Digestive System Anatomy and Function

The continuous tube from the mouth to the rectum that processes food and absorbs nutrients.

Organs like the salivary glands, liver, gallbladder, and pancreas that help digestion but don't directly house food or chyme.

The soupy mixture created as ingested food is broken down by stomach acids and enzymes.

The GI tract wall is made up of four layers: mucosa, submucosa, muscularis externa, and serosa.

The movement of food through the GI tract, including peristalsis (wave-like contractions) and segmentation (mixing contractions).

The breakdown of food into absorbable units through chemical (enzymes) and mechanical (chewing) processes.

The challenge of ensuring that the digestive system breaks down food, but not itself.

An inactive form of an enzyme that needs to be activated before it can perform its function. For example, digestive enzymes are secreted as zymogens to prevent them from digesting the cells that produce them.

Maintaining a constant volume of fluid within the digestive tract by balancing the amount of fluid entering and leaving.

Gut-associated lymphoid tissue - a collection of immune cells in the lining of the digestive system that helps protect the body against pathogens.

The process of taking nutrients from the digested food and transferring them from the digestive tract into the bloodstream.

The process of releasing fluids and electrolytes from the body into the digestive tract.

Wave-like muscle contractions that push food down the digestive tract.

Muscle contractions that mix food with digestive juices, but don't move it forward.

A complex network of neurons within the digestive tract that controls its functions, such as motility, secretion, and growth.

Neurons located entirely within the ENS, responsible for local control of digestive functions.

Neurons originating in the central nervous system (CNS) that connect to the digestive tract and influence its function.

Reflexes that are integrated and initiated within the ENS, allowing localized control of digestion.

Reflexes that integrate in the CNS, involving signals from the brain or other parts of the body that influence digestive processes.

A hormone released by the stomach that stimulates gastric acid production and growth of the stomach lining.

A hormone released from the small intestine that promotes digestion and has effects on the gallbladder and pancreas.

A hormone that inhibits the release of several other GI hormones, including gastrin, CCK, and secretin.

Hormones and other signaling molecules that influence digestion by regulating motility, secretion, and growth.

A mechanism that prepares the digestive system for incoming food by triggering the release of enzymes and hormones, even before food enters the mouth.

Nerve signals initiated by the brain, triggered by sights, smells, or thoughts of food, that prepare the stomach for digestion.

Fluid produced by salivary glands that contains enzymes to break down starch and lubricate food for swallowing.

The phase of digestion that takes place in the stomach, involving storage, digestion, and defense against pathogens.

Nerve signals initiated by the presence of food inside the stomach, triggering further digestive processes.

A hormone secreted by the small intestine in response to the presence of fats and amino acids. It slows gastric emptying, stimulates the release of pancreatic enzymes and bile, and promotes feelings of fullness.

CCK inhibits gastric emptying, slowing down the rate at which chyme enters the small intestine from the stomach. It also inhibits acid secretion in the stomach, further regulating the flow of acidic chyme.

Secretin inhibits further gastric emptying and acid secretion in the stomach to allow time for neutralization of the existing acidic load in the small intestine.

GIP stimulates the pancreas to release insulin, which helps to regulate blood glucose levels. It also inhibits gastric emptying, allowing for better time to absorb nutrients.

A hormone released in response to mixed meals containing carbohydrates or fats. It enhances insulin secretion, suppresses glucagon release, inhibits gastric emptying, and promotes feelings of satiety.

GLP-1 inhibits acid secretion in the stomach, contributing to slowing down gastric emptying and promoting satiety. It also suppresses glucagon release from the pancreas.

Motilin is inhibited during the fed (ingestion) state, allowing for proper digestion and nutrient absorption. Its release is triggered by fasting, facilitating the cleaning and preparation of the GI tract for the next meal cycle.