M3 Heart and Circulation Flashcards
What is meant by a double-circulatory system?
Blood travels through the heart twice for a complete circuit and is a closed system.
What is the name of the artery that goes to the liver?
The hepatic artery (hepatic vein goes away)
What is the name of the artery that goes to the kidneys?
The renal artery (renal vein goes away)
What are the names of the two Vena Cavas and where do they come from?
Inferiror Vena Cava - lower body
Superior Vena Cava - head and shoulders
What is the name of the artery that goes to the lungs?
Pulmonary artery (pulmonary vein returns blood)
Name the two types of valves
Atrioventricular and Semilunar
What is the name of the atrioventricular valve on the left side of the heart called?
The bicupsid valve
What is the name of the atrioventricular valve on the right side of the heart called?
Tricupsid Valve
What are always attached to valves? What do they do?
Tendons - they prevent the valves from opening in the wrong direction.
What are the names of the semilunar valves in the heart?
Aortic valve and pulmonary valve
What is the name of the thick piece of muscle between the left and right ventricle called?
The septum
What is the purpose of valves?
To prevent backflow
What are the names of the stages of the cardiac cycle?
Diastole, Atriole systole and Ventricular systole
What happens in Diastole?
- Ventricles and atria relax
- Vol increases, pressure decreases.
- Greater pressure in pumonary artery and aorta closes SL valves.
- Atria fill with blood due to pressure in pulmonary veins and vena cava.
- Ventricles fill passively as the AV valves open.
What happens in Atrial Systole?
- Both atria contract
- Volume of atria decreases, pressure increases
- High pressure in atria keeps AV valves open
- Blood flows into ventricles to fill them completely
What happens in Ventricular systole?
- Atria relax, both ventricles contract
- Pressure in ventricles increases, volume decreases
- Pressure in ventricles close AV valves and open SL valves so blood flows into pulmonary artery and aorta
What causes the ‘lub dub’ sound specifically?
‘lub’ = AV valves closing
‘dub’ = SL valves closing
What is the acronym to remember the order of valves opening and closing in the heart?
COCO
(bottom are AV, top are SL)
Describe the inner, middle and outer layer of arteries
INNER - endothelium
MIDDLE - elastic fibres, smooth muscle, collagen fibres
OUTER - Mostly collagen fibres, some elastic
Describe the inner, middle and outer layer of veins
INNER - endothelium
MIDDLE - same as arteries but thinner
OUTER - same as arteries but thinner
How are arteries adapted to their function?
Collagen = strength
Elastic tissue = stretch and recoil to maintain pressure
Smooth muscle = contract to restrict bloodflow
Endothelium = Smooth to reduce friction
How are veins adapted to their function?
Valves = stop backflow
Wide lumen = aids blood flow
Thinner walls = no need to stretch and recoil
Endothelium = Smooth to reduce friction
Movement of blood aided by contractions of skeletal muscles
How are capillaries adapted to their function?
1 red blood cell thick - short diffusion distance
Numerous - highly branched (high SA)
Spaces between endothelial cells
What do arterioles do and how are they adapted to function?
Carry blood from arteries to capillaries.
- Less elastic tissue (lower pressure)
- More muscle to control flow to capillaries
What do the following terms mean?
- Partial Pressure of O2
- Affinity
- Association
- Dissociation
- % Oxygen saturation
Partial Pressure of O2 = a measure of O2 concentration
Affinity = Tendency to combine with
Association = loading or binding with
Dissociation = unloading or unbinding with
% Oxygen saturation = % of bound oxygen molecules compared with maximum
Describe the structure of haemoglobin
A protein at quaternary level structure - made of 4 polypeptide chains (2 alpha and 2 beta). Each polypeptide contains a prosphetic haem group (Fe2+).
What happens with haemoglobin at gas exchange surfaces?
mention: pp of O2, pp of CO2, affinity for oxygen and the result.
High PP of O2
Low PP of CO2
High affinity for O2
Result: Haemoglobin associates with O2
What happens with haemoglobin at respiring tissues/capillary beds?
mention: pp of O2, pp of CO2, affinity for oxygen and the result.
