Test Your Knowledge With Our Nutrition Physiology Quiz

Cholecystokinin (CCK) is a hormone released by the small intestine in response to fatty acids and amino acids in the chyme. It triggers the pancreas to release digestive enzymes and stimulates the gallbladder to release bile. Gastrin primarily stimulates acid secretion in the stomach, while secretin triggers bicarbonate release from the pancreas to neutralize stomach acid. Enterogastrone is not a specific hormone but a general term for substances that inhibit gastric activity.

Peristalsis refers to the rhythmic, wave-like contractions that occur in the walls of the GI tract, moving food along from the esophagus to the intestines. This involuntary action is crucial for digestion and nutrient absorption. Segmentation involves mixing contractions within the intestines, mastication is chewing, and deglutition is the act of swallowing.

The large intestine is primarily responsible for absorbing water and electrolytes from undigested food material. While the small intestine absorbs most nutrients and some water, the large intestine reabsorbs water and salts to form solid waste. The stomach is involved in protein digestion, and the liver aids in detoxification and bile production, not absorption.

Salivary amylase, produced by the salivary glands, begins breaking down starches into maltose and dextrins in the mouth. This enzyme does not act on proteins, lipids, or nucleic acids, as these require different enzymes and a lower pH to be digested effectively.

The liver produces bile, which helps emulsify fats in the small intestine, allowing for efficient breakdown by lipases. While the pancreas secretes enzymes and bicarbonate to neutralize stomach acid, bile production and fat emulsification are the liver’s primary roles in digestion.

The pyloric sphincter is a muscular valve that controls the passage of partially digested food (chyme) from the stomach to the small intestine. It prevents backflow and regulates the pace of digestion. It does not control bile, pancreatic enzymes, or waste release from the large intestine.

Pepsin, produced in the stomach, is the primary enzyme that initiates protein digestion by breaking down protein chains into smaller peptides. It functions optimally in the acidic environment of the stomach. Trypsin and chymotrypsin, produced in the pancreas, continue protein digestion in the small intestine, while lactase breaks down lactose.

Proteases, such as pepsin in the stomach, are active in a low pH environment, which aids in the breakdown of protein molecules. Amylases and lactase require neutral to slightly alkaline pH levels to function, and "hydrolases" is a general term for enzymes that catalyze hydrolysis reactions without specifying an acidic environment.

Infra-orbital glands are not present in humans. Humans have three major salivary glands: the parotid, submaxillary (submandibular), and sublingual glands. These glands produce saliva, which contains enzymes like amylase for carbohydrate digestion, and play an essential role in moistening food for swallowing.

Rennin, also known as chymosin, is an enzyme produced in the stomach, specifically in infants, to curdle milk, slowing its passage and allowing for proper digestion. In adults, rennin is generally absent, and pepsin takes over protein digestion in the stomach. This enzyme is crucial for milk digestion during early development.

Casein is the primary protein in milk, constituting about 80% of milk proteins. It provides essential amino acids and calcium and plays a crucial role in muscle and tissue development. Rennin (also known as chymosin) is an enzyme, not a protein, that aids in curdling milk in infants. Galactose is a simple sugar in milk, and glycine is an amino acid found in various proteins but not specifically associated with milk.

Goblet cells, found throughout the lining of the digestive and respiratory tracts, produce mucus to protect the epithelial lining from digestive enzymes and mechanical damage. Mucus also helps trap particles and pathogens, aiding in immune defense. Parietal cells secrete hydrochloric acid in the stomach, oxyntic cells produce gastric acid, and chief cells release pepsinogen, a precursor to the enzyme pepsin for protein digestion.

Human saliva has a slightly acidic to neutral pH, typically ranging from 6.8 to 7.2, which is ideal for the function of enzymes like salivary amylase that start carbohydrate digestion. This pH also helps maintain oral health by inhibiting harmful bacteria while supporting beneficial bacteria. Lower or higher pH levels may disrupt this balance, leading to dental and digestive issues.

Cannibalism is the act of consuming individuals of one’s own species. In nature, cannibalism occurs in certain species as a survival strategy during scarcity or as a behavior for population control. In human society, however, cannibalism is culturally taboo and rare. Cannibalistic behaviors can be found in various animals, including fish, insects, and mammals, under specific environmental or social conditions.

Protein digestion is highly dependent on the acidic environment in the stomach, where the enzyme pepsin requires a low pH to function effectively. A basic stomach pH would inhibit pepsin's activity, impeding protein breakdown. The stomach's acidity also helps denature proteins, making them easier for enzymes to act upon. Carbohydrate and lipid digestion primarily occur in the small intestine, where a neutral to slightly basic environment is maintained.