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1 第 6 課人的營養 79 Chapter 6 Nutrition in humans 人的營養 6.1 The processes of human nutrition: 人的營養過程 : Nutrition in humans consists of five processes: Ingestion, digestion, absorption, assimilation and egestion. 人的營養包括五個過程 : 攝食 消化 吸收 同化和排遺 1. Ingestion: Food is taken in through the mouth. 攝食 : 食物從口腔進入消化道 2. Digestion: Food is broken down into smaller, simpler and diffusible molecules by the digestive enzymes. 消化 : 利用消化酶將固體食物分解為細小 簡單和可擴散的份子 3. Absorption: The digested food enters the circulatory system. 吸收 : 已消化的食物進入循環系統 4. Assimilation: The absorbed food is taken up by cells for metabolism. 同化 : 已吸收的食物由細胞吸收, 用於新陳代謝 5. Egestion: The undigested food is removed from the body through the anus. 排遺 : 不能消化的食物從肛門排出體外 6.2 The human digestive system: 人的消化系統 : Digestive system = alimentary canal + digestive glands 消化系統 = 消化道 + 消化腺 Alimentary canal: it is a long tube running from the mouth through the body to the anus. 消化道 : 這是一條由口腔穿過身體直達肛門的長管, Includes : mouth, oesophagus, stomach, small intestine, large intestine, anus. 包括 : 口腔 食道 胃 小腸 大腸 肛門 Digestive glands : salivary gland, gastric gland, liver, intestinal gland, pancreatic gland. 消化腺 : 唾液腺 胃腺 肝 腸腺 胰腺 The lining of alimentary canal can secrete mucus for lubrication and protection. 消化道的內層能分泌黏液作潤滑及保護之用 6.3 Ingestion of food: 攝食 : Food is taken into the alimentary canal through the mouth. Then food is cut up by the teeth. 食物從口腔進入消化道, 跟著被牙齒切成小塊以利吞嚥 We have 4 types of teeth: incisor, canine, premolar and molar. They are different in shape, number and function. 人有 4 種牙齒 : 門齒 犬齒 前臼齒和臼齒, 它們的形狀 數目和功能都不同

2 80 第 6 課人的營養 Types of teeth 牙齒的種類 : Incisor Canine premolar and molar 門齒 犬齒 前臼齒 和 臼齒 Chisel shape: Sharply pointed : In herbivores : In carnivores: for cutting. for killing the prey the surface is rough with sharp cusps and tearing the flesh and sharply ridged for for crushing bones cutting and grinding grass. and cutting flesh. 鑿形尖銳在草食性動物 : 在肉食性動物 : 用作切斷食物 用作殺死獵物表面粗糙和有尖利具角狀尖突, 用作切 Internal structure of teeth : 牙齒的內部構造 : 和撕開食物的橫脊, 用作切斷斷及咬碎骨頭, 將骨 和磨碎植物體 上的肉片下來 ( 在人類 : 前臼齒與臼齒都是用作磨碎食物 ) 1. Enamel: the hardest material in the body, to prevent the wearing of the tooth, non-living. 琺瑯質 : 身體上最硬的物質, 防止牙齒磨損, 沒有生命 2. Dentine : the bony material of the tooth, living. 齒質 : 構成牙的主體, 頗硬, 有生命 3. Pulp cavity : contains blood vessels and nerves. 齒髓 : 含有血管和神經 4. Cement : to attach the tooth to the jaw bone. 白堊質 : 將牙齒固定於顎骨 5. Nerve : for the sensitivity of the tooth. 神經 : 負責牙齒的感覺 6. Blood vessel : to supply oxygen and nutrients to the tooth. 血管 : 供應氧氣和養份給牙齒 琺瑯最硬防磨損 齒質頗硬牙體建 白堊固牙於顎骨 齒髓血管神經現 神經負責牙感覺 血管氧氣營養獻 Closed tooth 閉合式牙齒 : (for reference 只供參考 ) In most mammals after the tooth has reached a certain size, it stops growing and the aperture of the tooth root is almost closed. The supply of nutrients and oxygen is just sufficient to keep the tooth alive, not to grow. 在大多數的哺乳類, 當牙齒生長到某一大小時, 便會停止生長, 而齒根管差不多會完全封 閉, 只留下少許空間, 少量的氧氣和營養的供應, 只夠維持牙齒的生存, 而非生長

