Animal Digestive Systems and Nutrient Absorption

Electrolytes

Ions ingested by animals for physiological functions.

Vitamins

Organic compounds acting as co-enzymes in metabolism.

Capturing Food

Process of acquiring nutrients from various sources.

Simple Absorption

Nutrient uptake without a digestive tract, seen in tapeworms.

Tapeworms

Parasites that absorb nutrients through body wall cells.

Phagocytosis

Cellular process of engulfing food particles in vacuoles.

Food Vacuoles

Membrane-bound vesicles containing ingested food in cells.

Intracellular Digestion

Digestion occurring within a cell's food vacuole.

Choanocytes

Flagellated cells in sponges that facilitate feeding.

Extracellular Digestion

Digestion occurring outside cells in a digestive system.

Luminal Epithelium

Epithelial cells lining the digestive tube's lumen.

Incomplete Digestive System

Single opening serves as mouth and anus.

Gastrovascular Cavity

Body cavity in some animals for digestion and circulation.

Cnidarians

Group including Hydra with incomplete digestive systems.

Complete Digestive System

Separate mouth and anus for continuous digestion.

One-Way Flow

Food moves unidirectionally through the digestive tract.

Roundworms

Animals with simple complete digestive systems.

Earthworms

Complex digestive systems with specialized structures.

Crop

Food storage organ in earthworm's digestive tract.

Gizzard

Muscular chamber in earthworms for food breakdown.

Typhlosole

Fold in intestine increasing surface area for absorption.

Digestive Glands

Glands secreting enzymes into the digestive lumen.

Salivary Glands

Glands in insects aiding in digestion.

Digestive Glands

Glands aiding digestion, varying by invertebrate group.

Salivary Glands

Glands producing saliva for lubrication and digestion.

Homodont Dentition

Teeth with similar shape and function in vertebrates.

Heterodont Dentition

Teeth differing in structure and function among vertebrates.

Diphyodont

Species with two sets of teeth: milk and permanent.

Polyphyodont

Species regularly losing and replacing teeth.

Monophyodont

Species with only one set of teeth.

Salivary Amylase

Enzyme in saliva that digests starch into disaccharides.

Lingual Lipase

Enzyme initiating fat breakdown in the mouth.

Pharynx

Region where respiratory and digestive systems intersect.

Epiglottis

Cartilage blocking larynx during swallowing.

Uvula

Fleshy extension preventing food from entering nasal passages.

Esophagus

Tube transporting food to the stomach.

Mucosa

Innermost layer of tubular organs, contains epithelium.

Submucosa

Connective tissue layer supporting blood vessels and nerves.

Muscularis Externa

Smooth muscle layer propelling food via peristalsis.

Peristalsis

Waves of contraction moving food through digestive tract.

Teeth Function

Teeth adapted for grabbing, holding, and grinding food.

Cheek Teeth

Teeth associated with grinding function in mammals.

Venom Glands

Modified salivary glands in snakes and some mammals.

Oral Cavity

Initial site of digestion, bordered by lips and teeth.

Digestive Enzymes

Biological catalysts aiding in food breakdown.

Intestinal Organs

Includes stomach, small intestine, and large intestine.

Serosa

Outer layer of the gut tube, simple squamous epithelium.

Visceral peritoneum

Another term for serosa, covering abdominal organs.

Adventitia

Connective tissue layer outside gut tube in cavities.

Esophagus

Passageway from throat to stomach in mammals.

Crop

Sac-like structure in birds for food storage.

Pigeons milk

Nutrient-rich secretion for young pigeons.

Ruminant stomach

Modified esophagus in ruminants for digestion.

Skeletal muscle

Muscle type allowing voluntary swallowing control.

Stomach

Storage organ for food, site of digestion.

Hydrochloric acid (HCl)

Strong acid secreted by parietal cells, pH 1.

pH 2.0-2.5

Acidity level in stomach aiding digestion.

Pepsinogen

Inactive enzyme converted to pepsin by HCl.

Pepsin

Active enzyme that digests proteins in stomach.

Lipase

Enzyme secreted by chief cells for fat digestion.

Churning action

Mechanical digestion facilitated by stomach's muscle layers.

Chyme

Creamy substance leaving stomach for small intestine.

Pyloric sphincter

Muscle regulating passage from stomach to intestine.

Cardiac sphincter

Muscle preventing backflow into the esophagus.

Reflux

Condition when stomach contents flow back into esophagus.

Protease

Enzyme that digests proteins, activated by low pH.

Amylase

Salivary enzyme inactivated by stomach's low pH.

Absorption in stomach

Limited to water, vitamins, and alcohol.

Oblique muscle layer

Third muscle layer in stomach aiding churning.

Mechanical digestion

Churning action in stomach via smooth muscle.

Pyloric sphincter

Regulates passage from stomach to small intestine.

Cardiac sphincter

Prevents backflow into esophagus from stomach.

Small intestine

Major site for chemical digestion and nutrient absorption.

Pancreatic juice

Raises pH to 7.2, contains digestive enzymes.

Endopeptidases

Digest proteins by breaking internal bonds.

Carboxypeptidases

Cleaves terminal amino acids from proteins.

Lipase

Digests fats by splitting fatty acids from glycerol.

Amylase

Converts starch into disaccharides.

Nucleases

Digests DNA and RNA into nucleotides.

Aminopeptidases

Cleaves amino acids from polypeptides.

Disaccharidases

Digests disaccharides into monosaccharides.

Maltase

Converts maltose into glucose.

Sucrase

Converts sucrose into fructose and glucose.

Lactase

Converts lactose into glucose and galactose.

Bile

Produced in liver, aids fat digestion.

Bile salts

Break up fats into smaller droplets.

Bile pigments

Waste from hemoglobin, colors feces.

Villi

Microscopic folds increasing surface area for absorption.

Microvilli

Small projections enhancing absorption efficiency.

Submucosa

Highly vascularized layer with blood vessels.

Hepatic portal system

Carries absorbed nutrients to the liver.

Glycogen

Stored form of glucose in the liver.

Lacteals

Lymph capillaries absorbing lipids into circulation.

Lipids

Used for energy or stored in body tissues.

Large Intestine

Houses trillions of bacteria; absorbs water.

Cecum

Blind pouch connecting large and small intestines.

Vermiform Appendix

Remnant of longer cecum in humans.

Gut Bacteria

Produce vitamins B and K; aid digestion.

Coprophagy

Eating feces to obtain nutrients.

Water Absorption

Major function of the large intestine.