tailieunhanh - Ebook diFiore's atlas of histology - With functional correlations (12th edition): Part 2

(BQ) Part 2 book "diFiore's atlas of histology - With functional correlations" presents the following contents: Integumentary system, digestive system part I - oral cavity and major salivary glands, digestive system part II - esophagus and stomach, digestive system part III - small intestine and large intestine, respiratory system,. | HAPTER 12 Integumentary System General Overview Skin is the largest organ in the body. Its derivatives and appendages form the integumentary system. In humans skin derivatives include nails hair and several types of sweat and sebaceous glands. The surfaces of the body are covered either by thin skin or thick skin. Skin or integument consists of two distinct regions the superficial epidermis and a deep dermis. The surface layer of the skin or the epidermis is nonvascular and is lined by keratinized stratified squamous epithelium with distinct cell types and different cell layers. Inferior to the epidermis is the vascular dermis characterized by dense irregular connective tissue blood vessels nerves and different glands. In some areas of the body numerous hair follicles are visible in the dermis. Beneath the dermis is the hypodermis or a subcutaneous layer of connective tissue and adipose tissue that forms the superficial fascia seen in gross anatomy. Dermis Papillary and Reticular Layers Dermis is the inferior connective tissue layer that binds to the epidermis. A distinct basement membrane separates the epidermis from the dermis. In addition the dermis contains epidermal derivatives such as the sweat glands sebaceous glands and hair follicles. The junction of the dermis with the epidermis is irregular. The superficial layer of the dermis forms numerous raised projections called dermal papillae which interdigitate with evaginations of the epidermis called epidermal ridges. This region of the skin is the papillary layer of the dermis. It contains loose irregular connective tissue fibers capillaries blood vessels fibroblasts macrophages and other loose connective tissue cells. The deeper layer of the dermis is called the reticular layer. This layer is thicker and is characterized by dense irregular connective tissue fibers mainly type I collagen and is less cellular than the papillary layer. Also this layer of the dermis can withstand more mechanical stresses and can