• Large organisms require specialised mass transport systems for a number of reasons:


  - increasing transport distances

  - SA:V ratio (low)

  - increasing level of metabolic activity
• What is mass flow


  the bulk movement of materials
• What do mass transport systems help to do

  - bring substances quickly from one exchange site to another

  - maintain the diffusion gradients at exchange sites between cells and their tissue fluid surroundings

  - ensure effective cell activity by keeping the immediate fluid environment of cells within a suitable metabolic range
• What is a single circulatory system

  Blood only passes through the heart once for each complete circuit of the body
• What is a double circulatory system

  Blood passes through the heart twice for each complete circuit of the body
• Describe the circulatory system of a fish

  - A single circulatory system (2 chambers in heart, 1 atrium, 1 ventricle

  - Blood only passes through the heart once for each circuit of the body

  - closed system: blood contained in blood vessels

  - gills exchange site for oxygen and CO2

  
• What is an advantage of the mammalian double circulatory system?

  - extra contraction in left ventricle allows enough pressure to pump blood throughout the body

  - efficient and fast delivery of oxygen

  - can keep pressure to exchange surfaces low to avoid damage of capillaries

  - increased pressure and speed in pulmonary circuit helps to maintain a steeper concentration gradient which allows for efficient exchange of nutrients and waste
• Describe the circulatory system in mammals

  - A double circulatory system (4 chambers in heart, 2 atria, 2 ventricles)

  - Blood passes through the heart twice for each complete circuit around the body

  - closed system: blood contained in blood vessels

  - left side of heart: oxygenated blood

  - right side of heart: deoxygenated blood

  - The pulmonary system sends blood to the lungs (low pressure) and the systematic system sends blood to the rest of the body (higher pressure)

  
• What is a closed circulatory system?

  - The blood is enclosed inside blood vessels

  - All vertebrates (eg. fish and mammals) have closed circulatory systems
• What's an open circulatory system?

  - Blood isn't enclosed in blood vessels all the time (pumped directly into body cavities)

  - Some invertebrates (eg. insects) have open systems
• Describe the circulatory system of an insect

  - open circulatory system

  - have 1 main blood vessel (dorsal vessel)

  - tubular heart in abdomen pumps haemolymph (blood in insect) into dorsal vessel

  - dorsal vessel delivers haemolymph into haemocoel (body cavity)

  - haemolymph surrounds organs and eventually reenters heart via one-way valves (osita)

  - oxygen is delivered directly to their tissues via tracheae that connect to the outside
• What is the role and structure of arteries? is blood pressure high or low?


  - Arteries carry blood from the heart to the rest of the body

  - high blood pressure

  3 layers to wall:

  1. inner layer (tunica intima): thin layer of elastic tissue for stretch/recoil

  2. middle layer (tunica media): thick layer smooth muscle)

  3. outer layer (tunica adventitia): thick layer collagen/elastic tissue

  - thick and muscular walls have elastic tissue to stretch a recoil as the heart beats, which helps maintain high pressure and stops arteries from bursting

  - The inner lining (endothelium) is folded, allowing the artery to expand - this also helps maintain high pressure

  - narrow lumen

  - reduces surges in blood making flow more continuous

  
• What is the role and structure of the veins? is blood pressure high or low


  - carries blood from body to heart

  - low blood pressure

  - thin walls of smooth muscle, elastin and collagen

  - valves to stop back flow of blood

  - wide lumen

  - only the pulmonary veins carry oxygenated blood, this goes from the lungs to the heart
• What is the role and structure of the capillaries? is the blood pressure high or low?


  - sit of exchange of molecules

  - connect arterioles and venules

  - lowest blood pressure

  - 1 cell thick

  - only endothelial cells (squamos)

  - short diffusion distance

  - small lumen

  - leaky capillaries (pores in capillaries)
• What is the structure of arterioles?

  - Much smaller than arteries

  - They have a layer of smooth muscle, but less elastic tissue than arteries

  - The smooth muscle allows them to expand and contract, thus controlling the amount of blood flowing to the tissues
• What function do arterioles have

  vasoconstriction and vasodilation
• where do arterioles lead to?

  capillaries
• what is the function of elastic tissue?

  allows blood vessels to stretch, maintains pressure in arteries so when it recoils it maintains the pressure while the heart relaxes
• what is the function of muscle tissue?

  strengthens arteries, and can contract and relax to control blood flow, particularly in the arterioles
• What is the role and structure of venules?

