Blood, Tissue Fluid and Lymph Fluid Flashcards
What 4 components is blood made out of?
RBCs, WBCs, platelets, plasma
What dissolved substances does plasma contain?
• oxygen
• carbon dioxide
• salts
• glucose
• fatty acids
• amino acids
• hormones
• plasma proteins
What is tissue fluid? And what is it made up out of?
Tissue fluid is the fluid that bathes all the cells. It has a similar composition to plasma however it does not contain any plasma proteins.
Role = transport oxygen and nutrients (eg amino acids, glucose) from the blood to the cells and carbon dioxide and urea from the cells back to the blood
What is the pressure inside a capillary called?
Hydrostatic pressure
What is osmotic pressure?
Describes the effect of solutes on a water potential gradient, pulling water in a specific direction by osmosis
At the arterial end of the capillary, is there a higher or lower hydrostatic pressure than the venous end?
• At the arteriole end there is a higher hydrostatic pressure which forces water and substances dissolved in water out of capillary
• At venous end there is a lower water potential in the blood plasma of the capillary, water moves back in by osmosis, followed by solutes such as carbon dioxide by diffusion
Describe the formation of tissue fluid
Occurs at arterial end:
1. Blood is under higher hydrostatic pressure than fluid in the tissues due to the contraction of the left ventricle muscle of the heart
2. Water in the blood is forced out of tiny gaps in the capillary wall
3. This fluid contains dissolved substances such as oxygen and glucose. However, the cells and plasma proteins are retained in the capillary as they are too big to fit through the gaps in the endothelium of the capillary
4. The fluid is now known as tissue fluid and as it surround the cells and allows the movement of substances across the plasma membranes
5. This type of filtration under pressure is called ultrafiltration
Describe the return of fluid to the capillary
Occurs at the venous end of the capillary:
1. The blood has low hydrostatic pressure as solute and water has left the capillary
2. The retention of the plasma proteins means the **blood plasma has a lower water potential compared to the tissue fluid
3. water moves back into the capillary by osmosis down a water potential gradient. Other solutes and waste products eg carbon dioxide follow by diffusion
4. Excess tissue fluid moves into the lymphatic capillaries where it drains back into the circulatory system via the subclavian vein
What is the relationship between hydrostatic pressure and osmotic pressure in the arteriole end?
Hydrostatic pressure pushing out of the capillaries is higher then the osmotic pressure of the surrounding tissue fluid pushing in the opposite direction
What is the relationship between hydrostatic pressure and osmotic pressure in the venuole end?
Hydrostatic pressure pushing out of the capillaries is now lower than the osmotic pressure of the surrounding tissue fluid pushing in the opposite direction
How could a diet low in protein lead to an accumulation of tissue fluid?
• diet low in protein leads to a blood plasma protein content that is lower than normal levels
• proteins are soluble in blood plasma and therefore a reduction in protein content would increase the water potential of the blood plasma
• this results in a reduction in the water potential gradient between the blood plasma and the tissue fluid
• as a consequence more tissue fluid will be formed at the arteriole end of the capillary and less water will move by osmosis back into the capillary at the venue and of the capillary, leading to an accumulation of tissue fluid ( known as oedema)
What are lymph vessels?
Form a secondary drainage system returning some tissue fluid to the blood stream via the subclavian vein. If lymph vessels become blocked swelling can occur in the affected limbs due to accumulation of tissue fluid
What is lymph fluid?
Has a similar composition to tissue fluid but with more lipids and carbon dioxide but less oxygen and nutrients
What are lymph nodes?
Situated in the armpit, groin, neck and gut. They produce lymphocytes which intercept bacteria and viruses and help prevent the spread of microbial infection in the body
What are 3 things the lymphatic system is involved in?
1) draining excess tissue fluid and returning it to the blood
2) immune system - produces lymphocytes
3) absorption of lipids from digestive system
Explain why there is a net movement of fluid into the tissues at point X on the graph
Hydrostatic pressure is higher than osmotic pressure in the blood capillary so water is forced out of the gaps in the blood capillary leading to formation of tissue fluid
