The appendix is sometimes referred to as the 'abdominal tonsil' because it is composed largely of lymphoid tissue and is very susceptible to infection. It varies greatly in size, the average length being 75 mm. Normally it is a hollow tube lined with mucousmembrane, with a muscle wall similar to that of the caecum with which it communicates. Its tip may hang down over the brim of the pelvis to make contact with the bladder, the rectum, or in the female with the ovary, uterine tube or uterus. It may on the other hand, turn upwards behind the caecum pointing out towards the groin-the retro-caecal position. It may lie on the front of the caecum immediately under the anterior abdominal wall. Research Appendix
The autonomic nervous system is responsible for the self-controlling aspects of the body's nervous network, and is under the control of the cerebral cortex, the hypothalmus, and the medulla oblongata. Working in tandem with the central nervous system, the autonomic nervous system features two subsystems which regulate body functions such as involuntary smooth muscle movement and heart rate. These two subsystems are called the sympathetic and parasympathetic nervous system, and their functions operate in opposition to one another, delicately balancing the bodily functions which they control. The sympathetic nervous causes fight or flight responses in moments of stress or stimulus, such as increased heart rate, saliva flow, and perspiration. The parasympathetic system counterbalances these effects by slowing the heart rate, dilating blood vessels, and relaxing involuntary smooth muscle fibres. Viewed individually, the sympathetic nervous system, also referred to as the thoracolumbar system, features a series of nerves which branch out of the spinal cord between the first thoracic vertebra and the second lumbar vertebra. These nerve fibres join into a long trunk of fibres, called the sympathetic trunk, on each side of the spinal cord. Along the sympathetic trunk are enlarged clusters of nerve fibres, called ganglia.
From these ganglia, a number of nerve fibres extend throughout the body's tissues. Many of these nerves create additional ganglia, such as the celiac ganglia and the mesenteric ganglia. The sympathetic nerves are responsible for contracting involuntary smooth muscle fibres, viscera, and blood vessels, speeding up the heart rate, and dilating the bronchial tubes in moments of stress. The parasympathetic nervous system, also referred to as the craniosacral system, features ganglia in the midbrain, in the medulla oblongata, and in the sacral region. The first two, the cranial ganglia of the parasympathetic system, give pass impulses to the facial, oculomotor, glossopharyngeal, and vagus nerves. The sacral group of parasympathetic nerves originate at the second, third, and fourth vertebrae and extend nerves to the bladder, the distalcolon, the rectum, and the genitals. The nerves of the parasympathetic nervous system are responsible for conserving and restoring energy in the body following a sympathetic response to stress. Research Autonomic Nervous System
The colon is the central part of the large intestine. Extending from the cecum to the rectum, it is descriptively subdivided into four parts: the ascending, the transverse, the descending, and the sigmoid colon. The ascending colon extends upward from the cecum to lead into the transverse portion. The transverse extends across the abdominal cavity from the end of the ascending part to lead into the descending section of the colon. The descending colon extends from the end of the transverse colon to the sigmoid colon. The sigmoid colon connects the end of the descending colon to the rectum. The rectal and sigmoid sections are often referred to as the rectosigmoid. Research Colon
Colostomy is the operation of opening into the colon, or lower portion of the intestine. This procedure is one of the most important in abdominal surgery. It is sometimes necessary as a life- saving measure. It may be temporary or permanent as an artificial anus in the radical treatment of rectal cancer. Because of its appearance, its inconvenience and the very thought of an artificial opening in the abdominal wall a great deal of care is necessary to allay the anxieties of patients and their relatives when colostomy is necessary.
