COMPOUND EPITHELIA (MULTILAYERED EPITHELIA) -

• These are made up of more than one layer of cells.
• The compound epithelia may be stratified and transitinal.

1.      STRATIFIED EPITHELIUM -

• It has many layers of epithelial cells, however, the deepest layer is made up of columnar or cuboidal cells.
• On the basis of the shape of the cells present in the surperficial layers.

It is of four types :-

(i) Stratified Squamous Epithelium -

• The cells in the deepest (= basal) layer are columnar or cuboidal with oval nuclei.
• It is called germinative layer (= stratum germinativum).
• The cells of this layer divide by mitosis to form new cells.
• The new cells gradually shift outward.
• In the middle layers the cells become polyhedral with rounded nuclei.
• These are called intermediate layers.
• The superficial layers are flat with transversely elongated nuclei.
• These layes are called squamous layers.
• It is of two types : (a) Keratinized Stratified Squamous Epithelium.

(b) Nonkeratinized Stratified Squamous Epithelium.

(ii) Stratified Cuboidal Epithelium -

• It has outer layer of cuboidal cells and basal layer of columnar cells.
• It forms the epidermis of fishes and many urodels (tailed amphibians such as salamanders). e.g. ® It also lines the sweat gland ducts and larger salivary and pancreatic ducts.

(iii) Stratified Columnar Epithelium -

• It has columnar cells in both superficial and basal layers.
• e.g. It covers the epiglottis and lines mammary gland ducts and parts of urethra.

(iv) Stratified Ciliated Columnar Epithelium -

• Its outer layer consists of ciliated columnar cells and basal layer of columnar cells. e.g. ® It lines the larynx and upper part of the soft palate.

2.      TRANSITIONAL EPITHELIUM (= UROTHELIUM) -

• This epithelium consists of 4 to 6 layers of cells.
• The cells of deepest (= basal) layer are columnar or cuboidal.
• The cells of middle layer are polyhedral or pear shaped.
• The cells of the surface layer are large and globular or umbrella shaped.
• There is no germinative layer or basement membrane but shows mitosis.
• e.g.  renal calyces, renal pelvis, ureters, urinary bladder and part of the urethra.