Dermis, epidermal appendages

Question 1

functions of basement membrane zone (BMZ) (4)

Answer 1

• joins the epidermis with dermis
• establishes tissue architecture
• selectively permeable to macromolecules
• communication between dermis and epidermis

Question 2

conditions of BMZ

Answer 2

selectively attacked in diseases like bullous pemphigoid, epidermolysis bullosa, lupus erythematosus, some drug rxns (immune and genetic issues)

Question 3

functions of the dermis

Answer 3

• supports and nourishes the epidermis

- interacts with epidermis during embryogenesis, morphogenesis, wound repair and remodeling

Question 4

what’s so fucking special about the dermis?

Answer 4

it’s the thickest part of the skin! only slightly important…

Question 5

what makes up the matrix of the dermis

Answer 5

fibers, ground substance, cells, blood vessels, and nerves

Question 6

cells of the dermis (4)

Answer 6

• fibroblasts
• mast cells
• histiocytic cells/histiocytes
• melanocytes (in some species)

Question 7

purpose of fibroblasts

Answer 7

• produce collagen, elastic and reticular fibers, and ground substance
• produce fibronectin (wound healing, cell-cell interaction, adhesion)

Question 8

purpose of mast cells

Answer 8

• type I hypersensitivity reactions

- cross linking of 2 allergen-specific IgE antibodies bound to mast cell surface –> mast cell degranulation

Question 9

what do mast cells contain and what do those things do

Answer 9

• contain histamine, leukotrienes, prostaglandins, proteolytic enzmes
• induce clinical signs of inflammation

Question 10

what are histiocytes

Answer 10

• tissue monocytes that can become activated to macrophages
• dermal dendritic cells –> antigen processing and presenting
• present around vessels

Question 11

what are histiocytes that have phagocytized melanin called

Answer 11

melanophages

Question 12

what fiber makes up 90% of the dermis

Answer 12

collagen

Question 13

what is collagen

Answer 13

• major fiber of the dermis
• provides tensile strength
• continuously synthesized and degraded

Question 14

what is a disease characterized by enzymatic defects in collagen synthesis –> causes skin tearing

Answer 14

ehlers-danlos syndrome

Question 15

what are the 4 fibers of the dermis

Answer 15

• collagen
• elastic fibers
• reticulin fibers
• muscle fibers

Question 16

elastic fibers info

Answer 16

• 10% of dermis

- diseases: cutis laxa, solar elastosis

Question 17

reticulin fibers info

Answer 17

• fine, branching structures
• surround epidermal appendages, vessels, and nerves
• <1% of fibers of the dermis

Question 18

what is the important dermal muscle and what does it do

Answer 18

• arrector pili muscles
• originate near BMZ, attach to hair follicle near base
• cause erection of the hairs (smooth muscle)

Question 19

what does ground substance of the dermis consist of

Answer 19

• several anionic polysaccharides known as glycosaminoglycans
• in vivo: linked to proteins and known as proteoglycans
• produced/degraded by fibroblasts and mast cells

Question 20

functions of ground substance (2)

Answer 20

• interactions with collagen and cell surfaces

- influence water binding and flow of solutes

Question 21

what are present in high numbers in the skin of shar peis

Answer 21

proteoglygans

Question 22

what is cutaneous mucinosis in shar peis

Answer 22

abnormally high quantities of proteoglycans

Question 23

what is myxedema

Answer 23

large quantity of ground substance related to hypothyroidism (“tragic facial expression”)

Question 24

does hairy skin have a more complicated or less complicated superficial dermal surface than non-haired skin?

