有關牙齒的認識
參考下圖，回答以下問題:
Basic cognitive questions: (Suggested answers at the end)
What type of human tooth is shown above? Please explain.
What are the functions of this type of tooth? Do animals with different diets have different functions?
Besides this type of tooth, what other types of teeth do humans have? What are their functions?
List the names of P, Q, and R in the diagram above.
Using the letters in the diagram, indicate which part is the hardest. What component makes it hard?
Although teeth are strong, they can be easily eroded by a certain substance. What is it?
Using the letters in the diagram, indicate which structure in the tooth contains living cells.
What tissue supplies nutrients to the living cells in the tooth?
What is the definition of tooth decay (cavities)?
Using the letters in the diagram, indicate which structure, when exposed to external substances during tooth decay, causes pain.
Tooth decay does not always cause pain. Please explain why.
If the body lacks vitamin C, which structure in the tooth is more prone to bleeding? Please explain.
Using the letters in the diagram, indicate which part connects to the jawbone. What are the consequences if this part is damaged or inflamed?
Here is the English translation of your answers:
What type of human tooth is shown above? Please explain.
Answer: Molar or premolar. The surface is uneven and flat. It has two roots.
Explanation: The diagram does not clearly show whether the tooth has two or three roots. If it has three roots, it would be a molar.
What are the functions of this type of tooth? Do animals with different diets have different functions?
Answer:
For herbivores, molars have flatter surfaces, suitable for grinding tough plant fibers.
For carnivores, molars have more pointed structures, suitable for crushing hard substances (such as bones).
Besides this type of tooth, what other types of teeth do humans have? What are their functions?
Answer:
Incisors: Used for cutting food. They are chisel-shaped.
Canines: Used for tearing food (prey). They are pointed and curved inward.
Explanation: Compared to molars, canines are smaller and have only one pointed structure (while molars have multiple), making them unsuitable for biting hard materials (e.g., bones). Biting hard objects can easily fracture canines.
List the names of P, Q, and R in the diagram above.
Answer:
Using the letters in the diagram, indicate which part is the hardest. What component makes it hard?
Answer: P (enamel). It is mainly composed of calcium phosphate and is a non-living structure.
Although teeth are strong, they can be easily eroded by a certain substance. What is it?
Answer: Acid.
Explanation: Even weak acids can erode the enamel surface over time, leading to cavities.
Using the letters in the diagram, indicate which structure in the tooth contains living cells.
Answer: Q and R.
Explanation: Q (dentin) contains living cells that help replenish worn enamel. However, note that in adult humans, enamel does not regenerate, and teeth do not continue growing.
What tissue supplies nutrients to the living cells in the tooth?
Answer: The blood vessels within the pulp cavity (R).
What is the definition of tooth decay (cavities)?
Answer: The erosion of the tooth surface, leading to holes.
Using the letters in the diagram, indicate which structure, when exposed to external substances during tooth decay, causes pain.
Answer: U. U represents the nerve fibers in the pulp cavity, which sense pain and temperature changes.
Tooth decay does not always cause pain. Please explain why.
Answer: Pain is only felt when decay reaches the pulp cavity (R), where nerve fibers are located. Enamel (P) is non-living, and dentin (Q) has living cells but no nerve fibers, so damage to these areas does not cause pain.
If the body lacks vitamin C, which structure in the tooth is more prone to bleeding? Please explain.
Answer: S. S is the gum (gingiva). Vitamin C maintains healthy connective tissue. A deficiency weakens capillaries, making gums more prone to bleeding during brushing.
Using the letters in the diagram, indicate which part connects to the jawbone. What are the consequences if this part is damaged or inflamed?
Answer: V. V is the periodontal ligament or cementum (there are actually two different layers, but the diagram shows only one). If damaged, the tooth may become loose (even if the tooth itself is intact).
基本認知的問題: (建議答案在最後)
1. 以上的是人類哪一種類的牙齒? 試加以解釋。
2. 以上種類的牙齒有甚麼功能? 不同食性的動物有不同的功能嗎?
3. 除了以上種類的牙齒之外，人類還有哪些種類的牙齒? 功能又是甚麼?
