Olympiad Test: Human Body -2 - Class 4 MCQ

Explanation:
The correct answer is A: We should not chew the food. This statement is not true for the care of teeth. Chewing food is an essential part of the digestive process and helps promote oral health. Chewing stimulates the production of saliva, which helps to neutralize acids and wash away food particles from the teeth. Chewing also helps to break down food into smaller, more easily digestible pieces.
On the other hand, the other options are all true for the care of teeth:
B: We should eat raw fruits and vegetables: Raw fruits and vegetables are excellent choices for maintaining oral health. They are high in fiber, which helps stimulate saliva production and cleanse the teeth. They also contain vitamins and minerals that are beneficial for teeth and gums.
C: We should brush twice a day: Brushing twice a day is an important part of maintaining good oral hygiene. It helps remove plaque and food particles from the teeth, reducing the risk of tooth decay and gum disease. Brushing should be done with fluoride toothpaste and a soft-bristled toothbrush.
D: We should not eat too many sweets: Consuming excessive amounts of sweets can increase the risk of tooth decay. Sugary foods and drinks provide fuel for bacteria in the mouth, which produce acids that can erode tooth enamel. Limiting the intake of sweets is important for maintaining healthy teeth.
In summary, while all the options except A are true for the care of teeth, option A is not true as chewing food is an important part of maintaining oral health.

The blood flows to different parts of the body through:

1. Blood vessels: Blood vessels, including arteries, veins, and capillaries, play a crucial role in the circulation of blood throughout the body. They form a complex network that allows blood to reach every cell and tissue.


2. Arteries: Arteries carry oxygenated blood away from the heart and distribute it to various organs and tissues. They have thick, muscular walls that help maintain blood pressure and regulate blood flow.


3. Veins: Veins carry deoxygenated blood back to the heart after it has delivered oxygen and nutrients to the tissues. They have thinner walls than arteries and contain valves that prevent the backward flow of blood.


4. Capillaries: Capillaries are tiny, thin-walled blood vessels that connect arteries and veins. They are responsible for the exchange of oxygen, nutrients, and waste products between the blood and surrounding tissues.

Number of premolars in each jaw:
The number of premolars in each jaw is 4.
Explanation:
Premolars are the teeth located between the canines and molars. They are used for grinding and chewing food.
In each jaw, there are two premolars on each side, both in the upper and lower jaw. Therefore, in total, there are 4 premolars in each jaw.
Summary:
The number of premolars in each jaw is 4.

The number of teeth in a three-month-old baby is none. Here's why:
- Teething Process: The process of teething typically begins around 6 months of age. The baby's first tooth usually erupts between 6 to 10 months. However, it can vary from baby to baby, and some babies may start teething earlier or later.
- Development of Teeth: At three months of age, most babies have not yet started the teething process. The primary teeth, also known as baby teeth or milk teeth, develop beneath the gums during the first few months of a baby's life. The eruption of these teeth usually begins around 6 months.
- No Visible Teeth: At three months, it is unlikely for the baby to have any visible teeth. The baby's gums may appear smooth and without any signs of teeth pushing through.
- Teething Symptoms: Although the baby may not have teeth at three months, some babies may still experience teething symptoms. These symptoms can include increased drooling, chewing on objects, irritability, and mild discomfort. However, these symptoms can also be attributed to other developmental changes and may not necessarily indicate teething.
In conclusion, the number of teeth in a three-month-old baby is none. The teething process usually starts around 6 months, and the first tooth typically erupts between 6 to 10 months.

Teeth marked I represents incisors. Incisors are used for cutting.

Teeth between the canines and molars. premolars are also called as cracking teeth. Hence, Teeth marked III are also called Cracking teeth.

The outer portion of the tooth above the gum line is called the Crown.
The crown refers to the visible part of the tooth that is exposed above the gum line. It is composed of several layers, including the enamel, dentin, and pulp. Here is a breakdown of the different components of the tooth:
Enamel:
- The outermost layer of the tooth crown.
- It is the hardest substance in the human body.
- Provides protection to the underlying layers of the tooth.
Dentin:
- Lies beneath the enamel.
- It is a hard tissue that forms the main body of the tooth.
- Contains microscopic tubules that transmit sensations such as temperature and pain to the nerves in the pulp.
Pulp:
- Located in the center of the tooth.
- It is a soft, living tissue that contains blood vessels, nerves, and connective tissue.
- Supplies nutrients to the tooth and helps it maintain its vitality.
Root:
- The part of the tooth that is embedded within the jawbone.
- Anchors the tooth in place.
- Covered by a layer called cementum, which helps to attach the tooth to the surrounding bone.
In summary, while the pulp, dentin, and root are important parts of the tooth, the outer portion of the tooth above the gum line is referred to as the crown.

