Download presentation
Presentation is loading. Please wait.
1
5 The Integumentary System
2
The Skin and the Hypodermis
Skin—our largest organ Accounts for 7% of body weight Varies in thickness from 1.5 to 4.4mm Divided into two distinct layers Epidermis Dermis Hypodermis—lies deep to the dermis Composed of areolar and adipose tissues Not part of the integumentary system, but shares some of skin’s properties
3
Subpapillary vascular plexus Papillary dermis
Figure 5.1 Skin structure. Hair shaft Dermal papillae Epidermis Subpapillary vascular plexus Papillary dermis Sweat pore Appendages of skin Dermis Reticular dermis Eccrine sweat gland Arrector pili muscle Sebaceous (oil) gland Hair follicle Hair root Hypodermis (superficial fascia) Nervous structures Sensory nerve fiber with free nerve endings Dermal vascular plexus Lamellar corpuscle Adipose tissue Hair follicle receptor (root hair plexus) 3
4
Figure 5.2 Gross structure of skin and underlying tissues.
Epidermis Dermis Hypodermis Deep fascia Muscle 4
5
The Skin and Hypodermis
Five important functions 1. Protection Cushions organs and protects from bumps, chemicals, water loss, ultraviolet (UV) radiation 2. Body temperature regulation Capillary network and sweat glands regulate heat loss 3. Excretion Urea, salts, and water lost through sweat
6
The Skin and Hypodermis
Functions (continued) 4. Production of vitamin D Epidermal cells use UV radiation to synthesize vitamin D 5. Sensory reception Contains sense organs associated with nerve endings
7
Is composed of keratinized stratified squamous epithelium
Epidermis Is composed of keratinized stratified squamous epithelium Contains four main cell types Keratinocytes Location—stratum spinosum; produce keratin, a fibrous protein Melanocytes Location—basal layer; manufacture and secrete pigment
8
Contains four main cell types (continued)
Epidermis Contains four main cell types (continued) Tactile epithelial cells Location—basal layer; attached to sensory nerve endings Dendritic cells Location—stratum spinosum; part of immune system; macrophage-like
9
Keratinocytes—most abundant cell type in epidermis
Arise from deepest layer of epidermis Produce keratin, a tough fibrous protein Produce antibiotics and enzymes Keratinocytes are dead at skin’s surface
10
Layers of the Epidermis
Stratum basale (stratum geminativum) Stratum spinosum Stratum granulosum Stratum lucidum (only in thick skin) Stratum corneum
11
Figure 5.3a Epidermal cells and layers of the epidermis.
Stratum corneum Most superficial layer; 20–30 layers of dead cells represented only by flat membranous sacs filled with keratin. Glycolipids in extracellular space. Stratum granulosum One to five layers of flattened cells, organelles deteriorating; cytoplasm full of lamellar granules (release lipids) and keratohyaline granules. Stratum spinosum Several layers of keratinocytes unified by desmosomes. Cells contain thick bundles of intermediate filaments made of pre-keratin. Desmosomes Stratum basale Deepest epidermal layer; one row of actively mitotic stem cells; some newly formed cells become part of the more superficial layers. See occasional melanocytes and dendritic cells. Dermis 11
12
Figure 5.3b Epidermal cells and layers of the epidermis.
