Nutrition & Digestion Lecture Notes

Comprehensive vocabulary review flashcards covering comparative digestive anatomy, histology, digestive secretions, nutrient categories, and feeding strategies.

Nutrition

The acquisition and processing of food substances by organisms for growth, maintenance, and cellular energy production.

Digestion

The mechanical and chemical breakdown of ingested food into simpler, absorbable chemical substances that can be utilized by body cells.

Autotrophs

Organisms that synthesize their own organic food molecules from inorganic substances, exemplified by green plants and photosynthetic protists.

Heterotrophs

Organisms that cannot manufacture their own organic nutrients and must consume other organisms, exemplified by animals, fungi, and bacteria.

Herbivorous

Characterizing animals whose nutritional intake is derived entirely or primarily from plant tissues.

Carnivorous

Characterizing animals whose nutritional intake is derived entirely or primarily from the flesh or meat of other animals.

Omnivorous

Characterizing animals that routinely consume and derive nourishment from both plant and animal matter.

Macronutrients

Major nutrient classes required by the body in large quantities, specifically carbohydrates ($\text{CHO}$), lipids, and proteins.

Function of Macronutrients

Nutrients utilized by the organism for energy production or as structural sources for the essential "building blocks" of life.

Carbohydrates ($\text{CHO}$)

A primary class of macronutrients needed in large quantities, serving as a principal source of metabolic energy and structural cellular components.

Lipids

A class of macronutrients required in large quantities, used for long-term energy storage, cellular membrane structure, and vital building blocks.

Proteins

Macronutrients composed of amino acids required in large quantities to build and maintain body tissues, cellular structures, and enzymes.

Micronutrients

Essential dietary nutrients needed in small quantities, categorized into organic vitamins and inorganic minerals.

Vitamins

Organic micronutrients needed in small quantities that function primarily in enzymatic reactions as coenzymes or regulatory factors.

Minerals

Inorganic micronutrients required in trace quantities that participate in enzymatic reactions or form functional parts of certain proteins.

Ingestion

The physiological process of taking food, liquids, or nutrients into the digestive tract through the mouth.

Peristalsis

Coordinated, involuntary muscular contractions and relaxations of the alimentary tract wall that propel food forward through the digestive system.

Secretion

The release of digestive juices, enzymes, acids, buffers, and lubricating mucus by glandular tissues into the lumen of the digestive tract.

Absorption

The transport of digested nutrient molecules, water, and electrolytes across the epithelial lining of the digestive tract into the blood or lymph.

Defecation

The elimination of undigested residues, metabolic wastes, and fecal matter from the digestive tract through the anus or cloaca.

Digestive Tract

The continuous hollow muscular tube extending from the mouth to the anus or cloaca through which food passes and is processed.

Digestive Glands

Specialized secretory organs and tissues (including salivary glands, gastric glands, the pancreas, and liver) that produce digestive fluids.

Accessory Organs

Organs and structures (such as teeth, tongue, salivary glands, liver, gallbladder, and pancreas) that assist in mechanical or chemical digestion.

Mouth

The initial entry opening of the digestive tract where ingestion, mechanical mastication, and initial chemical digestion occur.

Lips

External fleshy muscular folds that surround the orifice of the mouth and aid in food grasping, manipulation, and oral sealing.

Vestibule

The narrow outer space within the oral cavity bounded externally by the lips and cheeks and internally by the teeth and gums.

Buccal / Oral Cavity

The primary inner oral chamber bounded by the palate, tongue, cheeks, and dental arches where mastication and insalivation take place.

Pharynx

The common muscular passageway connecting the oral and nasal cavities to the esophagus and larynx, subdivided into three regions.

Nasopharynx

The uppermost region of the pharynx located directly posterior to the nasal cavity and superior to the soft palate.

Oropharynx

The middle section of the pharynx lying posterior to the oral cavity, extending from the soft palate to the epiglottis.

Laryngopharynx (Hypopharynx)

The inferior segment of the pharynx positioned below the hyoid bone, opening anteriorly into the larynx and posteriorly into the esophagus.

Tonsils

Aggregations of lymphoid tissue situated along the pharynx that provide immune defense against ingested or inhaled pathogens.

Eustachian Tube

The auditory tube that connects the middle ear cavity to the nasopharynx to equalize atmospheric pressure.

