Digestive System
Digestion is the mechanical and chemical breakdown of food into
smaller components that are more easily absorbed into a blood
stream, for instance. Digestion is a form of catabolism: a breakdown of large food molecules
to smaller ones.When food enters the mouth, its digestion starts by the action of mastication, a form of mechanical digestion, and the contact of saliva. Saliva, which is secreted by the salivary glands, contains salivary amylase, an enzyme which starts the digestion of starch in the food. After undergoing mastication and starch
digestion, the food will now be in the form of a small, round mass, called a Bolus (digestion). It will then travel down the
esophagus and into the stomach by the action of peristalsis. Gastric juice in the stomach starts protein
digestion. Gastric juice mainly contains hydrochloric acid and pepsin. As these two chemicals may damage the
stomach wall, mucus is secreted by the stomach, providing a slimy layer that acts as a shield against the damaging effects of the chemicals. At the same time protein digestion is occurring, mechanical mixing occurs by peristalsis, which are waves of muscular contractions that move along the stomach wall. This allows the mass of food to
further mix with the digestive enzymes. After some time (typically an hour or
two in humans), the resulting thick liquid is called chyme. When the pyloric sphincter valve opens, chyme enters the
uodenum where it mixes with digestive enzymes from the pancreas, and then passes through the small intestine in which digestion continues. When the chyme is fully digested, it is absorbed into the blood.
smaller components that are more easily absorbed into a blood
stream, for instance. Digestion is a form of catabolism: a breakdown of large food molecules
to smaller ones.When food enters the mouth, its digestion starts by the action of mastication, a form of mechanical digestion, and the contact of saliva. Saliva, which is secreted by the salivary glands, contains salivary amylase, an enzyme which starts the digestion of starch in the food. After undergoing mastication and starch
digestion, the food will now be in the form of a small, round mass, called a Bolus (digestion). It will then travel down the
esophagus and into the stomach by the action of peristalsis. Gastric juice in the stomach starts protein
digestion. Gastric juice mainly contains hydrochloric acid and pepsin. As these two chemicals may damage the
stomach wall, mucus is secreted by the stomach, providing a slimy layer that acts as a shield against the damaging effects of the chemicals. At the same time protein digestion is occurring, mechanical mixing occurs by peristalsis, which are waves of muscular contractions that move along the stomach wall. This allows the mass of food to
further mix with the digestive enzymes. After some time (typically an hour or
two in humans), the resulting thick liquid is called chyme. When the pyloric sphincter valve opens, chyme enters the
uodenum where it mixes with digestive enzymes from the pancreas, and then passes through the small intestine in which digestion continues. When the chyme is fully digested, it is absorbed into the blood.