Chapter 5 Part 1 Flashcards
Contents of the Integumentary System
-Skin, Hair, Nails, Sweat Glands, Sebaceous (oil) glands.
Main Regions of Skin
- Epidermis) Top layer of skin. consists of epithelial tissue and is made of dead keratinized cells.
- Dermis) Underlies Epidermis. made of areolar and dense irregular tissue.
- Hypodermis) (Superficial Fascia) anchors skin to underlying muscles. (not part of skin but shares some function)
Types of Epidermis cells
-Keratinocytes, Melanocytes, Dendritic (langerhans) cells, and Tactile (Merkel) cells.
Keratinocytes
- Produce Fibrous Keratin. Gives epidermis its protective properties. Most cells of epidermis are keratinocytes
- Connected by desmosomes
- Arise from the stratum basale.
- Thickened areas of the epidermis are called callus’
Melanocytes
- Spider shaped cells that synthesize melanin. Found in deeper layers of epidermis.
- Melanin is packaged into granules called melanosomes.
- Melanosomes accumulate toward the apical surface of epidermal cells to protect the DNA from UV damage.
Dendritic (Langerhans) cells
-Star-shaped macrophages that patrol deep epidermis. Key in the immune system
Tactile (Merkel) cells.
- Sensory receptors that sense touch.
- Each cell is associated with a dislike neuron ending called a merkel disc
5 Layers of the Epidermis (bottom to top)
1) Stratum Basale (bottom)
2) Stratum Spinosum
3) Stratum Granulosum
4) Stratum Lucidum (only found in thick skin)
5) Stratum Corneum
Stratum Basale
- Deepest epidermal layer (basal layer). Attached to the dermis
- Made of a layer of stem cells that continuously make keratinocytes. When the cell divides one daughter cell becomes keratinocyte and one remains in Stratum Basale.
- Actively involved in the process of Mitosis. Because of this it is also called the stratum Germinativum.
Stratum Spinosum
- Prickly layer. Several layers of keratinocytes unified by desmosomes.
- Cells contain pre-keratin which looks like spines coming out of the cell. (giving it the nickname prickly layer)
- Dendritic cells are also present in this layer. More abundant in this layer than any other layer.
Stratum Granulosum
- Thin layer, one to 5 cells thick.
- Process of keratinization (cells fill with keratin) begins here. cell appearance flattens and nuclei dissolve.
- Hold two types of granules
1) Keratohyalin Granules) Help form keratin in the upper layer
2) Lamellar granules) Water-resistant glycolipid that slows water loss. - Cells above this layer die because they are too far from the dermal capillaries to diffuse nutrients and because lamellar granules stop nutrients.
Stratum Lucidum
-Only found in thick skin. Layer of clear keratinocytes.
Stratum Corneum
- 20-30 layers of dead, flat, anucleated keratinocytes. account for 3/4 of the thickness of the epidermis.
- Protect deeper cells, against water loss, and acts as a barrier.
Dermis
- Strong, flexible connective tissue found below the epidermis.
- Made of Fibroblasts, Macrophages, and occasionally white blood cells and mast cells (Immune Response). Structures include epidermal hair follicles and oil/sweat glands.
- Contains nerve, lymph, and blood vessels.
Two Layers of the Dermis
- Palpilary (areolar connective) layer
- Reticular (Dense irregular connective) layer
Papillary Layer.
- Top layer of the dermis. Made of areolar connective tissue, collagen and elastic fibers, and blood vessels.
- Looseness of this connective tissue allows phagocytes to wander freely.
Dermal Papillae
- Dermal Ridges that occur in thick skin following the pattern of the underlying papillary layer (dermis).
- Increase friction between objects that you hold and your hands.
- Each is unique to us (fingerprint). Small sweat pores on our fingertips leave fingerprints.
Reticular Layer.
- Accounts for 80% of dermal thickness. Made of dense irregular connective tissue.
- Also contain elastic fibers which provide stretch and recoil properties and collagen fibers which provide strength and bind water.
- Cutaneous Plexus) network of blood vessels that runs between reticular layer and the dermis.
Cleavage lines
- Lines in Reticular Layer of the dermis caused by many collagen fibers running parallel to the skin. Invisible on the surface.
- Important to surgeons because cuts along these lines heal better.
Flexure Lines
- Dermal Folds of the Reticular layer which are near joints.
- Ex: Palm lines.
Stretch Marks
-Extreme stretching of the skin cause dermal tears which appear as white scars. tears are called Striae
Blisters
-Fluid filled pockets between the epidermal and dermal layers due to trauma.
Skin Color
- Three Pigments contribute to skin color
Melanin) (see melanocyte) can be reddish yellow or brownish black. Skin color differences are due to differences in melanin.
- Carotene) Yellow/orange pigment most obvious in palms and soles. Accumulates in stratum corneum and hypodermis. Can be converted to vitamin A
- Hemoglobin) Pinkish hue due to this pigment.