Wisdom teeth, also known as third molars, typically appear in a person's late teens or early twenties. Here is a detailed explanation for the correct answer, which is option C (20-25 years):
1. Introduction:
Wisdom teeth are the last set of molars to emerge in the mouth. They are called wisdom teeth because they usually appear when a person is older and wiser.
2. Age range for appearance:
Wisdom teeth most commonly appear between the ages of 20 and 25. However, the exact timing can vary from person to person. Some may experience the eruption of wisdom teeth slightly earlier or later than the typical age range.
3. Factors affecting the appearance:
Several factors can influence the timing of wisdom teeth eruption, including genetics, jaw size, and dental development. Some individuals may not develop wisdom teeth at all, while others may have them appear earlier or later than usual.
4. Signs of wisdom teeth eruption:
When wisdom teeth begin to emerge, individuals may experience symptoms such as gum swelling, jaw pain, and discomfort in the back of the mouth. These signs indicate that the wisdom teeth are trying to break through the gums.
5. Dental examination and extraction:
It is crucial to have regular dental check-ups to monitor the development of wisdom teeth. In some cases, the dentist may recommend removing the wisdom teeth if they are causing pain, crowding, or other oral health issues.
6. Conclusion:
In summary, wisdom teeth typically appear between the ages of 20 and 25, although there can be variations from person to person. Regular dental examinations and consultations with a dentist are important to monitor the development of wisdom teeth and address any potential complications.

Well Developed Teeth in Herbivores:
Herbivores have specialized teeth that are well adapted for their plant-based diets. The type of teeth that are particularly well developed in herbivores are the molars.
Molars in Herbivores:
- Molars are the large, flat teeth located at the back of the mouth, designed for grinding and chewing plant material.
- Herbivores require efficient grinding of plant matter to extract nutrients and break down tough fibers.
- Molars in herbivores have broad surfaces with ridges and cusps, which help in the efficient grinding and pulverizing of plant material.
- The large size and sturdy structure of molars allow herbivores to process a high volume of food and extract the maximum nutritional value.
- The constant wear and tear on molars from grinding tough plant matter are compensated by the continuous growth and replacement of these teeth in many herbivorous species.
Other Teeth in Herbivores:
- Incisors: These are the sharp front teeth used for biting and cropping vegetation. While herbivores may have well-developed incisors, they are not as specialized as the molars for grinding plant material.
- Canines: Canines are usually small or absent in herbivores as they are primarily used for tearing and capturing prey, which is not necessary for herbivorous feeding habits.
- Premolars: These teeth are located between the incisors and molars and can have various functions depending on the species. While premolars may play a role in herbivorous diets, they are not as specialized for grinding plant material as the molars.
In conclusion, herbivores have well-developed molars that are specifically adapted for grinding and processing plant material, making them essential for their dietary needs.

Digestion in the Small Intestine:
Introduction:
The small intestine is a crucial organ in the digestive system responsible for absorbing nutrients from food. The process of digestion in the small intestine involves several steps that aid in breaking down food and extracting essential nutrients for absorption into the bloodstream.
Release of Juices:
- The small intestine receives digestive juices from various organs, including the liver, gallbladder, and pancreas, which play a vital role in digestion.
- The liver produces bile, which is stored in the gallbladder and released into the small intestine. Bile helps in the breakdown and absorption of fats.
- The pancreas secretes pancreatic juice, which contains enzymes that further break down proteins, carbohydrates, and fats.
Enzymatic Breakdown:
- The small intestine produces its own digestive enzymes, such as peptidases, maltase, lactase, and sucrase. These enzymes help break down proteins into amino acids, carbohydrates into simple sugars, and fats into fatty acids and glycerol.
- The enzymes act on the food particles, breaking them down into smaller molecules that can be absorbed by the intestinal lining.
Surface Area for Absorption:
- The small intestine is lined with tiny finger-like projections called villi, which increase the surface area for absorption.
- Each villus contains even smaller projections called microvilli, further increasing the surface area.
- The nutrients resulting from the breakdown of food are absorbed through the villi into the bloodstream.
Transportation of Nutrients:
- Once absorbed, the nutrients move through the walls of the small intestine into tiny blood vessels called capillaries.
- From the capillaries, the nutrients are transported to the liver through the hepatic portal vein, where they are processed and distributed to the rest of the body.
Conclusion:
Digestion in the small intestine involves the release of digestive juices, enzymatic breakdown of food, and absorption of nutrients through the villi. This complex process ensures that the body receives essential nutrients for energy and growth.

