Human Digestive System Anatomy and Physiology

Comprehensive practice flashcards covering the human digestive system, including the alimentary canal, accessory glands, oral anatomy, gastric physiology, and intestinal processing.

Ingestion

The physiological process of taking food into the body.

Digestion

The process of breaking down food into molecules small enough for the body to absorb.

Absorption

The process by which digested food is transferred to the bloodstream.

Elimination

The process of removing metabolic and digestive wastes to the outside of the body.

Alimentary Canal

A continuous muscular tube about $9\text{ meters}$ long that begins at the mouth and terminates at the anus, passing through the body's ventral cavity.

Ventral Cavity

The body cavity traversed by the $9\text{-meter}$ long muscular tube of the alimentary canal.

Accessory Organs

Organs that are necessary for the digestive process but do not form part of the continuous alimentary canal.

Mouth

The first portion of the alimentary canal, functioning to receive food, mechanically reduce particle size via mastication, and serve as an organ of speech and sensory reception.

Mastication

The mechanical reduction of the size of solid food particles and their mixing with saliva inside the mouth.

Oral Cavity

The interior chamber of the mouth located specifically between the palate and the tongue.

Vestibule

The narrow anatomical space within the mouth located between the teeth, cheeks, and lips.

Cheeks

Structures that form the lateral walls of the mouth, consisting of outer skin, pads of cutaneous fat, muscles of expression and chewing, and an inner lining of moist stratified squamous epithelium.

Cutaneous Fat Pads

Fat pads located within the cheeks that contribute to the structure of the lateral mouth walls.

Stratified Squamous Epithelium

The moist epithelial tissue forming the inner lining of the cheeks.

Lips

Structures surrounding the mouth opening that contain skeletal muscles and sensory receptors useful in judging the temperature and texture of food.

Reddish Color of the Lips

The visual hue of the lips caused by an abundance of blood vessels located near their surfaces.

External Borders of the Lips

The anatomical markings that delineate the boundary between the skin of the face and the mucous membrane lining the alimentary canal.

Tongue

A thick, muscular organ covered by mucous membrane occupying the floor of the mouth that mixes food with saliva and directs it toward the pharynx.

Frenulum

A membranous fold that connects the tongue in the midline to the floor of the mouth.

Functions of the Tongue

Aiding in mixing food particles with saliva during chewing and moving food toward the pharynx during swallowing.

Papillae

Rough projections on the surface of the tongue that provide friction for handling food and contain taste buds.

Taste Buds

Sensory structures housed within the papillae on the surface of the tongue.

Palate

The roof of the oral cavity, consisting of a hard anterior part and a soft posterior part.

Hard Palate

The rigid anterior roof of the mouth formed by the palatine processes of the maxillary bones in front and the horizontal portions of the palatine bones in back.

Palatine Processes of the Maxillary Bones

The anterior bony plates that form the front section of the hard palate.

Horizontal Portions of the Palatine Bones

The posterior bony plates that form the back section of the hard palate.

Soft Palate

The muscular arch forming the posterior roof of the oral cavity that extends posteriorly and downward into the uvula.

Uvula

A cone-shaped muscular projection that extends posteriorly and downward from the soft palate.

Swallowing Action of the Soft Palate and Uvula

Muscular drawing upward of the soft palate and uvula during swallowing, which closes the opening between the nasal cavity and the pharynx to prevent food entry into the nasal cavity.

Palatine Tonsils

Lymphoid structures situated at the back of the mouth on either side of the tongue that help protect the body against infections.

Pharyngeal Tonsils (Adenoids)

Lymphoid tissue aggregates located on the posterior wall of the pharynx, above the border of the soft palate.

Teeth

Hard structures developing in sockets within the alveolar processes of the mandibular and maxillary bones that break food into smaller pieces.

Alveolar Process

The bony ridge and socket region of the mandibular and maxillary bones in which teeth develop.

Gingiva

The gum tissue through which primary and secondary teeth erupt.

