FRCS Revision Notes Essay

The ulnar nerve is formed from the medial cord nerve roots of C7-T1.

Originating in the brachial plexus, it descends down the arm before passing around the medial epicondyle of the elbow (the so-called funny bone) and then passes between the heads of flexor carpi ulnaris (FCU). It gives some cutaneous branches just before the wrist whilst the motor branches pass around the hook of hamate. Its motor contribution is to all small muscles of the hand except the lateral two lumbricals as well as FCU and flexor digitorum profundus (FDP).

Its sensory supply is to the one and a half ulna side fingersThe foramen ovale is part of the greater wing of the sphenoid and transmits the mandibular and lesser petrosal nerve. This nerve enters the infratemporal fossa through the petrotympanic fissure and runs downward and forward to join the lingual nerve. The foramen spinosum transmits the middle meningeal artery from the infratemporal fossa into the cranial cavity. The jugular foramen transmits the following structures from before backward: inferior petrosal sinus, CN IX, X, XI, and the large sigmoid sinus.

The facial nerve exits the cranium via the stylomastoid foramen.Hyponatraemia can be classified as a hypovolaemic, euvolaemic or hypervolaemic state. Hypovolaemic state is due to marked dehydration with excessive salt losses, for example, vomiting or Addison’s disease. Euvolaemic state typically reflects syndrome of inappropriate secretion of antidiuretic hormone (SIADH). Hypervolaemic state is due to conditions such as congestive cardiac failure (CCF), cirrhosis, nephrotic syndrome and myxoedema. Carbenoxolone causes pseudohyperaldosteronism with hypertension, hypernatraemia and hypokalaemia.Major surgery, pneumonia, subarachnoid, meningitis and injury (as well as drugs) can induce SIADH. Scaphoid Articulations: * Radioscaphoid joint * Scapholunate joint * Scaphocapitate joint * Scaphotrapezial joint * Scaphotrapezoidal joint Muscle attachments: Abductor pollicis brevis Ligament attachments: None Epiphyses: None Fractures: Scaphoid fracture Tubercle is blunt prominence to thumb side of distal surface.

Waist of the bone is palpable in anatomical snuff box. The posterior cricoarytenoids are the (only) cord abductors. They are innervated by the recurrent laryngeal nerve.Femoral hernias lie in the femoral canal which is the medial compartment of the femoral sheath, the opening to which is the femoral ring. The femoral canal contains lymphatics, and therefore causes of enlarged lymph nodes form part of the differential diagnosis (that is, lymphoma, infection). However, Virchow’s node (Troisier’s sign) is a supraclavicular lymph node, associated with intra-abdominal malignancy (that is, gastric) and does not form part of the differential. The intermediate compartment of the sheath contains the femoral veins and therefore a saphena varix may be mistaken for a hernia due to the close proximity.

The femoral artery lies in the lateral compartment. The walls of the sheath are formed by a continuation of the fascia transversalis interiorly and posterior iliacus/psoas fascia. A psoas abscess will therefore track along the fascia, under the ligament into the groin, lying in a similar position to a femoral hernia.

The dermatomes for C8, T1 and T2 lie along the medial border of the upper limb, with the medial part of the forearm being supplied by T1. The muscles of the hand are supplied by either the ulnar (C8-T1) or the median nerve (C5-T1), with the hypothenar eminence being supplied solely by the ulnar nerve.The superficial palmar arch is a direct continuation of the ulnar artery and lies lateral to the hook of hamate. As the artery enters the palm it curves laterally behind the palmar aponeurosis and superficial to the flexor tendons. The trapezium articulates (via a synovial saddle-shaped joint) with the base of the first metacarpal to form the carpometacarpal joint of the thumb. The median nerve is the most medial structure in the cubital fossa (followed by bifurcation of brachial artery, biceps tendon, and the radial nerve most laterally).

The distal end of the radius (styloid process) articulates medially with the round head of ulna. The ulnar bursa is the common synovial sheath of both superficialis and profunda tendons and ends at the level of the bases of the distal phalanges. The dorsal cutaneous branch of the ulnar nerve is given off in the forearm and passes superficial to the extensor retinaculum in the wrist. The styloid process has an inferior articular surface divided by a ridge – the medial part articulating with lunate and the lateral part with scaphoid.Compression of the median nerve occurring in carpal tunnel syndrome may result in wasting of the thenar muscles, as they are supplied by the median nerve although there is no paraesthesia over the thenar eminence as the skin is supplied by the palmar cutaneous branch passing superficial to flexor retinaculum.

The radial nerve is the main branch of the posterior cord of the brachial plexus. The others are the axillary nerve, the thoracodorsal nerve, and the subscapular nerves. The median nerve is a continuation of the medial and lateral cord.The long thoracic nerve originates from the ventral rami of C5 to C7. After exiting the axilla, the radial nerve descends behind the fibres of the medial head of the triceps in the posterior compartment. It then pierces the lateral intermuscular septum at the mid-point of the arm to reach the anterior compartment, and lies between brachialis and brachioradialis.

