Integumentary System Notes PDF

Integumentary System PN 1109 Objective 4 Chapter 5 Learner Outcomes • Define key terms related to the integumentary system • Identify the primary functions of the skin • Discuss the structure and functions of the two main layers of the skin • Identify the main appendages of the skin and their loc...

Integumentary System PN 1109 Objective 4 Chapter 5 Learner Outcomes • Define key terms related to the integumentary system • Identify the primary functions of the skin • Discuss the structure and functions of the two main layers of the skin • Identify the main appendages of the skin and their location • Discuss the structure and function of the sudoriferous glands • Discuss the structure and function of the sebaceous glands • Discuss the structure and functions of the hair • Discuss the structure and functions of the nails • Discuss the functions of the receptors Integumentary System Largest organ in the body Made up of the skin and accessory organs (glands, hair, nails) Our contact with the external environment Protection from the outside environment (keeps the inside and outside separate) • Resilient and versatile • Repairs quickly • Integument = “covering” • • • • Structure of the Skin • AKA cutaneous membrane • Has two distinct layers • epidermis - superficial • Dermis – underlies epidermis; mostly fibrous connective tissue • Anchored to underlying structures by the subcutaneous tissue aka hypodermis • Deep to skin • Not part of skin but shares some functions • Mostly adipose tissue that absorbs shock and insulates Epidermis • • • • • • Outer layer Keratinized stratified squamous epithelium Avascular Cells receive their nutrients from underlying tissues via diffusion In thick skin (palms and soles) it has 5 distinct regions Rest of the body only has 4 regions or strata Epidermis 4 cell types: • Keratinocytes: • produces keratin • most abundant cell in epidermis; • continuously grow and shed • Melanocytes: • produce melanin which is a pigment that protects the nucleus of keratinocyte cells from UV light by forming a shield • Dendritic cells: • come from bone marrow (macrophages) • aka Langerhans cells; • ingest foreign substances • Tactile cells: • aka Merkel cells • linked to a nerve ending; • used as a sensory receptor for touch Epidermis • 4 or 5 distinct layers • thick skin- 5 layers • Thin- 4 layers • Acronym: “Come Let’s Get Sun Burned” (Top to bottom) • Layers: • • • • • • Corneum Lucidium Granulosum Spinosum Basale See p. 153-154 Epidermis Layers: Stratum Corneum • Horny layer • Outermost surface • ¾ of epidermal thickness • 20-30 layers of flattened, dead, keratinized cells • Usually shed and replaced (process takes about 5 weeks) • Functions: • Protect deeper cells from environment and water loss • Protect from abrasion and penetration • Barrier against biological, chemical, and physical assaults Epidermis Layers: Stratum Lucidum • • • • Clear layer thin, translucent band above the s. granulosum Few layers of flattened, anucleate cells Present only in thick skin (palms, soles of the feet) Epidermis Layers: Stratum granulosum • • • • Very thin region, 2 or 3 layers of flattened cells Keratinization begins in this layer Cells appear granular hence the name Cells above this layer die • Too far from dermal capillaries Epidermis Layers: Stratum spinosum • Prickly layer • Cells contain web-like system of filaments attached to desmosomes • Consists of several layers of cells • Abundant melanosomes and dendritic cells Epidermis Layers: Stratum basale • • • • • Bottom layer closest to basement membrane Aka: stratum germinativum Firmly attached to the dermis Closest to the blood supply Actively mitotic • News cells continually produced • As cells move toward surface they die Epidermis • Due to the avascular component and layout, cells close to the basement membrane receive adequate nutrients and are actively growing and dividing • They push upward toward the surface where they take on a flatter or squamous shape • Once they are far enough away from the basement membrane where nutrients will be lacking, they slough off and die • As they are being pushed away from the basement membrane they undergo a process called keratinization Epidermis • Keratinization • When a protein called keratin is deposited into the cell • Changes the chemical component and shape of the cell • They take on different appearances and characteristics to form distinct regions or strata Dermis • Strong flexible connective tissue • Deeper and thicker than epidermis • • • • • • Contains fibroblasts, macrophages, and sometimes mast cells Hair, nails and some glands are embedded in dermis Contain collagenous and elastic fibers (useful for strength and elasticity) Contains blood and lymphatic vessels and nerves (vascular and innervated) Contains sensory receptors Contains two distinct layers • Papillary • Reticular Dermis Layers: Papillary • areolar connective tissue with collagen and elastic fibers and blood vessels • Loose tissues • Phagocytes can patrol for microorganisms • dermal papillae • Superficial peg-like projections • contain blood vessels, nerve endings and sensory receptors • On thick skin such as the palms, fingertips and soles papillae form ridges that provide friction for grasping and fingerprints; friction ridges Dermis Layers: Reticular • Deeper and thicker than papillary layer • Made up of course, dense fibrous connective tissue • Elastic fibers – stretch and recoil • Collagen fibers – strength and resiliency • Contain separations or less