Chapter 8 - Transports Systems In Multicellular Animals Flashcards
Why are specialised transport systems needed
High metabolic demands
- diffusion over long distances is not enough to supply with needed quantities
- make lots of waste products, require lots of oxygen + food
SA:V is low
- not enough surface to transport required quantities
Hormones need to be transported
Waste products removed l
Food digested in one organ needs to be transported to every single cell
What features do circulatory systems have in common
- liquid transport medium that circulates around the system
- have vessels that Carr the transport medium
- pumping mechanism to move the liquid around
What is a
Mass transport system
When substances are transported in a mass of fluid with a mechanism for moving the fluid around the body
What are open circulatory systems
Blood isn’t enclosed in blood vessels all the time
It flows freely through the body cavity (haemocoel)
returns to heart through an open ended vessel
Example of open circulatory system in insect
Heart is segmented and contracts a wave, starting from the back pumping the blood into a single main artery
Artery opens up in haemocoel
Insect haemolymph transports food and nitrogenous waste
Haemolymph circulates but steep diffusion gradients can’t be maintained - can’t control the amount of haemolymph flowing to a particular tissue
Makes its way back to heart through open ended vessel
What is a closed circulatory system
The blood is enclosed inside blood vessels
Single circulatory systems definition
Single
- blood only passes through the heart once for each complete circuit of the body
Why single closed circulation is less efficient than double
Blood has to pass through 2 sets of capillaries , to exchange:
- O2 + CO2
- substances between blood and cells in organ systems
After passing through theses capillaries, blood pressure is very low, returns to heart slowly
Why is double closed circulatory efficient
Blood travels twice through the heart for each circuit of the body
Each circuit only passes through one capillary network
Which means
- High pressure and fast flow
Similarities between open and coded systems
Liquid transport medium
Vessels to transport the medium
Pumping mechanism to move fluid
Differences between open and closed systems
Open has few vessels
Closed has transport medium enclosed by vessels
Open isn’t enclosed
Closed can target specific tissues and cells
Open - transport medium pumped into body cavity (low pressure)
Closed - transport pumped by heart into artery (high pressure)
Arteries
- Thick muscular walls
- Have elastic tissue to stretch and recoil
- Inner lining is folded - allows expansion
- smooth muscle
Arteriole
-More smooth muscle than elastic
Capillaries (adaptations)
- large surface area for diffusion of substances
- single endothelial cell thick
- cross sectional area greater than arterioles so rate of blood flow falls, more time for exchange of materials
- substances pass out of fenestrations
Veins
- Wide lumen
- Collagen - but little elastic/smooth
- Valves
Venules
- Thin walls
- Smooth muscle
Adaptations that enable the body to overcome blood flow against gravity
- one way valves
- big veins run between active muscles so when muscles contract the blood is squeezed up the veins
- breathing movements and pressure changes cause blood in veins of chest and abdomen to move towards the heart
What does blood consist of
Plasma
- dissolves glucose, amino acids, mineral ions, hormones, large plasma proteins: albumin (maintaining osmotic potential), fibrinogen (blood clotting), globulins
Red blood cells / white blood cells
- carry oxygen
Platelets
- clotting mechanism
Functions of blood
Transport of:
- O2 + CO2
- digested food
- nitrogenous waste
- hormones
- cells and antibodies involved in immune response
- platelets to damaged areas
Maintains a steady body temperature
Minimising pH changes
How are substances transports between the capillaries and tissue fluid
- at start of capillary bed nearest to arterioles
- the hydrostatic pressure forcing fluid out of the capillaries is greater then the oncotic pressure attracting water in by osmosis
- so fluid is squeezed out of capillary into tissue fluid
- capillaries towards venules
- have a lower hydrostatic pressure than oncotic pressure because the pulse is lost
- water moves back into the capillaries by osmosis
What causes oncotic pressure
Plasma proteins in blood give capillaries high solute potential
Water has a tendency to move into capillaries by osmosis
What is tissue fluid
Fluid surrounding cells in tissues
Exchanges Oxygen water nutrients
Same components as blood but without:
- red blood cells
- plasma proteins
What are lymph vessels
Lymph transports excess tissue fluid to the heart
Has less oxygen and nutrients than tissue fluid and plasma
Contains fatty acids absorbed from villi on small intestine
How does the cardiac cycle pump blood round the body
Atrial systole
- ventricles are relaxed
- atria contract - decreases volume - increases pressure
- pushes blood into ventricle by atrioventricular valves
Ventricular systole
- atria relax
- ventricles contract - increase pressure - valves to close
- opens semi lunar valves
- blood forced into aorta/ pulmonary artery
Diastole
- ventricles and atria relax
- semi lunar valves close
- atria fill with blood
- atrioventricular valve opens
Calculate cardiac output
Heart rate
X
Stroke volume
Cardiac muscle is myogenic
Myogenic definition
Can contract and relax without signals from nerves
How does the heart beat
- sinoatrial node sends wave of electrical activity to atrial walls
- left and right atria contract at the same time
- non conducting collagen tissue prevents wave from ventricles
- SAN transfers waves of electrical conductivity (WOEA) to atrioventricular node
- slight delay before AVN passes wave to bundle of HIS
- HIS conducts wave of electrical actively to purkyne tissue
- cause ventricles to contract at same time
