SIMPLE EPITHELIUM 25 



(1) Squamous or pavement. Cells flattened. 



(a) Non-ciliated. Alveoli of lungs, also includes endothelium, 

 lining the blood vessels, and mesothelium, lining the large 

 serous spaces. 



(b) Ciliated. The peritoneum of some forms at breeding season. 



(2) Cubical epithelia. Cells with the three dimensions approxi- 



mately equal, mainly glandular. 



(a) Non-ciliated. The usual type. It is found lining both 

 ducts and secretory portions of most glands, the pigmented 

 layer of the retina, etc. 



(b) Ciliated. Not common. Lining of some of the smaller 

 bronchial tubes. 



(3) Columnar. Cells may be cylindrical, conical, or goblet-shaped. 



(a) Non-ciliated. Intestinal. 



(b) Ciliated. Fallopian tube and uterus. 



(c) Pseudo-stratified. Smaller bronchi, nasal duct, etc. 

 2. Stratified epithelia. Cells more than one layer in thickness. 



(1) Squamous. Surface cells flattened. 



(a) Non-ciliated. Skin, mouth, vagina, etc. 



(b) Ciliated. Pharynx of embryo. 



(2) Columnar. Surface cells columnar. 



(a) Non-ciliated. Portions of male urethra. 



(b) Ciliated. Trachea, bronchi, etc. 



II. Epithelia not in the form of membranes, but in solid masses or cords, 

 usually glandular. 



(1) Cells spheroidal. Ova. 



(2) Cells polyhedral. Liver, suprarenal, etc. 

 Epithelia, classified mainly as to function. 



I. Protective. Skin, mouth, alimentary canal. 



1. Cornified. Skin, nails, hair. 



2. Cuticular border. Columnar cells of intestine. 

 II. Glandular. 



1. Secretory. Cells of salivary glands, pancreas, etc. 



2. Excretory. Cells of kidney. 



3. Absorptive. Cells of alimentary canal. 



III. Sensory Epithelium. Cells of olfactory membrane, organ of Corti, 



taste buds, etc. 



IV. Reproductive. Sex cells. 



V. Pigmented. Pigmented layer of retina. 

 VI. Ciliated. Trachea, uterus, Fallopian tube, etc. 

 Only a few of the more important of the above-mentioned types of epithe- 

 lium will be described here. 



Simple Epithelium. Simple Squamous. This form of epithelium 