In some cases of acute intestinal obstruction the surgeon explores the abdomen and finds perhaps a large mass in the region of the pelvic colon or rectum that cannot be removed. An emergency colostomy is then performed in the transverse colon with the immediate purpose of saving life and with the further objective of providing temporary drainage should the growth be removable at a later date. In some such cases, when at first sight the primary cause of the obstruction seems beyond any possibility of surgical removal, after several weeks of colostomy drainage the infection subsides and the affected portion of bowel may then be removed. Colostomy may be necessary as a preliminary to other operations involving removal of the large bowel. Such an occasion arises if diverticulitis has produced vesico-colic fistula (between the colon and bladder). In some cases of severe incontinence due to abnormality or injury to the anus, a left iliac colostomy enables the patient to be free of the terrible inconvenience of perpetual soiling in the perineum. Injuries or abnormalities of the spinal cord produce paralysis of the anal sphincter mechanism and sometimes colostomy is essential. Congenital absence of the rectum or anus requires an emergency colostomy within a day or so of birth.
There are two main forms of colostomy. First is the loop colostomy which has two limbs. The opening is at the apex of the loop and the bowel has not been divided completely across. A variation of the loop colostomy is the double- barrel form in which the two limbs of the loop are separated by a piece of skinrafter complete division. This is also described as a defunctioning colostomy as it prevents the spill of faeces from the proximal to the distalloop. A second variety is the spur colostomy where a spur is formed by suturing the two ends together for several centimeters inside the abdomen. This is of particular value if the colostomy is temporary as the spur can be destroyed by a crushing clamp without risk of peritonitis or perforation since the limbs have become sealed together. When the spur breaks down, the artificial opening on the surface shrinks and sinks back below the skin level. The aim is that this should close spontaneously without further operation. The third type is the terminal colostomy in which the distal portion of bowel is removed completely or in the case of excision of rectum the lower end is closed to form a blind end. In grave emergencies the simplest form of colostomy is performed in which a loop of colon is brought out through the abdominal wall, where it is held by the insertion of a glassrod passed through a small hole in the mesentery. The ends of the glassrod are connected by a loop of rubber tubing which forms a 'bucket handle' . The abdominal wall is closed around the protrusion of the colostomy. Exteriorisation is another way of performing a colostomy. If a growth is present in a part of the bowel which can be brought readily through the abdominal wall (e.g. transverse or pelvic colon) the affected loop containing the growth is left outside and the peritoneum, muscles and skin are closed around the base of the loop where the two limbs converge. The loop of colon containing the growth is then removed, leaving two open ends of el which can later be joined by crushing the spur between them. This operation avoids the handling of growth or unprepared bowel while the peritoneal cavity is open and so diminishes the risk of peritonitis. A formal operation for closure is required if a spur has not been made.
At the end of the operation a small incision is usually made in the apex of the loop to allow the immediate discharge of gas and faecal material which is collected as cleanly as possible before the patient leaves the theatre. A dressing of petroleum jelly gauze or tullegras is applied on the exposed bowel. The skin incision may be sealed with Whitehead's varnish and a pad of cellulosetissue and wool is bandaged lightly over the opening. For fear of contaminating the abdominal wound before the peritoneal cavity has become sealed, the former practice was to leave the colostomy unopened for 48 hours. The initial opening may be enlarged by the surgeon two or three days after the colostomy has been raised. The bowel is usually divided (without anaesthetic) by an electric cautery which seals the blood vessels and prevents bleeding from the very vascular mucousmembrane and muscle wall of the bowel. A method of draining the colostomy is by the use of Paul's tube. This is an angled wide glass tube which is inserted through a hole in the colostomy loop. It is tied in position in the same way as the caecostomy catheter and connected to a bedside jar with wide, thin, latex tubing. Research Colostomy
The digestive system is responsible for processing food, breaking it down into usable proteins, carbohydrates, minerals, fats, and other substances, and introducing these into the bloodstream so that they can be used by the body. The digestive, or alimentary, tract begins at the mouth, where the teeth and tongue begin the breakdown of food, aided by saliva secreted by the salivary glands. The chewed food, combined with saliva, is swallowed, carrying it in peristaltic waves down the esophagus to the stomach. In the stomach, the food combines with hydrochloric acid which further assists in breaking it down. When the food is thoroughly digested, the fluid remaining, called chyme, is passed through the pylorus sphincter to the small intestine and large intestines. Within the long, convoluted intestinal canals, the nutrients are absorbed from the chyme into the bloodstream, leaving the unusable residue. This residue passes through the colon (where most of the water is absorbed into the bloodstream) and into the rectum where it is stored
prior to excretion. This solid waste, called faeces, is compacted together and, upon excretion, passes through the analcanal and the anus. Along the way through the digestive tract, the pancreas, spleen, liver, and gall bladder secrete enzymes which aid in the digestive process. Research Digestive System
Endoscopy is the examination of internal parts of the body using special instruments known as endoscopes. The simplest method of instrumental examination is that employed for the analcanal and rectum. A 'speculum' (proctoscope) which is in fact a simple tube with a handle, is introduced through the analcanal and the surgeon examines the rectal wall through the tube. To facilitate the introduction of the instrument, there is a shaped conical stopper which is known as the 'obturator.' This same principle of a shaped introducer is used on many instruments which have an open tubular end. Sigmoidoscopy is the examination of the upper regions of the rectum and the sigmoid or pelvic colon with a longer tubular speculum. Because the folds of mucousmembrane fall against the end of the instrument and obstruct the view, air inflation is used for the introduction of the sigmoidoscope so that the lumen of the bowel is distended. The surgeon inserts the instrument under direct vision, inspecting the wall of the bowel as far as 25 cm. from the anus.
