Food is one of the most fundamental requirements for living entities to survive. In humans, the digestive system consists of the digestive glands and the alimentary canal. Food provides all the minerals, vitamins and organic compounds that are required to grow and repair the body. Water plays a vital role in the digestion process and prevents the body from entering a state of dehydration. Biomolecules in food cannot be utilized by our body and hence need to be broken down into simpler substances in the digestive system. This process is known as digestion. Read on to learn more about digestion and absorption of food.
Very Short Answer Type Questions
Q.1. What is the food called when food blends completely with acidic gastric juices of the stomach by the churning movements of the muscular wall.
A.1. The food stays in the stomach for 4-5 hours during which it gets blended completely with the acidic gastric juice present in the stomach through churning movements of the muscular walls. At this point, the food is referred to as chyme.
Q.2. Name the tissue or cells that secrete the enzyme enterokinase which activates Trypsinogen. How is it activated?
A.2. The enzyme enterokinase activates trypsinogen to trypsin. The enzyme is secreted by the intestinal mucosa.
Q.3. Where in the alimentary canal, absorption of water, alcohol and simple sugars take place?
A.3. In the wall of the stomach.
Q.4. List the enzymes that are involved in the breakdown of nucleotides into bases and sugars.
A.4. Nucleotidases and nucleosidases.
Q.5. What is digestion?
A.5. Digestion is the process of converting complex food substances into simpler substances that can be absorbed through mechanical and biochemical methods.
Q.6. Name the type of teeth-attachment to the jaw bones wherein each tooth is embedded in a socket of jaw bones.
Short Answer Type Questions
Q.1. What is pancreas? What are the main secretions of the pancreas which aids in digestion?
A.1. The pancreas is a gland that has endocrine and exocrine parts required in producing hormones and digestive enzymes. The inactive enzymes involved in digestion and secreted by pancreas are as follows:
Q.2. Write the organs of the human alimentary canal. Mention the major digestive glands along with their locations
A.2. The alimentary canal consists of the anterior opening – the pharynx, buccal cavity, mouth, oesophagus, stomach, small intestine, large intestine, and anus.
The digestive glands are –
Salivary glands – Saliva is produced by 3 pairs of salivary glands which are – the parotids (cheek), the submandibular/sub-maxillary(lower jaw) and the sublingual (under the tongue).
The pancreas – It is located between the limbs of the C-shaped duodenum.
The liver – It is located in the abdominal cavity, below the diaphragm
Q.3. What is the significance of the gall bladder? Write the consequence if it stops functioning or is removed.
A.3. The gall bladder is a pear-shaped sac-like composition which is connected to the dorsal surface of the liver via connective tissue. The hepatic cells of the liver secrete bile which moves through the hepatic ducts gets accumulated in the gall bladder.
If the gall is removed or turns non-functional, the bile would continuously run from the liver into the intestine, without being concentrated enough as the bile originated in the gall bladder. A low-fat diet is suggested even though the body adapts as the digestion of fat is seemingly decreased after gall bladder is removed.
Q.4. Write the three major types of cells present in the gastric glands. List their secretions.
A.4. Gastric glands are present in the mucosa of the stomach. The three major cells are:
|Mucous neck cells||Mucus|
|Chief or peptic cells||Proenzyme pepsinogen|
|Oxyntic or parietal cells||HC1 and intrinsic factor|
Q.5. How is the intestinal mucosa guarded against the acidic food entering from the stomach?
A.5. The highly concentrated hydrochloric acid rich food is prevented from excoriation because of the mucus secreted by the goblet cells along with the bicarbonates which are significant in lubrication and protection of the mucosal epithelium.
Long Answer Type Questions
Q.1. Write the changes occurring in the passage through the alimentary canal when a person has ingested roti and dal as part of his meal.
A.1. The following are the changes:
- The teeth in the mouth masticate the food substances, wherein the carbs in the food are digested through the action of the enzyme secreted by the salivary gland – salivary amylase
- The food at this stage is partially digested and reaches the stomach. Here it is treated with acidic HCl. The proteins in the food are digested through the proteolytic enzymes.
- The gall bladder secrets the bile to digest the lipids present in the food
- The semi-digested food is finally digested in the duodenum of the small intestine by the action of digestive enzymes in the pancreatic and intestinal juices.
- The small intestine thus absorbs the disintegrated food in the form of glycerol, amino acids, starch, etc after digestion
- The food that is not digested in finally eliminated from the system through the anus.
Q.2. Write the mechanism of absorption.
A.2. It is the phenomenon through which the end products of digestion pass via the intestinal mucosa into the lymph or blood which is carried out through active, passive or facilitated transport means. Through simple diffusion, little quantities of monosaccharides such as amino acids, glucose and few electrolytes such as chloride ions are absorbed. The concentration gradients decide the passage of these substances into the blood. But amino acids and glucose are absorbed with the aid of carrier proteins and is referred to as facilitated transport. Water transport is dependant on the osmotic gradient. Active transport requires energy as it takes place against the concentration gradient. Through this mechanism, several monosaccharides such as glucose, nutrients such as amino acids, electrolytes such as Na+ are absorbed into the blood.
Q.3. What is the significance of hepato-pancreatic complex in digesting protein, carbohydrate and fat components of food?
A.3. The pancreatic and bile duct secretes bile and pancreatic juices into the duodenum through the common duct – the hepato-pancreatic duct which is shielded by a sphincter of Oddi. The pancreatic juice includes inactive enzymes –
The effect of hepato-pancreatic secretion on the digestion of fats, proteins, and carbohydrates are as follows:
- Hydrolysis of carbohydrates in the chyme into disaccharides by pancreatic amylase
- Fats are disintegrated into diglycerides and monoglycerides by lipases along with the aid of bile
- Proteolytic enzymes of the pancreatic juice act upon the proteins in the chyme that reach the intestine to produce proteases.
Q.4. How does digestion occur in the buccal cavity? Explain with the arrangement of teeth.
A.4. The buccal cavity has two important functions –
- Masticates food
- Facilitates swallowing
The tongue and the teeth with aid of saliva, masticate and blend the food completely. The mucus present in saliva helps in lubricating and holding the masticated food particles into a bolus. The bolus is further passed into the pharynx and down the oesophagus by deglutition or swallowing. The bolus moves through successive waves of contractions of the muscles down the oesophagus, this movement is known as peristalsis.
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