Transport in Animals

• What three things make an effective transport system?

  + pump to create pressure that pushes fluid around body (heart) and means of maintaining pressure (aorta)

  + transport medium to carry nutrients, oxygen and waste (blood)

  + vessels to carry transport medium which may also act as an exchange surface to enable substances to enter and leave transport system (capillaries)
• What is the mass transport system?

  when substances are transported in a mass of fluid, with a mechanism for moving fluid around -> mass transport system
• What types of circulatory systems do large multicellular organisms usually have?


  open or closed circulatory system
• What are open circulatory systems?

  open ended and have very few vessels to contain transport medium
• What is the transport medium in an open circulatory system?

  haemolymph - blood mixed with interstitial fluid through short vessels and into blood cavity of animal
• What is the open body cavity called?

  haemocoel
• How does the transport medium travel in the haemocoel?

  the haemolymph is under low pressure and directly bathes organs and tissues, enabling diffusion of substances
• What happens when the heart in an open blood system relaxes?

  the haemolymph (transport medium) is drawn back into the heart via pores called ostia
• What are the open circulatory systems in insects?

  + insects have one main blood vessel, dorsal vessel

  + dorsal vessel houses the tubular heart

  + haemolymph moves around haemocoel due to movement of organisms and peristalsis

  + haemolymph re-enters heart via one-way valves called ostia
• What does haemolymph transport?

  nitrogenous waste, food and immune cells
• What kind of pressure is the haemolymph under?

  low pressure
• What are the problems with the open circulatory system?

  + steep concentration gradients needed for efficient diffusion cannot be maintained

  + volume of haemolymph flowing to particular tissue cannot be altered to meet changing demand
• What is a closed circulatory system?

  blood never leaves the blood vessels to come into direct contact with body cells
• What are the advantages of a closed circulatory system?

  + blood at high pressure, so flows easily

  + delivery and removal of oxygen, nutrients and waste is rapid

  + transport is independent of body movement

  + blood flow can be adjusted by widening/ narrowing vessels to meet changing demand
• What is a single circulatory system?

  blood passes through heart once for each circuit of the body
• What is a double circulatory system?

  blood passes through the heart twice for each circuit of the body
• What are the advantages of single circulatory systems?

  + less complex

  + does not require complex organs
• What are the disadvantages of a single circulation?

  + blood pressure will drop as blood passes through tiny capillaries of gills and blood travels more slowly

  + delivery rate of oxygen, nutrients and removal rate of waste is limited
• What are the advantages of a double circulation?

  + heart can give blood an extra push between lungs and rest of body, so travels faster

  + aorta maintains prssure

  + blood travels more quickly, so delivery rate of oxygen, nutrients and removal rate of waste in increased
• What is the structure of arteries and veins in general?

  + inner layer (tunica intima/ interna) is a thin layer of elastic tissue

  + in arteries it is folded and helps walls to stretch and recoil to maintain blood pressure

  + middle layer (tunica media) layer of smooth muscle

  + outer layer (tunica adventitia/ externa) layer of collagen and elastic fibre in arteries, collagen provides strength to withstand high pressure, and the elastin to recoil to maintain pressure
• What are the arterioles?

  + small blood vessels that take blood from arteries to capillaries

  + have layer of smooth muscle

  + contraction of smooth muscle contacts lumen, increases resistance to flow and reducing rate of flow

  + can be used to divert blood to regions needing more O2
• How does the structure of veins differ to arteries?

  + endothelium and tunica intima are NOT folded

  + tunica media and adventitia are thinner
• What are venules?

  + small blood vessels that take blood from capillaries to veins

  + have endothelium and thin layers of muscle, elastin and collagen

  + do not have pulses ( lost in capillaries)

  + low blood pressure so valves may be present as lumen diameter widens or where several venules meet
• How doe venules differ from veins?

  + smallest venules have no elastin fibres or smooth muscle

  + as venules widen, gain very thin layers of elastic tissue (tunica intima) and smooth muscle ( tunica media)
• How doe arterioles differ from arteries?

  + more smooth muscle than elastic fibres

  + experience smaller pulse surges

  + vasodilation dilates the lumen, vasoconstriction narrows the lumen
• What do valves do in veins?

  act as one-way blood flow system to prevent back flow
• How are larger veins located?

  + between active muscles in body, contract, squeeze vein and force blood towards the heart
• How do chest breathing movements help blood flow in veins?

  + movements act as a pump

  + pressure chances cause squeezing of blood in veins, moving blood towards heart
• What are the adaptations of capillaries to their function?

  + large SA for diffusion

  + total cross-sectional area of capillaries always greater than arteriole supplying them: rate of blood flow falls, more time for exchange of materials

  + walls = single endothelial cell, thin for short diffusion distance
• What proportion of plasma consists of plasma proteins and what are half of them?

  about 8% of blood plasma consists of plasma proteins and about half of plasma proteins are albumins
• What are plasma proteins?

  + group proteins involved in transport of other substances (e.g. fatty acids, hormones)

  + too large to cross the endothelial capillary wall

  + hydrophilic so helps influence movement of water by osmosis - affects blood pressure
• What are the four main functions of blood?

  + transport (erythrocytes: O2, CO2) (plasma: CO2, nitrogenous waste, hormones, nutrients, cells, platelets)

  + defence/ immunity (platelets, wbcs (leukocytes), antibodies)

  + thermoregulation

  + maintaining pH of body fluids (buffering)
• What is negative feedback?

  + a type of regulation that responds to a change in conditions by initiating responses that will counteract change

  + maintains steady state
• What is the main adaptation of the neutrophil in relation to capillaries?

  multi-lobed nucleus makes it easier to squeeze between squamous cells of capillary endothelium
• What are the four types of leukocytes?

  monocyte, macrophage, neutrophil and dendritic cell
• What are the three types of capillaries and where are they found?

  + continuous capillaries found in nervous system, skin and lungs

  + fenestrated capillaries (with pores) in kidneys, small intestine and endocrine glands

  + sinusodial capillaries in liver, spleen, lymph nodes, bone marrow and endocrine glands
• What does endothelial permeability depend on?

  the tissue type that is supplies and can be varied to meet demand
• What is a pericyte?

  + multi-functional mural cells of microcirculation that wrap around endothelial cells lining capillaries

  + embedded in basement membrane of blood capillaries

  + essential for regulation and maintenance of homeostasis within body, such as the blood-brain barrier
• How are pericytes structured?

  + very prominent nucleus to distinguish from endothelial cells

  + contain dendrite-like extensions that wrap around capillary wall to regulate blood flow

  + can form direct connections with adjacent cells by forming gap junctions between them
• What is the role of tissue fluid?

  + in capillaries fluid passes out of blood and bathes respiring tissue cells

  + supplying dissolved oxygen and nutrients to cells requiring it

  + waste molecules diffuse from cells into tissue fluid

  + tissue fluid (interstitial fluid) re-enters capillaries