There are two common epithelial tissues that are many-layered. Stratified squamous epithelium is many layers of flattened cells. Label and color the basement membrane red, color the cytoplasm blue, and the nuclei purple. There are two major types of stratified squamous epithelium. Keratinized epithelium is found on the skin and is toughened by the protein keratin. Non-keratinized stratified squamous epithelium is found in the oral cavity and vagina and is a mucous membrane.
Another main type of layered epithelial tissue is transitional epithelium. This is tissue that lines part of the urinary tract including the bladder. When the bladder is empty, the cells bunch up on one another and the tissue is thick. When the bladder is full, the cells stretch out into a few layers. Label the cell types for each picture and color the structures in the same way as in previous illustrations.
Answer Key: a. Stratified squamous epithelium, b. Transitional epithelium
There are several types of glands in the human body. Some of these glands secrete their products into tubes or ducts. These are known as exocrine glands. Other glands secrete their products into the spaces between cells where they are picked up by the blood or lymph system. These are the endocrine glands. Endocrine glands secrete hormones that have an impact on target tissues of the body.
Glands can be unicellular or multicellular. Glands that consist of just one cell are called goblet cells. They secrete mucus, which is a lubricant. There are many types of multicellular glands. They are classified by how they secrete their products. Some glands secrete products from vesicles pinched off from the cell. These are called merocine glands. In these glands no cellular material is lost in the secretion of material. An example of a merocrine gland is a sweat gland. Some cells squeeze parts of the cell off to secrete cellular products. These are known as apocrine glands. The lactiferous glands that produce milk are apocrine glands. Some secretions occur by the entire cell rupturing. These are called holocrine glands. Oil glands of the skin are holocrine glands. Label the glands and color them in on the figure.
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This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.