1 of 27

Integument

2 of 27

Skin

  • Epidermis: Superficial layer
    • Made of stratified squamous keratinized epithelium
    • 4-5 Layers
  • Dermis: Underlying connective tissue layer
    • 2 Layers
  • Hypodermis: Not part of the skin, it is deep to the dermis
    • Primarily adipose tissue

​

2

3 of 27

Layers of the Epidermis

  1. Stratum corneum: Outermost layer
    • 20-30 cell layers thick
    • Cells are dead and flattened
    • Full of keratin
    • Constantly being rubbed off
  2. Stratum lucidum: Thin translucent layer of dead keratinocytes
    • Found only in thick skin

3

4 of 27

Layers of the Epidermis

  1. Stratum granulosum: Cells contain granules
    • The upper part of this layer has cells that are beginning to die
    • Lamellated granules contain a waterproofing glycolipid that is secreted into the extracellular space
    • Keratohyaline granules combine with intermediate filaments to form keratin fibrils

​

4

5 of 27

Layers of the Epidermis

  1. Stratum spinosum: several cell layers
    • Cells also dividing
    • Cells contain bundles of intermediate filaments made of pre-keratin
  2. Stratum basale: single row of cells
    • Adjacent to the dermis
    • Constantly dividing and pushing up layers

​

5

6 of 27

6

7 of 27

Dermis

  • The dermis is the connective tissue layer under the epidermis
  • Papillary Layer: Superficial dermal region
    • Areolar connective tissue
    • Contains capillaries, lymphatics and sensory neurons
    • Dermal Papillae: the fingerlike projections from the superior surface
    • Epidermal ridge: The epidermal layer that dips down into the dermal papillae
      • Create fingerprints

7

8 of 27

8

Dermal Papillae

Epidermal ridge

Papillary�Layer

Reticular�Layer

Epidermis

9 of 27

Finger Prints

9

Epidermal

Ridge

10 of 27

Dermis

  1. Reticular Layer: Deepest skin layer
    • Dense irregular connective tissue
    • Contains the arteries, veins, sweat and sebaceous glands
    • Cleavage lines: the deep creases (like in the palm) where collagen and elastic fibers are arranged in parallel bundles.

10

11 of 27

Hypodermis

  • Subcutaneous layer that is not part of the skin
    • Beneath the dermis layer
  • Composed of adipose and areolar connective tissue
  • Highly vascular

​

11

Dermis

Hypodermis

12 of 27

Cells of the Epidermis

  • Keratinocytes: The main cells of the epidermis
    • Produce keratin, a fibrous protein that gives skin its durability and protective capabilities
  • Melanocytes: Spidery black cells
    • In stratum basale
    • Produce melanin, the pigment that protects skin from UV damage

12

13 of 27

Cells of the Epidermis

  • Langerhans’ Cells: Also called epidermal dendritic cells
    • In stratum spinosum
    • Macrophages that migrated from the bone marrow that phagocytize pathogens
    • Immunologic surveillance cells

13

14 of 27

Cells of the Epidermis

14

15 of 27

Hair

  • Root: Everything that is not sticking out of the skin

​

  • Shaft: The part sticking out of the skin
  • Bulb: Active growing site

​

15

16 of 27

Hair Histology

16

17 of 27

Arrector Pili Muscle

  • Arrector pili muscle: Smooth muscle that pull hair upright during fright or cold (goose bumps)

17

18 of 27

Apocrine Sweat Glands

  • Apocrine glands: secrete a protein and fat rich substance that bacteria can use for nutrients (creates body odor)
  • Found in the armpits, around nipples and in the pubic region
  • Secrete products into hair follicles or directly onto the surface.
  • Begin functioning at puberty

18

19 of 27

Apocrine �Sweat Glands

  • Red arrow - Apocrine Sweat Glands
  • Green arrow - Hair follicle

​

19

20 of 27

Eccrine (Merocrine) Sweat Glands

  • Eccrine sweat glands are not associated with hair follicles.
  • Ducts open directly on the surface of the epidermis

​

​

20

21 of 27

Sebaceous �Glands

​

  • Sebaceous glands
    • Produce oily substance called sebum
    • Helps waterproof the skin
    • Acne: infection of the sebaceous gland

21

22 of 27

Sebaceous Follicle

  • Sebaceous glands not associated with hair follicles
  • Secrete their product directly on the skin surface
  • Located on face, back, chest, nipples and external genitalia

22

23 of 27

Pacinian (Lamellated) Corpuscle

23

  • Lie deep in the dermis
  • Respond only when deep pressure is first applied
  • Monitor high frequency vibrations

24 of 27

Meissner’s (Tactile) Corpuscle

  • Located in the dermal papillae
  • Receptor for light touch

24

25 of 27

Merkel Cells

  • Merkel Cells:
    • At the junction of the sensory nerve endings
    • In stratum basale

​

25

26 of 27

Fingernails

  • Scale like modification of the epidermis
  • Free edge: part that grows away from the finger
  • Body: visible attached portion
  • Root: Embedded in skin and sticks to the nail bed
  • Nail Bed: Extension of the stratum basale beneath the nail
  • Nail Matrix: Proximal part of the nail bed responsible for nail growth
  • Lunula: white crescent area; Most active growth region of nail matrix

26

27 of 27

Fingernail �Structures

27