Structure and function of the skin. Flashcards
Which types of collagen concentrate around dermal blood vessels?
Type III and V.
Which type of collagen constitutes 87% of dermal collagen?
Type I collagen.
Which type of collagen constitutes 10% of dermal collagen?
Type III collagen.
Which type of collagen constitutes 3% of dermal collagen?
Type V collagen.
What three types of collagen are fibrillar?
Type I, III and V.
What is collagen? How many types of collagen is there?
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.
What are the three types of dermal fibres
Collagenous, reticular and elastic.
What type of dermal fibre is the most abundant in the dermis and extra cellular matrix?
Collagenous fibres; which account for 90% of all dermal fibres and 80% of the dermal extracellular matrix.
What stain is used to identify the thick collagen bands composed of multiple protein fibrils?
Massons trichome
What 2 unusual amino acids does collagen contain?
hydroxylysine and 4-hydroxyproline
What stain can be used to identify reticular fibres?
Silver stains.
What are reticular fibres?
They are fine branching structures which closely approximate collagen with age.
The dermal extracellular matrix consists of what % of elastin?
4%.
Which stains best identify elastin?
Verhoff’s and van Gieson’s elastin stains
What are the two components of elastic fibres?
Amorphous elastin and microfibrils.
What is special about the amorphous elastin ?
Contains 2 unique cross linked amino acids; desmosine and isodesmosine which are not found in other mammalian proteins.
What do the microfibrils in elastic fibres consist of?
Type VI collagen and fibrillin.
What is the precursor to elastin?
Tropoelastin.
What gives the dermal elastic fibres their remarkable strength?
The cross linking of desmosine and isodesmosine.
What are the functions of the basement membrane zone?
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.
What stain best highlights the basement membrane zone?
Periodic acid Schiff stain. Stains poorly with H&E.
Where is the BMZ most prominent?
Non-haired skin and mucocutaenous junctions.
What special stains can be used to identify mast cells?
Touludine blue and acid orcein- Giemsa
By what % does the mast cell population decrease when tissue is fixed with formalin?
33%.
What are the three types of mast cells and how are they distinguished.
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.
How are dermal denodrocytes different from Langerhans cells?
They are CD4 and CD 90 (Ty1) positive.
What type of T cells are more common in normal canine skin.
Lymphocytes in normal skin are T cells (CD3+) and more commonly a/B receptor positive (vs y/O)
In general how many mast cells are present in normal skin in cats & dogs.
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.
Where can cannabinoid receptor type 1 immunoreactivity be found within the skin?
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.
