What are the four types of tissue?
Answer
Our body is made up of 30 trillion cells. From them, they can be grouped into 200 cell types for example: bone cells, lung cells, blood cells, nerve cells etc. These 200 cell types can be further grouped into four tissue types: epithelial, connective, muscular, and nervous. Starting with epithelial tissues. These consist of cells with a continuous shape in a single layer of thickness, which we call simple epithelium, or in a multi-layer thickness, which we call stratified. Epithelial tissue can be further categorized by its shape. If cells are flat-looking, they are called squamous. If they look like a box, they are called cuboidal. If they are shaped long and slender, they are called columnar. Now if these cells were a simple epithelium, their function would be diffusion, secretion, and absorption. For instance, in the lungs the alveoli tissue is simple squamous; they are there to absorb oxygen into the blood. If it's a simple cuboidal cell in the gastrointestinal tract, they are there to secrete enzymes to aid in digestion. If it's a simple columnar cell, they are there in the lining of the intestine; they are there to absorb nutrients. Now if it is stratified squamous, like in the skin, then that is there for protection.
Connective tissue is the second type of tissue. Connective tissue is made up of two main parts: the extracellular matrix (ecm) and cells. The ECM is made up of fibers such as collagen and elastin and gels like ground substance. If it's a fluid type of connective tissue, which means it's got a lot of fluid in its gel then it would be blood. If it's semi-solid or gelatinous, this would be loose connective tissue such as fat. If it is a real dense tissue where it has compact fibers then this could be something like bones or ligaments.
Muscular tissue is made up of myocytes that generate movement. Skeletal muscle attaches to bone. When it contracts, it helps to move the skeleton and generates body movement. The second type of muscle is cardiac muscle, which is made up in the heart. When it contracts, it pushes blood out into the rest of the body. The third type of muscle is smooth muscle, which is found in the walls of hollow organs such as in the intestine or blood vessels. It would help to move food along the intestine or blood along the blood vessels.
Nervous tissue is made up of two types: neurons and glia. Neurons receive stimuli. Convert that into electrical activity. Then send that electrical impulses to other neurons, muscles, or glands. Glia helps to support the neurons.
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