1
Q
Dermis
A
- vascular supply for epidermis
- papillary layer
- reticular layer
2
Q
What are the features of the papillary and reticular layers of the dermis?
A
papillary layer
-dermal ridges or papillae interdigitate with rete pegs of epidermis
reticular layer
-thickest laye
3
Q
Where do nerve endings occur?
A
- hypodermis
- dermis
- epidermis
4
Q
layers of the epidermis/ dermis?
A
- stratum corneum
- stratum lucidum (thick skin only)
- stratum granulosum
- stratum spinosum
- stratum basale
- stratum germatitome
5
Q
Which layer of epidermis/dermis is only found in thick skin?
A
stratum lucidum
6
Q
Keratinocytes
A
- “skin cells”
- make up bulk of epidermis
7
Q
Common animal carcinoma arising from keratinocytes?
A
- squamous cell
- basal cell
8
Q
melanocytes
A
- type of epidermal cell
- pigment cells = produce melanin
- need a special stain to see
- originate from neural crest
9
Q
Langerhan’s Cell
A
- antigen-presenting cells in epidermis
- mainly in stratum spinosum
- originate from monocytes
- have an oval, pale nucleus and pale cytoplasm
10
Q
How do Langerhan’s Cells work?
A
- originate from bone marrow precursors (monocytes)
- migrates to epidermis
- phagocytizes antigens
- migrates to lymph nodes
- presents antigen to lymphocytes
11
Q
How melanocytes look
A
- round cells
- pale cytoplasm
- have cytoplasmic processes between keratinocytes
12
Q
How do melanocytes work?
A
- produce melanin
- transfer melanin granules to epithelial cells, where the granules shield the nucleus
13
Q
What is melanoma?
A
- melanocyte tumor
- can be pigmented or nonpigmented
14
Q
Merkel Cell
A
- specialized touch receptor
- modified keratinocyte in contact with nerve ending
- epithelial in origin
- difficult to tell apart from melanocytes
- found in basal layer
15
Q
Skin Glands
A
- sebaceous glands (with hair follicles)
- apocrine = empty into hair follicles
- merocrine = found on hairy or non-hairy skin, but do not empty into hair follicles
- special glands (species dependent)
- mammary glands
16
Q
Examples of special glands
A
Sheep
-infraorbital, inguinal, and interdigital glands
Goat
-glands near horn
Cats
-submental (below chin) organ and circumoral glands
Dogs and Cats
-supracaudal glands
Dog, Cat, Ferret, and Skunk
-glands of the anal region
17
Q
Hair Follicle
A
- continuous with the epidermis of the surface of the skin
- has several layers
18
Q
Shaft of the hair
A
- protrudes from surface
- has cuticle, cortex, and medulla
- cortex is hard keratin
- medulla is only found in thick hair and is the light center of hair
19
Q
Root of the hair
A
- embedded in follicle
- has cuticle, cortex, and medulla (+/-)
- bulb = expanded end of root; surrounds a dermal papilla
20
Q
Follicle layers
A
- hair
- inner root sheath
- outer root sheath
- connective tissue sheath
21
Q
location of the Cuticle?
A
between hair and inner root sheath
22
Q
Inner Root Sheath
A
doesn’t extend superficially beyond opening of sebaceous glands
23
Q
Outer Root Sheath
A
contiunous with the skin surface
24
Q
Location of basement membrane for hair?
A
between outer root sheath and connective tissue sheath
25
How hair grows
- dividing cells in bulb cover surface of dermal papilla
| - new cells "push" hair upward as they form
26
During hair growth, what cells become what?
- cells at tip of papilla = form medulla (if present)
- cells covering sides of papilla = form cortex
- cells at reflection of cells at base of papilla = form cuticles and inner root sheath
27
Type of Hair
- guard (principle) hairs
- wool (secondary) hairs
- sensory hairs (tactile or sinus; vibrissae)
28
Sensory hairs
- tactile or sinus
- AKA vibrissae
- contain venous sinuses in connective tissue sheath around hair root
- nerve endings are in the connective tissue
- these hairs are sensitive to movement of the hair
29
The venous sinus in a tactile hair divides which layer of the folllicle into two layers?
connective tissue sheath
30
What is hoof tissue composed of?
tubular and intertubular horn
"like rods in concrete"
31
How does hoof tissue receive its nutrition?
- from underlying connective tissue
| - really it's the dermis, but often called "corium" in case of hoof
32
Hoof wall
- main part of hoof
- coronet = junction of wall with skin
- periople = cuticle-like covering over hoof wall
33
Sole of hoof
- bottom flat surface of hoof
| - white line: junction of wall and sole
34
Frog of hoof
wedge of tissue in center of ground surface
35
Hoof (epidermis) and corium (dermis)
- stratum basale of epidermis tightly covers the surface of the corium
- projections of corium (laminae and papillae) are templates for dividing hoof cells that cover them
- hoof's blood and nerve supply is in the corium
36
What is laminitis?
inflammation of sensitive layers of tissue (laminae) inside the hoof in horses and other animals
37
Laminae
- found in both the hoof and the corium
- primary structures for adherence of hoof wall to foot
- hoof and corium laminae interdigitate with each other
- increases surface area for adhesion of hoof to foot
- two divisions: primary and secondary (only one division of laminae in cows)
38
Primary Epidermal Laminae of the hoof
- composed of non-pigmented keratinized cells
- connected to inner surface of stratum medium
- secondary laminae attached to them
39
Secondary Epidermal Laminae of the hoof
- only in equids
- composed of stratum basale and stratum spinosum
- each primary lamina contains 100-200 secondary laminae
40
Papillae of the hoof
- templates for hoof wall, sole, and frog
| - cause epidermis dividing over them to form tubules and intertubular horn, which project downward to form hoof wall
41
Hoof Wall Layers
- stratum externum (tectorium)
- stratum medium
- stratum internum (lamellatum)
42
```
Stratum externum
(tectorium)
```
- layer of hoof wall
- periople = thin waxy outer layer of hoof
- very thin and cuticle-like
43
Stratum medium
- bulk of hoof wall
| - grows from cell division of the epidermis in the coronary region
44
```
Stratum internum
(lamellatum)
```
- epidermal laminae form this layer
| - interdigitate with laminae of corium
45
Growth of Hoof Wall
- division occurs in stratum basale where it covers the corium of coronary band
- forms tubular and intertubular horn
- keratinized cells move downward with growing hoof wall
- sole and frog grow similarly
46
Rate of hoof growth
- 1/4 to 1/2 inch per month
| - Defects at the coronary region take 8-12 months to grow out completely and reach ground surface
47
Separation of hoof wall from third phalanx, as often occurs in laminitis, is usually due to loss of normal function of what?
laminae
48
Claws
- claws (and human nails) very similar to hoof
| - most claws and nails have no secondary laminae
49
Bovine horn
- similar to hoof, except no laminae
| - epikeras = a thin layer of skin covering the junction between the base of a horn and the surrounding skin
50
Rhino horn
- essentially like horse hoof
| - grows directly from skin w/o bony base
51
Antlers
- bone covered by skin ("velvet")
| - entire structure shed annually
Microanatomy 1
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