ASCI 220 - Introductory Animal Nutrition and Feeding: Digestive System Anatomy

These flashcards cover the anatomy of the digestive system, including tissue types, headgut structures (teeth, tongue, salivary glands), foregut variations (mammalian and avian stomachs), and the microanatomy of the small and large intestines.

Prehension

The process of seizing and conveying food to the mouth.

Deglutition

The act of swallowing.

Mastication

The mechanical processing of food by chewing.

Alimentary tract

A tube or lumen space of variable dimensions lined by epithelia, serving as a control area outside the body for digestion and absorption.

Headgut

The major subdivision of the digestive system comprising the oral cavity and pharynx.

Foregut

The major subdivision of the digestive system comprising the esophagus and stomach.

Midgut

The major subdivision of the digestive system comprising the small intestine.

Hindgut

The major subdivision of the digestive system comprising the large intestine, cecum (ceca), rectum, and cloaca.

Stratified Squamous Epithelium

Tissue that provides physical protection against abrasion, pathogens, and chemical attack; located in the skin surface, mouth, throat, esophagus, rectum, anus, and vagina.

Simple Columnar Epithelium

Tissue responsible for protection, secretion, and absorption; located in the lining of the stomach, intestine, gallbladder, uterine tubes, and kidney collecting ducts.

Skeletal Muscle Tissue

Long, cylindrical, striated, and multinucleate cells that move or stabilize the skeleton and guard entrances and exits to the digestive, respiratory, and urinary tracts.

Smooth Muscle Tissue

Short, spindle-shaped, nonstriated cells with a single, central nucleus that move food, urine, and secretions, and regulate the diameter of blood vessels.

Rhamphotheca

The overlying keratinous layer of the avian bill.

Homodont

Teeth that are all of the same form, typically found in nonmammalian vertebrates.

Heterodont

Teeth differentiated into different forms, including incisors, canines, premolars, and molars, typically found in mammals.

Acrodont

Teeth attached either at the outer surface or the summit of the jaw bone.

Pleurodont

Teeth attached to the inner surface of the jaw bone.

Thecodont

Teeth that occupy alveoli (sockets) within the jaw bone.

Dental Formula

A notation indicating the numbers of each tooth type (I, C, P, M) on one side of the upper and lower jaw.

Deciduous Teeth

Also known as primary or milk teeth, these are the first set of teeth in young mammals.

Temporalis

A muscle of the jaw responsible for elevation and retraction.

Masseter

A muscle of the jaw responsible for elevation and protrusion.

Zygomatic Gland

A salivary gland found only in carnivores.

Parotid Salivary Glands

Glands that produce a serous secretion containing the enzyme salivary amylase to break down starches.

Sublingual Salivary Glands

Glands that produce a mucous secretion acting as a buffer and lubricant.

Ruminant saliva

Produced continuously (up to $12\,gal/d$ in cattle), it contains urea and sodium bicarbonate but no amylase.

Lysozyme

An enzyme in saliva with antiseptic properties.

Peristalsis

The wave of muscular contraction and relaxation that moves material forward through the digestive tract.

Crop

An avian enlargement of the esophagus used for temporary food storage; in some species like the Hoatzin, it serves as a fermentation organ.

Pigeon Milk

Discrete rice-shaped pellets produced by the mucosal surface of the lactating crop in pigeons.

Proventriculus

The avian gastric stomach that secretes $HCl$ and pepsin.

Ventriculus

Also known as the gizzard, this muscular avian stomach is responsible for maceration and trituration.

Koilin

A substance in the avian stomach that acts as a grinding surface and protects the underlying mucosa from acid and pepsin.

Chief Cells

Gastric cells that secrete pepsinogen and, in the cardiac region, minor amounts of gastric lipase.

Parietal Cells

Gastric cells that produce hydrochloric acid ($HCl$) and intrinsic factor.

Pepsinogen

An inactive proteolytic enzyme (zymogen) that is converted to active pepsin by $HCl$ at a low $pH$.

Intrinsic Factor

A glycoprotein produced in the stomach required for the absorption of vitamin $B_{12}$ in the small intestine.

Rennin

A proteolytic enzyme produced only in young mammals that coagulates milk to reduce the rate of passage.

Gastrin

A hormone released from G cells in the pyloric region that stimulates $HCl$ and pepsinogen secretion and gastric motility.

Chyme

The resulting stomach contents consisting of ingesta mixed with $HCl$ and digestive enzymes at an acidic $pH$.

Unilocular Stomach

A simple, single-chambered stomach.

Plurilocular Stomach

A stomach with a lumen subdivided into two or more chambers.

Margo Plicatus

The internal line in the horse stomach that separates the non-glandular stratified squamous epithelium from the glandular mucosa.

Reticulorumen

The combined forestomach compartment (reticulum and rumen) in ruminants lined with stratified squamous epithelium.

Omasum

A ruminant stomach compartment responsible for the absorption of water, sodium, potassium, and $40-60\%$ of volatile fatty acids (VFA).

Abomasum

The glandular 'true' stomach of the ruminant where autoenzymatic digestion occurs.

Plicae circulares

Large circular mucosal folds in the small intestine that increase surface area.

Villi

Multicellular mucosal projections into the intestinal lumen that increase surface area for absorption.

Microvilli

Microscopic projections of the apical surface of epithelial cells (the brush border) that increase surface area.

Enterocytes

Intestinal epithelial cells responsible for nutrient absorption and the production of specific enzymes.

Goblet Cells

Cells found in the intestinal epithelium and respiratory tract that secrete mucus.

Paneth Cells

Cells located in the intestinal crypts that are involved in the innate immune response.

Bile

A liver-produced secretion stored in the gallbladder (if present) that emulsifies lipids using glycocholic and taurocholic salts.

Succus entericus

A general term for 'intestinal juice'.

Brunner’s Glands

Submucosal glands in the duodenum that secrete a mucus-rich alkaline fluid to protect against acidic chyme.

Coprodeum

The most anterior subdivision of the avian cloaca receiving material from the rectum.

Urodeum

The middle subdivision of the avian cloaca where the ureters and genital ducts empty.

Proctodeum

The most posterior subdivision of the avian cloaca, opening to the vent.