Integumentary System _______________ membrane (skin) – our largest organ Accounts for _____ of body weight Divided into two distinct layers __________ Accessory structures Subcutaneous layer (_______________)

Functions Of The Integument _____________ and insulates deeper organs _____________ body from abrasion, trauma, chemicals, pathogens, temperature extremes and UV rays ___________ and ___________ Contains ____________________associated with nerve endings Synthesis and storage of nutrients (______________)

Integumentary Structures Components of the Integumentary System Figure 5-1

Skin Structures

The Epidermis- Four Main Cell Types _____________ - found in basal layer, manufacture and secrete pigment ______________ - basal layer, attached to sensory nerve endings _______________ – Arise from deepest layer of epidermis to stratum spinosum Produce __________ – a tough fibrous protein Produce _____________ and __________ Keratinocytes are dead at skin's surface __________________ - stratum spinosum, part of immune system macrophage-like

The Epidermis Stratified squamous epithelium Several distinct cell layers ________________—five layers on palms and soles ________________—four layers on rest of body

Layers of The Epidermis Stratum ____________ Most _______________ layer Dead, flattened (squamous) cells Abundant keratin - __________ (cornified) tough, water-resistant protein Protects skin against abrasion and penetration Stratum ___________ (clear layer) Occurs only in thick skin – palms and soles Composed of a few rows of flat, dead keratinocytes

Layers of The Epidermis Stratum ___________ (grainy layer) Consists of keratinocytes Tonofilaments Keratohyaline granules – help form keratin Lamellated granules – contain a waterproofing glycolipid Stratum ___________ (spiny layer) “Spiny” appearance caused by artifacts of histological preparation Contains thick bundles of intermediate filaments (tonofilaments) Resist ____________ Contain protein _____________ Contains _____________ Langerhans cells

Layers of the Epidermis Stratum ___________ __________ layer of epidermis Attached to underlying dermis _____________ actively divide __________– associated with sensory nerve ending __________ – secrete the pigment melanin

Epidermal Cells and Layers of the Epidermis Figure 5.3

Sources of Skin Color Melanocytes Make ________from tyrosine Melanin provides _____ protection Gives ____________ to brown-black color Carotene Contributes _________________ Provided from _____ (carrots and tomatoes) Hemoglobin - blood pigment Caucasian skin contains little ___________ Allows __________ color of blood to show through

Dermis _____________ major layer of the skin Provides mechanical strength, ___________, and protection for underlying tissues ___________________and contains a variety of sensory receptors that provide information about the external environment Two layers ________________– includes dermal papillae ______________- d eeper layer – 80% of thickness of dermis _________________- creases on palms

Layers of the Dermis Papillary layer Underlies epidermis Named for dermal papillae Aerolar __________________ Supports, nourishes epidermis Provides sensory nerves, lymphatics, and ____________ Reticular layer Tough, dense, fibrous layer Dense __________________ Collagen fibers - limit ________ Elastic fibers - provide __________ Blends into papillary layer (above) Blends into _______________ layer (below)

Dermal Components Epidermal accessory organs Cells of connective ________________ Communication with other organ systems _______________ ______________ _____________ Sensation Control of blood flow and secretion

Subcutaneous Layer - Hypodermis Composed ____________________________________________ ______________ skin position Loosely attached to dermis Loosely attached to muscle Contains _________________cells Provides ________________ ______________ underlying organs Safely receives hypodermic needles

Hair ___________ strands of dead keratinized cells produced by hair follicles Contains hard ___________ which is tougher and more durable than soft keratin of the skin Chief parts of a hair ___________ – imbedded in the skin ____________ – projects above skin's surface

Hair Hair Shaft organized into three concentric layers ___________ – central core __________ – surrounds medulla ___________ – outermost layer Pigmented by melanocytes at the base of the hair

Cross Section of a Hair Figure 5.7a, b

Hair Follicle ____________extending from the epidermal surface into the dermis Deep end is expanded forming _____________ __________ - nipple-shaped indentation with blood vessels and nerves _________ - germinal layer of cells (actively dividing cells) right above the papilla A knot of _____________ (a root hair plexus) wraps around each hair bulb _______________stimulates these endings, hence our hairs act as sensitive touch receptors ____________muscle - b undle of smooth muscle contracts to make hair stand erect

