What are the functions of the skin and hypodermis?
BEPPS
- Body temperature regulation: capillary network and sweat glands regulate heat loss
- Excretion: urea, salts, and sweat glands regulate heat loss
- Protection: cushions organs and protects from bumps, chemicals, water loss, and UV radiation
- Production of vitamin D: epidermal cells use UV radiation to synthesize vitamin D
- Sensory reception: contains sense organs associated with nerve endings
What type of tissue is the epidermis made of?
stratified squamous epithelium
Name the layers of the epidermis starting from the bottom to top most
- stratum basale
- stratum spinosum
- stratum granulosum
- stratum lucidum
- stratum corneum
Describe the stratum basale: What is the stratum basale located? What happens in this area? What cells are in stratum basale? What do they do?
- deepest layer of epidermis; attached to underlying dermis
- cells actively divide
- tactile epithelial cells: associated with sensory nerve endings
- melanocytes: secrete pigment melanin
Describe the stratum spinosum: What is it made of? What cells are here and what do they do?
- spiny appearance
- thick bundles of intermediate filaments (resist tension; contain protein pre-keratin)
- dendritic cells (keratinocyte): type of macrophage; function in immune system
Describe stratum granulosum: What does it consist of? Where keratinocytes are found here?
- few layers of keratinocytes
- keratohyaline granules: help form keratin
- lamellar granules: contain waterproofing glycolipid
What layer of the epidermis is ONLY found in thick skin? What areas of the body can you find thick skin?
- stratum lucidum
- location: palms, soles
Describe the stratum corneum. What is this layers function?
- thickened plasma membrane + thick layer of dead keratinocytes (no nuclei)
- protects skin against abrasion and penetration
What are the four main cells types found in the epidermis? Describe their location and main function
- keratinocytes: stratum spinosum; produce keratin (fibrous protein)
- dendritic cells: stratum spinosum; part of immune system; macrophage-like
- melanocytes: basal layer; manufacture and secrete pigment melanin
- tactile epithelial cells: basal layer; attached to sensory receptors
Name the cell that is the most abundant in the epidermis, arises from the deepest layer of the epidermis, produces a tough fibrous protein, antibiotics, and enzymes, and is dead at the skin’s surface
keratinocytes
What layer of the skin contains strong, flexible connective tissue and is richly supplied with blood vessels and nerves?
dermis
Name they two layers of the dermis
- papillary dermis (includes dermal papillae)
- reticular dermis (80% of thickness of dermis, rich nerve supply)
What is the function of dermal papillae?
increases surface area for gas, nutrient, waste exchange
What do dermal papillae lie on?
dermal ridges
What are epidermal ridges? What do they do?
- are elevations of dermal ridges
- form fingerprints and increase the gripping ability of hands and feet
What tissue is the reticular dermis made of?
dense irregular connective tissue
What can be found in dense irregular connective tissue?
- cleavage lines: separation between collagen fibers
- collagen fibers give skin strength
What are flexure lines? What specific layer of the skin is this found in?
- deep creases in palms, wrists, soles, fingers, and toes
- reticular dermis
Describe the hypodermis. What tissue is it made of and what are its functions?
- areolar + adipose CT
- anchors skin to underlying structures
- helps insulate body
What sensation is associated with free nerve endings?
light touch; hot; cold; pain
What sensation is associated with Merkel’s discs?
sustained touch and indented depth (indentation)
What sensation is associated with Ruffini corpuscles?
skin stretch
What sensation is associated with Meissner’s corpuscles?
changes in texture; slow vibrations
What sensation is associated with Pacinian corpuscle?
deep pressure, fast vibrations