Low PP of O2
High PP of CO2
Low affinity for Oxygen
Result: Haemoglobin dissociates with O2
How does the Partial Pressure of CO2 affect the affinity of haemoglobin for oxygen?
CO2 dissolves into plasma, increasing acidity. Haemoglobin protein changes shape, reducing affinity for oxygen so O2 is dissociated.
Explain the shape of the oxygen dissociation curve, referring to binding of O2 molecules to haemoglobin.
Shallow initial gradient - it is difficult for the first O2 molecule to bind due to the shape of the Hb.
Sudden steep gradient - binding of the first O2 molecule causes a change in shape of Hb which makes it easier for the second and third O2 molcules to bind.
Gradient reduces and graph flattens - It is difficult for the 4th O2 molecule to bind because there are fewer available Hb sites to bind to.
A small change in partial pressure of O2 leads to a _____ change in O2 saturation. This enables O2 to be ______ to respiring cells and ________ in the lungs.
large
unloaded
loaded
Explain how the shape of the oxygen dissociaion curve relates to transport of O2 in the body.
End: ppO2 is high in the lungs. Hb has a high affinity and O2 associates readily. O2 saturation is high.
As haemoglobin travels through blood vessels, very little O2 is lost.
Beginning: ppO2 is low in respiring tissues. Hb has a low affinity. O2 dissociates readily, O2 saturation is low.
What are the golden rules about shifting oxygen dissociation curves to the right and left? What organisms are these for?
Shift to right = decreased affinity. Oxygen dissociates more easily but associates less easily for organisms with high metabolic rate (e.g. birds and shrews)
Shift to left = increased affinity. Oxygen associates more easily but disociates less easily for organisms living in low O2 environments (e.g. lugworm)
When the oxygen dissociation curve is shifted to the right, at every ppO2, the affinity is _____, therefore % saturation is ______.
reduced
reduced
Explain how tissue fluid forms. Where does it form?
High hydrostatic pressure due to contraction of ventricles (which is greater than the effect of water potential gradient) in ateriole end of capillary forces fluid and dissolved substances through gaps in the capillary wall/endothelium.
How does water return to the blood?
Lower hydrostatic pressure in venule end of capillary due to greater distance from heart and loss of fluid, so effect of water potential greater than hydrostatic presure.
Lower water potential in capillary due to presence of plasma proteins and loss of fluid. Water returns to capillary from tissue fluid by osmosis down a water potential gradient.
What remains in the capillaries and why?
Blood cells and plasma proteins because they are too large to leave.
How does liquid form in the lymphatics? How do dissolved substances/proteins return to the blood?
Valves allow proteins, secreted by cells, to leave tissue fluid and enter the lymph. Excess fluid drains through valves into lymphatics. Lymph returns to blood via subclavian veins.
What does failure to remove proteins from tissue fluid via lymphatics lead to?
Oedema
What is the purpose of tissue fluid?
- Bathes the cells
- Cells exchange materials with tissue fluid by diffusion/facilitated diffusion
- Provides stable environments with the conditions cells need to function
Blood is a specialised ______. Blood cells are suspended in a liquid called _____, which contains many dissolved substances such as _____ and _____.
Tissue
plasma
salts and gases
Does tissue fluid contain:
- red blood cells
- white blood cells
- platelets
- large proteins
No red blood cells, platelets or large proteins
Some white blood cells
What percentage of tissue fluid returns to the blood?
90%
10% drains into lymphatics and returns to blood at subclavian veins.
The tissue fluid that drains into lymph vessels have a similar composition to tissue fluid except…
- less oxygen and glucose
- more carbon dioxide
- more fats (from small intestine)
- contains proteins secreted by body cells
Lymph flows very ____. Lymph vessels contain _____ and rely on _______ of _______ muscles to ensure flow. Lymph nodes are also found at intervals, which contain ________ (both phagocytic and antibody producing).
Slowly
Valves
contraction
skeletal
lymphocytes
