Cells, Tissues, Organs and Organ systems

• Organelles, also known as subcellular structures, are the parts that make up a cell, including the nucleus, ribosomes, and mitochondria.
• Cells come in all sorts of shapes and sizes and contain different combinations and numbers of the organelles that we just mentioned.
• Cells can be specialized, for example, epithelial cells, muscle cells, and different types of glandular cells.
• Tissues are a group of similar cells that work together to carry out a particular function, for example, epithelial tissue, muscle tissue, and glandular tissue.
• An organ is a group of different tissues that work together to perform a particular function, for example, the stomach, pancreas, and liver.
• An organ system is a group of organs that work together to perform a particular function, for example, the digestive system, cardiovascular system, and reproductive system.
• The whole organism is the highest level with multiple organ systems working together to form the organism.