Ch. 5 The Integumentary System (Epidermal Strata)

Stratum corneum

(Epidermis) hornlike; most superficial layer of epidermis; 20-30 layers of dead, flattened, scaly, anucleate (lack a nucleus), interlocking keratinized cells called corneocytes. -Dead cells are tightly packed together. -presents a thickened surface unsuitable for the growth of many microorganisms. -constantly being regenerated

Stratum spinosum

(Epidermis) several layers of keratinocytes attached to neighbors by desmosomes; epidermal dendritic cells present

No specific layers

(Subcutaneous layer) not considered part of the integument; deep to dermis; composed of areolar connective tissue and adipose connective tissue.

Keratinization

-Process by which the keratinocytes fill up with the protein keratin. -Not complete until the cells reach the more superficial epidermal layers. -A fully keratinized cell is dead (because it has neither a nucleus nor organelles), but it is strong because it contains keratin.

Keratinocyes

-most abundant cell type in the epidermis and occur throughout all epidermal strata. -Fibrous structural proteins that are both tough and insoluble. -The keratins found in epidermal cells of the skin are called cytokeratins, their structure in these cells givens skin its strength and make the epidermis almost waterproof.

Stratum basale

(Epidermis) deepest, single layer of cuboidal to low columnar cells in tight contact with basement membrane; mitosis occurs here; contains keratinocytes, melanocytes, and tactile cells

Reticular layer

(Dermis) deeper layer of dermis; dense irregular connective tissue surrounding blood vessels, hair follicles, nerves, sweat glands, and sebaceous glands. -Large bundles of collagen fiber project in all directions (meshwork or network of collagen fibers).

Papillary layer

(Dermis) more superficial layer of dermis; composed of areolar connective tissue; forms dermal papillae -Each dermal papillary that supply nutrients to the cells of epidermis also houses sensory receptors.

Stratum lucidum

(Epidermis) 2-3 layers of anucleate, dead cells; seen only in thick skin (palms of hands, soles of feet) -The keratinocytes within this layer are flattened and filled with the protein eleiden., an intermediate product in the process of keratin maturation.

Stratum granulosum

(Epidermis) 3-5 layers of keratinocytes with distinct granules in the cytoplasm: keratinization begins in this layer. Two types of granules: 1. Keratohyalin granules-involved in keratinization process. 2. Lamellar granules- fuse with the plasma member and extrude their contents (lipids primarily) into the extracellular space.

Melanocytes

produce and store the pigment is response to UV light exposure.

Tactile cells

sensitive to touch, and when compressed, they release chemicals that stimulate sensory nerve endings, providing information about objects touching the skin.

increase the area of contact between the epidermis and dermis and connect these layers

Epidermal ridges dermal papillae _________

2 weeks

Migration of the keratinocyte to the stratum cornium from stratum basale occurs during the first ______ of the keratinocyte's life.