Glands associated with digestive system
Associated glands play crucial roles in digestion by producing and secreting various enzymes, hormones, and other substances necessary for breaking down food into absorbable nutrients. The primary associated glands are the salivary glands, the liver, the pancreas, and the gallbladder.
Salivary Glands
The salivary glands produce saliva, which contains enzymes that initiate the breakdown of carbohydrates in the mouth. There are three major pairs of salivary glands:
Parotid glands: Located near the upper cheeks, they secrete saliva rich in the enzyme amylase.
Submandibular glands: Found under the floor of the mouth, they produce a mixture of serous fluid (containing enzymes) and mucus.
Sublingual glands: Located under the tongue, they primarily secrete mucus, which helps lubricate and bind food particles together into a bolus for easier swallowing.
Liver
The liver is the largest gland in the body and has multiple functions related to digestion and metabolism:
Bile production: The liver produces bile, a substance that helps emulsify fats, breaking them into smaller droplets that enzymes can more easily digest.
Nutrient processing: After absorption in the intestines, nutrients pass through the liver, where they are metabolized, stored, or redistributed to other parts of the body.
Detoxification: The liver also detoxifies harmful substances, preparing them for excretion.
Gallbladder
The gallbladder stores and concentrates bile produced by the liver until it is needed in the small intestine. During digestion, particularly after the ingestion of fatty foods, the gallbladder contracts and releases bile into the duodenum through the bile ducts. This process aids in the digestion and absorption of fats.
Pancreas
The pancreas serves both endocrine and exocrine functions:
Exocrine function:
It produces pancreatic juice, which contains digestive enzymes (like lipase, protease, and amylase) and bicarbonate to neutralize stomach acid in the small intestine. These enzymes play a critical role in digesting fats, proteins, and carbohydrates.
Endocrine function:
It regulates blood sugar levels by producing insulin and glucagon, which are released directly into the bloodstream.
Carbohydrates Metabolism
The digestion of carbohydrates is a process that begins in the mouth and continues through the digestive tract, breaking down complex carbohydrates into simple sugars that the body can absorb and use for energy
In Mouth:
Chewing physically breaks down food into smaller pieces, increasing its surface area, while salivary amylase chemically acts on starch.
the enzyme salivary amylase present in saliva coverts approximately 30% of the polysaccharides into the disaccharides.
In Oesophagus:
Oesophagus doesn’t contribute to any chemical changes in carbohydrates. It just works a pathway for the food from the oral cavity to the stomach.
In stomach:
The acidic environment causes the activity of salivary amylase to halt, temporarily stopping carbohydrate digestion. The stomach’s primary role in carbohydrate digestion is mechanical, churning food to mix it with gastric juices and create a semi-liquid substance called chyme.
The acidity of the stomach (low pH) inactivates amylase, but no enzymes in the stomach continue the digestion of carbohydrates.
Small Intestine
Process: The bulk of carbohydrate digestion occurs in the small intestine. When chyme enters the duodenum (the first part of the small intestine), it triggers the secretion of pancreatic juice from the pancreas and bile from the liver.
Pancreatic Amylase:
This enzyme further breaks down remaining starch into maltose and dextrins.
Intestinal Enzymes:
The lining of the small intestine contains microvilli, known as the brush border, which secrete enzymes such as maltase, sucrase, and lactase.
These enzymes break down disaccharides (maltose, sucrose, lactose) into monosaccharides (glucose, fructose, galactose), which are the simplest forms of sugar that can be absorbed by the body
Absorption
The monosaccharides are then absorbed through the intestinal walls into the bloodstream. Glucose and galactose are absorbed via active transport, while fructose is absorbed via facilitated diffusion.
Large Intestine
Any undigested carbohydrates (mainly dietary fibers) pass into the large intestine, where they can be partially fermented by gut bacteria.
The fermentation process produces short-chain fatty acids, which can be used by the body as an energy source, and gases. Dietary fibers also help in the formation of stool and support healthy bowel movements