Transport in animals Flashcards
(34 cards)
What is the role of the circulatory system
To transport gases and nutrients around and organism in a transport liquid. This liquid is transported around in vessels and there is a pump to move the liquid (e.g the heart)
Name the types of circulatory system
Open system
Closes system
Double system
Single system
What is an open circulatory system
Had by invertebrates such as insects
Transport medium (haemolymph) pumped to an open body cavity (haemocoel)
Very few transport vessels
Transport medium is pumped at low pressure, transports food and nitrogenous waste (not gases which are transported via the tracheal system)
Once the exchange has occurred in cells and tissues, the transport medium returns to the heard via an open ended vessel
What is a close circulatory system
Had by vertebrates (e.g fish and mammals) and some invertebrates (annelid worms)
Transport medium (blood) remains inside of the blood vessels
Gases and small molecules can leave blood by diffusion or due to high hydrostatic pressure
Transport oxygen and carbon dioxide, oxygen is usually transported by a pigmented protein (haemoglobin)
What is a single closed circulatory system
Had by fish
Blood only passed through heart once per cycle
Blood passes through two sets of capillaries immediately after the heart, blood flows through capillaries in gills to be oxygenated then flows through capillaries delivering blood to the body before returning to the heart
This system works for fish due to the counter current flow mechanism in gas exchange
What is a double closed circulatory system
Had by birds and most mammals
Blood passes through heart twice per cycle
One circuit of blood vessels carry blood from heart to lungs for gas exchange and the second carry blood from heart to body to deliver oxygen and nutrients and to collect waste
Properties of arteries
The smooth muscle layer is thicker than in veins so that constriction and dilation can occur to control volume and pressure of the blood
The elastic layer is thicker to help maintain blood pressure because these walls can stretch and recoil in response to the heart beat
The collagen outer layer provides structural support
The wall is generally thicker to help maintain the blood pressure
Properties of arterioles
The smooth muscle layer is thicker than in arteries to help restrict blood flow into the capillaries
The elastic layer is thinner than in the arteries as the pressure of the blood is lower
The collagen layer is thinner (low pressure means not as much support is needed)
Wall is thinner as the pressure is lower
Properties of capillaries
They are one cell thick consisting of only a lining layer (no smooth muscle, elastic or collagen layer) this helps provide a short diffusion distance for exchanging materials
Properties of venules
Thin layer of smooth muscle
No elastic or collagen layer
Very thin wall (several venules join to form a vein)
Has valves
Properties of veins
Relatively thin smooth muscle layer so it cannot control the blood flow
Relatively thin elastic layer as there is low pressure
Contains a lot of collagen
Thin wall ask risk of vessel bursting is low due to low pressure, thin walls also mean that the vessels are easily flattened which helps the flow of blood up to the heart
Has valves to prevent back flow due to low pressure
Describe capillaries
Form capillary beds (many branched capillaries) at exchange surfaces
Have a narrow diameter to slow the blood flow
Red blood cells can only just fit through and are squashed against the walls which maximises diffusion
What is tissue fluid
The liquid and small molecules forced out through small gaps in capillaries
Tissue fluid can be formed and reabsorbed due to the interaction between hydrostatic and oncotic pressure
What is hydrostatic pressure
The pressure exerted by a liquid
What is oncotic pressure
The tendency of water to move into the blood via osmosis
How is tissue fluid formed
As blood enters capillaries from attentions, the decreased diameter leads to high hydrostatic pressure, this pressure forces water, glucose, amino acids, fatty acids, ions and oxygen out of the capillaries at the arterial end
This solution that has been forced out is called tissue fluid and bathes the cells in substances that they need
How is tissue fluid reabsorbed
Large molecules such as plasma proteins remain in the capillaries and therefore lower the water potential of the blood remaining in the capillary
This lowered water potential will result in higher oncontic pressure
The net movement is back into the capillaries via osmosis
Once equilibrium of the water potential has been reached, no more water from the tissue fluid can be reabsorbed back (the remaining liquid is absorbed into the lymphatic system and will eventually drain back into the bloodstream near the heart)
When the liquid is in the lymphatic system it is called lymph, it is like plasma without the large plasma proteins and less oxygen and nutrients (has been absorbed by cells)
Describe features of the mammalian heart
Organ made of cardiac muscle
Responsible for pumping blood around the body
Surrounded by pericardial membranes (inelastic membranes which prevent the heart from filling and swelling with blood)
Why is cardiac muscle useful
It is myogenic which means it automatically contracts and relaxes and never fatigues
How does the cardiac muscle work
Coronary arteries supply the cardiac muscle with oxygenated blood for aerobic
respiration which provides ATP so the cardiac muscle can continue to contract and relax
Internal structures of the heart
Left ventricle has a thicker muscular wall so it can contract with more force and pump the blood at a higher pressure (this is needed so the book will flow all the way around the body)
The right ventricle only pumps blood to the lungs which is much closer and requires blood to flow slowly to allow time for gas exchange, for this reason the muscular wall is thinner.
Both atria have very thin muscular walls because blood is only pumped from atria to ventricles so minimal pressure is required
What are the three key stages of the cardiac cycle
Diastole (relaxing)
Atrial Systole (atria contracting)
Ventricular Systole (ventricles contract)
Describe the cardiac cycle
At the start, (diastole) is where both the atria and the ventricles are relaxed so there is a larger volume in the chambers so pressure drops and blood flows in to atria from vena cava and pulmonary vein
As blood flows in pressure increases and atroventricular valves are forced open, atria contract which forces the blood from atria to ventricles
Atria then relax and ventricles contract, high pressure in ventricles causes atroventricular valves to shut, the semi lunar valves will open and blood will be pushed out of the ventricle and into the pulmonary artery and aorta
How to find cardiac output
Cardiac output= heart rate X stroke volume
where stroke volume is the volume of blood that leaves the heart each beat and heart rate is how many beats per minute
