Dermis - Module 3 PDF

DERMIS MODULE 3 Prepared by: MK SALAZAR-PASCUA DERMIS The dermis is an integrated system of fibrous, filamentous, and amorphous connective tissue. It comprises the bulk of the skin. It ranges from 0.2 mm (eyelids) to 4 mm (palms, soles) The dermis interacts with the epidermis in...

DERMIS MODULE 3 Prepared by: MK SALAZAR-PASCUA DERMIS The dermis is an integrated system of fibrous, filamentous, and amorphous connective tissue. It comprises the bulk of the skin. It ranges from 0.2 mm (eyelids) to 4 mm (palms, soles) The dermis interacts with the epidermis in maintaining the properties of both tissues. It is composed mainly of collagen DERMIS It is well supplied with blood vessels, sweat glands, sebaceous glands, and nerve endings It houses hair follicles and nail roots The dermis is the tissue of the facial skin to which skeletal muscles attach and cause facial expressions of emotion The dermis is also called corium DERMIS The dermis has a wavy, conspicuous boundary with the superficial epidermis ○ Dermal papillae - upward, finger-like extensions of dermis ○ Epidermal ridges - downward waves of epidermis ○ Friction ridges - Prominent waves on fingers (fingerprints) DERMIS The constituents of the dermis are mesodermal in origin except for nerves, which, like melanocytes, derive from the neural crest. ○ 0-6 weeks - precursors of fibroblasts. ○ 12 weeks - fibroblasts (reticulum and elastic fibers, collagen) ○ 24 weeks - vascular network, fat cells ○ Infant - small collagen bundles; numerous fibroblasts ○ Adult - thicker bundle of collagen  01 Functions of the Dermis Skin support Protection Thermoregulation Sensory  Functions of the Dermis 1 Skin Support It provides the skin pliability, elasticity, and tensile strength. ○ Collagen ○ Hyaluronic acid ○ Oxytalan fibers ○ Elastic tissue Functions of the Dermis 2 Protection It protects the body from mechanical injury. The blood vessels in the dermis are crucial for maintenance of the epidermis and epidermal appendages. Hosts an inflammatory response via recruitment of neutrophils, lymphocytes, and other inflammatory cells. Functions of the Dermis 3 Thermoregulation Vasoactive dermal vessels regulate body temperature Glomus bodies also take part in thermoregulation through AV shunt formation. ○ Glomus bodies are complexes of glomus cells, vessels, and smooth muscle cells that predominate in the digits, palms, and soles. Functions of the Dermis 4 Sensation Nerve endings in the dermis surround hair follicles. ○ These nerve endings sense hair movement and act as mechanoreceptors allowing sensation to extend beyond the skin's surface. Deep pressure receptors ○ Pacinian corpuscles - provide deep pressure and vibratory sensation. ○ Meissner's corpuscles - low-frequency stimuli  02 Layers of the Dermis Papillary Layer Reticular Layer Papillary Layer The superficial zone of dermis The dermal area that projects into the intervals between the epidermal ridges. Composed of loose connective tissue Thin zone of areolar tissue in and near the dermal papilla Papillary Layer The fiber components are thin and richly supplied with capillaries, sensory nerve endings and cytoplasm. It allows for mobility of leukocytes and other defense cells Rich in small blood vessels Reticular Layer The deeper and thicker layer of dermis Consists of dense, irregular connective tissue It comes into contact with the subcutaneous fatty tissue. It contains blood vessels and nerves in some parts.  03 Interstitial Components Collagen Elastin Fiber Reticular Fiber COLLAGEN COLLAGEN Collagen is the principal component of the dermis. It accounts for up to 70% of the weight of the dermis, primarily Type I collagen with some Type III collagen. It is found in tendons, ligaments, the lining of bones, and the dermis. It is a major stress-resistant material of the skin. Collagen fibers exist in a constant state of flux, being degraded by proteolytic enzymes called spare collagenases and replaced by new fibers. COLLAGEN Collagen fibers form from aggregations of thin fibrils. ○ Thin collagen fibers - papillary layer ○ Thick collagen fibers - reticular dermal upper layers Collagen fiber