Gas Exchange
Define a shunt
Blood that does not undergo gas exchange (or, blood that travels from the right to left heart without being oxygenated)
What are the three layers of a blood vessel?
Tunica adventitia
Tunica media
Tunica intima
At what SaO₂ does central cyanosis develop?
<85%
What is an adjuvant?
A vaccine component that improves the body's immune response
E.g. alum
What are the boundaries of the anterior triangle of the neck?
Mandible
Midline of neck
Sternocleidomastoid (SCM) muscle
Describe a cause of hypoxaemia
Hypoxaemia = low concentration of oxygen in arterial blood
Causes include: hypoventilation (reduces O2 in alveoli), diffusion limitations (e.g. reduced surface area of alveoli), shunts (blood that bypasses oxygenation), ventilation-perfusion (V/Q) inequality, low FiO2 (reduced fraction of air that is oxygen)
Describe the key features of epicardium tissue
Simple squamous mesothelial cells
Connective tissue
Adipose tissue
Blood vessels
Describe the anion gap (equation) and why is it measured
Cations minus anions: (Na + K) - (Cl + HCO3)
Primarily to investigate the cause of metabolic acidosis
Describe the features of live attenuated vs inactive vaccines
Live attenuated = virus with reduced pathogenicity (so still causes infection), very immunogenic/long-lasting
Inactive = virus "killed" with chemicals (cannot cause infection), sometimes less immunogenic/long-lasting
Describe the vascular supply to the thyroid gland
Arterial supply:
Subclavian --> thyrocervical trunk --> inferior thyroid artery
External carotid --> superior thyroid artery (1st branch)
Venous drainage:
Superior + middle veins --> internal jugular vein
Inferior vein --> brachiocephalic vein
Explain the development of Eisenmenger's syndrome and its clinical manifestations
Explain the main histological differences between elastic (large) and muscular (medium) arteries with regard to their function
Elastic = vasa vasorum in tunica adventitia, lots of elastic lamellae in tunica media
--> stretch and recoil under high pressure from heart
Muscular = internal & external elastic laminae, tunica media is mostly smooth muscle
--> vasoconstrict/dilate to control blood blow to organs
Explain how being cold leads to peripheral cyanosis
Cold temperature triggers thermoregulatory vasoconstriction in the extremities, slowing blood flow
This slower-moving blood has more time for oxygen to be pulled out of it, increasing the deoxyhaemoglobin concentration
Explain how mRNA vaccines work
mRNA contained in a lipid vesicle, this gets taken up into cells
The cell translates the mRNA to protein
This protein antigen stimulates an immune response
Explain the structure and function of the epiglottis
Elastic cartilage flap that folds to prevent food/liquid from entering the trachea during swallowing
A 3yo child presents with cyanosis, dyspnoea and light-headedness that is exacerbated by exercise and relieved by squatting. What is the likely diagnosis and why?
Tetralogy of Fallot
Exercise increases oxygen demand
Squatting compresses vessels in lower body --> increase SVR --> reverse right-to-left shunt --> more blood to lungs
(PDA would be acyanotic, no "Tet spells")
A patient experiencing ventricular arrythmia could have dysfunction in which cells present in the endocardium?
What are the key histological features of these cells?
Purkinje fibres
Large, round nuclei, contain glycogen = makes them pale
A patient's ABG test gives the following results [normal values]:
pH = 7 [7.35-7.45]
PCO2 = 48 [35-45]
PHCO3 = 23 [22-26]
What type of acid/alkalosis are they experiencing (if any)?
Respiratory acidosis (high CO2 + low pH) without metabolic compensation (normal HCO3)
A woman present to the hospital with her infant. He has encephalitis, seizures and vesicular lesions around the eyes and mouth. The doctor states that the infant was infected during delivery, most likely with what virus...?
Rubella | CMV | HSV | Zika
Herpes simplex virus (HSV) - during delivery, neurological/rash
Rubella - during pregnancy, heart problems
CMV - during pregnancy, hearing/blindness/intellectual
Zika - during pregnancy, microcephaly
After a total thyroidectomy, a patient experiences tetany (muscle twitches/cramps). Why would this occur?
Removal of the parathyroid glands
These are very small glands on the posterior thyroid that regulate calcium levels in the body --> muscle contraction
What are the treatment options for a premature infant with patent ductus arteriosus?
NSAIDs (prostaglandins keep shunt open)
Surgery - catheter closure, ligation
How is right ventricular hypertrophy as part of Tetralogy of Fallot treated?
Correct the VSD (patch) and pulmonary stenosis (widen outflow)
Optional: Resection of excess myocardium
Temporary fix in infancy: Blalock-Taussig-Thomas shunt
A patient with a right-to-left cardiac shunt is hypoxaemic, with PaO2 = 60mmHg (normal range 80-100). If this patient is put on supplemental oxygen (100% oxygen), will this improve their arterial oxygen saturation?
No - in a R-L shunt, the blood is bypassing the lungs and doesn't have the opportunity to be oxygenated. Thus, increasing alveolar PO2 will not improve arterial oxygen saturation.
How is rubella infection treated?
you can't treat it :(
--> MMR vaccination, isolation of sick contacts