MI, cardiac failure
4. Aortic aneurysms - rupture causes sudden death
5. Peripheral vascular disease with intermittent claudication
What is peripheral vascular disease? What does it cause? What effects does it have?
Atheroma of distal aorta/iliac/femoral arteries
It causes ischaemia of the lower limbs
Effects = intermittent claudication, pain, ulcers, gangrene
What are aneurysms? What are the 6 types?
Localised, permanent, abnormal dilation of BV or the heart
Where do atherosclerotic aneurysms occur? What are some predisposing factors? What is its morphology? What are the 5 possible clinical consequences?
Usually abdominal aorta, distal to renal arteries
MEN>women & smokers over 50
Morphology: saccular or fusiform
15-25cm in length
frequently contains mural thrombi
- thrombosis, embolism, rupture, obstruction of a branch vessel, impingement on an adjacent surface
Who is more likely to have a dissecting aortic aneurysm? What is its morphology?
Men are 3x more likely than women aged 40-60 with hypertension
Younger pts with systemic or localised abnormalities of connective
Morphology: usually initiates with an intimal tear 1-2cm from aortic valve. Dissectino can extend along the aorta retrograde toward the heart or distally, sometimes into the iliac & femoral arteries
What are the 2 common clinical symptoms of dissecting aortic aneurysms?
1. sudden onset of excruciating pain
-beginning in the anterior chest, radiating to the back between the scapulae, & moving downward as the dissection progresses; the pain can be confused with
that of MI.
2. The most common cause of death is rupture of the dissection outward into the pericardial, pleural or peritoneal cavities
What are berry aneurysms? Who do they affect? What are they associated with?
Aneurysms of the circle of willis
Affect young people
Associated with sub-arachnoid haemorrhage
What are capillary micro-aneurysms? What are they associated with?
Small aneurysms of branches of middle cerebral artery
- diabetes mellitus
- intra-cerebral haemorrhage
Describe (i) syphilitic (ii) mycotic aneurysms.
(i) usually affects the thoracic aorta
(ii) walls of artery are weakened by infection of bacteria or fungi. Often in brain, secondary to embolism
What are varicose veins? What are the 5 risk factors? Give some examples of where varicose veins can occur.
Abnormally dilated, tortuous veins produced by prolonged, increased intraluminal pressure and loss of vessel wall support. Venous valves are incompetent whic leads to stasis, congestion, oedema, pain & thrombosis.
RISK FACTORS = age, sex, heredity, posture, obesity
LLs - usually saphenous system
Varicocele (spermatic cord)
What is vasculitis? What is its pathogenesis?
Inflammation & necrosis of BVs
- cell immune mediated inflammation
- deposition of immune complexes
- direct attack by circulating antibodies
- direct invasion of vascular walls by infectious pathogens
- often part of multi-system disease
What are the 4 types of vasculitis?
1. GIANT-CELL (TEMPORAL) ARTERITIS
- >50, ave age onset 70, women>men
- granulonatous inflammation of large to small sized arteries
- cord like nodular thickening
2. TAKAYASU ARTERITIS (PULSELESS DISEASE)
- granulomatous vasculitis of medium & larger arteries of ULs (& arch Ao) woman age
3. POLYARTERITIS NODOSA (PAN)
4. KAWASAKI DISEASE
What are the types of (i) benign (ii) malignant vascular tumours?
- Juvenile (strawberry): skin
- Capillary (ruby spots): skin, spleen, kidneys
- Cavernous (port wine stains): skin, spleen, liver, pancreas
- capillary & cavernous
- skin, soft tissue, breast bone, liver & spleen
- kaposi's sarcoma: associated with HIV/AIDS, an angioproliferative tumour derived from endothelial cells
When does coronary perfusion occur?
During diastole, since during systole the coronary vessels are being constricted
What happens if the diastole window shortens?
Negative impact on the heart, since not enough coronary perfusion can occur and cardiac muscle can't be supplied with sufficient oxygen ---> lactic acid build up & angina
How does vasodilation of coronary arteries occur?
Build up of local factors
Which hormones/neurotransmitters contribute to (i) vasoconstriction (ii) vasodilation?
(i) NA & Adrenaline
What happens to total peripheral resistance during dynamic exercise?
Decreases due to vasodilation occurring
What will happen to diastolic pressure during dynamic exercise?
If anything, it will decrease slightly