Anatomy and physiology

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vermiform appendix

• Anatomy and physiology

b I n u r a j
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• In human anatomy, the
• Appendix
• or
• vermiform appendix
• also cecal (or caecal) appendix also vermix)
• is a blind ended tube connected to the cecum (or
  caecum), from which it develops embryologically.
  The cecum is a pouch-like structure of the colon.
  The appendix is near the junction of the small
  intestine and the large intestine.
• The term "vermiform" comes from Latin and means
  "worm-like in appearance".

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• History
• The appendix was probably first noted as early as
  the Egyptian civilization (3000 BC).
• Aristotle and Galen did not identify the appendix
  because they both dissected lower animals, which
  do not have appendices. Celsus, however, probably
  discovered the appendix because he was allowed to
  dissect criminals executed by Caesar.
• Leonardo da Vinci first depicted the appendix in
  anatomic drawings in 1492 . In 1521, Jacopo
  Beregari da Capri, a professor of anatomy in
  Bologna, identified the appendix as an anatomic
  structure. Phillipe Verheyen coined the term
  appendix vermiformis in 1710.

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• ANATOMY
• Embryologically, the appendix is a continuation
  of the cecum and is first delineated during the
  fifth month of gestation. The appendix does not
  elongate as rapidly as the rest of the colon,
  thus forming a wormlike structure.
• The appendix averages 10 cm in length but can
  range from 2-20 cm. The wall of the appendix
  consists of 2 layers of muscle, an inner circular
  and outer longitudinal.
• Few submucosal lymphoid follicles are noted at
  birth. These follicles enlarge, peak from 12-20
  years, and then decrease. This correlates with
  the incidence of appendicitis.

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• Blood supply - Apendicular artery, a branch of
  the ileocolic artery. An accessory appendicular
  artery can branch from the posterior cecal
  artery. This artery can lead to significant
  intraoperative and postoperative hemorrhage and
  should be searched for carefully and ligated once
  the main appendicular artery is controlled.
• The base is at a constant location, whereas the
  position of the tip of the appendix varies. In
  65 of patients, the tip is located in a
  retrocecal position in 30, it is located at the
  brim or in the true pelvis and, in 5, it is
  extraperitoneal, situated behind the cecum,
  ascending colon, or distal ileum.

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• Functions
• Embryological
• Physiological
• Microbiological (Bacteriological)
• Biochemical
• Immunological
• 1. Embryological
• During the fifth foetal week it is the appendix
  which develops from a bud at the junction of the
  small and large bowel and undergoes rapid growth
  into a pouch. In the sixth week there is a
  transient nubbin surmounting the pouch indicative
  of being involved in the rapid development of the
  pouch which is very strategically placed near the
  apex of the highly significant mid-gut loop. The
  embryonic appendix has finger-like projections
  (villi) on its inside surface

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• 2. Physiological
• The goblet cells lining the appendix and adjacent
  caecum and colon secrete a special type of mucus
  which can be regarded as an antibacterial paint
  controlling the organisms which develop in the
  bowel in the region. The paint contains a high
  concentration of IgA type immunoglobulins,
  secretory antibodies produced for mucosal or
  surface immunity and part of the bowel-blood
  barrier .
• 3. Bacteriological
• Through the cells within and overlying the
  lymphoid follicles and their production of
  secretory and humoral antibodies the appendix
  would be involved in the control of which
  essential bacteria come to reside in the caecum
  and colon in neonatal life. As well it would be
  involved in the development of systemic tolerance
  to certain antigenic agents within the alimentary
  tract whether they are derived from bacteria,
  foodstuffs or even the bodys own proteolytic
  enzymes.

