3.1.2 Transport in Animals Flashcards
1
Q
Why are transport systems needed in multicellular animals?
A
- Increased size means diffusion distance increases
- Small SA:V ratio
- Level of metabolic activity
2
Q
What are the features of a transport system?
A
- Suitable transport medium (normally water based)
- Vessels to transport the medium
- A pump (or pressure) to transport the medium around the vessels
- Medium which flows in one direction
- Ability to control flow of medium to suit the changing needs to different parts of the organisms
3
Q
What is a single closed circulatory system?
A
- Only passes through the heart once for each complete circuit of the body
- Heart has 2 chambers
- Because it goes through 2 sets of narrow vessels, pressure is low which limits exchange processes
4
Q
What is a double closed circulatory stystem?
A
- Blood travels through the heart each circuit
- Ensures relatively high pressure and fast flow of blood
5
Q
What are the advantages of a double closed circulatory system?
A
- The blood only travels through one capillary network before returning to the heart
- This maintains a higher pressure and steeper concentration gradient
6
Q
What is a closed circulatory system?
A
- Blood is enclosed in blood vessels and doesn’t come directly into contact with cells
- Blood is pumped under pressure and things leave through the walls of the blood vessels
7
Q
What is an open circulatory system?
A
- The blood (haemolymph) flows freely from the heart into body cavities (haemocoel) and comes into contact with the cells
- This is where exchange takes place before returning to the heart through open ended vessels
8
Q
What are the components of the blood?
A
- Red blood cells
- White blood cells
- Platelets
- Plasma
9
Q
What is the role of the components of the walls of the blood vessels?
A
- Smooth muscle contracts to control the flow of blood
- Elastic layer allows vessel to stretch and recoil
- Endothelium is a thin inner lining which is smooth to reduce friction in all vessels
10
Q
What are the characteristics of the arteries?
A
- Carry blood away from the heart
- High pressure
- Narrow/small lumen to maintain pressure
- Thick muscular wall
- Elastic fibres in wall stretch and reoil with each ventricular contraction to maintain high blood pressure
- Endothelium is folded to allow stretching/artery to expand to maintain high blood pressure
11
Q
What are the characteristics of the arterioles?
A
- Small blood vessels that distribute the blood away from an artery to the capillaries
- An arteriole wall has rings of smooth muscle which contract and constrict the diameter of the arteriole
- Increases resistance to flow and reduces the rate of flow of blood which diverts the flow to parts of the body that are demanding more oxygen
12
Q
What are the characteristics of capillaries?
A
- Very narrow diameter to reduce blood flow to allow for time for exchange between blood and surrounding cells to take place more efficiently
- Thin walls only one cell thick to ensure maximum rate of transfer between blood and surrounding tissue fluid
- Close to cells for a short diffusion distance
- Large number to increase surface area
- Fenestrations (gaps between endothelial cells) mean walls are leaky to allow plasma and dissolved substances to leave the blood
13
Q
What are capillary beds?
A
- Networks of capillaries running through tissues
- Precapillary sphincters regulate the flow of blood to the tissues
14
Q
What are the characteristics of venules?
A
- Capillaries join to form valves
- These collect blood from the capillary bed and lead into veins
- The venule wall consists of thin layer of muscle, elastic and collagen
15
Q
What are the characteristics of veins?
A
- Outer layer of connective tissue with fibres of collagen (same as artery)
- Carry blood towards heart
- Thin walls with few elastic fibres and smooth muscle
- Blood flow slowly under low pressure and there is no pulse so the walls don’t need to stretch and recoil)
- Wide when in order to ease blood flow
- Valves prevent the backflow of blood
16
Q
How do valves work in veins?
A
- Blood in the veins is pushed forward by the pressure produced by the contraction of the nearby skeletal muscles which the vein runs through
- When the muscles relax and stop pressing, the pressure drops and valves prevent the backflow of blood
17
Q
What is hydrostatic pressure?
A
Pressure created by a fluid pushing against the container that it’s within
18
Q
What is oncotic pressure?
A
Pressure created by the osmotic effects of the solutes in a solution (opposing force)
19
Q
How is tissue fluid formed?
A
- At the arterial end of capillary, blood is at a relatively high hydrostatic pressure
- Pressure pushes the blood fluid out of the capillaries through the capillary wall
- Fluid leaving the blood contains plasma with dissolved nutrients and oxygen
- All red blood cells, platelets, most white blood cells and plasma proteins remain in the blood as they are too large
- Tissue fluid surrounds body cells so exchange of gases and membranes of gases/nutrients/ can occur across plasma membrane
20
Q
How to calculate the net hydrostatic and oncotic pressure?
A
- For hydrostatic, subtract inner pressure from outer pressure
- For oncotic pressure, subtract inner from outer - - There is no change in the net oncotic pressure and the number of proteins haven’t changed
