Transport in animals

• Explain why most animals need specialised transport systems


  As organisms became multicellular, transport systems had to evolve. These more complex organisms had organs performing specific fuctions that produced or required substances for/from elsewhere in the body. They are too large and complex for simple transport methods e.g. diffusion alone to be effective.
• Define the terms "mass flow", "vascular system", "open circulatory system", "closed circulatory system", "haemolymph", "single circulatory system", "double circulatory system", "pulmonary circulation" and "systemic circulation"


  Mass flow - a transport system where substances are transported in a mass of fluid

  Vascular system - a system of transport vessels in plants or animals

  Open circulatory system - a circulatory system with a heart but few vessels to contain the transport medium

  Closed circulatory system - a circulatory system where blood is enclosed in vessels and does not come into direct contact with the cells of the body beyond the vessels.

  Haemolymph - The transport medium or 'blood' in insects

  Single circulatory system - A circulatory system where the blood flows through the heart and is pumped out to travel all around the body before returning to the heart.

  Double circulatory system - A circulatory system where the blood travels twice through the heart for each complete circulation around the body. In the first circulation the blood is pumped form the heart to the lungs. In the second oxygenated blood is pumped to the brain and body to deliver oxygen to the cells.

  Pulmonary circulation - the portion of the cardiovascular system which carries deoxygenated blood away from the heart, to the lungs, and returns oxygenated blood back to the heart

  Systemic circulation - the part of the cardiovascular system which carries oxygenated blood away from the heart to the body, and returns deoxygenated blood back to the heart.
• State some examples of organisms with each type of circulatory system

  Arthropods have open

  Vertebrates have closed

  Fish have single

  Mammals have double
• Compare open and closed circulatory systems

  Open: Transport medium not in vessels - fills body cavity, Often has one or more pumps to circulate blood. Not as efficient - larger organisms will not survive. Doesn't carry the oxygen in insects (tracheal system)

  Closed - blood carried in vessels moved by a pump
• Compare single and double circulatory systems

  Blood under higher pressure in double circulatory system so organisms can be bigger and more active.
• List, in order, the sequence of blood vessel types that blood passes through once it leaves the heart

  Arteries, arterioles, capillaries, venules, veins
• Define the term "lumen"

  The inside space of a tubular structure, such as an artery or intestine
• State the names of the anatomical layers in arteries, veins, and capillaries.

  Endothelium, Elastic layer, Muscle layer, collagen
• State the properties and function of each component of blood vessel walls

  Endothelium - smooth so blood flows easily

  Elastic layer - elastic fibres allow stretching to withstand pressure and allow larger volumes through after heart pumps but spring back to original size to even out surges of blood and maintain a continuous flow.

  Muscle layer - constrict/dilate to control blood flow by changing size of lumen

  Collagen - provides structural support to maintain shape and volume of the vessel
• Compare the relative proportions of elastin fibres, smooth muscle and collagen in the aorta, medium-sized arteries and arterioles and relate these to their function.

  Arterioles have more smooth muscle and less elastin than arteries - little pulse surge but control flow into individual organs. Arterioles have sphincters - ring of muscle which can close to restrict blood to capillaries
• Describe the structure of capillaries, explain how capillaries are adapted for their function.

  Lumen small - RBCs travel single file

  Provide large surface area for the diffusion of substances into and out of blood

  Total cross-sectional are of capillaries is always greater than arteriole supplying them so the rate of blood flow falls. Slow movement - more time for diffusion

  Walls are squamous epithelium - single endothelial cell thick - think layer for diffusion - gaps between cells quite large in most of body (Not central nervous system where junctions between cells are very tight)See an expert-written answer!We have an expert-written solution to this problem!
• Explain how the structure of veins makes them adapted for their function

  Walls contain lots of collagen and little elastin fibre - no pulse by the time blood reaches veins so no need to even out surges. Wide lumen and smooth endothelium - blood flows easily.
• Describe the function of valves in veins and explain how they work

  Prevent back flow as only open one way - blood cannot fall back down
• Describe 3 adaptations that enable the body to return low pressure blood to the heart against gravity

  Most veins have one-way valves - flaps/infoldings of inner lining of vein preventing back flow

  Many big veins run between big, active muscles. Contractions squeeze veins forcing blood towards heart - valves prevent back flow when muscles relax

  Breathing movements of chest act as pump. Pressure changes and squeezing actions move blood in veins of chest and abdomen towards heart
• Describe the processes of vasoconstriction and vasodilation, and how this affects blood flow through capillaries

  Vasoconstriction - smooth muscle in arteriole walls contracts narrowing lumen and restricting blood flow into the capillaries

  Vasodilation - smooth muscle in arteriole walls relaxes and blood flows freely into the capillary bed
• List the components of blood and describe their functions

  Blood consists of plasma and cells (RCBs, lyphocytes etc.)

  Plasma is mostly water and carries glucose, hormones, proteins, cells and much more around the body
• State the functions of blood as a whole

  Transport of...