Primary Teeth (Deciduous Teeth)

The initial set of $20$ teeth ($10$ in each jaw) that typically erupt between the ages of $6\text{ months}$ and $2\text{ to }4\text{ years}$.

Primary Teeth Eruption Window

The developmental time interval between $6\text{ months}$ and $2\text{ to }4\text{ years}$ of age during which deciduous teeth erupt through the gums.

Deciduous Teeth Series

The arrangement of the $10$ primary teeth per jaw from the midline toward the sides: central incisor, lateral incisor, cuspid (canine), first molar, and second molar.

Secondary Teeth (Permanent Teeth)

The adult set of $32$ teeth that replace deciduous teeth.

Permanent Teeth Series

The arrangement of secondary teeth from the midline toward the sides: central incisor, lateral incisor, cuspid (canine), first bicuspid (premolar), second bicuspid, first molar, second molar, and third molar.

Crown

The portion of a tooth that projects beyond the gum and is covered by glossy white enamel.

Enamel

The glossy white covering of the crown composed of calcium salts, recognized as the hardest substance in the human body.

Root

The portion of the tooth that is anchored to the alveolar process of the jaw.

Dentin

The bulk substance of the tooth lying beneath the enamel and surrounding the central pulp cavity.

Pulp Cavity

The central internal chamber of a tooth enclosed by dentin.

Incisors

Two chisel-shaped teeth per quadrant specialized for biting food.

Canine (Cuspid)

A pointed tooth specialized for tearing food, with one present per quadrant.

Premolars (Bicuspids)

Two fairly flat teeth per quadrant specialized for grinding food.

Molars

Three broad teeth per quadrant specialized for crushing food.

Saliva

A fluid secreted by salivary glands that moistens food, binds particles, initiates carbohydrate digestion, acts as a solvent for tasting, cleanses oral tissues, and coats food with mucus.

Deglutition

The physiological process of swallowing.

Parotid Glands

Major salivary glands located in front of and somewhat below the ears, situated between the skin of the cheeks and the masseter muscles.

Parotid Secretion

A clear, watery serous fluid rich in the digestive enzyme amylase.

Submandibular Glands

Major salivary glands located in the floor of the mouth on the inside surface of the mandible.

Submandibular Secretion

A salivary secretion composed primarily of serous fluid with some mucus that is more viscous than parotid secretion.

Sublingual Glands

Major salivary glands situated in the floor of the mouth beneath the tongue.

Sublingual Secretion

A thick, stringy mucus secretion produced by glands under the tongue.

Salivary Amylase

A salivary enzyme that initiates the chemical digestion of starch into maltose.

Salivary Amylase Reaction

The chemical reaction represented by $\text{Starch} + \text{H}_2\text{O} \xrightarrow{\text{Salivary amylase}} \text{Maltose}$.

Pharynx

The muscular throat region where the digestive and respiratory systems diverge.

Divergence in the Pharynx

The anatomical branch-point where the digestive pathway separates from the respiratory tract.

Tracheal Reflex

A coordinated set of swallowing reflexes that closes the opening into the trachea to prevent food aspiration.

Esophagus

A tubular structure approximately $9\text{ inches}$ long that receives food from the contracting pharynx and propels it to the stomach.

Peristalsis

A rhythmic, wavelike motion of muscle tissue that forces contents through the alimentary tract.

Stomach

A muscular organ that stores up to $2\text{ liters}$ or more of partially digested food while contracting vigorously to mix it with digestive juices.

Stomach Storage Capacity

The volume of partially digested food the stomach can hold, amounting to up to $2\text{ liters}$ or even more.

Gastric Juice

A secretion produced when food enters the stomach containing Hydrochloric Acid ($\text{HCl}$) and the enzyme pepsin.

Hydrochloric Acid ($\text{HCl}$)

A substance secreted by the stomach with high acidity sufficient to kill bacteria, soften meat connective tissue, and activate gastric enzymes.

