General Science Solutions Solutions for Class 6 Science Chapter 8 - Our Skeletal System And The Skin

Answer:

(a) The place where two or more bones are connected is called a joint.
(b)Cells of the epidermis contain a pigment called melanin.
(c) Epidermis and dermis are the two layers of the human skin.
(d)The human skeletal system is divided into two parts.

Answer:

Answer:

(a) Bones are soft- Wrong
Bones are hard and non flexible.

(b)The human skeleton protects the internal organs- Right

Answer:

(a) The system which gives a definite shape to our body.
$\mathbf{\square }$ Excretory system
$\mathbf{\square }$ Respiratory system
 Skeletal system
$\mathbf{\square }$ Circulatory system

(b) The ................ joint is seen in fingers and toes.
 Hinge joint
$\mathbf{\square }$ Ball and socket joint
$\mathbf{\square }$ Immovable joint
$\mathbf{\square }$ Gliding joint

Answer:

 a. The most important functions of the skin are:

• Protection − The skin provides protection to the body from mechanical injury, ultraviolet rays, from disease-causing microbes, and prevents desiccation.

• Temperature regulation − The skin helps in the maintenance of body temperature at a constant.

• The skin contains numerous sense receptors, which help in perceiving the surroundings.

• The skin is also involved in the synthesis of vitamins such as Vitamin D.

• The skin also helps in disposing off the excess water and salt by evaporation.​

Ans b. The following things should be done in order to keep our bones healthy and strong:

• Have calcium rich foods like milk, yoghurt as calcium is an important component of bones.
• We need to take enough vtiamin D as it helps in the absorption of calcium present in foods.
• Some other important nutrients like potassium, vitamin K and magnesium also help the body to absorb and use calcium. 
• Daily exercise is required to keep our bones in a state of good health.

Ans c. The skeletal system includes all of the bones and joints in the body. It performs the following functions:

• gives a definite shape to the body
• provides support and protection for the soft tissues that make up the rest of the body
• provides attachment points for muscles to allow movements at the joints

Ans d. Bones are structurs which are hard and non flexible. The chances of breaking of bones occurs, if the bones are weak. There are various reasons due to which bones may become weak and may break:

• certain diseases can result in weakening of the bones and cause them to break. For example, osteoporosis and arthirits are diseases which result in the weakening of bones
• defeciency of nutrients like calcium and vitamin D 
• certain stress or injury may result into fracturing of bones
• bone loss also occurs with age and thus making them more fragile
• alcohol and smoking also have a negative impact on bones and bone density

Ans e. There are 4 types of bones:

1. Flat bones: They are thin shaped and, in some cases, provide mechanical protection to soft tissues beneath or enclosed by the flat bone.
2. Irregular bones: They have complicated shapes which cannot be classified as 'long', 'short' or 'flat'. Their shapes are due to the functions they fulfill within the body.
3. Long bones: These type of bones are longer than wider and they function to support the weight of the body and facilitate movement
4. Short bones: They are almost cube shaped bones as they are equal in their length and width.

Answer:

a. Joints are the places where 2 bones are joined together. They permit the various kinds of movement which we carry out in order to fulfill our requirements. In absences of these joints our body would become stiff and we would not be able to carry out our daily tasks.

b. Melanin is a pigment which is found in skin and hair as well. It is important for two reasons, firstly it imparts colour to our skin and the tone of our skin depends on the amount of melanin pigment, secondly it protects our skin and the inner parts from ultravoilet rays. If the melaning pigment is absent, all the humans will have the same skin colour and we will become susceptible to the UV rays present in our atmosphere.

c. The 33 vertebrae together form the structure which we know as spine. They permit the movement of our spine so that we can bend it easily and carry out other functions. In other words we can say that they provide flexibilty to the spine. If in place of them, only one single and straight bone will be present then we would loose our flexiblity and remain in fixed positions. We would always stand straight like a pole and would not be able to sit down or perform other activities.

Answer:

(a) Types of joints

1. Gliding joint




2. Ball and socket joint


3. Hinge joint





(b.) Structure of skin