Integumentary System - Notes (PDF)

Y1B4M1L3 MUSCULOSKELETAL / INTEGUMENTARY SYSTEMS LECTURER DR. GRACE PEREZ OCTOBER 18, 2023 | 8 00 - 10 00 AM THE INTEGUMENTARY SYSTEM TABLE OF CONTENTS I. Integumentary System A. Layers of the Skin B. Glands C. Nail D. Hair II. Natural Skin Creases A. Visible Skin Lines B. Wrinkle Lines C. Contour...

Y1B4M1L3 MUSCULOSKELETAL / INTEGUMENTARY SYSTEMS LECTURER DR. GRACE PEREZ OCTOBER 18, 2023 | 8 00 - 10 00 AM THE INTEGUMENTARY SYSTEM TABLE OF CONTENTS I. Integumentary System A. Layers of the Skin B. Glands C. Nail D. Hair II. Natural Skin Creases A. Visible Skin Lines B. Wrinkle Lines C. Contour Lines D. Flexure/Joint Lines E. Relaxed Skin Tension Lines F. Lines of Langer G. Kraisslʼs Lines H. Blaschkoʼs Line III. Skin Conditions A. Acne Vulgaris B. Pigmenatry Demarcation Lines C. Periorbital Pigmentation D. Melanocytic Nevus E. Melanoma F. Vitiligo G. Albinism H. Striae Distensae IV. Aging V. Review Questions A. LAYERS OF THE SKIN ● Epidermis - outermost layer of the skin ○ Stratum Corneum ○ Stratum Lucidum ○ Stratum Granulosum ○ Stratum Spinosum ○ Stratum Basale/Germinativum ● Dermis - contains blood vessels (nerves, involuntary muscles, sweat glands, oil glands, hair follicles, and papillae) ● Hypodermis I. INTEGUMENTARY SYSTEM ● 15% of total body weight ● 3 Major Parts: ○ Skin – derm/o, derm/a, dermat/o → Membrane - covers the body → Organ - contains a variety of essential tissues ○ Hair – trich/o, trich ○ Nails – kerat, kerat/o ● Functions: ○ Protection – acts as a barrier to the sunʼs ultraviolet rays and to the invasion of pathogens or germs ○ Sensory Perception – the body is able to respond to pain, pressure, temperature as well as touch sensations ○ Body Temperature Regulation – performed by the blood vessels and the sudoriferous glands ○ Storage – the skin stores fat, glucose (sugar), water, vitamins, and salts; adipose (fatty) tissue is stored in the subcutaneous fascia as a source of energy ○ Absorption – semipermeable; substances both beneficial and not so can penetrate through and into the body ○ Excretion – skin can also eliminate substances such as excess water, salt, and a minute amount of waste/toxins ○ Production – the skin is responsible for the production of vitamin D by synthesizing the rays of the sun with skin compounds; vitamin D is an essential nutrient for the wellbeing and functioning of the body ○ Pigmentation – normal skin colors (skin, hair, & retina of the eye) → Melanin – a brownish-black color pigment; determines the color of the skin; the more melanin produced, the darker the skin is; responsible for freckles in smaller concentrations → Melanocytes – specialized cells in the epidermis, melanocytes, that produce melanin → Carotene – a yellowish-red pigment which also helps to determine skin color → Albino – the lack of color pigmentation in the skin; lack the ability to produce melanin; skin color is white or yellowish, albino eyes also lack pigmentation (dark pink or red) and are very sensitive to sunlight Figure 1. Layers of the Skin EPIDERMIS ● Outermost layer ● Further divided into 5 6 thinner layers which do not have blood vessels ● Stem cells → transit amplifying cells → terminal differentiation → shed off ● Normal epidermal turnover time = 52 75 days → Pathology causes faster turnover which leads to desquamation of cells in upper layers (e.g. psoriasis) ■ Psoriasis ⎻ Fast turnover 8 days) ⎻ Very thick corneum ⎻ Blood vessels seen (lesions) EPIDERMAL DIFFERENTIATION ● Intermediate filament family → Keratins → Assemble to polymers → Desmosomes - cell to cell junction o All cells o Makeup changes 1. Desmoglein 3 (basal) 2. Plakophilin 2 (basal) 3. Desmoglein 1 (differentiated) 4. Plakophilin 1 (differentiated) → Hemidesmosomes - cell to stratum junction ABALO, ALANTUSON, ATENOR, BARSANALINA, DEDAL, DELFIN, LEE, LICAYAN, SALISE, TORNALEJO | MG 3 1 of 10 Y1B4M1L3 THE INTEGUMENTARY SYSTEM ● Structural markers: → Loricrin and filaggrin - granular and upper spinous → Keratins 1 and 10 - differentiated cell layers (spinous) → Keratins 5 and 14 STRATUM CORNEUM ● Uppermost layer ● Dead skin cells ● No nuclei STRATUM LUCIDUM ● Nuclei begin to disintegrate ● Filled with Eleidin protein which is eventually transformed into Keratin STRATUM BASALE GERMINATIVUM ● Lowest layer (in contact with the dermis below) ● Where cell division/mitosis takes place and new epidermal tissue is formed ● Tight junctions and keratohyalin granules ○ Keratohyalin – modify to filaggrin at corneum ● Mark granular cells ○ Melanocytes ○ Langerhans cells ○ Merkel cells ● Basal keratinocytes – columnar/cuboidal ● Corneum loss = basal growth ● Desquamation ● Peeling/flaking ● Normally imperceptible unless with excess Figure 2. Melanin synthesis. The color will depend on the presence of cysteine. Note: TYR = tyrosinase). FITZPATRICK SKIN PROTOTYPE SCALE ● ● ● ● ● Baseline pigmentations Sensitivity to sun burning Ability to tan Asians – typically Type IV and V Caucasians - typically Type I to III MELANOCYTES ● Melanin pigment producing cells derived from the neural crest ● Produces 3 kinds of melanin ○ Pheomelanin – red to yellow; one kind is produced ○ Eumelanin – brown-black; two kinds are produced → DHICA melanin - light brown pigments → DHI-melanin - dark brown pigments ● Supplies melanin to 35 40 basal keratinocytes ● Racial variation (pigmentation) – based melanocyte morphology and activity, not on the number and distribution ● Melanosomes in light skinned individuals degrade more rapidly than in dark-skinned MELANIN ● Protects the skin against harmful effects of UV radiation on DNA ● Scavenger of the damaging free radicals ○ Constitutive pigmentation – intrinsic level; genetically determined ○ Facultative pigmentation – reversible changes induced by environmental agent such as UV radiation and hormones → Immediate tanning – occur within minutes as a result of photo-oxidation of pre-existing melanin → Delayed tanning – occurs after 48 hrs; stimulation of melanogenesis within the melanocytes and transfer of additional melanosome to keratinocytes Figure 3. Fitzpatrick Skin Prototype Scale LANGERHANS CELLS ● Dendritic antigen - presenting cells ● Birbeck granule – discoid or cup-shaped that resembles the head of a tennis racket ○ The structural hallmark of langerhan cells ● Migrate out of the epidermis to lymphoid tissues when stimulated by antigens ● Increased levels in chronic inflammatory disorders MERKEL CELLS ● Function as neuroendocrine sensory receptors ● Connected to keratinocytes by desmosomes ● Slowly adapting mechanoreceptors that respond to directional deformations of the epidermis and direction of the hair movement by releasing a transmitter from dense-core cytoplasmic granules ○ Loricrin and filaggrin ABALO, ALANTUSON, ATENOR, BARSANALINA, DEDAL, DELFIN, LEE, LICAYAN, SALISE, TORNALEJO | MG 3 2 of 10 Y1B4M1L3 THE INTEGUMENTARY SYSTEM EPIDERMAL LIPID LAYER ● Serves as an important barrier to transepidermal water loss and other substances through the body surfaces ● Lipids are synthesized in the epidermis that includes triglycerides, fatty acids, phospholipids, cholesterol, cholesterol esters, glycosphingolipids, and ceramides ● 7-dehydrocholesterol - also synthesized in the skin; a precursor of Vitamin D DERMIS ● Contains major structures and functions for the skin within a framework of elastic connective tissue ● Contained within the dermis (corium) → Blood vessels ○ Nerves ○ Involuntary muscles ○ Sweat glands → Oil glands ○ Hair follicles → Papillae ● Blood vessels – via the capillaries, nutrients are provided to the skin and waste products are taken away; play a major part in maintaining and sustaining the bodyʼs temperature; the vessels dilate (to make larger) to release heat or they constrict (to make smaller) in order to retain the bodyʼs heat ● Nerves – allow the skin to have sensory perception: pain, pressure, temperature, touch ● Involuntary muscles in the dermis – by dilating, or opening the pores in the skin, the body is able to cool off and allow sweat to exit; these muscles allow the pores on the skin to contract or constrict in order to keep the heat from exiting the body ● Goosebumps – these structures are important for keeping and maintaining the bodyʼs temperature which averages at 98.6 fahrenheit 37C ● Homeostasis – a major process by which the body works to keep all of its structures and functions in balance ● The top of the dermis is covered with papillae, which fits into the ridges right below the stratum germinativum; fingerprints ● Type III collagen ○ 15 20% ○ Finer type ○ Papillary dermis and blood vessels ● Type IV collagen ○ Basal lamina between the epidermis and dermis ○ Located around Schwann cells of peripheral nerves and endothelial cells of vessels ● Minor types: 5, 6, 7 ● Elastic fibers ○ Fibrous network interwoven between the collagen bundles throughout the dermis ● Papillary function ○ Mechanical anchorage ○ Metabolic support ○ Trophic maintenance to epidermis ○ Supply sensory nerve endings and blood vessels ○ Linked to basal keratinocytes (superficial) – interdigitate ○ Dermal-epidermal junctions ● Reticular layer ○ Deformable lattice (elastic fibers) ○ Thicker collagen bundles ○ Parallel orientation (collagen fibers) → Mechanical forces → Development of skin line Figure 5. Layers of the Dermis HYPODERMIS Subcutaneous fascia Hypo- below the dermis It is made of elastic and fibrous connective tissue and adipose Layer of loose connective tissue of variable thickness that merges with the reticular dermis ● Mediates the mobility of the skin ● Adipose component contributes to the thermal insulation, shock absorber and store of metabolic energy ● Subcutaneous fat varies according to: ○ Gender (thicker in females) ○ Age (thicker in middle aged) ○ Geographic location of the person (thicker in colder) ○ Location in the body → Lower abdominal wall (distinct) → Limbs and perineum (differentiated) → External ears (almost absent) → Scalp, palms, and soles (atypical) ● ● ● ● Figure 4. Structures of the Dermis LAYERS OF THE DERMIS ● Dense connective tissue composed of an interwoven collagenous and elastic network in an amorphous ground substance of glycosaminoglycans , glycoproteins and bound water ● Type I collagen ○ 80 85% ○ Coarse ○ Deeper reticular dermis ABALO, ALANTUSON, ATENOR, BARSANALINA, DEDAL, DELFIN, LEE, LICAYAN, SALISE, TORNALEJO | MG 3 3 of 10 Y1B4M1L3 THE INTEGUMENTARY SYSTEM ● Why does it hurt when you pull a hair out of the scalp? ○ At the base of the hair follicle are sensory nerve fibers that wrap around each hair bulb INNERVATION OF THE SKIN ● Major sensory organ ● Pacinian corpuscle ○ Subserve deep pressure and vibrational sensation ○ Located deep in the dermis or in the hypodermis ● Meissnerʼs corpuscle ○ Highly specialized mechanoreceptors ○ Responsible for sensing light touch ○ Found in hairy and glabrous skin ○ Located in the dermal papillae close to the dermal-epidermal junction ● Primary input is transmitted by neurons whose cell bodies lie in the spinal and cranial ganglia ● Myelinated and unmyelinated axons are terminally distributed within the dermis ● Segmental arrangement of the spinal nerves is ● reflected in the sensory supply of the skin ● Dermatome - area supplied by all cutaneous branches of an individual spinal nerve through its dorsal and ventral rami VASCULAR SUPPLY AND LYMPHATIC DRAINAGE ● 3 main sources: ○ Direct cutaneous system → Derived from the main arterial trunks and accompanying veins → Vessels course in the subcutaneous fat parallel to the skin surface ○ Musculocutaneous system → Arise from the intramuscular vasculature → Pass through the surface of the muscle and pierce the deep fascia to reach the skin by spreading out in the subcutaneous tissue ○ Fasciocutaneous system → Consists of perforating branches from deeply located vessels that pass along intermuscular septa and then fan out at the level of the deep fascia to reach the skin ● Lymphatics ○ Small terminal vessels that collect interstitial fluid and macromolecules for return to the circulation via larger vessels ○ Convey lymphocytes, Langerhans cells and macrophages to regional lymph nodes ○ Blind-ended, endothelial-lined tubes or loops just below the papillary dermis ○ Drains into superficial plexus below the subpapillary venous plexus ○ Drain via collecting vessels into a deeper plexus at the junction of the reticular dermis and subcutis B. GLANDS SWEAT GLANDS ● Sudoriferous glands ● Coiled tubes that extend through the dermis and open on the surface of the skin and pores ● Release sweat via exocytosis (contents transfer from inside the cell to outside the cell) ● Merocrine secretion type – the cell remains unharmed and intact during the secretion process ● ● ● ● Total number is approximately 1.6 4.5 M Greatest on the plantar skin of the feet More sweat glands for indigenous people in warmer climates Sweat contains: ○ Clear, odorless fluid, hypotonic to tissue fluid ○ Contains mainly sodium and chloride ions ○ Potassium, bicarbonate, calcium, urea, lactate, amino acids, immunoglobulins, and other proteins ○ Secrete 10 L per day ○ Others: → Water → Salt → Body waste ECCRINE GLANDS Found almost everywhere on the body Concentrated on palms, soles, head Secrete watery substance via a pore on skin Tubular, coiled appearance Secrete: ○ Water – 99% ○ Salt – 1% ○ Waste ○ Compounds that inhibit growth of