Integument Histology

Question 1

Layers of the epidermis (5)

Answer 1

Statum corneum
Stratum lucidem
Statum granulosum
Stratum spinosum
Stratum basale

Question 2

Epidermis is comprised of (4)

Answer 2

Keratinocytes
Melanocytes
Merkel cells
Langerhans cells

Question 3

Thick vs. thin skin

Answer 3

Thick only on palms and soles. Has 5 layers.

Thin is widespread but only has 4 layers (no stratum lucidem).

Question 4

Stratum basale

Answer 4

Bottom layer. Single layer of keratinocytes.
Mitotically active layer of cuboidal/low columnar cells.
Bound apically by desmosomes and basally by hemidesmosomes.

Question 5

Stratum spinosum

Answer 5

Several cell layers thick.

Layer thickens with pressure to produce corns and calluses.

Question 6

Stratum granulosum

Answer 6

Thickest layer of non-keratinized portion of epidermis.
Has keratinocytes with keratohyalin granules.
Irregularly shaped and variable in size.

Question 7

Keratohyalin granules

Answer 7

Found in keratinocytes.
Basophilic, cysteine and histidine-rich proteins.
Precursor to filaggrin.

Question 8

Stratum corneum

Answer 8

Anucleated w/o organelles.
Filled with mature keratin.
PM forms water barrier.
Continuously shed.

Question 9

Stratum lucidem

Answer 9

Subdivision of stratum corneum.
Seen well only in thick skin.
Poorly stained.
No organelles or nuclei.

Question 10

Keratinocytes

Answer 10

Produce keratin and participate in the epidermal water barrier.
Will produce cornified cells full of keratinization.
Undergo keratinization and desquamation.

Question 11

Basal cells

Answer 11

Synthesize intermediate filaments. Grouped into bundles called tonofibrils.

Question 12

Spinous cells

Answer 12

Keratin synthesis coninues, begin synthesis of keratohyalin granules and glycolipid containing lamellar bodies.

Question 13

Granular cells

Answer 13

Discharge lamellar bodies to form water barrier.
Keratohyalin granules w/ flaggrin present, which promotes production of tonofibrils.
Now cells are cornified.

Question 14

Epidermal differentiation and replacement

Answer 14

Initiated by division of stem cells in SB.
New cells undergo divisions in SB.
Move upward as the differentiate into keratinized cells.
Eventually lost by exfoliation.

Question 15

Epidermal-melanin unit

Answer 15

One melanocyte maintains association with a specific number of keratinocytes (1:36).

Question 16

Langerhans cells

Answer 16

APCs thet provide defense against pathogens.

Found in stratum spinosum.

Question 17

Merkel cells

Answer 17

Cutaneous sensation (fingertips). Found in stratum basale.

Question 18

Dermal-epidermal junction

Answer 18

Dermal papillae project into epidermis, complemented by epidermal ridges.

Question 19

Layers of dermis (2)

Answer 19

Papillary layer: loose CT beneath epidermis.
Includes dermal papilla and ridges.
Has vasculature and nerve endings.
Reticular layer: deep to papillary layer.
Thicker and less cellular.
Forms regular lines of tension.

Question 20

Hypodermis

Answer 20

Subcutaneous fascia.

Question 21

Meissner’s corpuscle

Answer 21

Sensitive touch receptors.

Present in dermal papillae just beneath epidermis.

Question 22

Pacinian corpuscle

Answer 22

Large ovoid structures that detect pressur or vibration.

Found in fingertips, joints, periosteum, internal organs.

Question 23

Free nerve endings

Answer 23

Terminate in SG.
Does not have CT.
Modalities in fine touch, heat, cold, and pain.
Surround most hair follicles.

Question 24

Sebaceous glands

Answer 24

Produce sebum via holocrine secretion.

Sebum discharged into infundibulum forming pilosebaceous canal.

Question 25

Eccrine (merocrine) sweat glands

Answer 25

Found throughout skin.
Myoepithelial cells facilitate exulsions of secretion.
Duct is stratified cuboidal.

Question 26

Apocrine sweat glands

Answer 26

Uses merocrine secretion to secrete proteins, carbs, ammonia.
Has myoepitheial cells.
Duct is stratified cuboidal.
Subject to adrenergic regulation.

Question 27

Melanin production

Answer 27

Reactions occur in premelanosomes in melanocyte. Once enough melanin is produced, they become melanosomes. Melanin is donated to keratinocytes via phagocytosis.