It passes through the cubital fossa (lateral side) beneath brachioradialis, then gives off the major posterior interosseus branch and continues downwards as the superficial radial nerve.This then descends until it reaches the back of the hand, and passes superficial to the anatomical snuffbox. The long thoracic nerve supplies the serratus anterior muscle which is important in rotation of the scapula during abduction of the shoulder. It is flexor digitorum profundus (FDP) that causes the distal interphalangeal (IP) joint to flex ( flexor digitorum superficialis [FDS] flexes the middle phalanx and assists in flexing the proximal phalanx). The median nerve is medial to the tendon of biceps (the brachial artery lying between the two structures).

At the level of the wrist, the flexor carpi radialis passes lateral to the median nerve. As the ulnar nerve crosses the medial ligament of the elbow joint it enters the front of the forearm by passing through the two heads of flexor carpi ulnaris (FCU), and continues to run between FCU and FDP. Congenital diaphragmatic hernia occurs in 1 in 2000 live births and is frequently diagnosed on antenatal ultrasound scans. Left-sided (Bochdalek) defects are commonest, and pulmonary hypoplasia is a common cause of death.

In babies, repair is usually delayed for at least 48 hours, until the ventilatory status is stable. It is repaired using a left upper quadrant abdominal incision. Pancreatic carcinoma is the fourth most common cancer after lung, colorectal and breast. Over 90% present late with no chance of cure, and only 25% present with Courvoisier’s law, which states that if, in painless jaundice, the gallbladder is palpable, the cause will not be gallstones. Progressive jaundice occurs in over 75% and only 5% will present with pancreatitis.It is unclear whether diabetes mellitus is an aetiological factor or if pancreatic cancer induces glucose intolerance.

It is the fourth commonest cause of cancer mortality, after lung, prostate, bowel. The suprascapular nerve arises from the upper trunk of the brachial plexus. The upper and lower subscapular nerves arise from the posterior cord of the plexus. The medial pectoral nerve arises from the medial cord of the plexus. The commonest malignant tumours of the salivary glands are adenoid cystic carcinoma and carcinoma arising in a pleomorphic adenoma.Squamous cell carcinoma is very rare and aggressive, growing rapidly with 50% having lymph node involvement at presentation.

Eighty percent of tumours are in the parotid gland and 80% of these are benign. A parotid lump with involvement of the facial nerve is highly suggestive of malignancy. Facial paralysis occurs due to the passage of the nerve through the gland, with * Absence of tone of facial muscles * Asymmetry * Loss of nasolabial fold * Drooping corner of the mouth and can occur in roughly 25% of cases. Management of a malignant parotid lump requires radical en bloc resection and radiotherapy.

However if a lump thought to be benign is treated by superficial parotidectomy, and is subsequently found to be malignant, the options include watch and wait, radiotherapy or further surgery. Prognosis with malignant tumours of the parotid gland is poor with a less than 30% five year survival. The carotid sinus baroreceptors are stretch receptors (not pressure) that control blood pressure and heart rate by a feedback mechanism. They are located in the internal carotid artery, distal to the carotid bifurcation but proximal to the carotid body, (the latter arises from the external carotid artery).

Similar baroreceptors are found in the aortic arch, atria and left ventricle. The carotid sinus nerve, which is a branch of the ninth cranial nerve, receives afferent fibres from the carotid sinus and carotid body, and ascends to the vasomotor centre. As the distending pressure in the artery increases, the discharge rate from the baroreceptors increases, which stimulates the cardioinhibitory centre, causing a fall in blood pressure, heart rate and cardiac output. In chronic hypertension, in order to maintain an elevated blood pressure, the reflex mechanism is reversibly reset.The anterior tibial artery is formed by the bifurcation of the popliteal artery in the calf, which passes forwards above the upper border of the interosseous membrane to reach the extensor compartment. The artery with both of its veins run inferiorly on the interosseous membrane and passes between the two malleoli anteriorly to become the dorsalis pedis. Tibialis anterior lies medial to the artery throughout. Extensor digitorum longus and peroneus tertius lie laterally.

The deep peroneal nerve runs laterally initially and then passes in front in the middle third.The tendinous centre of the perineum or perineal body is a small wedge-shaped mass of fibrous tissue located at the centre of the perineum. Other structures attached include the * External anal sphincter * Levator prostate which is a part of levator ani * Bulbospongiosus * Superficial and deep transverse perineii.

The femoral triangle contains from medial to lateral: * The femoral vein * Artery and * Nerve. The triangle is formed: * Laterally by sartorius * The inguinal ligament superiorly and * The adductor longus medially. The roof of the triangle are the superficial structures, namely: * The fascia lata Cribiform fascia * Subcutaneous tissue and * The skin. The floor is muscular and is formed, from medial to lateral by: * The adductor longus * Part of the adductor brevis * The pectineus, and * The iliopsoas. The femoral vessels are enclosed in the femoral sheath with the femoral nerve lying outside the sheath. Medial to the femoral vein within the sheath is the femoral canal, an area of dead space into which the vein can expand during increased venous return.

The femoral artery is a continuation of the external iliac artery.It exits the triangle via the apex and enters the subsartorial (Hunter’s) canal. The femoral artery lies at the midinguinal point, which is midway between the pubic symphysis and anterior superior iliac spine. The diaphragm develops from: * Septum transversum (central tendon) * Cervical myotomes (C345) * The pleuroperitoneal membranes * Oesophageal mesentery. The attachments of the diaphragm are: The sternal attachments are to the xiphoid process, not the body of the sternum. The costal part is from the lower six ribs and costal cartilages.The lumbar part is from the medial and lateral arcuate ligaments and the crura which are attached to the upper three lumbar vertebrae on the right and upper two on the left.

