B8 - Transport In Animals Flashcards
Open circulatory system
Transport medium pumped straight into the body cavity (hamocoel).
Pumped under low pressure
The transport medium directly contacts cells
It does not rely on diffusion as concentration gradients can not be maintained.
Closed circulatory system
Can be double (human) or single (fish)
Enclosed in blood vessels
Transport medium does not come into contact with cells and tissues.
Transport medium travels under pressure
Substances leave and enter the blood via diffusion
Similarities between open and closed circulatory systems
Liquid transport medium
Require a pumping mechanism
Can be described as a “mass transport system”
Artery structure
Narrow lumen
Lining called endothelium
Thick elastic layer
Thick smooth muscle layer
Tough outer layer (collagen)
Thin lining (endothelium)
Why do arteries have a narrow lumen
To keep the blood under high pressure while being pumped around the body
Why do arteries have a thick elastic layer
Elastic fibres allow arteries to withstand the force of the blood pumped and stretch to take a larger volume. The elastic fibres recoil and return to their original length. This helps to even out the surges of blood pumped from the heart to give a continuous flow.
Arterioles (structure and function)
Arterioles link the arteries and the capillaries. They have more smooth muscle and less elastin in their walls than arteries. They constrict or dilate to control the flow of blood into individual organs.
Vasoconstriction in arterioles
When the smooth muscle in the arteriole contracts it constricts the vessel and prevents blood flowing into a capillary bed. This is vasoconstriction.
Vasodilation in arterioles
When the smooth muscle in the wall of an arteriole relaxes, blood flows though into the capillary bed. This is vasodilation.
Capillaries (structure and function)
The capillaries are microscopic blood vessels that link the arterioles with the venules. The Lumen of a capillary is very small (10 micrometers). Substances are exchanged through the capillary walls between the tissue cell and the blood. Many substances pass out of the capillaries into the fluid surrounding the cells.
How capillaries are adapted for their role
The total cross-sectional area of he capillaries is always greater than the arteriole supplying them so the rate of blood flow falls. The relatively slow movement of blood through capillaries gives more time for exchange of materials by diffusion between the blood and the cells.
The walls are a single endothelial cell thick, giving a very thin layer for diffusion.
Where do arteries carry blood to
Arteries carry blood away from the heart to the tissues of the body. They carry oxygenated blood except in the pulmonary artery and (during pregnancy) the umbilical artery.
Where do veins carry blood to
Veins carry blood away from the cells of the body towards the heart. Except in the pulmonary vein and the umbilical vein.
Veins (structure and function)
Veins do not have a pulse
The blood pressure in the veins is very low compared with the pressure in the arteries.
Medium sized veins have valves to prevent the back flow of blood.
The walls contain lots of collage and little elastic fibre
Veins have a wide lumen
Thin lining called endothelium.
Why do veins have a wide lumen
Because blood in the veins is transported at low pressure.
Venules (structure and function)
Venules link the capillaries with the veins. They have very think walls and a little smooth muscle. Several venules join to form a vein.
How does deoxygenated blood return to the heart
The majority of the veins have one way valves at intervals that prevent backflow.
Many of the bigger veins run between active muscles in the body. When the muscles contract they squeeze the veins, forcing the blood toward the heart.
The breathing movements of the chest act as a pump. The pressure changes and the squeezing actions move blood in the veins of the chest and abdomen towards the heart.
What does the endothelium do
The endothelium is in both the veins and the arteries, it is a thin lining that ensures the blood flows easily.
What flows into the right atrium
Deoxygenated blood through the vena cava at relatively low pressure
How thick is the muscle in the atria
Thin muscular walls
What happens when blood enters the right atria
Slight pressure builds up until the atria-ventricular valve (the tricuspid valve) opens to let blood pass into the right ventricle. When the atrium and ventricle are filled with blood the atrium contracts, forcing the blood into the right ventricle. Tricuspid valve then closes, preventing blood backflow.
What do tendinous cords do
They make sure the valves are not turned inside out by the pressures exerted when the ventricle contracts.
