8. TRANSPORT IN MAMMALS Flashcards
How is the mammalian cardiovascular system a closed system
blood always remains within vessels
Why is the mammalian cardiovascular system called a double circulatory system
blood flows twice through the heart in one complete circuit.
The function of arteries
to transport blood swiftly and at high pressure to the tissues
Layers of the arteries
- tunica intima (squamous epithelium) (minimises friction with moving blood)
- tunica media (elastic fibres, collagen fibres, smooth muscle)
- tunica externa (collagen fibres and some elastic fibres)
Arteries near the heart contain more _____ and arteries away from the heart contain less elastic tissue and more _____ in the tunica media
more elastic tissue
smooth muscle
The distinctive characteristics of an artery
strength and elasticity
Role of elastic fibres in artery
- allow the wall to stretch as pulses of blood at high pressure surge through, making the artery wider and reducing the pressure
- allow the wall to recoil inwards as the pressure drops, making it narrower and raising the pressure
- reduces the likelihood of artery bursting
What is a pulse
The stretching of the arteries due to the high pressure of the blood passing through it with each surge of blood from the heart
Significance of arterioles
- control the volume of blood entering capillaries and thus tissues
- reduce the pressure of blood going into the capillary (preventing oedemas)
The function of the capillaries
to take blood as close as possible to the all the cells, allowing rapid transfer of substances between the cells and blood
What places do capillaries not form a capillary bed
- cornea
- cartilage
What allows some components of the blood to seep through into the spaces between the cells in all the tissues of the body
tiny gaps between the individual cells that form the endothelium
Functions of veins
to return blood to the heart
Movement of blood in veins
- pressure in veins is produced by the contraction of skeletal muscles close to it
- semilunar valves prevent backflow of blood away from heart
Role of plasma proteins in blood
- regulate osmotic potential
- regulate pH
- some, such as fibrinogen, have a role in blood clotting
Function of haemoglobin in red blood cells
to transport oxygen from lungs to respiring tissues
First site of red blood cell production
liver of foetus, while in the uterus
Why do red blood cells not live long
- membranes become more and more fragile
- eventually rupture in some ‘tight spot’ usually the spleen
Plan an experiment for a haemoglobin dissociation curve
page 168
Adaptations in people living at high altitudes to the low-oxygen environment
- more red blood cells
- broad chest (providing larger lung capacities)
- larger heart, especially the right side, that pumps to the lungs
- more haemoglobin in blood (increasing the efficiency of oxygen transport from lungs to tissues, compensating for low partial pressures)
- increase in rate and depth of breathing
- increase in heart rate
What pushes valves open and shut
pressure differences in the blood
Why do the right ventricles need to produce less force
- only have to pump blood to the lungs which are very close to the heart
- if too high a pressure was developed, tissue fluid would accumulate in the lungs, hampering gas exchange
Function of the papillary muscles
papillary muscles attached to the valve by tendons prevent the atrioventricular valve from being forced inside-out
Diameter of capillaries
7μm
