KIN 223 CHAPTER 6 LESSON OBJECTIVES

6.1.1 Describe the structure, composition, arrangement, and functions of the five layers (strata) of the epidermis.

Come Let’s Get Sun Burned 

• Stratum Corneum 

-Most superficial layer of the epidermis

-Has 20-30 layers of dead, flattened, anucleate, keratin-filled keratinocytes

• Stratum Lucidum 

-It may not be there, seen only in thick skin (palms of hands, soles of feet)

• Stratum Granulosum 

- 3 to 5 layers of keratinocytes

-Keratinocytes begin keratinization (it kills)

-Nucleus and organelles disintegrate, cells are dead 

• Stratum Spinosum 

-Several layers of keratinocytes

-New cells from stratum basale pushed into this layer

-Epidermal dendritic cells present

• Stratum Baseale

-Deepest epidermal layer 

-Single layer of cuboidal to lower columnar cells 

-3 cell types

-Keratinocytes

-Found in all layers

-Those in stratum basale are large stem cells

-Divide to regenerate new cells

-Synthesize keratin (protein that strengths epidermis)

-Melanocytes

-Make (produce/store) melanin in response to UV (ultraviolet light)

-Tactile cells (also called Merkel cells)

-Few in number

-Sensitive to touch

6.1.2 Compare the variations in thickness, color, and markings of the epidermis.

Thickness 

• Thick skin 

-Palms of hands, soles of feet

-5 layers of epidermal strata

-Sweat glands but no hair follicles or sebaceous glands

• Thin skin 

-Covers most of body 

-Lacks stratum lucidum 

Sweat glands but had hair follicles or sebaceous glands 

Color (skin color)

• Hemoglobin 

-Oxygen-binding protein in red blood cells

-Right red color upon binding oxygen

• Melanin (responds to UV light) 

-Dark pigment produced in melanocytes

-Eumelanin– brown and black shades

-Pheomelanin– lighter shades

• Carotene

-Yellow-orange pigment acquired from some vegetables

Markings

• Nevus-mole 

• Freckles - yellowish or brown sports 

-Due to melanocyte activity 

• Hemangiomas– skin discoloration due to benign blood vessel tumor

• Friction ridges–fingerprints

-Large folds and valleys of dermis and epidermis 

6.1.3 Describe the structure, organization, and functions of the layers of the dermis.

Contains two layers - Papillary and reticular layers 

• Papillary 

-Superficial region of dermis 

-Has areolar connective tissue

-Dermal papillae (little mount, each makes the papillary layer) 

• Reticular layer

-Deeper, major portion of dermis

-Has dense irregular connective tissue 

6.1.4 Explain the significance of cleavage lines.

Collagen (fight tension) and elastic (stretch and recoils) fibers located in the dermis 

• Help resist stress during routine movement 

Lines of cleavage 

• Incisions parallel to cleavage lines more likely to heal 

- If cut, cleavage lines heal quickly 

• Incisions perpendicular to cleavage lines more likely to open (due to cut elastic fibers) 

-If cut, cleavage lines may gape and delay healing 

6.1.5 Describe the structure and function of the subcutaneous layer.

*Deep to dermis but it is NOT part of the integumentary system 

• Has areolar and adipose CT

• Function: protection, energy stores, insulation 

6.1.6 List and explain the varied functions of the integument.

• Protection 

-Injury, harmful substances, UV radiation; etc

• Prevention of water loss/gain 

-Water lost by sweat and transpiration 

• Vitamin D synthesis 

• Secretion, absorption, immune function, temperature regulation, sensory reception 

6.1.7 Explain how the skin helps retain warmth or cool the body.

• Temperature regulation-dermal blood vessels capable of vasoconstriction (to conserve heat) or vasodilation (release heat) 

6.2.8 Describe the structure and function of nails.

• Form on the dorsal edges of fingers and toes

• Function: protect the distal tips of the digits during jumping, kicking, or catching

  • Fingernails also assist us in grasping objects

• Light colored free edge

• Darker colored nail body

• Nail root: proximal part embedded into the skin 

• All these parts form nail plate 

• Nail body covers layer of epidermic called nail bed which contains only deeper living cell layers of the epidermis 

6.2.9 Describe the structure, distribution, and function of hair.

• Found almost everywhere in the body except for the palms of the hands and palmar surface of fingers, sides and soles of feet and toes, lips, and portions of the external genitalia 

• Hairbulb: base where hair originates 

• Hair papila: small CT containing tiny blood vessels and nerves

• Root: zone of hair extending from bulb to skin surface

• Shaft: ectends beyond skin surface

• Hair matrix: in hair bulb

• Functions:

  • Protection 

  • Heat retention

  • Sensory reception

  • Visual identification 

6.2.10 Describe how hair changes throughout life (i.e., the hair growth cycle).

• Anagen phase: growth where living cells of hair bulb are rapidly growing, dividing and transforming into hair

• Catagen phase: cell division ceases and follicle undergoes involution

• Telogen phase: phase where hair is shed 

6.2.11 Compare and contrast the structure, function, and location of the two types of exocrine glands of the skin.

• Merocrine sweat glands: simple coiled tubular glands that discharge their secretions directly onto surface of skin

  • Major function is thermoregulation 

• Apocrine sweat glands: coiled tubular glands that release their secretion into hair follicles axill, around nipples, and in pubic and anal region 

6.3.12 Distinguish between regeneration and fibrosis.

• Regeneration: replacement of damaged or dead cells with the same cell type by cell division

  • Restores tissue function

• Fibrosis: process of scar tissue deposition in connective tissue healing

  • Binds damage parts together

6.3.13 Describe the process of wound healing.

• Cut blood vessel bleed into wound

• Blood clot forms and leukocytes clean wound

• Blood vessels regrow and granulation tissue forms 

• Epithelium regenerates and connective tissue fibrosis occurs

6.4.14 Describe how integument develops from ectoderm and mesoderm.
- Development around week 7 (has 3 layers, endoderm, ectoderm, and mesoderm) 

• Ectoderm forms a layer of squamous epithelium 

- Becomes periderm and basal layer (forms all epidermal layers)

By week 21 

• Formation of stratum corneum and friction ridges 

-Periderm disappears 

-Mixes with sebum to make vernix caseosa

Development between week 11 

• Dermis derived from mesoderm (it becomes mesenchyme) 

6.4.15 Explain the developmental origins of nails, hair, and glands.

• Start to form in 10th week of development 

• Fingernails reach tips by 32 weeks toenails 36

• Hair Follicles appear 9-12 weeks of development 

• First appear 20 weeks

6.4.16 List the changes that occur in the skin during aging, and explain the factors that contribute to those changes.

• Reduced number and activity of stem cells resulting in thinner skin 

  • Less likely to protect against abrasive mechanical trauma 

• Collagen fibers decrease in dermis 

6.4.17 Describe the risk factors, warning signs, and characteristics of skin cancer

• To much UV exposure 

• Moles that form after a sunburn 

• Raised scales