Circulatory system Flashcards
Describe closed double circulatory system
- Closed: All blood remains within blood vessels
- Double circulation: Blood flows through heart twice in each circuit. 1st blood-lungs 2nd blood-body
Why is double circulatory system required?
To manage pressure of blood flow as different parts of the body require blood at different pressures
Why do lungs need low-pressure blood?
- Reduces damage to capillaries around alveoli
- Reduces speed = more time for gas exchange
Why does the body need high-pressure blood?
Make sure blood reaches every cell = all respiring cells receive O2
Main blood vessels
- Coronary artery: Supply blood to heart muscles
- Vena cava: Body-heart
- Aorta: Heart-body
- Pulmonary artery: Heart-lungs
- Pulmonary vein: Lungs-heart
- Renal artery: Oxygenated blood in
- Renal vein: Deoxygenated blood out
Adaptation of cardiac muscle
- Walls of the heart are thick muscle
- Myogenic: Can contract/relax without nervous/hormonal stimulation as long as there is O2/glucose supply
- Never fatigues as long as 02/glucose supply
Function of coronary artery
- Supply cardiac muscle with oxygenated blood
- Brach of aorta
- If become blocked = cardiac muscle doesn’t receive O2 = no respiration = cells die = myocardial infraction = heart attack
4 chamber of the heart
Right atrium - Left atrium
Right ventricle - Left ventricle
Features of atria
- Thinner walls as only need to contract to pump to ventricles
- Elastic walls as they stretch as blood enters
Features of ventricles
- Thicker walls to enable more contractions as need to pump blood further distances of lungs and heart
Features of right ventricle
- Thinner muscle compared to left ventricle
- Pumps blood to lungs = need lower pressure contractions = prevent damage to capillaries + slow flow for more time for gas exchange
Features of left ventricle
- Thicker muscle compared to right ventricle = larger contractions
- Pumps blood to body = higher pressure = ensure blood reaches all respiring cells
Describe the 2 heart veins
VENA CAVA:
- Deoxygenated blood from body to right atrium
PULMONARY VEIN:
- Oxygenated blood from lungs to left atrium
Describe the 2 heart arteries
PULMONARY ARTERY:
- Deoxygenated blood from right ventricle to lungs
AORTA:
- Oxygenated blood from left ventricle to body
3 valves in the heart
- Semi-lunar: Aorta + pulmonary artery
- Bicuspid: Left atria + ventricle
- Tricuspid: Right atria + ventricle
Adaptations of valves
- Open when there is higher pressure behind valve
- Close when there is higher pressure in front of valve = prevent backflow
Adaptations of septum
- Separates oxygenated/deoxygenated blood
- Maintains high concentration of oxygen by not diluting with deoxygenated in oxygenated blood= maintained concentration gradient to diffuse at respiring cells
4 blood vessels involved in exchange
- Vein
- Artery
- Arteriole
- Capillary
Describe structure of artery
- Muscle layer: Thicker than vein= constrict/dilate to control blood volume
- Elastic layer: Thicker than vein= maintain blood pressure + stretch in response to heartbeat
- Wall thickness: Thicker than vein= prevent bursting under high pressure
- No valves
Describe structure of arteriole
- Muscle layer: Thicker than artery to help restrict blood flow into capillaries
- Elastic layer: Thinner than artery as pressure is lower
- Wall thickness: Thinner than artery as pressure is lower
- No valves
Describe the structure of vein
- Muscle layer: Thin= doesn’t control flow
- Elastic layer: Thin= pressure is lower
- Wall thickness: Thin= pressure is lower + low risk of bursting + flattened vessels help flow of blood to heart
- Valves to prevent backflow
Describe structure of capillary
- No muscle layer
- No elastic layer
- Wall thickness: 1cell thick= short diffusion
- No valves
3 stages of the cardiac cycle
1) Arterial/ventricular diastole
2) Arterial systole
3) Ventricular systole
Explain arterial/ventricular diastole
- Atrial + ventricular muscles relax = volume increase
- Blood enters atrium via vena cava/pulmonary vein = increase pressure in atrium
Explain atrial systole
- Walls of atrium contract = increase pressure = atrioventricular valves open + blood flows into ventricles