There aretwo main sites of congenital diaphragmatic hernias. * Posteriorly and usually left sided: Bochdalek’s hernia (pleuroperitoneal canal). This is caused by failure of pleuroperitoneal development. These present in neonates and children. * Anteriorly: hernia through the foramen of Morgagni’s (at the junction of the costal and xiphoid origins).

Motor innervation is from C345 via the phrenic nerves.The lower intercostal nerves only provide proprioceptive suppy to the periphery of the diaphragm. The right phrenic nerve pierces the central tendon and the left pierces the left dome alongside the vena cava. The aorta, with the azygos vein and thoracic duct (both on the right of the aorta), passes through the diaphragm in the midline at T12. The oesophagus passes through at T10 to the left of the midline, with the vagus nerves and oesophageal branch of the left gastric artery. The inferior vena cava passes through at T8 through the central tendon to the right of the midline.

The main blood supply is from the right and left inferior phrenic arteries (from the aorta) on the abdominal surface. The lower five costal and intercostal arteries supply the costal margins. The pudendal nerve is the nerve of the pelvic floor and perineum.

It arises from the second, third and fourth sacral nerves. In the pelvis it runs on piriformis and then passes laterally through the greater sciatic foramen to enter the gluteal region. Here it curls around the sacrospinous ligament and passes through the lesser sciatic foramen to enter the ischiorectal fossa medial to the pudendal vessels.This sheath of fascia in the lateral ischiorectal fossa containing the vessels and nerve is the pudendal canal.

Branches: * Inferior rectal nerve – supplies external anal sphincter, anal canal and perianal skin * Perineal nerve – supplies scrotum/labium majus * Dorsal nerve of the penis/clitoris. Levator ani (iliococcygeus and pubococcygeus) and coccygeus are supplied by branches of S3, 4 from the sacral plexus. Nitric oxide is produced from L-arginine by nitric oxide synthase and is produced by the vascular endothelium in response to haemodynamic stress, and produces smooth muscle relaxation and reduced vascular resistance.Nitric oxide is a free radical and may be inactivated through interaction with other oxygen free radicals, for example, oxidised low-density lipoprotein (LDL). It causes the production of cyclic guanosine monophosphate (cGMP) as a second messenger. The curved shape of the oxygen dissociation curve means that the loading of oxygen to the tissues is little affected by significant drops in alveoli PO2 concentration. The steep lower part of the dissociation curve means that peripheral tissues can take off large amounts of oxygen for only a small drop in capillary PO2, assisting the diffusion of oxygen into the tissues.

The position of the oxygen dissociation curve is shifted to the right by acidosis, hypercapnia, raising the temperature, and increasing the amount of 2,3-DPG (23 diphosphoglycerate, an end product of red cell metabolism, the concentration of which increases in chronic hypoxia, either at altitude, or in chronic lung disease). A reduced haemoglobin reduces the total oxygen carrying capacity of the blood, but does not change the shape of the curve. The pulmonary trunk lies posterior to the aorta. The ascending aorta lies completely within the pericardium as does the pulmonary trunk.The left atrium is the most posterior chamber of the heart, the right atrium is just anterior and to the right of the left atrium. The left atrial appendage is not readily seen on transthoracic echocardiography and requires transoesophageal echocardiography. Congenital diaphragmatic hernias occur in approximately 1 in 4,000 live births.

Ninety percent occur in the posterior portion of the diaphragm through the foramen of Bochdalek and 90% occur on the left. The commonest clinical presentation is with respiratory distress in the neonatal period and due to pulmonary hypoplasia and compression.The abdomen often has a scaphoid appearance. About 40% of patients have associated congenital anomalies. The diagnosis can be confirmed radiologically with bowel loops seen in the chest.

Neonates usually require sedation, ventilation and intestinal decompression prior to surgery between 36 and 72 hours after birth. Thoracic outlet syndrome (TOS) is caused by compression of the brachial plexus, subclavian artery or subclavian vein in the thoracic outlet. Almost all patients (95%) present with neurological symptoms.

The commonest cause of arterial symptoms is a cervical rib, which occurs in 0. % of the population. Although 70% of cervical ribs are bilateral, symptoms tend to be unilateral.

Neurological symptoms and signs include: * pain * paraesthesia * weakness * muscle wasting. Vascular symptoms and signs include: * distended arm veins which do not collapse even on limb elevation * venous thrombosis* cyanosis * oedema * arterial thrombosis (acute ischaemia or claudication) and embolisation (digital ischaemia) * post-stenotic dilatation and aneurysm formation * The left phrenic nerve passes inferiorly down the neck to the lateral border of scalenus anterior. It passes medially across the border of scalenus anterior, parallel to the internal jugular vein which lies inferomedially. At this point it is deep to the prevertebral fascia, the transverse cervical artery and the suprascapular artery.

* It descends between the left subclavian and the left common carotid arteries, and crosses the left surface of the arch of the aorta. It then courses along the pericardium, superficial to the left auricle and left ventricle, piercing the diaphragm just to the left of the pericardium. * It carries sensory fibres from the pleura, pericardium and a small part of the peritoneum.Thrombin time compares a patient’s rate of clot formation to that of a sample of normal pooled plasma.