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• 4. Biochemical
• One in three hundred or so appendectomy specimens
  contains a carcinoid tumour composed of a highly
  specialised type of cell rich in vaso-active
  peptides such as serotonin. The exact function of
  such agents in the entire bowel is still being
  elucidated, but the fact that the majority of
  such tumours occur within the appendix is
  indicative that the appendix could well be
  involved in some way with such substances.
• 5. Immunological
• This is the area where the appendix would seem to
  have its predominant functions due to its content
  of lymphoid follicles, which are highly
  specialised structures. Although it was thought
  the appendix itself could be the site for
  B-lymphocyte induction, the latest opinions
  favour this programming being more centralised in
  the bone marrow. The appendix may still have a
  role in this highly significant function, but not
  alone, and its lymphoid tissue is known for
  certain to be involved in antibody production .
  These antibodies are of two types
• IgA type immunoglobulins for secretory or mucosal
  surface immunity, and
• IgM and IgG immunoglobulins for humoral or
  bloodstream immunity

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• Latest Interpretation Maintaining gut flora
• Although it was long accepted that the immune
  tissue, called gut associated lymphoid tissue,
  surrounding the appendix and elsewhere in the gut
  carries out a number of important functions,
  explanations were lacking for the distinctive
  shape of the appendix and its apparent lack of
  importance as judged by an absence of
  side-effects following appendectomy. William
  Parker, Randy Bollinger, and colleagues at Duke
  University proposed that the appendix serves as a
  safe haven for useful bacteria when illness
  flushes those bacteria from the rest of the
  intestines. This proposal is based on a new
  understanding of how the immune system supports
  the growth of beneficial intestinal bacteria.
  Such a function is expected to be useful in a
  culture lacking modern sanitation and healthcare
  practice, where diarrhea may be prevalent.
  Current epidemiological data show that diarrhea
  is one of the leading causes of death in
  developing countries, indicating that a role of
  the appendix as an aid in recovering beneficial
  bacteria following diarrhea may be extremely
  important in the absence of modern health and
  sanitation practices.

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• Diseases
• The most common diseases of the appendix (in
  humans) are appendicitis and carcinoid tumors.
  Appendix cancer accounts for about 1 in 200 of
  all gastrointestinal malignancies. Adenomas also
  (rarely) present.
• Etiology
• Appendicitis results from obstruction of the
  lumen of the appendix. Obstruction may be from
  lymphoid hyperplasia (60), fecalith or fecal
  stasis (35), foreign body (4), and tumors (1)
  (Liu, 1997).
• Appendicitis (or epityphlitis) is a condition
  characterized by inflammation of the appendix.
  Virtually all cases of appendicitis require
  removal of the inflamed appendix, either by
  laparotomy or laparoscopy. Untreated, the
  appendix may rupture, leading to peritonitis,
  then shock, and, if continued untreated, death.
  Pain often begins in the center of the abdomen
  where the lining of the stomach is irritated then
  moves lower right as the condition develops it
  is important to note that this makes diagnoses
  difficult in the early stages because an MRI or
  CT scan must be used to detect it. Appendicitis
  presents as pain in the right lower quadrant with
  rebound tenderness (pain upon removal of pressure
  rather than application of pressure). In
  particular, it presents at McBurney's point, 1/3
  of the way along a line drawn from the Anterior
  Superior Iliac Spine to the Umbilicus. Typically,
  point (skin) pain is not present until the
  parietal peritoneum is inflamed as well. Fever
  and immune system response are also
  characteristic of appendicitis.

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Appendix Cancer
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• The surgical removal of the vermiform appendix is
  called an appendicectomy (or appendectomy). This
  procedure is normally performed as an emergency
  procedure, when the patient is suffering from
  acute appendicitis. In the absence of surgical
  facilities, intravenous antibiotics are used to
  delay or avoid the onset of sepsis it is now
  recognized that many cases will resolve when
  treated non-operatively. In some cases the
  appendicitis resolves completely more often, an
  inflammatory mass forms around the appendix. This
  is a relative contraindication to surgery.
• Use as efferent urinary conduit
• The appendix is used for the construction of an
  efferent urinary conduit, in an operation known
  as the Mitrofanoff procedure, in people with a
  neurogenic bladder.

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• Imaging Studies
• Plain abdominal radiographs
• Abdominal/pelvic ultrasound
• Contrast-enhanced CT scans
• Tc-labeled WBC scan
• Barium contrast studies