Final answer:
Expired blood tubes lose their seal and cause the blood and its components to deteriorate and leak out of the tube. This renders the blood sample unusable for analysis.
Step-by-step explanation:
When an expired blood tube loses its seal, the blood and its components begin to deteriorate. The cells in the blood, such as erythrocytes (red blood cells) and leukocytes (white blood cells), start to break down and leak out of the tube. This can affect the composition and quality of the blood sample, making it unusable for analysis.