Circulation and Gas Exchange
Chapter
42
Back to Biology 1402 page
Transport
Systems
Functionally connect
organs of exchange with body cells
Gastrovascular cavities
- function in both digestion and circulation - sufficient for body plans of
cnidarians and flatworms
Circulatory systems -
active pumping of fluid - ensures that no substance must diffuse very far to
enter or leave cell
Circulatory
Systems
Open - tissues bathed directly by hemolymph pumped by
heart into sinuses - common in most arthropods and molluscs
Closed - blood confined to vessels and pumped by pulsating
vessels or heart - common in annelids, some molluscs, all vertebrates
Cardiovascular
System
in Vertebrates
Heart (2- to
4-chambered, depending on group)
Blood pumped from ventricles
into arteries ฎ arterioles ฎ capillary beds ฎ venules ฎ veins ฎ atria
Double circulation - separte circuits to lungs and rest of body - no
mixing of oxygen-rich and oxygen-poor blood
Cardiac
Cycle
One complete cycle of
hearts pumping & filling
Systole - period of
contraction
Diastole - period of
relaxation
Coordinated by pacemaker
- sinoatrial node of right atrium - directs atria to contract followed by
ventricles
Vessels
Arteries and veins - 3
layers (endothelium, smooth muscle, elastic fibers, connective tissue)
Capillaries -
endothelium layer - sites of chemical exchange between blood and interstitial
fluid
Heart maintains pressure
in arteries - movement & valves important in veins
Role of
Lymphatic System
Blood lost in
capillary beds enters lymphatic capillaries - becomes lymph - similar to
interstitial fluid
Returns to circulatory
system near heart
Lymph nodes filled with
white blood cells - filters lymph - important in defense against infection
Components
of Blood
Connective tissue with
cells suspended in plasma - complex aqueous solution - nutrients, wastes,
gases, hormones, etc..
Erythrocytes - red blood cells - transport of oxygen
Leukocytes - defense against infection
Stem cells - give rise to all blood cells
Platelets - important in blood clotting
Gas
Exchange
Cellular respiration
demands constant supply of oxygen & elimination of carbon dioxide
Diversity of respiratory
adaptations in aquatic vs. terrestrial organisms
Gases diffuse down
concentration gradients - from areas of high concentration to areas of low
concentration
Respiratory
Adaptations -
Aquatic Animals
Cutaneous - absorption through skin - most are either long and
thin, or flat in shape - high ratio of surface area to volume
Gills - used by most aquatic animals
Ventilation - forced movement of water over gills - inceases efficiency of exchange
Countercurrent
exchange - blood and water (over
gills) flow in opposite directions
Respiratory
Adaptations - Terrestrial Animals
Trachael systems - branching tubes permeate body - bring oxygen
directly to cells - common in arthropods
Internal lungs - located in one area - not in direct contact with
cells - relies on circulatory system to transport oxygen to rest of body - most
terrestrial animals
Ventilation
Breathing - alternate
inhalation and exhalation of air
Positive and negative pressure systems
In birds, air sacs
ensure one-way flow of air through lungs - also reduce density
Regulated by breathing
control center in brain
Respiratory
Pigments
Transport gases - buffer
blood
Hemocyanin - contains
copper - widespread in invertebrates
Hemoglobin - contains
iron - widespread in vertebrates