Chapter 8 Keyconcepts Flashcards
Why do animals need specialised transport systems?
- diffusion distances increases as the organism gets bigger. Diffusion would be so slow that organism wouldn’t survive
- high metabolic demand so made lots of waste and need lots of oxygen and food. Diffusion distances too great and not enuf to supply the quantities needed
- SA V gets smaller so amount of SA avail to absorb or remove substances decreases
- molecules eg enzymes made in one place but needed in another
- food digested in one organ system but needed in another place
- waste products of metabolism needs to be removed form cells and transported to excretory organs
Three things most circulatory systems have in common
Liquid medium that circulates around the blood
Vessels that carry the transport medium
Pumping mechanism to move the fluid around the system
Features of an open circulatory system
- v. Few vessels to contain the transport medium
- pump straight from heart to open body cavity aka haemocoel. When here the transport medium is under low pressure.
- medium in direct contact with tissue and cells and exchange takes place here.
- medium back to the heart through an open ended vessel
What animals tend to have open ended circulatory systems?
Invertebrates inc. most insects and some molluscs
Features of a closed system
- Blood in blood vessels
- blood Doesn’t come into direct contact with cells of the body
- Heart pumps blood under high pressure and relatively quickly
- blood returns directly to the heart
- substances leave and enter blood by diff thru walls of the bv
- can adjust the vol going to particular fissure by narrow/widen bv
- most closed circ systems have blood pigment that carries respiratory gases
Animals that have a closed circulatory system
Echinoderms eg sea urchins and star fish
Cephalopod molluscs including the Octopods and squid
Annelid worms incl. earth worms
All vertebrae
Animals with single closed
Fish
Annelid worms
Features of a single closed system
-Blood travels only once through the heart per complete circulation of the body
-blood passes through two sets of capillaries
First exchanging O2 and CO2
second in the different organ systems, substances exchanged entre blood and cells
- blood return to heart under v.low pressure as it passed through 2 sets of v. Narrow vessels
- limits the efficiency of the exchange so activity level tends to be quite low.
Features of a double circulatory system
Enable birds and most mammals that are v. Active land animals, to maintain their own body temperature
- most efficient of the two
- passes through one cap network so relatively high pressure and fast flow of blood can be maintained
- blood travels through the heart twice per circuit of the body
- blood pumped from heart to lung to pick up O2 and unload CO2 then returns to heart
- Blood flows through heart and is pumped out to travel all around the body before returning to heart again
Artery
- carry blood away
- carry ox blood except pulmonary artery and the umbilical artery
- high pressure
- walls have elastic fibre to withstand the force of the bp out of the heart and stretch to take a larger volume. Recoils in-between heart contractions to even out the surges of blood pumped out of the heart to give a continuous flow but can’t eliminate pulse when heart contracts
-smooth muscle
- collagen limits the amount by which the arteries stretch by
- endothelium is smooth so blood flows easily over it
Arterioles
Link artery to capillaries
Have more smooth muscle
less elastin as they have little pulse surge
Can constrict or dilate to control blood flow into individual organs
Ways in which the Capillaries are adapted for their role
- large SA for diff of substances in n out of blood
- walls are a single endothelial cell thick so v. Thin layer for diffusion
- total cross sectional area is greater than the arteriole supplier so rate of blood flow falls. Relative slow movement of blood thru Capps gives more time for exchange
Veins
Doesn’t have a pulse
Surges lost when blood passes the narrow Capps
Up to 60% of blood vol is in ur veins at anyone time
Low pressure and needs to move against gravity
Medium size veins have values to prevent backflow of blood
- lots of collagen
- little elastic fibre
- vessels have a wide lumen
Venules
Link Capps with veins
Very thin walls with just a little smooth muscle
Several venules join to make a vein
3 adaptation of the body to overcome the low pressure but have to move against gravity problem
- breathing movement of the chest acts as a pump. Pressure changes and squeezing actions move blood in the veins of chest and abdomen towards the heart
- many bigger veins run through big active muscles eg arms and legs. When muscle contract they squeeze the veins forcing blood towards the heart. Valves prevent backflow when muscles relax
- one way valves at intervals. These are unfolding of the inner lining of the vein. When blood flows in direction of the heart valves open, if it starts to flow backwards valves close
Functions of the blood
-contributes to maintaining steady blood pressure
-acts as a buffer, minimising pH changes
-transport
Platelets to damaged areas
Digested food to the small intestine
O2 to and CO2 from respiring cells
Nitrogenous waste products from cells to the excretory organs
Chemical messages (hormones)
Food molecules from storage compounds to cells that need them
Cells and antibodies involved in immune response
Blood composition
55% plasma
45% rbc, platelets, leucocytes
What does it mean if the lymph nodes are enlarged
Sign that the body fighting off an invading pathogen The sites of the major lymph nodes are Neck Armpits Stomach Groin
Adaptations of the rbc for transporting oxygen
Bioconcave
- larger SA than a simple disc structure or sphere. This increasing SA avail for diff
- helps rbc pass through narrow capp
Lack of nucleus
- by the time mature rbc enter the circulation they have lost their nuclei , for max haemoglobin
- limits their life to 120 days
Transport of O2 from lung to tissue
When rbc enter Capp in lungs , low O2 levels so steep con grad entre rbc and air in the alveoli
- O2 into rbc and bind with Hb. In positive cooperativity as soon as one O2 binds to haem group so molecule changes shape so easier for next oxygen molecules to bind.
- steep o2 con maintained until fully saturated. because o2 binded to the haem so free o2 stays low
- at the tissue the o2 con in the cyto is lower than the rbc so O2 out down a steep con grad. When first is removed, change of shape so easier for next ones to be removed
Bohr shift
As pp of CO2 increases, haemoglobin gives up oxygen more easily and graph shift right
Importance of the Bohr effect
- at active cells with higher pp of CO2 haemoglobin gives up O2. More easy
- at the lung where pp CO2 in alveoli air is relatively low, ox binds to haemo molec easily
Fetal
Haemoglobin
In the placenta, mum ox blood runs close to child deox blood.
Need high affinity or die. Graph shift left.
Three ways of transporting CO2
5% dissolved in plasma
10-20% combined with amino group in the Haemoglobin peptide change to make carboamimohaemoglobin
75-85% converted into hydrogen carbonate ions
Reason for the Chloride shift
Maintain electrical balance when HCO3-
What happens from the cell to the lung in terms of CO2 transport
Low CO2 con at the lung .
HCO3- back into rbc and reacts with H+ to make more carbonic acid . Cl- out of rbc into plasma down electrochemical gradient
Carbonic Anhydrase catalyses carbonic acid to CO2 and h20
How does Haemoglobin act as a buffer
Reacts reversibly with the H+ to make Haemoglobinic acid preventing pH change
Role of the coronary artieries
Supply cardiac muscle with ox blood cuz heart need to contract and relax at all times
Role of the inelastic pericardial membranes
Prevent heart from over-distending with blood
AVV aka
Tricuspid valve
What do the tendinous chords do?
Ensure values aren’t turned inside out by the pressure made when ventricle contracts
Role of the semilunar value
Prevent backflow from pulmonary artery into heart
Why is the left side of the heart thicker than the right?
The left pumps to the body. Has to make enough force to overcome the resistance of the aorta and the arterial systems of the whole bond and move the blood under pressure to all the extremes of the body
Role of the September
Inner dividing wall of the heart which prevents the mixing of deox and ox blood
Why does contraction start at the apex of the heart ?
Allows for more efficient emptying of the ventricles