Thrombin is added to the samples of plasma. If the plasma does not clot immediately, a fibrinogen deficiency is present. If a patient is receiving heparin, a substance derived from snake venom called reptilase is used instead of thrombin. Reptilase has a similar action to thrombin but, unlike thrombin, it is not inhibited by heparin. Thrombin is added to platelet-poor plasma at 37°C; the clotting time is recorded. Typically 14-16 seconds is the normal time. It is prolonged in * Afibrinogenaemia Hypofibrinogenaemia * Dysfibrinogenaemia. It is prolonged by * Heparin (corrects with protamine) * Fibrinogen degradation product (FDP) * Paraproteins (partial correction with protamine).

Splenectomy is associated with * Howell-Jolly bodies * Thrombocytosis * Macrocytosis (persistence of larger red blood cells [RBCs])* Acanthocytes * Target cells * Leucocytosis. Auer’s bodies are inclusions in leukaemic white cells and are pathogonomic of leukaemia. Which of the following conditions is not associated with an increased tendency to thrombosis? (Please select 1 option) | Behcet’s disease| | Homocystinuria| Kawasaki disease| | Metastatic malignancy| | von Willebrand disease Correct| Other acquired causes include * Congestive cardiac failure (CCF) * Trauma * Surgery * Myeloproliferative disorders * Oral contraceptives. Other inherited causes include * Antithrombin III/protein C/protein S deficiency * Factor V Leiden * Dysplasminogenaemia * Dysfibrinogenaemia * Heparin cofactor II deficiency. von Willebrand disease (vWD) is a congenital or acquired condition. It arises from a deficiency of von Willebrand factor (vWF), a protein that is required for platelet adhesion.

All cytotoxic agents have adverse effects.General side-effects include nausea, vomiting and bone marrow suppression, alopecia and stomatitis. More specific side-effects are listed in the questions above. Alkylating agents such as cyclophosphamide may cause a haemorrhagic cystitis. Asparaginase results in a dose related pancreatitis. The anthracyclines, for example, doxorubicin and daunorubicin are cardiotoxic, which is often very difficult to detect. Monitoring with echocardiograms is advised. Vincristine is an alkaloid agent and results in sensory motor neuropathy with long term use.

It also has an affect on the autonomic system resulting in severe constipation and paralytic ileus.It may also result in sensory changes with parathesis progressing to loss of tendon reflexes. Bleomycin is the main drug resulting in lung damage and occurs in up to 10% of patients. The damage is dose related. Certain assumptions are required for appropriate interpretation of statistical analyses. In particular, t-tests and ANOVA require that the data should have a normal/Gaussian distribution and the tests are invalid if the data are non-parametric, where alternative tests such as the Mann-Whitney U test or the Wilcoxon signed rank test are appropriate.These latter tests can be used for normally distributed data but their ability to reject the null hypothesis accurately is impaired.

Small sample size would not invalidate test results, as it would be less likely to show differences between groups but the results would still be valid. Similarly, small SDs and narrow confidence intervals would increase the likelihood of demonstrating a difference but have no effect on validity of the test. The composition of the groups really makes no difference The popliteal fossa is a rhomboid shaped anatomical space. The upper oundaries of the popliteal fossa are the biceps tendon laterally and semimembranosus and semitendinosus medially. The inferior boundaries of the popliteal fossa are formed by the heads of the gastrocnemius which are less easily identified on palpation. The popliteal fossa contains the common peroneal nerve and the tibial nerve as well as the popliteal artery and vein.

The common peroneal nerve can be found on deep palpation of the lateral aspect of the head of the fibula and is particularly vulnerable to injury at the site. Undescended testes affect 3% of full-term boys.However, the majority of these lie in the inguinal canal and approximately 75% of undescended testes descend into the scrotum during the first year of life.

Undescended testes are associated with an increased risk of testicular malignancy which develops in 5% of intra-abdominal testes. Overall, 80% of males with bilateral descended testes are fertile but only 30% of men with bilateral undescended testes have normal fertility. Surgery should be performed during the second year of life. Boys with a palpable testis should undergo a routine orchidopexy.

Impalpable testes should be assessed with laparoscopy. Crush syndrome’ may also be referred to as traumatic rhabdomyolysis. The sustained crushing of a significant muscle mass causes impaired perfusion and therefore ischaemia of the muscle. Damaged muscle cells release myoglobin (an assay should be used to confirm its presence) and potassium, causing hyperkalaemia. Myoglobin can induce renal failure, therefore making intravenous fluid resuscitation critical. Alkalisation of urine with sodium bicarbonate reduces tubular precipitation of myoglobin and may be used in treatment.

Other toxic metabolites released from damaged muscle cells may affect the myocardium leading to a reduced cardiac output and shock. The diagnostic criteria for crush syndrome are: * Crushing injury to a large mass of skeletal muscle * There are sensory and motor disturbances in the compressed limbs, which subsequently become tense and swollen * Myoglobinuria and/or haematuria * Peak creatine kinase (CK) greater than 1000 U/l. Renal problems are common with one of the following characteristics: * Oliguria (urine output less than 400 ml/24 hr) * Elevated levels of blood urea, creatinine, uric acid, potassium, phosphate, or decreased calcium.The left phrenic nerve passes inferiorly down the neck to the lateral border of scalenus anterior. It passes medially across the border of scalenus anterior, parallel to the internal jugular vein which lies inferomedially.

