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