Digestive System Lecture Flashcards

A comprehensive set of vocabulary flashcards covering the anatomy, physiology, and processes of the human digestive system as described in the lecture notes.

Digestive System

The organs and tissues that assist in breaking down food molecules that are too large to use into useable materials.

Ingestion

The process of bringing food into the body.

Mastication

The act of chewing.

Propulsion

The movement of food from one location to another, including swallowing and peristalsis.

Peristalsis

Wavelike contractions and relaxation of muscles in the wall of the GI tract that move food from one region to another; occurs in the esophagus, stomach, small intestine, and large intestine.

Mechanical Digestion

The physical breakdown of food from large-sized particles to smaller-sized particles.

Segmentation

Rhythmic, local contraction of the small intestine that mixes food with digestive enzymes and hormones; occurs only in the small intestines.

Chemical Digestion

The breakdown of food components at a molecular level.

Absorption

The process of bringing water and nutrients in from the external environment to the internal environment.

Secretion

The expulsion of hormones or digestive enzymes from accessory organs to the GI Tract.

Defecation

The elimination of food wastes from the body.

Alimentary Canal

A continuous tube from the mouth to the anus, approximately $30\,ft$ long, consisting of the oral cavity, pharynx, esophagus, stomach, small intestines, and large intestines.

Accessory Digestive Organs

Organs that provide mechanical and chemical mechanisms to aid in digestion, including teeth, tongue, salivary glands, liver, gallbladder, and pancreas.

Mucosa

The innermost layer of the alimentary canal which comes in direct contact with ingested items, secretes mucus, enzymes, and hormones, and absorbs nutrients.

Stratified Squamous Epithelium

The type of epithelial tissue found in the mouth, esophagus, and anus for protection.

Simple Columnar Epithelium

The type of epithelial tissue found in the stomach, small and large intestines, and rectum.

Lamina Propria

The sub-layer of the mucosa consisting of connective tissues, blood vessels, and lymphatic tissue.

Muscularis Mucosa

A thin layer of smooth muscle within the mucosa that contracts to improve absorption and secretion.

Submucosa

A layer of connective tissue housing blood vessels, nerves, lymphatic tissue, and glands; contains elastic fibers that allow structures to stretch and regain shape.

Muscularis Externa

The layer responsible for segmentation and peristalsis; typically consists of circular and longitudinal muscle layers.

Serosa

The outermost, thin layer of connective and epithelial tissue that secretes a slippery, watery fluid to lubricate the outer part of the digestive tract.

Stomach Muscularis Externa

A unique three-layer arrangement of muscle consisting of circular, longitudinal, and oblique layers.

Visceral Peritoneum

Membrane that covers the external surfaces of most abdominal digestive organs and secretes serous fluid for lubrication.

Parietal Peritoneum

Tissue that lines the abdominal body wall and secretes serous fluid.

Greater Omentum

A membrane that tethers or attaches the greater curvature of the stomach to the small intestines.

Lesser Omentum

A membrane that tethers or attaches the liver to the lesser curvature of the stomach.

Mesentery Proper

The membrane that suspends the small intestines from the posterior wall of the abdomen.

Mesocolon

The membrane that suspends the large intestines.

Enteric Nervous System (ENS)

The nervous system that controls smooth muscle contraction and GI secretions without constant brain involvement.

Autonomic Nervous System Regulation

The system where sympathetic nerves decrease GI secretions and motility, while parasympathetic nerves increase them.

Oral Cavity

Also known as the mouth; includes the lips, tongue, cheeks, palate, gingiva, teeth, uvula, and salivary glands.

Hard Palate

The bony anterior $\frac{2}{3}$ of the roof of the oral cavity.

Soft Palate

The muscular posterior $\frac{1}{3}$ of the roof of the oral cavity that moves upward during swallowing.

Bolus

A mass of partially digested material created by the tongue manipulating and mixing food.

Papillae

Small projections on the surface of the tongue that house the taste buds.

Uvula

A cone-shaped structure hanging from the soft palate that prevents food and fluids from entering the nasopharynx during swallowing.

Saliva

A watery fluid ($99\%$ water) that dissolves food molecules, lubricates the oral cavity, and inhibits bacterial growth; $1-1.5\,L$ is produced daily.

Lingual Lipase

An enzyme in the oral cavity that breaks down lipids.

Salivary Amylase

An enzyme in the oral cavity that breaks down starch.