4. 列出以上P、Q及R的名稱。
5. 試使用圖中的英文字母，列出以上哪一部分最堅硬? 是甚麼成份導致堅硬的?
6. 牙齒雖然堅固，但容易被一種物質侵蝕，是甚麼?
7. 試使用圖中的英文子母，列出牙齒內含有活細胞的構造。
8. 活細胞所需的營養來自牙齒內甚麼組織?
9. 蛀牙的定義是甚麼?
10. 使用圖中的英文字母，列出蛀牙時外界物質接觸到以上哪一構造，才會感到痛楚?
11. 蛀牙不一定會感到痛楚。試加以解釋。
12. 如身體不足維生素C，以上哪一構造會容易出血? 試加以解釋。
13. 使用圖中的英文字母，列出哪一部份與顎骨連接? 這部份如受損或發炎的話，會有甚麼影響?
基本認知問題建議答案:
1. 以上的是人類哪一種類的牙齒? 試加以解釋。
答: 臼齒或前臼齒。表面凹凸不平，扁平。有2個牙根。
解: 平面圖無法確定上圖的牙齒有2個抑或3個牙根，如有3個牙根的話，那便是臼齒。
2. 以上種類的牙齒有甚麼功能? 不同食性的動物有不同的功能嗎?
答: 對草食性動物而言，臼齒突出物較扁平，適合磨碎食物(主要是堅韌的植物纖維)
對肉食性動物而言，臼齒具較多尖突的構造，適合壓碎食物(主要堅硬的骨骼)
3. 除了以上種類的牙齒之外，人類還有哪些種類的牙齒? 功能又是甚麼?
答: 門齒: 用以切割食物。門齒呈鑿形。
犬齒: 用以撕咬食物(獵物)。犬齒尖而向內彎。
解: 相對臼齒，犬齒較細小，祇有一個尖突的構造(臼齒則有多個)，因此犬齒不適宜用以啃咬堅硬的物質(例如骨頭)，如啃咬堅硬骨頭的話，犬齒很易碎裂。
4. 列出以上P、Q及R的名稱。
答: P是琺瑯質; Q是齒質; R是髓腔。
解: 這三個詞彙是學習牙齒最重要的，必須熟記並同時清楚相關的組成構造。
5. 試使用圖中的英文字母，列出以上哪一部分最堅硬? 是甚麼成份導致堅硬的?
答: P (即琺瑯質)。主要由磷酸鈣組成，屬非生命的構造。
6. 牙齒雖然堅固，但容易被一種物質侵蝕，是甚麼?
答: 酸。
解: 即使是弱酸，長時間的話，琺瑯質表面一樣會被侵蝕，出現孔洞。
7. 試使用圖中的英文子母，列出牙齒內含有活細胞的構造。
答: Q及R。
解:
Q含活細胞，主要功能是補充不停被磨損掉的琺瑯質。但留意，人類成人牙齒的琺瑯質不會被補充，人類成人的牙齒不會不停生長。
8. 活細胞所需的營養來自牙齒內甚麼組織?
答: 來自髓腔內的微血管。
9. 蛀牙的定義是甚麼?
答: 牙齒表面被侵蝕，出現孔洞。
10. 使用圖中的英文字母，列出蛀牙時外界物質接觸到以上哪一構造，才會感到痛楚?
答: U。U是髓腔內的神經纖維，可感受痛及冷熱。
11. 蛀牙不一定會感到痛楚。試加以解釋。
答: 除非蛀牙已深入至髓腔(即上圖的R)，那裡才有神經纖維感受痛。琺瑯質是已死物質，齒質有活細胞，但沒有神經纖維，即使受損也不會有感覺。
12. 如身體不足維生素C，以上哪一構造會容易出血? 試加以解釋。
答: S。S是牙肉或稱為齒齦。維生素C可使結締組織健康，不足的話，微血管便容易破損，牙肉內滿佈微血管，因此刷牙時容易使牙肉出血。
13. 使用圖中的英文字母，列出哪一部份與顎骨連接? 這部份如受損或發炎的話，會有甚麼影響?
答: V。V是牙周膜或白堊質。(實際上有2層不同的組織。上圖祇顯示一種)。受損的話，牙齒會容易鬆脫。(即使牙齒本身沒有破損)