3 第 6 課人的營養 81 Crown 牙冠 enamel 琺瑯質 dentine 齒質 Neck 牙頸 gum 牙齦 pulp cavity 齒髓腔 blood capillary 微血管 Root 牙根 nerve 神經 cement 白堊質 bone 顎骨 Structure of a tooth 牙的結構 Dentition and diet 齒系與膳食: Dentition : the number and arrangement of different types of teeth in a mammal. 齒系 ( 牙列 ): 哺乳類各種牙齒的排列形式和數目 Dental formula : the number and types of teeth on one side of the upper and lower jaws. 齒式 : 一邊上及下顎的各種牙齒數目 Sequence ( 次序 ) : icpm icpm Human 人類 : icpm icpm = Total 總數 = (32) incisors 門齒 Canine 犬齒 Premolar 前臼齒 Molar 齒臼 orbit 眼窩 upper jaw 上顎 IC P M Top view of lower j aw 下顎的俯視圖 wisdom tooth 智慧齒 lower jaw 下顎 IC P M Lateral view of jaw 顎骨的側面

4 82 第 6 課人的營養 Dentition is related with the diet (carnivorous, herbivorous, or omnivorous) of the mammals. 齒系和哺乳類的飲食習慣 ( 如肉食性 草食性或雜食性 ) 有關 Although basic structures of a carnivorous mammal, an herbivorous mammal and an omnivorous mammal are similar, their dentition and digestive tracts have been modified greatly to suit their different feeding patterns. 雖然肉食性動物 草食性動物和雜食性動物的身體結構非常相似, 但是牠們的齒系及消化道都各自作了一些改變, 以迎合不同的飲食習慣 All of them have incisors, premolars and molars. Herbivores (sheep) do not have canine. 牠們三者都有門齒 前臼齒和臼齒, 草食性動物 ( 羊 ) 沒有犬齒 Milk teeth and permanent teeth 乳齒和恆齒 : 1. Man have 2 sets of teeth. 人類有兩副牙齒 2. Number of teeth : Milk (20) ; permanent (32) 牙齒的數目 : 乳齒 :(20) ; 恆齒 : (32) 3. Premolar is absent in milk teeth. 乳齒沒有前臼齒 4. Advantages of having 2 sets of teeth : Allow the organisms to have suitable size of teeth at different stages of life. 有兩副牙齒的好處 : 可容許生物在不同的生命階段有合適大小的牙齒使用 Causes of tooth decay 蛀牙的成因 : 1. By the action of acids produced by the bacteria. 由細菌所產生的酸所造成 人類牙齒分四款 大小臼齒與犬門 咬碎食物增面積 加速消化利吞嚥 2. The film of bacteria is called plaque. 在牙齒上的細菌膜名為牙垢 3. Starchy and sugary food favour the growth of bacteria. 澱粉質和含糖的食物有利細菌的生長 4. Bacteria turns the food into weak organic acids. 細菌將食物變成弱有機酸 5. The acids corrode the enamel of the teeth (acid react with calcium). 這些酸腐蝕牙齒的琺瑯質 ( 鈣和酸發生反應 ) 蛀牙皆因細菌生澱粉和糖利菌增食物變成有機酸弱酸腐蝕琺瑯身 Periodontal disease : Plaque gets between the gum and teeth, This affects the gum and bone structure, and may result in bad breath, bleeding gums and loose teeth. 牙周病 : 如果牙石出現在牙肉和牙縫間, 便可能引致牙周病 牙周病會影響牙肉和顎骨的結構, 造成口氣 牙肉出血和牙齒鬆脫 Ways to reduce tooth decay 防止蛀牙的方法 : 1. Use tooth paste when brushing. 每次刷牙用牙膏 2. Brush the teeth after eating so as to remove food debris and plaque. 每次進食後刷牙以清除食物殘渣和牙垢 3. Add fluoride to the tap water. 食水中加入氟化物

5 第 6 課人的營養 Movement of food along the alimentary canal: 食物在消化道中的移動 : Function of the tongue 舌頭的功能 : 1. Tasting. 試味 2. Manipulate food between the teeth to facilitate chewing. 在牙齒間搬弄食物以利咀嚼 3. mix food with saliva and facilitate swallowing. 將食物和唾液 ( 口水 ) 混合以利吞嚥 Swallowing 吞嚥 : The trachea is closed by the epiglottis when swallowing, thus food is prevented from entering the lung. 吞嚥時, 會厭會遮蓋氣管, 防止食物進入肺部 Food is moved down the oesophagus (as well as alimentary canal) by peristalsis. 食物在食道 ( 以及消化道 ) 的向下移動靠蠕動 Peristalsis : involuntary rhythmic waves of muscular contraction stimulated by roughage. 蠕動 : 由粗糙食物刺激所引起的不自主節奏性波浪式肌肉收縮 6.5 Digestion 消化作用 : Peristalsis 蠕動 The need of digestion 消化的需要 : The food we eat are usually starch, proteins and fat whose molecules are too large to pass through the cell membranes / wall of digestive tract. 我們常吃的食物是澱粉 蛋白質和脂肪, 它們的分子過大, 不能穿過細胞膜 / 消化管壁 A. Physical digestion 機械消化 : Small food pieces have a larger surface area for the action of enzymes. 小塊的食物有較大的表面積讓酶作用 1 Mechanical actions of the alimentary canal: 消化道的機械動作 : chewing by teeth in the mouth cavity 口腔內牙齒的咀嚼 churning in the stomach 胃的劇烈攪動 peristalsis along the alimentary canal 消化道的蠕動 2 Emulsification of lipids by bile salts in the small intestine 小腸內的膽鹽將脂肪乳化 食物分子太大個不能穿過細胞膜消化酵素來分解細小簡單可通過 B. Chemical digestion 化學消化 : The food pieces after physical digestion are not yet small enough for absorption. They need further break down into molecular form by digestive enzymes. 經機械消化後的食物碎不夠細小以讓細胞吸收, 要用消化酶將它們分解為分子的形式