Parotid Glands

The largest salivary glands, located in the cheek just anterior to the ear.

Submandibular Glands

Salivary glands located in the lower jaw region that produce the most saliva.

Sublingual Glands

Salivary glands located under the tongue.

Dentition

The collective term for teeth.

Crown

The exposed portion of a tooth covered with enamel.

Root

The portion of the tooth within the jaw bones containing the root canal, blood vessels, and nerves.

Deciduous Teeth

Also known as baby or milk teeth; consists of $20$ total teeth appearing between $6-30$ months.

Permanent Teeth

Adult teeth; consists of $32$ total teeth, including the third set known as wisdom teeth.

Adult Dental Formula

$2+1+2+3=8 \times 4 = 32$, representing $2$ incisors, $1$ canine, $2$ premolars, and $3$ molars per quadrant.

Pharynx

Commonly called the throat; connects the oral cavity to the esophagus and trachea, serving both digestive and respiratory systems.

Esophagus

A muscular tube approximately $25\,cm$ long in adults that carries a bolus from the mouth to the stomach.

Epiglottis

The structure acting as a 'trap door' ensuring food and liquids enter the digestive tract rather than the trachea.

Inferior Esophageal Sphinter

A sphincter at the junction of the esophagus and stomach that prevents backflow into the esophagus.

Chyme

A watery fluid produced by the stomach after mixing bolus with gastric secretions.

Rugae

Folds in the stomach that increase surface area for digestion.

Pylorus

The part of the stomach containing the sphincter that controls the movement of chyme into the small intestines.

Gastric Pits

Microscopic openings within the rugae that lead to stomach glands.

Parietal Cells

Stomach cells that secrete Hydrochloric Acid (HCl), Intrinsic Factor (for B12 absorption), and Ghrelin (hunger hormone).

Chief Cells

Stomach cells that secrete Gastric Lipase and Pepsinogen (the inactive form of pepsin).

Mucous Cells

Stomach cells that secrete mucus to protect the lining from hydrochloric acid.

Enteroendocrine Cells

Cells that produce and secrete Gastrin, a hormone regulating stomach secretions and motility.

Cephalic Phase

The first phase of stomach secretion, activated by the sight, smell, or thought of food.

Falciform Ligament

The ligament that attaches the liver to the anterior abdominal wall.

Bile

A substance produced by the liver that emulsifies lipids into small droplets.

Hepatic Portal Vein

The vessel that delivers deoxygenated, nutrient-rich blood from the digestive organs to the liver.

Portal Triad

A structure in each corner of a liver lobule consisting of a Hepatic Artery branch, Hepatic Portal Vein branch, and a Bile Duct.

Gallbladder

A pear-shaped sac that stores and concentrates bile until needed by the duodenum.

Pancreas

A sponge-like mixed gland behind the stomach with endocrine and exocrine functions; contains acinar and islet cells.

Trypsin and Chymotrypsin

Pancreatic enzymes responsible for breaking down proteins.

Duodenum

The first part of the small intestine, approximately $10\,inches$ long.

Jejunum

The middle region of the small intestine, approximately $7.5\,ft$ long.

Ileum

The final and longest portion of the small intestine ($11\,ft$), terminating at the ileocecal valve.

Circular Folds

Folds in the mucosa layer of the small intestine that increase surface area.

Villi

Finger-like projections in the small intestine covered with absorptive cells.

Microvilli

Long cytoplasmic extensions on mucosal cells that create a brush border.

Teniae Coli

Three muscular bands that run the length of the large intestines and help tone the walls.

Haustra

Pocket-like sacs of the large intestines created by the teniae coli.

Bacterial Flora

Bacteria in the large intestine that produce gas, produce vitamins, and digest plant fiber (cellulose).

Internal Anal Sphincter

An involuntary smooth muscle sphincter that opens when the rectum contracts.

External Anal Sphincter

Skeletal muscle that must be voluntarily relaxed for fecal matter to leave the body.

Diarrhea

Watery stool caused when water enters the large intestine faster than it can be reabsorbed.

Glycogen

The form in which glucose is mainly stored in the body after absorption.

Normal Blood Glucose Range

$80-110\,mg$.

Micelles

Small droplets formed when bile salts emulsify fatty acids and monoglycerides.

Lacteals

Lymphatic capillaries in the small intestine that absorb chylomicrons.