Biology 1110 - Lecture 14: Ventilation and Gas Exchange in Animals

Practice vocabulary flashcards covering gas exchange surfaces, ventilation mechanisms, countercurrent exchange, and comparative respiratory systems across insects, fish, amphibians, birds, and mammals.

Ventilation

The flow of a respiratory medium (air or water) across a specialized gas exchange surface.

Respiratory Surface Moisture

The essential structural characteristic of gas exchange surfaces requiring a film of water, which allows gases to dissolve and diffuse across cell membranes more rapidly.

Gastrovascular Cavity Gas Exchange

The mode of gas exchange in cnidarians and platyhelminthes (flatworms), where materials diffuse directly across the external body surface and the tissues lining the internal cavity.

Tracheal System

The gas exchange system in insects consisting of an extensive network of air-filled tubes branching throughout the entire body to deliver oxygen directly to tissues.

Tracheoles

Small, fluid-filled terminal branches of the insect tracheal system that serve as the primary gas exchange surface in direct contact with body cells.

Spiracles

Small pores located on the body wall of an insect through which air enters and exits the tracheal system.

Abdominal Pumping

A ventilation mechanism used by large insects in which rhythmic compression and expansion of the abdomen moves air into and out of the trachea.

Aquatic Respiratory Medium

A gas exchange medium (water) that holds approximately $40\times$ less $O_2$ than air and has a much higher density, requiring more energy to move across respiratory surfaces.

Gill Filaments

Thin, highly vascularized subdivisions of gills that serve as the gas exchange surface in fish and aquatic amphibians.

Countercurrent Exchange

An arrangement in fish gills where water and blood flow across the lamellae in opposite directions, maintaining a favorable $O_2$ concentration gradient along the entire capillary length and allowing $\text{approximately } 80\text{--}90\%$ of $O_2$ in water to diffuse into the blood.

Positive Pressure Breathing

A ventilation mechanism used by amphibians (such as frogs) that pushes air from the mouth into the lungs using positive pressure, compensating for the lack of ribs and a diaphragm.

Buccal Pumping Cycle

The two-step amphibian ventilation process where the floor of the mouth drops to draw air through open nostrils into the buccal cavity, followed by nostril closure and mouth floor elevation to force air through the glottis into the lungs.

Parabronchi

Small, rigid air tubes within bird lungs where gas exchange occurs as air flows through them continuously in one direction.

Avian Air Sacs

A set of eight to nine non-respiratory structures distributed above and below bird lungs that expand and contract like bellows to drive continuous, unidirectional airflow through the parabronchi.

Two-Cycle Avian Ventilation

The avian respiratory process requiring two complete inhalation and exhalation cycles to move a single volume of air through the posterior air sacs, lungs, anterior air sacs, and out of the body.

Negative Pressure Breathing

The ventilation mechanism used by mammals where contracting the diaphragm and rib muscles increases lung volume and drops internal pressure, pulling air into the lungs.

Alveoli

Clusters of tiny, expandable air-filled sacs at the ends of bronchioles in mammalian lungs that provide an extensive surface area for gas exchange.

Pulmonary Capillaries

Fine branching networks of blood vessels surrounding the alveoli that facilitate the diffusion of $O_2$ into the blood and $CO_2$ into the alveoli down their concentration gradients.

Two-Way Airflow (Tidal Breathing)

The bidirectional breathing mechanism of mammals in which fresh incoming air mixes with residual expired air left in the lungs, reducing the steepness of the $O_2$ concentration gradient relative to unidirectional avian flow.