Histology of Esophagus

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Histology of Esophagus Powered By Docstoc
					         Course Outline
Gross outline of Esophagus, general
 histological features of
 gastrointestinal, tract and specific
 histological features of Esophagus
       Learning Objectives
Review the gross features of
Describe the general histological
 features of Gastrointestinal tract
Discuss the specific histological
 features of Esophagus
Alimentary Canal
   begins at the oral
   cavity and
   terminates at anal
Gastrointestinal Tract
   begins at the
   Esophagus and
   terminates at anal
The esophagus consists of a
  muscular tube through            Anatomy
  which food passes from the
  pharynx to the stomach. In
  humans the esophagus is
  continuous with the
  laryngeal part of the
  pharynx at the level of the
  C6 vertebra. The esophagus
  passes through a hole in the
  diaphragm at the level of
  the tenth thoracic vertebrae
  (T10). It is usually about 25–
  30 cm long and connects
  the mouth to the stomach.
        Coats / Layers of Intestine
In general the
  intestine consists
  of four layers
  these are in to
  outside are:
Muscularis Externa
Seorsa or Adventitia
The mucosa is the
  innermost layer of the        Mucosa
  gastrointestinal tract that
  is surrounding the
  lumen, or space within
  the tube. This layer
  comes in direct contact
  with food (or bolus), and
  is responsible for
  absorption and
  secretion, important
  processes in digestion.
The mucosa can be divided
Lamina propria
Muscularis mucosae
Mucosa in the small
  intestine thrown into
  folds called as Villi.
  The number of villi
  decreasing as we are
  moving from
  duodenum to ileum.
On the free surface of
  villi lined with
  epithelium which is
  simple columnar
  epithelium. Free
  surface of epithelium
  shows microvilli, these
  are finger like
  projection of
  plasmalemma of
These microvilli are
  very regularly
  arranged and on
  examination they
  form continuous
  border called as
  striated border.
  Villi and microvilli
  increased the
  surface area of
           Mucosa: Lamina Propria
Lamina propria
  consists of
  connective tissue,
  these are fiber
  (Collagen, Elastic &
  reticular), cells
  histiocytes, plasma
  cell and wandering
  cells of connective
            Mucosa: Lamina Propria
Lamina propria also extends
  into the villi, supports the
  villi. The lamina propria is
  also typically rich in blood
  and lymphatic capillaries
  necessary to support the
  secretory and absorptive
  functions of the mucosa.
Exocrine glands are present
  in lamina propria of almost
  entire length of GIT
       Mucosa: Muscularis Mucosae
The muscularis mucosae
  consists of several
  layers of smooth
  muscle fibers, those in
  the deeper layers
  oriented parallel to the
  luminal surface. The
  more superficial fibers
  are oriented at right
  angles to the surface
  and in the small
  intestine the fibers
  extend up into the villi.
       Mucosa: Muscularis Mucosae
The activity of the
  muscularis mucosae
  keeps the mucosal surface
  and glands in a constant
  state of gentle agitation,
  which expels secretions
  from the deep glandular
  crypts, prevents clogging
  and enhances contact
  between epithelium and
  luminal contents for
The submucosa
  consists of             Submucosa
  collagenous and
  adipose supporting
  tissue that binds the
  mucosa to the main
  bulk of the muscular
  wall. The submucosa
  contains the larger
  blood vessels and
  lymphatics as well as
  the nerves supplying
  the mucosa.
Parasympathetic ganglia are
  scattered throughout the     submucosa
  submucosa, forming the
  submucosal (Meissner's)
  plexus from which
  postganglionic fibers
  supply the muscularis
Submucosa also contains
  the exocrine glands, there
  are only two place in GIT,
  where the submucosa
  contains the glands,
  Esophagus and
The muscularis externa
  consists of an inner
  circular layer and a
                            Muscularis externa
  longitudinal outer
  muscular layer. The
  circular muscle layer
  prevents food from
  traveling backward and
  the longitudinal layer
  shortens the tract. The
  contractions of these
  layers is called
  peristalsis and propels
  the bolus, or balled-up
  food, through the GI
              Muscularis externa
Between the two
  muscle layers are
  the myenteric or
  activity enhances
  peristalsis while
  activity slows gut
                Serosa / Adventitia
The adventitia consists
  of several layers of
When the adventitia is
  facing the mesentery
  or peritoneal fold, the
  adventitia is covered
  by a mesothelium
  supported by a thin
  connective tissue
  layer, together
  forming a serosa, or
  serous membrane.
             Division of Esophagus
For the purpose of histological
  descriptions, the esophagus
  is subdivided into three
Upper one third (entirely
  skeletal muscle in the
  muscularis externa), and
  under voluntary control
Middle one third (mixed
  smooth and skeletal muscle)
Lower one third entirely
  smooth muscle and under
  involuntary control
             Surface Epithelium
The esophageal
  epithelium is the
  stratified squamous
  type because this
  tube is under the
  constant wear & tear
Surface epithelium is
  supported by a
  connective tissue
  lamina propria.
The lamina propria contains
  isolated lymphoid nodules
  and scattered leukocytes.
  Small mucous glands may
  be found scattered in the
  lamina propria of the
  upper and lower
  esophagus. Small mucous
  glands which are present in
  lower part of esophagus
  called as cardiac glands
  these secret serous fluid.
A rather thick layer of
  longitudinally arranged
  smooth muscle fibers form
  the muscularis mucosae.
The connective tissue of the
  submucosa consists of
  mostly collagenous fibers
  with some elastic fibers
  and varying amounts of fat
  as well as submucosal
  sero-mucous glands, these
  secret mucus.
In the upper esophagus, the
   muscularis externa consists       Esophagus
   of both inner and outer
   layers of skeletal muscle only.
In the middle esophagus, the
   muscularis externa contains a
   mixture of skeletal and
   smooth muscle,
 whereas in the lower
   esophagus only smooth
   muscle is found.
 Present in all regions of the
   esophagus (upper, mid, and
   lower) is the myenteric
   (Auerbach’s) plexus between
   the two layers of the
   muscularis externa.
For most of its extent, the
  esophagus is
  retroperitoneal, so its
  outermost layer consists of
  a connective tissue
  adventitia which merges
  with the adjacent
  connective tissue
  associated with nearby
  structures (such as the
  trachea. Below the
  diaphragm, however, the
  esophagus is suspended
  within abdominal cavity
  and is therefore covered by
  a connective tissue serosa.

Description: This presentation explains histology of Esophagus