At this point it is deep to the prevertebral fascia, the transverse cervical artery and the suprascapular artery. It descends between the left subclavian and the left common carotid arteries, and crosses the left surface of the arch of the aorta. It then courses along the pericardium, superficial to the left auricle and left ventricle, piercing the diaphragm just to the left of the pericardium.

It carries sensory fibres from the pleura, pericardium and a small part of the peritoneum. At its origin, the right ureter is usually covered by the descending part of the duodenum, and, in its course downward, lies to the right of the inferior vena cava, and is crossed by the right colic and ileocolic vessels. Near the superior aperture of the pelvis it passes behind the lower part of the mesentery and the terminal part of the ileum. The left ureter is crossed by the left colic vessels, and near the superior aperture of the pelvis passes behind the sigmoid colon and its mesentery.The ureter forms, as it lies in relation to the wall of the pelvis, the posterior boundary of a shallow depression named the ovarian fossa, in which the ovary is situated.

It then runs medialward and forward on the lateral aspect of the cervix uteri and upper part of the vagina to reach the fundus of the bladder. In this part of its course it is accompanied for about 2. 5 cm by the uterine artery, which then crosses in front of the ureter and ascends between the two layers of the broad ligament. The ureter is distant about 2 cm from the side of the cervix of the uterus.The ureter is sometimes duplicated on one or both sides, and the two tubes may remain distinct as far as the fundus of the bladder.

On rare occasions they open separately into the bladder cavity. They are contained within the same membrane as the kidney but separated from them by a fibrous layer of tissue. The right gland is tetrahedral in shape and lies lower than the left, which is semi-lunar in shape and usually the larger of the two. Each gland weighs approximately 5 grams and measures approximately 50 mm vertically, 30 mm across and 10 mm thick.The right lies between the diaphragm posteriorly and the IVC anteromedially. Superiorly lies the bare area of the liver. Its inferior end is covered by peritoneum reflected over it from the liver. The left lies in the stomach bed, with anterior relations of the stomach and pancreas and posteriorly with the diaphragm.

Its inferior part is not covered by peritoneum as it is crossed anteriorly by the tail of the pancreas and splenic vessels. The adrenal medulla contains the chromaffin cells. Embryologically, the medulla is derived from neural crest cells and cortex from mesoderm.Internal Jugular Vein * The internal jugular vein originates at the jugular foramen as a continuation of the sigmoid sinus, descending medially and forwards within the carotid sheath to the root of the neck. * It lies lateral first to the internal and then to the common carotid artery within the carotid sheath. * It passes behind the clavicle where it joins the subclavian vein to form the brachiocehpalic vein.

* The thoracic duct empties into the venous system of the neck at the union of the left internal jugular and subclavian veins.The specificity of a test is the probability that a test will produce a true negative result when used on an unaffected population, whereas the sensitivity of a test is the probability that it will produce a true positive result when used on an affected population (as determined by a reference or “gold standard”). The positive predictive value of a test is the probability that a person is affected when a positive test result is observed. The negative predictive value of a test is the probability that a person is not affected when a negative test result is observed.Accuracy is expressed through the above four parameters. Pelvic mass and features of thyrotoxicosis suggest a diagnosis of struma ovarii.

This rare condition is an ovarian tumour which contains thyroid tissue and can cause thyrotoxicosis. The second case of a patient with previous hyperparathyroidism, features suggestive of a phaeochromocytoma with a thyroid swelling (medullary thyroid cancer) supports a diagnosis of MEN type 2. This condition is associated with the RET proto-oncogene and is autosomal dominant.

It differs from MEN type 1, in that the latter is characterised by pituitary, parathyroid and pancreatic neoplasia. The last case is a young woman with features suggestive of renal carcinoma and has retinal haemangiomas. The diagnosis is von Hippel-Lindau disease, an autosomal dominant condition characterised by the deletion of the vHL tumour suppressor gene. Other features include cerebellar and spinal cord haemangiomas and phaeochromocytoma. The side effects of total parenteral nutrition (TPN) are numerous and include catheter-related sepsis and metabolic abnormalities resulting from the administered nutrients.Fatty acid deficiency may develop during prolonged TPN, though administering 3% of the total caloric input as linoleic acid prevents or corrects this deficiency. Hyperchloraemic metabolic acidosis may occur because of the liberation of hydrochloric acid during the metabolism of amino acids in the TPN.

Hypercarbia occurs from the increased production of carbon dioxide resulting from the metabolism of large amounts of glucose. A requirement for ventilatory support or weaning difficulties may subsequently occur. Hyperglycaemia is a potential problem until endogenous insulin production increases, requiring frequent glucose monitoring.Hypovolaemia due to an osmotic diuresis and a non-ketotic hyperosmolar hyperglycaemic coma are both potential complications of TPN, which may necessitate the addition of insulin to the TPN solutions.

Accidental or sudden discontinuation of the TPN infusion may cause hypoglycaemia. The pancreatic insulin response may persist despite discontinuing the TPN, resulting in a high plasma insulin concentration. Consequently intravenous glucose administration may be required, or alternatively a gradual discontinuation of the TPN over 60 to 90 minutes.The diaphragm is a domed fibromuscular sheet separating the thorax from the abdomen.