What happens when the right ventricle contracts
It pumps deoxygenated blood through the semilunar valves into the pulmonary artery, which transports it to the capillary beds of the lungs. The semilunar valves prevent the back flow of blood into the heart.
What enters the left atrium
Oxygenated blood from the lungs enters the left atrium from the pulmonary vein.
What happens when oxygenated blood enters the heart
As pressure in the atrium builds the bicuspid valve opens between the left atrium and the left atrium and the left ventricle so the ventricle also fills with oxygenated blood. When both are full the atrium contracts, forcing all the oxygenated blood into the left ventricle. The left ventricle then contracts and pumps oxygenated blood through semilunar valves into the aorta and around the body. As the ventricle contracts the tricuspid valve closes, preventing any back flow.
Why is the muscular wall of the heart much thicker than that of the right
The left side has to produce sufficient force to overcome the resistance of the aorta and the arterial systems of the whole body and move the blood under pressure to all the extremities of the body.
Why is the muscular wall of the right side much thinner than that of the left
Because the lungs are relatively close to the heart and so the heart has to pump blood a relatively short distance and only has to overcome the resistance of pulmonary circulation.
what is the septum of the heart
The septum is the inner dividing wall of the heart which prevents the mixing of deoxygenated and oxygenated blood.
Sino-atrial node
- sends out a wave of electrical excitation
- causes atria to contract
- non-conducting tissues stop impulses spreading to ventricles
The purkinje fibres
- spreads the wave of excitation and triggers ventricles to contract starting at the apex
Atrio-ventricular node
- picks up electrical activity from SAN
- imposes slight delay before stimulating bundle of His
The bundle of His
- bundle of conducting tissue.
- penetrates through the septum between ventricles
atrial systole
- the atria contract
- pressure in atria increases
- blood pushed into ventricles through the AV valves
The semi-lunar valve open
- ventricule pressure increases above aorta pressure
- SLV forced open
the AV valve closes
- pressure in the ventricles rises above the pressure in the atria (due to ventricular contraction)
- this cause AV valves to snap shut, preventing backflow of blood into atria
- this is the first noise made by the heart
Ventricular systole
- ventricles contract
- pressure in ventricles increase
- blood ejected from heart through semi-lunar valves
Diastole
- both atria and ventricles are relaxed
- blood enters atria
- pressure behind AV valves increases pushing them open
Semi-lunar valve closes
- ventricular pressure decreases below aortic pressure
- so SLV snap shut preventing backflow of blood
- this is the second noise made by the heart
A valve opens
- pressure in ventricles below pressure in atria
- causes AV valve to open allowing blood flow into ventricles
Electrocardiograms
- an ECG monitors the electrical activity of the heart
- sensors placed on the skin pick up electrical activity that has spread through tissues next to the heart
- the ECG converts the electrical excitation into a trace
P wave
Associated with atrial systole
QRS complex
Associated with ventricular systole
T wave
Associated with diastole
Ectopic heartbeat
- extra heartbeats that are out of normal rhythm. Most people have at least one a day. They are usually normal but they can be linked to serious conditions when they are very frequent.
Atrial fibrillation
- this is an example of an arrhythmia, which means an abnormal rhythm of the heart. Rapid electrical impulses are generated in the atria. They contract very fast up to 400 times a minute. However, they don’t contract properly and only some of the impulses are passed on the ventricles, which contract much less often. Therefore the heart wont pump blood effectively
Tachycardia
- when the heartbeat is very rapid, over 100 BPM. This is often normal, for instance when you exercise, if you are frightened or angry. If it is abnormal it may be caused by problems in the electrical control of the heart and may need to be treated by medication or by surgery.
>100BPM
Bradycardia
- when the heart rate slows down to below 60 BPM. Many people have bradycardia because they are fit. Training makes the heart beat slowly and efficiently. Severe bradycardia can be serious and may need an artificial pacemaker to keep the heart beating more steadily.
