Transcript Slide 1
November 5, 2014 Objective: To describe the structure and function of the hair and nails To make a model of the skin Journal: What are two accessory organs that can be found in the dermis? Hair Hair Functions - Helps regulate body temperature - Helps detect things on your skin - Eyelashes and nose hairs are for protection Hair Anatomy Made up of dead keratinized epithelial cells Hair Shaft: the part that protrudes above the skin Hair Follicle: Tube-like hole in the skin from which the hair develops Hair Anatomy Continued… Hair Bulb: Expanded base of the root Hair Papilla: when the dermis of the skin projects into the base of the hair to supply it with nutrients from blood vessels Hair Anatomy Continued… Arrector pili muscle: contract to allow hairs to stand up straight Two Stages of Hair Growth Growth Stage: Stem cells reproduce and differentiate to form epithelial cells, which are then keratinized and die The hair grows longer as cells are added to the base Resting Stage: No hair growth Hair is held within the hair follicle Duration of each cycle depends on the hair. Hair Lifespan Eyelashes lasts around 3 to 4 months Hair on your head lasts about 3 to 4 years It is normal to lose about 100 hairs a day. Baldness occurs when the hair follicles are lost due to genetic factors or testosterone ** Ingested substances can become part of a hair’s composition, so the longer the length of the hair the longer the record of what was consumed by the individual. Hair Color and Style Dependent on the amount and type of melanin you produce in the hair bulb The more melanin, the darker the hair White hair occurs in the absence of melanin Red hair occurs when the melanin is altered and has iron it in Flat hair shafts = curly hair Round hair shafts = straight hair Nails Nails Nail Structure Nails are thin plates made up of layers of keratinized stratum corneum cells. Nail body: visible part of the nail Nail root: part of the nail covered by skin Nail fold: the fold of skin that holds the nail in place Nail Structure Continued… Cuticle: stratum corneum cells from the nail fold that extends on to the nail body Nail Bed and Matrix: Stratum basale that produce the cells that make up the nail body Lunula: crescent shaped part of the nail matrix Nail Growth Nails grow continuously Production of cells within the nail matrix results in growth of the nail What your nails can tell your about your health Nail Shape and Texture: Horizontal ridges - stress Vertical ridges - arthritis Vertical grooves - kidney disorders, aging, and iron deficiency Markings: Blue nail beds – not enough oxygen in the blood Small white patches – zinc or calcium deficiency or parasites Receded lunulae - poor circulation, shallow breathing habits, or thyroid problems Large lunulae (more than 25% of the thumb nail) - high blood pressure.