Chapter 2 Tissues and body cavities
Epithelial tissue or epithelium covers the surface of the body and the organs, cavities and tubes within it – it covers the internal and external surfaces of the body. Its main function is to protect delicate structures lying beneath it but in some areas the epithelium may be secretory, e.g. glands, or absorbent, e.g. in the small intestine. The epithelium lining structures such as the inside of the heart, blood vessels and lymph vessels is referred to as endothelium.
The thickness of the epithelium reflects its ability to protect: the more layers of cells, the more protection is provided. The epithelium on the footpads consists of many layers of cells providing protection when walking on rough surfaces, while the epithelium over the abdominal wall is only a few cells thick and additional protection is provided by fur. Further protection may be provided by the presence of the protein keratin. The epithelium is described as being a keratinised stratified epithelium and this type can be seen in claws and nails.
(Taken from D. Samuelson. Textbook of Veterinary Histology. Saunders. 2007, p 42.)
The full classification of the type of epithelium is based upon the shape of the cell and the number of layers present. There are a number of different types of epithelial tissue in the body, these include:
(Taken from D. Samuelson. Textbook of Veterinary Histology. Saunders. 2007, p 43.)
(Taken from D. Samuelson. Textbook of Veterinary Histology. Saunders, p 64.)
Connective tissue is responsible for supporting and holding all the organs and tissues of the body in place. It also provides the transport system within the body, carrying nutrients to the tissues and waste products away. Connective tissue consists of cells embedded in an extracellular matrix or ground substance. The properties of this ground substance depend on the type of connective tissue. There are many types of connective tissue which, in order of increasing density are: