Chapter 8: Transport in animals Flashcards
Why do multicellular animals need transport systems ?
multicellular organisms have high metabolic demands (need loads of o2 and food in cells deep in the body) —> cannot be supplied by diffusion
multicellular organisms have a small SA:V ratio + are larger in size (and so large diffusion distance)
waste products need to be removed (from metabolic reactions)
what is a circulatory system
a mass transport system responsible for carrying gases (o2 and co2) nutrients, waste products and hormones around the body to where they are needed.
what are the different types of circulatory system
single circulatory system
open circulatory system
double circulatory system
closed circulatory system
what features do all circulatory systems have in common
have a liquid transport medium that circulates around the system (blood)
have vessels that carry the transport medium
have a pumping mechanism to move the fluid around the system
what does an open circulatory system look like (in an insect)
very few vessels to contain transport medium, pumped straight from heart into the body cavity of animal
open body cavity = haemocoel —> blood here comes into direct contact with tissues and cells
exchange takes place between transport medium and cells under low pressure
why doesn’t gaseous exchange take place via the open circulatory system in insects?
in insects gaseous exchange takes place in the tracheal system
also insect blood (haemolymph) does not carry co2 or o2
what does a closed circulatory system look like
blood flows in enclosed vessels + the heart pumps the blood under pressure
substances leave and enter the blood by diffusion through the walls of the blood vessels
amount of blood flowing to a particular tissue can be adjusted through the widening and narrowing of these blood vessels
blood carries respiratory gases
what does a single closed circulatory system look like (in fish)
blood travels through the heart once for each complete circulation
the blood passes through two sets of capillaries (in the gills and in the body)
in the gills it exchanges oxygen and co2, but in the body other substances are exchanged
blood flows back to the heart under low pressure ( limited efficiency of exchange due to circulatory system)
what does a double closed circulatory system look like ?
most efficient system for transporting substances
blood travels through the heart twice in enclosed blood vessels
to the lungs (pulmonary circuit) and to the body (systemic circuit)- for gaseous exchange
travels to and away from the heart under high pressures
Describe the structure and function of an artery
must carry blood away from the heart under high pressure
contains high proportions of elastic fibres and collagen ( and very low proportions of smooth muscle)
elastic fibres allow the the vessel walls to stetch and recoil - enabling it to with stand the force of blood pumped out of the heart and stetch
the collagen- provides a structural support to maintain the shape of the vessel
give 2 examples of the artery carrying deoxygenated blood
pulmonary artery and umbilical artery
What is the endothelium, where is it present and what function does it carry out
The endothelium is a thin layer of cells present in all of the blood vessels and enables blood to flow easily
Describe the structure and function of an arteriole
higher proportion of smooth muscle, less elastin and little collagen
smooth muscle enables arteriole to constrict and dilate controlling the flow of blood to different capillary beds - vasoconstriction/dilation
elastin- allows it to stretch/ provides flexibility
collagen- provides support
describe the structure and function of a capillary
are microscopic blood vessels linking arterioles and venules
consist of a thin layer of endothelial cell wall only- has large gaps where substances can pass out of the capillary for exchange (into the surrounding fluid)
thin layer for diffusion is provided
lumen of capillary is thin so the RBCs can travel in single file (for exchange)
How are capillaries especially adapted to their role
provide a large surface area for diffusion into and out of the blood
rate of blood flow falls = more time for the exchange of materials by diffusion (because of larger total cross sectional area of the capillaries)
Describe the structure and function of veins
transports blood back to the heart under low pressure (typically carries deoxygenated blood)
have high proportions of collagen and some smooth muscle, very low proportion of elastin
muscle and elastic layers are thin because constriction not needed to control flow of blood
contains a wide lumen- maximising volume of blood being carried to the heart, because pressure is low
weak pulse indicating little elastic tissue and smooth muscle
has valves to prevent backflow of blood
Describe the structure and function of venules
link the capillaries to the veins
Venules have a high proportion of smooth muscle + very thin walls
this allows the constriction and dilatation
What is hydrostatic pressure and what is oncotic pressure (Include their values)
oncotic pressure is the tendency for water to move out of the blood by osmosis and is always at -3.3 kPa
hydrostatic pressure is the pressure from the heart beating created when there is a surge of blood and it is always at + 4.6 kPa
How is oncotic pressure created
plasma proteins especially albumin have an osmotic effect (give blood in the capillaries a high solute potential compared to surrounding fluid)
because of this water has a tendency to move into the blood by osmosis (this is termed oncotic pressure)
How is hydrostatic pressure created
when there is a surge of blood that occurs every time the heart contracts + this forces fluid out of the capillaries
Describe the process of forming tissue fluid from blood plasma
blood flows in through the arterial end (of the capillary)-
hydrostatic pressure is higher than oncotic pressure here so there is an overall net movement of fluid out of the blood and out the capillary
this results in the formation of tissue fluid
diffusion takes place between blood and cells through tissue fluid
what happens to the tissue fluid at the venous end of the capillaries
towards venous end balance of forces change
hydrostatic pressure falls to about 2.3kPa and oncotic pressure remains at -3.3kPa
oncotic pressure is now stronger than hydrostatic pressure and so there is now a net flow of fluid back into venous end of capillaries
Describe the composition of the blood
blood consists of a yellow liquid called plasma (Mostly made up of water)
plasma contains a variety of components dissolved in it (glucose, amino acids, mineral ions, hormones + plasma proteins)
plasma also carries red blood cells, platelets + white blood cells
Describe the composition of tissue fluid
same composition as plasma but without red blood cells and plasma proteins
describe the composition of the lymph
lymph contains less oxygen + nutrients than tissue fluid & plasma + contains more fatty acids
describe some other components of the lymph and lymph vessels
contain lymph nodes where lymphocytes build up and produce antibodies + pass into the blood
lymph nodes intercept bacteria and debris from the lymph (ingested by phagocytes from the nodes)
lymphatic system plays a large role in defence mechanisms in the body
how is oxygen transported via the haemoglobin
oxygen binds reversibly (and loosely) to the haem groups in each of the 4 subunits (contain iron Fe 2+ ions)
this means that each haemoglobin molecule carries 4 o2 molecules
how does oxygen show positive cooperativity in the haemoglobin
the arrangement of the haemoglobin molecule means that as soon as one oxygen molecule binds to the haem group the molecule changes shape.
this makes it easier for the next oxygen molecule to bind to the haem group.
How does the oxygen dissociation curve work
