Mass transport in animals Flashcards
Mass transport what is it
In large multicellular organisms, mass transport systems are needed to carry substances between exchange surfaces and the rest of the body and between parts of the body.
Most cells are too far away from the exchange surface/each other for diffusion alone to maintain the composition of tissue fluid within suitable metabolic range.
Mass transport maintains final diffusion gradients bringing substances to and from cells. It also helps to maintain relatively stable immediate environment of cells that is tissue fluid.
The circulatory system
Closed double circulatory system - there are two circuits where blood passes through twice
Pulmonary circulation
Deoxygenated blood in right side pumped to lungs
Oxygenated blood returns to the left side of the heart
Systemic circulation
Oxygenated blood in left side pumped to tissues/organs of the body
Deoxygenated blood returns to the right side
Why is circulation important for mammals
Prevents mixing of oxygenated and deoxygenated blood so that the blood pumped to the body is fully saturated with oxygen and is efficiently delivered for respiration
Blood can be pumped at a higher pressure (after being lowered from lungs) so that substances can be taken to and removed from body cells more quickly and efficiently
Coronary arteries
Deliver oxygenated blood to cardiac muscles
Blood vessels entering and leaving heart
Aorta - takes oxygenated blood from the heart to respiring tissues
Vena cava - takes deoxygenated blood from respiring tissues back to the heart
Blood vessels entering and leaving lungs
Pulmonary artery - takes deoxygenated blood from the heart to the lungs
Pulmonary vein - takes oxygenated blood from the lungs to the heart
Blood vessels entering and leaving kidneys
Renal arteries - takes deoxygenated blood to the kidneys
Renal veins - takes deoxygenated blood to the vena cava from the kidneys
Structure of the heart related to its function
Atrioventricular valves that prevent backflow of blood from the ventricles to the atria.
Semi lunar valves that prevent backflow of blood from arteries to ventricles
Left has a thicker muscle wall which generates a higher blood pressure as oxygenated blood has to travel a greater distance around the body
Right has a thinner muscle wall which generates a lower blood pressure as deoxygenated blood has to travel a shorter distance to the lungs where high pressure would damage alveoli.
Structure of arteries related to its function
Carry blood from the heart to the rest of the body at a high pressure.
Thick smooth muscle layer that contracts, pushing blood flow along and maintains the blood flow/pressure
Elastic tissue layer that stretches as the ventricle contracts (when under high pressure) and recoils when the ventricle relaxes (when under low pressure). It also reduces pressure surges.
Thick wall that can withstand high pressure and prevents the artery from bursting
Smooth, thin endothelium reduces friction
Narrow lumen increases and maintains the high blood pressure.
Structure of arterioles related to its function
Division of arteries to smaller vessels which can direct blood to different capillaries/areas.
Thicker muscle layer than arteries - constricts to reduce blood flow by narrowing the lumen, dilates to increase blood flow by enlarging the lumen.
Thinner elastic layer as there are lower pressure surges
Structure of veins related to its function
Carry blood back to the heart under lower pressure
Wider lumen than arteries
Very little elastic and muscle tissue
Valves to prevent backflow of blood
Contraction of skeletal muscles squeezes veins, maintaining blood flow
Structure of capillaries related to function
Thin walls (one cell thick) that provide a short diffusion pathway
Capillary bed is made of a large network of branched capillaries for an increased SA:V, rapid diffusion
Narrow lumen which reduces flow rate so more time for diffusion to occur
Capillaries permeate tissues (short diffusion pathway)
Pores in walls between cells which allows substances to escape
Importance of capillaries
Provides important exchange surfaces within the circulatory system as capillaries branch between cells
Capillaries allow the efficient exchange of gases and nutrients between blood and tissue fluid
Tissue fluid what is it
Tissue fluid is the fluid surrounding cells/tissues
It provides respiring cells with substances such as water, glucose, amino acids and oxygen.
It enables waste substances to move back into the blood such as urea, lactic acid and carbon dioxide
The formation of tissue fluid
At the arterial end of the capillaries, fluid is forced out of capillaries as there is a higher hydrostatic pressure inside capillaries (due to contraction of the left ventricle) than tissue fluid (net outward pressure)
Large plasma proteins remain in the capillary as they are too large to leave
Return of tissue fluid to circulatory system
Towards the venule ends of capillaries hydrostatic pressure reduces as fluid leaves capillary
Due to water loss, an increasing concentration of plasma proteins lowers the water potential in the capillary below the water potential of the tissue fluid.
