Digestive System part 1

Flashcards covering the general functions, organization, histology, and regulation of the digestive system, including the upper gastrointestinal tract and stomach.

Digestive System

A body system that provides the means to break down ingested nutrients, absorb them, and expel waste products.

Ingestion

The first step in the digestion process, involving the introduction of solid and liquid nutrients into the oral cavity.

Motility

Voluntary and involuntary muscular contractions used for mixing and moving materials through the gastrointestinal tract.

Secretion

The process of producing and releasing fluid products, such as digestive enzymes, acid, and bile, that facilitate digestion.

Mechanical Digestion

The physical breakdown of ingested material into smaller structures through processes like chewing and mixing.

Chemical Digestion

The use of specific enzymes to break chemical bonds and change large complex molecules into smaller molecules.

Absorption

The transport of digested molecules, electrolytes, vitamins, and water from the gastrointestinal tract into the blood or lymph.

Elimination

The expulsion of indigestible components from the body that are not absorbed.

Gastrointestinal (GI) Tract

A continuous tube consisting of the oral cavity, pharynx, esophagus, stomach, small intestine, large intestine, and anus.

Accessory Digestive Organs

Organs that assist in the breakdown of food, including the salivary glands, liver, pancreas, teeth, tongue, and gallbladder.

Mucosa

The innermost tunic of the gastrointestinal wall, consisting of an epithelium, a lamina propria of areolar tissue, and a thin layer of smooth muscle called the muscularis mucosae.

Submucosa

A layer of areolar and dense irregular connective tissue containing blood vessels, lymph vessels, nerves, and mucosa-associated lymphatic tissue (MALT).

Peyer Patches

Larger aggregates of lymphatic nodules located in the distal small intestine.

Muscularis

A tunic generally composed of an inner circular layer and an outer longitudinal layer of smooth muscle responsible for motility.

Peristalsis

The alternating contraction sequence of the inner and outer muscularis layers that propels materials through the gastrointestinal tract.

Adventitia

The outermost tunic of the gastrointestinal wall composed of areolar connective tissue, found on organs outside the peritoneal cavity.

Serosa

The outermost tunic of the gastrointestinal wall for organs within the peritoneal cavity, composed of areolar connective tissue covered by visceral peritoneum.

Parietal Peritoneum

The serous membrane that lines the inside surface of the abdominal wall.

Visceral Peritoneum

The serous membrane that reflects over and covers the surface of internal abdominal organs.

Intraperitoneal Organs

Organs completely surrounded by visceral peritoneum, such as the stomach and most of the small intestine.

Retroperitoneal Organs

Organs lying directly against the posterior abdominal wall with only their anterolateral portions covered by peritoneum, including the pancreas and rectum.

Mesentery

A double layer of peritoneum that supports, suspends, and stabilizes intraperitoneal gastrointestinal tract organs.

Greater Omentum

A mesentery extending from the stomach that covers most abdominal organs and accumulates large amounts of adipose tissue, often called a 'fatty apron'.

Falciform Ligament

A flat, crescent-shaped fold of peritoneum that attaches the liver to the internal surface of the anterior abdominal wall.

Baroreceptors

Sensory receptors that detect stretch or pressure within the gastrointestinal tract wall as contents move through.

Chemoreceptors

Sensory receptors that detect specific chemical substances within the lumen of the gastrointestinal tract.

Short Reflexes

Local digestive reflexes that occur only within the neurons and do not involve the Central Nervous System.

Long Reflexes

Digestive reflexes involving autonomic motor output relayed through the facial, glossopharyngeal, and vagus nerves to effectors like the pancreas.

Bolus

A mass of ingested material and saliva formed in the oral cavity during the voluntary phase of swallowing.

Salivary Amylase

An enzyme secreted by salivary glands that initiates the chemical digestion of starch.

Parotid Salivary Glands

The largest salivary glands, located anterior and inferior to the ear, which produce $25\%$ to $30\%$ of all saliva.

Mucous Cells

Secretory cells in salivary glands and the stomach that produce mucin, which forms mucus upon hydration.

Serous Cells

Secretory cells in salivary glands that produce a watery fluid containing electrolytes and salivary amylase.

Mastication

The process of chewing

Enamel

Hardest substance in the body, composed of calcium phosphate crystals, which forms the external surface of the tooth crown.

Deglutition

The medical term for swallowing, the process of moving ingested materials from the oral cavity to the stomach.

Pharyngeal Phase

The involuntary phase of swallowing where the soft palate and uvula elevate to block the nasopharynx and the larynx elevates to move the epiglottis over the laryngeal opening.

Chyme

A semidigested liquid formed in the stomach by mixing the bolus with gastric secretions.

Cardia

The small, superior entryway into the stomach lumen from the esophagus.

Rugae

Gastric folds found on the internal stomach lining that allow the stomach to expand significantly when filled with food.

Parietal Cells

Stomach cells that secrete intrinsic factor, required for Vitamin B12 absorption, and hydrochloric acid ($HCl$).

$$HCl$$

Hydrochloric acid, which is responsible for the low pH of the stomach and functions to activate pepsinogen into pepsin.

Chief Cells

The most numerous secretory cells in the gastric glands, which produce pepsinogen and gastric lipase.

Pepsinogen

The inactive precursor to the enzyme pepsin, which chemically digests denatured proteins into oligopeptides.

G-cells

Enteroendocrine cells in the stomach that secrete the hormone gastrin into the blood.

Gastrin

A hormone that stimulates stomach secretions and motility while also stimulating the contraction of the pyloric sphincter.

Cephalic Phase

The phase of stomach regulation initiated by the thought or sensation of food, resulting in increased vagal stimulation.

Gastric Phase

The phase of stomach regulation following the arrival of a bolus, triggered by baroreceptors detecting stretch and chemoreceptors detecting protein or increased pH.

Intestinal Phase

The phase of stomach regulation following the arrival of chyme in the small intestine, which involves the intestinal reflex to decrease stomach motility.

fats break down to

fatty acids and glyercol

Simple Columnar Epithelium

Found in the stomach and intestines, it is responsible for secretion and absorption.

Stratified Squamous Epithelium

Found in the oral cavity and esophagus, it provides protection against abrasion.

Pathway Through the GI Tract

The journey of food from the mouth to the anus: mouth → pharynx → esophagus → stomach → small intestine → large intestine → anus.

Superior Esophageal Sphincter

A muscular ring located at the top of the esophagus that controls the entry of food from the pharynx into the esophagus.

Inferior Esophageal Sphincter

A muscular ring at the bottom of the esophagus that prevents stomach contents from flowing back into the esophagus.

what does the stomach mainly digest?

proteins