APK 2100C Lecture Notes - Lecture 4: Stratified Squamous Epithelium, Stratum Granulosum, Stratum Spinosum
5 Jul 2016
School
Department
Course
Professor
Document Summary
Contains: skin (largest organ in the body) layers (superficial to deep): epidermis dermis hypodermis (not techically layer) accessory organs (hair, nails, oil/sweat glands) Functions: protection thermoregulation excretion vitamin d production sensory reception. Made of keratinized stratified squamous epithelium cells: keratinocytes (more than 90%) Thin skin areas where little friction develops in most of the skin areas. Stratum corneum: 20-30 layers of dead cells held by membranous keratin-filled sacs. Stratum granulosum: <6 layers of flattened cells; organelles deteriorating, cytoplasm contains lamellar granules that release lipids, keratohyaline granules. Stratum spinosum: multiple layers of keratinocytes held by desmosomes; contain thick bundles of intermediate filaments of pre-keratin. Stratum basale: one row of actively mitotic stem cells; newly formed cells can be come part of superficial layers. Thick skin areas where friction commonly develops (palms, feet, fingertips) 5 epidermal layers stratum lucidum readily visible layer in microscope. Amount of melanin produced affects skin color, not number of melanocytes.
