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The Digestive System

Human Nutrition and Absorption

What is nutrition? Nutrition is the process by which an organism obtains and uses its food.
What are the different nutrition classifications of organisms? Plants make their own food and are called autotrophs. Organisms that eat plants are known as herbivores. Organisms that eat animals are known as carnivores. Animals that eat plants and animals are known as omnivores.
What is the dental formula of an organism? The dental formula tells us how many teeth in the upper and lower jaw in one half of the mouth of an organism.
What is the human dental formula? i=2/2 c=1/1 p=2/2 m=3/3
What are the five stages of digestion in human nutrition? 1: Ingestion 2: Digestion 3: Absorption 4: Assimilation 5: Egestion
What type of digestion occurs in the mouth? Physical digestion: the teeth chew the food and break it into smaller pieces. Chemical digestion: salivary amylase breaks down starch into maltose in the mouth.
What are the 4 types of tooth in our mouths. What is the function of each type? Incisors are used to cut and slice teeth. Canines are used to rip and tear food. Premolars and molars are used to crush and grind food.
How does food get from the mouth to the stomach? A bolus is formed in the mouth. It is swallowed and passes into the oesophagus. Muscles around the oesophagus contract and force the food down (peristalsis). At the end of the oesophagus the cardiac sphincter opens and the food enters the stomach.
What occurs in the stomach? The stomach holds approx 1L of liquid (chyme). The stomach churns the food (physical) and mixes it with HCl and the enzyme pepsin (chemical). The HCl kills bacteria and the pepsin converts proteins to polypeptides. Mucus prevents self digestion by HCL
What are the two parts of the small intestine known as? The first part of the small intestine is 30cm long and is called the duodenum. Chemical digestion occurs here. The next, roughly 8m of small intestine is known as the ileum, chemical digestion ends here and absorption occurs here.
What digestion takes place in the duodenum? Enzymes from the pancreas and bile from the liver mix with the biomolecules in the duodenum. The enzymes include Trypin, Amylase and Lipase. The bile contain Sodium Bicarbonate which neutralises the acid from the stomach.
What are the functions of the pancreas? The pancreas produces three enzymes. 1: Trypsin which converts proteins to polypeptides. 2: Amylase which converts starch to maltose. 3: Lipase which converts fats to fatty acids to glycerol. It also produces insulin which controls blood sugar.
What is the function of bile? Bile is made by the liver and stored in the gall bladder. It is an emulsifying agent that allows water and oil to mix, increasing the surface area for lipase to work on. It is made up of bile salts, bile pigments and the base sodium bicarbonate.
What are the functions of the liver? 1:Storage of excess glucose as glycogen and iron from recycled red blood cells. 2:Deamination, the breakdown of excess amino acids.4:Detoxification, the break down of harmful chemicals ingested. 5: Body heat is produced by the livers chemical reactions
What chemical digestion occurs in the ileum? The ileum is the longest part of the intestines. Chemical digestion occurs here through the enzymes maltase (maltose to glucose) lipase (fats to fatty acids and glycerol) and pepsidase (polypeptides to amino acids)
How is the ileum well suited for the absorption of food? Its entire surface is covered in finger like projections called villi which are in turn covered in micro-villi. It is one cell thick to allow for rapid absorption and it has an excellent blood supply.
What absorption occurs in the ileum? Carbohydrates, proteins, minerals and water soluble vitamins are absorbed into the capillaries in the villus. Fatty acids, glycerol and fat soluble vitamins are absorbed into the lacteals of the villi.
What happens to the material absorbed into the lacteal? The material is coated in protein by the lymph system and is returned to the blood stream at the sub clavian vein.
What is a portal system? What blood vessel connects the liver and the intestines? A portal system connects two organ systems and by passes the heart. The hepatic portal system.
What is the advantage of the hepatic portal system? This allows the blood to be screened by the liver for any toxic material and allows for detoxification before it is sent to the heart and then all around the body.
What are the 5 parts of the large intestine? What is the large intestines major function? 1: The caecum. 2: The Appendix 3: The Colon 4: The Rectum. 5 The Anus. The function of the large intestine (colon) is to absorb water from the undigested food, forming faeces.
What happens during egestion? Faeces is stored in the rectum and during egestion it is passed out of the anal sphincter and egested through the anus.
Created by: cbsbiology