Stratified Squamous Epithelium consists of squamous(flattened) epithelial cells arranged in layers upon the basement membrane. A single layer is in contact with the basement membrane while the other layers adhere to one another in order to maintain structural integrity. Despite being referred as squamous, many cells within the layers may not be flattened; this is due to the conventional naming of epithelia based on the cell type at the surface. In the deeper layers, the cells may be columnar or cuboidal.
The stratified squamous epithelium is well suited to areas of the body subjected to constant abrasion. Since this is the thickest, layers can be sequentially sloughed off and replaced before the basement membrane is exposed. Hence, the main function of this type of epithelia is for protection.
The stratified squamous epithelium may either be keratinized or non-keratinized. Keratin is a tough protective protein found at the apical surface.
The non-keratinized stratified squamous epithelium include the oral cavity, vagina, oesophagus, etc. The non-keratinized type must be kept moist by bodily secretions to prevent them from drying out.
The keratinized stratified squamous epithelium include the outer layers of the skin.
2. Stratified Cuboidal Epithelium
Stratified cuboidal epithelium is a rare type of epithelial tissue which consists of cube-shaped cells that are arranged in mmultiple layers.
The chief function of this type of epithelial tissue is to provide protection.
They are found in the larger ducts of various glands such as the sweat glands as well as the mammary glands.
3. Stratified Columnar Epithelium
Stratified columnar epithelium is a rare type of epithelia. The upper layer of this type of epithelia consists of column-shaped cells while the lower layers are made up of cube-shaped cells. They also contain specialized secretory cells called goblet cells that stores mucus.
The main function of this type of epithelia is for protection and secretion of mucin(mucin is a heavily glycosilated protein which helps in forming chemical barriers, lubrication and cell signalling).
The stratified columnar epithelia are found in the intralobular ducts in the salivary glands, the male urethra, and the female'r uterus.
4. Trnsitional Epithelium
The transitional epithelium or also known as the 'urothelium' is a type of epithelial tissue that consists of multiple layers of epithelial cells that can contract and expand. These cells appear cuboidal in shape with a domed apex when the organ or tube they reside in is not stratched. When the bladder is filled, the compress and the cells become stratched giving them a squamous appearance.
The main function of this epithelia is for protection and distensibility.
The transitional epithelia is found in the inner lining of the urinary bladder, ureter and part of the urethra.
No comments:
Post a Comment