  - transport blood from capillaries to veins

  - few or no elastic fibres

  - large lumen

  - as blood flow is at low pressure after passing through the capillaries there is no need for muscular layer
• why do veins have a large lumen?

  so volume of blood delivered per unit time is the same as artery. also eases flow of blood.
• difference between veins and arteries?

  Veins have a thinner elastic and muscle fibres
• what do capillaries not have?

  tunica media or externa

  (no elastic/muscle tissue)
• What are the contents of blood plasma

  - oxygen

  - CO2

  - water

  - glucose

  - minerals

  - urea

  - small proteins

  - amino acids

  - hormones

  - RBC's

  - WBC's

  - platelets
• What is tissue fluid and what is its role

  The fluid surrounding the cells and tissues which supply them with oxygen and nutrients
• What molecules are found in tissue fluid?

  - Water

  - Dissolved solutes

  - Very few white blood cells

  - Very few proteins

  - (red blood cells and platelets too big to get through capillary, platelets only present if capillary is damaged)
• Explain why tissue fluid does not contain erythrocytes

  Gaps between epithelium cells in capillary walls too small for erythrocytes to fit through. Erythrocytes are larger and cannot change shape to fit through gaps
• What is hydrostatic pressure

  - blood pressure generated by contraction of the ventricles

  - forces fluid out of the plasma into the tissue fluid
• What is oncotic pressure

  - water potential gradient

  - generated by the presence of proteins in a solution

  - fulling force

  - water molecules attracted to proteins and form H bonds which makes the water potential more negative (lower)
• How is tissue fluid formed?

  It's formed by pressure filtration:

  
  

  - The hydrostatic pressure in the capillaries (near the arteries) is greater than hydrostatic pressure of the tissue fluid. This forces fluid out of the leaky capillaries, forming tissue fluid

  - As fluid leaves the hydrostatic pressure decreases

  - Oncotic pressure is generated by plasma proteins in the capillaries which lower water potential

  - The water potential is lower by the venule end of capillaries due to fluid loss and a high oncotic pressure

  - This means some water reenters via osmosis

  
  

  - high hydrostatic pressure in capillaries forces fluids out as capillaries are leaky

  - fluids move down pressure gradient from high to low into tissue fluid by diffusion
• What is the lymphatic system?

  - collects excess tissue fluid that has leaked from the venules of capillaries and returns it to the bloodstream

  - once tissue fluid passes into lymph vessels its called lymph

  - fluid called lymph and is similar in composition to tissue fluid but contains more lymphocytes as these are produced in lymph nodes (the only proteins present are antibodies)

  - It supports the immune system by housing and transporting white blood cells to and from lymph nodes
• Describe the formation of lymph

  - some tissue fluid reenter the capillaries (95%) while some enters the lymph capillaries (5%)

  - lymph capillaries separate from circulatory system

  - larger molecules that are unable to pass through the capillary wall enter the lymphatic system as lymph

  - enter through small valves in the vessel wall

  - liquid moves along the larger vessels of this system by compression caused by body movement

  - any backflow prevented by valves

  - lymph eventually reenters the bloodstream through veins located close to the heart

  - any proteins that have escaped from the blood are returned to the blood via the lymph capillaries
• 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
• What is the function of the pulmonary vein and vena cava

  brings blood to the heart
• What is the function of the pulmonary artery and the aorta


  takes blood away from the heart
• What is the function of the coronary arteries

  surrounds the heart and supplies the heart with oxygen for aerobic respiration
• Describe the structure of cardiac muscle

  - consists of fibres that branch producing cross bridges which helps to spread the stimulus around the heart and ensure that the muscle can produce a squeezing action rather than a simple reduction in length

  - lots of mitochondria between myofibrils

  - muscle cells separated by intercalated discs which facilitate synchronised contraction

  - each cell has nucleus and is divided into contractile units = sacromeres

  
• What is systole


  contraction of the heart
• What is diastole


  relaxation of the heart
• Describe the atrial systole stage of the cardiac cycle


  - The ventricles are relaxed (ventricular diastole)

  - The atria contract (atrial systole), which decreases their volume and increases their pressure

  - This pushes the blood into the ventricles through the atrioventricular valves (tricuspid/bicuspid valves)