6 84 第 6 課人的營養 澱粉質 (Starch) 葡萄糖 (glucose) 蛋白質 (Protein) 氨基酸 (amino acids) 脂肪 (Fats) 脂肪酸和甘油 (fatty acids and glycerol) 1. Mouth cavity 口腔 : Saliva is secreted by salivary glands. 唾液是由唾液腺所分泌 Function of saliva: 唾液的功能 : 1. Saliva sticks food particles together and act as a lubricant when swallowing. 唾液可將食物粒黏在一起, 當吞嚥時作為潤滑劑 2. It contains an enzyme amylase which digest starch into maltose. 它含有一種消化酶 唾液澱粉酶, 可將澱粉消化成麥芽糖 2. Stomach 胃部 : Stomach wall secretes gastric juice which contains: 胃壁可分泌胃液, 胃液含有 1. Hydrochloric acid (HC1), ph = 2. 鹽酸 HCl (ph = 2) HC1 kill bacteria and activate enzymes. 鹽酸可殺菌 ( 消毒 ) 和活化酶 2. Protein digestive enzymes (pepsin) 蛋白消化酶 ( 胃蛋白酶 ) It converts proteins to peptones. 將蛋白質消化成腖 Function 功能 : 1. Stores food. 儲藏食物 2. Absorption of simple molecules (water, glucose and alcohol) 吸收簡單的份子 ( 水 葡萄糖 酒精等 ) 3. Partial digestion of protein 部分消化蛋白質 Partial digestion of protein only, no digestion of carbohydrates 只能部份消化蛋白質, 沒有碳水化合物的消化 Why is the stomach not digested by its own enzymes? 為什麼胃不會被自己的消化酶所消化? 1. The whole surface of the alimentary canal is covered with mucus for the lubrication of food as it passes along and for the protection of the gut lining against enzyme action. 整個消化管道都由黏液所覆蓋, 一則潤滑食物的通過, 二則保護腸道免受消化酶所 消化 舌頭試味搬食物 唾液潤滑黏食物 酵素唾液澱粉酶 澱粉化成麥芽糖 Stomach 胃 胃部出口有兩個 儲藏食物及吸收 胃壁可分泌胃液 內有鹽酸和酵素 鹽酸殺菌活化酶 部分消化蛋白質 胃部不會被消化 黏液保護酶未活

7 第 6 課人的營養 Digestive enzymes are produced in inactive forms (pepsinogen). It can ensure the enzyme produced will not digest the glandular cells while it is still within the cells. 剛製造的消化酶 ( 胃蛋白酶原 ) 是不活躍的, 這可確保消化酶不會消化製造它的腺細胞 palate 軟顎 buccal cavity 口腔 salivary glands 唾液腺 tongue 舌頭 pharynx 喉頭 trachea 氣管 liver 肝 gall bladder 膽囊 bile duct 膽管 pyloric sphincter 幽門括約肌 pancreatic duct 胰管 epiglottis 會厭軟骨 oesophagus 食道 diaphragm 橫膈膜 cardiac sphincter 賁門括約肌 stomach 胃 pancreas 胰臟 duodenum 十二脂腸 colon 結腸 ileum 迴腸 caecum 盲腸 appendix 蚓突 rectum 直腸 anus 肛門 The human digestive system 人類的消化系統

