THE DIGESTIVE SYSTEM
Organs, structure and function
,INTRODUCTION
• The alimentary/digestive tract provides the body with a continual supply of water,
electrolytes, and nutrients.
• To achieve this requires:
• Movement of food through the alimentary tract;
• Secretion of digestive juices and digestion of the food;
• Absorption of water, various electrolytes, and digestive products;
• Circulation of blood through the gastrointestinal organs to carry away the absorbed substances
• Control of all these functions by local, nervous, and hormonal systems.
• As shown in figure 1, each part is adapted to its specific functions: some to simple
of food, such as the oesophagus; others to temporary storage of food, such as the
and others to digestion and absorption, such as the small intestine.
,FIGURE 1: THE DIGESTIVE TRACT. This
image illustrates the various
components that comprise the digestive
system. All these elements possess a
specific function that allows the
breakdown and uptake of nutrients.
, NERVOUS CONTROL OF GIT
• The gastrointestinal tract has a nervous system all its own called the enteric nervou
system.
• This gastrointestinal nervous system resides in the wall of the gut, beginning in the
oesophagus and extending all the way to the anus.
• The number of neurons in this enteric system is about 100 million, almost exactly e
the number in the entire spinal cord.
• This highly developed enteric nervous system is especially important in controlling
gastrointestinal movements and secretion.
• The enteric nervous system is composed mainly of two plexuses (fig. 2):
• An outer plexus lying between the longitudinal and circular muscle layers, called the m
plexus or Auerbach's plexus,
• An inner plexus, called the submucosal plexus or meissner’s plexus, that lies in the su
• The myenteric plexus increases the tone of the gut and the velocity and intensity o
contractions.
• The submucosal plexus is involved with local conditions and controls local secretion
absorption, and muscle movements.
Organs, structure and function
,INTRODUCTION
• The alimentary/digestive tract provides the body with a continual supply of water,
electrolytes, and nutrients.
• To achieve this requires:
• Movement of food through the alimentary tract;
• Secretion of digestive juices and digestion of the food;
• Absorption of water, various electrolytes, and digestive products;
• Circulation of blood through the gastrointestinal organs to carry away the absorbed substances
• Control of all these functions by local, nervous, and hormonal systems.
• As shown in figure 1, each part is adapted to its specific functions: some to simple
of food, such as the oesophagus; others to temporary storage of food, such as the
and others to digestion and absorption, such as the small intestine.
,FIGURE 1: THE DIGESTIVE TRACT. This
image illustrates the various
components that comprise the digestive
system. All these elements possess a
specific function that allows the
breakdown and uptake of nutrients.
, NERVOUS CONTROL OF GIT
• The gastrointestinal tract has a nervous system all its own called the enteric nervou
system.
• This gastrointestinal nervous system resides in the wall of the gut, beginning in the
oesophagus and extending all the way to the anus.
• The number of neurons in this enteric system is about 100 million, almost exactly e
the number in the entire spinal cord.
• This highly developed enteric nervous system is especially important in controlling
gastrointestinal movements and secretion.
• The enteric nervous system is composed mainly of two plexuses (fig. 2):
• An outer plexus lying between the longitudinal and circular muscle layers, called the m
plexus or Auerbach's plexus,
• An inner plexus, called the submucosal plexus or meissner’s plexus, that lies in the su
• The myenteric plexus increases the tone of the gut and the velocity and intensity o
contractions.
• The submucosal plexus is involved with local conditions and controls local secretion
absorption, and muscle movements.
