Gus's Rugby Injury Flashcards
Describe the course of the right phrenic nerve from origin to diaphragm
It passes in front of right scalenus anterior muscle, then to the side of the superior vena cava and over the right border of the heart. It pierces the diaphragm beside the IVC in the tendinous portion.
Name a tributary of the superior vena cava.
The azygos vein
Why might hypoxia occur 12-24 hours after a haemorrhage?
Reduced haemocrit due to internal transfusion but since CO, blood volume and pressure are normal there is no detection of this by baroreceptors
Describe the course of the left phrenic nerve from origin to diaphragm
It passes over the left scalenus anterior muscle then passes to the side of the aorta and pulmonary trunk and over the left border of the heart. It pierces the diaphragm in the muscular portion of the left dome.
What lies in the posterior mediastinum?
Oesophagus and vagus nerves, azygos system of veins, the descending thoracic aorta and sympathetic chain
Where do the superficial lymphatics drain to?
The axillary lymph nodes
Why does diastolic blood pressure rise in isometric exercise but not in dynamic exercise?
Because of the compression of blood vessels in the contracting muscle raising TPR
Which vein drains the lower left side of the thoracic cage?
Hemiazygos vein
What damage caused by haemorrhage may be irreversible?
Damage to myocardium leads to ischemia, ischemic gut from reduced splanichic circulation may become leaky and lead to escape of toxic gut bacteria. Renal failure from under perfusion, ARDS from lung under perfusion
What factor is missing in haemophilia A?
FVIII
Where do the posterior deep lymph heads of the chest wall drain to?
The thoracic duct or right lymphatic duct
What would a graph of work and O2 consumption look like and why?
Linear up until a set point which is maximum work output as VO2 max has been reached
What is vitamin K required for in coagulation pathways?
y-carboxylation of prothrombin and factors VII, IX, X during synthesis in the liver
What is O2 consumption at rest and during exercise?
At rest: 250ml/min
Exercise: 2500ml/min
How will SV change with venous pooling?
Decreases SV by 40%
What may cause vitamin K deficiency?
Haemolytic disease of the newborn, bile duct obstruction, coeliac disease and Crohn’s disease
Where are the sympathetic chains in the back of the thoracic inlet?
At the back in the posterior mediastinum
Where in the brain are the phrenic nerves under control from?
Hind brain (lower pons and medulla)
Where does the trachea bifurcate?
The plane of the sternal angle
Where do pre ganglionic sympathetic nerves originate?
The lateral horn of spinal levels T1-L2 inclusively
How is lymphatic drainage of the chest wall divided?
Into superfical and deep
How long does it take for haemoglobin levels in blood to return to normal following blood loss of 20-30%?
5-6 weeks
What % blood loss can lead to irreversible damage or death in an healthy individual?
Above 30-50%
What is dynamic contraction?
Muscles shorten in rhythmic contraction and relaxation
When is the thymus gland most essential?
In neonates and grows until age 1 and prevents immune disorders in childhood. Begins to regress after puberty and is small and fat ridden in adults.
What is the pressure in a venule?
12.18 mmHg
Where do the anterior deep lymph heads of the chest wall drain to?
The bronchomediastinal lymph trunk
Why should jugular cannulation be done with the head down?
Jugular vein pressure is usually 0 so this prevents the possibility of an air embolus entering during inspiration
What kind of genetic disease is haemophilia?
X-linked, recessive
Why does vascular smooth muscle vasodilate in exercise?
Decreased PO2 and pH, increased PCO2, local metabolites, sympathetic stimulation of B2 receptors, nitric oxide
How are arterial and venous O2 content affected by exercise intensity?
Arterial blood content will not change and venous will decrease with increased exercise intensity.
What lies in the middle mediastinum?
Heart and pericardium
What do sympathetic efferent do in the thorax?
Stimulation of SAN and cardiac muscle increasing heart rate and strength of contraction. Increases smooth muscle tone in blood vessels of lungs causing vasoconstriction
How do you work out ventilation and alveolar ventilation?
Ventilation = tidal volume x respiratory frequency
Alveolar ventilation= (tidal volume - dead space volume) x respiratory frequency
What is the pressure in a vein?
10 mmHg
What is the main factor in determining VO2 max?
CO
How will limb and splanchnic flow change with venous pooling?
Decreases limb and splanchnic flow by 25%
How does the increase in heart rate in isometric exercise compare to that of dynamic exercise?
Heart rate increases steadily with length of contraction but not as steep and high as in dynamic excercise
How does training improve ability to exercise?
The anaerobic threshold is higher, more O2 is offloaded to tissues so Hb effectively more efficient, lungs have better perfusion as more capillaries so need to ventilate less, heart can pump higher SV with each pump
How will PvO2 change as VO2 max is reached?
Venous O2 pressure will decrease sharply to begin with then decrease at a slower rate as exercise intensity increases
Where does the azygos vein receive blood from?
The right side of the posterior chest wall with the exception of the first posterior intercostal vein which drains to the right brachiocephalic vein
How will TPR change with venous pooling?
Increases TPR by 25%
Where do phrenic nerves pass through in the thoracic inlet?
In front of the subclavian artery
What are the most common causes of severe internal bleeding?
Ruptured ectopic pregnancy, ruptured spleen, aortic aneurysm, fracture, bleeding peptic ulcer
Where do the upper spaces of the thoracic cage drain to?
