Question

Name the glands present in the buccal cavity and write the components of food on which the secretion of these glands act upon.

Answer 1

Step 1: Understanding the salivary glands:
The salivary glands are located in the buccal cavity (mouth) and are responsible for producing saliva. There are three pairs of major salivary glands:
- Parotid glands: Located near the ears.
- Submandibular glands: Located beneath the lower jaw.
- Sublingual glands: Located beneath the tongue.

Step 2: The secretion of saliva:
The salivary glands secrete a watery fluid called saliva, which plays a crucial role in the digestion of food.
- Saliva moistens food, making it easier to chew and swallow.
- It also contains enzymes that help break down food components for easier absorption in the digestive system.

Step 3: Role of salivary amylase (or ptyalin):
One of the main components of saliva is the enzyme salivary amylase (also known as ptyalin).
- Salivary amylase begins the process of carbohydrate digestion in the mouth.
- It breaks down starch, which is a complex carbohydrate, into simpler sugars like maltose (a disaccharide).

Step 4: Action on carbohydrates:
- When food containing starch (such as bread or potatoes) enters the mouth, salivary amylase starts breaking down the starch into maltose.
- This process continues in the mouth and then further in the stomach and small intestine, where other digestive enzymes take over the breakdown.

Step 5: Conclusion:
Saliva, secreted by the salivary glands, contains the enzyme salivary amylase, which acts on carbohydrates (specifically starch), breaking it down into maltose, an essential step in the digestive process.

Answer 2

Step 1: Understanding the role of sphincter muscles:
Sphincter muscles are circular muscles that control the opening and closing of certain passages in the body. They act as valves, regulating the flow of substances in and out of organs.

Step 2: The pyloric sphincter in the stomach:
- The pyloric sphincter is located between the stomach and the duodenum (the first part of the small intestine).
- Its primary function is to regulate the passage of partially digested food (chyme) from the stomach to the small intestine.
- The pyloric sphincter prevents the backflow of intestinal contents into the stomach and ensures that the stomach empties its contents in a controlled manner.

Step 3: The anal sphincter in the anus:
- The anal sphincter is located at the end of the rectum, controlling the release of feces from the body.
- It consists of two muscles: the internal anal sphincter (involuntary control) and the external anal sphincter (voluntary control).
- The primary function of the anal sphincter is to regulate the expulsion of waste and maintain continence, preventing premature release of feces.

Step 4: Conclusion:
- The stomach is guarded by the pyloric sphincter, which controls the exit of partially digested food to the small intestine.
- The anus is guarded by the anal sphincter, which regulates the exit of waste from the body.
Both sphincters play a crucial role in controlling the passage of substances and ensuring proper bodily functions.

Answer 3

Step 1: Understanding the role of mucus in the stomach:
Mucus is secreted by the gastric glands in the stomach and serves as a protective layer for the stomach lining. It shields the stomach from the acidic gastric juices and mechanical damage.

Step 2: Consequences of no mucus secretion by the gastric glands:
If mucus is not secreted by the gastric glands:
- The stomach lining would be exposed to the harsh acidic environment created by hydrochloric acid and digestive enzymes like pepsin. - This can lead to ulcers (sores in the stomach lining) or gastritis (inflammation of the stomach lining) due to the continuous damage caused by the acid.

Step 3: Understanding the role of villi in the small intestine:
Villi are tiny, finger-like projections present in the lining of the small intestine. They significantly increase the surface area for nutrient absorption.

Step 4: Consequences of absence of villi in the small intestine:
If villi are absent in the small intestine:
- There will be a drastic reduction in the surface area for absorption of nutrients, leading to inefficient digestion and nutrient absorption. - This would result in malnutrition, as the body would not be able to absorb sufficient nutrients from food.

Conclusion:
(i) If mucus is not secreted by the gastric glands, it can lead to stomach ulcers or gastritis due to the lack of protection from acidic gastric juices.
(ii) If villi are absent in the small intestine, nutrient absorption will be severely impaired, leading to malnutrition.

Answer 4

Step 1: Understanding bile juice:
Bile juice is a digestive fluid produced by the liver and stored in the gallbladder. It is secreted into the small intestine to aid in digestion.

Step 2: Bile juice and its components:
Although bile juice does not contain digestive enzymes, it plays a crucial role in digestion. The primary components of bile juice include:
- Bile salts: These are the active components that help in digestion.
- Bile pigments: These are by-products of red blood cell breakdown (e.g., bilirubin).
- Water: It helps in maintaining the fluidity of bile.

Step 3: Role of bile juice in digestion:
Even without enzymes, bile juice has important roles in digestion:
- Emulsification of fats: Bile salts break down large fat globules into smaller droplets in a process called emulsification. This increases the surface area of fats, making it easier for pancreatic lipase (an enzyme) to act on them and break them down into fatty acids and glycerol.
- Neutralization of acidic chyme: The chyme (partially digested food) from the stomach is acidic. Bile juice helps neutralize this acidity, providing an optimal pH environment for the enzymes in the small intestine to function effectively.

Step 4: Conclusion:
Although bile juice does not contain enzymes, it plays a vital role in digestion by emulsifying fats and neutralizing stomach acids, thereby facilitating the action of digestive enzymes.