UM1010 MCB Integumentary System PDF

Dr Katja Vogt Integumentary System @katjetz [email protected]  Dr Katja Vogt I will use the traffic light system through out my slides to help you evaluate the significance of the material @katjetz [email protected] ...

Dr Katja Vogt Integumentary System @katjetz [email protected]  Dr Katja Vogt I will use the traffic light system through out my slides to help you evaluate the significance of the material @katjetz [email protected]  Dr Katja Vogt Today we are going to… … define the structure and function of the skin … explore different cell types within the skin … identify the layers of the skin … highlight the structure and function of the basement membrane and dermis … interpret the hair cycle … investigate the apendages of the integumentary system appendages: nerve cells; nails; sweat glands @katjetz [email protected]  Dr Katja Vogt The Integumentary System 1. Skin & its appendages 5. Glands: sweat, wax, oil glands 2. Hair 6. Mammary glands 3. Nails 7. Teeth 4. Sense receptors @katjetz [email protected] Pathology of the Skin Dr Katja Vogt Solar (Actinic) Keratosis Solar (Actinic) Keratosis Solar (Actinic) Keratosis @katjetz [email protected] Pathology of the Skin Dr Katja Vogt Superficial spreading Amelanotic melanoma Melanoma of the nail unit malignant melanoma arising within pigmented melanoma Amelanotic melanoma Metastatic melanoma @katjetz [email protected]  Dr Katja Superficial layer of stratified squamous epithelium (noVogt blood vessels), which acts as physical & chemical barrier Structure of the Skin Acid mantle Created by acidic substances e.g. amino acids, lactic acid and fatty acids in perspiration, sebum and hormones Friction ridges Criss-crossing ridges and valleys Regular protrusions of the epidermis layer (rete ridges) into the upper layers of the underlying dermis Invaginations due to follicles and sweat duct ostia Epidermis Basement membrane zone Dermis Subcutaneous tissue @katjetz [email protected]  Dr Katja Vogt Cell Types in skin - overview Epidermis has 3 main types of cell: Keratinocytes (skin cells) Melanocytes (pigment-producing cells) Langerhans cells (immune cells) Merkel cell (neuroendocrine cells) @katjetz [email protected]  Dr Katja Vogt Cell Types - Keratinocytes make up 95% of the skin surface Normally renewed every 15 to 30 days Created in the basal layer and gradually move towards surface Become more differentiated as they move upwards Produce the protein keratin in large amounts Keratin (intermediate filament) is tough and very resistant to water Keratinization: Replacement of cell contents with the protein keratin @katjetz [email protected]  Dr Katja Vogt Cell Types - Melanocytes Precursors melanoblasts are derived from the neural crest cells Migrate to skin, inner ear, uveal tract and substantia nigra Highly dendritic, heavily pigmented cells Produce melanin to protect the skin from UV Melanin is responsible for different skin/hair colour Melanin is packaged into small parcels (or melanosomes), which are then transferred to keratinocytes Melanocyte stem cells reside in hair follicle bulge @katjetz [email protected]  Dr Katja Vogt Cell Types – Langerhans cells First line of immunologic defence in the skin Specific dendritic cells ~5% of the cells within the epidermis Characterised by cytoplasmic Birbeck granules Migrate to the lymph nodes Responsible for allergen recognition Present antigens to lymphocytes (interact through specific surface receptors) @katjetz [email protected]  Dr Katja Vogt Epidermal Layers 1. Stratum corneum (horny layer) 2. Stratum lucidum (NOT seen in thin epidermis) Malphigian Layer 3. Stratum granulosum (granular cell layer) 4. Stratum spinosum (spinous or prickle cell layer) 5. Stratum basale (basal or germinativum cell layer) @katjetz [email protected]  Dr Katja Vogt Stratum Basale Located adjacent to dermis Consists of mainly dividing and nondividing keratinocytes Melanocytes present (1:10 to Keratinocytes) Merkel cells present in very low numbers even in sensitive areas @katjetz [email protected]  Dr Katja Vogt Stratum