BIO 240 1st Edition Lecture 8 Outline of Last Lecture E Specialized Connective Tissue i Cartilage ii Bone iii Blood I Membranes Outline of Current Lecture I Membranes A Types B Cutaneous membrane C Regions of the skin D Details of the epidermis E Hair F Glands Current Lecture I Membranes The smallest organs by complexity because they re only made up of two tissue types A 4 types of membranes in the body 1 Serous membranes Secretes serous fluids to reduce friction a Pericardium Membrane surrounding the heart b Pleura Membrane surrounding the lungs c Peritoneum Lines the abdominopelvic cavity 2 Mucous membrane Secretes mucus and lines structures that open to the outside 3 Synovial membrane Secretes synovial fluid and lines synovial joints 4 Cutaneous membrane Skin B Cutaneous Membrane 1 Forms the integumentary system an organ system contains 2 or more organs 2 Epidermal derivatives are the other things embedded in skin the epidermal derivatives plus the skin equal the integumentary system a Examples of epidermal derivatives hair fingernails exocrine glands horns claws 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 b The epidermis makes these derivatives and then pushes them down into the dermis 3 Characteristics of Cutaneous Membrane a Largest organ in the body by volume making up about 7 of your total body weight b Serves as a protective barrier from bacteria viruses UV and water c Synthesizes vitamin D i Too many UV rays are bad but some is necessary to activate the synthesis of vitamin D ii Vitamin D is necessary for the absorption of calcium d Secretes nitrogenous waste through sweat glands e Has millions of sensory inputs C Regions of the skin 2 1 1 Epidermis Composed of keratinized stratified squamous epithelial tissue consisting of 5 layers in some places of the body thick skin and 4 layers of the body in most places thin skin 2 Dermis Composed of connective tissue in 2 layers 3 Hypodermis Layer below the dermis that is entirely adipose tissue Sometimes called superficial fascia D Details of the epidermis 1 Epidermis layers from deepest to most superficial a Stratum Basale Typically simple cuboidal cells that are mitogenic Reproduces cells and pushes them upwards Maintain their cuboidal shape because can receive nutrients by diffusion from the capillaries below b Stratum Spinosum Cells from the basale layer that start to shrink because of a lack of nutrients They are huge holders of keratin c Stratum Granulosum Little granular balls of keratin Cells are often referred to a keratinocytes because they have so much keratin Look spotted or grainy d Stratum Lucidum This is the extra layer that is found in only thick skin on the palms of the hands and soles of the feet It is a thick layer of cells that gives thick skin its rough texture e Stratum Corneum Flattened keratinocytes This region can be multiple layers thick 2 Cells of the epidermis a Keratinocytes make up 90 of all the cell layers of the epidermis b Melanocytes Cells of the epidermis only found in the stratum basale layer About 20 of the cells in the stratum basale are melanocytes There is the same number of melanocytes in the stratum basale across all races skin tone is dependent on the amount of melanin produced not the number of melanocytes These cells give us our skin pigment by producing melanin which gives us all colors from red to brown to black Melanin shields us from UV and is what gives us our skin tone c Some of the cells migrate down from the stratum basale to form the epidermal derivatives E Hair 1 Cuticle Is the hardest outside layer of hair that is solid keratin 2 Cortex Hardened keratin injected with melanin This is the section of hair that contributes to hair color 3 Medulla Air in the hollow center of each hair follicle This air is easy to heat up and can warm up to help with insulation 4 Arrector pili muscle This is not an epidermal derivative it is a muscle It is a small muscle attached to the base of the hair follicle It contracts when we are cold making the hair stand straight up and giving us goose bumps 5 Papilla The cells at the base of the follicle They are mitogenic and contribute to the growth of the hair 6 Texture of hair a Straight There is a round diameter to the shaft of the hair b Curly There is an oval diameter to the shaft of the hair The more curly it is the more exaggerated the oval is 7 Color of hair a Black brown There is mostly eumelanin deposited in the cortex The more eumelanin the darker b Red There is mostly pheomelanin c Blonde There is most pheomelanin but with some eumelanin d Gray There is no melanin the melanocytes in the cortex have stopped producing melanin so when light hits the hair the air in the medulla is reflected F Glands 1 Sebaceous gland Oil glands Present everywhere except on the palms of the hands and soles of the feet 2 Sweat glands Present everywhere 3 Ceruminous glands In your ear wax Specialized form of sebaceous gland 4 Mammary glands Produce milk There are two in humans and more in most other mammals