3.1.2 Transport in animals Flashcards
What is the need for transport systems in multicellular animals?
-single celled organisms can use diffusion across outer membrane to get substances but as organisms get bigger, the distance between cells and the outside gets greater and diffusion would be too slow
What are the 4 main reasons animals have a specialised transport system?
1) to meet their high metabolic demands(need more O2+food and remove more waste products)
2) overcome smaller SA:V they have to absorb substances
3) maintain steep concentration gradients(rapid supply of glucose + oxygen and removal of CO2 especially for active animals)
4) allow diffusion across large distances(need energy from food for respiration+other metabolic processes)
What do most circulatory systems have in common?
-liquid transport medium that circulate around the body(blood)
-vessels to carry transport medium
-pumping mechanism to move fluid around the system
What is the circulatory system in mammals used for?
-to carry glucose and oxygen around the body
-to carry hormones antibodies(to fight disease) and waste products like CO2
What happens in an open circulatory system?
- blood is pumped from the heart into cavities surrounding organs
-in the haemocoel* the blood is under low pressure(pulmonary) so can come into direct contact with the with tissues and cells where exchange can take place between transport medium and cells and then medium truths to heart through open ended vessel
*open body cavity
Example of open circulatory system
some invertebrates have open circulatory system i.e insect:
-has segmented heart that contracts in a wave starting from the back—> pumps blood into a single main artery
-artery opens up into the body cavity
-blood flows around the insect’s organs, gradually making its way back into the heart segments through a series of valves
(haemolymph/blood doesn’t carry oxygen, only nutrients and white blood cells etc)
What happens in a closed circulatory system?
-blood is continuously contained in vessels and doesn’t come directly into contact with body cells
-heart pumps blood under high pressure (systemic)
-substances leave and enter via diffusion through blood vessel walls(widening and narrowing control blood flow)
Example of a closed circulatory system
all vertebrates i.e fish:
-heart pumps blood into arteries which branch out into millions of capillaries
-substances like oxygen and glucose diffuse from blood in capillaries to body cells BUT blood stays inside the blood vessels as it circulates
-veins take blood back to the heart
What is a single closed circulatory system?
- blood passes through the heat once for each complete circuit of the body
passes through 2 sets of capillaries before returning to heart:
-1st, exchanges O2 and CO2
-2nd, substances exchanged between blood + cells in other organ systems - narrow vessels causes blood pressure to drop + blood returns to heart slow = limits efficiency so tend to have low activity levels
Why do fish have an effective single circulatory system even though they are very active?
-have a countercurrent mechanism in gills that allows them to take a lot of O2 from the water = efficient gas exchange
-do not have to maintain own body temp because body weight supported by the water they’re in = reduces metabolic deman
What is a double circulatory system?
(most efficient system to transport substances around the body)
- blood passes through the heart twice for each complete circuit of the body
-each circuit only passes through 1 capillary network; relatively high pressure + fast blood flow can be maintained
Example of how double closed circulatory system works?
-birds and most mammals have this which allows them to be very active and maintain own body temp
- RIGHT SIDE: blood pumped from heart to lungs to pick up O2 and unload CO2 and returns to LEFT SIDE of heart
-LEFT SIDE: blood flows through the heart and is pumped out to travel all around the body before returning to the RIGHT SIDE of the heart again
(heart can give an extra push between lungs and rest of the body to make blood travel faster, so oxygen is delivered to tissues quicker)
Elastic fibres
-composed of elastin and can stretch and recoil to maintain BP and provide vessel walls with flexibility
Smooth muscle
contracts/relaxes, which changes size of the lumen and controls flow of blood
Collagen
provides structural support to maintain shape + volume of blood vessel and resist changes in BP
Artery
- carry blood from heart to rest if the body and have elastic tissue that recoils to maintain high pressure and overcome resistance of circulatory system
-thick muscle layer which contacts and relaxes control blood flow
-thick elastic fibres stretch and recoil to maintain high bp
-thick arterial wall(with collagen to resist changes in pressure) to prevent bursting from high bp
-no valves because bp is too high
Arterioles
(smaller branches of arteries, from arteries to capillaries under low pressure)
-thicker muscle layer to reduce blood flow to capillaries(vasoconstriction to prevent blood flow and vasodilation to allow blood flow to capillary bed)
-thinner elastic tissue because they don’t need to maintain a high bp
-have intermediate collagen to resist bp
-no valves
Capillaries
(arterioles branch into capillaries which are the smallest of the blood vessels, link arterioles and venules)
-substances are exchanged between blood and tissue fluid
-only have a thin endothelium and a narrow lumen
-provides a short diffusion distance
-they come in a large number(network) and are highly branched so they have a large SA for exchange
How are capillaries adapted for their role?
