Digestive System Functions and Organs

Ingestion, mechanical breakdown (chewing), initiation of propulsion (swallowing), and the start of polysaccharide digestion.

Part of the palate formed by the palatine bones and palatine processes of the maxillae.

Closing off the nasopharynx during swallowing with the uvula.

Gripping, repositioning, mixing of food to form a bolus, swallowing, speech, taste.

Gives the tongue its rough texture for gripping food and contains no taste buds.

Cleanse mouth, dissolve food for taste, moisten food, and start starch digestion.

Parotid, submandibular, and sublingual glands located outside the oral cavity, producing most saliva.

Mostly water, enzymes (amylase), and protective substances (lysozyme, IgA, defensins).

Membrane covering the external surface of most digestive organs.

Membrane lining the abdominal cavity wall.

Space between visceral and parietal peritoneum, filled with serous fluid.

Double-layered peritoneum connecting abdominal wall to organs.

Organs located within the peritoneum.

Organs located outside the peritoneum.

Fat-containing mesentery draped over the abdominal organs.

Structure of the digestive tract's wall layers of tunics.

Innermost layer of the alimentary canal wall; does absorption and secretion.

Connective tissue layer beneath the mucosa; contains blood/lymph.

Smooth muscle layer responsible for gut movements (peristalsis, segmentation).

Outermost layer (mostly visceral peritoneum), coating the digestive organs.

Gut's own nervous system; controls motility (movement).

Inflammation of the peritoneum.

Reflexes mediated entirely by the enteric nervous system.

The digestive system breaks down food into nutrient molecules, absorbs these molecules into the bloodstream, and eliminates indigestible remains.

The digestive system consists of the alimentary canal (GI tract) and accessory digestive organs.

The organs of the alimentary canal are the mouth, pharynx, esophagus, stomach, small and large intestine, and anus.

Accessory digestive organs include teeth, tongue, gallbladder, salivary glands, liver, and pancreas.

Ingestion, propulsion, mechanical breakdown, digestion, absorption, and defecation are the six activities involved in food processing.

Peristalsis is the wave-like contraction and relaxation of muscles in the alimentary canal that propels food through the system.

Segmentation is the rhythmic contractions of the small intestine that mix food with digestive juices and enhance absorption.

Digestion involves breaking down complex food molecules into smaller units, while absorption involves the passage of these units into the bloodstream.

Demineralization of tooth enamel and dentin caused by bacterial action, leading to cavities.

A sticky film on teeth composed of sugar, bacteria, and debris, which can lead to cavities.

Hardened dental plaque that disrupts the seal between teeth and gums, leading to gingivitis.

Inflammation of the gums caused by bacteria, usually caused by calculus buildup.

A tooth that remains trapped in the jawbone, often causing pain and pressure.

The part of the pharynx that allows the passage of food, fluids, and air.

A muscular tube that transports food from the pharynx to the stomach.

The process of controlling the amount and composition of gastric juice, a mix of digestive fluids produced by the stomach.

The nervous system's role in regulating gastric juice production via nerve signals.

Chemical messengers (hormones) that influence gastric juice production.

Hormone that stimulates HCl secretion by the stomach.

The 'thinking' phase where gastric juice production is stimulated by food anticipation.

The phase when food reaches the stomach and triggers most of the gastric juice release.

The phase where partially digested food enters the small intestine and regulates gastric juice production.

A reflex where the small intestine sends signals to the stomach to slow down gastric juice production.

Hormones released by the small intestine that inhibit gastric juice production.

The process by which parietal cells in the stomach produce hydrochloric acid (HCl).

The increase in bicarbonate ions (HCO3-) in the blood as a result of HCl production.

The process of controlling the muscular contractions of the stomach to move and empty food.

The ability of the stomach to expand and accommodate incoming food.

The small intestine sends signals to the stomach to slow down emptying when it's full.

The forceful expulsion of stomach contents through the mouth.

Swallowing has two phases:

1. Buccal (voluntary): Tongue pushes food into the oropharynx.
2. Pharyngeal-esophageal (involuntary): Swallowing center in brain stem controls this phase, stopping breathing briefly.

The stomach temporarily stores food, initiates protein digestion by converting food into chyme, and releases chyme into the small intestine.

The stomach can expand significantly, from 50 ml when empty to 4 L when full, thanks to folds called rugae.

The stomach has 4 main regions:

1. Cardia: Surrounds the opening from the esophagus.
2. Fundus: The dome-shaped top region.
3. Body: The middle section.
4. Pyloric region: The lower section with a valve (pyloric sphincter) controlling food release.

Mesenteries attach the stomach to other digestive organs:

1. Lesser omentum: Connects to the liver.
2. Greater omentum: Drapes over the intestine, spleen, and transverse colon, contains fat and lymph nodes, and blends with the mesocolon (for anchoring).

Heartburn happens when stomach acid backs up into the esophagus, often due to overeating, obesity, pregnancy, or a hiatal hernia (stomach protrusion).

The stomach wall has 4 layers, like most digestive organs, but with an extra muscle layer (oblique) for churning and a unique mucosa.

The stomach's mucosa is made of simple columnar epithelium; it's protected by a mucous layer and contains gastric pits that lead to gastric glands.

Parietal cells in the stomach secrete:

1. HCl: Activates pepsin and denatures proteins.
2. Intrinsic factor: Needed for vitamin B12 absorption.

Chief cells secrete pepsinogen, an inactive enzyme that is activated to pepsin (for protein digestion) by HCl and pepsin itself.

The stomach is protected from its harsh environment by a thick mucus layer, tight junctions between cells, and quick replacement of damaged cells.

Gastritis is inflammation of the stomach lining, often caused by bacteria or NSAIDs. Persistent damage can lead to ulcers and potentially bleeding.

The stomach holds food, mixes it, breaks it down mechanically, starts protein digestion with HCl and pepsin, and absorbs some substances like alcohol.

Intrinsic factor is essential for vitamin B12 absorption in the small intestine, which is crucial for red blood cell maturation. Lack of it leads to pernicious anemia.

Bile is a fluid produced by the liver that helps in fat digestion. It acts as an emulsifier, breaking down large fat globules into smaller droplets, increasing their surface area for digestion by enzymes.

Bile is stored in the gallbladder, a small sac-like organ located beneath the liver. The gallbladder concentrates the bile by absorbing water and ions, making it more potent.

The pancreas secretes pancreatic juice, which contains digestive enzymes for breaking down carbohydrates, proteins, and fats. It also secretes bicarbonate, which neutralizes the acidic chyme from the stomach, protecting the small intestine.

The liver is the largest gland in the body, weighing about 3 pounds. It has a vital role in many functions, including digestion, detoxification, and protein synthesis.

The liver's main function in digestion is to produce bile. Bile is a substance that helps break down fats into smaller droplets, making them easier to digest.

Liver sinusoids are leaky capillaries located between hepatic plates. Blood from both the hepatic portal vein and hepatic artery flows through them, allowing for nutrient and oxygen exchange, and removal of waste products.

Enterohepatic circulation is the recycling process of bile salts. Bile salts are reabsorbed in the small intestine, return to the liver via the blood, and are reused in the production of new bile.

Gallstones can obstruct the flow of bile from the gallbladder, leading to pain and potential complications like jaundice (yellowing of skin).

The liver performs numerous functions, including production of bile, detoxification of harmful substances, processing bloodborne nutrients, storage of vitamins, and production of plasma proteins.

Cirrhosis is a chronic liver disease characterized by scar tissue replacing healthy liver tissue. It can be caused by chronic hepatitis, alcoholism, or other factors.