Animal Nutrition, Digestion, Circulation, Gas Exchange, and Osmoregulation

Comprehensive vocabulary flashcards covering key terms and concepts across animal nutrition, digestion, circulation, gas exchange, and osmoregulation based on lecture notes.

Ingestion

The first stage of food processing, defined as the act of eating or taking food into the body.

Digestion

The second stage of food processing involving the enzymatic and mechanical breakdown of large food molecules into small particles.

Absorption

The third stage of food processing, characterized by the uptake of small nutrient molecules by an organism's body cells.

Elimination

The final stage of food processing, involving the passage of undigested material out of the digestive tract in feces.

Gastrovascular Cavity

A central digestive compartment with a single opening that functions in both digestion and nutrient distribution in simple animals like hydra.

Alimentary Canal

A complete digestive tract consisting of a tube with two openings (a mouth and an anus) organized into specialized compartments.

Crop

A pouch-like organ in the alimentary canal of animals such as earthworms, grasshoppers, and birds used for storing food prior to digestion.

Gizzard

A specialized muscular digestive organ in earthworms, insects, and birds that functions in mechanically grinding food.

Chief Cells

Specialized cells located in the gastric glands of the stomach that secrete the inactive enzyme precursor pepsinogen.

Parietal Cells

Cells in the gastric glands of the stomach that secrete hydrogen and chloride ions to form hydrochloric acid ($\text{HCl}$).

Pepsin

An active digestive enzyme in the stomach that hydrolyzes proteins into smaller polypeptides; activated when hydrochloric acid cleaves pepsinogen.

Bile

A digestive secretion produced by the liver and stored in the gallbladder that aids in the breakdown and emulsification of fats in the small intestine.

Hepatic Portal Vein

A blood vessel that conveys nutrient-rich blood from the capillaries of the digestive tract directly to the liver for detoxification and metabolic processing.

Villi

Finger-like projections on the inner surface of the small intestine that greatly increase surface area for nutrient absorption.

Lacteal

A small lymphatic vessel inside each intestinal villus that absorbs digested fats and carries them into the lymphatic system.

Cecum

A blind pouch at the junction of the small and large intestines that serves as a site for bacterial fermentation of plant material, enlarged in nonruminant herbivores.

Insulin

A hormone secreted by pancreatic beta cells in response to high blood glucose levels that promotes cellular glucose uptake and glycogen synthesis.

Glucagon

A hormone secreted by pancreatic alpha cells in response to low blood glucose levels that stimulates the breakdown of glycogen into glucose.

Open Circulatory System

A circulatory system in which fluid called hemolymph directly bathes organs and tissues in sinuses rather than remaining in closed vessels.

Closed Circulatory System

A circulatory system in which blood is confined to vessels and kept separate from interstitial fluid.

Hemolymph

The body fluid that functions as both blood and interstitial fluid in invertebrates with an open circulatory system.

Single Circulation

A circulatory pathway found in fishes where blood passes through a two-chambered heart once per complete body circuit.

Double Circulation

A circulatory pattern in amphibians, reptiles, birds, and mammals where blood passes through the heart twice during a complete circuit around the body.

Atrioventricular (AV) Valves

Heart valves located between the atria and ventricles (tricuspid and mitral) that prevent backflow of blood into the atria when ventricles contract.

Semilunar Valves

Valves situated at the exits of the heart (pulmonary and aortic valves) that prevent blood from flowing back into the ventricles.

Systolic Pressure

The peak blood pressure exerted in the arterial system during ventricular contraction (systole).

Diastolic Pressure

The minimum blood pressure maintained in the arteries when the ventricles are relaxed (diastole).

Countercurrent Exchange

The transfer of a substance or heat between fluids flowing in opposite directions, maximizing gas extraction efficiency across respiratory surfaces like fish gills.

Tracheal System

A network of air-filled tubes branching throughout insects that delivers oxygen directly to body cells independently of the circulatory system.

Negative Pressure Ventilation

A breathing method used by mammals where contracting the diaphragm and rib muscles expands the thoracic cavity, creating a vacuum that pulls air into the lungs.

Haemoglobin

An iron-containing respiratory pigment present in erythrocytes of all vertebrates and some annelids that turns red when bound to oxygen.

Haemocyanin

A copper-containing respiratory pigment found in most mollusks and arthropods that appears blue when oxygenated and colorless when deoxygenated.

Erythrocytes

Red blood cells specialized for the transport of oxygen and some carbon dioxide throughout the circulatory system.

Bicarbonate Ion ($\text{HCO}_3^-$)

The primary chemical form in which the majority ($60\%$ to $88\%$) of carbon dioxide is transported through blood plasma.

Osmoregulation

The active regulation and maintenance of solute concentrations and water balance within an organism relative to its environment.

Osmoconformer

An animal that remains isoosmotic with its marine environment, maintaining an internal solute concentration equal to external surroundings.

Osmoregulator

An animal that controls its internal osmolarity independently of the solute concentration of its surrounding environment.