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Human Nutrition
The Digestive System
| Question | Answer |
|---|---|
| Where does chemical digestion take place? | the mouth, the stomach, the duodenum in the SI |
| Where does mechanical digestion take place? | the mouth, the stomach |
| What are the four stages of the digestive system? | Ingestion, digestion, absorbtion, egestion |
| Explain the four stages of the digestive system | Ingestion- eating Digestion-breaking down of food (mechanical and chemical) Absorbtion-small intestine absorbing nutrients into bloodstream Egestion-removal of undigested material |
| Why does food need to be digested? | food needs to be soluable so it can be absorbed into the bloodstream and transported around the body |
| What is the formula for teeth? | 2(I 2/2 C 1/1 PM 2/2 M 3/3) |
| What are the four types of teeth? | Incisor, Canine, Premolar, Molar |
| What is chemical digestion? | Enzymes |
| What enzyme helps digest food in the mouth and where does it come from? | Amylase- the salivery gland |
| What is digestion? | The physical and chemical breakdown of food |
| What is the function of bile? | Emulsify lipids- doesn't breakdown the fat into its smallest form, but chops it up into smaller pieces to increase the surface area for lipase |
| What is saliva made of? | water, mucous, lysozyme and amylase |
| Explain how digestion works in the mouth | 1.Mechanical digestion takes place by the crushing and grinding of teeth 2.Chemical digestion takes place by the enzyme amylase in the saliva (breaks down starch into maltose) 3.Food is pushed towards the pharynx which connects mouth to the oesophagus |
| What ensures that food doesn't travel down the trachea instead of the oesophagus? | A flap called the epiglottis closes over the trachea while swallowing |
| How does food travel through the oesophagus? | Involuntary muscular contractions called peristalsis |
| Name two functions of peristalsis in digestion | Helps break food down mechanically and forces food into the small intestine, large intestine and rectum |
| What is dietary fibre (roughage) made of? | Cellulose |
| What does fibre do in relation to digestion? | Stimulates peristalsis and absorbs/stores water |
| What is the stomach? | A muscular bag that holds and digests food |
| What is the stomach lined with? | Mucosa |
| What is the function of the mucosa? | Heavily folded to form millions of gastric glands which produce gastric juice |
| What is gastric juice made of? | mucus, pepsinogen and hydrochloric acid |
| What in the stomach prevents self digestion? | A mucus coating |
| What are the functions of hydrochloric acid? | kills bacteria, loosens fibrous and cellular food, activates pepsinogen and denatures amylase |
| Describe mechanical digestion in the stomach | The contraction of the stomach digests the food and turns it into a thick, soupy mixture called chyme |
| What is the function of pepsinogen in the stomach? | Its an inactive enzyme that is converted into pepsin which digests protein and turning it into peptides |
| What is the function of the pancreas? | Secretes the hormone insulin and digestive materials which form pancreatic juice |
| What is pancreatic juice made of? | Sodium bicarbonate (which neutralises chyme), amylase and lipase |
| What does the liver breakdown? | red blood cells and amino acids |
| What is deanimation? | excess amino acids being broken down to form urea (to be excreted) |
| Where does deanimation take place? | The liver |
| Name other functions of the liver | produces bile, detoxifies the body, stores vitamin D and minerals, makes cholesterol, produces heat |
| What is bile made of? | bile salts, pigments and water) |
| Where is bile stored? | gall bladder |
| What is the function of bile? | neutralises chyme |
| Name the parts of the small intestine and name their functions | Duodenum (site of digestion) and Ileum (absorption) |
| What enters the duodenum? | Products of the liver and pancreas |
| What does the duodenum have that increases its surface area? | Inner lining contains infoldings called villi, which contain microvilli |
| In the duodenum, what does digestion produce? | monosaccharides, amino acids, fatty acids and glycerol |
| What does the duodenum produce? | Digestive enzymes |
| Name the adaptations of the villi in the ileum | large numbers of them to increase surface area, very thin to increase absorption, rich blood supply |
| Name the two main things that take place in the ileum | 1. Glucose and amino acids are absorbed into the bloodstream by diffusion and are carried to the liver by the lymphatic portal vein 2. Fatty acids and glycerol pass into the lacteals which are in the centre of each villus (lacteals contain lymph) |
| Name four adaptations of the small intestines that help it carry out its function | 1. It's very long 2. Numerous villi and microvilli 3. Rich blood supply to carry away water soluble products 4. Each villus has a lymph supply to carry away fats |
| Name the three parts of the large intestine | Caecum, colon, rectum |
| What is the end of the caecum called? | The appendix |
| What does the colon do? | Reabsorbs water from waste, forming faeces |
| Name the function of the appendix in herbivores | Breaks down cellulose |
| Name the function of the appendix in humans | Is a vestigial organ, it has lost its function |
| What vitamins are made in the colon and how? | Vitamins B and K - Bacteria in the colon feed on the waste products which produce the vitamins, which get reaborbed |
| What kind of bacteria lives in the colon and why? | Symbiotic bacteria which prevent the growth of pathogenic bacteria and fungi |
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sjbuzb
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