8 86 第 6 課人的營養 Check point 測試站 (12) 1. State the five processes of human nutrition. 說出人獲取營養所包括的五個過程 2. State all the digestive glands. 說出所有的消化腺 3. Explain the need of digestion. 解釋消化的需要 4. What is digestion? 解釋消化作用 5. Describe the shape and function of incisor. 簡述門齒的形狀和功能 6. Describe the shape and function of canine. 簡述犬齒的形狀和功能 7. Explain the importance of chewing food. 解釋咀嚼食物的重要性 8. State the function of enamel, dentine, pulp cavity, cement, nerve and blood vessel? 說出琺瑯質 齒質 齒髓腔 白堊質 神經和血管的功用? 9. What type of teeth is absent in milk teeth? 乳齒缺少了何種牙齒? 10. Explain the causes of tooth decay. 解釋蛀牙的成因 11. State the cause of periodontal disease and its effect. 簡述牙周病的成因及其影響? 12. Suggest some ways to reduce tooth decay. 建議一些減少蛀牙的方法 13. Describe the functions of saliva. 簡述唾液的功能 14. What is meant by peristalsis? 蠕動是什麼意思? 15. State the function of stomach? 胃有什麼功用? 16. Name the components of gastric juice and state their functions. 說出胃液的成分和它們的功能 17. Why does baby can digest milk but most adult cannot? 為什麼嬰兒能消化鮮奶, 但成人卻不能? 18. Why is the stomach not digested by its own enzymes? 為什麼胃不會被自己的消化酶所消化?

9 第 6 課人的營養 Small intestine 小腸 : It is composed of duodenum and ileum. 由十二指腸和迴腸組成 Bile, pancreatic juice and intestinal juice are released into the small intestine. 膽汁 胰液和小腸液被釋入小腸 (a) Bile 膽汁 : It is secreted by liver and stored in gall bladder. 由肝臟製造, 儲存在膽囊 It neutralizes the acid and gives an alkali medium for the duodenal enzymes. 可中和酸性的食糜, 提供一鹼性環境給小腸的消化酶 Components 成份 : (1) bile pigment : break down products of haemoglobin, green and useless. 膽色素 : 血紅素分解後的產品, 綠色, 無用 (2) bile salts : emulsify the fats, increase surface area for the latter enzymes to act on. Speed up the digestion of fats. It is not an enzyme so will not be affected by heat. 膽鹽 : 乳化脂肪 ( 將油變成微小的油點 ), 增加脂肪與脂肪酶接觸的表面積, 加 速脂肪的分解 它不是酶所以不受熱影響 (3) sodium bicarbonate : alkaline, neutralize the acid chyme. 重碳酸鈉 : 鹼性, 可中和酸性的食糜 (b) Pancreatic juice 胰液 : It is secreted from the exocrine glands of the pancreas. 由胰臟的外分泌腺製造 It is alkaline, neutralize the acid chyme. 鹼性, 可中和胃酸和提供一鹼性環境給消化酶作用 Pancreas 胰 It contains enzymes which digest carbohydrates (pancreatic amylase), proteins (trypsin), fats (lipase) and nucleic acids (nuclease). 含有可消化碳水化合物 ( 胰澱粉酶 ) 蛋白質 ( 胰蛋白酶 ) 脂肪 ( 脂肪酶 ) 和核酸 ( 核 酸酶 ) 的消化酶 (c) Intestinal juice 小腸液 : It is secreted from walls of small intestine, and contains all food enzymes (carbohydrases, proteases and lipases) for complete digestion of food. 小腸液由小腸壁分泌, 含有所有消化酶 ( 碳水化合物酶 ( 羧酶 ) 蛋白酶和脂肪酶 ), 可完成食物的消化 小腸酵素三處瀝 膽囊胰臟小腸壁 十二指腸接膽胰 迴腸絨毛通處植 吸收食物增面積 膽汁肝造儲膽囊 乳化脂肪不怕燙 乳化大油變小油 增加面積消化幫 4. Large intestine 大腸 : Composed of caecum, colon and rectum. 由盲腸 結腸和直腸組成 It absorbs water and salts (colon) and stores faeces (rectum). 吸收水 鹽和礦物質 ( 結腸 ), 暫時儲藏糞便 ( 直腸 ) 結腸吸收水和鹽 直腸暫時儲糞便

