Year 2 Bio Random Flashcards
Learn sum shiz
Describe tissue fluid
A watery liquid
Contains dissolved oxygen n nutrients
Supplies the necessary solutes to tissues
Receives waste materials such as CO2
A means by which materials are exchanged between blood and cells
Bathes all the cells of the body
Provides a mostly constant environment for the cells it surrounds
Describe formation of tissue fluid
Blood is pumped along arteries into narrower arterioles and then narrower capillaries creating hydrostatic pressure at the end of the capillaries
HP forces tissue fluid out of the blood plasma
HP is opposed by two other forces
HP of the tissue fluid outside the capillaries and a lower water potential of the blood due to plasma proteins, pulling water back into the blood within the capillaries
The combined effect of these forces is to create an overall pressure that pushes tissue fluid out of the capillaries.
Pressure here is only enough to force small molecules out of the capillaries, leaving all cells and proteins in the blood.
This type of filtration under pressure is known as ultrafiltration
Describe the return of tissue fluid to the circulatory system
Most returns to the blood plasma directly via the capillaries since the hydrostatic pressure within capillaries has been reduced due to the loss of tissue fluid
By the time the blood has reached the venuous end it’s HP is less than that of tissue fluid outside it.
Osmotic forces resulting from the proteins in the blood plasma pull water back into the capillaries
The remainder of tissue fluid is carried back via the lymphatic system
Outline the countercurrent flow system in fish
Water is taken in through the mouth n forced over the gills n out through an opening each side of the body
Flow of water over the hill lamellae n flow of blood within them are in opposite directions
This is so that there is always a higher concentration of O2 in the water than the blood so diffuses into the blood along the whole length of lamellae
Outline artery structure and function
Thick muscle layer = can constrict n dilate to control volume of blood passing through
Thick elastic layer = stretching and recoil helps maintain high blood pressure n smooth pressure surges creates by the beating of heart
Overall thickness = helps prevent vessel bursting under pressure
No valves = blood is under constant high pressure so does not tend to flow backwards
Describe gas exchange in single celled organisms
Have a large surface area to volume ratio
Thus oxygen can be absorbed by diffusion across their body surface
Body surface covered by only a cell surface membrane
CO2 does the same
Outline gas exchange in insects
Insects must balance the opposing needs of exchanging respiratory gases with reducing water loss
To reduce water loss they have water proof coverings and a small surface area to volume ratio to minimise the area over with water is lost
Means insect cannot use body surface to exchange/diffuse respiratory gases
So have developed an internal network of tubes called trachae (supported by strengthened rings to stop collapse) these divide into smaller tubes called tracheoles which extend throughout body tissue of the insect so oxygen can be brought directly to respiring tissues
Describe the workings of an insects gas exchange system
Respiratory gases move in and out of the tracheal system via a diffusion gradient (oxygen used up in respiration so concentration towards end of the tracheoles falls) and ventilation
Gases enter and leave trachae through tiny pores called spiracles on the body’s surface. The spiracles may be opened n closed by a valve. When they are open water can evaporate from the insect
Tracheal system relies mostly on diffusion to exchange gases between the environment and cells. For diffusion to be effective pathway must be short.
Tissues found in roots
Epidermis Cortex Endodermis Pericycle Vascular tissue/bundle
Epidermis Cortex Endodermis Pericycle Vascular tissue/bundle description
Epidermis - a single layer of cells often with long extensions called root hairs
Cortex - a thick layer of packing cells containing starch
Endodermis - a single layer of cells that surround the vascular tissue containing waterproof layer called the casparian strip
Pericycle - layer of undifferentiated meristematic cells
Vascular tissue/bundle - contains xylem and phloem cells
Epidermis Cortex Endodermis Pericycle Vascular tissue/bundle function
Epidermis - increase the surface area
Cortex - store for energy store
Endodermis - casparian strip allows the plant to control the movement of ions into the xylem
Pericycle - allows for plant growth (cell elongation)
Vascular tissue/bundle - xylem and phloem functions
What is the symplast pathway for water movement through the root?
A pathway where water moves through cytoplasm
What is the apoplastic pathway for water movement through the root?
A pathway where water moves through cell walls
Gills description in gas exchange in bony fish
Gills are located behind the heads of fish and are made up of gill filaments which are stacked up in a pile.
At right angles to the filaments are gill lamellae which increase the surface area of the gills
Describe mass flow as the mechanism for water movement through the stem
Since xylem vessels are dead open tubes no osmosis can occur within them thus water moves by mass flow
The driving force for the movement is transpiration in the leaves
Transpiration causes low pressure in the leaves so water is drawn up the stem replacing the lost water
The column of water in the xylem vessels is therefore under pressure
Fortunately water has a high tensile strength due to the tendency of water molecules to stick together via cohesive forces (hydrogen bonds) = cohesion tension mechanism
Root pressure also pushes up water from beneath. It arises because mineral ions are actively taken up into the xylem in the root
If transpiration is slow they aren’t transported up the stems the ions build up in the root xylem
This lowers the water potential in the root tissue and water is drawn up into the root by osmosis , pushing the column of water upwards
