Human Digestive System

This is a significant brush border enzyme.This enzyme decreases with age, and as such lactose intolerance is often a common abdominal complaint in the older population, manifesting with bloating, abdominal pain, and osmotic diarrhea.

Peyer's patches are covered by specialized epithelium (follicle-associated epithelium). Some of these epithelial cells have surfaces, which seem folded under the scanning electron microscope. These microfold, or M, cells sample and actively transport particulate antigens from the lumen into the dome area, where priming of both T and B lymphocytes occurs.

Fructose is absorbed by facilitated diffusion in the small intesstine.

Segmentation occurs only in the small intestine as short segments of intestine contract. Segmentation helps to increase the absorption of nutrients by mixing food and increasing its contact with the walls of the intestine.

The pancreas is also the main source of enzymes for digesting fats (lipids) and proteins. The enzymes that digest polysaccharides, by contrast are primarily produced by the walls of the intestines.

After passing through the small intestine, food passes into the large intestine. In the large intestine, some of the water and electrolytes (chemicals like sodium) are removed from the food. Many microbes (bacteria like Bacteroides, Lactobacillus acidophilus, Escherichia coli, and Klebsiella) in the large intestine help in the digestion process.

The skin is indeed the heaviest organ in the human body, weighing approximately 4-5 kg (9-11 lbs) in adults. It's also the largest organ by surface area, covering about 2 square meters. The liver is the second heaviest internal organ at 1.5 kg, but the skin's total mass makes it the heaviest overall.

Dehydration is the excessive loss of water from body tissues when fluid intake cannot replace fluid loss due to bleeding, diarrhea, vomiting, or excessive sweating. Rehydration is the process of restoring fluids, while retardation and deformation are unrelated to fluid loss.

Alkali proteases find extensive application in detergent and leather industries while Acidic proteases are used in cheese production.

The digestive system performs three main activities: Ingestion (taking in food), Digestion (breaking down food), and Elimination (removing waste). All these functions are essential, making 'All of the above' the correct answer.

The sphincter of Oddi is a muscular valve that controls the opening of the common hepatopancreatic duct (also called the common bile duct) into the duodenum. It regulates the flow of bile from the liver and digestive enzymes from the pancreas. It is not associated with the pyloric stomach, esophagus, or colon.

During swallowing, the soft palate (velum) elevates and the uvula swings backward to close off the nasopharynx. This prevents food/liquid from refluxing into the nasal cavity. The hard palate is anterior bone and doesn't move. Uvula alone cannot seal the opening.

Ruminants chew their cud through retro-peristalsis, which is the reverse movement of stomach contents from the rumen back to the mouth for additional mastication. This process, called rumination, allows more thorough breakdown of fibrous plant material. Regular peristalsis moves food forward through the digestive tract, not backward.

Horses are hindgut fermenters, and their colon is the principal site for nutrient absorption, particularly volatile fatty acids produced by microbial fermentation. Unlike ruminants (which have a rumen), horses rely on their enlarged colon for both fermentation and absorption. The rumen and ceacum are not the primary absorptive organs in horses.

In ruminants, the rumen is the primary site for absorption of fluid food and volatile fatty acids produced during fermentation. While the reticulum, omasum, and abomasum have important functions (storage, water absorption, enzymatic digestion respectively), the rumen's large surface area and vascularization make it the principal absorptive organ for fluid nutrients.