BIOFOUND 5.5 Gas Exchange and Circulation pt 2

Oxygen Transport in Blood

Most oxygen is carried bound to hemoglobin in red blood cells; a small amount is dissolved in plasma.

Carbon Dioxide Transport in Blood

Carried as bicarbonate (HCO₃⁻), bound to proteins like hemoglobin, or dissolved in plasma.

Hemoglobin

An iron-containing protein in red blood cells that binds and carries oxygen (and some CO₂).

Hemocyanin

A copper-containing oxygen carrier found in some invertebrates (e.g., mollusks, arthropods).

Carbonic Anhydrase

An enzyme that rapidly converts carbon dioxide and water into carbonic acid (H₂CO₃), which dissociates into bicarbonate and protons.

Breathing and pH Regulation

By altering breathing rate, we change CO₂ levels in the blood, which shifts carbonic acid levels and thus regulates blood pH.

Gas Exchange in Invertebrates

Occurs via direct diffusion through moist surfaces (like skin or tracheae), eliminating the need for a complex circulatory system.

Open Circulatory System

A circulatory system in which hemolymph is pumped by a heart into open body cavities where it bathes organs directly.

Closed Circulatory System

A circulatory system in which blood flows through a continuous system of vessels, pumped by a heart.

Muscular Heart

Pumps blood through the circulatory system.

Atrium

Heart chamber that receives blood from the body or lungs.

Ventricle

Heart chamber that pumps blood out to the body or lungs.

Arteries

First type of blood vessel, carry blood away from the heart; thick-walled, high-pressure

Arterioles

Second type of blood vessel, small branches of arteries that regulate flow into capillaries

Capillaries

Third type of blood vessel, tiny vessels where gas and nutrient exchange occurs

Venules

Fourth type of blood vessel, collect blood from capillaries

Veins

Fifth type of blood vessel, return blood to the heart; low-pressure, often with valves

What are the Three Reasons Vertebrates Have Closed Circulatory Systems

Efficient delivery of oxygen and nutrients, support for high metabolic rates, better control of blood flow and pressure

Fish Circulatory System

A simple closed system with one circuit; heart pumps blood to gills for oxygenation and then to the rest of the body in a single loop.

Circulatory Circuit

A complete pathway of blood flow from the heart through vessels and back.

Double Circuit System (Land Animals)

Required to separate low-pressure pulmonary circulation (to lungs) from high-pressure systemic circulation (to body).

Pulmonary Circuit

Low-pressure circuit that carries deoxygenated blood from the heart to the lungs and returns oxygenated blood to the heart.

Systemic Circuit

High-pressure circuit that delivers oxygenated blood from the heart to the body and returns deoxygenated blood to the heart.

Sinoatrial (SA) Node

The heart’s pacemaker; generates electrical signals that initiate each heartbeat.

Atrioventricular (AV) Node

Delays the electrical signal to allow atria to contract before ventricles.

Ventricular Conducting Fibers

Spread the electrical signal through the ventricles, causing them to contract.

Pacemaker

The SA node sets the timing and rhythm of the heartbeat by spontaneously initiating electrical signals.