Integumentary System - August 2024 PDF

August 2024 The Integumentary System f) Stem cells divide and give rise to Layers of the Integumentary System keratinocytes that migrate toward the surface 1. Epidermis - Str...

August 2024 The Integumentary System f) Stem cells divide and give rise to Layers of the Integumentary System keratinocytes that migrate toward the surface 1. Epidermis - Stratified squamous epithelium and replace lost epidermal cells 2. Dermis - Deeper connective tissue 2. STRATUM SPINOSUM Hypodermis – connective tissue below Thickest stratum in most places except in dermis; not part of the skin palms and soles (stratum corneum) Deepest cells continue dividing but cease to EPIDERMIS do so as they’re pushed farther Keratinized stratified squamous epithelium Keratinocytes bound together by tight Surface consists of dead cells junctions which make an essential Keratin –tough fibrous protein contribution to water retention by the skin lacks blood vessels Desmosomes attach keratinocytes together Depends on diffusion of nutrients from which accounts for the toughness of underlying connective tissue epidermis Sparse nerve endings bridge from cell to cell giving each cell a spiny appearance. Cells of the Epidermis 3. STRATUM GRANULOSUM 1. KERATINOCYTES a. 3-5 layers of flat keratinocytes – more in thick a. Great majority of epidermal cells skin b. Synthesizes keratin b. Keratinocytes contain coarse, dark staining 2. MELANOCYTES KERATOHYALIN GRANULES a. At stratum basale 4. STRATUM LUCIDUM b. Synthesize brown to black pigment MELANIN a. Thin zone seen only in thick skin c. Continually shed melanin containing b. Densely packed keratinocytes with clear fragments called MELANOSOMES from their protein called ELEIDIN tips c. No nuclei/ organelles d. These dark granules shield the DNA from d. Pale, featureless appearance with indistinct ultraviolet rays cell boundaries 3. MERKEL CELLS 5. STRATUM CORNEUM a. associated with sensory nerve endings a. layers of dead, scaly, keratinized cells that 4. LANGERHANS CELLS form a durable surface layer a. macrophage-like dendritic cells b. Resistant to abrasion, penetration, and water loss Layers of the Epidermis 1. STRATUM BASALE/GERMINATIVUM DERMIS a) Deepest layer Fiber types: collagen, elastic, reticular b) Single row of cells attached to dermis Well-supplied with blood vessels, cutaneous c) Youngest cells glands, and nerve endings d) Deepest layer thermoregulation e) Melanocytes, tactile cells, stem cells Hair follicles and nail roots skeletal muscles attach to dermal collagen fibers Gen Ana 1 Lab - Prelim  August 2024 Dermal papillae c. Hair matrix – mitotically active cells above Upward waves of fingerlike extensions the papilla; growth center; all cells higher up between epidermis and dermis are dead Raised areas Epidermal ridges Microscopic Parts: Downward epidermal waves between the a. Medulla – core of loosely arranged cells and air papillae spaces; most prominent in thick hairs e.g. FRICTION RIDGES – wavy boundary on eyebrows; narrower in hairs of medium thickness fingertips producing fingerprints and absent from thinnest hairs of scalp and elsewhere Layers of Dermis b. Cortex – most of the bulk of hair; several layers A. Papillary Layer – thin zone of areolar tissue in of keratinized cells and near the dermal papillae c. Cuticle – multiple layers of thin, scaly cells that Loosely organized tissue which allows for overlap each other like roof shingles with their mobility of leukocytes and other defenses against free edges directed upward; keep hairs separated organisms introduced through breaks in the so they don’t become matted together epidermis; rich in small blood vessels b. Reticular layer Hair receptors – nerve fibers that entwine each Dense irregular connective tissue follicle and respond to hair movements Fibrous Arrector muscle – PILOMOTOR MUSCLE/ Thicker bundles of collagen ARRECTOR PILI; smooth muscle cells ext from Less ground substance dermal collagen fibers to CT root sheath of the follicle in response to cold, fear, touch, or other HYPODERMIS stimuli Beneath the skin Also known as subcutaneous tissue/ 2. NAILS superficial fascia nail plate – hard part, includes free edge More areolar and adipose tissue a. nail body – visible attached part Pads the body and binds skin to underlying b. nail root – extends proximally under the tissues overlying skin Drugs can be introduced here by injection as c. nail fold – surrounding skin that rises above it is highly vascular and absorbs drugs quickly the nail d. nail bed – skin underlying the nail plate SKIN APPENDAGES a. hyponychium – epidermis 1. HAIR e. nail matrix – thickening of stratum basale at A. Shaft – portion of hair above the skin the proximal end of the nail B. Root – beneath the surface a. Penetrates deeply into dermis/ hypodermis Cutaneous Glands and ends with a dilation called bulb 1. Apocrine sweat glands b. Dermal papilla – vascular CT where bulb in groin, anal region, axilla, and areola, beard grows around; provides hair with its sole area source of nutrition Gen Ana 1 Lab - Prelim  August 2024 use exocytosis mode of secretion (same as ∙ Keeps eardrum pliable, waterproofs the eccrine) canal, kills bacteria, coats guard hairs making thicker, milkier due to presence of more fatty them sticky and more effective in blocking acids foreign particles from entering the canal scent glands respond to stress and sexual stimulation 5. Mammary Gland not active until puberty ∙ Breasts are present in males and females secrete sex pheromones ∙ Mammary glands are the milk-producing exert subtle effects on sexual behavior glands that develop within the female breast and physiology of other people during pregnancy and lactation hair serves to retain the aromatic ∙ Modified apocrine glands secretion and regulate its rate of ∙ In most mammals, 2 rows of mammary glands evaporation from the skin form along the mammary ridges or milk lines 2. Eccrine sweat glands END a. widely distributed over entire body b. abundant on palms, soles, forehead c. cools body d. leads to a sweat pore myoepithelial cells - at deep end of apocrine/ eccrine glands - contractile properties similar to smooth muscle ∙ perspiration – 99% water and has a pH ranging from 4-6 ∙ acid mantle – inhibits bacterial growth in skin 3. Sebaceous Glands Produce an oily secretion called sebum Opens into hair follicle; some directly onto skin surface Holocrine glands Sebum – keeps skin and hair from being dry, brittle and cracked 4. Ceruminous Glands ∙ Modified apocrine glands ∙ External ear canal ∙ Yellow, waxy secretion combined with sebum and dead epidermal cells => earwax/ cerumen ∙ Lead to hair follicles on skin surface of ear Gen Ana 1 Lab - Prelim