BIO 1300 Lecture Notes - Lecture 4: Stratum Granulosum, Stratum Spinosum, Stratum Corneum
14 Mar 2018
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Document Summary
Evolution from sh to amphibia: skin becomes very important feature. Amphibia: aquatic and terrestrial environments but lack features that allow them to live entirely on land. Dessication: process by which things dry (amphibian skin dries out on land) Reptiles had what amphibia lacked: internal fertilization, hard-shelled eggs, and impermeable scaly skin which is one of main features which gave rise to their domination of. Reptilian dinosaurs were birds and had keratinized extensions (feather) Mammals have keratin extensions (hair and by de nition it is a mammalian trait) Skins is very important and plays a key role in our evolution and it is a very important organ. Can be mechanical protection (abrasions etc. ) or chemical protection (against acids etc. ) Trapping heat within (endothermic/ectothermic) and maintaining homeostasis. See outer most layer which is the stratum corneum (dead cells) Contain keratinocytes (keratin), melanocytes (melanin), langerhaus cells (immune system), and merkel cells (light touch receptors.