The oesophagoscope is a similar instrument passed down the oesophagus through the mouth, thus enabling the surgeon to inspect the whole length of the gullet. The inside of the stomach is examined by the gastroscope, using air inflation. Through a very small incision in the abdominal wall the surgeon may introduce another viewing instrument, the peritoneoscope, and with this he may inspect the inside of the peritoneal cavity and obtain infonnation to enable him to reach a decision without open operation. In order to separate the coils of intestine from one another and allow the satisfactory inspection of the viscera, the peritoneal cavity is inflated with air through a separate cannula. Endoscopic instruments, except for the simpler forms of proctoscope, carry their own miniature lamps which draw electric current either from a battery or the mains through a transformer to reduce the voltage. The bladder and urethra are inspected with the cytoscope and urethroscope. The urinary tract is distended with water instead of air for the inspection, but air inflation is sometimes used for the lower part of the urethra. Various forms of speculum are used for the vagina and these are usually illuminated by direct light, although some forms carry a lamp of their own. Operations for the removal of tissue for microscopic examination (biopsy) are performed through some of the tubular instruments, and for this purpose there are special long forceps and diathermy electrodes. Examinations carried out with endoscopic instruments may be made with local or general anaesthesia and in the case of the rectum and colon, without anaesthesia. Research Endoscopy
The intestines are the convoluted membranous tube which extends from the stomach to the anus and which receives the ingested food from the stomach, mixes it with bile, pancreatic juice and intestinal secretions, gives origin to the chyle and delivers the indigestible products from the system. The intestines are divided into the small and large intestine (colon). The small intestine is further divided into three parts: the duodenum, the jejunum and the ileum. The large intestine is divided into the ascending colon, the tansverse colon, the descending colon and the rectum that terminates at the anus. Research Intestines
The large intestine is a broad, corrugated tube which accepts the by-products of digestion from the small intestine and passes it along to be excreted, continuing to process the material on the way. Any unabsorbed food materials are stored in the large intestine until the body can partially reabsorb water from it, then passing the remains along to the anus for elimination. The overabsorption of water from the waste material may lead to hard, relatively dry faeces which can become impacted, making elimination difficult. This condition is known as constipation. If not enough liquid is reabsorbed, as often caused by some viral infections or malnutrition, the large intestine passes too much fluid to the anus, making control of elimination difficult. This condition, and the fluid (which is often painful to the anal tissues) is known as diarrhea. The
large intestine is divided into eight sections: the cecum, the appendix, the ascending colon, the transverse colon, the descending colon, the sigmoid colon, the rectum, and the anus. Research Large Intestine
The inferior mesenteric vein and the superior mesenteric vein run alongside their corresponding arteries. The inferior mesenteric vein returns blood from the rectum and colon. Both veins merges with the splenic vein to form the portalvein. Research Mesenteric Vein
The Probert Encyclopaedia was designed, edited and programed by
Matt and Leela Probert
Abbreviations
Research Appendix
