Anatomy of the Skin Flashcards
1
Q
% body weight occupied by the skin
A
16%
2
Q
Define the epithelium of the skin
A
Stratified squamous epithelium, keratinized
3
Q
Layer beneath the dermis
A
Hypodermis
4
Q
Main type of connective tissue in the dermis
A
Dense irregular connective tissue
5
Q
Main type of connective tissue in the hypodermis
A
Loose connective tissue
6
Q
Contents of hypodermis
A
Adipose tissue (unilocular adipocytes; fat cells)
7
Q
What is the hypodermis continuous with?
A
The deep fascia surrounding nerves and bones
8
Q
Describe the epithelium of the wet surface of the oral cavity
A
Stratified squamous epithelium, non-keratinized
9
Q
5 functions of the skin
A
- Protection from injury and dessication
- Receive stimuli from the environment
- Excretion of various substances
- Participation in thermoregulation and maintenance of water balance
- Cutaneous immunigenicity
10
Q
What mediates the skin function of protection from injury and dessication?
A
Keratinocytes of the epithelium
11
Q
What mediates the skin’s ability to receive stimuli from the environment?
A
- Merkel cells within the epithelium
- Nerve endings in and beneath the epithelium
12
Q
What mediates the excretion of substances from the skin?
A
- Sebaceous glands associated with the hair
- Sweat glands
13
Q
What mediates thermoregulation and maintenance of water balance by the skin?
A
- Insulating properties of secretion by keratinocytes that act as hydrophobic barriers to water
- Shivering mechanism related to “goose-bumps”
14
Q
What mediates cutaneous immunogenicity by the skin?
A
Langerhans cells within the epithelium acting as antigen-presenting cells
15
Q
From what are the appendages of the skin derived?
A
The epithelium of the skin
16
Q
4 appendages of the skin
A
- Nails
- Hair
- Sebaceous glands
- Sweat glands
17
Q
2 layers of the dermis
A
- Papillary layer
- Reticular layer
18
Q
Describe the composition of the papillary layer of the dermis
A
- Composed of finger-like projections of epidermis (rete pegs) into the dermis
- Can be thought of conversely as finger-like projections of loose connective tissue from the dermis into the epidermis
19
Q
From what embryologic germ layer is the keratinizing system derived?
A
Ectoderm
20
Q
2 distinct cell lineages which compose the stratified squamous epithelium of the skin
A
- Keratinocytes
- Melanocytes
21
Q
Fibrous protein produced by keratinocytes
A
Keratin
22
Q
Function of keratin
A
Transforms the keratinocytes into a dead cell layer (keratinized/cornified layer)
23
Q
Typical time length of cytomorphosis of a keratinocyte
A
15 - 30 days
24
Q
Function of melanocytes
A
Produce pigment (melanin) to protect against UV radiation
25
Embryological origin of melanocytes
Neural crest
26
When do the melanocytes invade the skin during development?
3rd to 6th month in utero
27
2 cells of the epidermal epithelium that do not belong to either the keratinizing system nor the pigmentary system
* Langerhans cell
* Merkel cell
28
5 layers of the epidermis from the innermost to the outermost layer
1. Stratum Basale/Germinativum (Basal Layer)
2. Stratum Spinosum (Spiny Layer)
3. Stratum Granulosum (Granular Layer)
4. Stratum Lucidum (Clear Layer)\*\*
5. Stratum Corneum (Cornified Layer)
NOTE: Stratum lucidum is not in ALL epidermises
29
4 examples of structures derived from the ectoderm
* Lining of oral and nasal cavities
* Cornea
* Skin epidermis
* Glands of skin
30
4 examples of structures derived from the endoderm
* Lining of the GI tract
* Lining of the respiratory tract
* Liver
* Pancreas
31
3 examples of structures derived from the mesoderm
* Renal tubules
* Lining of the reproductive tract
* Lining of blood vessels
32
Shape of keratinocytes
Cuboidal
33
When do mitoses occur in the stratum basale of the epidermis?
