BIOLOGY 2A03 Lecture Notes - Lecture 11: High-Pressure Area, Hemolymph, Circulatory System
13 Mar 2018
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Document Summary
Diffusion times (t) are proportional to the distance (x)2 over which diffusion occurs. Diffusion = too slow to transport nutrients and gases in most animals. A fast convection system = rapidly circulates fluids between surfaces in contact with the external milieu and cells deep inside organisms. General characteristics of circulatory systems: fluid (e. g. blood, haemolymph) Pump(s) or other propulsive structures - often with valves to assure unidirectional movement. E. g. heart, skeletal muscles contracting and relaxing along blood vessels (external pump: tubes, channels, or spaces for fluid to flow through. Circulatory system = distribution system for gases, nutrients, chemical signals, etc. Can have secondary roles (e. g. heat dissipation for thermoregulation) Circulatory fluids flow either through enclosed in vessels (tubes) separating them from tissues or through open spaces called sinuses (collectively known as haemocoel) - allows fluid direct contact with tissue. Closed circulatory system - fluid (e. g. blood) always remains within vessels. Allow for more control and support high pressures/flow rates.
