The Integumentary System Exercise 7 The Integumentary System

What is the integumentary system? An organ system Several tissue types functioning together Largest organ of body Many functions: Protection, insulation, cushion, prevent water loss, regulate heat loss, excretion through pores, vitamin D synthesis, sensory input

2 Main Regions Epidermis Dermis

EPIDERMIS: 4-5 layers SUPERFICIAL DEEP Stratum corneum Stratum lucidum Stratum granulosum Stratum spinosum Stratum basale

Figure 7.2 The main structural features in epidermis of thin skin. Keratinocytes Dendritic cell Stratum corneum Most superficial layer; 20–30 layers of dead cells, essentially 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 joined by desmosomes. Cells contain thick bundles of intermediate filaments made of pre-keratin. Stratum basale Deepest epidermal layer; one row of actively mitotic stem cells; some newly formed cells become part of the more superficial layers. Dermis Dermis Tactile (Merkel) cell Melanin granule Sensory nerve ending Desmosomes Melanocyte 6

TOP: Stratum corneum Stratum corneum Most superficial layer; 20–30 layers of dead cells, essentially flat membranous sacs filled with keratin. Glycolipids in extracellular space.

2nd (if present) Stratum lucidum Thin, clear layer Flattened dead cells, filled with keratin Only in “thick skin”: palms, soles Fig. 5-4

3rd (if thick skin) Stratum granulosum Stratum granulosum One to five layers of flattened cells, organelles deteriorating; Cytoplasm full of lamellar granules (release lipids) and keratohyaline granules. Fig. 5-4

4th Stratum spinosum Dendritic cell Stratum spinosum Several layers of keratinocytes joined by desmosomes. Cells contain thick bundles of intermediate filaments made of pre-keratin. Keratinocytes

5th (bottom) Stratum basale Stratum basale Deepest epidermal layer; one row of actively mitotic stem cells; some newly formed cells become part of the more superficial layers. Tactile (Merkel) cell Melanocyte Dermis Melanin granule Sensory nerve ending Desmosomes

Epidermal cells Keratinocytes: most abundant, produce keratin Melanocytes: produce melanin, shield nuclei from UV, freckle = many in one spot Langerhans cells: macrophages (immune system) that help stimulate a defense; in s. spinosum Merkel cells: sensory touch receptors; in s. basale

DERMIS: 2 layers Papillary layer Reticular layer superficial, just below the epidermis Reticular layer deep, below the papillary layer

• Sebaceous (oil) gland • Hair follicle Figure 7.1 Skin structure. Hair shaft Dermal papillae Epidermis Subpapillary plexus Papillary layer Sweat pore Dermis Appendages of skin Reticular layer • Eccrine sweat gland • Arrector pili muscle • Sebaceous (oil) gland • Hair follicle Hypodermis (subcutaneous tissue; not part of skin) • Hair root Cutaneous plexus Nervous structures Adipose tissue • Sensory nerve fiber with free nerve endings • Lamellar corpuscle • Hair follicle receptor (root hair plexus)

Papillary Layer Dermal papillae (projections) extend from upper dermis into epidermal ridges Epidermal ridges formed by stratum basale, at junction of epidermis & dermis  FINGERPRINTS! Areolar tissue

Reticular Layer Thicker layer Dense irregular connective tissue Fibers Vascular, glandular (sweat/sebaceous) Stretch marks: dermis is torn because stretched too far…then repaired

Dermal Cells Meissner’s corpuscles: light touch receptors in dermis—PAPILLARY LAYER Pacinian (lamellar) corpuscles: deep pressure receptors in dermis—RETICULAR LAYER

Hypodermis Deep to the dermis (below it) Superficial fascia layer Primarily adipose tissue NOT a part of the “skin”

Accessory Skin Organs Hair Nails Cutaneous Glands

Hair follicle Tubular depression in epidermis & dermis Where a hair develops Follicle wall

Hair bulb (root), within the hair follicle, the enlarged base

Root sheath Inner cylinder of epidermis surrounding hair root in the follicle • External epithelial root sheath • Internal epithelial root sheath

Arrector pili Smooth muscle cells Arrector pili muscle Arrector pili Smooth muscle cells Connect hair follicle to papillary layer Muscles contract  hair stands up, goosebumps b/c skin dimpled

Hair shaft Hair shaft Visible, dead (keratinized) portion of the hair

Figure 7.6 Photomicrographs of skin. Sloughing stratum corneum cells Epidermis Hair follicle Hair shaft Dermis Epidermis • Stratum corneum • Stratum lucidum • Stratum granulosum • Stratum spinosum • Stratum basale Dermis 25

NAILS Are in the integumentary system Don’t need to know the specifics FOR LAB

Cutaneous Glands Sebaceous Glands Sweat Glands Eccrine Apocrine

Sebaceous Glands “oil glands” Associated with hair follicle Secrete sebum into hair follicle to keep hair from being brittle (holocrine gland) Sebaceous gland

Sweat Glands Exocrine glands, all over body (pores) 2 types of fluid: Eccrine glands Forehead, back, palms, soles Clear perspiration (water, salts, urea: exocytosis), controls body temperature Merocrine glands Apocrine glands Much larger Axillary, pubic, mammary (specialized, produces milk) “cloudy” perspiration, odorous Olfactory communication--pheromones Eccrine gland

Skin Model Key: I. Epidermis II. Dermis III Skin Model Key: I. Epidermis II. Dermis III. Hypodermis (subcutaneous) 1. Stratum corneum 1a. Stratum lucidum 2. Stratum germatativum 2a. Stratum granulosum 2b. Stratum spinosum 2c. Stratum basale 3. Papillae 4. Touch (Meissner) corpuscle 5. Adipose tissue 6. Laminated (Pacinian) corpuscle 7. Sweat (Eccrine) gland 8. Hair (longitudinal section) 8a. Medulla 8b. Cortex 8c. Cuticle 8d. Internal epithelial root sheath 8e. External or outer epithelial root sheath 8f. Glassy (hyaloid) membrane 8g. Fibrous connective tissue root sheath 9. Hair (cross-section) 10. Hair shaft 11. Root 11a. Hair bulb 12. Hair papilla 13. Sebaceous glands 14. Arrector pili muscle 15. Sweat (apocrine) gland 15a. Smooth muscle cells 15b. Hyaline top 15c. Part of the pushed out cell body

Interactive website—quiz yourself! http://daphne.palomar.edu/ccarpenter/Models/skin_model_2.htm

Review Figure 7.1 36