I am really struggling to get this correct, Any help would be great.
The liver has the function of detoxification of drugs; most lipid-soluble drugs are metabolized by enzymes such as oxidases, hydroxylases, etc, most of which are part of the cytochrome oxidase complex in the microsomal fraction (a term used more in the description of the portions separated by centrifugation). This is also known as the P450 system, and each member enzyme is now refereed to as CYP#X#. Then they are glucuronized before being excreted by the kidneys. Since drugs taken orally first reach the liver via the hepatic portal vein [running from the intestines to the liver - for first pass metabolism], the liver faces high concentrations of drugs, making it susceptible to toxicity, e.g. overdose of paracetamol.
The brain has a delicate physiology, and is easily affected by increased levels of externally derived chemicals e.g. as in Wernicke's encephalopathy due to alcoholic poisoning.
The heart is very sensitive to changes in electrolytes, since the unique features of cardiomyocytes of automaticity, intrinsity and rhythmicity depend crucially on the movement of ions, particularly sodium and potassium. Hence, e.g. cardiotoxicity of digoxin is worsened by hypokalaemia; the antipsychotic drugs and some others that adversely affect sodium channels can cause drastic arrhythmia known as multifocal ventricular tachycardia (torsades de pointes), which can be fatal, although uncommon.
The pulmonary tissue, although it has a rich blood supply to the alveoli for efficient gas exchange, does not have great exposure to systemically administered drugs. Exceptions do exist e.g. the non-cardioselective (i.e. beta-1 plus beta-2) adrenoceptor blocking agents e.g. propranolol, acebutolol [unlike the beta-1 selective ones like metoprolol, betaxolol and atenolol], can exacerbate or precipitate an attack of asthma in susceptible individuals.
The cavity of the stomach is actually technically outside the body as it is continuous with the mouth and the anus, so is unlikely to be affected by drugs.
Hope this makes sense.