Lecture 1: ANATOMY OF THE SKIN - Part 1 Flashcards
Skin is the…
largest and most (only) visible organ of the body
What portion of body weight is skin?
16%
What surface area is skin?
1.5-2 square metres
What makes humans unique?
Our bare (not much hair), sweaty (lots of sweat glands) skin
What are the functions of skin?
Protect, excrete, maintain, produce, synthesise, store and detect
What does the skin protect?
Underlying tissues and organs against impact, abrasion, fluid loss and chemical attack
What does the skin excrete?
Salts, water and organic wastes by integumentary glands
What does the skin maintain?
Normal body temperature through either insulation or evaporative cooling as needed (thermoregulation)
What does the skin produce?
Melanin and keratin
What does melanin do?
Protect underlying tissue from ultraviolet radiation
What does keratin do?
Protect against abrasion and serves as a water repellent (hair and nails)
What does the skin synthesise?
Vitamin D3, a steroid that is subsequently converted into calcitriol, which is a hormone important to normal calcium metabolism
What does the skin store?
Lipids in adipocytes in the dermis and in adipose tissue in the subcutaneous layer
What does the skin detect?
Touch, pressure, pain, and temperature stimuli, and relay that information to the nervous system
What happens at the chemical level?
Atoms combine to form molecules
What happens at the cellular level?
Molecules interact to form cells that secrete and regulate extracellular materials and fluids
What happens at the tissue level?
Cells and extracellular materials and fluids combine to form tissues
What does epithelial tissue do?
Cover exposed surfaces, line internal passageways and chambers and form secretory glands
What does connective tissue do?
Fill internal spaces, provide structural support and store energy
What does muscle tissue do?
Contract to produce movement. Includes skeletal, cardiac and smooth muscle
What does nervous tissue do?
Conduct electrical impulses and carry information
What tissue is skin made of?
Epithelial, connective, muscle and nervous
What are the 3 layers of the skin?
Epidermis, dermis and hypodermis
What is in the cutaneous layer?
Epidermis and dermis
What is in the subcutaneous layer?
Hypodermis
What is the epidermis?
Stratified barrier, mostly keratinocytes ( cells with large amounts of keratin), no circulation (avascular)
What happens id a cut doesn’t go beyond the epidermis?
No bleeding
What is the dermis?
Protein fibres for strength and vascular (nourishes epidermis)
What is the hypodermis?
Adipose tissue- insulation
What is within the dermis?
Papillary layer and reticular layer
Describe the border between the epidermis and dermis
Has papule which increase surface area for nourishment
What are the layers of the epidermis?
Stratum corneum, Stratum lucid (in thick skin), stratum granulosum, stratum spinosum, stratum basale
What are the cells of the stratum corneum?
Dead dried out hard cells without nuclei which can be completely removed by strip-taping
What are the cells of the stratum granulosum?
Contain granules that promote dehydration of the cell, cross linking of keratin fibres. Waxy material is secreted into the intercellular spaces
What are the cells of the stratum spinosum?
Intercellular bridges called desmosomes link the cells together. The cells become increasingly flattened as they move upward
What are the cells of the stratum basal?
Columnar (tall) regenerative cells. As the basal cell divides and differentiates, a daughter cell migrates upwards to replenish layers above
What are simple epithelia?
Single layers of cells
What are the types of epithelia?
Squamous, cuboidal and columnar
What are stratified epithelia?
Multiple layers of cells
What type of epithelial cell is the epidermis?
Stratified squamous
What skin layers shed?
The epidermis and not the dermis
What protein fibres are in the dermis?
Collagen and elastin
Where is thick skin found?
Palms of hands and soles of feet
What are the characteristics of thick skin?
No hair, extra epidermal layer (stratum lucidum) for extra rigidity, stratum corneum much thicker but other layers the same
What happens to the epidermis in ageing?
Thinner and drier (less sebum and fewer active follicles)
What happens to the dermis in ageing?
Thinner (sagging and wrinkling), reduced collagen
What happens to skin repair in ageing?
Slower
What happens to cooling in ageing?
Impaired (less sweat/sweat glands)
What happens to pigmentation in ageing?
Less. Pale skin, grey hair
What is the relationship between smoking and skin ageing?
Smoking increases skin ageing
What does smoking do?
“reactive oxygen” damages collagen and elastin. vasoconstriction - nicotine increases vasopressin