pathogens ● Become functional soon after birth ● Function to cool the skin ● Eccrine = Everywhere on skin (almost) ● ● ● ● ● APOCRINE GLANDS Found in armpits, anal, and genital region Secrete a milky substance rich in protein Stink after bacterial consumption Unlike eccrine glands, apocrine glands open into hair follicles These glands become active during puberty Initially sterile secretion Undergoes bacterial decomposition to generate odorous and musky compounds including short-chain fatty acids and 5 alpha androstenone ● Potent pheromones in animals ● Apocrine = Armpits, Anal, and Anogenital region ● ● ● ● ● ● ● MODIFIED SWEAT GLANDS ● Special types of modified apocrine glands ● Ceruminous Glands ○ Found in ear ○ Work with oil glands to create cerumen (earwax) ○ Cerumen lubricates external ear canal, waterproofs, and protects against pathogens/debris ● Ciliary Glands ○ Found along eyelid ○ Work with oil glands to keep eyelashes flexible ● Mammary Glands ○ Specialized glands that secrete milk ○ Mammary means “breast” ○ Typically become functional in females during/after pregnancy, but also present in males OIL GLANDS ● Sebaceous glands ● Usually open into hair follicles ● Produces sebum, an oily substance ○ Contributes to characteristic body odor ABALO, ALANTUSON, ATENOR, BARSANALINA, DEDAL, DELFIN, LEE, LICAYAN, SALISE, TORNALEJO | MG 3 4 of 10 Y1B4M1L3 THE INTEGUMENTARY SYSTEM ● ● ● ● ● ● ● ● ○ Mixture of 50% di- and triglycerides, wax esters, squalene, cholesterol esters and free fatty acids ○ Large at birth then regress until stimulated during puberty by androgens ○ Sebum keeps the skin and hair from becoming dry; lubricates skin and hair; helps skin retain water ○ However, due to genetics some peopleʼs hair is more dry than others ○ The dryness is determined by whether or not the hair is curly ○ A hair follicle anchors each hair into the skin—deep into the dermis ○ The hair bulb forms the base of the hair follicle ○ In the hair bulb, living cells divide and grow to build the hair shaft ○ The hair shaft is the hair that projects from the skin or scalp Absent on palms, soles; common on face/scalp Made of acini cells that secrete sebum Cells fill with sebum then rupture Contents are released into hair follicle Holocrine secretion – cells are damaged as they fill and rupture and release their contents Become active during puberty Commonly attach to hair follicles Also found in areas with no hair Figure 6b. Nail structure ● Finger nails ○ Grow about 3 mm per month ○ 6 months from root to free edge ● Toe nails ○ Grow about 1 mm per month ○ 12 to 18 months from root to free edge ● Both grow faster in the summer - during increased circulation, possibly due to increased exposure to sun C. NAIL ● Main function: serve the fingers and toes as protective plates and enhance the sensation of the fingertip or toe tip ● Help prevent bone damage – dig, itch, grasp ● Like the hair, the nail is also composed of keratin ● Keratinization ○ Elimination of nucleus and organelles → process continues ○ Fill with keratin protein ● The nail is made up of dead epithelial cells packed tightly together to form a translucent, thick dense surface of keratin ● The nail is formed in the nail bed ● If you slam your finger in the door you may lose your nail, but it will regrow ● If you damage the nail bed, that nail will never come back Figure 7. Keratinization process NAIL STRUCTURE ● ● ● ● ● ● ● ● Free edge – whitish Nail body – pinkish (blood) Lunula – crescent Cuticle/eponychium – extends into the skin Nail root Nail bed – living cells Nail matrix – growing area; cell division (mitosis) Hyponychium – beneath lunula and root; free edge hangs over D. HAIR Main function is to protect the skin Composed of a strong structural protein called keratin Grows within a hollow tube called the follicle Filamentous cornified structures present over almost the entire body surface ● Play a role as socio-sexual communication ● Assist in thermoregulation and protection ● Sensory function ● ● ● ● HAIR STRUCTURE ● ● ● ● ● Figure 6a. Nail structure Hair shaft – extends out from surface to skin Hair root – extends from bulb to surface Hair bulb – extends from root to deeper dermal layer Hair follicle – sac or tube surrounds hair root; extends into the dermis ○ Dermal root sheath ○ External epithelial root sheath → Internal epithelial root sheath ABALO, ALANTUSON, ATENOR, BARSANALINA, DEDAL, DELFIN, LEE, LICAYAN, SALISE, TORNALEJO | MG 3 5 of 10