10 88 第 6 課人的營養 Digestion of cellulose 纖維的消化 : (for reference 只供參考 ) Cellulose cannot be digested by most animals because they lack the enzyme, cellulase. This enzyme is found in some protozoans and in some bacteria. Herbivorous mammals utilize these bacteria to digest cellulose, a phenomenon known as symbiosis. eg. Horses and rabbits have large caecum containing symbiotic bacteria which can secrete cellulase to digest cellulose to glucose. 大部分的動物都不能消化纖維, 因為牠們缺少一種酶 纖維素酶 某些原生動物和細 菌能製造這種纖維素酶, 草食性哺乳類可利用此等細菌去消化纖維, 建立一種名為共 生的關係 例如 : 馬和兔子都有很大的盲腸, 內有共生菌, 共生菌可分泌纖維素酶, 將纖維素消化成葡萄糖 6.6 Absorption 吸收作用: Most absorption takes place at the small intestine. The absorptive area is greatly increased by finger like structure called villi projecting into the lumen of the gut. Each villus is covered by an absorptive epithelium, and contains capillaries and a lacteal (lymph vessel). 大部分的吸收作用都是在小腸內進行, 腸內有名為絨毛的手指狀凸出物, 伸進腸的內腔 中, 使吸收表面大為增加, 每條絨毛都被一層吸收表皮所覆蓋, 內含微血管和乳糜管 ( 淋 巴系統 ) To increase efficiency, the epithelium is thin. This reduces the barrier of absorption. Each villus is richly supplied with capillaries and lacteal. This facilitates diffusion or absorption of food across the epithelium. 為了增加效率, 表皮都是非常薄的, 這可減少吸收的障礙, 以進一步增加吸收面積, 這有 助食物的吸收 villus 絨毛 epithelial cell 表皮細胞 epithelial cell 表皮細胞 Lumen 腸腔 lacteal 乳糜管 capillary 微血管 structure of a villus 絨毛的結構 section of a villus 絨毛的橫切面 lacteal 乳糜管 capillary 微血管 T.S. of small intestine showing villi 小腸內腔顯示絨毛

11 第 6 課人的營養 89 Absorption of glucose and amino acids: 葡萄糖和氨基酸的吸收: These molecules are absorbed through the epithelium of the gut to the capillaries of the villi, due mostly to active transport which consumes energy (ATP). Diffusion plays a relative minor role in this process. 這些分子穿過絨毛表皮進入絨毛的微血管內, 吸收主要是依靠主動轉運, 故需要能量 (ATP), 在這吸收作用中, 擴散作用只扮演一個微小的角色 Absorption of fat 脂肪的吸收 : This is absorbed by lacteals (a part of the lymphatic system). 脂肪是透過乳糜管吸收 ( 淋巴系統的一部分 ) 的 The fat absorption occurs in two ways 主要透過以下二個途徑被吸收 : (a) As fatty acids and glycerol, in intestinal epithelium resynthesis into fat. 以脂肪酸和甘油的形式, 在腸上皮內再結合成脂肪 (b) As small fat droplets resulting from the emulsification by bile. 以小油點的形式 小油點由膽汁的乳化而來 Absorption of water 水分的吸收 : Water (90%) is mainly absorbed by the small intestine. The rest is absorbed by blood capillaries of the large intestine under osmotic activity because the contents in the lower gut is usually hypotonic to blood. 絨毛內藏微血管 包著中央乳糜管 若論絨毛的特色 好薄多血大面積 葡萄氨基微血吸 脂酸甘油乳糜入 維生礦物各物質 水溶入血脂乳吸 食物吸收緣擴散 主動運輸吸物質 水分 (90%) 主要被小腸吸收, 其餘的藉滲透作用被大腸的微血管吸收, 因腸腔內的物質相 較血液是較為低滲性的 Absorption of vitamins and minerals 維生素與礦物質的吸收 : They are absorbed in unchanged conditions; minerals and water-soluble vitamins into blood while fat-soluble vitamins into lymph. 它們於沒有改變的狀況下被吸收, 礦物質和水溶性維生素會被吸進血管, 而脂溶性的維生 素會被吸進乳糜管 How does the structure of small intestine adapt to its functions? 小腸的構造如何適應它的功能 : (1) The millions of finger-like villi cover the entire surface of the intestinal lining. 小腸的內壁充滿過百萬的手指狀絨毛 (2) The villi are greatly folded to increase the surface area for absorption. 絨毛都是高度摺疊, 以增加吸收表面積 (3) The wall of the villi are thin (with only one layer of epithelial cells) and this permit the food to diffuse through easily. 絨毛的體壁都是很薄的, 只有一層上皮細胞, 這可使食物能快速通過它 (4) The epithelial cells lining the villi have cylindrical projections called brush border microvilli. These further increase the surface area of absorption. 每個絨毛表皮細胞都有一些圓筒形名為邊緣刷絨毛的凸出物, 可進一步增加吸收面積

