Learning Objectives (Lectures1&2) PDF

11 Learning Objectives (Lectures1&2) After you have revised these lectures, you should be able to: 1. Describe the layers of the skin 2. Describe the functions of the skin 3. Understand the basic classif...

11 Learning Objectives (Lectures1&2) After you have revised these lectures, you should be able to: 1. Describe the layers of the skin 2. Describe the functions of the skin 3. Understand the basic classification of burns and potential complications 4. Describe accessory structures of the skin and their function 5. Understand how skin anatomy relates to skin aging, pigmentation, melanoma and tattoo. ©N.Ramesh, 2024  12 Readings from Martini et al., Visual Anatomy & Physiology (3rd ed) The “Integumentary” system : Module 5 (page 224-251) Integumentary system = skin + accessory structures Skin Layers : Module 5.1-5.4 (pages 224-231) Burns: Module 5.5 (pages 232-233) Accessory Structures : Module 5.6-5.9 (pages 235-240) Skin aging: Module 5.10 (page 241) ©N.Ramesh, 2024  13 Word Cloud for Recall (Lectures1&2) ©N.Ramesh, 2024  14 Our bare, sweaty skin… Skin is the largest and most visible organ of the body 16% of total body weight 1.5 - 2 m2 of surface area Product of evolution – ability to sweat makes us unique! Performs complex roles in the body ©N.Ramesh, 2024  15 Functions of skin & accessory structures Protects underlying tissues and organs from abrasions, fluid loss, chemicals etc Excretes salts, water, and organic wastes using glands Temperature regulation by insulation or evaporative cooling as required Produces melanin: protects underlying tissues against UV INTEGUMENTARY SYSTEM Produces keratin: Protection against abrasions & water repellent Synthesize Vitamin D3 (steroid) converted to calcitriol: a hormone important for normal calcium metabolism Lipid storage in adipocytes, some in the dermis and mostly in adipose tissue in the hypodermis Detect touch, temperature, pain, and pressure stimuli and relay the information to the nervous system Adapted from Martini et al., Visual Anatomy and Physiology (3rd ed), ©N.Ramesh, 2024  16 Skin isBut a composite organ first, a little made up of all revision…. 4 tissue-types…. - As we go through the module, try to pick them out! Adapted from Martini et al., Visual Anatomy and Physiology (3rd ed), ©N.Ramesh, 2024  17 Skin consists of 3 primary layers 1. Epidermis Stratified barrier Mostly keratinocytes No blood circulation (avascular) Cutaneous 2. Dermis Protein fibres for strength Vascular (nourishes epidermis) 3. Hypodermis Subcutaneous Adipose tissue ©N.Ramesh, 2024  18 Anatomy of the Skin Adapted from Martini et al., Visual Anatomy and Physiology (3rd ed), ©N.Ramesh, 2024  19 What tissue type is predominant in epidermis? Adapted from Martini et al., Visual Anatomy and Physiology (3rd ed), ©N.Ramesh, 2024  20 Types of Epithelia Simple = Single Stratified = ‘Stacked’ Epidermis is predominantly made of stratified squamous epithelium Adapted from Martini et al., Visual Anatomy and Physiology (3rd ed), ©N.Ramesh, 2024  21 Epidermis Layer Cell type Stratum corneum (spiky layer) Dead, dried-out hard cells without nuclei Contain granules that promote Stratum granulosum (granular dehydration of the cell, crosslinking layer) of keratin fibre Waxy material is secreted into the intercellular spaces Intercellular bridges Stratum spinosum (spinous, called desmosomes link the cells or prickly cell layer) together. The cells become increasingly flattened as they move upward. Contains dendritic (immune) cells. Columnar (tall) regenerative cells. Stratum basale (basal layer) As the basal cell divides, a daughter cell migrates upwards to replenish the layer above. Desmosomes: anchors adjacent/neighboring cells in epidermis Hemidesmosomes: anchors stratum basale to the dermis ©N.Ramesh, 2024  22 Epidermis Layer Cell type Stratum corneum (spiky layer) Dead, dried-out hard cells without nuclei Easily flakes off & can be completely removed Stratum granulosum (granular layer) Contain granules that promote dehydration of the cell, crosslinking of keratin fibres Waxy material is secreted into the intercellular spaces Stratum spinosum (spinous Intercellular bridges or prickly cell layer) called desmosomes link the cells together. The cells become increasingly flattened as they move upward. Contains dendritic (immune) cells. Stratum basale (basal layer) Columnar (tall) regenerative cells. As the basal cell divides, a daughter cell migrates upwards to replenish the layer above. Image adapted from Tajpara et al., (2018) ©N.Ramesh, 2024  23 Thin vs thick skin Palms of hands and soles of feet No hair Extra epidermal layer Stratum lucidum (extra layer for thick skin) Adapted from Martini et al., Visual Anatomy and Physiology (3rd ed), ©N.Ramesh, 2024  24 Epidermis Only found in ’thick- skin’ Dermal papillae are projections from the dermis adjacent to the epidermal ridges. They both increase the surface area and bind the epidermis and dermis closely. Adapted from Martini et al., Visual Anatomy and Physiology (3rd ed), ©N.Ramesh, 2024  25 What’s underneath the epidermis? Adapted from Martini et al., Visual Anatomy and Physiology (3rd ed), ©N.Ramesh, 2024  26 Dermis Situated below the epidermis & anchors via hemidesmosomes Not shed Divided into two layers: - Papillary Layer: Consists of highly vascularised tissues (for nourishment). - Reticular Layer: ‘Mesh-like’ structure of collagen and elastin fibres (for strength) Note: Both layers contain blood vessels, Collagen lymphatics, sensory nerve fibres and accessory fibers structures Elastic fibers Reticular layer of dermis Adapted from Martini et al., Visual Anatomy and Physiology (3rd ed), ©N.Ramesh, 2024  27 Plexuses of the Dermis Cutaneous Plexus: - Network of blood vessels present at Hair the junction of dermis/hypodermis. Papillary layer - Supplies the hypodermis, deeper dermis, including the capillaries for Subpapillary hair follicles and sweat glands. plexus Subpapillary Plexus: - Branches from the cutaneous plexus Cutaneous - Lies deep to the papillary layer of the plexus dermis - Network of blood vessels providing O2 Tip: ‘Plexus’ refers to a ‘network’ of blood vessels and nutrients to the upper dermis and OR nerves epidermis ©N.Ramesh, 2024  28 Hypodermis The ‘subcutaneous’ layer Not considered part of the skin Dominated by adipocytes that produce subcutaneous fat The subcutaneous fat stores energy & provides insulation Common site of injections using hypodermic needles Adapted from Martini et al., Visual Anatomy and Physiology (3rd ed), ©N.Ramesh, 2024  29 First-Degree Burn Superficial i.e only involve the outer layers of the epidermis Red/pink, dry, painful - Erythema. Usually no blisters e.g., a mild sunburn Skin remains a water and bacterial barrier Usually heals 3-10 days Adapted from Martini et al., Visual Anatomy and Physiology (3rd ed), ©N.Ramesh, 2024  30 Second-Degree Burn Normal 2nd degree burns – Epidermis + varying amounts of dermis – Painful, moist, red and blistered. – Usually heal in approx. 1-2 weeks (needs good dressings) Deeper 2nd degree burns – May include whiteish, waxy looking areas – Hair follicles, sweat glands may remain intact – Usually heal in 1 month – May have some loss of sensation and scarring Adapted from Martini et al., Visual Anatomy and Physiology (3rd ed), ©N.Ramesh, 2024  31 Third-Degree Burn Full thickness burns i.e., extend into subcutaneous tissue and may involve muscle and bone Varied color from waxy white through to deep red or black Hard, dry and leathery skin No pain in these areas as sensory nerve endings destroyed May require skin grafting Weeks to regenerate + scarring Adapted from Martini et al., Visual Anatomy and Physiology (3rd ed), ©N.Ramesh, 2024