Answer 24

less complicated

Question 25

where are rete ridges found

Answer 25

- glabrous skin has prominent dermal papillae (rete ridges) | - footpads and nasal planum

Question 26

what is dermis divided in

Answer 26

- papillary dermis (superficial) --> more cellular, finer fibers - reticular dermis (deep) --> less cellular, coarse fibers

Question 27

in hairy animals, where are dermal papillae found

Answer 27

non-haired skin only (not present in haired skin)

Question 28

define: hypodermis/subcutis/panniculum adiposum

Answer 28

subcutaneous tissue below the dermis composed primarily of fat (lipocytes grouped together in lobules)

Question 29

functions of hypodermis (4)

Answer 29

- fat storage - heat insulation - body contour - shock absorption (footpads)

Question 30

what is sterile inflammation of the hypodermis

Answer 30

sterile nodular panniculitis --> nodules that may or may not drain

Question 31

what are the epidermal appendages

Answer 31

sebaceous glands, sweat glands (apocrine and eccrine), hair and follicles, claws, nails, hooves, horns

Question 32

sebaceous glands info

Answer 32

- present throughout haired skin - empty info hair follicle - sebum forms an emulsion that lubricates, aids in water retention, etc --> bacteriostasis, fungistasis

Question 33

factors that increase sebum production

Answer 33

- androgens - progesterone - thyroid hormones

Question 34

factors that decrease sebum production

Answer 34

- corticosteroids (glucocorticoids) | - estrogen

Question 35

what can dietary fat deficiencies do to sebum production

Answer 35

can increase or decrease production and have qualitative changes

Question 36

2 diseases associated with sebaceous glands

Answer 36

- sebaceous adenitis | - sebaceous hyperplasia or adenomas

Question 37

apocrine sweat glands

Answer 37

- most extensive in domestic animals - present throughout haired skin - apocrine secretion + sebum = emulsion on skin/hair

Question 38

why are apocrine glands important in horses

Answer 38

- temperature regulation | - anhydrosis --> inability to sweat (can lead to hyperthermia)

Question 39

eccrine sweat glands

Answer 39

- not associated with hair follicles | - restructed to footpads, frogs of ungulates, carpus/snout of pig, nasal planum

Question 40

what things make up the pilo-sebaceous/apocrine apparatus

Answer 40

- hair follicle - sebaceous glands - apocrine glands

Question 41

what is the dilation at the base of the hair follicle

Answer 41

a bulb that encloses the dermal papilla

Question 42

3 phases of hair growth cycle

Answer 42

- anagen: growth phase - catagen: intermediate phase - telogen: resting phase

Question 43

when are melanocytes of the hair bulb active

Answer 43

only during anagen

Question 44

factors affecting hair growth (3)

Answer 44

- hormones - nutrution - diseases

Question 45

hormones and hair growth

Answer 45

- thyroid hormone initiates anagen (hypothyroidism --> alopecia) - glucocorticods and estrogen inhibit anagen (cushings, ovarian tumor --> alopecia)

Question 46

nutrition and hair growth

Answer 46

deficiency in dietary protein can lead to abnormal color and structure of hairs

Question 47

what is telogen defluxion

Answer 47

- 2-3 months after stressful event | - result of excessive glucocorticoid secretion --> inhibition of anagen

Question 48

simple follicles

Answer 48

- one hair emerging from single hair follicle pore - follicle is large and rooted deep in dermis - associated sebaceous and apocrine glands plus arrector pili muscle - omnivores and herbivores

Question 49

compound follicles

Answer 49

- combination of primary and secondary follicles - secondary follicles are smaller, buds from primary, lack apocrine gland and arrector pili muscle - multiple hairs from a single hair follicle pore - dogs, cats, goats, ferrets, sheep

Question 50

parts of the hair

Answer 50

- shaft: free portion above skin surface | - root: proximal portion inside follicle (root attached by hair bulb to underlying papilla)

Question 51

layers of the hair (3)

Answer 51

- cuticle (outermost layer) - cortex (keratinized cells, melanin) - medulla (loose cells, melanin, little influence on hair color) --> not all hairs have a medulla

Question 52

types of hair

Answer 52

- primary (guard hairs) - secondary (undercoat) - lanugo (non-medullated, not in dogs/cats after birth) - wool - sinus/tactile (whiskers --> sensory)