BIOL 2457 Module 3 - The Integumentary System PDF

Module 3: The Integumentary System BIOL 2457 Anatomy & Physiology I  Learning Objectives 1. List the major functions of the skin. 2. Identify the tissue types of the epidermis, papillary layer of the dermis, reticular layer of the dermis, an...

Module 3: The Integumentary System BIOL 2457 Anatomy & Physiology I  Learning Objectives 1. List the major functions of the skin. 2. Identify the tissue types of the epidermis, papillary layer of the dermis, reticular layer of the dermis, and the subcutaneous tissue. 3. List the 5 layers of the epidermis in order and describe their structural & functional differences. 4. Explain how thick skin is different from thin skin. 5. Describe the functions of each type of cell found in the epidermis. 6. Describe the factors that normally contribute to skin color and identify alterations. 7. Explain the anatomical basis for fingerprints. 8. Describe the structural & functional differences of the 2 layers of the dermis. 9. Describe the secondary structures of the skin: sensory structures, exocrine glands, hair, and nails. 10. Explain the short-term and long-term dangers of burns and how the degree of a burn (first-degree, second-degree, or third-degree) is determined. 11. Explain the significance of the Rule of Nines. 12. Relate the three types of skin cancer to the epithelial layers 13. Describe the process of tissue repair used by the body to heal superficial wounds  The Integument The integument (skin or is the barrier cutaneous membrane) between the internal & external environments It includes many accessory structures Major functions Barrier to environmental microbes Prevents water loss Thermoregulation Detecting sensations Vitamin D synthesis Excretion  Layers of the Skin The Epidermis: Keratinized stratified squamous epithelium The Dermis: The papillary layer of the dermis  Areolar loose connective tissue The reticular layer of the dermis  Dense irregular connective tissue The Subcutaneous Layer (hypodermis) Adipose loose connective tissue The Epidermis  The Epidermis The epidermis is the outermost layer of the skin The keratinocytes in the epidermis are arranged in strata (layers) Stratum corneum (Top Layer) Stratum lucidum* (Middle Layer in Thick Skin) Stratum granulosum (Middle Layer) Stratum spinosum (Middle Layer) Stratum basale (Bottom - Germ Layer)  Strata of the Epidermis Stratum basale is the deepest layer This layer is closest to the dermis, which means it is closest to the capillaries This layer includes keratinocytes doing mitosis This layer also include melanocytes (produces melanin) & Merkel cells (tactile cells) stimulates the Merkel disc (sensory nerve cell) Stratum spinosum The keratinocytes in this layer have spiny cell junctions Desmosomes strongly attach these cells to one another Langerhans cells & melanin granules are also in this layer Most abundant (thickest) layer of living cells  Strata of the Epidermis Stratum granulosum The dark spots in this layer are lamellar granules Function: prevents water loss from the skin Cells start to keratinize here Cells begin to die in upper region of this layer Stratum corneum This is the outermost layer of dead/non-living cells Increased keratinization provides protection against abrasion and microbes These cells are constantly being shed, generating replacement Stratum Lucidum Stratum lucidum (clear layer) is only seen in thick skin It is superficial to (closer to body surface) stratum granulosum It is deep to (farther away from body surface) stratum corneum Thick skin is present on the palms of the hands and the soles of the feet It does not have sebaceous (oil) glands and….. hair  Cells of the Epidermis Keratinocytes are the most abundant cell type Function: replenish epithelium and make keratin Mitosis happens in stratum basale Keratinocytes on the outer skin surface (corneum) are dead Langerhans cells are the “immune system” of the epidermis Function: phagocytize foreign substances These cells migrate to the epidermis from the red bone marrow  Cells of the Epidermis Melanocytes are the melanin-producing cells Darkens skin Function: protecting the skin from UV Radiation Melanin is stored in melanosomes which are transferred to keratinocytes Merkel cells are rare Function: detecting touch & proprioception (spatial position) Interacts with the Merkel disc in the underlaying dermis (a sensory nerve cell)  Skin Pigments Melanin is a reddish-yellow / brownish-black pigment It is made by melanocytes in the epidermis Everyone has the same number of melanocytes, but NOT the same amount of melanin Exposure to UV radiation stimulates the activity of melanocytes “Human skin pigmentation as an adaptation to UV radiation.” Jablonski and Chaplin, 2010.  