Glottis

The vocal apparatus of the larynx, comprising the true vocal cords and the slit-like opening between them.

Posterior Nares

The internal nasal openings (choanae) through which the nasal cavities communicate directly with the nasopharynx.

Opening of the Esophagus

The anatomical gateway at the lower end of the laryngopharynx through which swallowed food passes into the esophagus.

Esophagus (Oesophagus)

A hollow, muscular tube that conveys the food bolus from the pharynx downward to the stomach by peristaltic contractions.

Bolus

A lubricated, rounded mass of chewed food mixed with saliva prepared for swallowing and transport down the esophagus.

Peristaltic Wave

A continuous, synchronized wave of muscular constriction and dilation along the digestive tract that propels ingested contents forward.

Incisors

Chisel-shaped anterior teeth adapted for cutting and shearing food; adult humans possess a total of $8$ ($4$ upper, $4$ lower).

Canines

Pointed, conical teeth specialized for piercing, tearing, and holding food; adult humans possess a total of $4$ ($2$ upper, $2$ lower).

Premolars

Bicuspid teeth positioned between canines and molars adapted for crushing and shearing food; adult humans possess a total of $8$ ($4$ upper, $4$ lower).

Molars

Broad posterior teeth with multi-cusped surfaces specialized for grinding and pulverizing food; adult humans possess a total of $12$ ($6$ upper, $6$ lower).

Adult Human Dentition Formula

The complete adult human dentition consisting of $32$ teeth: $8$ incisors, $4$ canines, $8$ premolars, and $12$ molars.

Temporary Teeth

The primary or deciduous dentition ("milk teeth") that erupt during infancy and are later replaced by permanent adult teeth.

Permanent Teeth

The secondary, lifelong dentition consisting of $32$ teeth that replaces the deciduous set in humans.

Tongue

A mobile muscular accessory organ on the oral cavity floor that manipulates food, aids in swallowing, and contains gustatory receptors.

Root of the Tongue

The posterior, relatively fixed attachment region of the tongue connected to the hyoid bone and mandible.

Body of the Tongue

The main, mobile anterior two-thirds of the tongue composed of interlacing skeletal muscle fibers and covered by mucous membrane.

Tip of the Tongue

The pointed, freely movable anterior extremity of the tongue resting behind the incisor teeth.

Lingual Frenulum

A vertical fold of mucous membrane connecting the midline underside of the tongue to the floor of the buccal cavity.

Serous Glands

Exocrine glands of the oral area that secrete a thin, watery fluid containing digestive enzymes and proteins.

Mucous Glands

Exocrine glands in the oral mucosa that produce a thick, viscous, mucin-rich fluid for lubrication and surface protection.

Mixed Glands

Salivary glands containing both serous and mucous secretory cells that produce a combined watery and mucinous secretion.

Circumvallate Papillae

Large, dome-shaped papillae arranged in a V-shaped row at the back of the tongue dorsum, surrounded by circular trenches containing taste buds.

Foliate Papillae

Series of short vertical folds on the posterolateral margins of the tongue containing taste buds.

Fungiform Papillae

Mushroom-shaped vascular projections scattered over the dorsal surface and tip of the tongue that appear red and house taste buds.

Filiform Papillae

Small, conical, keratinized papillae covering the anterior two-thirds of the tongue dorsum that provide friction to manipulate food but lack taste buds.

Stomach

A muscular J-shaped digestive organ that stores food, secretes acid and enzymes, and mechanically churns food into semi-liquid chyme.

Cardiac Region (Stomach)

The small superior region of the stomach immediately surrounding the gastroesophageal entrance.

Fundus (Stomach)

The dome-shaped, superior-most portion of the stomach that bulges above and to the left of the cardiac opening.

Body of the Stomach

The large, central main portion of the stomach located between the fundus and the pyloric region.

Pyloric Region (Pylorus)

The funnel-shaped terminal region of the stomach that connects the stomach body to the duodenum.

Cardiac Sphincter

The circular smooth muscle ring at the gastroesophageal junction that prevents gastric contents from refluxing into the esophagus.

Pyloric Sphincter

A thickened band of circular smooth muscle that regulates the passage of chyme from the pylorus into the duodenum.

Gastroesophageal Opening

The anatomical aperture where the lower terminal esophagus enters the cardiac region of the stomach.

