UNIT5 YIPPEE

Alimentary Canal

aka gastrointestinal tract; tubular part of the digestive tract from the mouth to the anus; includes the mouth, pharynx, esophagus, stomach, small intestine, and large intestine

Bolus

Food that has been chewed and mixed with saliva, forming a mass rolled by the tongue.

Duodenum

The part of the small intestine where most chemical digestion occurs; it receives chyme, gastric juices, enzymes from the pancreas, and bile.

Feces

Non-digested food, also known as waste or stool.

Ileum

where important vitamins like vitamins A, B12, E, D, and K are absorbed; has the ileocecal valve at the end that connects to the large intestine

Ingestion

The act of eating, which occurs only in the mouth.

Intestinal villi

Small projections that maximize surface area for nutrient absorption into the blood.

Jejunum

The part of the small intestine where most nutrient absorption takes place.

Lumen

passageway; allows for the passage of digested food; the opening inside a tubular body structure that is lined by body tissue known as an epithelial membrane

Mesentery

 a sheet of two serous membranes fused back to back that provides routes for blood vessels, nerves, and lymphatic vessels to the small intestines. This structure also holds the organs in place and stores fat

Mucosa

The innermost layer of the alimentary canal.

Muscularis

The middle layer of smooth muscle in the alimentary canal critical for peristalsis.

Peristalsis

Rhythmic waves of muscular contraction in the walls of certain tubular organs that move food through the GI tract.

Propulsion

The movement of food through the gastrointestinal tract, primarily via peristalsis.

Pyloric sphincter

The valve located at the bottom of the stomach, controlling the passage of chyme into the duodenum;gatekeeper.

Serosa

The outer covering of the alimentary canal that contains nerves, blood vessels, and lymphatic vessels.

Submucosa

The layer of the alimentary canal beneath the mucosa that provides elasticity to the tube.

Function of Digestive System

To convert food into energy and the raw materials needed for body functions.

Accessory structures

Teeth, tongue, salivary glands, gallbladder, liver, and pancreas that aid in digestion but do not directly process food.

Chemical digestion

secreted enzymes chemically break down food molecules into their simplest form (monomers) so that they can be absorbed into the blood, transported, and used by our cells

Absorption

the transport of the end result of our digested food through the walls of the GI tract and into the blood (or lymph) to be transported

Defecation

The elimination of indigestible substances through the anus as feces, which occurs in the large intestine; absorption of nutrients is over, but H2O absorption continues

Stratified squamous epithelial cells

Cells in the mouth, esophagus, and anus that protect against abrasive foods.

Simple columnar epithelial cells

Cells in the stomach and intestines that facilitate absorption and secretion.

Amylase

An enzyme found in saliva that digests starches to create the disaccharide maltose.

Pepsin

An enzyme in gastric juice that digests proteins, activated by HCl. Produces partially digested proteins.

Proteases, lipases, and amylases

Enzymes in pancreatic juice that digest proteins, fats (in bile), and starches. Produces peptides, amino acids, fatty acids, glycerol, and maltose.

Peptidases, sucrase, lactase, and maltase

Intestinal enzymes that digest peptides, sucrose, lactose, and maltose. Produces amino acids, glucose, fructose, and galactose.

Bile salts

Substances found in liver bile that help digest fats. Produce fat droplets.

Enteric nervous system

The nerve supply specific to the GI tract that regulates digestive activities.

Vagus nerve

The nerve that allows communication between the enteric nervous system and the central nervous system.

Gastrin

A hormone produced by G cells that stimulates gastric fluid secretion.

Serotonin and Histamine

Substances that increase the release of HCl and stimulate muscle contractions in the gastrointestinal tract/stomach.

Cephalic Phase

First phase of the gastric fluid secretion; The 'reflex' phase in the brain that prepares the stomach for food intake before it enters; external stimuli trigger parasympathetic fibers in the vagus nerve to prep stomach for incoming food.

Gastric Phase

Second phase of the gastric fluid secretion;The phase in the stomach where mechanical and chemical stimuli trigger gastric fluid, gastrin, and HCl secretion.

Intestinal Phase

Third phase of the gastric fluid secretion;The phase in the intestines where chyme is received by the receptors in the duodenum; intestinal cells secrete further gastrin secretion.