# Simple Epithelia --- **Simple epithelia** are types of [[epithelial tissue]] that have one single layer of cells, all of which are attached to the [[basement membrane]]. They come in *simple squamous*, *simple cuboidal* and *simple columnar*, with a bonus of *pseudostratified columnar. ```mermaid graph LR B(simple<br>epithelium) C(simple<br>squamous) D(simple<br>cuboidal) E(simple<br>columnar) F(ciliated) G(nonciliated) H(pseudostratified<br>columnar) B --> C & D & E & H E --> F & G ``` #### Simple Squamous **Simple squamous epithelia** are about as thin as you can get, and are perfect for very fast materials exchange, i.e. filtration, absorption, excretion, gas exchange. For this reason they are found in places like the [[lungs|alveoli]], and in the lumen of blood vessels. ![[simple squamous.png]] Some simple squamous tissues have specific names based on where they are located. - The **mesothelium** is the name of the simple squamous tissue that forms [[serous membrane|serous membranes]]. - The **endothelium** is the simple squamous tissue that lines the insides of [[blood]] and [[lymphatic vessels|lymphatic]] vessels. #### Simple Cuboidal **Simple cuboidal epithelia** are pretty straightforward: they're a row of boxy cells that are used for absorption and secretion. They form most of the [[gland|glands]] and small ducts of the body, and the walls of the [[kidneys]]. ![[simple cuboidal.png]] #### Simple Columnar **Simple columnar epithelia** are taller than they are wide, and can be divided into *ciliated* and *noncilliated* versions. Both versions may or may not have [[goblet cell|goblet cells]]. **Ciliated simple columnar epithelium** have [[cilia]], and function not only to secrete [[goblet cell|mucin]], but to move mucous but also things like eggs through the [[uterus|uterine tubes]]. ![[ciliated simple columnar.png]] **Nonciliated simple columnar epithelium** do not have cilia but they usually have [[microvilli]], or a brush boarder. They live in the intestines and function to secrete [[goblet cell|mucin]] and help absorb nutrients as [[enterocytes]]. ![[nonciliated simple columnar.png]] #### Pseudostratified Columnar **Pseudostratified columnar epithelia** may appear at first glance as if they were stratified columnar, but in fact they are simple—each cell does attach to the basement membrane, but does not necessarily reach the apical surface. It can be difficult to tell especially because the nuclei are all at various levels. It serves a protective function, and like simple columnar, it comes in ciliated and nonciliated forms, but unlike simple columnar, only the ciliated version has [[goblet cell|goblet cells]]. **Ciliated pseudostratified columnar epithelium** serves as protection and the secretion of mucin to move debris out of the respiratory tract. ![[ciliated pseudostratified.png]] **Nonciliated pseudostratified columnar epithelium** is quite rare, and does not produce mucin. It's only found lining part of the male urethra and epididymis. ![[nonciliated pseudostratified.png]] ___