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Integumentary System
Question | Answer |
---|---|
Largest organ Accounts for 7% of body weight Varies in thickness from 1.5–4.4mm Divided into two distinct layers Epidermis Dermis | The Skin |
lies deep to the dermis | Hypodermis |
What are the functions of the Skin and Hypodermis? | Protection— from bumps, chemicals, water loss, UV radiation Regulation of body temperature Excretion— urea, salts, and water lost through sweat Production of vitamin D Sensory reception—keeps us aware of conditions at the body’s surface |
4 main cell types of Epidermis | Keratinocytes -tratum spinosum; produce keratin a fibrous protein Melanocytes-basal layer; secrete pigment Tactile epithelial cells-basal layer; attached to sensory nerve endings Dendritic cells-stratum spinosum; part of immune system; macrophage-like |
most abundant cell type in epidermis Arise from deepest layer of epidermis Produce keratin, a tough fibrous protein Produce antibodies and enzymes Dead at skin's surface | Keratinocytes |
5 Layers of the Epidermis | A) Stratum basale (stratum geminativum) B) Stratum spinosum C) Stratum granulosum D) Stratum lucidum (only in thick skin) E) Stratum corneum |
Deepest layer of epidermis Attached to underlying dermis Cells actively divide Stratum basale contains Merkel cells—associated with sensory nerve ending Melanocytes—secrete the pigment melanin | A) Stratum basale |
“Spiny” appearance caused by artifacts of histological preparation Contains thick bundles of intermediate filaments (tonofilaments) Resist tension Contain protein prekeratin and star-shaped dendritic cells Function in immune system (as macrophages) | B) Stratum spinosum (spiny layer) |
Consists of keratinocytes and tonofilaments Tonofilaments contain: Keratohyaline granules—help form keratin Lamellated granules—contain a waterproofing glycolipid | C) Stratum granulosum |
Occurs only in thick skin Locations of thick skin—palms and soles Composed of a few rows of flat, dead keratinocytes | D) Stratum lucidum (clear layer) |
Thick layer of dead keratinocytes and thickened plasma membranes Protects skin against abrasion and penetration | E) Stratum corneum (horny layer) |
Second major layer of the skin Strong, flexible connective tissue Richly supplied with blood vessels and nerves | Dermis |
2 layers of the dermis | Papillary layer—includes dermal papillae Reticular layer Deeper layer—80% of thickness of dermis |
Creases on palms are called: | Flexure lines |
Deep to the skin—also called superficial fascia Contains areolar and adipose CT Anchors skin to underlying structures Helps insulate the body | Hypodermis |
3 pigments that contribute to skin color: | i) Melanin Most important pigment—made from tyrosine ii) Carotene Yellowish pigment from carrots and tomatoes iii) Hemoglobin Caucasian skin contains little melanin Allows crimson color of blood to show through |
scalelike modification of epidermis Made of hard keratin | Nails |
Parts of The Nail | Free edge Body Root Nail folds Eponychium—cuticle |
Flexible strand of dead, keratinized cells Hard keratin—tough and durable | Hair |
2 Parts of Hair | Root—imbedded in the skin Shaft—projects above skin's surface |
3 layers of Hair | i) Medulla—central core ii) Cortex—surrounds medulla iii) Cuticle—outermost layer |
Extend from epidermis into dermis | Hair follicles |
Deep, expanded end of the hair follicle | Hair bulb |
Knot of sensory nerves around hair bulb | Root plexus |
Bundle of smooth muscle Hair stands erect when this contracts | Arrector pili muscle |
Body hairs of women and children | Vellus hairs |
Hair of scalp Axillary and pubic area (at puberty) | Terminal hairs |
Occur over entire body Except palms and soles Secrete sebum—an oily substance | Sebaceous Glands |
entire cell breaks up to form secretion Most are associated with a hair follicle | Holocrine secretion |
Functions of sebum | Collects dirt; softens and lubricates hair and skin |
glands (sudoriferous glands) widely distributed on body | Sweat glands |
a blood filtrate 99% water with some salts Contains traces of metabolic wastes About 2% urea | Sweat |
2 types of sweat glands | Eccrine gland (merocrine) Most numerous—produce true sweat Apocrine gland Confined to axillary, anal, and genital areas Musky odor-attracts mate Signal about immune system, MHC (Ceruminous glands and mammary glands are modified apocrine glands) |
only upper epidermis is damaged from burns | First-degree burn |
upper epidermis and upper part of dermis is also damaged from burns | Second-degree burn (Blisters appear Skin heals with little scarring) |
Consumes thickness of skin Burned area appears white, red, or blackened | Third-degree burn |
Least malignant and most common skin cancer | Basal cell carcinoma |
Skin cancer that arises from keratinocytes of stratum spinosum | Squamous cell carcinoma |
A cancer of melanocytes The most dangerous type of skin cancer | Melanoma |
Develops from embryonic ectoderm | Epidermis |
Develop from mesoderm | Dermis and hypodermis |
Develop from neural crest cells | Melanocytes |
vernix caseosa | produced by Fetal sebaceous glands |
Fetal skin is well formed after the fourth month. At 5–6 months, the fetus is covered with lanugo (downy hairs) | Fetal skin is well formed after the fourth month. At 5–6 months, the fetus is covered with lanugo (downy hairs) |