Tag: structure and functions of living organisms -ii

Entamoeba gingivalis is a protozoan endoparasite, residing in the tartar and pus pockets of teeth of pyorrhoea infected human beings. It is the first parasitic amoeba known to human beings. 

The skeletal system is divided into an axial and appendicular skeleton and it provides both support protection to the brain as well as give shape to the face. The skull is part of the axial skeleton. Skull or cranium has 22 bones out which mandible  (lower jaw) is a single bone. It is lowest and strongest bone which hold the lower teeth in the socket and gives shape to the face. 

Hardest substance of the body is enamel. It is the thin outer covering of the tooth. It is composed of hydroxyapatite, which is a crystalline calcium phosphate. The color can vary from light yellow to a grayish white. It protects the tooth.

There are several types of teeth and each performs its own special function in the chewing process, depending on its size, shape, location within the jaws. Starting at the midline, the permanent dentition is comprised of incisors, canines, premolars and molars.
Therefore, the correct answer is option D.

Teeth are the hardest substance in the human body. The enamel on your teeth is the hardest and most highly mineralized substance in your body. It covers the outer layer of each tooth and it is the most visible part of the tooth. The enamel is made up mostly of minerals, primarily hydroxyapatite. So, enamel is the hardest substance in our body compared to dentine, collagen and melanin. 

Dental pulp is an unmineralized oral tissue composed of soft connective tissue, vascular, lymphatic and nervous elements that occupies the central pulp cavity of each tooth. Pulp has a soft, gelatinous consistency. The pulp cavity extends down through the root of the tooth as the root canal which opens into the periodontium via the apical foramen. The blood vessels, nerves etc. of dental pulp enter and leave the tooth through this foramen. This sets up a form of communication between the pulp and surrounding tissue - clinically important in the spread of inflammation from the pulp out into the surrounding periodontium. 

Dentine is the calcified tissue of the body, is one of the components of the teeth along with enamel, cementum and pulp. It is generally surrounds the entire pulp is a covering beneath the enamel. 70% of the weight of dentine is made up of mineral hydroxylapatitie, while 20% is organic material and the rest 10% is water.

• The canines are the pointed and the sharp teeth which are found in the mouth of the humans. 
• These are the teeth that are used for tearing of the food. The sugarcane is made up of tough fibers. These fibers can be torn with the help of canine teeth. 
• Thus, the correct answer is option B. 

Human teeth have two sets of teeth during their life one temporary set of milk teeth and one permanent set. Once the milk teeth have replaced by permanents, then the permanent teeth are not going to replace again in life naturally after 12 years of age.