1. Plasma Pale yellow liquid of blood Plasma leaks out of capillaries
Water with substances dissolved
Glucose (nutrient), urea (waste)
Plasma Proteins
Plasma leaks out of capillaries
Forms tissue fluid
Plasma proteins too big to leak

2. Tissue Fluid Similar to plasma, but
Few plasma proteins & RBCs
WBCs can squeeze through capillaries into tissue fluid

3. Formation of Tissue Fluid
Depends on pressure in blood vessel (from artery)
Balanced by tendency for water to move:
from high water potential in tissue fluid (few plasma proteins)
to low water potential in blood (lots of plasma proteins; concentrated solution)
Fluid flows
out of capillary at arterial end of capillary bed
Into capillary at venous end of capillary bed

4. Homeostasis Tissue fluid is the external environment of most cells
Exchange of material happens through tissue fluid
Constancy of tissue fluid required
Glucose, water, pH, waste, temperature
Oedema is build up of tissue fluid

5. Lymph 90% tissue fluid seeps back into capillaries
10% collected in lymph vessels
Dead-end vessels
Valves allow flow into lymph vessels
Valves allow large protein molecules through
(cannot get back into capillaries)
Lymph similar composition to tissue fluid

7. Unusual Tissue Fluid Liver: Small Intestine:
High protein concentrations in tissue fluid & lymph
Small Intestine:
High lipid concentration in lymph after a meal
‘Lacteal’ is a lymph vessel in each villus
Absorb lipids

8. Fate of Lymph Form larger vessels
Empty into subclavian veins (beneath collar bone)
Movement by muscles and valves
Some smooth muscle in walls
Slow: 100cm3h-1 (blood 80cm3 s-1)

9. Lymph Nodes Protection against disease in nodes:
Phagocytes remove pathogens etc
Lymphocytes secrete antibodies

10. Blood ~5dm3 25 million million RBCs 0.5 million million WBCs
6 million million platelets

11. Red Blood Cells Erythrocytes (‘red cells’)
Red due to haemoglobin (globular protein)
Transports oxygen
First formed in liver as a foetus
Before birth, bone marrow takes over
First in long bones eg femur, humerus
Later more in skull, ribs, pelvis
Short life, cell membrane becomes fragile
often rupture in spleen

12. RBCs are Unusual Small; 7µm (cf liver cell 40µm average)
All haemoglobin is close to surface
Capillaries can also be small
Efficient diffusion
Biconcave disc shape
Increases surface area:volume
Faster diffusion
No nucleus, mitochondria, ER
More room for haemoglobin
More capacity to transport oxygen

13. White Blood Cells Leucocytes (‘white cells’) Fight disease
Made in bone marrow
Have a nucleus
Larger than RBCs (except lymphoyctes)
Usually spherical
Fight disease
Phagocytes (phagocytosis)
Lobed nuclei, granular cytoplasm
Lymphocytes (antibodies)
Large round nucleus, little cytoplasm, smaller