-large SA for diffusion of substances in and out of the blood
-total cross sectional area is always greater than arteriole supplying them to lower rate of blood flow to give more time for diffusion
-walls are one cell thick, giving a very thin layer for diffusion
Venules
(transport blood from capillary to veins under low pressure)
-has the same stricte and function of veins but are much smaller
-very thin walls that contain some muscle cells
Veins
(carry mostly deoxygenated blood back to the heart under low pressure)
-lower bp—> valves prevent blood flowing backwards
-have relatively thin muscle layer as there is no need to control blood flow
-thin elastic wall as low bp needed
-venal wall is thin
-more collagen than arteries for structural support as they carry large volumes of blood
How is the body adapted to pump blood under low pressure after veins return blood to heart?
-majority of veins have one way valves at intervals—> open so blood can pass through when blood flows in the direction of the heart + prevent back flow
-many of the bigger veins run between active muscles which squeeze veins when they contact, forcing blocks to the heart + valves prevent back flow when the muscles relax
-breathing movements of chest acts as a pump—> pressure changes and the squeezing actions move blood in the veins of the chest + abdomen towards heart
What are the 4 main blood vessels in double closed circulatory systems?
-Pulmonary artery + aorta(away)
-Pulmonary vein + vein(towards)
What kind of tissue is blood and how does that affect its role?
Blood is a connective tissue:
-connects all organs and transports substances(vitamins, minerals, ions, hormones, glucose, amino acids, oxygen + CO2 to respiring cells, waste products, antibodies, food molecules from storage compounds etc) between them
-contributes to maintenance of steady body temp and acts as a buffer to minimise pH change
What does blood consist of?
-plasma
-platelets
-red blood cells
-white blood cells(leucocytes)–} neutrophils/lymphocytes
Red blood cells
-4 to 6 mil per ml of blood
-45% of blood volume
-transports 02 in the blood via haemoglobin(carries iron)
-biconcave disc to increase SA and allow it to squeeze through gaps(flexible)
-no nucleus for more space to carry oxygen
-surface is covered with antigens integrally linked to membrane proteins/lipids that determine blood group
White blood cells(leucocytes)
-around 1% of blood vol
-NEUTROPHILS: type of phagocytes, engulf and destroy pathogens and send signals to lymphocytes, contain digestive enzymes and multilobed nucleus
-LYMPHOCYTES: produce antibodies + antitoxins, T lymphocytes attach to and destroy cells that have been take over by viruses/are cancerous, B lymphocytes are a memory cell which retains which retains which antibody it produces is for what pathogen
Platelets(thrombocytes)
-around 1% of blood
-small cell fragments made in the bone marrow
-cause blood clots by trapping blood cells
-contains enzymes released at the site of a cut
-converts soluble protein fibrinogeninto insoluble fibrinogen to form blood clot(prevent entry of microorganisms)
Plasma
-55% of total blood vol(90% water)
-transports substances around the body
-CO2 from cells to lungs; urea from liver to kidneys; carries nutrients, hormones and proteins to parts of the body
-filtered blood plasma makes tissue fluid
Tissue fluid
-fluid that surrounds cells in tissues to facilitate substance exchange between cells + blood
-made from substances that leave blood plasma i.e water, oxygen, glucose + ions
-doesn’t contain red blood cells or big/plasma proteins because they’re too large to be pushed out through capillary walls
-controls exchange of substances between blood and cells