3.1.2- transport in animals Flashcards
reasons why animals need a specialised transport system
increased metabolic demand
smaller SA:V
hormones and enzymes made in different locations than their target cells
digestive products needed in various locations
removal of waste products
what is an open circulatory sytem with an example
Transport fluid (haemolymph) pumped straight from heart into body cavity of the animal. This open body cavity is called the haemocoel, in haemocoel the transport medium is under low pressure. Comes into direct contact with the tissues and the cells. This is where exchange occurs between transport medium and the cells. Transport medium returns to heart through open ended vessels. E.G molluscs
what is a closed circulatory system?
transport medium (blood) remains within the blood vessels and materials diffuse in and out of the blood through the walls of tiny tubes called capillaries. Flow is at high pressure, the flow can be altered to meet demand. This carries nutrients, gases, and waste products. e.g. mammals
describe a single closed circulatory system
Found in fish and annelid worms. The blood flows through the heart and is pumped out to travel around the body before it returns to the heart. Blood travels through heart only once per complete circulation of body
describe a double closed circulatory system
Birds and mammals have high oxygen demands. A double circulatory system is the most efficient way to transport substances around the body. Involves two circulations 1) blood is pumped from heart to lungs to pick up oxygen and unload CO2 and then returns to heart 2) blood flows through the heart and is pumped out to travel all around the body before returning to heart.
what is the role of elastic fibres in blood vessels?
composed of elastin and can stretch and recoil, providing vessel walls with flexibility. enable expansion during systole and a smooth flow
what is the role of smooth muscle in blood vessels?
contracts of relaxes to change the size of the lumen
what is the role of collagen in the blood vessels?
provides structural support to maintain shape and volume of the vessel
what is the function of an artery?
Carry blood away from the heart to the tissues of the body. Carry oxygenated blood (except PA and UA). Arterioles link the arteries and the capillaries. Blood under high pressure.
what is the structure of an artery?
lumen, endothelium, elastic fibres, smooth muscle, collagen
arteries have a small lumen to keep blood at a high pressure
elastic fibres to recoil to keep blood under pressure and smooth out pulses
smooth muscles allows the artery to stretch, and control blood flow to organs
collagen fibres stop the artery bursting under pressure
what is the function of a vein?
carry blood away from the cells of the body towards the heart and carry deoxygenated blood (except PV and UV)
what is the structure of a vein?
larger lumen as blood is at a lower pressure
smooth endothelium to reduce friction
thinner layer of elastic fibres as the blood is at a lower pressure, less recoil is needed
smooth thinner layer as blood is under lower pressure
collagen fibres protect veins as nearer to the surface so more likely to be damaged
Many veins pass between large muscles, as the muscles move they squeeze the blood along the vein. Valves stop the backflow of blood when the muscles relax
what is the function of a capillary?
capillaries are microscopic blood vessels which link arterioles with venules. Form an extensive network through all tissues. enable exchange
what is the structure of a capillary?
endothelium
Small lumen only allows one cells at a time through to maximise gaseous exchange.
Blood is mostly oxygenated from the arterioles, by the time it leaves the capillaries for the venules it has less oxygen and more carbon dioxide.
Endothelium of thin flattened cells which are permeable so WBCs can pass through spaces between cells.
A short diffusion distance, smooth to reduce friction
Thin endothelium provides a short diffusion distance
Large network throughout body- large surface area.
