Integumentary System Histology

	INTEGUMENTARY SYSTEM ©David B. Fankhauser, Ph.D. Professor of Biology and Chemistry University of Cincinnati Clermont College, Batavia OH 45103
thin skin a cross section, labeled	This page has been accessed times since 15 October 2001. rvsd 22 October 1992, 18 Oct '94, 12 Sept '95, 23 Sept.'96, 22 Sept '97, 14 Sept 99,19 Sept 00, 4 Oct 01	epidermis a keratinized stratified squamous epithelium

The skin is the largest organ of the body. It gets its strength and nourishment from the underlying dermis, a dense irregular connective tissue (previously seen in the Connective Tissues Lab ). It is protected by an outer covering of epidermis, a keratinized stratified squamous epithelial tissue. Numerous accessory organs are associated with it, notably sweat glands, hair follicles, sebaceous glands, and nerve endings. Note that all but the nerve endings originate from the epithelial layer. We will spend considerable time studying a single slide to understand the structure and functioning of the features of this crucial barrier between the external environment and our vital inner organs.

Make three illustrations:

100x view showing the overall relationships of the epidermis, dermis and accessory structures as listed in the left column below.
400x view of a strand of hair
400x view of the epidermis , labeling its various layers, according to the list in the right column.

Contrast with the mucous membrane of the esophagus , a non-keratinized stratified squamous epithelium which you studied as part of the Epithelial Tissues Lab (slide #5). Non-keratinized stratified squamous has nuclei all the way to the apical surface.

All images are from slide 15 in the slide collection : Skin, mammal. See VE's 9^th: pp 143-149

Click image to enlarge
hair follicle: hair bulb:	1) Hair follicle & accessory organs at 100x (VE's 9^th: fig 9-4, p 143) Note that the epithelial lining of the hair follicle is continuous with the epidermis. Nourishment for the growing hair is derived from a dermal projection into the hair bulb called the papilla. The epithelial cells which produce a hair are the matrix. Another accessory organ of the integument associated with the hair follicle is the sebaceous gland. This holocrine produces sebum, an oil which conditions the hair and skin, and whose fatty acids restrict bacterial growth on the epidermis. Here is a labeled hair follicle, etc .	epidermis dermis sweat gland (only in c.s.?) hair follicle: epithelial lining hair bulb papilla of follicle matrix of hair hair medulla hair cortex sebaceous gland arrector pili
	2) Cross section of a hair at 400x The cortex consists of tough consolidated "scales" of keratin. The medulla is less densely organized, and is hollow in some species, adding to insulating quality of the hair (polar bear).	medulla cortex flattened, flaking cells
epidermis thin skin: epidermis from pig ear:	3) *Features of the epidermis per se* at 400x:** (VE's 9^th: fig 9-11, p 149) Here is a labeled view of the epidermis at 1000x. Epidermis is a keratinized stratified squamous epithelium which affords protection from a harsh environment primarily due to the keratin of which the outer stratum corneum is composed. "Invented" by reptiles, a coat of keratin freed them from the dependence on aquatic environment because it prevents dehydration in the air. Its indigestibility also resists microbial growth. Nourishment of the avascular edpidermis is through the well vascularized papillary layer of the dermis. The lower image demonstrates the flaking nature of the stratum corneum.	epidermis and its layers: stratum corneum stratum germinativum: stratum spinosum stratum basale melanocytes (any mitotic figures?) dermis and its features: fibroblasts collagenous fibers capillaries sweat gland duct (only cs?) These thin skin sections may lack obvious: stratum lucidum stratum granulosum dermal papilla

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INTEGUMENTARY SYSTEM