Bones are living organs systems structures( organs, systems, structures ), containing nerves neurons neutrophils( nerves, neurons, neutrophils ) and blood vessels collagen elastic fibres( blood vessels, collagen, elastic fibres ).
The main bones in the body have marrows memory cells meristem( marrows, memory cells, meristem ) in their centres.
Here, adult stem cells divide join move( divide, join, move ) and differentiate change go( differentiate, change, go ) to replace worn out blood cells – erythrocytes phagocytes neutrophils( erythrocytes, phagocytes, neutrophils ) (red blood cells) and neutrophils erythrocytes phagocytes( neutrophils, erythrocytes, phagocytes ) (white blood cells to fight infection).

Sperm Egg( Sperm, Egg ) cells have a flagellum so they can swim jump( swim, jump ) to the egg.
Have lots of mitochondria lysosomes( mitochondria, lysosomes ) to provide energy enzymes( energy, enzymes ) to swim.
Acrosome Phagosome( Acrosome, Phagosome ) in head contains digestive biological( digestive, biological ) enzymes to enable sperm to penetrate the surface of the egg.

Root hair Epithelium Meristem( Root hair, Epithelium, Meristem ) cells:
absorb water + mineral ions carbon dioxide waste( mineral ions, carbon dioxide, waste ) from soil.
have a large small( large, small ) surface area for absorption.
Have thin, permeable long impermeable( permeable, long, impermeable ) wall for entry of water and ions.
Have extra mitochondria lysosomes ribosomes( mitochondria, lysosomes, ribosomes ) (energy for active transport) in their cytoplasm plasma membrane vacuole( cytoplasm, plasma membrane, vacuole ).