Answer:
Tissues may be defined as the group of similar cells that combine together to form a similar functions. Four main types of tissues are epithelial tissue, connective tissue, muscle tissue and nervous tissue.
Epithelial tissue are presents on the surface, body lining and lining of mouth and internal organs. The cells of epithelial tissue are one layer thick only. This means epithelial tissue that have the function of absorption are usually thick and has the large surface area that increases the rate of absorption.
Answer: Around 37.2 trillion cells
