BIOL 252 1st Edition Lecture 8 Outline of Last Lecture I. EquilibriumII. VisionIII. Sensory Transduction in the RetinaIV. Generating Optic Nerve SignalV. How we Have Different SensitivitiesVI. Color VisionVII. Visual Projection PathwayOutline of Current LectureI. The Skin: Its Structure and FunctionII. The EpidermisIII. The DermisIV. HypodermisV. Skin ColorationCurrent LectureI. The Skin: Its Structure and Functiona. Biological harmi. Keeps microbes and pathogens outb. Chemical harmi. Waterproofing – helps us to retain water or absorbing too muchc. Physical harmi. Abrasionsd. Other functions:i. Vitamin D synthesisii. Sensory reception1. Pain, heat, movement, pressure, light touchiii. Thermoregulation1. Involves all 3 layers of the skiniv. Communication1. Facial muscles, skin color changesII. The Epidermisa. Epidermal cell typesi. Keratinocytes and stem cells (make keratin)ii. MelanocytesThese 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.1. Protect against UV light (causes DNA mutations)iii. Tactile cells1. Sensory receptor for touchiv. Dendritic cells1. Fight off microbes and bacteria for the immune system2. First line of defense for body after the skin (so 2nd line of defense)3. Signals to the rest of the immune systemb. Keratinized stratified squamous epitheliumi. Desmosomes: strong mechanical linkagesii. Stratum basale: bottom-most leveliii. Stratum spinosum:1. Spiny because beginning to dehydrateiv. Stratum granulosum: 1. Beginning process of cells dying – start to become functional2. Become dehydrated, lose organelles3. By the time they come to stratum corneum, cells DEADv. Stratum corneum:1. Cells dead, continually exfoliatevi. Poll Everywhere:1. What is cancer? Uncontrolled cell division2. Which cells are least likely to become a skin cancer?a. Stratum granulosumb. Other three types have naturally dividing cellsc. Pathology: Skin Disordersi. Cancers of the epidermisii. 1. Basal Cell Carcinoma1. Stratum basale 2. Most common3. Least dangerous4. Carcinoma = epithelial canceriii. 2. Squamous cell carcinoma1. Arises w/in stratum spinosum2. Metastasizes (leave tissue of origin and can travel to other places) to lymph nodes and can be lethaliv. 3. Malignant melanoma1. Most readily metastasizing2. Rare but deadly3. Metastasizes readily and is fatala. Can have it all over your bodyIII. The Dermisa. Superficial: Papillary layeri. Areolar connective tissueii. Forms papillae, dense w/ nerve endings and capillariesb. Deep: reticular layeri. Dense irregular connective tissueii. Contains larger blood vesselsiii. Some adipocytesiv. Comprises most of dermisv. Leather = reticular layerc. Why do we have fingerprints?i. To gripIV. Hypodermisa. Last layer of the skinb. Fat layer at the bottomc. Structure: primarily adipose; rich in blood vessels, nervesd. Functions: fat (energy) storage, thermal insulation, communicatione. Health reflected by amount of fat that you have V. Skin Colorationa. Ingesting of silver nitrate (antibacterial properties)i. Man turns blueb. Which molecule does not contribute to the normal color of skin?i. Hemoglobin – ranges from red to purplish/blue (highly oxygenated = red; purple/blue = deoxygenated) 1. Abnormal colors in skina. Cyanosis: poorly oxygenated hemoglobinb. Pallor: yellow/green/pale skin resulting from poor blood supplyc. Erythema: any abnormal reddening of skin (overheating, stress, burns, rashes)d. Jaundice: yellowing due to buildup of bilirubine. Hematoma: bruise – mass of clotted bloodii. Melanin – provides pigment from yellowish to brown to black (part of stratum basale)1. Produced by melanocytes, distributes on external face of keratinocytes; breaks down more rapidly in lighter skin tones2. Abnormal colors in skina. Albinism = lack of melanin; genetic3. Lots of melanin where strong UV light is (equator)iii. Keratin – waterproofs skin, gives abrasion resistanceiv. Carotene – normal pigment found in plants; yellowish-orangish1. Carotenemia: carotene is normal in small amounts but may accumulate in stratum