Transport in animals- transport in animals and blood vessels Flashcards
why are specialised transport systems necessary in multicellular organism unlike unicellular organisms?
- higher metabolic demands
- small surface area to volume ratio. The ratio gets smaller as the organism gets bigger.
- hormones or enzymes may be made I one place but needed in another
- food will be digested in one organ system but needed in every cell
- waste products from cells need to be transported to excretory organs
Describe the features of the circulatory system
- liquid transport medium that circulates around the system (blood)
- vessels are needed to carry transport medium
- pumping mechanism to move fluid around the system.
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.
Describe the open circulatory system
- few vessels to contain the transport medium
- transport medium is pumped straight from the heart into the body cavity of animal.
- open body cavity is called the haemocoel where transport medium is under low pressure.It comes into direct contact with cells and tissues where exchange takes place.
- transport medium returns to the heart through open-ended vessel.
where are open ended circulatory systems mainly found?
invertabrate animals including insects.
what is insect blood called and why is it different to human blood?
insect blood: haemolymph. It doesn’t carry oxygen or carbon dioxide. It carries food, waste products and cells involved against disease.
how is the heart placed in the open circulatory system?
the body cavity is split by a membrane and the heart extends along the length of the thorax and the abdomen of the insect.
Describe the closed circulatory system
- blood enclosed in blood vessels and doesn’t come in direct contact with cells.
- heart pumps blood under pressure and quickly.
- amount of blood flowing to particular tissue can be adjusted by widening or narrowing blood vessels.
- most closed circulatory systems contain a pigment that carries respiratory gases.
Can the amount of haemolymph flowing to a particular tissue be varied to meet demands?
no. Steep diffusion gradient cannot be maintained for efficient diffusion.
where are closed circulatory systems found?
in many different animal phyla including echinoderms (animals such as sea urchins and star fish)
Describe the single closed circulatory system
blood flows through the heart and is pumped out to travel all around the body before returning to the heart. Blood travels once through heart for each complete circulation of the body.
Where are single closed circulatory systems found?
fish and annelid worms
how does blood travel in a single closed circulation before returning to the heart?
-blood travels through two sets of capillaries. In the first, it exchanges oxygen and carbon dioxide. In the second, in the different organ systems, substances are exchanged between the blood and cells.
why is the activity levels of animals with single closed circulations low?
because the efficiency of the exchange processes is low as blood pressure is low due to narrow vessels so blood returns to heart slowly.
why are fish an exception as they have an efficient single circulatory system allowing them to be active?
- counter current gaseous exchange system
- their body weight is supported by the water in which they live and they do not maintain their own body temperature which reduces metabolic demands of their bodies.
Describe the double closed circulatory system
involves two circulation systems:
- blood is pumped from the heart to the lungs to pick up oxygen and unload carbon dioxide and then returns to the heart.
- blood flows through the heart and is pumped out to travel all around the body before returning tot he heart again.
What animals have the double circulatory system?
birds and animals
Describe the three structural components in blood vessels and explain how it’s related to the function of the blood vessel
- elastic fibres which are composed of elastin can stretch and recoil (to withstand pressure) providing vessel wall flexibility allowing a larger blood volume. It also helps to even out surges of blood pumped to keep a continuous flow.
- smooth muscles which contracts and relaxes to change size of lumen.
- collagen provides structural support to maintain shape and volume of vessel.
Describe the function of the arteries
carries blood away from the heart to the tissues. They carry oxygenated blood except from the pulmonary artery and the umbilical artery. Blood is under high pressure in arteries.
what is the function of the pulmonary artery?
carries deoxygenated blood from the heart to the lungs.
what is the function of the umbilical artery?
carries deoxygenated blood from foetus to placenta
what are arterioles and how do they link to vasoconstriction and vasodilation?
they link arteries and capillaries. They have more smooth muscle and less elastin on their walls compared to arteries. They constrict or dilate to control blood flow. When smooth muscle contracts it constricts the vessel preventing blood flowing to a capillary bed- vasoconstriction. When smooth muscle relaxes, blood flows into capillary bed- vasodilation.
what are capillaries?
microscopic blood vessels that link the arterioles and the venues. They form a network around tissues. Lumen is small. Entering the capillaries, it carries oxygenated blood but as it leaves the capillaries to venues it has less oxygen and more carbon dioxide. Lungs and placenta are exceptions.
how are capillaries adapted for their roles?
- they provide a large surface area for diffusion
- total cross sectional area of capillaries is greater than arterioles supplying them so rate of blood flow is slower giving more time for exchange.
- walls are single endothelial cell thick