12 90 第 6 課人的營養 (5) The villi contain blood capillaries to absorb glucose and amino acids through the hepatic portal system to the liver. 絨毛含有微血管以吸收葡萄糖和氨基酸, 然後透過肝門靜脈將它們送往肝臟 (6) The villi contain lacteals to absorb fatty acids and glycerol. 絨毛含有乳糜管用以吸收脂肪酸和甘油 (7) Glandular cells in epithelial lining which secrete digestive enzymes for digestion of food molecules as they pass through. 小腸內壁含有能分泌消化酶的腺細胞, 將食物分解 (8) Circular and longitudinal muscles involved with peristalsis. They mix the digestive juices with chyme so promoting hydrolysis of food by the enzymes. 有環形肌和縱走肌, 使蠕動可以進行 蠕動可將食穈和消化液混合, 使食物被酶分解 (9) Mucus secretion which protects epithelium. 能分泌黏液以保護腸腔內的表皮 villus 絨毛 6.7 Assimilation 同化作用: Assimilation is the uptake and use of food molecules by body cells. 同化作用是身體把營養素轉化成可以運用的形式 1. Carbohydrates 碳水化合物 : They are the main respiratory substrates. They are absorbed in the form of glucose and enter the liver through the hepatic portal vein. In liver, excess glucose is converted to glycogen for storage. The glycogen will be reconverted into glucose by liver when the sugar concentration in blood is low. 它們是主要的呼吸基質, 它們以葡萄糖的形式被吸收, 然後由肝門靜脈運往肝臟 在 肝臟, 過多的葡萄糖被轉化成糖原作儲藏 在血糖濃度低時, 糖原會轉回葡萄糖, 釋 進血內 The interconversion of glucose and glycogen is controlled by two hormones : insulin and glucagons (explain later). The capacity of the liver to store glycogen is limited. When the maximum capacity of glycogen has been reached, the excess carbohydrates will be converted to fat. 葡萄糖和糖原的轉換受二種激素所控制 胰島素和高血糖素 ( 稍後解釋 ) 肝臟能儲存 的糖原是有限的, 當所儲藏的糖原達到極限時, 過多的碳水化合物會轉化成脂肪 2. Fats 脂肪 : Fat carried by the lymphatic system would be emptied into the blood stream at the base of the neck. Therefore, blood will contain fat. Fats can be used as a respiratory substrate. Fats are stored as adipose tissues beneath the skin or around internal organs. They form an insulating layer beneath the skin to reduce heat loss from the body. They are also important structural materials of the protoplasm, cell membrane, and the myelin sheath of nerve fibers. 脂肪被淋巴系統運往頸底的血管 ( 與上腔大靜脈連接 ), 所以血液含有脂肪 脂肪可作 為呼吸受質, 脂肪是以皮下脂肪組織的形式儲於皮下層, 或是包圍著內臟器官 它們 在皮下層形成一個隔溫保護層, 以防止熱量從身體散失 它們是原生質的重要結構物 質, 亦用於合成細胞膜 神經纖維表面的磷脂髓鞘

13 第 6 課人的營養 Proteins 蛋白質 : Proteins are absorbed as amino acids. The latter after entering the body are used to build up proteins which may be used as structural materials such as protoplasm, or as synthetic materials such as enzymes or hormones. 蛋白質是以氨基酸的形式被吸收, 氨基酸進入身體後會用作製造蛋白質, 而蛋白質會 用於合成原生質 酶和激素 Excess amino acids are not stored. They are deaminated at the liver. Deamination is the removal of the amino group (-NH 2 ) by certain enzymes in liver, producing a keto acid and ammonia : 過多的氨基酸不能儲藏, 它們在肝臟被脫氨基, 脫氨基作用是將氨基組 (-NH2) 移除, 產 生酮酸及氨 : R.CH. NH 2 COOH + 1/2O 2 R.CO.COOH + NH 3 Amino acid 氨基酸 keto acid 酮酸 ammonia 氨 As ammonia is poisonous, it has to be converted to non-toxic forms tolerable to the body, eg. as urea or uric acid. Some keto acids are converted to glucose while some others are oxidized to carbon dioxide and water. 因為氨是非常毒的, 它必須轉化成身體能接受的沒有那麼毒的形 式, 例如尿素和尿酸 部分酮酸會轉化成葡萄糖, 或氧化成二氧 化碳和水 6.8 Egestion 排遺作用: The undigested food is egested from the body through the anus. 不能消化的食物, 從肛門排出體外 葡萄氨基入肝臟由血運往各部藏脂酸甘油在乳糜再次結合為脂肪淋巴系統注入血所以血液含脂肪 Roughage 基糠 : These are indigestible cellulose fibers that give bulk to the intestinal contents. This stimulates peristalsis of the gut and thus prevents the contents from staying too long in the colon; otherwise excess water will be removed so that the faeces become too hard and dry and are difficult to be egested, a condition called constipation. 它們是不能消化的纖維, 使小腸內的物質成團狀, 它們刺激腸的蠕動, 可防止食物在結腸 內停留過久, 否則過多的水分會被吸收, 使到糞便非常乾硬, 那時就很難排遺, 稱為便秘 6.9 Function of the liver 肝臟的功能: 1. Deamination of amino acids (excess amino acids cannot be stored). 將氨基酸進行脫氨基作用 ( 過剩的氨基酸不能儲藏 ) 2. Conversion of carbohydrates to fat. 將碳水化合物轉化成脂肪 3. Storage of iron. 儲藏鐵質 4. Secretion of bile. 分泌膽汁 Liver 肝

