These 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. Lecture 8 Outline of Last Lecture I. Equilibrium II. Vision III. Sensory Transduction in the Retina IV. Generating Optic Nerve Signal V. How we Have Different Sensitivities VI. Color Vision VII. Visual Projection Pathway Outline of Current Lecture I. The Skin: Its Structure and Function II. The Epidermis III. The Dermis IV. Hypodermis V. Skin Coloration Current Lecture I. The Skin: Its Structure and Function a. Biological harm i. Keeps microbes and pathogens out b. Chemical harm i. Waterproofing – helps us to retain water or absorbing too much c. Physical harm i. Abrasions d. Other functions: i. Vitamin D synthesis ii. Sensory reception 1. Pain, heat, movement, pressure, light touch iii. Thermoregulation 1. Involves all 3 layers of the skin iv. Communication 1. Facial muscles, skin color changes II. The Epidermis a. Epidermal cell types i. Keratinocytes and stem cells (make keratin) BIOL 252 1st Editionii. Melanocytes 1. Protect against UV light (causes DNA mutations) iii. Tactile cells 1. Sensory receptor for touch iv. Dendritic cells 1. Fight off microbes and bacteria for the immune system 2. First line of defense for body after the skin (so 2nd line of defense) 3. Signals to the rest of the immune system b. Keratinized stratified squamous epithelium i. Desmosomes: strong mechanical linkages ii. Stratum basale: bottom-most level iii. Stratum spinosum: 1. Spiny because beginning to dehydrate iv. Stratum granulosum: 1. Beginning process of cells dying – start to become functional 2. Become dehydrated, lose organelles 3. By the time they come to stratum corneum, cells DEAD v. Stratum corneum: 1. Cells dead, continually exfoliate vi. Poll Everywhere: 1. What is cancer? Uncontrolled cell division 2. Which cells are least likely to become a skin cancer? a. Stratum granulosum b. Other three types have naturally dividing cells c. Pathology: Skin Disorders i. Cancers of the epidermis ii. 1. Basal Cell Carcinoma 1. Stratum basale 2. Most common 3. Least dangerous 4. Carcinoma = epithelial cancer iii. 2. Squamous cell carcinoma 1. Arises w/in stratum spinosum 2. Metastasizes (leave tissue of origin and can travel to other places) to lymph nodes and can be lethal iv. 3. Malignant melanoma 1. Most readily metastasizing 2. Rare but deadly3. Metastasizes readily and is fatal a. Can have it all over your body III. The Dermis a. Superficial: Papillary layer i. Areolar connective tissue ii. Forms papillae, dense w/ nerve endings and capillaries b. Deep: reticular layer i. Dense irregular connective tissue ii. Contains larger blood vessels iii. Some adipocytes iv. Comprises most of dermis v. Leather = reticular layer c. Why do we have fingerprints? i. To grip IV. Hypodermis a. Last layer of the skin b. Fat layer at the bottom c. Structure: primarily adipose; rich in blood vessels, nerves d. Functions: fat (energy) storage, thermal insulation, communication e. Health reflected by amount of fat that you have V. Skin Coloration a. Ingesting of silver nitrate (antibacterial properties) i. Man turns blue b. 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 skin a. Cyanosis: poorly oxygenated hemoglobin b. Pallor: yellow/green/pale skin resulting from poor blood supply c. Erythema: any abnormal reddening of skin (overheating, stress, burns, rashes) d. Jaundice: yellowing due to buildup of bilirubin e. Hematoma: bruise – mass of clotted blood ii. 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 skin a. Albinism = lack of melanin; genetic 3. Lots of melanin where strong UV light is (equator) iii. Keratin – waterproofs skin, gives abrasion resistance iv. Carotene – normal pigment found in plants; yellowish-orangish 1. Carotenemia: carotene is normal in small amounts but may accumulate in stratum