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प्रश्न
Write down the explanation.
Explain the structure of tooth.
उत्तर
Structure of tooth:
Tooth Anatomy
- A tooth consists of the portion that projects above the gum called crown and the root that is made up of two or three projections which are embedded in gum.
- A short neck connects the crown with the root.
- The crown is covered by the hardest substance of the body called enamel, which is made up of calcium phosphate and calcium carbonate.
- Basic shape of tooth is derived from dentin which is a calcified connective tissue.
- The dentin encloses the pulp cavity. It is filled with connective tissue pulp. It contains blood vessels and nerves.
- Pulp cavity has extension in the root of the tooth called root canal.
- The dentin of the root of tooth is covered by cementum, which is a bone like substance that attaches the root to the surrounding socket in the gum.
- We have four different types of teeth hence, we are heterodont. Types of teeth are incisors (I), canines (C), premolars (PM) and molars (M). Each half of each jaw has two incisors, one canine, two premolars and three molars.
- Thus, the dental formula of adult human can be represented as.
`I2/2, C1/1, PM2/2, M3/3 = (2, 1, 2, 3)/(2, 1, 2, 3)`
i.e. 8 × 2 = 16 teeth in each jaw = 32 teeths
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संबंधित प्रश्न
Why do we get instant energy from glucose?
The partially digested food coming from the stomach of a person enters a long and narrow organ A in his body. The organ A receives the secretion of two glands : liver and pancreas. Liver secretes a greenish-yellow liquid B which is normally stored in the organ C. Pancreas secretes pancreatic juice which contains three digestive enzymes D, E and F. The intestinal juice completes the process of digestion of food. The inner wall of organ A has millions of tiny finger-like projections G which help in the rapid absorption of digested food into blood stream. The undigested part of food then passes into wider tube H which absorbs most of the water from undigested food. The last part of tube H called I stores this undigested food (or waste) for some time. The undigested food is then passed out though opening J as faeces in the process known as K.
(a) Name the organ A.
(b) Name (i) liquid B, and (ii) organ C.
(c) What are the digestive enzymes D, E and F?
(d) Name the projections G present on the inner wall of organ A.
(e) Name (i) tube H (ii) part I (iii) opening J, and (iv) process K.
What do you mean by the absorption of food?
Define the following term:
Egestion
Differentiate between
Small intestine and Large intestine
Observe the diagram. This is the histological structure of the stomach. Identify and comment on the significance of the layer marked by an arrow.
A calcified connective tissue from which the basic shape of the tooth is derived is known as ______.
The coiled middle portion of the small intestine which is 2.5 meters long is the ______.
In which part of the alimentary canal food is finally digested?
Solve the crossword given in Figure 2.3.
| Across | Down | ||
| 1 | Cream-coloured digestive gland | 2 | Feeds with the help of pseudopodia |
| 3 | Undigested excretory solid residues | 6 | Total number of molars in one jaw of an adult |
| 4 | Organ that mixes saliva with the food | 8 | Largest gland |
| 5 | Point of defecation | 9 | Watery secretion in the mouth |
| 7 | Stored in gall bladder | 11 | A ruminant |
| 10 | Finger-like outgrowth in the small intestine | 12 | Form of food chewed by ruminants |
| 13 | Kind of taste buds | ||
| 14 | Kills bacteria in the stomach | ||
