Dermis and Hypodermis

Question 1

describe the dermis papillary layer

Answer 1

• superificial layer
• loose connective tissue (more cells)
• contains blood vessels
• predominantly type I and type III collagen fibers
• contains meissner corpuscles (sensory)

Question 2

describe the dermis reticular layer

Answer 2

• considerably thicker than and deeper to the papillary layer
• dense irregular connective tissue (fewer cells)
• it is characterized by thick irregular bundles of mostly type I collagen and coarser elastic fibers

Question 3

describe the hypodermis

Answer 3

• deep to the reticular layer of dermis
• serves as a major energy storage site and provides insulation
• hair follicles, glands and mechanoreceptors extend into this layer

Question 4

describe the hair follicle

Answer 4

• invagination of the epithelium that extends into hypodermis
• associated with a sebaceous gland and smooth muscle = phlebo sebaceous organ
• not found in thick skin
• consists of:
  
  • infundibulum (interacts with surface of skin)
  • isthmus (narrowing as it goes down)
  • inferior segment (contains bulb)
    
    • bulb contains the matrix cells for hair formation
      
      • melanocyte stem cells are found in the bulb

Question 5

describe hair

Answer 5

• consists of hard keratin
• color is determined by the amount of melanin produced by the melanocytes in the bulb
• 3 layers
  
  • medulla: central part contains large vaculated cells and only present in thick hairs
  • cortex: peripherally to the medulla and contains cuboidal cells which undergo differentiation into kertain-filled cells
  • cuticle: squamous cells that form the outermost layer

Question 6

describe nails

Answer 6

• hard plates of epidermal keratinized cells

Question 7

describe the sebaceous glands

Answer 7

• simple branched acinar
• secretory portion is located in the deeper dermis
• opens into hair follicle
• secretion is holocrine
• product is sebum
• helps prevent the hairs from becoming dry and brittle

Question 8

Answer 8

• sebaceous gland
• simple branched acinar

Question 9

describe the sweat glands

Answer 9

• found in thick and thin skin
  
  • heat trigger vs emotional stimulus
• simple coiled tubular glands
• secretory portion is in the deep dermis
• contains:
  
  • clear cells: abundant glycogen stains well with PAS
  • dark cells: rER and secretory granules are abundant
  • myoepithelial cells: basal aspect of the secretory segment

Question 10

describe apocrine glands

Answer 10

• found only in armpit and perineum
• coiled tubular glands
• secretion mode is merocrine (misnomer)
• ducts are straight and lined by stratified cuboidal epithelium
• opens into the hair folicle

Question 11

Answer 11

• sweat gland seen on the left and duct seen on the right
  
  • duct: stratified cuboidal cells

Question 12

Answer 12

• apocrine gland
• lumen is larger

Question 13

describe free nerve endings

Answer 13

• most numerous and terminate in the stratum granulosum
• subserve multiple sensory modalities
  
  • fine touch, and temperature
• networks of free dermal endings surround most hair folicles
  
  • attach to their outer root sheath
  • very sensitive to hair movement and serve as mechanoreceptors

Question 14

Pacinian corpuscle

Answer 14

• deep dermis and hypodermis
• nerve fiber in the middle surrounded by flattened Schawnn cell lamellae that form the inner core of the corpuscle
• detect pressure and vibration

Question 15

Answer 15

• Pacinian corpuscle
• detect pressure and vibration

Question 16

Meisner’s corpuscle

Answer 16

• touch receptors particularly responsive to low frequency stimuli
• found in the dermal papillae just beneath the epidermal basal lamina

Question 17

describe Ruffini’s corpuscle

Answer 17

• respond to stretch and torque