  Oxygen and Carbon dioxide to and from cells

  Digested food molecules from small intestine

  Nitrogenous waste products from cells to excretory organs

  Hormones

  Food molecules from storage compounds

  Platelets to damaged areas

  Cells and antibodies involved in immune response

  
  

  Also helps maintain constant body temp. and acts as a buffer to minimise pH changes
• Define the terms "blood plasma", "tissue fluid", and "lymph"


  Blood plasma - the main component of blood, a yellow fluid containing many dissolved substances and carrying the blood cells

  Tissue fluid - the solution surrounding cells of multicellular animals

  Lymph - modified tissue fluid that is collected in the lymph system
• Compare the components of blood, tissue fluid and lymph

  Blood contains molecules dissolved in plasma and larger plasma proteins as well as cells

  Tissue fluid contains molecules small enough to get through the capillary wall - water, ions, oxygen, glucose and amino acids NOT cells and large plasma proteins which remain in blood

  Lymph is similar to plasma and tissue fluid but contains less oxygen and nutrients. It also contains fatty acids absorbed from the small intestine and lymphocytes from lymph nodes which lie along the lymph vessels.
• Describe how total cross sectional area of blood vessels varies across the circulatory system

  Cross sectional area is greater at the capillaries than in the arteries or arterioles, slowing the blood down for diffusion to take place.
• Define the terms "hydrostatic pressure", "oncotic pressure" and "filtration pressure"

  Hydrostatic pressure - The pressure created by water in a closed system

  Oncotic pressure - The tendency of water to move into the blood by osmosis as a result of the plasma proteins

  Filtration pressure - the net driving force which pushes fluid into tissue spaces and out of vessels; the net result between oncotic pressure and hydrostatic pressure
• Describe how blood pressure / hydrostatic pressure varies across the circulatory system

  Highest in the arteries - just come from the heart

  Much lower in veins
• Describe how the oncotic pressure in capillaries is produced

  After tissue fluid is formed by ultrafiltration, the hydrostatic pressure in the capillaries falls as the blood travels along, as does the water potential due to the plasma proteins and cells left in the capillaries. This results in much higher oncotic pressure.
• Draw a diagram showing the production of tissue fluid in a capillary bed, and the possible routes it will take

  As capillaries are very thin, blood pressure/hydrostatic pressure is highforcing small molecules out of the capillary by ultrafiltration. This forms the tissue fluid which bathes the cells allowing useful substances to enter and waste to leave. Some of the fluid then enters the lymph vessels and the rest reenters the capillaries.

  
• Describe the structure and function of the lymphatic system

  Lymphatic system plays a major part in the immune system - lymph nodes along the vessels produce lymphocytes which then get passed into the blood.

  Lymph squeezed through the vessels by contraction of muscles and back flow is prevented by valves like those in veins.

  Rejoins blood in the subclavian veins in neck.
• Define the term "oedema"

  a condition characterized by an excess of watery fluid collecting in the cavities or tissues of the body.
• Label a diagram and a photograph of the internal structure of the heart

  
• Explain why the heart is called a "double pump"

  One side pumps to the lungs and the other to the rest of the body
• Describe the structure of the heart

  4 chambers: 2 atria - thin walls, receive blood from outside the heart - right supplied by superior and inferior venae cavae bringing blood from body, left supplied by pulmonary veins bringing blood from lungs

  2 ventricles - thick walls, receive blood from atria - Right has thinner wall, left is very thick.

  Right and left are divided by the septem.

  Between right atrium and ventricle is tricuspid valve and between left is bicuspid or mitral valve

  Tendons attach AV valves to walls of ventricles preventing valves inverting due to force of ventricle contracting
• Describe the flow of blood (include the names of the blood vessels adjoining the heart as well as whether the blood is oxygenated or deoxygenated and where the blood has come form or is going to).

  Body - venae cavae - right atrium - tricuspid valve - right ventricle - pulmonary artery - lungs - pulmonary vein - left atrium - bicuspid valve - left ventricle - aorta - body
• Name the type of muscle that the heart is made from and describe its features.

  Cardiac muscle which is incapable of going into tetanus (state of permanent contraction) and does not need to rest - does not get fatigued
• Name the blood vessels that supply the heart muscle with oxygen and glucose

  Coronary arteries
• State the role of the pericardial membranes

  Inelastic membranes that stop the heart over-distending with blood
• Explain why the walls of the ventricles are thicker than the walls of the atria

  Ventricles pump blood to the body or lungs, atria just move blood to the ventricles - ventricles must pump it must further
• Explain why the wall of the left ventricle is thicker than the wall of the right ventricle

  Left ventricle pumps all around the body, right just to lungs - much shorter distanceSee an expert-written answer!We have an expert-written solution to this problem!
• Describe the function of the valves and tendinous cords (valve cords/tendons) in the heart

  Between right atrium and ventricle is tricuspid valve and between left is bicuspid or mitral valve

  Semi-lunar valves stop back flow from arteries into ventricles

  Tendons attach AV valves to walls of ventricles preventing valves inverting due to force of ventricle contracting

  Valves prevent back flow of blood
• State the location and function of the septum in the heart

  Divides the left and right sides of the heart. Prevents oxygenated and deoxygenated blood mixing
• Name the stages in the cardiac cycle and outline what is happening at each stage

  Diastole - heart relaxes, blood enters heart, pressure gradually increases within the heart but artery pressure is at a minimum

  Atrial systole - contraction of the atria, blood moves into ventricles

  Ventricular systole - contraction of the ventricles, blood moves out into arteries
• Describe the events in the cardiac cycle including what is contracting or relaxing, changes in pressure in chambers, opening or closing of valves and direction of blood flow


  Diastole - atria filling with blood - bi and tri cuspid valves closed (pressure higher in ventricles than in atria) semi-lunar valves closed (pressure high in aorta and pulmonary artery)

  Atrial systole forces blood into ventricles. Bicuspid and tricuspid valves open - pressure higher in atria. Semi-lunars still closed (pressure higher in arteries)

  Ventricular systole - atria relax, blood propelled into aorta and pulmonary artery - pressure highes in ventricles - bi and tri cuspid close. semi lunars open

  Diastole - atria begin to refill - pressure in ventricles now less - semi-lunars closed but higher than atria - bi/tricuspid closed
• Interpret a graph of pressure change and volume change in different chambers of the heart (and arteries attached to the heart). Identify where valves open and close on the graph and explain why