- Ventricles still in diastole
Explain ventricular systole
- Blood from atrium emptied into ventricle
- Wall of ventricle contracts = increases pressure = atrioventricular valves close + semi-lunar valves open
- Blood is pushed out of ventricles into aorta/pulmonary artery
Describe a blood pressure change graph
ATRIUM LINE:
- Atrial systole: Pressure slightly increases but then decreases as blood flows into ventricle
- AV valve closes: Ventricular pressure is slightly more than atrial
- AV valve opens: Atrial pressure is slightly more than ventricular
VENTRICLE LINE:
- Ventricular systole: Pressure increases greatly as thick walls contract but then slight decrease when blood flows off to body
- Ventricular diastole: Ventricle relaxes = volume increases = pressure decreases so it drops greatly
AORTIC LINE:
- SL valve open: Ventricular pressure is slightly more than aortic
- SL valve closes: Aortic pressure is slightly more than ventricular
Describe the structure of haemoglobin
- Globular
- Quaternary structure protein
- 4 polypeptide chains
- Each chain has a haem group with Fe2+ which the O2 binds to
Function of haemoglobin
It is inside red blood cells and O2 binds to haem groups and carried to respiring tissue
Factors that affect oxygen-haemoglobin binding
1) PP of O2
2) PP of CO2
3) Saturation of haemoglobin with O2
How does PP of O2 affect binding?
- PP increases = haemoglobin affinity for O2 increases = more binding
- PP low = O2 unloaded
How does PP of CO2 affect binding?
BOHR EFFECT
- PP increases = conditions become acidic = haemoglobin shape changes = haemoglobin affinity reduced = O2 unloaded
How does saturation of haemoglobin with O2 affect binding?
COOPERATIVE BINDING
- It is hard for the first oxygen molecule to bind
- Binding = changes the tertiary structure to make it easier for the second and third molecules to bind as it creates a binding site
- It is then slightly harder for the fourth oxygen molecule to bind because there is a low chance of finding a binding site.
Why does O2 bind in the lungs?
- PP of O2 high + PP of CO2 low = high affinity
- Cooperative binding = binding subsequent molecules is easier
Why does CO2 unload in respiring cells?
- PP of O2 low + PP of CO2 high = low affinity
Describe oxyhaemoglobin dissociation curve
- Saturation against PP of O2
- Curve to the left = higher affinity
- Curve to the right = lower affinity
Describe oxyhaemoglobin dissociation curve for fetus
- Curve to the left = higher affinity
- At same PP it has higher saturation
- Advantageous: Cannot ventilate so O2 intake is through mother’s blood via placenta so must have a higher affinity to grab the O2 from mother’s haemoglobin
Describe oxyhaemoglobin dissociation curve for llama
- Llamas live at high altitudes = lower PP of O2
- Curve to the left = higher affinity = at same PP it has higher saturation
- Advantageous: In a low PP O2 environment it can load O2
Describe oxyhaemoglobin dissociation curve for bird
- Curve to the right = lower affinity
- Advantageous: Have faster metabolism as they are flying = muscle contractions = need higher supply of O2 for aerobic respiration so lower affinity = readily unload O2
Describe oxyhaemoglobin dissociation curve for worm
- Live underground = lower PP of O2
- Curve to left = higher affinity
- Advantageous: Can load O2 in low PP environment
What is tissue fluid?
- Liquid that surrounds the cells
- Consists of water, glucose, ions, O2
Describe how tissue fluid is formed
- Blood flows from the arterioles to the capillaries = smaller diameter = high hydrostatic pressure
- Water forced out from high hydrostatic pressure - low hydrostatic pressure
Describe how tissue fluid is reabsorbed
- Larger molecules remain in capillary = low WP at venule end
- Hydrostatic pressure decreases at venule end
- Water re-enters via osmosis from high WP outside to lower WP inside
What happens to tissue fluid that is not reabsorbed?
- Equilibrium reached = no more osmosis
- Rest of tissue fluid absorbed by lymphatic system
Role of the heart in formation of tissue fluid
- Contraction of ventricles = high blood/hydrostatic pressure
- Forces blood out of capillaries