molecules are produced in the rough endoplasmic reticulum of fibroblasts. ELASTIC FIBERS ELASTIC FIBERS Elastic fibers are composed of elastin and fibrillin microfibrils ○ Elastin allows for gliding, stretching, and recoiling of fibers. The elastic fiber is thinner than collagen fibers. It is not as tough as the collagen fiber It is extremely elastic and found abundantly in the dermis of the scalp, face and the extensible organs such as arteries and tendons. ELASTIC FIBERS In the dermis, the deeper the elastic fiber, the thicker it is. In the reticular layers, elastic fibers are scattered among collagen bundles running parallel to the skin surface. Elastic fibers are also connected to the lamina densa of glands, sweat ducts, smooth muscle, nerves and blood vessels. The reticular dermis comprises thick elastic fibers. ELASTIC FIBERS Subtypes of Elastic Fibers 1. Elaunin fibers - horizontally arranged elastic fibers found near the junction of the papillary and reticular dermis. 1. Oxytalan fibers - are perpendicular elastic fibers found in the papillary dermis. RETICULAR FIBER RETICULAR FIBER Reticular fibers are composed of type III collagen. Unlike the thick and coarse collagenous fibers, reticular fibers form a thin reticular network. Such networks are widespread among different tissues and form supporting frameworks in the liver, lymphoid organs, capillary endothelia, and muscle fibers.  04 Cells of the Dermis Fibroblasts Macrophages Mast Cells Fibroblasts Fibroblasts are the primary cell type present in the dermis Responsible for the production and secretion of procollagen and elastic fibers. Procollagen is then catalyzed by enzymes to form collagen, which is finally cross- linked to create strong parallel layers. Histiocytes Histiocytes are tissue macrophages present within the connective tissue that assist the immune system. It intermingles with fibroblasts on the outside of endocapillary cells. Histiocytes contain a nucleus, Golgi apparatus, smooth and rough endoplasmic reticuli, and lysosomes. It is involved in organ repair Mast Cells Mast cells are inflammatory cells located in the perivascular areas of the dermis. Secrete vasoactive and proinflammatory mediators important in inflammatory reactions, collagen remodeling, and wound healing Contain granules with histamine and other chemicals, which are released from the cell if it is disturbed or damaged Schwann Cells Specialized cutaneous Schwann cells initiate pain sensation Dermal Adipocytes Dermal adipocytes are a distinct cell population from the subcutaneous adipose tissue. Dermal adipocytes not only provide insulation and energy storage but also assist in hair follicle regeneration and wound healing. 05 VASCULATURE Vasculature 1. Subcutaneous/deep dermal - composed of arteries and veins that branch superficially into the middermis to form the cutaneous plexus. - Largest blood supply Vasculature 2. Cutaneous Plexus - responsible for supplying blood to the adnexal structures of the dermis, including follicles and glands - Branches superficially to form a fine network of capillaries and venules called the papillary plexus Vasculature 3. Papillary Plexus - supplies blood to the epidermis Vasculature The skin blood flow is adjusted to keep the deep-body temperature at 37 degrees Blood flow to the skin is dynamic, and factors such as environmental temperature, systemic disease and/or localized inflammation can readily induce shunting of blood to or from the skin.  06 Nerves of the Dermis Free-Nerve endings Meissner’s Corpuscles Pacinian Corpuscles Hair Nerve Endings Free-Nerve Endings Most abundant type of sensory endings Occurs widely in the integument and within muscles, joints, viscera, and other structures. Act primarily as pain receptors, although some sense temperature, touch, and muscles. Merkel disc - dermal-epidermal junction - light-touch receptors Meissner’s Corpuscles These are light-touch mechanoreceptors lie within the dermal papillae. They’re small, egg-shaped capsules of connective tissue surrounding a spiraled-end of a dendrite. Most abundant in sensitive skin areas such as the lips and fingertips These corpuscles can sense a quick touch but not a sustained one. Pacinian Corpuscles These are deep-pressure mechanoreceptors dendrites surrounded by concentric layers of connective tissue. Found deep within the dermis and hypodermis, they respond to deep or firm pressure and vibrations. Each is more than 2 mm long and therefore visible to the naked eye. Hair Nerve Endings These mechanoreceptors respond to a change in position of a hair. They consist of bare dendrites. The sensory nerve enters the hair follicle, wrapping around the hair bulb. When the hair is moved, the hair stimulates the nerve endings, creating sensation. End-Bulbs of Krause Also known as Krause’s corpuscles Respond to continuous pressures. Thermoreceptors sensitive to cold and activated by temperatures below 20 degrees Celsius. They are commonly found throughout the body in the dermis as well as in the lips, the tongue, and the conjunctiva of the eyes Brushes of Ruffini Also known as Ruffini cylinders, Ruffini’s corpuscles, or bulbous corpuscles, These branch out parallel to the skin and detect tension deep in the skin. Thus, they are sensitive to pressure, stretching, and distortion of the skin. Found primarily in the dermis and subcutaneous tissue, they’re dendrite endings enclosed in a flattened capsule  07 Diseases Free-Nerve endings Meissner’s Corpuscles Pacinian Corpuscles Hair Nerve Endings Collagen-Related Ehlers-Danlos syndrome A group of genetic connective tissue disorders caused by various mutations in collagen Defective collagen synthesis. skin hyperextensibility Joint mobility tissue fragility Collagen-Related Osteogenesis imperfecta A genetic disorder of type I collagen causing decreased dermal collagen and impaired skin elasticity. Bones fracture (break) easily, often with no obvious cause or minimal injury. Brittle bone disease Collagen-Related Striae distensae Stretch marks A type of scar that develops when our skin stretches or shrinks quickly. Collagen and elastin rupture. Marfan syndrome Cushing's syndrome Chronic glucocorticoid use Pregnancy Fibroblast-Related Myofibroblasts, expressing alpha- smooth muscle actin (a-SMA), have been implicated in both hypertrophic scars and keloids. Hypertrophic scars raised, erythematous, pruritic lesions that do not extend beyond the boundaries of the original wound Keloids benign growths of fibrous tissue that grow beyond wound boundaries. Fibroblast-Related Lichen sclerosus An inflammatory disorder involving abnormal fibroblast function in the papillary dermis, causing fibrosis of the superficial dermis and epidermis. A rare skin disease that causes itchy and painful patches of thin, white, wrinkled-looking skin. Can lead to scarring and tightening of the skin around the genitals and anus. Fibroblast-Related Acanthosis nigricans Results from increased growth factor receptor signaling causing proliferation of epidermal keratinocytes and dermal fibroblasts, leading to hyperkeratosis and papillomatosis ("peaks and valleys") Velvety, darkening of the skin that usually occurs in intertriginous areas. Usually occurs in skin fold areas, such as the back of the neck, axilla, and groin, and may include thickening of the skin Mast Cell-Related Mastocytosis A spectrum of rare diseases involving an increase in mast cells within the skin and other organs. Urticaria pigmentosa Most common mastocytosis A rash that appears most often in children and young adults Reddish-brown lesions that may form hives or blisters when stroked. HYPODERMIS  HYPODERMIS Also called the subcutaneous layer or superficial fascia The layer directly below the dermis Connects the skin to the underlying fascia (fibrous tissue) of the bones and muscles. It consists of well-vascularized, loose, areolar connective tissue and adipose tissue, which functions as a mode of fat storage and provides insulation and cushioning for the integument.  HYPODERMIS The panniculus varies in thickness depending on the skin site. It is considered an endocrine organ because it provides the body with buoyancy and functions as a storehouse of energy. Hormone conversion ○ androstenedione -> estrone (by aromatase) ○ Lipocytes produce leptin, which regulates body weight Thanks!