NS 3410 1st Edition Lecture 6Outline of Last LectureI. Quiz II. TA IntroductionsIII. Tissue TypesIV. Epithelial Tissue CharacteristicsOutline of Current LectureI. Overview of Integumentary SystemII. Epithelial Tissue III. Skin Regions IV. Skin ColorCurrent LectureI. Overview of Integumentary System- Skin has a surface area of about 20 sq. ft.- Skin weighs about 4-5 kg- Skin is the largest organ in the body- Americans spend about $12.4 billion dollars annually on cosmetics- A 2002 study found that 61% of college students had used a tanning lamp- Skin ranges in thickness from .5 mm to 5 mm- Skin has a microbiome- Integumentary system is comprised of skin and derivatives (sweat, oil glands, hair and nails)- Functions of Integumentary System-Protection: chemical, physical, and mechanical barrierThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.-Body temperature regulation: If hot, vessels dilate to cool and if cold, vessels constrict to maintain core temp-Cutaneous sensation: exoreceptors sense touch and painII. Epithelial Tissue- Characteristics-Specialized contacts: desmosomes, tight junctions and gap junctions-Polarity: basal and apical sides-Avascular (no blood vessels) but innervated (supplied by nerve fibers)-Regenerative: rapidly replaces lost cells by cell division-Classification: each tissue type given 2 names. First name denotes the number of cell layers present and the second name denotes the shape of its cells- Classification1. Number of cell layers present-Simple: 1 layer-Stratified: 2 layers-Pseudostratified: looks like 2 or more layers but it only has 12. Shape of the cells-Squamous: flat or scale like-Cuboidal: cube like-Columnar: column shaped-Transitional: shape changes from flat to cuboidal and back (in bladder)3. Nucleus-Shape: flat or rounded-Where located: basal part of cell or center- Squamous: flattened and scale like, nucleus flat. Needed for diffusion, osmosis and filtration. - Cuboidal: boxlike, as tall as wide, nucleus round. Needed for secretion and absorption- Columnar: tall and column like, near base of cell. Needed for secretion and absorption. Has microvilli at apical surface- Found in various locations depending on type of epitheliumIII. Skin Regions- Epidermis- outermost superficial region-Composed of keratinized stratified squamous epithelium, consisting of four distinct cell types and either four or five layers-Cell types include keratinocytes, melanocytes, Merkel cells and Langerhans’ cells-Outer portion of the skin is exposed to the external environment and functions in protection - Dermis- middle region- Hypodermis- deepest region; not really part of the skin but shares skins protective functions; consists mainly of adipose tissue- Keratinocytes produce the fibrous protein keratin which provides protective function. They are connected tightly to one another via desmosomes- Melanocytes are spider shaped cells that synthesize melanin, found in deepest layer of epidermis. Melanin accumulates in vesicles called melanosomesIV. Skin Color- Three primary pigments contribute to skin color-Melanin: yellow to reddish-brown to black-Carotene: yellow to orange pigment-Hemoglobin: reddish pigment- Jaundice: yellowish tint to skin. Liver can’t excrete bile so yellow pigment (bilirubin) accumulates in body fluids.- Iron overload: buildup of iron stores can turn skin a bronzed color- Vitiligo: lose your