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Saladin Anatomy and Physiology The Unity of Form and Function Episode 4

Tham khảo tài liệu 'saladin anatomy and physiology the unity of form and function episode 4', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | I Text Saladin Anatomy Physiology The Unity of Form and Function Third Edition 6. The Integumentary System The McGraw-Hill Companies 2003 Chapter 6 194 Part Two Support and Movement c Figure 6.3 Layers of the Dermis. a Light micrograph of axillary skin with the collagen stained blue. fa The papillary layer made of loose areolar tissue forms the dermal papillae. c The reticular layer made of dense irregular connective tissue forms the deeper four-fifths of the dermis. Figures b and cfrom R. G. Kessel and R. H. Kardon Tissues and Organs A Text-Atlas of Scanning Electron Microscopy W. H. Freeman 1979 . upward however they cease dividing. Instead they produce more and more keratin filaments which cause the cells to flatten. When skin is histologically fixed keratinocytes shrink and pull away from each other but remain attached to their neighbors by several desmosomes. These create bridgelike extensions where one keratinocyte reaches out to another across the gap a little like two people holding hands while standing farther apart. These bridges give the cells the spiny appearance for which the stratum spi-nosum is named. The stratum spinosum and stratum granulosum also contain dendritic3 Langerhans4 cells. These are macrophages that arise in the bone marrow but migrate to the stratified squamous epithelia of the epidermis oral cavity esophagus and vagina. The epidermis has as many as 800 dendritic cells per square millimeter. They help to 3dendr tree branch 4Paul Langerhans 1847-88 German anatomist protect the body against pathogens by capturing foreign matter and presenting it to the immune system for a response. Stratum Granulosum The stratum granulosum consists of two to five layers of flat keratinocytes more in thick skin than in thin skin. These keratinocytes contain coarse dark-staining kerato-hyalin granules that give this layer its name. These granules consist of a protein that combines with intermediate filaments of the cytoskeleton and converts them to .