transport Flashcards
Describe capillaries
- 5-10 um
- Has basement membrane
- Highly branched
- Wall is one cell thick, made of flattened endothelial cells
- Small lumen
- Tissue fluid formed by blood plasma and surrounds cells
- Continuous capillaries present in muscle, skin, lungs
- Fenestrated capillaries in high metabolic demands tissue like kidneys, small intestine.
Explain reason for adaptations in capillaries
*Basement membrane provides structural support for endothelium, and regulates exchange of material
* Highly branched to increase surface area to volume ratio, slow down blood flow for more substance exchange, make it quicker.
* Wall is thin for short diffusion distance
*Small lumen to cause red blood cells to squeeze into single-file, making blood move slower and thus more diffusion happens.
* Tissue fluid surrounds cells, enabling exchange of substances
Describe arteries
- Blood away from heart
- Thick walls with elastin and smooth muscle
- Narrow lumen
- Three layers
Explain reasons for adaptations in arteries
- Elastin in walls to accommodate increases in volume as blood flows
– Volume increases as blood flows in
– Walls then recoil as heart relaxes, pushes blood
*Elastin reduces fluctuations in blood pressure - Smooth muscle regulates diameter by contracting or relaxing
- Narrow lumen increases pressure
Name the three walls of arteries and their build
Tunica intima: In contact with blood, has endothelium layer to reduce friction
Tunica media: Smooth muscle cells and elastic fibre. Usually the thickest.
Tunica adventitia: Collagen fibres and elastic fibres which protect and anchor it down.
What is systolic vs dyastolic pressure
Systolic pressure is the highest pressure point reached as blood is forced out of ventricles.
Dyastolic pressure is the lowest pressure point reached as heart relaxes
Muscles can ____ and ____.
Elastic tissue can ____ and ____.
Muscles can contract and relax.
Elastic tissue can stretch and recoil.
Describe veins
- Return blood to heart
- Thin walls, less smooth muscle and elastic fibre.
- Big lumen
- Flexible walls
Explain reasons for adaptations in veins
- Thin walls w/ less muscle and elastic fibre because there is no need for high pressure
- Big lumen to decrease pressure
- Valves for low pressure to prevent backflow
- Flexible muscles because surrounding muscles compress them, facilitating movement back to the heart.
Coronary heart disease causes
CHD is caused by plaque build-up, mostly cholesterol particles.
Coronary heart disease consequences
It narrows the diameter of the coronary artery, reducing blood flow to heart.
Parts of this plaque (antherosclerotic plaque) can rupture, exposing and damaging tissue underneath. Exposure of tissue results in formation of blood clot, further restricting blood flow.
Describe the transpiration stream in the xylem
- Unidirectional.
- Often going against force of gravity.
- Transpiration:
–Water evaporates through stomata.
– Negative pressure potential created.
^There is lower water potential outside the stomata compared with inside the leaf.
–Results in water being pulled out of xylem, which in turn pulls water up the xylem (capillary action) - Possible because of adhesion and cohesion.
Ways of measuring pulse rate
Feeling the radial artery (on wrist just below thumb) or the carotid artery (on neck, beside trachea). Place finger and count number of pulses that occur in 15 seconds, multiply by 4 for one minute.
Using a stethoscope placed on the sternum.
Heart rate monitor (measures electrical signals of the heart)
Why are cells in the xylem hollow
So the water does not have to go across membranes every time in the transpirations stream.
Xylem adaptations
Thin, continuous columns made of dead, hollow cells.
Walls stregnthened with lignin because it binds to cellulose and gives the plant strength; allows plants to withstand mechanical stress and tension; waterproofs the xylem walls. Deposited as rings or spirals.
Specialised cells which make xylem contain pits (wall thinner, no lignin) allows lateral movement of water into and out of xylem (if vessel is damaged water can still reach destination)
