Define fissure in ano

Fissure in ano is a longitudinal tear in the epithelial skin and anal mucosa, most commonly in the posterior (6 o'clock) position. Fissures may occur in the 12 o'clock position in approximately 10% of cases and are more common in women following childbirth.

What is the underlying pathophysiology of this condition?

It is thought that the initial insult may involve traumatic injury, e.g., from the passage of hard stool. However, in the majority of cases this heals without leading to development of a chronic anal fissure. It is likely that, in those patients developing anal fissure, there is an underlying abnormality of the internal anal sphincter leading to hypertonicity. This spasm exacerbates the relative ischaemia of the anodermal mucosa posteriorly and as a result can lead to the development of a fissure.

What volume of saliva is normally produced per day?

0.5–1.0 litres.

Where is saliva produced?

1. Submandibular glands (70% saliva produced here): opens into oral cavity via Wharton's duct at a small papilla lateral to the frenulum linguae; supplied by the facial nerve.

2. Parotid gland: opens into oral cavity adjacent to the second molar tooth via Stensen's duct; supplied by the glossopharyngeal nerve.

3. Saliva is also produced by the sublingual and minor salivary glands within the oral mucosa.

What are the common approaches to the thoracic cavity?

Median sternotomy

The patient is positioned supine on the operating table. A midline skin incision is made from the jugular notch to the xiphisternum. Using monopolar diathermy this is then extended through the subcutaneous fat, being careful to remain in the midline until the sternum is reached. Blunt dissection with a finger is then used to clear tissues below the xiphisternum and around the top of the manubrium. The interclavicular ligament is divided with diathermy and the xiphisternum is cut with McIndoes scissors. The sternal saw is then used to divide the bone and a retractor is placed to expose the anterior mediastinum.

Posterolateral thoracotomy

The patient is positioned prone or in a lateral position dependent on the structures to be accessed. A long parascapular incision is made, running from a point midway between the medial scapular edge and the thoracic spine and following a curve that runs 2 cm below the inferior scapular angle, to the midpoint of the axilla.

What proportion of traumatic blunt splenic injuries are successfully treated conservatively?

Around 90%.

What diagonistic modalities are useful in the assessment of the patient following blunt abdominal trauma?

Focused assessment for sonography in trauma (FAST) - This includes examination of the peri-splenic region, Morrison's pouch, subxiphoid pericardial view, suprapubic region and examination of pleura for haemothoraces.

Preface

In the face of the changing style of the intercollegiate MRCS examination, ‘older’ revision texts are no longer up to date with the novel exam format. In writing this book we aim to preserve the ‘Socratic’ method of question-and-answer that has previously been so well received amongst candidates. At the same time, we draw on our own personal experiences, of those students we have taught, and of those that have taught us, providing a novel text based on what you really need to know.

By combining a systems-based approach with the related anatomy and physiology, we hope that this book will not only act as a quick reference guide during a night on call, but also improve your overall understanding of each topic, providing that background information that we so greatly crave but often have insufficient time to search for.