3.1.2d Blood, Tissue Fluid, Lymph Flashcards
What is tissue fluid
- Fluid found between cells of tissues
- Composed of plasma leaked from blood through gaps in capillary wall (eg. oxygen, water & nutrients)
- Same constituents as blood EXCEPT:
- no plasma proteins
- no red blood cells (some WBCs can squeeze through)
(because theyre too large to be pushed out through capillary walls)
- Responsible for exchange (cells take in oxygen & nutrients from the tissue fluid, & release metabolic waste into it)
What is pressure filtration
In a capillary bed (the network of capillaries in an area of tissue), substances move out of the capillaries, into the tissue fluid, by pressure filtration
Composition of blood
- Blood consists of plasma (a yellow liquid) - which carries a wide variety of other components including dissolved glucose & amino acids, mineral ions, hormones, & the large plasma proteins including albumin, fibrinogen, globulins.
- Plasma also transport RBCs & many types of WBCs
- Also carries platelets - fragments of large cells called megakaryocytes found in red bone marrow, involves in clotting mechanism of blood
- Much of plasma volume is actually water
- Only the plasma & RBCs are involved in the transport functions of the blood
Simple composition of blood overview
Made up of cells:
- Red blood cells
- White blood cells
- Platelets
Made up of blood plasma (contains):
- Glucose
- Amino acids
- Mineral ions
- Oxygen
- Plasma proteins (sa albumin)
What exchange occurs with tissue fluid
Tissue fluid leaves the blood at the parts of the capillary which are near the artery
Tissue fluid transfers molecules sa oxygen & glucose to the tissue cells
Waste molecules from the tissue cells sa CO2 pass into the tissue fluid
The tissue fluid then returns back to the bloodstream at the parts of the capillary which are near the vein
What happens at the arterial end of the capillary bed
- Hydrostatic pressure (created by the heart contracting) is greater than the oncotic pressure (the attraction of water, by osmosis, that results from plasma proteins)
- Therefore, water leaves the capillaries through small pores in the capillary wall
- Tissue fluid circulates around the cells & exchange takes place
What happens at the venous end of the capillary bed
- The oncotic pressure is now greater than the hydrostatic pressure, which has now dropped
- Water moves back into the capillaries by osmosis, carrying waste products (90% of the tissue fluid drains back into the blood)
Where is tissue fluid drained
(90% of tissue fluid drains back into the blood at the venous end of the capillary)
However, the remaining 10% of tissue fluid drains into a series of blind-ended vessels called lymph capillaries, where it becomes known as ‘lymph’
Lymph capillaries connect into larger lymph vessels, forming the **lymphatic system*
Lymph fluid moves along when lymph vessels are squeezed by nearby skeletal muscles
Valves in the lymph vessels help to keep the lymph fluid moving forward
Eventually, the lymph fluid returns to the bloodstream via blood vessels under the collar bone
see link on showbie for diagrams (freesciencelessons), pg81
Links between blood, tissue fluid & lymph
Tissue fluid is formed by blood
Lymph is formed from tissue fluid
Composition of blood
Contains:
- RED BLOOD CELLS
- WHITE BLOOD CELLS
- PLATELETS
- PLASMA PROTEINS
- WATER
- DISSOLVED SOLUTES (solutes sa salt, can move freely between all 3, blood, tissue fluid & lymph)
Composition of tissue fluid
Contains:
- WATER
- DISSOLVED SOLUTES (solutes sa salt, can move freely between all 3, blood, tissue fluid & lymph)
- VERY FEW WHITE BLOOD CELLS (only enter when theres an infection)
- VERY FEW PLASMA PROTEINS (most plasma proteins are too big to get through capillary walls)
Does not contain:
- RED BLOOD CELLS (RBCs are too big to get through capillary walls into tissue fluid)
- PLATELETS (only present in tissue fluid if the capillaries are damaged)
Composition of lymph
Contains:
- WHITE BLOOD CELLS (Most WBCs are in the lymph system. They only enter tissue fluid when theres an infection)
- WATER
- DISSOLVED SOLUTES (solutes sa salt, can move freely between all 3, blood, tissue fluid & lymph)
- PLASMA PROTEINS BUT THESE ARE ONLY ANTIBODIES (most plasma proteins are too big to get through capillary walls)
Does not contain:
- RED BLOOD CELLS (RBCs are too big to get through capillary walls into tissue fluid, therefore cannot be in lymph)
- PLATELETS (only present in lymph is present in tissue fluid due to damage to capillaries)
Water potential comparison of blood, tissue fluid & lymph
Since all 3 contain water,
Tissue fluid & lymph have a higher water potential than blood
EXAM Q practice: 3 differences between tissue fluid & blood
- Blood contains plasma proteins, whilst tissue fluid contains very few plasma proteins
- Blood contains RBCs, whilst tissue fluid does not
- Blood contains platelets, whilst tissue fluid does not
EXAM Q practice: 2 differences between tissue fluid & lymph
- Lymph contains WBCs, whilst tissue fluid contains very few WBCs
- Lymph contains only antibodies (plasma proteins), whilst tissue fluid contains very few plasma proteins
EXAM Q practice: 3 differences between blood & lymph
- Blood contains RBCs, whilst lymph does not
- Blood contains platelets, whilst lymph does not
- Blood contains plasma proteins, whilst lymph contains only antibodies (plasma proteins)
EXAM Q practice: Similarities between tissue fluid & blood
- Both contain water
- Both contain dissolved solutes
EXAM Q practice: Similarities between tissue fluid & lymph
- Both do not contain RBCs
- Both do not contain platelets
- Both contain water
- Both contain dissolved solutes
EXAM Q practice: Similarities between blood & lymph
- Both contain WBCs
- Both contain water
- Both contain dissolved solutes
