INTRODUCTION
The digestive system consists of the digestive tract, a tube extending from the mouth
to the anus.
It is associated with accessory organs, primarily glands,
which secrete fluids into the digestive tract.
The digestive tract is also called the
alimentary tract, or alimentary canal.
The term gastrointestinal tract technically only
refers to the stomach and intestines but is
often used as a synonym for the digestive tract.
LAYERS OF ALIMENTARY CANAL
Serosa or Adventitia
This outermost layer of the digestive tract.
It is a connective tissue layer called either the serosa or the adventitia.
This serosa is called the visceral peritoneum.
It consists of a thin layer of connective tissue and a simple squamous epithelium.
PERITONEUM
It is the largest serous membrane of the body.
It is a closed sac containing a small amount of serous fluid within the abdominal cavity.
Itis richly supplied with blood and lymph vessel and contain many lymph nodes.
It provides a physical barrier to the local spread of infection and prevents other abdominal structures' involvement.
It has two layers
1. The parietal peritoneum -which lines the abdominal wall.
2. The visceral peritoneum- which covers the organs.
Mesentery:
Double folded peritoneum that covers the stomach and intestine deeply.
Greater omentum:
The fold of the peritoneum enclosing the stomach extends beyond the greater
Curvature of stomach
and hangs down in front of the abdominal organ like an apron.
peritoneal cavity:
The two layers of the peritoneum are actually in contact and friction between them.
It is prevented by the presence of serous fluid secreted by peritoneal cells.
MUSCLE LAYER
muscular or muscle layer: which consists of an inner layer of circular smooth muscle outer layer of longitudinal smooth muscle.
myenteric plexus:
nerve plexus, which also consists of axons cell bodies,
It is between these two muscle layers
enteric plexus:
Together, the submucosal and myenteric plexuses constitute the enteric
plexus
The enteric plexus is extremely important in the control of movement
and secretion.
SUBMUCoSA
The submucosa is a thick connective tissue layer
containing nerves, blood vessels, and small glands
submucosal plexus -The plexus of nerve cells in the submucosa.
MUCOSA
The innermost layer, the mucosa, consists of three layers: (1)
The inner mucous epithelium, which is moist stratified squamous epithelium in the mouth, oropharynx, esophagus, and anal canal
(2) A loose connective tissue called the lamina propria; and
(3) An outer thin, smooth muscle layer, the muscular mucosae.
MUCOUS MEMBRANE
This layer consists of stratified squamous epithelium with mucus-secreting
glands.
The mucous membrane consists of columnar epithelial cells.
Muscles Lubricate the wall of the track and protect them from the damaging effects of digestive enzymes.
FUNCTIONS OF THE DIGESTIVE SYSTEM
Ingestion is the introduction of solid or liquid food into the stomach.
Mastication is the process by which food taken into the mouth is chewed by
the teeth.
Propulsion in the digestive tract is the movement of food from one end of
the digestive tract to the other.
Deglutition or swallowing moves food and liquids, called a bolus, from the oral cavity into the esophagus.
Peristalsis is responsible for moving material through most of the digestive tract.
Mixing: mix food with digestive secretions and to help break it into smaller pieces.
Secretion. - It is added to lubricate, liquefy, and digest the food.
Mucus- lubricates the food and the lining of the tract.
Enzymes break large food molecules down into smaller molecules that can be absorbed by the intestinal wall.
CLINICAL SIGNIFICANCE
Peritonitis
Peritonitis is the inflammation of the peritoneal membranes.
This inflammation may result from chemical infection in the digestive
tract, such as when the appendix ruptures.
Peritonitis can be life-threatening.
An accumulation of excess serous fluid in the peritoneal cavity is called
ascites
Ascites may accompany peritonitis, starvation, alcoholism, or liver cancer.
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