4.2.2 Circulation Flashcards
Why cannot large multicellular organisms rely on diffusion alone for gas exchange
Have a small SA:V
Diffusion distance between surface and most of the cells is too great
Ventilation
The movement of air in and out of the lungs
Using the movements of:
Rib muscles (intercostals)
Diaphragm
Table of action during inhalation and exhalation:
Intercostal muscles
Rbcage
Diaphragm
Volume of thorax
Pressure in thorax
Pressure in thorax
Air moves
Inhale:
Contract
Up and out
Down (contracts)
Increases
Decreases
Air—in
Exhale:
Relax
Down and in
Up, relaxes
Decreases
Increases
Air is drawn out
Gas exchange
Inhale: oxygen rich air into lungs—maintains steep conc grad between air in the alveoli and blood—O2 continuously diffuses into bloodstream
Exhale: CO2 rich air out of lungs—maintains steep conc grad between blood and air in the alveoli so CO2 continuously diffuses OUT of bloodstream into air in lungs
Double circulatory system
Pulmonary circulation carries blood from heart to lungs and back again—allows O2 and CO2 to be exchanged with the air in the lungs
Somatic/systemic circulation carries blood to respiring cells in all organs of your body and back again to the heart
Better than single circulation:
Faster (high pressure) delivery of oxygenated blood
More O2 for higher rate of respiration
Structure of heart
Vena cava deoxygenated blood from body—>right atrium—>right ventricle—>pulmonary artery deoxygenated blood to lungs
Pulmonary vein brings oxygenated blood from lungs—>left atrium—>left ventricle—>aorta beings oxygenated blood to the rest of the body
Right Left
Why is being born with a hole in the septum a problem
Oxygenated blood is mixed with deoxygenated blood from the RV
Less oxygen is delivered by the blood to the baby’s respiring cells—>cannot contract muscles effectively
Disadvantages of having an artificial pacemaker
Battery needs to be charged—minor operation—risk of anaesthetic and risk of infection
Chance of defected pacemaker—too fast/slow/could malfunction
Does not increase heart rate during exercise
Arteries, veins, capillaries
Arteries carry oxygenated blood
Veins carry deoxygenated blood
Capillaries connect them
Oxygen diffuses into body cells from the capillaries
Pulmonary artery and pulmonary vein are upside down
Artery structure
Thick muscular wall
Thick elastic wall
Smaller lumen (compared to vein)
Usually looking pretty circular in diagrams
Artery function
To carry blood at HIGH pressure, away from the heart and to the tissues and organs of the body
Vein structure
ThinNER wall
LargER lumen
Valves to PREVENT BACKFLOW
Vein function
Carry blood at LOW pressure from the tissues and organs of the body back to the heart
Capillary structure
Wall only 1 cell thick
Pores to allow exchange of substances by diffusion
Capillary function
Site of exchange of substances—O2, glucose, etc—at cells and and tissues
Substances carried by plasma in blood
Glucose—enters small intestine to respiring cells
CO2–enters respiring cells to lungs
Platelets
If skin is cut, exposure to air stimulates platelets and damaged tissue to produce chemical
Chemical causes the soluble protein FIBRINOGEN to change into insoluble protein fibres called FIBRN
Fibrin forms a network of fibres across a wound trapping RBCs—forms a clot—then a scab, protects the damaged tissue while new skin grows underneath
Fibrinogen—> fibrin
Clot
Mesh traps RBCs
CHD (circulation topic)
Blood reaches the cardiac muscle cells via the coronary artery
The lumen of the coronary arteries may become narrowed by a build up of fatty substances—including cholesterol on their walls
Called plaque, or atheroma
Why could blockage in the coronary artery cause heart to die
Blockage reduces blood flow
Less oxygen and glucose to heart cells/tissue
Cannot respire s cells die
Risk factors for CHD
Lack of exercise
High cholesterol diet
Smoking
Chronic stress
Older age
Treatment of CHD: statins
Drugs which slow the development of CHD
Reduces blood cholesterol levels—slows the rate at which fatty material is deposited in coronary arteries—reduces risk of heart attack
Tablets taken once a day
Treatment continues for life—stopping medication causes cholesterol levels rise in a few weeks
Treatment of CHD: surgery
Stent:
Small mesh tube
Supports artery’s inner wall
Reduces the chance that the artery will become narrow/blocked
Heart bypass:
Complex nad expensive procedure
Replaces affected coronary arteries with sections of vein from other parts of the body
Treatment of faulty heart valves
Some valves don’t close properly—causes backflow
Replacement valves:
Biological valves—usually from humans or pigs, last 12-15 years, immuno-suppressants are needed
Mechanical valves—made out of a synthetic material/metals such as titanium, increased risk of blood clotting - need anti-coagulants, last for a long time
Heart transplant
If patient has severe heart failure and medical treatments are not helping
Donor and patient—same tissue type to reduce risk of rejection—could wait a very long time for a suitable donor
Surgery under general anaesthetic
A heart-lung bypass machine will be used to keep oxygen rich blood circulating the body
Artificial heart transplant
Rare
Temporarily replace the heart
Expensive
Cause blood clots
Why does a transplant need to be carried out soon after a donor heart is identified
Heart tissue will start to decay very quickly—bacteria
It will not be respiring—more difficult to re-start beating
Main risks associated with heart transplants
Infection
Anaesthetic
Rejection
Why do patients have to wait a long time for a heart ransplant
Hard to find a close tissue match otherwise will be rejected
Shortage of donors
Many people waiting for transplants