It develops mainly from septum transversum (central tendon) and cervical myotomes (muscular component). The mesothelial linings are derived from the pleuro-peritoneal membranes (failure of its development leads to Bochdalek’s foramen and hernia). Oesophageal mesentery also contributes to the formation of the diaphragm. Morgagni’s foramen is a congenital defect arising at the junction of the costal and xiphoid origins. Because of its cervical myotomal origin, it receives nerve supply from cervical roots; the phrenic nerves.

The phrenic nerves pierce the muscular components not the central tendon to reach and supply the diaphragm from below. The lower intercostal nerves give only proprioceptive supply to the periphery of the diaphragm. The openings in diaphragm are: * Aortic opening – T12 * Oesophageal opening – T10 * Vena caval opening – T8. At its origin, the right ureter is usually covered by the descending part of the duodenum, and, in its course downward, lies to the right of the inferior vena cava, and is crossed by the right colic and ileocolic vessels.

Near the superior aperture of the pelvis it passes behind the lower part of the mesentery and the terminal part of the ileum. The left ureter is crossed by the left colic vessels, and near the superior aperture of the pelvis passes behind the sigmoid colon and its mesentery. The ureter forms, as it lies in relation to the wall of the pelvis, the posterior boundary of a shallow depression named the ovarian fossa, in which the ovary is situated. It then runs medialward and forward on the lateral aspect of the cervix uteri and upper part of the vagina to reach the fundus of the bladder.In this part of its course it is accompanied for about 2. 5 cm by the uterine artery, which then crosses in front of the ureter and ascends between the two layers of the broad ligament. The ureter is distant about 2 cm from the side of the cervix of the uterus. The ureter is sometimes duplicated on one or both sides, and the two tubes may remain distinct as far as the fundus of the bladder.

On rare occasions they open separately into the bladder cavity. The pituitary stalk connects the anterior pituitary to the hypothalamus and it is contained in the pituitary sella with the optic chiasm and hypothalamus as superior relations.Glycoproteins such as thyroid-stimulating hormone (TSH) and luteinising hormone (LH) follicle-stimulating hormone (FSH) are produced by the anterior pituitary. These share a common alpha subunit with unique beta subunits. There is diurnal variation in the secretion of many hormones such as LH, adrenocorticotropic hormone (ACTH) and growth hormone (GH). T3 is the major active thyroid hormone but the majority is produced via peripheral de-iodination of T4.

Most binding proteins, including TBG, are increased in pregnancy and therefore it is much more important to measure free thyroid hormone concentrations than total.Illness and starvation produce a decline in both T4 and T3 concentrations. The isomer D-T4 is inactive, it is L-T4 that is the active molecule.

The source of the inferior hypogastric plexus are the hypogastric nerves and sacral splanchnic nerves (postganglionic sympathetic axons); pelvic splanchnic nerves. (Preganglionic parasympathetic axons from the ventral primary rami of spinal nerves S2-S4. ) The inferior hypogastric plexus lies between the pelvic viscera (vagina and rectum) and the pelvic wall. It lies between the two iliac vessels.It contributes branches to * Uterine/vaginal plexus * Vesical plexus/male * The prostatic plexus. Amongst many other reasons, the relations of the inguinal ligament are important in determining the origin of hernias. The inguinal ligament is the thickened lower border of the aponeurosis of the external oblique.

It extends from the anterior superior iliac spine to the pubic tubercle in a curved line which folds posteriorly. Its medial attachment forms a narrow sling for support of the spermatic cord or round ligament of the uterus.The femoral artery lies at the midpoint of the inguinal ligament and the capsule of the hip joint beneath iliopsoas. The psoas is supplied by segmental branches from the lumbar plexus. Pectineus arises from the superior ramus of the pubis. They are contained within the same membrane as the kidney but separated from them by a fibrous layer of tissue. The right gland is tetrahedral in shape and lies lower than the left, which is semi lunar in shape and usually the larger of the two.

Each gland weighs approximately 5 grams and measures approximately 50 mm vertically, 30 mm across and 10 mm thick.The right lies between the diaphragm posteriorly and the inferior vena cava anteromedially. Superiorly lies the bare area of the liver.

Its inferior end is covered by peritoneum reflected over it from the liver. The left lies in the stomach bed, with anterior relations of the stomach and pancreas and posteriorly with the diaphragm. Its inferior part is not covered by peritoneum as it is crossed anteriorly by the tail of the pancreas and splenic vessels. The adrenal medulla contains the chromaffin cells. Embryologically, the medulla is derived from neural crest cells and cortex from mesoderm.Scalenus anterior is a flat muscle that arises from four slips from the four typical cervical vertebrae (C3-6) and is inserted on the scalene tubercle on the first rib. It is one of the accessory muscles of respiration, but is more important as an anatomical landmark.

Its anterior relations are * Phrenic nerve * Ascending cervical artery * Transverse cervical artery * Suprascapular artery * Internal jugular vein. The subclavian vein lies in the groove on the first rib in front of the attachment of scalenus anterior. The trunks of the brachial plexus lie lateral to scalenus anterior.The subclavian artery is divided into three parts – first part is medial to it, second part is behind (posterior) to the muscle and the third part is lateral to it. The thymus is a lymphatic organ that develops mainly from the endoderm of the third pharyngeal pouch. Some of the epithelial cells become the thymic (Hassall’s) corpuscles; others form a network of epithelial reticular cells believed to secrete the thymic hormones that are linked to differentiation of T lymphocytes.

