(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.

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

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

√ Skeletal system

√ Hinge joint

The most important functions of the skin are:

• Protection − Protection of body during heat or cold is done by the skin by regulation of body temperature.
• 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.
• Synthesis of vitamin ‘D’ is done by the skin in the presence of sunlight..
• The skin also helps in disposing off the excess water and salt by evaporation.​
• The skin is one of the sensory organs which helps in sensation of touch.

For keeping the bones strong and healthy, we need to take proper diet.

• The diet should contain calcium rich foods like milk, yoghurt as calcium is an important component of bones.

• We need to take enough vitamin 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.
• For obtaining these nutrients, milk, milk products, fruits, green leafy vegetables, eggs and meat should be consumed regularly. 
• Regular exercise, walking, cycling, etc. will keep the bones strong.

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.
• Movements of the body are possible due to bones and cartilages which are attached to muscles.
• Internal and vital organs are protected due to bones.
• 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.

• Minerals like calcium and phosphorus are stored inside the bones.

Bones are structures 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:

• Bones may break due to accidents and injuries. Falling from height or impact off hard object upon colliding can easily break the bones.
• 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
• Deficiency of nutrients like calcium and vitamin D 
• In old age, the bones become brittle due to lack of calcium and other nutrients.
• Alcohol and smoking also have a negative impact on bones and bone density.

There are 4 types of bones:

1. Long bones: These type of bones are longer than wider and they function to support the weight of the body and facilitate movement
2. Short bones: They are almost cube shaped bones as they are equal in their length and width.

3. Flat bones: They are thin shaped and, in some cases, provide mechanical protection to soft tissues beneath or enclosed by the flat bone.
4. 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.

Joints are the places where two bones are joined together. They permit the various kinds of movement which we carry out in order to fulfill our requirements. If there are no joints in our body, we will not be able to move. The bones can not show movements without joints

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 ultraviolet rays.

• If there is no melanin pigment in the skin, our skin will look absolutely white’
• The harmful ultraviolet rays of the sun will damage our internal organs due to absence of melanin.
• Melanin gives characteristic hues of colour and glow to our body, this will not be seen in the absence of melanin.

• 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.
• Due to individually joined vertebrae we are able to move, bend, walk, sit and work in any possible way.
• But if all the vertebrae are replaced by just one continuous bone, we will not be able to perform all these movements. ‘

Types of joints
1. Gliding joint

2. Ball and socket joint

3. Hinge joint

Structure of skin