Skin and Skin Appendages PDF

# Skin and Skin Appendages (Integumentary System) ## The Skin - Hair - Sebaceous gland - Sensory nerve ending - Epidermis - Nerve - Dermis - Subcutaneous tissue - Fat, collagen, fibroblasts - Capillaries - Muscle - Sweat gland - Arteriole ## Skin appendages ## Objectives At the end of...

# Skin and Skin Appendages (Integumentary System) ## The Skin - Hair - Sebaceous gland - Sensory nerve ending - Epidermis - Nerve - Dermis - Subcutaneous tissue - Fat, collagen, fibroblasts - Capillaries - Muscle - Sweat gland - Arteriole ## Skin appendages ## Objectives At the end of this lecture, you will be able to: 1. Define skin appendages 2. Describe the structure of sweat gland, sebaceous gland, and mammary gland ## The Sebaceous Glands 1. Holocrine glands in the dermis of the skin mainly in the face, forehead, and scalp. 2. Secretes sebum. 3. Acini (alveoli) have rounded vacuolated cells containing excess fat droplets in their cytoplasm. 4. The cells burst during secretion. 5. The ducts open in the upper part of the hair follicle. ## The Sweat Glands - **Site:** in the dermis - **Types:** - **Merocrine sweat glands** are present allover the body, open on the epidermal surface. - **Apocrine sweat glands** found in the axilla, anogenital region, open in the hair follicles, not on the epidermal surface. - **Morphology:** simple coiled tubular gland having secretory part & a duct. - **The secretory part:** contains 3 cell types: - **Dark cells:** secrete sweat. - **Clear cells:** ion transporting cells. - **Myoepithelial cells**. - **Duct:** is lined by double layer cuboidal epithelium. ## The Mammary Gland - **Definition:** - The mammary gland is considered as a modified apocrine sweat gland. - The mammary gland shows structural variations according to the age of the female and the activity of the gland. - **Adult mammary gland structure:** - Two different states of the adult mammary gland are identified: resting, lactating - The female breast is composed of: 1. **Nipple:** conical projection of dense CT rich in smooth muscle fibers & nerve fibers. 2. **Areola:** dark pigmented skin area around the nipple 3. **Breast proper:** - **Breast proper (parenchyma of the breast)** - It is formed of several separate lobes (12-20) radiating from the nipple, separated by thick dense CT septea rich in fat cells. - Each lobe is with its own excretory lactiferous duct, that emerges separately in the nipple is considered as a gland in itself. - Each lobe consists of secretory acini draining into several extensively branching ducts that converge & empty into one separate large lactiferous duct. The ducts are embedded in abundant loose. - **I. Resting mammary gland** - The amount of the CT & Fat and the development glandular tissue are the major elements the are changed during the resting and lactating states of the breast. - More connective tissue and less glandular tissue. - The glandular elements (alveoli) are tubular (duct like) and lined by cubical epithelium. Some of them may be in form of solid cords of cells (not well developed). - Branching of duct system - **II. Lactating mammary gland** - The glandular elements proliferate so, more prominent than the CT. - The interlobular CT septum is very thin. - The glandular element is well developed in the form of closely arranged spherical alveoli. - The alveoli are lined by simple cuboidal secretory epithelium and surrounded by myoepithelial cells. Their lumen contains milk which appear acidophilic & vacuolated (fat droplets). - Extensive branching of the duct system. ## Recommended references & Websites - Junqueira's Basic Histology: Text and Atlas, Thirteenth Edition 2013 - ISBN-13: 978-0071780339 - ISBN-10: 0071780335 Edition: 13th - The histology tutor: http://www2.yvcc.edu/histologyzoomer/Histology Tutorials/histology_tutorials.htm.