Greater Curvature

The longer, convex lateral and inferior border of the stomach extending from the cardiac notch to the pylorus.

Lesser Omentum

A double layer of peritoneum that extends from the lesser curvature of the stomach and initial duodenum to the liver.

Rugae

Prominent, longitudinal mucosal and submucosal folds in the stomach wall that flatten to allow organ distension during feeding.

Gastric Glands

Tubular glands embedded within the stomach mucosa that secrete gastric juice containing enzymes, acid, and protective mucus.

Parietal Cells

Specialized secretory cells in gastric glands that produce hydrochloric acid ($\text{HCl}$) and intrinsic factor.

Chief Cells

Enzymogenic cells situated in gastric glands that synthesize and secrete pepsinogen, the inactive precursor of pepsin.

Mucous Cells (Gastric Glands)

Epithelial cells in gastric glands that secrete an alkaline, viscous mucus that protects the stomach lining from acid and pepsin.

Gastric Juice

The highly acidic digestive fluid secreted by gastric glands, containing hydrochloric acid, pepsin, and mucus.

Chyme

The semi-fluid, acidic mass of partially digested food mixed with gastric secretions that passes from the stomach into the small intestine.

Longitudinal Muscle Layer (Stomach)

The outer smooth muscle layer of the stomach muscularis externa, oriented along the longitudinal axis of the organ.

Circular Muscle Layer (Stomach)

The middle layer of smooth muscle in the stomach muscularis externa, running circumferentially around the organ wall.

Oblique Muscle Layer (Stomach)

The innermost, diagonal smooth muscle layer of the stomach muscularis externa that facilitates multidirectional mechanical churning.

Small Intestine

The major section of the alimentary canal divided into the duodenum, jejunum, and ileum where chemical digestion and nutrient absorption are completed.

Duodenum

The initial, shortest segment of the small intestine that receives acidic chyme from the stomach along with bile and pancreatic juice.

Jejunum

The middle portion of the small intestine characterized by dense mucosal villi, where the vast majority of nutrient absorption takes place.

Ileum

The final and longest segment of the small intestine that terminates at the ileocecal junction, emptying into the large intestine.

Villi

Microscopic, finger-like mucosal projections lining the small intestine that immensely amplify the surface area available for absorption.

Microvilli

Minute projections on the apical surface of intestinal enterocytes that form the brush border to facilitate final nutrient uptake.

Lacteal

A specialized central lymphatic capillary located within an intestinal villus responsible for absorbing dietary fats and lipid-soluble substances.

Capillary Bed (Intestinal Villus)

The dense vascular network within an intestinal villus that absorbs water-soluble nutrients, including simple sugars and amino acids.

Hepatic Portal Vein

The major venous vessel that conveys nutrient-rich blood directly from the gastrointestinal capillary beds to the liver.

Large Intestine

The distal section of the alimentary canal consisting of the cecum, colon, rectum, and anal canal, primarily absorbing water and compacting feces.

Cecum

The blind pouch forming the proximal commencement of the large intestine, receiving chyme from the ileum.

Vermiform Appendix

A narrow, finger-like blind pouch containing lymphoid tissue that projects from the posteromedial wall of the cecum.

Ascending Colon

The initial segment of the colon that ascends superiorly along the right side of the abdominal cavity toward the liver.

Transverse Colon

The horizontal middle segment of the colon that crosses the abdomen from right to left beneath the stomach.

Descending Colon

The segment of the colon that travels inferiorly down the left side of the abdominal cavity toward the pelvis.

Sigmoid Colon

The S-shaped terminal segment of the colon that traverses the pelvic cavity to join the rectum.

Rectum

The straight terminal segment of the large intestine that stores compacted fecal matter prior to defecation.

Anus

The external terminal orifice of the digestive tract through which solid digestive waste (feces) is expelled.

Cloaca

A common terminal chamber in non-mammalian vertebrates (such as amphibians and birds) receiving digestive, urinary, and reproductive tracts.

Liver

A large accessory digestive gland that produces bile, processes and stores absorbed nutrients, and detoxifies metabolic substances.

Bile

A greenish-yellow alkaline fluid produced by hepatocytes that emulsifies dietary fats in the small intestine to assist lipase activity.

Gallbladder

A pear-shaped muscular sac situated beneath the liver that stores and concentrates bile between digestive periods.