Chapter 4 Opener
Introduction The integumentary system is composed of: Skin Hair Nails Sweat glands Oil glands Mammary glands The skin is the most visible organ of the body Clinicians can tell a lot about the overall health of the body by examining the skin
Figure 4.1 Functional Organization of the Integumentary System
Function of the integument includes: Physical protection Regulation of body temperature Excretion (secretion) Nutrition (synthesis) i.e. vitamin D3 Sensation Immune defense
Integumentary Structure and Function Cutaneous membrane (skin) are subdivided into: Epidermis is the keratinized (hardened) stratified squamous epithelium Dermis is the underlying loose connective tissue 2 layers: Papillary layer & Reticular layer Hypodermis (subcutaneous) lies deep into the dermis Accessory structures Hair & eyelashes Exocrine glands (sweat & oil) Nails
Figure 4.2 Components of the Integumentary System No blood vessels (avascular) or nerves in the epidermis
The Epidermis Four cell types can be found in the epidermis: Keratinocytes are the most abundant cells in the epidermis secrete waterproofing protein to protect body surface from dehydration Form different cell layers (four in thin skin, five in thick) Melanocytes are pigment cells found deep in the epidermis make brown pigment around the nucleus to protect DNA from UV damage Merkel cells are sensory cells detect small changes in pressure on surface of skin Langerhans cells are fixed macrophages Fight infectious problems in skin
Layers of the Epidermis (from bottom to top) Stratum basale Stratum spinosum Stratum granulosum Stratum lucidum (only in thick skin) Stratum corneum
Table 4.1 Epidermal Layers These layers get nutrients from the dermis below These layers can not get nutrients and die (dry)
Figure 4.3 The Structure of the Epidermis These layers can not get nutrients and die (dry) Surface Stratum corneum These layers get nutrients from the dermis below Epidermis of thick skin LM 225 Stratum lucidum Stratum granulosum Stratum spinosum Stratum basale Basal lamina Dermis
Figure 4.4 Thin and Thick Skin Epidermis Epidermal ridge Dermal papilla Dermis Stratum corneum Basal lamina Stratum lucidum Dermis Dermal papilla Epidermal LM 240 ridge LM 240 The basic organization of the epidermis. The thickness of the epidermis, especially the thickness of the stratum corneum, changes radically depending on the location sampled. Thin skin covers most of the exposed body surface. (During sectioning the stratum corneum has pulled away from the rest of the epidermis.) Thick skin covers the surfaces of the palms and soles.
Figure 4.5 The Epidermal Ridges of Thick Skin Pores of sweat gland ducts Epidermal ridge SEM 25 Formed by the stratum basale
Skin Color Dependent on genetic information Factors that contribute to skin color: The dermal blood supply Variable quantities of two pigments: Melanin- yellow-brown protective pigment Carotene- an orange-yellow pigment
Figure 4.6 Melanocytes Melanocytes in stratum basale Melanin pigment Basal lamina Thin skin LM 600 This micrograph indicates the location and orientation of melanocytes in the stratum basale of a dark-skinned person. Melanosome Keratinocyte Melanin pigment Melanocyte Basal lamina Melanocytes produce and store melanin.
Figure 4.7 The Structure of the Dermis and the Subcutaneous Layer
Figure 4.8 Lines of Cleavage of the Skin Bundles of collagen and elastic fibers are arranged to resist applied forces ANTERIOR POSTERIOR
Figure 4.1 Functional Organization of the Integumentary System (Part 2 of 2) Hair Follicles Produce hairs that protect skull Produce hairs that provide delicate touch sensations on general body surface Exocrine Glands Accessory Structures Assist in thermoregulation Excrete wastes Lubricate epidermis Nails Protect and support tips of fingers and toes
Accessory Structures Hair Follicles and Hair Hair is a nonliving keratinized structure that extends beyond the surface of the skin in most areas of the body 98% of the 5 million hairs on the body are not on the head. Hair follicles are the epidermal organs that form the hairs Chief parts of a hair Root imbedded in the skin Shaft projects above skin's surface
Figure 4.9a Accessory Structures of the Skin Exposed shaft of hair Hair shaft Boundary between hair shaft and hair root Hair root Sebaceous gland Arrector pili muscle Connective tissue sheath Hair bulb Hair papilla A diagrammatic view of a single hair follicle
Figure 4.9b Accessory Structures of the Skin Epidermis Arrector pili muscle Dermis Sebaceous gland Hair shaft Hair follicle, cross section Hair Glassy membrane Subcutaneous adipose tissue Medulla Papilla External root sheath Connective tissue sheath of hair follicle Cortex Hair bulb Scalp, sectional view LM 66 A light micrograph showing the sectional appearance of the skin of the scalp. Note the abundance of hair follicles and the way they extend into the dermis.