Longitudinal Section of Follicle Figure 5.7c, d

Hair Follicles

Hair Function and Distribution Functions of hair include: Helping to maintain _____________ Alerting the body _________________on the skin Guarding the scalp against ____________, heat loss, and sunlight Hair is distributed over the entire skin surface except __________,__________,________ Nipples and portions of the external genitalia

Sebaceous Glands (oil glands) Occur over entire body - Except palms and soles Simple ____________________ _______________ secretion – entire cell breaks up to form secretion Secretes an oily substance called _________ Most are associated with a _____________ Functions of sebum Softens and lubricates hair and skin ___________________

Sweat (Sudoriferous) Glands Two types: __________________ Most abundant sweat gland “True sweat” 99% water with some salts Contains traces of metabolic wastes ~ 2% urea Role in _________________ Widely present in skin (up to 500/cm 2 ) ______________ Odorous secretion Absent before ___________ Present in axillary, areolar, anal and genital areas

Eccrine (Merocrine) Gland Figure 5.10b

Nails _____________ modification of epidermis made of hard keratin Parts of the nail Free edge Body - d ense mass of _______________ Root Nail folds _____________– cuticle

Skin Injury and Repair Four Stages in Skin Healing ______________ Blood flow increases Phagocytes attracted ______________ Cell division and migration ___________ formation

Bleeding occurs at the site of injury immediately after the injury, and mast cells in the region trigger an inflammatory response. Epidermis Dermis After several hours, a scab has formed and cells of the stratum germinativum are migrating along the edges of the wound. Phagocytic cells are removing debris, and more of these cells are arriving with the enhanced circulation in the area. Clotting around the edges of the affected area partially isolates the region. Sweat gland Scab Macrophages and fibroblasts Migratory epithelial cells Granulation tissue Skin Injury and Repair

One week after the injury, the scab has been undermined by epidermal cells migrating over the meshwork produced by fibroblast activity. Phagocytic activity around the site has almost ended, and the fibrin clot is disintegrating. Fibroblasts After several weeks, the scab has been shed, and the epidermis is complete. A shallow depression marks the injury site, but fibroblasts in the dermis continue to create scar tissue that will gradually elevate the overlying epidermis. Scar tissue Skin Injury and Repair

Table 5-1

Aging of the Skin Major Age-Related Changes _____ and infection increase Immune cells ___________ Sun protection diminishes Skin becomes dry, ________ Hair thins, ________ Sagging, _________ occur Heat loss ___________ Repair ________

Effects of UV Radiation Beneficial effect - activates synthesis of vitamin D 3 Harmful effects ___________ Wrinkles, ___________ ___________________

Types and Growth of Hair _________ hairs Body hairs of women and children _________ hairs Hair of scalp Axillary and pubic area (at puberty) _______________________ Due to aging Male pattern baldness

Burns Classified by severity _______________– only upper epidermis is damaged _______________– upper part of dermis is also damaged _____________ appear Skin heals with little scarring ___________________ Consume ______________ of skin Burned area appears white, red, or _______________

Estimating Burns Using the Rule of Nines Figure 5.11a

Skin Cancer _______________________ Least malignant and ________________ _______________________ Arises from ________________ of stratum spinosum ________________ A cancer of _________________ The most dangerous type of skin cancer

Skin Cancer Squamous cell carcinoma Figure 5.12 Melanoma Squamous cell carcinoma Basal cell carcinoma

The Skin Throughout Life ______________ Develops from embryonic ectoderm ________________ Develop from mesoderm _________________ Develop from neural crest cells

The Skin Throughout Life Fetal skin Well formed after the ________________ At 5-6 months The fetus is covered with __________ (downy hairs) Fetal sebaceous glands produce ___________________

The Skin Throughout Life Middle to old age Skin thins and becomes _____________ Shows ____________ effects of environmental damage Skin ______________ become more common