BIO1022 Chapter Notes - Chapter Prescribed: Lymphatic Vessel, Collagen, Aldosterone
30 May 2018
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BIO1022 – Readings – Week 11
concepts 42.1 - 42.4
- circulate systems link exchange surfaces with cells throughout the body
- molecular trade animals carry out with environment - gaining O2 and nutrients
while shedding CO2 and other waste products - involves every cell of the body
- small molecules - including O2 and co2 can move between cells and their
immediate surroundings by diffusion
- this movement is very slow - for distances more than a few millimetres -
because the time it takes for a substance to diffuse from one place to another is
proportional to the square of the distance
- the relationship between diffusion time and distance places a substantial
constraint on the body plan of any animal
- natural selection has resulted in two basic adaptations that permit effective
exchange for all animal’s cells
• one - adaptation is a body plan that places many or all cells in direct
contact with the environment
•
o each cell can thus exchange materials directly with the
surrounding medium
o found only in certain invertebrates- including cnidarians and
flatworms
• other - circulatory system
•
o found in all other animals
o these systems move fluid between cell’s immediate surroundings
and the body tissues where exchange with the environment
occurs.
- gastrovascular cavities
• animals whose body shapes put many of their cells into contact with the
environment
• enabling them to live without a distinct circulatory system
• in hydras, jellyfish, and other cnidarians a central gastrovascular cavity
functions in the distribution of substances throughout the body as well as
in digestion
• an opening at one end connects the cavity to the surrounding water
• fluid bathes both the inner and outer tissue layers - facilitating the
exchange of gases and cellular waste
• only the cells lining the cavity have direct access to nutrients released by
digestion
• planarians and most other flatworms survive without a circulatory
system
•
o combination of a gastrovascular cavity and a flat body is well
suited for exchange with the environment
o
▪ a flat body optimises exchange by increasing surface area
and minimising diffusion distances
- open and closes circulatory systems
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• a circulatory system has three basic components
•
o a circulatory fluid
o a set of interconnecting vessels
o a muscular pump - the heart
o
▪ powers circulation by using metabolic energy to elevate the
circulatory fluid’s hydrostatic pressure - the pressure the
fluid exerts on surrounding vessels
▪ the fluid then flows through the vessels and back to the
heart
• by transporting fluid throughout the body the circulatory system
functionally connects the aqueous environment of the body cells to the
organs that exchange gases, absorb nutrients and dispose of wastes.
• open circulatory system
•
o the circulatory fluid - called haemolymph - is also ther interstitial
fluid that bathes body cells
o arthropods such as grasshoppers and some molluscs have open
circulatory systems
o heart contraction pumps the haemolymph through the circulatory
vessels into interconnected sinuses, spaces around the organs
o within the sinuses - chemical exchange occurs between the
haemolyph and body cells
o relation of the heart draws haemolymph back in through the pores
- which are equipped with valves that close when the heart
contracts
o body movements periodically squeeze the sinuses - helping the
haemolymph circulate
o the open circulatory systems for animals such as the larger
crustaceans - lobsters and crabs - includes a more extensive
system of vessels and an accessory pump
o evolutionary advantages
o
▪ lower hydrostatic pressures associated with open
circulatory systems make them less costly than closed
systems in terms of energy expenditure
• closed circulatory system
•
o a circulatory fluid called blood is confined to vessels and is distinct
from the interstitial fluid
o one or more hearts pump blood into large vessels that branch into
smaller ones that infiltrate the organs
o chemical exchange occurs between the blood and the interstitial
fluid as well as between the interstitial fluid and body cells
o annelids, cephalopods, and all vertebrates have closed circulatory
systems
o evolutionary advantages
o
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▪ relatively high blood pressure, which enables the effective
delivery of O2 and nutrients to the cells of larger and more
active animals
▪ well suited to regulating the distribution of blood to
different organs
- organisation of vertebrate circulatory systems
• the closed circulatory system of humans and other vertebrates is often
called the cardiovascular system
• blood circulates to and from the heart through a network of vessels
• arteries, veins and capillaries are the three main types of blood vessels
•
o within each type blood only flows in one direction
o arteries and veins are distinguished by the direction in which they
carry blood
o
▪ arteries carry blood away from the heart towards the
capillaries
▪ veins return blood towards the heart from capillaries
o arteries
o
▪ carry blood from the heart to organs throughout the body
▪ within organs - arteries branch into arterioles
▪
▪ these small vessels convey blood to capillaries,
microscopic vessels with very thin, porous walls
▪
▪ networks of capillaries - called capillary beds
infiltrate tissues
▪ across the thin walls of capillaries, chemicals
including dissolved gases are exchanged by
diffusion between the blood and interstitial
fluid around the tissue cells
▪
▪ at their downstream end - capillaries
converge into venules
▪
▪ and venules converge into
veins - the vessels that carry
blood back to the heart
• the hearts all vertebrates contain two or more muscular chambers
•
o the chambers that receive blood entering the heart are called -
atria - singular - atrium
o the chambers responsible for pumping blood out of the heart are
called ventricles
• single circulation
•
o bony fishes, rays and sharks - the heart consists of two chambers -
an atrium and a ventricle
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Document Summary
Bio1022 readings week 11 concepts 42. 1 - 42. 4. Circulate systems link exchange surfaces with cells throughout the body. Molecular trade animals carry out with environment - gaining o2 and nutrients while shedding co2 and other waste products - involves every cell of the body. Small molecules - including o2 and co2 can move between cells and their immediate surroundings by diffusion. This movement is very slow - for distances more than a few millimetres - because the time it takes for a substance to diffuse from one place to another is proportional to the square of the distance. The relationship between diffusion time and distance places a substantial constraint on the body plan of any animal. Coordinated cycles of heart contraction drive double circulation in mammals. Patterns of blood pressure and flow reflect the structure and arrangement of blood vessels. Blood vessel structure and function: blood vessels contain a central lumen - cavity - lined with an endothelium.