dense regions between bundles aka cleavage (tension) lines (see fig 5.4); important with surgeons; externally invisible • Collagen fibers give skin strength and resiliency • Flexure lines are dermal folds that occur at or near joints; visible on hands, wrists, fingers, soles, toes Dermal Layer Skin Tone • Determined by melanin, carotene, and hemoglobin • Melanin: • • • • Only pigment made in skin reddish yellow to brownish black all humans have same number production depends on environmental factors freckles and nevi are local accumulations of melanin • Carotene: • yellow to orange pigment • most obvious in palms and soles • From food • Hemoglobin: • pinkish-red • From oxygen carried in blood Skin Color Alterations • Cyanosis • Blue – low oxygenation of hemoglobin • Erythema • redness – fever, hypertension, inflammation, allergy • Pallor • blanching; anemia, low BP, fear, anger • Jaundice • Yellow; liver disorder Skin Appendages • Integumentary system contains accessory organs such as hair and hair follicles, nails, sweat & sebaceous glands Hair • Found on nearly all body surfaces • Contains a shaft and root • Shaft extends beyond the skin’s surface; part you can see; has no nerves • Root is the portion below the skin’s surface; can’t see; surrounded by hair follicle • Functions: • Heat loss • Physical trauma • sunlight Skin Appendages Hair Follicles • Extend from epidermal surface to dermis • Hair bulb is contained in the • • • • dermal layer a Hair follicle receptor (root hair plexus) Sensory nerve endings – touch receptors Hair matrix: actively dividing area • Arrector pili • smooth muscle attached to follicle that allow for the hair to move (goose bumps) • Hair papilla • Dermal tissue – blood supply Skin Appendages Types & Growth of Hair • Vellus • faint and fine; found on children and adult females • Terminal • thicker, coarser hair found on scalp/pubic area • Nutrition and hormones affect hair growth • Lose 90 scalps hairs daily Skin Appendages Skin Appendages Nails • Scale-like modifications of epidermis • cover the distal, dorsal surfaces of fingers and toes • Contain hard keratin • Nail matrix Skin Appendages - Glands Sweat Glands (sudoriferous) • All skin surfaces except nipples and parts of external genitalia • ~ 3 million per person • 2 main types: • Eccrine (merocrine) • Apocrine Skin Appendages (1) Eccrine or merocrine • • • • • more numerous; Abundant on palms, soles and forehead Ducts connect to sweat pore; secretion is sweat (99% water) Function in thermoregulation • Regulated by sympathetic nervous system (2) Apocrine • • • • found only on the axillae and external genitalia Larger than eccrine glands Ducts empty into hair follicles secretion is milky/yellowy & odorless • • when broken down by bacteria create body odor; release product via hair follicles Begin functioning at puberty Skin Appendages – Glands Modified Apocrine Sweat Glands: • Ceruminous glands: • lining of the external ear canal • secrete cerumen (wax) • Mammary glands: secrete milk Skin Appendages - Glands Sebaceous (Oil) Glands • aka holocrine glands • Widely distributed (not in thick skin) • Most are associated with hair follicles • Secrete an oily substance sebum • which keeps skin and hair soft and pliable • bactericidal • Stimulated by sex hormones at puberty Primary Functions of the Skin • • • • • • Protection Regulation of temperature Sensory Perception Production of Vitamin D Blood reservoir Excretion of wastes Primary Skin Functions: Protection • The keratin protein in cells waterproofs the skin and helps prevent fluid loss • Also prevents too much water entering the skin • Intact skin provides the first layer of protection against bacteria and potential invading organisms • The sebaceous glands secrete oils that inhibit bacterial growth; pH remains low to ward of bacteria • Melanin, a pigment found in skin, absorbs light and helps protect underlying tissues from damaging effects of UV light • Protects against underlying tissues from mechanical, chemical and thermal injury Primary Skin Functions: Thermoregulation • Important to maintain as changes in body temperature can alter chemical reactions in the body • Two ways skin help maintain body temperature: • 1. Dilation and constriction of blood vessels • 2. Activity or inactivity of the sweat glands • Adipose tissue in the subcutaneous layer also acts in thermoregulation by offering heat insulation Primary Skin Functions: Sensory Reception • Cutaneous sensory receptors; exteroceptors (respond to stimuli on the outside off the body) • Dermis • contains sensory receptors for heat, cold, pain, touch and pressure • Receptors in the dermis relay messages to the brain regarding changes in the environment • These messages allow the brain to take the necessary precautions to prevent or minimize injury • Means of communication between individuals Primary Skin Functions: Synthesis of Vitamin D • Needed in order for the body to absorb calcium and phosphorus; needed in muscle function and bone metabolism • When the skin is exposed to UV rays a cholesterol molecule found within in the skin will stimulate the production of vitamin D (Synthesis) Primary Skin Functions: Blood Reservoir • Dermal supply is highly vascular • Can hold 5% of the blood supply • Useful when body needs blood elsewhere; vessels constrict to shunt blood to vital areas Primary Skin Functions: Excretion of Wastes • Via pores in your skin; salt and water loss • Defense mechanism • Helps body to maintain homeostasis in extreme cases; diabetic ketoacidosis