Figure 4.10a Hair Follicles
Figure 4.10bc Hair Follicles Hair shaft External root sheath Connective tissue sheath of hair follicle Internal root sheath Glassy membrane Cuticle of hair Cortex of hair Medulla of hair Matrix Hair papilla Hair follicle LM 60 Subcutaneous adipose tissue Histological section along the longitudinal axis of a hair follicle Diagrammatic view along the longitudinal axis of a hair follicle
Hair growth cycle
Figure 4.12 A Classification of Exocrine Glands in the Skin Exocrine Glands Assist in thermoregulation Excrete wastes Lubricate epidermis consist of Secrete oily lipid (sebum) that coats hair shaft and epidermis Provide lubrication and antibacterial action Sebaceous Glands types Produce watery solution by merocrine secretion Flush epidermal surface Perform other special functions Sweat Glands types Typical Sebaceous Glands Sebaceous Follicles Apocrine Sweat Glands Merocrine Sweat Glands Secrete into hair follicles Secrete onto skin surface Limited distribution (axillae, groin, nipples) Produce a viscous secretion of complex composition Possible function in communication Strongly influenced by hormones Widespread Produce thin secretions, mostly water Merocrine secretion mechanism Controlled primarily by nervous system Important in thermoregulation and excretion Some antibacterial action special apocrine glands Ceruminous Glands Secrete waxy cerumen into external ear canal Mammary Glands Apocrine glands specialized for milk production
Sebaceous Glands Occur over entire body Except palms and soles Secrete sebum an oily substance Functions of sebum Inhibits growth of bacteria softens and lubricates hair and skin (keep from cracking)
Figure 4.13 Sebaceous Glands and Follicles Sebaceous follicle Sebaceous gland Lumen (hair removed) Wall of hair follicle Epidermis Dermis Subcutaneous layer Basal lamina Discharge of sebum Lumen Breakdown of cell walls Sebaceous gland Mitosis and growth Germinative cells LM 150
Sweat Glands Sweat glands (sudoriferous glands) widely distributed on body Apocrine sweat gland: found in armpits and groin after puberty; active under stress Eccrine (merocrine) sweat gland: found all over the body Thermoregulation (perspiration) Excretion (H20 & electrolytes) Protection (antibacterial action)
Figure 4.14 Sweat Glands Lumen Myoepithelial cell Connective tissue of dermis Apocrine gland cells Duct of apocrine sweat gland Sectional plane LM 440 through apocrine sweat gland Apocrine sweat glands are found in the axillae (armpits), groin, and nipples. They produce a thick, potentially odorous fluid. Sweat pore Duct Myoepithelial cells Merocrine gland cells Lumen Cross section of merocrine sweat gland LM 243 Merocrine sweat glands produce a watery fluid commonly called sensible perspiration or sweat.
Figure 4.15 Structure of a Nail Direction of growth Free edge Lateral nail fold Lateral nail groove Nail body Nail Lunula Eponychium Proximal nail fold Nail bed Phalanx (bone of fingertip) Cross-sectional view View from the surface Cuticle Eponychium Nail root is where nail production occurs Proximal nail fold Nail root Lunula Nail body Hyponychium Thickened Stratum corneum Epidermis Dermis Phalanx Longitudinal section
Local Control of Integumentary Function The integument can respond independently of the endocrine system and nervous system Mechanical stress can trigger stem cell divisions resulting in calluses. Regeneration occurs after damage The inability to completely heal after severe damage may result in acellular scar tissue Skin repairs process more rapidly in young, healthy individuals
The skin during the Aging Process Reduced Skin Repair skin repairs proceed more slowly