Stratum corneum Most superficial layer; 20–30 layers of dead cells represented only by flat membranous sacs filled with keratin. Glycolipids in extracellular space. Keratinocytes Stratum granulosum One to five layers of flattened cells, organelles deteriorating; cytoplasm full of lamellar granules (release lipids) and keratohyaline granules. Stratum spinosum Several layers of keratinocytes unified by desmosomes. Cells contain thick bundles of intermediate filaments made of pre-keratin. Desmosomes Stratum basale Deepest epidermal layer; one row of actively mitotic stem cells; some newly formed cells become part of the more superficial layers. See occasional melanocytes and dendritic cells. Dermis Dendritic cell Sensory nerve ending Melanocyte Melanin granule Tactile epithelial cell 12
13
Layers of the Epidermis
Stratum basale Deepest layer of epidermis Attached to underlying dermis Cells actively divide Stratum basale contains Tactile epithelial cells—associated with sensory nerve ending Melanocytes—secrete the pigment melanin
14
Epidermis Stratum corneum Stratum lucidum Stratum granulosum
Figure 5.4 Thick skin. Epidermis Stratum corneum Stratum lucidum Stratum granulosum Stratum spinosum Dermis Stratum basale Papillary dermis Dermal papilla Reticular dermis Collagen fibers 14
15
Layers of the Epidermis
Stratum spinosum (spiny layer) “Spiny” appearance caused by artifacts of histological preparation Contains thick bundles of intermediate filaments (tonofilaments) Resist tension and contain the protein prekeratin Among the keratinocytes are star-shaped dendritic cells Are a type of macrophage Function in immune system
16
Layers of the Epidermis
Stratum granulosum Consists of a few layers of keratinocytes Keratinocytes contain Keratohyaline granules—help form keratin Lamellar granules—contain waterproofing glycolipid Above stratum granulosum Cells are too far from dermal capillaries to receive nourishment
17
Layers of the Epidermis
Stratum lucidum (clear layer) Occurs only in thick skin Locations of thick skin—palms and soles Composed of a few rows of flat, dead keratinocytes
18
Layers of the Epidermis
Stratum corneum (horny layer) Thick layer of dead keratinocytes and thickened plasma membranes Protects skin against abrasion and penetration
19
Second major region of the skin Strong, flexible connective tissue
Dermis Second major region of the skin Strong, flexible connective tissue Richly supplied with blood vessels and nerves Has two layers Papillary dermis—includes dermal papillae Reticular dermis Deeper layer—80% of thickness of dermis
20
Includes dermal papillae
Papillary Dermis Includes dermal papillae Increase surface area for exchange of gases, nutrients, and wastes Dermal papillae lie on dermal ridges Epidermal ridges (friction ridges)—elevations of dermal ridges Are fingerprints Increase gripping ability of hands and feet
21
Accounts for 80% of dermal thickness Dense irregular connective tissue
Reticular Dermis Accounts for 80% of dermal thickness Dense irregular connective tissue Reticular dermis Has rich nerve supply Has two vascular plexuses Dermal plexus Subpapillary plexus Blood vessels play important role in temperature regulation
22
Figure 5.5 Dermal modifications.
Openings of sweat gland ducts Friction ridges Flexure lines on digit Friction ridges of fingertip (SEM 12) Flexure lines on the palm Cleavage lines in the reticular dermis Flexure lines of the hand 22
23
Contains areolar and adipose connective tissue
Hypodermis Deep to the skin Also called superficial fascia Contains areolar and adipose connective tissue Anchors skin to underlying structures Helps insulate the body Has different distribution in males and females
24
Three pigments contribute to skin color
Melanin Most important pigment—made from tyrosine Carotene Yellowish pigment from carrots and tomatoes Hemoglobin Caucasian skin contains little melanin Allows crimson color of blood to show through
25
Nails—scalelike modification of epidermis
Made of hard keratin Parts of the nail Free edge Body Root Nail folds Eponychium—cuticle
26
Figure 5.6 Structure of a nail.
Lateral nail fold Lunule Free edge of nail Nail root Eponychium (cuticle) Nail plate Nail matrix Proximal nail fold Nail bed Phalanx (bone of fingertip) 26
27
Appendages of the Skin Hair Flexible strand of dead, keratinized cells
Hard keratin—tough and durable Chief parts of a hair Root—embedded in the skin Shaft—projects above skin’s surface
28
Hair has three concentric layers of keratinized cells
Appendages of the Skin Hair has three concentric layers of keratinized cells Medulla—central core Cortex—surrounds medulla Cuticle—outermost layer
29
Figure 5.7a Structure of a hair and hair follicle.
Hair shaft Arrector pili Sebaceous gland Follicle wall Peripheral connective tissue (fibrous) sheath Hair root Glassy membrane Hair bulb Epithelial root sheath External root sheath Internal root sheath Hair Cuticle Cortex Medulla Diagram of a cross section of a hair within its follicle 29
30
Figure 5.7b Structure of a hair and hair follicle.