14 92 第 6 課人的營養 5. Storage of glycogen (muscle also store glycogen) 儲藏糖原 ( 肌肉亦可儲藏糖原 ) 6. Storage of vitamin A, D, E and K and minerals including potassium, iron and copper. 儲藏維生素 A D E K 和包括鉀 鐵和銅等礦物質 7. Production of heat. 產生熱能 8. Interconversion of glucose and glycogen. 葡萄糖和糖原的相互轉換 9. Detoxication : poisonous substances in blood are neutralized by the liver cells. 解毒作用 : 血液內有毒的物質被肝臟細胞中和 口訣:肝臟功能有排講, 脫脂鐵膽儲熱糖 Check point 測試站 (13) 19. Name the sources that small intestine receives digestive juice. 說出小腸所接收的消化液的來源 20. Name the components of small intestine. 說出小腸的成員 21. Which ducts are connected to duodenum? 有那些管接往十二指腸? 22. Name the finger like projections in ileum and state its importance. 說出迴腸內的手指狀突出物的名稱和它的重要性 23. Where is the bile juice produced and stored? 膽汁是在何處產生和儲在何處? 24. What is bile pigment? 膽色素是什麼? 25. What is the function of sodium bicarbonate? 重碳酸鹽有什麼作用? 26. What is the function of bile juice (salts)? 膽汁 ( 鹽 ) 有什麼功用? 27. Will the bile salts be affected by heat, why? 膽鹽會否被熱力所影響, 為什麼? 28. Will the secretion of bile stop after the removal of gall bladder, why? 切除膽囊後是否沒有膽汁分泌, 為什麼, 這對消化有什麼影響?

15 第 6 課人的營養 Can bile digest fat into fatty acids and glycerol? 膽汁能否將脂肪消化成脂肪酸和甘油? 30. What is the function of pancreatic juice? 胰液有什麼功能? 31. Name the different parts of large intestine. 說出大腸的不同部分 32. State the function of colon. 說出結腸的功用 33. State the function of rectum. 說出直腸的功用 34. State the components of faeces. 說出糞便內含的物質 35. At which part of the gut is water absorption mainly take place? 腸的那一部分是吸水的主要地方? 36. Name the site of food absorption in small intestine. 說出小腸用作吸收食物的組織名稱 37. State and explain the features of absorptive surface. 說明和解釋吸收面的特徵 38. Which part of the villus absorbs glucose and amino acids? 絨毛的那一部分會吸收葡萄糖和氨基酸? 39. Which part of the villus absorbs fats? 絨毛的那一部分會吸收脂肪? 40. Explain why does the lacteal become milky after a meal of fatty food. 解釋為什麼一個人吃了肥膩食物後, 他體內的乳糜管變為乳白 41. Explain the absorption of vitamins and minerals. 解釋如何吸收維生素和礦物質 42. By what mechanism is the food absorbed into the villi? 食物的吸收是靠什麼機制的? 43. Describe the fate of the absorbed glucose and amino acids. 簡述被吸收了的葡萄糖和氨基酸將往何處 44. Describe the fate of the absorbed fatty acids and glycerol. 簡述被吸收了的脂肪酸和甘油將將往何處 45. How do different nutrients assimilate in the body? 不同的營養素怎樣在細胞內被同化?

16 94 第 6 課人的營養 Concept Map 概念圖 人的營養作用 Nutrition in man 包括五個步驟 Include 5 steps 消化道 Alimentary canal 包括 Include 攝食 Ingestion 把食物研碎依靠 Break down food by 消化作用 Digestion 包括 Include 吸收作用 Absorption 地點在 Occurs at 同化作用 Assimilation 發生地 Occurs at 排遺作用 Egestion 口腔 Mouth 食道 Oesophagus 胃 Stomach 十二指腸 Duodenum 迴腸 Ileum 結腸 Colon 直腸 Rectum B 肛門 Anus 牙齒 Teeth 門齒 Incisor 犬齒 Canine 前臼齒 Premolar 臼齒 Molar 包括 Include 齒式 Dentition 數目及排列次序 Number and Arrangment 機械消化 Physical digestion 牙齒咀嚼 Chewing by Teeth 胃的攪動 Churning in stomach 蠕動 P eristalsis 膽鹽乳化 Emulsification by bile 包括 Include 化學消化 Chem ical digestion 消化 Enzymes 碳水化合物 carbohydrase 蛋白 Protease 脂肪 Lipase 微血管 Capillary 單糖 氨基酸 礦物質 水溶性維生素 水 Glucose, amino acids, minerals, water soluble vitamins and water 絨毛 Villi 擴散作用 Diffusion 主動轉運 Active transport 負責吸收和轉運 Responsible for absorption and transport of 吸收藉 Absorbed by 絨毛內有 Contain 乳糜管 Lacteal 脂肪 脂溶性維生素 Lipids and fat soluble vitamins 身體細胞 Body cells 主要經 Through 肝門靜脈 Heptic portal vein 肝臟 Liver 到 To 功能 Functions 排出不能消化的食物 Undigested food is egested 脫脂鐵膽儲熱糖 Deamination,storage of iron,glycogen and vitamins, secretion of bile,etc.

