Structure and function of the skin.

Question 1

Which types of collagen concentrate around dermal blood vessels?

Answer 1

Type III and V.

Question 2

Which type of collagen constitutes 87% of dermal collagen?

Answer 2

Type I collagen.

Question 3

Which type of collagen constitutes 10% of dermal collagen?

Answer 3

Type III collagen.

Question 4

Which type of collagen constitutes 3% of dermal collagen?

Answer 4

Type V collagen.

Question 5

What three types of collagen are fibrillar?

Answer 5

Type I, III and V.

Question 6

What is collagen? How many types of collagen is there?

Answer 6

Collagen is a family of related molecules whose diverse biological roles include morphogenesis, tissue repair, cellular adhesion, cellular migration, chemotaxis, and platelet aggregation. There is 17 types.

Question 7

What are the three types of dermal fibres

Answer 7

Collagenous, reticular and elastic.

Question 8

What type of dermal fibre is the most abundant in the dermis and extra cellular matrix?

Answer 8

Collagenous fibres; which account for 90% of all dermal fibres and 80% of the dermal extracellular matrix.

Question 9

What stain is used to identify the thick collagen bands composed of multiple protein fibrils?

Answer 9

Massons trichome

Question 10

What 2 unusual amino acids does collagen contain?

Answer 10

hydroxylysine and 4-hydroxyproline

Question 11

What stain can be used to identify reticular fibres?

Answer 11

Silver stains.

Question 12

What are reticular fibres?

Answer 12

They are fine branching structures which closely approximate collagen with age.

Question 13

The dermal extracellular matrix consists of what % of elastin?

Answer 13

4%.

Question 14

Which stains best identify elastin?

Answer 14

Verhoff’s and van Gieson’s elastin stains

Question 15

What are the two components of elastic fibres?

Answer 15

Amorphous elastin and microfibrils.

Question 16

What is special about the amorphous elastin ?

Answer 16

Contains 2 unique cross linked amino acids; desmosine and isodesmosine which are not found in other mammalian proteins.

Question 17

What do the microfibrils in elastic fibres consist of?

Answer 17

Type VI collagen and fibrillin.

Question 18

What is the precursor to elastin?

Answer 18

Tropoelastin.

Question 19

What gives the dermal elastic fibres their remarkable strength?

Answer 19

The cross linking of desmosine and isodesmosine.

Question 20

What are the functions of the basement membrane zone?

Answer 20

1) Anchoring the epidermis to the dermis.
2) Maintaining a functional and proliferative epidermis.
3) Maintaining tissue architecture.
4) Wound healing.
5) Functioning as a barrier.
6) Regulating nutritional transport between epithelium and connective tissue.

Question 21

What stain best highlights the basement membrane zone?

Answer 21

Periodic acid Schiff stain. Stains poorly with H&E.

Question 22

Where is the BMZ most prominent?

Answer 22

Non-haired skin and mucocutaenous junctions.

Question 23

What special stains can be used to identify mast cells?

Answer 23

Touludine blue and acid orcein- Giemsa

Question 24

By what % does the mast cell population decrease when tissue is fixed with formalin?

Answer 24

33%.

Question 25

What are the three types of mast cells and how are they distinguished.

Answer 25

They are distinguished based on the content of the mast cell specific proteases.
1) T-mast cells: tryptase
2) C-mast cells: chymase
3) TC-mast cells: both.

Question 26

How are dermal denodrocytes different from Langerhans cells?

Answer 26

They are CD4 and CD 90 (Ty1) positive.

Question 27

What type of T cells are more common in normal canine skin.

Answer 27

Lymphocytes in normal skin are T cells (CD3+) and more commonly a/B receptor positive (vs y/O)

Question 28

In general how many mast cells are present in normal skin in cats & dogs.

Answer 28

In general, normal cat skin contains 4 to 20 mast cells per high-power microscopic field around superficial dermal blood vessels; normal dog skin contains 4 to 12 cells per high-power microscopic field.

Question 29

Where can cannabinoid receptor type 1 immunoreactivity be found within the skin?

Answer 29

Epidermis= basal & suprabasal layers.
Hair follicles = cytoplasm of IRS.
Adnexa = strong reactivity in reserve cells at the periphery of sebaceous glands (e.g proliferative & undifferented seboyctes). Also, cytoplasm of secretory & ductal cells of sweat glands
Dermis = diffuse cytoplasmic staining was observed in perivascular cells with typical mast cell morphology. Also detected in the cytoplasm of scattered fibroblasts &, rarely, in endothelial cells.