Module 3.1.2- Transport in Animals

• The need for specialised exchange system in multicellular organisms

  - metabolic demand is high- low surface area to volume ratio- as organism gets large, diffusion is required over longer distances
• What is an open circulatory system and what are the characteristics of one

  - no separate tissue fluid- blood circulates around the organs and cells- pressure cannot be raised- circulation affected by body movement- oxygenated and deoxygenated blood mix freely- few vessels to contain transport medium
• What is the haemocoel? (Insects/invertebrates circulatory system)


  The open body cavity. (Mainly in insects) The blood is pumped straight here.

  
• Describe the function of haemolymph. (Insects/invertebrates circulatory system)


  Insect blood. Does not carry OXYGEN or BLOOD. It transports food and nitrogenous waste and the cells involved in defence against disease. The body cavity is split by a membrane.
• What is a closed circulatory system and what are the characteristics of one


  Blood enclosed in blood vessels and do not come in contact directly with the cells of the body.- blood is pumped under pressure (maintained)- blood returns directly to heart- substances leave and enter by diffusion- amount of blood controlled (widening or narrowing of blood vessels)
• Single closed circulatory system


  The blood is pumped through the heart once for each complete circuit. (e.g. fish). Goes through 2 sets of capillaries.

  
• Fish- Single closed circulatory system


  Blood passes through 2 sets of capillaries1st set: O2 and CO2 exchanged2nd set: substances exchanged between cells and blood in different organ systemsTherefore blood pressure drops significantly returning to the heart slowly making this a relatively slow process. (Fish however are still fast due to countercurrent gas exchange)
• Mammals- Double closed circulatory system


  The blood is pumped through the heart twice for each complete circuitBlood is pumped from the heart to the lungs (pulmonary circulation)Then to the heart then blood is pumped all around the body (systemic circulation)- relatively high pressure- fast flow of blood maintained

  
• Elastic fibres


  Composed of elastin and can stretch and recoil providing vessel walls with flexibility
• Smooth muscle


  Contracts or relaxes changing size of lumen
• Collagen

  Provides structural support to maintain the shape and volume of the vessel
• What are arteries


  Blood vessels that carry blood away from the heart. Carry oxygenated blood (except in Pulmonary Artery and Umbilical Artery)
• Structure and composition of arteries.


  Blood in arteries is under higher pressure maintained by the recoil of elastic tissue.-Thick wall with an endothelium lining (smooth so blood flows easily over it) -Thick middle layer of elastic tissue-Thick smooth muscle.-Thick outer layer rich in collagen-Small lumen.
• What are arterioles and its composition compared to arteries

  They link arteries and capillaries together. -More smooth muscle (than arteries)- can control flow of blood into individual organs-Less elastin fibres (than arteries)
• Structure and composition of capillaries


  Microscopic vessel linking arterioles with venules. Structure: 1 cell thickness (small lumen)function: aids in gas diffusion So thin so they only provide enough room for blood cells to squeeze through in single file. Gases, nutrients and waste product rapidly transfer across the thin porous capillary walls
• Capillaries adaptations


  Blood entering capillaries are oxygenated and leave deoxygenated.- large SA for diffusion- walls are single endothelium cell thick, small distance for diffusion- total cross sectional area of capillaries is greater than arteriole supplying them so rate of blood falls. relatively slow movement allows enough time for diffusion to occur.
• Structure and composition of veins

  carry blood to the heart. Carry deoxygenated blood (except pulmonary vein and umbilical vein)- Lots of collagen- Low elastic fibre (low pressure)- Wide lumen (so blood flows easily)- Smooth lining (so blood flows easily)
• Venules


  The smaller veins that connect capillaries to the larger veins.
• Adaptation of veins


  -Valves prevent back flow of blood -Valves close when blood goes away from the heart (backwards)-Thin outer wall - muscles can squeeze vein: keeps blood moving up the body-Breathing movements of chest act as a pump to push blood towards the heart.

  
• Blood consists of plasma. What is plasma composed of?

  dissolved glucose mineral ions hormones large plasma proteins red blood cells platelets

  
• Functions of blood


  Transports:- O2 (to) and CO2 (from) to respiring cells - digested food from small intestine- hormones- nitrogenous waste products- platelets to damaged areas- cells and antibodies- maintenance of a steady body temp acting as a buffer
• Tissue Fluid


  The fluid surrounding the cells and tissues.

  
• Oncotic pressure


  The pressure of water to move, typically into the capillary, as the result of the presence of plasma proteins.
• Hydrostatic Pressure


  The pressure within a blood vessel that tends to push water out of the vessel
• Explain process of the formation of tissue fluid

  ATERIAL END (left side) - There is high Hydrostatic Pressure so fluid diffuse out as tissue fluid by OSMOSIS.

  Moving down capillary, hydrostatic pressure decreases.

  VENULE END (right side)- There is low Hydrostatic Pressure so fluid diffuses back in by OSMOSIS. (90% comes back in)
• Tissue fluid composition


  Same composition as plasma without red blood cells and plasma proteins. dissolved glucose mineral ions hormones platelets
• Lymph


  10% of tissue fluid drained into lymph capillaries.
• Composition of Lymph

  Similar to tissue fluid and plasma but with less oxygen and nutrients+ fatty acids
• Adaptations of lymphatic system


  - squeezing of body muscles transport lymph- one-way valves to prevent backflow- lymphocytes build up in the lymph node- lymph nodes intercept bacteria etcenlarged lymph nodes= sign body is fighting off an evading pathogen
• haemoglobin + oxygen


  <=> oxyhaemoglobin

  
• positive cooperativity


  the first substrate changes the shape of the enzyme allowing other substrates to bind more easily
• Levels of oxygen in the erythrocytes in lungs and body tissues

  Low in lungs

  High in body tissues
• Oxygen dissociation curve


  A curve on a graph that shows how saturated with oxygen haemoglobin is at any given partial pressure

  
• At low partial pressure of oxygen...


  ...few haem groups are bound to oxygen, so haemoglobin does not carry much oxygen
• At higher partial pressure of oxygen...


  ...more haem groups are bound to oxygen, making it easier for more oxygen to be picked up
• At the top of an oxygen dissociation graph the haemoglobin becomes...

  ...saturated at very high pO2 as all haem groups become bound
• Bohr effect


  As the partial pressure of carbon dioxide rises, haemoglobin gives up oxygen more easily.The graph shifts to the right

  
• Why is the Bohr effect important?


  Active tissues with a high pCO2, oxygen is given easily

  Lungs with low pCO2, oxygen binds to haemoglobin easily
• Fetal haemoglobin Vs Adult haemoglobin


  Fetal haemoglobin has a higher affinity for oxygen than the adult so the graph shifts left

  
• Lungs regarding partial pressure


  At the lungs, the proportion of CO2 in the air is relatively low, therefore the oxygen binds to the haemoglobin more easily