Meat Connective Tissue Softening

A major digestive function of stomach $\text{HCl}$ that softens connective fibers in meat.

Antibacterial Action of Gastric $\text{HCl}$

The destruction of bacteria and potential disease-producing agents in food caused by the high acidity of stomach secretions.

Enzyme Activation by Gastric $\text{HCl}$

The chemical activation of at least one stomach enzyme mediated by secreted hydrochloric acid.

Pepsin

A hydrolytic enzyme in gastric juice that acts on proteins to produce peptides.

Pepsin Reaction

The digestive reaction represented by $\text{Protein} + \text{H}_2\text{O} \xrightarrow{\text{Pepsin}} \text{Peptide}$.

Chyme

A thick, soup-consistency mixture of ingested food and gastric juice formed within the stomach.

Cardiac Valve

The muscular valve located between the esophagus and the stomach.

Pyloric Sphincter

A muscular ring located at the base or end of the stomach controlling the narrow opening into the duodenum.

Duodenal Chyme Reflex

A neural reflex triggered when chyme enters the duodenum that causes the sphincter muscle to contract vigorously and temporarily close.

Stomach Mucus Layer

A thick protective mucus barrier lining the stomach wall and first part of the duodenum that prevents self-digestion by pepsin and acid.

Ulcer

An open sore in the gastrointestinal wall caused by the gradual disintegration of tissues when pepsin digests the lining.

Nervous Stimulation Cause of Ulcers

The most frequent cause of an ulcer, identified as the oversecretion of gastric juice due to excessive nervous stimulation.

Small Intestine

The chief organ of absorption in the digestive system, measuring $4\text{ to }7\text{ meters}$ in length.

Small Intestine Length

The total physical dimension of the human small intestine, spanning $4\text{ to }7\text{ meters}$.

Ridges and Furrows

Corrugated anatomical folds on the inner surface of the small intestine that increase surface area.

Villi

Small, fingerlike projections located on the surface of the ridges and furrows of the small intestine.

Microvilli

Minute projections present on the surface of epithelial cells covering the intestinal villi.

Effective Surface Area Expansion

The substantial increase in intestinal absorptive capacity achieved through the structural contributions of villi and microvilli.

Duodenal Chyme Digestive State

The digestive state upon entering the duodenum where proteins and carbohydrates are only partly digested, and fat digestion has not yet begun.

Duodenum

The first segment of the small intestine, measuring $10\text{ to }12\text{ inches}$ in length, where food and enzymes mix with digestive juices from the pancreas, gallbladder, and intestinal glands.

Duodenum Length

The physical measurement of the initial section of the small intestine, spanning $10\text{ to }12\text{ inches}$.

Jejunum

The middle portion of the small intestine that forms the next $2/5$ of its length and constitutes its most coiled part.

Coiled Structure of the Jejunum

The characteristic morphological state of the jejunum being the most coiled portion of the small intestine.

Ileum

The final segment of the small intestine that attaches to the large intestine.

Ileocecal Valve

The valve through which the ileum joins the large intestine.

Liver

An accessory digestive gland that produces bile, which is routed to the gallbladder and duodenum.

Gallbladder

The accessory organ that stores bile produced by the liver before dispatching it to the duodenum via a duct.

Bile

A greenish digestive secretion manufactured by the liver containing bile salts and hemoglobin breakdown pigments.

Green Pigmentation of Bile

The green visual appearance of bile resulting from pigments produced during hemoglobin breakdown.

Bile Salts

Emulsifying agents in bile that physically break up large fat masses into smaller fat droplets.

Emulsification

The physical process in which fat is broken apart and caused to mix with water, making it more easily acted on by enzymes.

Bile Salts Emulsification Reaction

The physical transformation represented by $\text{Fat} \xrightarrow{\text{Bile Salts}} \text{Fat Droplets}$.

Pancreas

An accessory gland operating as an endocrine gland by secreting insulin into blood and an exocrine gland by secreting pancreatic juice into the duodenum.