As a result, water reenters the capillaries from the tissue fluid by osmosis down a water potential gradient
Excess water is taken up by the lymphatic system and is returned to the circulatory system.
Contraction of the atria (atrial systole)
Atria contract, decreasing volume and increasing pressure inside the atria.
Semilunar valves are shut
Atrioventricular valves are forced open
Blood is pushed into ventricles
Contraction of the ventricles (ventricular systole)
Ventricles contract from bottom up, decreasing volume and increasing pressure inside ventricles
Semilunar valves forced open
Atrioventricular valves shut
Blood is pushed out of heart through arteries.
Relaxation of heart (diastole)
Atria and ventricles relax, increasing volume and decreasing pressure inside chambers
Blood from veins fill atria (slightly increasing the pressure inside atria) and flows passively to ventricles
Atrioventricular valves open
Semilunar valves shut
Cardiac output formula
Cardiac output = stroke volume (dm3) x heart rate (min-1)
Coronary heart disease
Often associated with atherosclerosis and atheroma formation
Atheroma’s cause narrowing of coronary arteries which restricts blood flow to heart muscle supplying glucose, oxygen etc
Heart respires anaerobically, less ATP is produced, not enough energy for heart to contract, lactate is produced which damages heart tissues
Risk factors that increase probability of getting disease
Age
Diet high in salt or saturated fat
High consumption of alcohol
Stressful lifestyle
Smoking cigarettes
Genetic factors
High blood pressure increases risk of damage to endothelium of artery wall which increases risk of atheroma which can cause blood clots (thrombus)
Haemoglobin what is it
The haemoglobin’s are a group of chemically similar molecules found in many different organisms (chemical structure may differ between organisms)
Found in red blood cells (have no nucleus so it can contain more haemoglobin, biconcave shape for rapid diffusion)
Quaternary structured protein - made of 4 polypeptide chains. Each polypeptide chain contains a haem group containing an iron ion (Fe2+) which combines with oxygen
How oxygen is transported in the blood
Haemoglobin in red blood cells transports oxygen (as oxyhaemoglobin)
Haemoglobin can carry 4 oxygen molecules - one at each haem group
In the lungs, at a high partial pressure of oxygen, haemoglobin has a high affinity for oxygen and so oxygen readily loads/associates with haemoglobin
At respiring tissues, at a low partial pressure of oxygen, oxygen readily unloads/disassociates from haemoglobin. Also, concentration of CO2 is high, increasing the rate of unloading
Oxyhaemoglobin disassociation curves
At high partial pressure of oxygen, haemoglobin is saturated with oxygen
At low partial pressure of oxygen, haemoglobin is less saturated with oxygen
After the 1st oxygen molecule binds, the shape of haemoglobin changes in a way that makes it easier for the 2nd and 3rd oxygen molecules to bind too i.e. haemoglobin has a higher affinity for oxygen
After the 3rd molecule binds, and haemoglobin starts to become saturated, the shape of haemoglobin changes in a way that makes it harder for other molecules to bind too.
The Bohr effect - effect of carbon dioxide concentration
When rate of respiration is high eg during exercise, more carbon dioxide is released
High partial pressure of CO2 lowers pH and reduces haemoglobins affinity for oxygen as haemoglobin changes shape, so the rate of oxygen unloading increases
This is advantageous because it provides more oxygen to muscles/tissue for aerobic respiration. Oxygen haemoglobin curve shifts to the right.
Curve shifts
Curve shifts left: haemoglobin has a higher affinity for oxygen (so loads oxygen readily but unloads it less easily). More oxygen associates with haemoglobin more readily (in the lungs) but dissociates less easily.
Curve shifts right: haemoglobin has a lower affinity for oxygen (so loads oxygen less readily but unloads it more easily). Oxygen dissociates from haemoglobin more readily to respiring cells, associates less easily. Advantageous to organisms such as those with a high rate of respiration.