- <60BPM
Plasma
- yellow liquid
- carries wide variety of other components including dissolved glucose and amino acids, mineral ions, hormones, and the large plasma proteins including albumin, fibrogen, and globulins
- it transports red blood cells and white blood cells and platelets
Platelets
- fragments of megakaryocytes
- found in red bone marrow
- involved in blood clotting
Erythrocytes
- red blood cells
- carry oxygen
- biconcave shape
- no nucleus to carry more oxygen
- haemoglobin to bind to oxygen
Leukocytes
- White blood cells
- defend the body from pathogens
How is the movement of plasma and solutes determined?
- hydrostatic pressure inside the vessels (resulting from heart contractions)
- this pushes plasma and solutes out of the capillary
- once outside of the capillary, the fluid is then referred to as tissue fluid
- oncotic pressure is caused by plasma proteins that are to big to get out of the capillary
- it acts to push the tissue fluid back into capillaries
How is tissue fluid formed (at the arterial end of the capillary)
- hydrostatic pressure is greater than the oncotic pressure
- therefore water leaves the capillaries
- tissue fluid circulates around the cells and exchange takes place
How does tissue fluid get back into the capillaries at the venous end
- the oncotic pressure is now greater than the hydrostatic pressure
- fluid moves back into the capillaries carrying waste products
How is lymph formed?
- 10% of the liquid that leaves the blood vessels drains into a system of blind-ended tubes called lymph capillaries
- it is now known as lymph
How is lymph transported
- lymph capillaries join up to form larger vessels
- the fluid is transported through them by squeezing of the body muscles
What are lymph nodes
- along the lymph vessels are the lymph nodes.
- lymphocytes build up in the lymph node when necessary and produce antibodies
- lymph nodes intercept bacteria and other debris from the lymph, which are ingested by phagocytes in nodes.
How are erythrocytes adapted to transport oxygen
- erythrocytes have a biconcave shape, giving a larger surface area. This also helps them pass through narrow capillaries
- they have no nucleus so they can carry more haemoglobin.
- they contain haemoglobin which carries oxyegn
What is haemoglobin
- a globular protein
- gives blood the red pigment
- made up of four peptide chains, each with an iron-containing haemoglobin prosthetic group.
- each haemoglobin can bind to four oxygen molecules.
What is the reaction when haemoglobin binds to oxyegn
Haemoglobin + oxygen = oxyhaemoglobin
Hb + 4(O2) = oxyhaemoglobin
The reaction is reversible.
Positive cooperativity
- one oxygen moves into the erythrocytes of the haemoglobin molecule
- the arrangement of the haemoglobin molecule changes shape
- making it easier for the next oxygen molecule to bind.
- this also works the other way, once one oxygen molecule disassociates it becomes easier for the rest to do the same.
What is the oxygen dissociation curve
- the percentage saturation haemoglobin in the blood is plotted against the partial pressure of oxygen.
- shows the affinity of haemoglobin for oxyegn
- the curve goes up sharply due to positive cooperativity
- then it plateaus at the highest partial pressures of oxyegn because all the haemoglobin groups are bound to oxygen.
The effect of carbon dioxide on haemoglobin
- in active tissues with a high partial pressure of carbon dioxide, haemoglobin gives up its oxygen more readily. (Bohr effect)
- in the lungs where the proportion of carbon dioxide in the air is relatively low, oxygen binds to the haemoglobin molecules easily
Fetal haemoglobin
- haemoglobin in fetus’ has a higher affinity for oxygen than regular haemoglobin.
- as oxygen from the mothers blood needs to release into the fetus’ blood stream.
- fetal haemoglobin removes oxygen from the maternal blood as they move past each other
How is carbon dioxide transported
- 5% carried dissolved in the plasma
- 10%-20% is combined with the amino groups in the polypeptide chains of haemoglobin to form a compound called carbaminohaemoglobin
- 75%-85% is converted into hydrogen carbonate ions (HCO3-) in the cytoplasm of the red blood cells.
Chloride shift
- the negatively charged hydrogen carbonate ions move out of the erythrocytes into the plasma by diffusion.
- negatively charged chloride ions move into the erythrocytes.
- this maintains the electrical balance of the cell