Skin Pigments Carotene is a yellow / orange pigment obtained from plants Carotene is used to make Vitamin A (retinol) It can accumulate in stratum corneum Hemoglobin leads to red / pink color It is found in red blood cells of the dermis When melanin levels are low, hemoglobin’s color is more visible Blushing is due to vasodilation  Alterations to Skin Color Erythema: redness Bruising: changing color due to Albinism: melanocytes unable to due to increased Pallor: paleness due to decreased blood pooling blood under skin produce melanin blood Cyanosis: blueness due to Jaundice: yellowing due to Vitiligo: certain areas lose Addison’s Disease: bronze patches low oxygenated blood liver malfunction ability to produce melanin due to adrenal gland malfunction  The Dermis The dermis is the thickest layer of the skin The papillary layer (superficial); 20% made of loose areolar connective tissue The deep reticular layer (deep); 80% made of dense irregular connective tissue The dermis has blood vessels, nerves, lymphatic vessels, and other accessory structures  The Papillary Layer of the Dermis The papillary layer of the dermis is attached to the epidermis Dermal papillae are ridges with collagen fibers and nervous structures The pattern of these ridges determine a person’s fingerprint Fingerprints = “friction ridges” Fingerprints assist with grip & the sense of touch  The Reticular Layer of the Dermis The reticular layer of the dermis is made of dense irregular connective tissue  The Reticular Layer of the Dermis The collagen fiber proteins in the reticular arrange in: ◦ Cleavage lines , the natural orientation of the proteins ◦ Flexure lines , the way the proteins fold near joints  Secondary Structures Sensory Receptors: Different dermis sensory receptors detect different kinds of information The location of a receptor can be used to predict the kinds of information it collects  Secondary Structures Exocrine Glands: Eccrine sweat glands make watery sweat Function: thermoregulation These glands dump sweat onto the skin’s surface Apocrine glands make protein- & lipid-rich sweat Skin bacteria break this down, leading to body odor Function: reproductive signaling Contains pheromones Sebaceous glands make sebum (a type of oil) Function: lubricating and water-proofing hair & skin These glands dump their secretions onto hairs  Sebaceous Gland Malfunctions Whiteheads & blackheads are caused by blocked sebaceous glands Whiteheads exposed to air turn into blackheads Infected sebaceous glands make pimples (pustules / cysts / “zits”) This can be caused by a bacterial infection of the gland  Anatomy of Hair Hair is made of dead keratinized cells that grow out of the hair follicle Hair has many functions Detecting sensations (through hair nerve plexus) Protection against  heat loss & sunlight Eye protection  eyelashes & eyebrows Terminal hairs are long & coarse; vellus hairs are short & fine Hair nerve plexus  Fingernails Fingernails are an extension of the epidermis They contain harder dead keratin proteins than keratinocytes Fingernails grow from the nail matrix They are attached to the finger at the nail bed There are many capillaries under the nail bed, leading to the pink color of nails  Skin Cancer Skin cancer is the most common kind of cancer… one in five Americans will develop it Greatest risk factor: UV radiation exposure Basal cell carcinoma: most common, least dangerous, slow-growing, least malignant starts in stratum basale Squamous cell carcinoma: may spread (metastasize) starts in stratum spinosum Malignant melanoma: most deadly (most likely to metastasize) starts from melanocytes (usually in a mole)  Burns Burns are damage to the skin caused by heat, electricity, chemicals, or radiation Proteins in the tissue become denatured This leads to cell death Burns compromise the protective layer around the body Immediate problem: water loss  together with electrolytes & proteins Long-term problem: septicemia (systemic infection) & bacterial infection  Degrees of Burns First degree burn Second degree burn Third degree burn Only the epidermis is damaged Epidermis + reticular dermis are damaged All layers of the skin Redness, swelling, and pain Blisters appear is damaged (full thickness)  Treating Burns A 2nd degree burn of more than 30% of the body or a 3rd degree burn of more than 20% of the body is considered a critical situation Treatments Initially, replacing fluid & proteins is critical Next, preventing infection & sepsis is key Finally, skin grafts create a new skin barrier (necessary in 3rd degree burn)  The Rule of Nines The Rule of Nines is used to estimate the skin surface that has been burned Each area of the body = 9% Genital region = 1% The Rule of Nines is critical to predicting the tissue damage of a burn patient  Stages of Tissue Repair Inflammation  blood flow increases & leads to blood clots Granulation  fibroblasts fill the gap with collagen; macrophages “eat” the debris Regeneration  the edges of the gap fuse; thick epithelium forms Regenerated epithelium Scab Blood clot in Regenerating cut skin 1 epithelium Epidermis 2 Area of Vein granulation 3 tissue ingrowth Fibroblast Macrophage Budding Inflammatory Migrating Artery capillary chemicals white blood cell Fibrosed area 31  Stages of Tissue Repair 1. Inflammation 2. Granulation (scar tissue) 3. Wound Closure injured cells release granulation replaces clot and restores blood fibrosed area pulls closed proinflammatory chemicals flow ↑ blood flow and vessels ”leak” fibroblasts “stitch” tissue together with epithelium thickens  scab collagen fibers detaches blood clots forms  scabs epithelium regenerates underlying scar tissue remains macrophages clean up cellular debris Scab Regenerated epithelium Blood clot in Regenerating cut skin 1 epithelium Epidermis 2 Area of granulation Vein tissue 3 ingrowth Fibroblast Macrophage Budding Inflammatory Migrating Artery capillary chemicals white 32 blood cell Fibrosed area