Tissue Fluid

What are the 2 ends of the capillary called

arteriole end
venule end

What are some of the substances that exchange across this surface

oxygen
carbon dioxide
urea
water
glucose
ions
hormones

what is tissue fluid made of

plasma leaked out of the capillary

what is hydrostatic pressure

pressure exerted by any fluid in small places (eg capillaries)

what is oncotic pressure

pressure induced by protein in plasma that causes a fluid to move back into the capillary

How is tissue fluid created and returned to the circulatory system

At arteriole end, there is high hydrostatic pressure
This forces water to move to tissue fluid
Blood cells and plasma proteins stay in the blood
Useful products move to cells (eg O2)
(then goes to cells for exchange)

At venule end, oncotic pressure is high
Water is forced back into capillary
Water moves into capillary via osmosis also
Waste products move from tissue fluid to capillary (eg CO2)

What remains in the capillary when others are forced out by hydrostatic pressure

erythrocytes
leucocytes
plasma proteins

Kwashiokor is a disease caused by a lack of protein in the blood. This leads of a swollen abdomen due to a build up of tissue fluid.
Explain why a lack of protein in the blood causes a build up of tissue fluid.

Oncotic pressure is low with no proteins to induce it. Less water is removed from tissue fluid via osmosis into the capillary.

How does tissue fluid differ from blood and lymph?

Tissue fluid is formed from blood, but does not contain erythrocytes, platelets, and various other solutes usually present in blood.

After tissue fluid has exchanged with cells, it becomes lymph. Thus containing less O2 and nutrients and more waste products.

State the effect on the water potential of the blood if the concentration of glucose increases. \[1\]

Water potential decreases

Explain why the oncotic pressure of the blood depends only on the concentration of large plasma proteins. \[2\]

Large plasma proteins cannot pass through capillary wall / leave the blood

so there is an imbalance of large plasma proteins between blood and tissue fluid resulting in oncotic pressure.

The table below contains statements about the composition of lymph and tissue fluid.

Which are true and which are false? \[2\]

* Lymph is similar in composition to tissue fluid but has more oxygen.
* Tissue fluid does not contain lymphocytes because they are too large to pass through the capillary wall.
* Lymph contains more protein than tissue fluid because of antibody production by plasma cells.

False

False

True

Dissolved ions diffuse between blood plasma and tissue fluid.

Pressure differences at the arterial and venous ends of capillaries are responsible for the formation of tissue fluid.

The following measurements were made in one capillary:

• Net hydrostatic pressure at the arterial end was 4.6 KPa

• Net oncotic pressure was -3.0 KPa

• Net hydrostatic pressure at the venous end was 2.3 KPa.

Use this information to explain the movement of fluid in and out of a capillary. \[2\]

At arterial end, hydrostatic pressure is greater than oncotic pressure.

So fluid moves out from capillary.

But at venous end, the hydrostatic pressure is lower than the oncotic pressure.

So tissue fluid moves into capillary.