Cell and Tissue

Cell

A cell consists of a cytoplasm enclosed by a cell membrane and is typically microscopic. It is the smallest unit of living matter and forms the basis of all living organisms. Most cells contain nuclei and other organelles that perform various functions. While some cells, like bacteria or yeast, are entire organisms, others serve as specialised components in multicellular organisms such as plants and animals.

In biology, the fundamental unit enclosed by a membrane containing the essential molecules for life is known as a cell. It can operate independently as an organism, like bacteria or yeast. As cells mature, they specialise in various functions, collaborating with other specialized cells to form larger multicellular organisms, such as animals and humans. Despite being larger than atoms, cells are still extremely small. The smallest known cells, mycoplasmas, can be as tiny as 0.2 μm in diameter, with a total mass equal to that of 8 billion hydrogen atoms. Human cells, in contrast, are typically about 20 μm across, and it would take approximately 10,000 human cells to cover the head of a pin. An individual human is composed of over 30 trillion cells.

Type of cells

• Blood Cells: Also referred to as blood corpuscles, these cells are manufactured in the bone marrow and circulate throughout the body. They vary in shape and size and fulfil diverse functions, including Red Blood Cells (RBCs), White Blood Cells (WBCs), and platelets.
• Neurons: These specialized nerve cells reside in the brain and spinal cord, facilitating the transmission of messages. They consist of a cell body, dendrites (which receive signals), and an axon (which transmits signals).
• Muscle Cells: Also termed myocytes, these cells are responsible for contraction and relaxation in animal muscles. In vertebrates like humans, there are three primary types: skeletal muscle cells (attached to bones for voluntary movement), smooth muscle cells (found in organs for involuntary movement), and cardiac muscle cells (forming the heart muscles).
• Animal Cells: These cells are characteristic of animals and exhibit distinct shapes, sizes, and the presence of specific organelles within their structures.
• Stem Cells: These versatile cells have the potential to differentiate into various cell types within the body. They are broadly categorized into embryonic stem cells (derived from embryos) and adult stem cells (present in adult tissues).
• Epithelial Cells: These specialized cells compose a thin tissue layer called epithelium, which lines surfaces or cavities of tissues. They serve as protective barriers and can be found both on the surface and inside tissues.

Some functions of cell 

1. Movement– muscle and other contractile cells help in movement.
2. Epithelial cells form adhesive and tight junctions between cells
3. Synthesise and secrete components of extracellular matrix
4. Neuron and sensory cells convert physical and chemical stimuli into action potentials.
5. Synthesis and secretion of degradative enzymes
6. Synthesis and secretion of glycoprotein
7. Iron transport
8. Lipid storage