B3.2 Transport Flashcards
(15 cards)
What are the structural adaptations of capillaries that make them effective for gas and nutrient exchange?
1) Large surface area – due to extensive branching into capillary beds.
2) One-cell-thick walls – short diffusion distance as walls are made of endothelium.
3) Fenestrations (pores) – in some capillaries allow tissue fluid (plasma) to leak through, bathing and nourishing cells.
4) Narrow lumen – slows blood flow and forces red blood cells to pass single file, maximizing contact with the walls and slowing flow for more efficient diffusion.
→ These features help oxygen and glucose diffuse into tissues and CO₂ out into blood.
What are the functions of capillaries?
1) Capillaries allow diffusion of oxygen and carbon dioxide between the blood and tissues.
2) Glucose and other nutrients pass from blood into cells.
3) Plasma leaks through fenestrations, forming tissue fluid, which bathes and nourishes nearby cells and removes waste.
→ This exchange is essential for cellular respiration and homeostasis.
What structural features allow arteries to transport blood away from the heart under high pressure?
- Thick muscular and elastic walls (especially in the middle layer) allow arteries to withstand high pressure.
- Narrow lumen helps maintain high pressure.
- Elastic fibers stretch and recoil to smooth out pressure fluctuations between heartbeats.
- Smooth muscle regulates lumen diameter (vasoconstriction/dilation).
- Collagen in outer wall provides strength and prevents rupture. → These features allow arteries to safely transport blood under pressure during systole and diastole.
What features of veins help return blood to the heart under low pressure?
- Thin walls (as pressure is low), allowing external muscle compression to assist blood flow.
- Wide lumen reduces resistance and accommodates larger blood volume.
- Valves prevent backflow of blood.
- Skeletal muscle contractions help push blood forward.
- Surrounding muscles, especially in the legs, assist blood movement.
- Veins can collapse slightly under pressure – their flexible structure adapts to volume and pressure changes.
How is pulse rate measured manually and digitally, and what considerations should be made?
Manual method:
• Use carotid artery (side of neck, below jaw) or radial artery (thumb side of wrist).
• Count pulses for 60 seconds for accuracy.
• Avoid using the thumb to feel the pulse, since it has its own pulse.
Digital method:
• Use smartwatches, fitness bands, or data loggers that detect pulse using light sensors or pressure to measure blood flow through arteries.
→ This allows continuous, convenient monitoring.
What is occlusion?
Occlusion = blockage or narrowing of arteries, especially coronary arteries.
What are the consequences and treatments of coronary artery occlusion?
Consequences: Reduced O₂ → heart cell death → myocardial infarction (heart attack).
Treatment: Bypass surgery – blood is rerouted using a vein from the leg.
What does correlation vs. causation mean in epidemiological studies?
Studies (e.g. on fat/smoking and heart disease) often show correlation, but this does not prove causation.
What must valid studies include
- Use large, representative samples
- Be repeatable with consistent results
- Control for confounding variables (e.g. age, stress, diet)
- Use proper statistical analysis (e.g. correlation coefficient) → Avoid assuming direct cause from simple associations.
How is water transported from roots to leaves in a plant via transpiration?
- Water evaporates from the leaf (mostly stomata) = transpiration.
- Water is drawn from the xylem due to tension (negative pressure).
- Cohesion between water molecules and adhesion to xylem walls help maintain a continuous flow.
- This creates an upward movement of water = transpiration stream.
- Water reaches leaf cells to support photosynthesis and cooling by evaporation. → This process helps maintain leaf temperature and allows nutrient delivery.
What structural features make xylem vessels effective for water transport?
- Dead, hollow cells with no cytoplasm or end walls allow unimpeded flow.
- Lignified walls strengthen vessels and prevent collapse under tension.
- Pits allow sideways water movement between adjacent vessels.
- Narrow tubes enhance capillary action and cohesion. → These features maintain water flow under negative pressure in the transpiration stream.
What tissues are found in a transverse section of a dicot stem, and what are their functions?
- Epidermis – outer protective layer; may have a waxy cuticle to reduce water loss.
- Cortex – made of parenchyma cells; provides support and stores water/sugars.
- Vascular bundles – in a ring: • Xylem (inner side) – transports water/minerals • Phloem (outer side) – transports sugars • Cambium (between xylem and phloem) – produces new xylem/phloem in growing stems
- Pith (center) – parenchyma cells; stores starch and helps support the stem → All tissues are organized for mechanical strength and efficient transport.
What tissues are found in a transverse section of a dicot root and what are their roles?
- Epidermis – outer layer with root hairs that absorb water and minerals.
- Cortex – parenchyma cells for storage and lateral movement of substances.
- Endodermis – regulates what enters the vascular tissue; has a waterproof Casparian strip.
- Pericycle – produces lateral roots.
- Vascular tissue (stele) – • Xylem forms an X-shaped structure in the center for strong water transport • Phloem is located between the arms of the xylem → The central position of xylem provides mechanical support and efficient vertical water movement.
What is atherosclerosis
Atherosclerosis: fatty deposits called atheromas build up under the artery lining (endothelium), often after damage (e.g. from high blood pressure or smoking).
Describe process of occlusion and atherosclerosis
Atheromas can harden into plaques, which reduce lumen size and elasticity, restricting blood flow. → This leads to decreased oxygen supply to heart cells.
