Movement of Lymph
1. Moves by contraction of skeletal muscles
2. Semi-lunar valves stop back flow of lymph
3. Gravity causes lymph to flow downwards
Functions of Lymphatic system
1. Returns excess tissue fluid to blood
2. Transports lipids (Fatty acids + Glycerol) + Fat-soluble vitamins that are absorbed from small intestine
3. Defence against disease. Part of human defence system. Lymph nodes filter bacteria. Lymphocytes mature here
The Lymphatic System Structure
1. Lymphatic system consists of lymphatic vessels flowing alongside veins
2. Vessels return lymph through thoracic + lymphatic ducts to blood system at subclavian veins near superior vena cava under the clavicles
3. Swellings along lymphatic vessels called lymph nodes are found at tonsils, spleen, neck, groin and armpits
4. Trap micro-organisms during infection. Lymphocytes develop here
Tissue fluid
1. Blood plasma leaks out at end of capillaries due to thin walls + high pressure
2. Tissue fluid surrounds every body cell. Substances are exchanged between tissue fluid + cells
3. Red and white blood cells, platelets + large proteins are too big to leave capillary. They stay in blood
4. Tissue fluid returns to blood
5. Excess tissue fluid drains into lymphatic vessels forming lymph
Four types of fluids
1. Plasma
2. Serum
3. Tissue fluid
4. Lymph
Plasma
Liquid part of blood. Contains blood cells + proteins
Serum
Plasma with blood clotting proteins removed
Tissue fluid
Surrounding cells. Similar to plasma, but without red blood cells, platelets + large proteins
Lymph
Inside lymphatic vessels. Similar to tissue fluid, but with more lipids
Diffusion
Movement of water
From an area of it's high concentration
To an area of it's low concentration
Passive
Does not require energy
Diffusion in humans
Oxygen diffuse into the blood in the lungs
Carbon dioxide diffuses out of the blood in the lungs
Diffusion in plants
Carbon dioxide diffuses into leaf through stomata
Oxygen diffuses out of leaf through stomata
Semi-permeable
Only some substances can pass through
Fully permeable
All substances can pass through
Small + Large molecules
Small molecules can get though small pores in membrane
Large molecules too big + cannot get through small pores
Examples of small molecules
H2O, O2 and CO2
Membranes in cell that are semi-permeable
1. Cell membrane
2. Mitochondria membrane
3. Chloroplast membrane
4. Nucleus membrane
Osmosis
Movement of water
From an area of it's high water concentration
To an area of it's low water concentration
Across a semi-permeable membrane
Why is Osmosis a "special case" of diffusion?
It's the diffusion of water across a semi-permeable membrane
Importance of kidneys in Animals
If Blood plasma had a high water concentration compared to water concentration inside red blood cells
Cells water would move from blood plasma into cells by osmosis causing red blood cells to swell and burst
If an Animal cell is surrounded by a solution with a Low water concentration compared to cytoplasm in cell
What happens?
Result?
What happens?- Water moves out of cell by osmosis
Result- Cell shrivels up + may die
If an Animal cell is surrounded by a solution with a High water concentration compared to cytoplasm in cell
What happens?
Result?
What happens?- Water moves into cell by osmosis
Result- Cell swells up + may burst
If an Animal cell is surrounded by a solution with same water concentration compared to cytoplasm in cell
What happens?
Result?
What happens?- Water moves in and out of cell by osmosis
Result- No change occurs
Plasmolysis
Pulling away of cytoplasm from cell wall dye to loss of water from vacuole + cytoplasm by osmosis
What happens to plants when their cells lose water?
Plants wilt
Osmoregulation
Kidneys control water level in blood plasma by removing excess water from blood
If an Plant cell is surrounded by a solution with Low water concentration compared to cytoplasm in cell
What happens?
Result?
What happens?- Water moves out of vacuole + cytoplasm by osmosis
Result-
Cell membrane pulls away from cell wall
Cell wall stays intact, rest of cell shrivels up
Cell is plasmolysed
If an Plant cell is surrounded by a solution with High water concentration compared to cytoplasm in cell
What happens?
Result?
What happens?- Water moves into vacuole + cytoplasm by osmosis
Result-
Vacuole swells causing cell to swell and cell is turgid
Turgor
Outward pressure of vacuole + cytoplasm against plant cell wall
Effect on plants
1. Herbaceous (soft stem) rely on turgor pressure for mechanical support
2. Roots absorb water from soil
Osmosis and Food preservation
Sugary/Salty solutions = Low water concentraion
Micro-organisms lose water by osmosis and die as they cannot survive without water
Examples of Osmosis and Food Preservation
1. Fish and Bacon = Salt solution
2. Jam and Tinned Fruit = Sugar solution
Active Transport
Movement of a substance
From an area of it's low concentration
To an area of it's high concentration
Active process
Requires energy
Examples of when active transport occur
1. Kidney (nephron)- during reabsorption of glucose and useful substances
2. Root hair- Absorption of minerals from soil
Why Marine (Saltwater) Amoeba do not need a contractile vacuole?
Salt/Water concentration is the same as concentration of seawater that surrounds it
Water moves in and out of saltwater Amoeba at the same rate
Marine Amoeba do not swell and burst, they do not need a contractile vacuole
Importance of Contractile Vacuole to Freshwater Amoeba
Outside water has high water concentration compared to inside Amoeba.
So water moves into amoeba by osmosis causing it to swell and burst
Contractile bascule in freshwater amoeba collect excess water inside amoeba and release it
Known as Osmoregulation