Classification according to function Surface epithelium Glandular epithelium Distribution : covers all inner and outer surfaces of the body skin and mucous membranes Exception: synovial membrane synovium The synovial membrane is composed of synoviocytes not epithelial cells! Formation : Different types of epithelia are formed from the three germ layers. Ectoderm : epithelium of skin and skin appendages Mesoderm Epithelium of serous membranes mesothelium : peritoneum , pleural, and pericardial cavities Cells lining the inner surface of blood and lymphatic vessels endothelium Endoderm : epithelium of the respiratory and gastrointestinal tract Surface epithelium Definition : A specialized layer of tissue formed by closely aggregated cells that line the outer surface of organs, blood vessels, the skin , and the inner surface of body cavities.
Divided into squamous, cuboidal, and columnar types. Criteria for classification Layers Simple epithelium : a single layer of epithelial cells with all cells attached to the basement membrane Pseudostratified epithelium : a single layer of cells with the appearance of multiple layers as a result of the nuclei positioned at different levels Stratified epithelium : two or more cell layers with the basal layer attached to the basement membrane Cell shape Explanation : The cell shape of the upper cell layer of a type of epithelium determines the name for the whole epithelium.
Examples: skin , esophagus , cervix , serous membrane e. Examples: bile ducts , renal tubules Column-shaped columnar epithelium Appearance: Upper cells have a rectangular or cylindrical shape width. Examples: intestine , respiratory tract respiratory epithelium Epithelial specialization Keratinization horny layer Specialization on the surface of epithelial cells can be differentiated into the horny layer keratinization and cell projections microvilli , stereocilia , kinocilia.
Keratinized epithelium is only found on the skin stratum corneum. The epidermis is a keratinized stratified squamous epithelium. References Standring S. Elsevier Health Sciences ; Finger-shaped, non-active motile projections on the apical surface of epithelial cells. Eyelash-shaped, active motile projections on the apical surface of epithelial cells. Inner structure composed of actin filaments Cross-linkage by fimbrin. These hormones are secreted by the endocrine system. Endocrine glands do not have ducts.
Their secretions hormones are secreted into the blood stream. Because of this, the hormones can act over long distances, and reach any organ in the body to co-ordinate activity. Often there is a specific 'target' organ that the hormone acts on. This long range activity is also often called neuroendocrine - as it is somewhat analogous to the co-ordinating activity of neurones. Some short range endocrine activity also occurs in the digestive system - and this is known as paracrine activity - for example enteroendocrine cells of the gut respond to activity by secreting peptides of monoamines that act locally.
The secretory cells of endocrine glands are therefore always found in close proximity to a capillary bed, and have a rich network of blood vessels. Chapter First Online: 08 September Keywords Glands Glandular epithelium Exocrine glands Endocrine glands Goblet cells Constitutive secretion Regulated secretion Merocrine secretion Apocrine secretion Holocrine secretion End pieces Duct system Myoepithelial cells Secreting epithelial surface Intraepithelial glands Mucous secretion Serous secretion Hormone receptors Hormones Follicular endocrine tissue Trabecular endocrine tissue.
This is a preview of subscription content, log in to check access. Genesers Histologi. Munksgaard; Google Scholar. The glandular tissue are a mixture of both endocrine ductless, hormones are secreted into the blood and exocrine have ducts, hormones are secreted onto surfaces glands. The exocrine glands are covered in the respective topics.
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