17 第 6 課人的營養 95 Misconceptions 錯誤觀念 : 1. Enamel and dentine cannot grow because they are dead. 琺瑯質與齒質不能生長因它們是死物 2. Our saliva contains an enzyme which can digest starch to glucose. 我們的唾液含有可將澱粉消化成葡萄糖的酵素 3. There will be no bile secretion after removal of gall bladder. 切除膽囊後便沒有膽汁分泌 4. Bile juice digest lipids into fatty acid and glycerol. 膽汁將脂肪消化成脂肪酸和甘油 5. After gall bladder removal surgery, we should not eat fatty food because there will be not enough bile to digest lipids into fatty acid and glycerol. 切除膽囊後不應進食脂肪食物因為沒有膽汁分泌來將脂肪消化成脂肪酸和甘油 6. The main water absorption region in intestine is colon. 在腸主要吸收水分的區域是結腸 7. The indigestible food is excreted in the form of faeces. 不能消化的食物以糞便形式排泄出體外 8. Excess amino acid will be deaminated in liver and become urea. 在肝臟過剩的氨基酸脫氨基後變成尿素 9. Excess amino acid will be stored as protein in our body. 過剩的氨基酸以蛋白質的形式儲藏在身體內 10. Absorption only takes place at duodenum and ileum. 吸收作用只在十二指腸和迴腸中進行 11. Lipids are carry to every part of the body through lymphatic circulation. 脂肪經淋巴循環運送到身體各部分

18 96 第 6 課人的營養 Answers of misconceptions 錯誤觀念的答案 : 1. Enamel is not living, but the cells of pulp cavity send cytoplasmic strands into dentine, so dentine can grow and undergo metabolism. 琺瑯質是沒有生命的, 但齒髓腔的細胞將細胞質幼絲伸進齒質, 故此齒質可生長及進 行代謝 2. Amylase can only turn starch into maltose. 唾液澱粉酶只能將澱粉消化成麥芽糖 3. Bile will still be secreted from liver even without gall bladder. However it cannot be stored in gall bladder. This will affect digestion of lipids as only limited amount of bile will be released into duodenum when food enters it. 沒有膽囊, 膽汁仍會由肝繼續分泌, 雖然它不能儲在膽囊 這會影響脂肪的消化, 因 為當食物進入腸道時只有少量膽汁分泌進十二指腸 4. Bile cannot digest lipids, it can only emulsify fat into oil droplets. This is physical and not chemical action. 膽汁不會消化脂肪, 它只能將脂肪乳化成小油點, 這是物理作用而非化學作用 5. Bile production continues but cannot store in gall bladder, so there will be not enough bile to emulsify fats. 仍會有膽汁分泌但不能儲在膽囊, 結果沒有足夠膽汁乳化脂肪 6. Water mainly absorbed in small intestine. 吸收水分主要在小腸內進行 7. This is egestion and not excretion. The indigested food is not metabolic waste which comes from cellular activities. Faeces is not excretory substance. 這作用名叫排遺作用而非排泄作用, 不能消化的物質不是從細胞活動產生的廢物, 故 冀便不是排泄物 8. Excess amino acid will be turned to ammonia and keto acid. Ammonia combine with CO 2 to form urea. 過剩的氨基酸脫氨基後變成氨和羧酸, 氨和二氧化碳結合成尿素 9. Excess amino acid cannot be stored in body in the form of protein. They are deaminated in liver to form ammonia and keto acid. 過剩的氨基酸不能以蛋白質的形式儲藏在身體內, 它們在肝臟脫氨基成氨和和羧酸 10. Although absorption mainly takes place at duodenum and ileum, but colon and stomach can still absorb some simple substances. 雖然吸收作用主要在十二指腸和迴腸中進行, 但結腸和胃也可以吸收一些簡單物質 11. Lymph ducts only responsible for the transport of lipids just after absorption. Lymph ducts connect with blood vessels. Lymph will return to blood, so lipids are transport all over body by blood circulation. 淋巴管負責運送吸收後的脂肪, 最終與血液循環相連 所以, 脂肪是經由血液循環運 送至身體各部分