Follicle wall Peripheral connective tissue (fibrous) sheath Glassy membrane Epithelial root sheath External root sheath Internal root sheath Hair Cuticle Cortex Medulla Photomicrograph of a cross section of a hair and hair follicle (120) 30
31
Appendages of the Skin Hair follicles Hair bulb Root plexus
Extend from epidermis into dermis Hair bulb Deep, expanded end of the hair follicle Root plexus Knot of sensory nerves around hair bulb
32
Figure 5.7c Structure of a hair and hair follicle.
Hair shaft Follicle wall Peripheral connective tissue (fibrous) sheath Glassy membrane Arrector pili Epithelial root sheath External root sheath Sebaceous gland Internal root sheath Hair root Hair root Cuticle Cortex Hair bulb Medulla Hair matrix Dermal papilla Melanocyte Subcutaneous adipose tissue Diagram of a longitudinal view of the expanded hair bulb of the follicle, which encloses the matrix 32
33
Figure 5.7d Structure of a hair and hair follicle.
Follicle wall Peripheral connective tissue (fibrous) sheath Glassy membrane Epithelial root sheath External root sheath Internal root sheath Hair root Cuticle Cortex Medulla Hair matrix Dermal papilla Subcutaneous adipose tissue Photomicrograph of longitudinal view of the hair bulb in the follicle (150) 33
34
Appendages of the Skin Wall of hair follicle Arrector pili muscle
Connective tissue root sheath Epithelial tissue root sheath Arrector pili muscle Bundle of smooth muscle Hair stands erect when arrector pili contracts
35
Secrete sebum—an oily substance
Sebaceous Glands Occur over entire body Except palms and soles Secrete sebum—an oily substance Simple alveolar glands Holocrine secretion—entire cell breaks up to form secretion Most are associated with a hair follicle Functions of sebum Collects dirt; softens and lubricates hair and skin
36
Dermal connective tissue Hair in hair follicle
Figure 5.8a Skin glands. Sebaceous gland Sweat pore Sebaceous gland duct Dermal connective tissue Hair in hair follicle Eccrine gland Secretory cells Photomicrograph of a sectioned sebaceous gland (90) 36
37
Sweat glands (sudoriferous glands) widely distributed on body
Sweat—is a blood filtrate 99% water with some salts Contains traces of metabolic wastes About 2% urea
38
Dermal connective tissue
Figure 5.8b Skin glands. Sebaceous gland Sweat pore Eccrine gland Duct Dermal connective tissue Secretory cells Photomicrograph of a sectioned eccrine gland (140) 38
39
Two types of sweat gland
Sweat Glands Two types of sweat gland Eccrine gland (merocrine) Most numerous—these produce true sweat Apocrine gland Confined to axillary, anal, and genital areas Produce a special kind of sweat Musky odor—attracts a mate Signal information about a person’s immune system, major histocompatibility complex (MHC) Ceruminous glands and mammary glands Modified apocrine glands
40
Classified by severity
Burns Classified by severity First-degree burn—only upper epidermis is damaged Second-degree burn—upper part of dermis is also damaged Blisters appear Skin heals with little scarring Third-degree burn Consumes thickness of skin Burned area appears white, red, or blackened
41
Anterior and posterior head and neck, 9%
Figure 5.9 Burns. Anterior values Totals 4½% 1st degree burn Anterior and posterior head and neck, 9% Anterior and posterior upper limbs, 18% 2nd degree burn 4½% 4½% Anterior and posterior trunk, 36% Anterior trunk, 18% Skin bearing partial-thickness burn (first- and second-degree burn) 3rd degree burn 9% 9% (Perineum, 1%) Anterior and posterior lower limbs, 36% 100% Skin bearing full-thickness burn (third-degree burn) Rule of nines; used to estimate extent of burns 41
42
Squamous cell carcinoma
Skin Cancer Basal cell carcinoma Least malignant and most common Squamous cell carcinoma Arises from keratinocytes of stratum spinosum Melanoma A cancer of melanocytes The most dangerous type of skin cancer
43
Figure 5.10 Photographs of skin cancers.
Basal cell carcinoma Squamous cell carcinoma Melanoma 43
Similar presentations