The developing thymus descends in front of all the major structures of the neck to enter the anterior mediastinum.It doubles its size rapidly after birth and stays the same size throughout the life but the lymphoid components decrease with age. However, the secretion of thymic hormones and its effect on lymphocytes that migrate to it continue throughout life. The radial nerve is the continuation of the posterior cord of the brachial plexus. The brachial plexus is formed by the anterior roots of C5 to T1 spinal nerves. The roots of C5 and C6 join together to form the upper trunk. C7 continues as the middle trunk while C8 and T1 join to form the lower trunk.

Each of these trunks divides into anterior and posterior division.All the posterior divisions join to form the posterior cord while the anterior divisions of the upper and middle trunks join to form the lateral cord and the anterior division of the lower trunk continues as the medial cord. It is the principal motor supply to muscles of the extensor compartments of the arm, forearm and the dorsum of the hand. Surface marking of radial nerve is from the point where the posterior wall of axilla and the arm meet to a point two thirds of the way along the line, joining the acromion to the lateral epicondyle and thence to the front of the epicondyle.The radial nerve supplies all the muscles of the posterior compartment of the arm, gives sensory branches to the skin overlying the posterior compartment and lateral aspect of the arm, and divides in the anterior compartment of forearm into posterior interosseous nerve and its terminal superficial branch.

Through these branches it supplies extensor muscles and skin on the lateral aspect of the forearm. It supplies the skin over the proximal phalanges on the extensor aspect of the radial three and half digits.The dorsal aspect of the distal two phalanges is supplied by median nerve (its branches). Anaplastic carcinomas of the thyroid are associated with poor prognosis. Follicular carcinoma spreads via the blood stream.

MEN2 is associated with medullary carcinoma of the thyroid. Raised calcitonin levels are associated with medullary thyroid carcinoma. Approximately 60% of patients presenting with a thyroid malignancy have a papillary carcinoma. MEN1 is an inherited tumour syndrome, characterised by the development of tumours of the parathyroid, the anterior pituitary and the pancreatic islets.

Krebs’ cycle (tricarboxylic acid cycle or citric acid cycle) is a sequence of reactions in which acetyl coenzyme A (acetyl-CoA) is metabolised to carbon dioxide and hydrogen atoms. The sequence of reactions is known collectively as oxidative phosphorylation, which only occurs in the mitochondria (not cytoplasm). The cycle requires oxygen and does not function under anaerobic conditions. It is the common pathway for the oxidation of carbohydrate, fat and some amino acids, required for the formation of high energy phosphate bonds in adenosine triphosphate (ATP).Pyruvate enters the mitochondria and is converted into acetyl-CoA, which represents the formation of a two carbon molecule from a three carbon molecule (with the loss of one CO2 and the formation of one NADH molecule).

Acetyl-CoA is then condensed with the anion of a four carbon acid, oxaloacetate, to form citrate which is a six carbon molecule. Citrate is subsequently converted into isocitrate, alpha-ketoglutarate, succinyl-CoA, succinate, fumarate, malate and finally oxaloacetate. Alpha-ketoglutarate is the only five carbon molecule in the cycle.Cervical lymphadenopathy is relatively common in children.

Diseases of the lymph nodes include acute lymphadenitis, that is, inflammation arising from an acute infection and chronic lymphadenitis, frequently associated with hyperplasia of the node. Nodes may be enlarged secondary to malignant infiltration. In this case, as the child is well, it is unlikely that a follicular tonsillitis is the cause. A thorough history and examination needs to be undertaken with particular reference to more extensive lymphadeopathy, hepatosplenomegaly, mediastinal masses, etc.First line investigations would include blood tests to exclude blood dyscrasias, as well as blood tests for inflammatory markers, for example, erythrocyte sedimentation rate (ESR),C-reactive protein (CRP), antistreptolysin-O test (ASOT) titres.

If clinically there are signs of bacterial infection then the treatment of choice would be a course of antibiotics. Failure to find one or both testes in the scrotum may indicate any variety of congenital or acquired conditions, for example * Ectopic testes * Maldescended testes * Retractile or absent testes. . 5% of males have an undescended testis at birth, falling to 0.

8% by six months. Maldescended or ectopic testes and true undescended testicles are differentiated from each other surgically. The ectopic testis has completed its descent through the inguinal canal but ends up in a subcutaneous location. Spontaneous testicular descent does not occur after the age of one year. Complications include infertility in adulthood, associated hernias and torsion and tumour development in the affected testis (if not operated on before 11 years).The patient with cryptorchidism has a 20-40% chance of developing malignancy, and those most at risk are those untreated or those whose surgery was carried out during or after puberty. The rectum is about 12 cm long.

It extends from the level of the third sacral vertebral body to the anorectal line. The taeniae of the sigmoid colon widen to form a complete outer layer of longitudinal muscle. There is a transition zone where the sigmoid mesocolon ends and the rectum has no mesentery. The rectum is retroperitoneal and the lower third is below the peritoneal reflection.The main blood supply is from the superior rectal artery. This divides into two lateral branches at the level of S3.

