Bio10004 Anatomy and Physiology 2024 Integumentary System PDF

Bio10004 – Anatomy and Physiology 2024 The Integumentary system Dr. Greg Davis (Designed by Dr.ALI AL-RUBAIE) Department of Health Sciences and Biostatistics  Learning objectives At the end of this lecture you should be able to: 1. K...

Bio10004 – Anatomy and Physiology 2024 The Integumentary system Dr. Greg Davis (Designed by Dr.ALI AL-RUBAIE) Department of Health Sciences and Biostatistics  Learning objectives At the end of this lecture you should be able to: 1. Know the functions of the integumentary system, the general functions of the epidermis, dermis, subcutaneous layer of the skin and the related functions for accessory structures in the integument. 2. Identify the five layers of the epidermis, the two layers of the dermis. 3. Explain how the skin responds to injury and the steps of regeneration of the skin after an injury. 4. Be able to describe sebaceous, sweat, mammary and ceruminous glands in the skin, their functions and secretion. 5. Know the structure of a hair follicle and be able to describe a typical strand of hair. 6. Briefly be able to summarise what tension lines of the skin are. The Integumentary System  The Integument The integument is the largest system of the body: – 16% of body weight – 1.5 to 2 m2 in area Made up of: – Cutaneous membrane (skin) – Accessory structures Exocrine gland Hair Nail  Parts of the Cutaneous Membrane Outer epidermis: – superficial epithelium (epithelial tissues) Inner dermis: – connective tissues https://www.researchgate.net/figure/Structure-of-skin-Epidermis-The-epidermis-the-outermost-layer-of-skin-provides-a_fig1_316939986  Accessory Structures Originate in the dermis Extend through the epidermis to skin surface: – hair – nails – multicellular exocrine glands  The subcutaneous Layer Subcutaneous layer (hypodermis): – loose connective tissue – Deep (below) the dermis – location of hypodermic injections  Functions of Skin Protects underlying tissues and organs Excretes salts, water, and organic wastes (glands) Maintains body temperature (insulation and evaporation) Synthesises vitamin D3 Stores lipids Detects touch, pressure, pain, and temperature Organization of the Epidermis under the eyes heel of the foot  Layers of the Epidermis From basal lamina to free surface: – stratum germinativum – stratum spinosum – stratum granulosum – stratum lucidum – stratum corneum https://courses.lumenlearning.com/wm-biology2/chapter/epidermis/ –Keratinised stratified squamous epithelium – 15–30 days for a cell to move from stratum germinosum to corneum  Stratum Germinativum The “germinative layer”: – has many germinative (stem) cells or basal cells – is attached to basal lamina by hemidesmosomes – forms a strong bond between epidermis and dermis  Structures of Stratum Germinativum Epidermal ridges –fingerprints Dermal papillae – tiny mounds – increase the area of basal lamina – strengthen attachment between epidermis and dermis Figure 5–3c  Stratum Corneum The “horn layer”: – exposed surface of skin – 15 to 30 layers of keratinized cells – water resistant – shed and replaced every 2 weeks  Keratinisation The formation of a layer of dead, protective cells filled with keratin Occurs on all exposed skin surfaces except eyes Keratinocytes: – contain large amounts of keratin – the most abundant cells in the epidermis  Skin Color Skin color depends on: – the pigments carotene and melanin – Extent of blood circulation (red cells)  What are sources of pigment Melanin Carotene  What are sources of pigment Melanin – sunlight action on melanocytes Carotene – food (e.g. carrots)  The Dermis Located between epidermis and subcutaneous layer Anchors epidermal accessory structures – hair follicles, sweat glands Has 2 components: – outer papillary layer – deep reticular layer Characteristics – Strong, due to collagen fibers – Elastic, due to elastic fibers – Flexible (skin turgor)  The Papillary Layer Consists of areolar tissue Contains – capillaries, lymphatics and sensory neurons Has dermal papillae projecting between epidermal ridges  The Reticular Layer Consists of dense irregular connective tissue Contains – larger blood vessels, lymph vessels, and nerve fibres Contains collagen and elastic fibers Contains connective tissue proper Tissue is stronger in certain directions  Lines of Cleavage Lines of cleavage or tension lines Strength and alignment of fibres – a parallel cut remains shut, heals well – a cut across (right angle) pulls open and scars Figure 5–5  Accessory Structures Hair, hair follicles, sebaceous glands, sweat glands, and nails: – are derived from embryonic epidermis – are located in dermis – project through the skin surface Figure 5–15 Hair and Hair Follicles Figure 5–12  Exocrine Glands Sebaceous glands (oil glands): – holocrine glands – secrete sebum Sweat glands: – merocrine glands – watery secretions  Sebaceous Glands Sebum Contains lipids and other ingredients Lubricates and protects the epidermis Inhibits bacteria  Sweat Glands Merocrine (main type) – widely distributed on body surface – especially on palms and soles – sensible perspiration Cools skin Excretes water and electrolytes Flushes microorganisms and harmful chemicals from skin Thermoregulation: – is the main function of sensible perspiration – works with cardiovascular system – regulates body temperature  Other Integumentary Glands Apocrine sweat glands – found in armpits, around nipples, and groin – odorous secretions begin at puberty Pheremones? Mammary glands: – produce milk Ceruminous glands: – protect the eardrum – produce cerumen (earwax)  Repair of skin 1. Inflammatory 2. Migratory 3. Proliferation 4. Scarring  Summary Epidermis – is a multilayered, flexible, self-repairing barrier – prevents fluid loss – protects from UV radiation – produces vitamin D3 – resists abrasion, chemicals, and pathogens Dermis – provides mechanical strength, flexibility and protection – is highly vascularized – contains many types of sensory receptors Skin plays a major role in controlling body temperature: – acts as a radiator – removes heat from dermal circulation – works by evaporation of sensible perspiration