Integumentary System (Skin)

Question 1

General Parts of the skin

Answer 1

1. Epidermis
2. Dermis
3. Hypodermis or subcutaneous tissue

Question 2

Functions of integumentary system

Answer 2

• Protection
• selective permeability
• thermoregulation
• Sensation
• metabolic functions

Question 3

Cells of epidermis

Answer 3

• keratinocytes (80%)
• melanocytes (5-10%)
• langerhans cells (2-8%)
• Merkel cells (<1%)

Question 4

Histological types of skin

Answer 4

• thin skin (hairy)
• thick skin (in Palms and soles)

Question 5

Cellular layers in epidermis of thin skin

Answer 5

1. Basal layer (stratum basale)
2. Spinous layer (stratum spinosum)
3. Granular layer (stratum granulosum)
4. Keratin (corneal) layer (stratum corneum)

Question 6

Basal layer

Answer 6

• Single layer of cuboidal or low columnar cells (keratinocytes)
• cells divide for constant Regeneration of epidermis
• each cell is bound to basal lamina by hemidesmosomes
• cells to each other by desmosomes

Question 7

Spinous layer

Answer 7

• several layers of keratinocytes

Question 8

Granular layer

Answer 8

• 3-5 layers of keratinocytes that become progressively more flattened
• contain keratohyaline and lamellar granules (contain lipids, are for epidermal Water barrier)

Question 9

Keratin layer

Answer 9

• 15-20 layers of squamous, keratinized cells filled with keratin
• pH decreases from neutral to acidic

Question 10

Epidermis of thick skin

Answer 10

• very thick keratin layer (~50 layers of keratin flakes)
• additionally clear Layer (stratum lucidum) between Granular and keratin layer
• Deep epithelial ridges and long dermal pappillae

Question 11

Clear layer

Answer 11

• contains eosinophilic cells, Full of eleidin

Question 12

Proliferation and maturation of keratinocytes

Answer 12

• human epidermis renews about every 15-30 days

Question 13

Skin Color depends on?

Answer 13

-melanin (Pigment produced by melanocytes)
- red blood cells
- carotenes
- bilirubin

Question 14

Melanocytes

Answer 14

• are in basal layer
• more numerous in areas which are most exposed to light
• melanin protects skin from UV radiation

Question 15

Langerhans cells

Answer 15

• present in all layers of epidermis (except for keratin layer)
• Most often in Spinous layer
• derived from monocytes
• are Antigen-presenting cells

Question 16

Merkel (epithelial tactile) cells

Answer 16

• between keratinocytes in the basal layer of epidermis
• rounded, branched cells
• are intra-epidermal touch receptors

Question 17

Dermis

Answer 17

• Composed of CT proper
• Supports epidermis, binds it to hypodermis
• contains Blood and lymphatic vessels, nerves and sensory endings, hair follicles, sebaceous glands, arrector pili muscle and sweat glands

Question 18

Layers of dermis

Answer 18

1. Papillary layer
2. Reticular Layer

Question 19

Papillary layer (of dermis)

Answer 19

• below epidermis and BM
• relatively narrow
• out of LCT (Type I & II collagen, fibroblasts)
• has capillaries and Meissner’s corpuscles

Question 20

Reticular Layer (of dermis)

Answer 20

• Collagen Type I and elastic fibers are randomly oriented

Question 21

Hypodermis or subcutis

Answer 21

• Loose CT + adipose tissue
• glands

Question 22

Function of hypodermis

Answer 22

• binds the skin loosely to underlying tissues, provides mobility for skin
• Energy Storage site

Question 23

Nerve supply of skin

Answer 23

1. Uncapsuled nerve endings
   - free nerve endings
   - Merkel cells
   - Root hair plexuses
2. Encapsulated nerve endings
   - Meissner corpuscles (visible)
   - Pacinian corpuscles (visible)
   - ruffini corpuscles
   - Krause end bulbs

Question 24

Pilosebaceous unit

Answer 24

• hair follicle
• sebaceous gland
• arrctor pili muscle

Question 25

Parts of hair

Answer 25

- hair root (inside hair follicle, inside skin) - hair shaft (beyond skin surface)

Question 26

Segments of hair follicle

Answer 26

1. Infundibulum - from skin surface to Level of opening of sebaceous glands 2. Isthmus - from opening of sebaceous gland to Insertion of arrector pili muscle 3. Inferior segment At base of inferior Segment: hair bulb with dermal papilla

Question 27

Hair shaft

Answer 27

1. Medulla or core - innermost Layer 2. Cortex - broad layer - highly keratinized layer - contain hair’s pigments 3. Cuticle - on surface of hair - consists of overlapping hard keratin plates

Question 28

Hair color

Answer 28

- Because of Melanin in the cells of cortex - turns white with age due to Air bubbles between the cells

Question 29

Phases of hair growth

Answer 29

1. Anagen (growth) - up to 7 years 2. Catagen (regression) - several days 3. Telogen (rest) - several months - inactive period, hair is shed, ne could be formed

Question 30

Sebaceous glands (glandulae sebaceae)

Answer 30

- surround hair follicles - secrete **Sebum** to hair shaft and skin surface

Question 31

Functions of sebum

Answer 31

- maintains stratum corneum and hair shafts - maintain skin’s flexibility - waterproof - barrier for skin protection — Sebum is product of **holocrine secretion** (programmed Cell death)

Question 32

Arrector pili muscle

Answer 32

- bundle of smooth muscle cells - one end inserted in connective tissue of hair follicle, another into Papillary Layer of dermis

Question 33

Contraction of arrector pili muscle

Answer 33

- pulls hair shaft to more erect Position - goose skin - sebum is discharged from sebaceous glands

Question 34

Type of Sweat glands

Answer 34

1. Eccrine sweat glands - right on surface of skin 2. Apocrine sweat glands - into hair follicle

Question 35

Fingernail

Answer 35

1. nail plate, keratinized plate - nail body - nail root (nail Matrix) 2. nail bed, stratified squamous epithelium (only basal and spinal epidermal layers)

Question 36

Differences of keratin

Answer 36

1. Soft keratin - in epidermis 2. Hard keratin - in nail and hair