Explanation:
When a person touches a hot metal, the body reacts immediately to protect itself from the high temperature. This response is a part of the body's natural defense mechanism to prevent burns or further damage to the skin. The following factors explain why the person withdrew their hand from the hot metal:
1. Thermal receptors:
- The human body has specialized nerve endings called thermal receptors that are sensitive to temperature changes.
- These receptors quickly detect the high temperature of the metal and send signals to the brain.
2. Reflex action:
- The brain receives the signals from the thermal receptors and immediately initiates a reflex action.
- Reflex actions are rapid, involuntary responses that occur without conscious thought.
- In this case, the reflex action causes the muscles in the hand to contract and withdraw the hand from the hot metal.
3. Pain sensation:
- When the skin comes into contact with a hot object, it stimulates pain receptors in the skin.
- The brain interprets this sensation as pain and triggers the withdrawal response to protect the body from potential harm.
4. Protective mechanism:
- The withdrawal of the hand from the hot metal is an automatic protective mechanism to prevent burns and further damage to the skin and tissues.
- By quickly removing the hand from the hot metal, the body aims to minimize the duration of contact and reduce the risk of injury.
Therefore, the person withdrew their hand from the hot metal due to the body's system that responds to high temperature, which includes thermal receptors, reflex actions, pain sensation, and a protective mechanism.

Answer:
The correct answer is Larynx. Here is a detailed explanation:
Larynx:
- The larynx, also known as the voice box, plays a crucial role in producing sound for speech.
- It is located in the throat and contains vocal cords that vibrate to create sound.
- The muscles in the larynx control the tension and position of the vocal cords, allowing us to produce different pitches and tones.
- The larynx also helps in controlling the volume and quality of our voice.
The other options mentioned do play a role in the process of speech, but they do not directly contribute to the production of sound. Here is a brief explanation of the other options:
Blood:
- Blood carries oxygen to the various organs and tissues in our body, including the lungs and larynx.
- While it is essential for the proper functioning of the vocal cords, it does not directly help in the production of speech.
Lungs:
- The lungs are responsible for the inhalation and exhalation of air.
- The air from the lungs passes through the larynx, where the vocal cords vibrate to produce sound.
- While the lungs provide the necessary airflow for speech, they do not directly contribute to the production of sound itself.
Windpipe:
- The windpipe, also known as the trachea, is a tube that connects the larynx to the lungs.
- It allows air to pass through and reach the lungs for respiration.
- While it is involved in the process of breathing, it does not directly contribute to the production of speech.
In conclusion, while the lungs, blood, and windpipe are all important for the overall process of speech, the larynx is specifically responsible for producing sound, making it the correct answer in this case.

Effects of smoking tobacco on the body:


There are numerous detrimental effects of smoking tobacco on the body. Here are some key points to consider:
1. Increased risk of cancer:
- Smoking tobacco is a leading cause of various types of cancer, including lung, throat, mouth, esophageal, pancreatic, bladder, kidney, and cervical cancer.
- It introduces harmful chemicals into the body, such as tobacco-specific nitrosamines, polycyclic aromatic hydrocarbons, and benzene, which can damage DNA and lead to the development of cancerous cells.
2. Respiratory issues:
- Smoking damages the respiratory system, causing chronic bronchitis, emphysema, and chronic obstructive pulmonary disease (COPD).
- It irritates and inflames the airways, leading to coughing, wheezing, shortness of breath, and an increased risk of respiratory infections.
3. Cardiovascular problems:
- Smoking tobacco increases the risk of heart disease, heart attacks, strokes, and peripheral vascular disease.
- The harmful chemicals in tobacco smoke can damage the lining of blood vessels, leading to the buildup of fatty plaques, narrowing of the arteries, and reduced blood flow to vital organs.
4. Weakened immune system:
- Contrary to the given options, smoking weakens the immune system, making individuals more susceptible to infections and diseases.
- It impairs the body's ability to fight off illnesses and slows down the healing process.
5. Other health complications:
- Smoking tobacco is linked to various other health issues, including osteoporosis, infertility, erectile dysfunction, type 2 diabetes, gum disease, and vision problems.
It is important to note that quitting smoking can significantly reduce the risk of developing these health problems and improve overall well-being. Seeking professional help and support can be beneficial for individuals who want to quit smoking and mitigate the harmful effects on their bodies.

Explanation:

When you breathe in, several processes occur in your body to allow for the intake of air. Let's break down each of the options to determine which one does not happen:

• Our lungs squeeze: When we inhale, our diaphragm, a dome-shaped muscle beneath our lungs, contracts and moves downward, causing our lungs to expand. This expansion creates space for air to enter the lungs. Therefore, our lungs do not squeeze during inhalation. This option is incorrect.



• The volume of our chest increases: As the diaphragm contracts and moves downward, the volume of the chest cavity increases. This expansion creates a negative pressure within the lungs, allowing air to rush in. This option is correct.



• Air rushes into our lungs: Due to the increased volume in the chest cavity, air rushes into the lungs. This option is correct.



• Our ribs are raised: When we inhale, the muscles between our ribs, called intercostal muscles, contract, causing our ribcage to expand. This expansion also helps to increase the volume of the chest cavity. This option is correct.

Based on the above analysis, it is clear that option A, "Our lungs squeeze," does not happen when we breathe in. Therefore, option A is the correct answer.