Lab 4 Notes: The Integument

Important Terms & Functions

Layers of the Epidermis

  • epidermisepidermis: top layer of the skin; epithelium of the integument, keratinized squamous epithelium, avascular & acquires nutrients from dermis
    • %%germinative zone%%:: deepest layer of the epidermis; where cells engage in mitosis & renew old cells
    • @@stratum basale@@ - deepest epidermal layer; ranges from cuboidal to low columnar
      • ^^keratinocytes^^ - most abundant cell type; produces keratin & gives strength and waterproofing
      • ^^melanocytes^^ - long, branching processes; produce & store melanin, give pigment to skin and get darker with more exposure to UV light
      • ^^tactile cells^^ - (Merkel cells) sensitive to touch & provide sensory info
    • @@stratum spinosum@@ - (spiny layer) on top of stratum basale and underneath stratum granulosum
    • @@stratum granulosum@@
    • %%keratinization zone:%% middle layer of the epidermis; can create harder, tougher cells that produce hair and horns
    • @@stratum granulosum@@ - (granular layer) lies above stratum spinosum but below stratum corneum; helps form waterproof barrier that functions to prevent fluid loss from the body
    • %%cornification zone%%: superficial layer of the epidermis;
    • @@stratum lucidum@@ - (clear layer) found in thick skin (hands or soles of feet); thni layer of dead skin cells
    • @@stratum corneum@@ - (horny layer) most superficial layer of the epidermis; consists of 20-30 layers of dead, interlocking keratinized cells
    • ^^desquamation^^ - peeling of the skin, unintended damage to and loss of the upper layer of skin
  • dermisdermis: middle layer of the skin and deep to epidermis; consists of two types of connective tissue - areolar and connective; vascular, sweat glands, sebaceous glands, and nerve endings
    • @@papillary layer@@ - superficial region of dermis;
    • %%dermal papillae%% - projections of the dermis that interlock with epidermal ridges
    • @@reticular layer@@ - forms the deeper portion of the dermis; consists of primarily dense irregular CT with large bundles of collagen fibers
  • hypodermishypodermis: (subcutaneous layer) deepest layer of the skin, stores energy and connects dermis later to muscle and bone
    • @@adipocytes@@ - fat cells
    • @@breast tissue@@ - composed of collagen fiber matrix and adipose tissue; lays superficial to the muscle and bone of the thorax
    • ^^lobes^^ - different subcompartments of the breast
    • ^^septa^^ - bands/highways of collagen fibers
    • ^^alveoli^^ - in breast, produces milk
    • ^^lactiferous ducts^^ - converge & form a branched system connecting the nipple to the lobules of the mammary gland

Glands of the Skin

  • sudoriferous(sweatglands)sudoriferous (sweat glands): small tubular structures of the skin that produce sweat
    • @@merocrine (eccrine) glands@@ - package their secretions in structures called secretory vesicles and release secretion via exocytosis
    • @@apocrine glands@@ - glands that accumulate their secretory products within apical portion of cytoplasm
    • @@ceruminous glands@@ - true apocrine glands, secretion mixes with both sebum and exfoliated keratinocytes for waterproofing purposes (earwax)
    • %%cerumen (earwax)%% - waterproof earwax
    • @@mammary (lactiferous) glands@@ - modified apocrine sweat glands that secrete milk to nourish offspring
  • @@sebaceous (oil glands):@@ holocrine glands that produce sebum and are most abundant on the face and scalp
    • %%sebum%% - oily, waxy secretion

Miscellaneous Structures of the Skin

  • @@arrector pili muscles@@ - small muscles attached to hair follicles
  • @@nerves@@ - carry electrical impulses between brain and the rest of the body
    • %%free nerve endings%% - terminal branches of dendrites
    • %%Meissner’s corpuscles%% - (tactile corpuscles) large, encapsulated oval receptors; determine textures and shapes with touch
  • @@friction skin@@ - refers to the skin that is present along palms, fingertips, and soles of feet; used for gripping purposes
  • @@tactile finger pads@@ - area of skin that is particularly sensitive (pressure, temperature, pain)

Skin Pigments

  • melaninmelanin - dark brown to black pigment responsible for color in the hair, iris, & especially in skin
    • tanning
    • helps exposure to sunlight → UV ray protection
  • carotenecarotene - pigmentation in plants to give them color
  • hemoglobinhemoglobin - red-colored compound that gives skin ability to flush red

Keratinous Appendages of Skin

  • hair(orfur)hair (or fur) - used for warmth, cushions skull, & protects against general environmental elements
    • elements of hair:
    • ^^follicle^^ - tube-like structure that surrounds root and strang of a hair
    • ^^root^^ - descends down to dermis; surrounded by follicle
    • ^^shaft^^ - visible part of hair that sticks out of skin
    • ^^bulb^^ - forms base of hair follicle
    • ^^cuticle^^ - outermost layer of hair strand
    • ^^cortex^^ - located between hair cuticle & medulla
    • ^^medulla^^ - innermost layer of hair shaft