Integumentary System

Question 1

Skin Composition

Answer 1

epidermis

dermis

Hypodermis

Question 2

layers of the Epidermis

Answer 2

Stratified squamous keratinized epithelium

stratum corneum – dead cells (squames) – keratin filled

stratum lucidum – translucent (absent in ‘thin’ skin), present in

soles and palms – no nuclei or organelles – lots of keratin

stratum granulosum – keratohyalin granules

stratum spinosum (prickle cells) – thickest layer - some mitotic

stratum basale (single layer cuboidal, columnar) - mitotic

Question 3

Components of dermis

Answer 3

loose and dense irregular connective tissue

papillary layer – loose connective tissue - interdigitations with the epidermis called dermal ridges (dermal papillae) Capillary loops, Meissner’s corpuscles

reticular layer – coarser, denser connective tissue

Vascular plexus, hair follicles, sebaceous glands, sweat glands, Krause’s end bulbs, Pacinian corpuscles

Question 4

Components of Hypodermis

Answer 4

loose connective tissue Vasculature, can contain pads of adipocytes, Superficial fascia

Question 5

Keratinocytes

Answer 5

produce keratin, most numerous cells in epidermis – present in all layers of epidermis

Question 6

Keratinocytes : maturation

Answer 6

Keratinocytes are generated in the stratum basale, a single layer of cells. Keratinocytes move from the stratum basale (innermost layer) to the stratum corneum (outermost layer) in approximately 47 days.

Question 7

Keratinocytes – keratinization

Answer 7

Keratinocytes in upper part of stratum spinosum produce keratohyalin granules.

Keratohyalin granules in stratum granulosum contain filaggrin & trichohyalin. When granule contents are released into the cytoplasm, keratin filaments aggregate into keratin fibrils (soft keratin) (keratinization).

Question 8

Keratinocytes- exfoliation

Answer 8

Cell nucleus & organelles break down

Degradation of desmosomes by pH dependent proteases leads to exfoliation

Question 9

Keratinocytes – Water barrier

Answer 9

Water barrier components:

* Cell envelope = insoluble proteins on inner plasma membrane surface (link structural proteins with proline-rich proteins = loricrin, keratin, cystatin…)

* Lipid envelope = lipid layer on outer surface of plasma membrane (ceramides, cholesterol, free fatty acids)

Question 10

What are lamellar bodies?

Answer 10

Produced by stratum spinosum and granulosum cells

• vesicles that contains probarrier lipids synthesized in Golgi
• exocytosed into spaces between stratum spinousum & granulosum cells

Question 11

Melanocytes

Answer 11

produce melanin – located in: stratum basale (melanocyteprocesses extend to stratum spinosum), hair follicles, also in dermis

2 types of melanin: eumelanin (brown-black pigment = dark hair color) pheomelanin (red-rust pigment = blond/red hair)

Question 12

Langerhans cells

Answer 12

dendritic cells (i.e. antigen presenting cells) – stratum spinosum

no desmosomal attachments to keratinocytes

Question 13

Merkel cells (Tactile discs)

Answer 13

mechanoreception - stratum basale (abundant in fingertips), base of hair follicles, unmyelinated sensory fibers, attached to keratinocytes via desmosomes

Question 14

Encapsulated Sensory receptors

Answer 14

Meissner, Pacinian, and Ruffini corpuscles

Question 15

Unencapsulated sensory receptors

Answer 15

Free nerve endings

Merkel cells

Root hair plexus

Question 16

Skin composition: Hair

Answer 16

• elongated keratinized structure
• hair follicles are invaginations of epidermal epithelium,

embedded in dermis or hypodermis

Question 17

Skin composition: Sebaceous glands

Answer 17

• branched acinar glands in dermis
• ducts empties into hair follicle or open directly to epidermal surface
• contents (sebum) released via holocrine secretion (entire cell dies)

Question 18

Skin composition: Sweat glands

Answer 18

Eccrine sweat glands

* widely distributed

* coiled secretory portion and coiled ducts, small lumen

* ducts open to epithelium surface

Apocrine sweat glands

* axillary and perineal regions

* large lumen

* ducts open into hair follicles

* development depends on sex hormones (i.e. completed at puberty)

* pheromone and swear secretion