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Digestive system - Coggle Diagram
Digestive system
Organs
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Salivary glands
Three pairs of glands produce saliva, which dissolves food.
Saliva contains mucus that lubricates the mouth and food and holds food in a lump of swallowing. It also contains salivary amylase, which begins starch digestion.
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Stomach
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Chemical digestion by pepsin, which begins protein digestion.
Liver
Produces bile, which is stored and concentrated in the gall bladder.
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Gall bladder
Stores bile and releases it into the small intestine, where the bile emulsifies lipids.
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Pancreas
Produces pancreatic juice containing enzymes for digesting proteins, lipids and nucleic acids.
Colon
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Longest part of large intestine. Absorbs water, minerals and vitamins.
Small intestine
Its lining secretes intestinal juice, which contains many enzymes.
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Anus
Opening surrounded by the anal sphincter, a muscle that can be voluntarily controlled.
Large intestine
Movement of material through it is slow. (18-24 hours to pass through). During this time, water is absorbed so the contents become solid.
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Some bacteria produce vitamins, which are then absorbed through the walls into the blood. (mineral nutrients are absorbed)
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Faeces contain water, undigested food material, bacteria, bile pigments and the remains of cells that have broken away from the internal lining.
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Rectum
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Semi-solid material left in the colon after water absorption is pushed into the rectum by peristalsis.
As the walls of the rectum stretch, they trigger a response known as defaection.
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Stomach
The stomach lining is specialized for secretion of gastric juice. Gastric juice contains hydrochloric acid, mucus and digestive enzymes.
- Mechanical digestion in the stomach occurs by waves of muscular contraction that move along the stomach wall.
- The stomach can contract in a variety of ways to churn the food and mix it with the gastric juice. The food is converted to a thick, soupy liquid called chyme.
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- Chemical digestion occurs through enzymes in the gastric juice.
- The enzyme pepsin (or gastric protease) breaks the bonds between certain amino acids so that the long chains of amino acids that make up a protein molecules are broken into shorter chains called polypeptides.
- Pepsin works in very acidic solutions.
- The hydrochloric acid in gastric juice allows pepsin to act.
- It also kills many bacteria that enter the stomach with the food.
- A thickening of the circular muscle, called the pyloric sphincter, regulates flow of material form the stomach to the duodenum.
- After 2-8 hours, the stomach contents are pushed into the duodenum.
- The mucosa is specialized for the secretion of gastric juice.
- Gastric juice is secreted by gatsric galnds, which are located gastric pits.
The small intestine
- It receives material pushed through the pyloric sphincter from the stomach.
- The first part of the intestine is called Duodenum.
- Digestion continues in the small intestine under the influence of intestinal juice secreted by glands in the lining, pancreatic juice secreted by the pancreas, and bile secreted by the liver (store in the gall bladder).
- Pancreatic juice enters the duodenum and helps to neutralize the acid that has come with the material form the stomach.
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Liver produces Bile (contains no digestive enzymes but has bile salts, which break fats into droplets; mechanical digestion).
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- The products of digestion (vitamins, minerals and water) are absorbed through the wall of the small intestine into the blood.
- Nutrients are absorbed through the internal surface area of the small intestine, efficient absorption requires a large surface area.
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Villus
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Inside it there is a lymph capillary called a lacteal, which is surrounded by a network of blood capillaries.
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Substances that are absorbed into the blood capillaries are carried by the hepatic portal vein to the liver.
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Oesophagus
The wall of the oesophagus has a double layer of muscle made up of circular muscle with muscle fibres arranged in a circle around the alimentary canal, and Longitudinal muscle, with fibres arranged along the length of the canal
As the lump of food enters the pharynx and oesophagus, the circular muscle behind it contracts to form a constriction.
By contraction of successive bands of circular muscle the constriction moves in a wave along the oesophagus, pushing the food in front of it.
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The oesophagus passes through the diaphragm, a sheet of muscle that separates the chest cavity from the abdominal cavity.
Teeth
Mechanical digestion
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As the food is chewed it is mixed with saliva, a fluid that is secreted into the mouth cavity by three pairs of salivary glands.
Types of teeth
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Molars (6)
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The cusps of the teeth of one jaw fit into depressions on the surface of teeth on the other jaw, (making premolars and molars ideal for crushing and grinding food.
Chemical digestion
It contains a mucus and salivary amylase,which begins the chemical digestion of starch, breaking down the large starch molecules into smaller molecules.
Tongue
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To swallow the tongue moves upwards and backward, pushing the food into the back of the mouth, the pharynx.
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Digestion
The process in which proteins, carbohydrates and fat molecules are broken down to products small enough to be absorbed into the blood and into the cells.
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The digestive system extracts nutrients from the food we eat and absorbs them into the body for the use by cells.