The middle rectal artery is a branch of the internal iliac artery. It passes along the lateral rectal ligament. The inferior rectal artery is a branch of the internal pudendal artery. Sympathetic supply is from the hypogastric plexus and fibres from the coeliac plexus running with its arterial supply. Its parasympathetic (motor) supply is derived from the pelvic splanchnic nerves of S234 origin.

The pelvic fascia around the rectum is described as the mesorectum.This contains the pararectal lymph nodes. These are excised in total mesorectal excision of rectal tumours. Lymphatic drainage follows the arterial supply to the preaortic and internal iliac nodes. The vagus nerve (tenth cranial nerve) has both sensory and motor divisions. It emerges from the anterolateral surface of the medulla as a series of 8-10 rootlets in a groove between the olive and the cerebellar peduncle. It passes through the jugular foramen and descends within the carotid sheath between the internal carotid artery and internal jugular vein (common carotid from the upper border of the thyroid cartilage).

The right recurrent laryngeal nerve passes below and behind the subclavian artery and passes upwards behind the common carotid artery. The left recurrent laryngeal nerve passes around the ligamentum arteriosum. The cricothyroid muscle is supplied by the external laryngeal nerve. The other laryngeal muscles are supplied by the recurrent laryngeal nerve.

All the muscles of the palate are supplied by the cranial part of the accessory nerve via the pharyngeal plexus and the pharyngeal branch of the vagus nerve except tensor veli palatini. This is supplied by the mandibular branch of the trigeminal nerve.Infrahyoid muscles * Sternothyroid * Sternohyoid * Omohyoid are supplied by the ansa cervicalis. Thyrohyoid is supplied by the hypoglossal nerve. The trachea of an adult is approximately 15 cm long and extends from the lower border of the cricoid cartilage at the level of the sixth cervical vertebra. It terminates at the bronchial bifurcation or carina, which is between T4 and T6 (the variation is due to changes during breathing).

The trachea has 16-20 C-shaped cartilaginous rings that maintain its patency. The tracheobronchial tree comprises 23 generations of air passages (not 25) from the trachea to the alveoli.The trachea is the first. The blood supply to the trachea is from the inferior thyroid arteries, which are branches of the thyrocervical trunk, which arise from the first part of the subclavian artery. The ascending cervical artery can easily be mistaken for the phrenic nerve at operation.

The phrenic nerve passes inferiorly across scalenus anterior and medius. The subclavian artery and vein are separated by scalenus anterior. The subclavian vein joins with the internal jugular to form the brachiocephalic vein. The trunks of the brachial plexus emerge from the lateral border of scalenus anterior.Gastric MALT tumours are associated with H. pylori infection in approximately 98% of cases, and all that is usually required in low grade disease is eradication therapy. High grade disease is best treated with chemotherapy, and the prognosis for these tumours is excellent. Paraproteinaemia is commonly found.

Solar keratosis is the most common pre-malignant lesion usually seen in older light-complexioned individuals. The progression from actinic keratosis to invasive malignancy occurs by several routes, and the resulting cancer is a squamous cell carcinoma (SCC) in almost all cases.Dermatitis herpetiformis is seen in patients with coeliac disease.

There are extremely itchy, burning blisters over the elbows, scalp, shoulders and ankles. They are not pre-malignant. Keratoacanthoma is not a pre-malignant lesion but often mimics SCC. Although the lesion might involve and disappear without specific therapy (hence the name ‘self-limiting’ SCC), early conservative excision of sufficient depth to eliminate the entire lesion is recommended. Molluscum contagiosum are wart-like lesions commonly found on the hands of children or adolescents. They are caused by a virus and are not pre-malignant.

Pyogenic granulomas are fruit-like cutaneous vascular lesions, which occur either spontaneously or secondary to some form of trauma. They grow rapidly, erupting through the skin and forming a stalk or pedicle. They may regresses spontaneously, but sometimes require cauterisation and/or surgical excision. Solar keratosis is the most common pre-malignant lesion usually seen in older light-complexioned individuals. The progression from actinic keratosis to invasive malignancy occurs by several routes, and the resulting cancer is a squamous cell carcinoma (SCC) in almost all cases.

Dermatitis herpetiformis is seen in patients with coeliac disease. There are extremely itchy, burning blisters over the elbows, scalp, shoulders and ankles. They are not pre-malignant. Keratoacanthoma is not a pre-malignant lesion but often mimics SCC.

Although the lesion might involve and disappear without specific therapy (hence the name ‘self-limiting’ SCC), early conservative excision of sufficient depth to eliminate the entire lesion is recommended. Molluscum contagiosum are wart-like lesions commonly found on the hands of children or adolescents. They are caused by a virus and are not pre-malignant.Pyogenic granulomas are fruit-like cutaneous vascular lesions, which occur either spontaneously or secondary to some form of trauma. They grow rapidly, erupting through the skin and forming a stalk or pedicle. They may regresses spontaneously, but sometimes require cauterisation and/or surgical excision. Aldosterone is produced in the zona glomerulosa of the adrenal cortex and acts via intracellular steroid receptors to increase sodium reabsorption. It is regulated by the renin/angiotensin system.

Its release is therefore stimulated by hypovolaemia and blood loss, and is inhibited by increased sodium intake/hypertension.

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