Solutions-Class 7-Science-Chapter-12-The Muscular System and Digestive System in Human Beings-Maha Board

(a) The process of digestion starts from the mouth.

(b) Eyelids have voluntary muscles.

(c) Production of blood cells is not a function of the muscular system. 

(d) Muscles of the heart are cardiac muscles.

(e) Pushing forward the food that has been chewed is the function of the oesophagus.​

The tongue, large intestine, appendix and lungs are lying.

1. Tongue can taste all the different tastes.

2. Liver is telling truth

3. Large intestine is 1.5 meter long.

4. Appendix does not perform any function in human body.

5. Lung is partial lying. It can perform in excretion, but not as important as performed by Kidneys in excretion.

The wall of the stomach has gastric glands, that produce mild hydrochloric acid in the stomach. As the food reaches the stomach, it gets mixed with the hydrochloric acid present there. Due to this food becomes acidic in the stomach.

Cardiac muscles are said to be involuntary because they are not controlled by our will. These muscles are found in heart and are the only muscles which work throughout the life time involuntry without getting tired or fatigue.

• Intoxicating substances should not be consumed because they harm the body health directly or indirectly.
• Alcohol cause damage to the nervous system and the digestive system as well.
• Liver is the main organ which is affected by alcohol.
• Tobacco is one of the leading causes of oral cancer.
• Smoking has a direct effect on the respiratory system of an individual and can lead to lung cancer as well.

• Our muscles should be strong and efficient because they carry out various vital functions in our body.
• Muscles helping us to breath, digest food, also in walking and lifting weights, muscles play an important role.
• If our muscles are not strong enough there can be various painful problems.
• Therefore the muscles should be strong and efficient.
• We can make our muscles strong and efficient by proper exercise and protein rich diet.

There are 3 types of muscles:

• Skeletal muscle fibres: They are found attached to the skeletal bones and are voluntary.
• Smooth muscle fibres: They are present in the walls of internal organs such as blood vessels, stomach, etc., and are involuntary.
• Cardiac muscle fibres: This is the only type of muscle present in the heart. They are contractile in nature and are involuntary.

Acid is produced by stomach. It is mild 0.5% HCL. It plays two important roles like:

1. It initiates protein digestion by activating the conversion of pepsinogen to pepsin.

2. It provides acidic medium for the activity of pepsin and other enzymes present in gastric juice.

However, if the level of this HCl exceeds its normal levels, it results in acidity/acid reflux, burning sensation in the throat and heart, headache, vomiting, rashes on skin etc. Exposure to higher levels of HCl for longer durations can also result in the development of peptic ulcers/ulcers in the stomach. 

There are 4 types of teeth which are found in humans:

1. Incisors are the teeth present at the front portion of the mouth. There are four incisors in each jaw. They are used for biting and cutting food.

2. Canines are located next to the incisors. There are two canines in each jaw. They are used for tearing and piercing food.

3. Premolars lie next to the canines. There are four premolars in each jaw. They are used for chewing and grinding food.

4. Molars lie next to the premolars at the end of the jaw. There are six molars in each jaw. They are also used for chewing and grinding food.

Digestion in Humans :

• The food that we eat passes through a Canal inside our body.
• The food is processed and utilized in the body and unused food is collected inside the canal only.
• This Canal is often called as the Alimentary Canal or the Digestive Tract.

 The canal is divided into different parts:

• The Mouth or Buccal Cavity
• Food Pipe or Oesophagus
• Stomach
• Small Intestine
• Large Intestine
• Anus

There are three glands associated with the alimentary canal that secrete digestive juices that are used to convert the complex food substances into simpler substances.

• liver
• pancreas
• salivary glands

Major constituent organs of the human digestive system are: buccal cavity, oesophagus, stomach, small intestine, large intestine, rectum and anus.

Buccal cavity − It includes the teeth, saliva and tongue. The teeth break down the food. Digestion of food begins in the mouth. The tongue helps in the chewing and swallowing of food.

Oesophagus − The food passes from the mouth, down the oesophagus, into the stomach, as a result of the movement of the walls of the oesophagus.

Stomach − It mixes the food received from the oesophagus with digestive juices.

Small intestine − The food from the stomach moves into the small intestine, which receives intestinal juices from two glands − liver and pancreas. These juices help in the further digestion of food.

Large intestine − Water is absorbed in the large intestine.

Rectum and anus − Undigested food particles are thrown out with the help of the rectum and anus.