The left brachiocephalic vein
What drains the anterior chest wall?
The internal thoracic veins
What lies in the anterior mediastinum?
Internal thoracic vessels, lymphatics and part of the thymus gland
How do valves help reduce venous pressure in legs?
Aid venous return by aiding skeletal muscle pumping and preventing back flow of blood due to gravity
How will PvCO2 change as VO2 max is reached?
CO2 pressure will rise sharply to begin with then rise at a slower rate as exercise intensity increases
How will PaCO2 and PaO2 change as VO2 max is reached?
Remain constant
What is reverse stress compensation?
Compensatory mechanism for reduced blood volume whereby veins shrink around reduced blood volume, maintaining venous pressure and venous return despite reduced CO and blood volume
What is isometric contraction?
Contraction with no muscle shortening, sustained contraction.
What does the brachiocephalic artery divide into?
Right common carotid and right subclavian arteries
Describe the course of the oesophagus
It lies behind the trachea in the superior mediastinum and, leaving the trachea behind, it courses downwards and to the left entering the inferior mediastinum behind the left atrium of the heart. It passes through the left muscular portion of the diaphragm.
What are the subdivisions of the mediastinum?
Superior and inferior mediastinum bounded by an imaginary line drawn from the sternal angle. The inferior mediastinum can be further divided into anterior middle and posterior
What are the three usual branches of the aorta?
The brachiocephalic artery, the left common carotid (to left side of face and neck) and the left subclavian (to left upper limb)
How do you calculate O2 consumption?
CO x (arterial- mixed venous blood O2 content)
What is progressive shock?
Initial recovery in terms of BP and CO but ultimately leads to death if untreated by transfusion
What is an internal transfusion?
Restoration of blood volume by fluid movement from interstitum to blood caused by fall in BP/ hydrostatic pressure difference. Associated with haemodilution
What is the superior vena cava formed of?
Union of right and left brachiocephalic veins
What forms the brachiocephalic veins?
The internal jugular vein from head and neck and the subclavian vein from upper limb
What do sympathetic afferents in the thorax do?
Signal pain from viscera to spinal nerves C7-T4
What % blood loss will elicit shock in an healthy individual?
20% and above
How can we calculate the blood pressure in the feet or the head of a person with normal BP?
Distance from heart x 0.77 and then add for feet or subtract for head this value from BP
Where can the oesophagus be constricted?
By the cricoid cartilage of the larynx, the arch of the aorta, by the left main bronchus, by the left atrium of the heart and by entry through the diaphragm
Which nerves are motor control for diaphragm?
Phrenic nerves
Where do phrenic nerves lie in the chest?
In front of lung root
What does stimulation of the vagus nerve do in the thorax?
Increases respiratory tract mucus secretion, causes bronchoconstriction, motor supply to smooth muscle in lower oesophagus and causes myocytes to slow rate of depolarisation
What are the main factors affecting maximum and resting heart rates?
Maximum: age, younger people have a higher maximum heart rate
Resting: physical fitness, fitter people have a lower resting heart rate
How is CO increased in exercise?
By consistent rise in heart rate and more modest increase in stroke volume due to increased filling pressure of the heart and increased contractility
What is the vasovagal response?
The overwhelmingly parasympathetic response on the vascular system experienced in fainting (vasodilation and vagally mediated bradycardia)
Which kind of shock gets better without treatment?
Non progressive
What bounds the mediastinum?
The mediastinum is the space between the lungs and is bounded in front by the sternum and behind by the vertebral column
How will CO change with venous pooling?
Decreases CO by 25%
What increases the reticulocyte count?
Erythropoietin released by kidneys
How will pH change as VO2 max is reached?
Decrease slowly, may be fairly constant to begin with due to buffering
Where are the baroreceptors and where do they send afferent signals to?
Carotid sinus and aortic arch, responses sent to nucleus tractus solaris via glossopharyngeal and vagus nerves respectively
What is oligaria?
Low urine output caused by sudden decrease in blood volume
Where are cervical post ganglionic neurones mainly clustered?
Into three ganglia, superior (C1-C4), middle (C5, C6) and inferior (C7-T1)
Does most of the blood reside in the arterial or venous system at rest?
60% in venous, 40% in arterial
What lies in the superior mediastinum?
The remnants of the thymus gland, the great veins (brachiocephalic and SVC) the arch of the aorta and its branches (brachiocephalic trunk, left common carotid and left subclavian), the lower part of the trachea and the oesophagus. All these structures lie behind the manubrium to some extent so are well protected
What factor is missing in haemophilia B (Christmas disease)?
FIX
What are the symptoms of severe internal blood loss?
Grey, cold skin, shallow, rapid breathing, quick pulse, intense thirst, nausea, reduced urine output, low BP, anxiety, confusion, aggression, decreased coagulation time
How will CVP change with venous pooling?
Decreases CVP
Where does the aorta arch?
At the sternal angle, lying in the superior mediastinum, arching backwards and to the left lying behind the left main bronchus
Where do the azygos vein and the superior vena cava join?
By the arch of the azygos at the plane of the sternal angle
How can circulatory shock be defined?
Not only low blood pressure but inadequacy of blood flow
What is venous pooling?
When standing still for too long there is reduced skeletal pumping so decreased venous return,
