food digestion

• ingestion - this involves taking in food into the mouth and gastrointestinal tract.
• ingestion also involves salivary action and physical breakdown of food through mastication.
• Initially, the smell of food signals the salivary glands to produce saliva.
• Tasting the food increases the amount of secretion.
• Amylase - is the enzyme in saliva that is responsible for digestion of starch (sugars in plants) and glycogen (sugars in animals).
• Propulsion - is the movement of food down that gastrointestinal tract.
• Swallowing - is a voluntary type of propulsion where tongue pushes the food down to the esophagus.
• Peristalsis - is the involuntary type of propulsion, wherein muscles of the digestive tract involuntarily contract and relax alternately to create rippling movements.
• Mechanical digestion - breaks down food molecules without chemical reactions.
• Mastication - oral cavity
• Churning - stomach
• Segmentation - small intestine
• Chemical digestion - breaks down food molecules by using chemical reactions.
• Gastrin - triggers the stomach to produce pepsinogen, mucus, and hydrochloric acid.
• Most of the digestion takes place in the - small intestine.
• Bile - fat emulsification
• Pancreatic juice - amylases, proteases, and lipases for breakdown of respective substrates
• Absorption - involves transport of the digested food into the bloodstream via intestinal capillaries and lacteals
• Capillaries - glucose and amino acids, vitamins, minerals
• Lacteals - fatty acids and glycerol
• Stomach - water, minerals and alcohol
• Large intestine - most of the water and vitamins
• The small intestine - also absorbs some of the water, minerals, and alcohol.
• The large intestine - absorbs most of the water and some vitamins.
• Assimilation - involves building up of complex substances after absorption. This process is the opposite of absorption.
• Fatty acids - are used to form fats.
• Amino acids - are used to form proteins.
• Monosaccharides are used to form polysaccharides (glycogen for animals).
• Essential compounds - such as hormones and enzymes are also synthesized.
• Excretion - is the elimination of the undigested food.
• Feces - indigestible materials like cellulosic fiber, small amounts of water, mucus, and bacteria
• Peristalsis and mass movements in the large intestine move the feces into the rectum.
• Mass movements are slow and long contractions within the large areas of the large intestine.
• Digestive system events are ingestion, propulsion, digestion, absorption, assimilation, and excretion
• Digestion, or the breakdown of food into absorbable units can either be mechanical or chemical