KNES 260 Lecture Notes - Lecture 12: Hair Follicle, Cholecalciferol, Subcutaneous Tissue
27 Feb 2017
School
Department
Course
Professor
Integumentary System
Components
● Cutaneous membrane (epidermis and dermis)
● Accessory structures (glands, hairs, etc.)
● Subcutaneous layer
Functions
● Protection
● Excretion of waste products
● Temperature regulation
● Nutrient storage
● Vitamin D3 synthesis
● Sensory detection
Epidermis
● Composed of layers of keratinocytes
○ Four layers of thin skin
○ Five layers of thick skin (thin has hair, thick does not)
● Provides mechanical protection
● Prevents fluid loss
● Keeps microorganisms from invading the body
● As they are pushed up from the dermis they gain keratin until they are eventually shed
● Epidermal ridges are interlocked with dermal papillae as they lack hairs
○ Ridges are fingerprints
○ Improve gripping ability
● Skin colour depends on
○ Blood supply, carotene and melanin, epidermal pigmentation (reason people with
pale skin have moles)
Epidermal Cells
● Synthesize vitamin D3 when exposed to UV radiation
● Respond to epidermal growth factor with growth, division, and repair
Dermis
Papillary Layer
● Contains blood vessels, lymphatic vessels, sensory nerves
Reticular layer
● Contains network of collagen and elastin fibers to resist tension
○ Reason skin is stretchy and elastic
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Document Summary
Five layers of thick skin (thin has hair, thick does not) As they are pushed up from the dermis they gain keratin until they are eventually shed. Epidermal ridges are interlocked with dermal papillae as they lack hairs. Blood supply, carotene and melanin, epidermal pigmentation (reason people with pale skin have moles) Synthesize vitamin d3 when exposed to uv radiation. Respond to epidermal growth factor with growth, division, and repair. Contains blood vessels, lymphatic vessels, sensory nerves. Contains network of collagen and elastin fibers to resist tension. Stretch marks are caused by excessive stretching of the dermis. Patterns of collagen and elastic fibers form lines of cleavage. Lines of cleavage are naturally occurring and allow for movement of the body. They form over typical areas of stress. They keep skin attached to the subcutaneous fat and tissue. Stabilizes skins position against underlying organs and tissues. Composed of a root (papilla) and a shaft (part which is outside the skin)
