B3.2 Transport Flashcards
(27 cards)
What is the function of fenestrations in capillaries?
Fenestrations are gaps in the thin endothelial cells of some capillaries. They allow blood plasma to leak out and form tissue fluid, enabling exchange of substances like oxygen, glucose, and carbon dioxide.
What is the significance of capillary beds?
Capillary beds are networks of capillaries formed between cells. They increase the surface area for diffusion of substances to and from cells, reducing the diffusion distance.
Describe the direction of the flow of blood in arteries and veins.
Arteries carry blood away from the heart.
Veins carry blood into the heart.
Define endothelium.
The endothelium is the innermost layer of artery and vein walls, consisting of squamous epithelial cells. It is one cell thick and reduces friction for smooth blood flow.
How does vasoconstriction affect blood pressure?
Vasoconstriction (narrowing of the lumen) increases blood pressure by reducing the diameter of arteries.
What is the role of elastic tissue in arteries?
Elastic tissue helps maintain blood pressure by stretching and recoiling during heartbeats, evening out pressure fluctuations.
What is the purpose of valves in veins?
Vein valves prevent backflow of blood under low pressure, aiding blood return to the heart.
How do skeletal muscles assist blood movement in veins?
Skeletal muscle contractions push blood through veins, and valves prevent backward flow.
What is the main difference in wall thickness between arteries and veins?
The arterial walls are much thicker than those of veins.
Define the term ‘lumen’ in the context of blood vessels.
Lumen is the internal space or cavity within a blood vessel through which blood flows.
What is the purpose of the larger lumen in veins?
The larger lumen in veins helps to ensure that blood returns to the heart at an adequate speed by reducing friction between the blood and the endothelial layer.
State the relationship between lumen size and blood flow rate in veins.
In veins, the rate of blood flow is slower, but the larger lumen means the volume of blood delivered per unit of time is equal to that of arteries.
What causes a pulse in arteries?
A pulse in arteries is caused by the expansion of arteries to accommodate the large volume of blood forced through them by the contraction of the ventricles.
Where is the carotid artery located?
Carotid artery is an artery that runs down the side of the neck, where a pulse can be felt just below the jaw.
Define ‘occlusion of the arteries’.
Occlusion of the arteries is the narrowing of the arteries due to a blockage.
What is atherosclerosis?
Atherosclerosis is a process where fatty deposits build up under the endothelium of arteries, narrowing the lumen and reducing blood flow.
What is a thrombus?
A thrombus is a blood clot formed within a blood vessel.
Define embolus.
Embolus is a blood clot that circulates in the bloodstream.
What is a myocardial infarction?
A myocardial infarction, or heart attack, occurs when parts of the heart muscle die due to blocked coronary arteries.
What is transpirational pull?
Transpirational pull is the pulling force created by the tension in the xylem when water moves into leaf cells, transmitted through the plant via cohesion between water molecules.
Define ‘capillary action’ in the context of plant water movement.
Capillary action is the movement of water that occurs due to adhesion to the walls of a narrow tube, such as the cell walls in plant xylem.
What is the cohesion-tension theory of transpiration?
The cohesion-tension theory of transpiration explains how water moves upwards through plants against gravity, due to the tension created by water loss in leaves and the cohesion between water molecules.
State three ways in which transpiration is important to plants.
Transpiration is important to plants in three ways:
1. it provides cooling through evaporation
2. helps in the uptake of mineral ions
3. provides support to leaves and non-woody stems through turgor pressure
What are the two main functions of xylem vessels in plants?
The two main functions of xylem vessels are the transport of water and the transport of mineral ions from the roots.