Spinosum 5-12 layers of polygonal keratinocyte cells that become flatter near surface Communicate with surrounding keratinocytes, melanocytes and Langerhans cells Cells are connected by desmosomes Langerhans cells predominantly found here @katjetz [email protected]  Dr Katja Vogt Stratum Granulosum (+Lucidum) Stratum lucidum 3- 5 layers of flattened cells 2-3 cell layers Thin clear layer consisting of eleidin Anucleated and losing cytoplasm Filled with irregular dark keratohyaline granules @katjetz [email protected]  Dr Katja Vogt Stratum Corneum flattened dead cells (corneocytes) with no nuclei or organelles extracellular space of the cells is surrounded by lipidic bilayers 10±30 layers of stacked corneocytes in most areas of skin Palms and soles have thickest layer @katjetz [email protected]  Dr Katja Vogt Basement Membrane aka basal lamina Thin, dense sheets of specialized, self-assembled extracellular matrix Helps to attach and anchor the cells to the underlying connective tissue. 2 independent polymeric networks Laminin Type IV collagen 3 distinct layers: Lamina lucida Lamina densa Lamina reticularis (sometimes also seen as own entity) @katjetz [email protected]  Dr Katja Vogt Dermis Fibrous connective tissue Normal cells in the dermis include: Mast cells Vascular smooth muscle cells Fibroblasts Epidermis and dermis communicate through release of cytokines and chemotactic factors Dermis houses the sweat glands, hair, hair follicles, muscles, sensory neurons, and blood vessels. @katjetz [email protected]  Dr Katja Vogt Layers of the dermis Papillary Layer Composed of loose connective tissue and blood capillaries most of the touch receptors located here as well. Reticular layer Composed of interlacing bundles of collagen and elastin. Gives it strength, elasticity, and extensibility. Binds the epidermis to the subcutaneous layer. Collagen and elastin bundles give it strength and elasticity. Lines of tension are formed from these bundles forming patterns under the skin. @katjetz [email protected]  Dr Katja Vogt Nerve Tissue within the Dermis Within the dermis are numerous nerve fibres both motor and sensory. All of the touch receptors are located within the dermis as well. Pacinian corpuscle- heavy pressure Meissner’s corpuscle- light touch Merkel’s disc- light touch Ruffini’s corpuscle- touch, heat @katjetz [email protected]  Dr Katja Vogt Hair Is present on all skin surfaces Develops from a group of epidermal cells called a hair follicle. Soft, short and pale hair: vellus hair Hard large, long, dark hair: terminal hair Extends down into the dermis some even into the subcutaneous layer @katjetz [email protected]  Hair growth cycle Dr Katja Vogt @katjetz [email protected]  Dr Katja Vogt Sweat Glands Most numerous in the palms and soles. Originate from the dermis or subcutaneous layer. Apocrine sweat gland Eccrine Sweat Glands Found in virtually all skin. Respond to elevated body Respond to emotional stress temperature. and sexual stimulation. Most numerous on forehead, Concentrated at the axilla neck and back. and groin found only with Produce perspiration that is hair follicles very dilute, water and NaCl. Salt is actually reabsorbed within the duct. @katjetz [email protected]  Dr Katja Vogt Can you… … define the structure and function of the skin? … explore different cell types within the skin? … identify the layers of the skin? … highlight the structure and function of the basement membrane and dermis? … interpret the hair cycle? … investigate the appendages of the integumentary system: nerve cells; nails; sweat glands? MBBS learning outcomes Recognise the structure, function and histology of the skin and its accessory organs @katjetz [email protected]  Dr Katja Vogt References / further reading Integument - Textbook of Histology Gartner, Leslie P., PhD; Textbook of Histology, Chapter 14, 333-354.e2 Microanatomy of the skin - Dermatology: An Illustrated Colour Text; Gawkrodger, David J., DSc MD FRCP FRCPE; Ardern-Jones, Michael R., BSc MB BS DPhil FRCP; Dermatology: An Illustrated Colour Text, 1, 1-3 @katjetz [email protected]