Because bacteria mutates that's why we have a new flu vaccine every year , because strains of DNA in the bacteria change all the time.
Answer:
They are smaller than blood capillaries.
Explanation:
Lymphatic capillaries drains the extracellular fluid present between the cell spaces. The fluid is known as lymph as it enters the lymph capillaries. These capillaires drains into lymph vessels that drains to lymph nodes and lymph ultimately enters the venous circulation.
Lymphatic capillaries are slightly larger than blood vessels and these capillaries have close ends. The walls of lymph capillaries are made up of endothelial cells. The endothelial cells overlap in lymph vessels and when the pressure in ECF is greater these cells move and create a sort of gap for the movement of ECF inside the lymph capillary but when the pressure inside the capillary is greater these cells again overlap and does not allow the lymph to move outside of capillary. Thus lymph capillaries only allow the ECF to enter the capillary but does not allow the lymph to go out from capillary. Lymph capillaries have greater internal pressure than blood vessels.
Evolved from prokaryotic cells
This statement should be true, hope this helps!!!!!