Mostly at night
34
Purpose of hemidesmosomes
Cell-matrix adhesions
35
Protein associated with hemodesmosomes
Integrins
36
Purpose of desmosomes
Cell-cell adhesion
37
Protein associated with desmosomes
Cadherins
38
Connective tissue type of the epidermal basement membrane
Collagen IV and Laminin
39
Type of collagen that comprises the anchoring fibrils contained in the papillary layer of the dermis
Collagen VII
40
Type of collagen that comprises the reticular fibril found in the papillary layer of the dermis
Collagen III
41
Intermediate filaments of the stratum spinosum
Tonofilaments
42
Number of keratin genes (cytokeratins) in epidermis
14
43
Number of diseases identified with mutated keratin genes
70
44
Location of keratins in the stratum spinosum and where they insert
In the spiny processes; insert into desmosomes
45
Where is the stratum lucidum found?
Skin that is very thick (i.e. sole of foot)
46
Thickness of stratum granulosum
3 - 5 layers of cells
47
Describe the cells of the stratum lucidum
No organelles (not even nucleus); dead
Full of keratin tonofibrils
48
3 constituents of the stratum granulosum
* Large keratohyalin granules (filaggrin protein) associated with tonofibrils
* Increased number of lamellated bodies/granules
* Increased transglutaminase crosslinking
49
What do the cells of the stratum spinosum secrete?
Distinct lamellated granules (membrane coating granules)
50
What are the lamellated granules of the stratum spinuson ccomprised of?
Glycolipids (NOT phospholipids)
51
2 proteins deposited under the membrane as a cell envelope in the stratum corneum
Involucrin
Loricrin
52
What occupies the intercellular space in the stratum corneum?
Lipids
53
How does desquamation occur in the stratum corneum?
Desmosomal attachments are released
54
Define epidermolysis bullosa
Blistering in response to minor trauma
55
Cause of epidermolysis bullosa
Defective epidermal cell adhesion (acantholysis)
56
Describe basal cell carcinoma
Basal cells affected, but not metastatic
57
Cells affected by squamous cell carcinoma
Keratinocytes
58
Cause of psoriasis
7x increased cell proliferation (i.e. turnover of skin is less than 30 days) and T-cell activation (autoimmune)
59
Define warts
Benign infection with papilloma viruses
60
Define blisters
Separations between keratinocytes due to trauma
61
Define ichthyosis
Abnormal keratinization or glycolipid processing/release (i.e. filaggrin and transglutaminase mutations)
62
Define moles
Large aggregation of melanocytes
63
Location of cell body of melanocytes
Stratum basale
64
Contents of pre-melanosomes
Tyrosine
65
Describe how melanin is formed
1. Melanosome is formed by tyrosinase vesicle + pre-melanosome
2. Tyrosine activated by tyrosinase and UV
3. Tyrosine --\> Melanin
66
2 types of melanin and the colors associated with them
* Eu (dark brown)
* Pheo (red,yellow)
67
Method of melanin release to keratinocytes
Cytovrine
68
Location of melanin granules
Dendritic-like cell processes
69
Cause of albinism
Gene mutations in tyrosinase gene (complete or partial)
70
Risk associated with albinism
Increased risk of skin cancer
71
Role of Langerhans cell
Bind foreign substances (antigens) and migrate to lymph nodes to present to T lymphocytes (i.e. it's an APC)
72
From where are Langerhans cells derived?
Bone marrow
73
Granules associated with Langerhans cells
Birbeck (vermiform) granules (NOTE: function unknown)
74
Granules associated with Merkel cells
Dense-cored granules (NOTE: function unknown)
75
8 functions of the extracellular matrix (ECM)
1. Connecting and supporting (typically collagen fibrils)
2. Signals for cell proliferation and differentiation
3. Cell communication (outside-in/matrix-cell signalling)
4. Cell protection
5. Transmits and attenuates mechanical signals
6. Compartment for blood vessels, lymphatics, nerves, etc.
7. Transport system
8. Controls diffusion of soluble growth factors
76
3 types influences on cells that can affect their fate
* Physical signals
* Soluble signals
* Cell-cell interactions
77
3 examples of soluble signals that can influence a cell
* Growth factors
* Cytokines
* Chemokines
78
6 examples of physical signals that can influence a cell
* Fibronectin
* Vitronectin
* Laminin
* Collagen
* Fibrillin
* GAGs, PGs
79
2 examples of cell-cell interactions that can influence the cell
* Cadherins
* CAMs
80
4 cell fate processes
1. Replication
2. Differentiation
3. Migration
4. Apoptosis
81
3 potential outcomes of cell signalling and coordinated functions
* Tissue formaiton
* Tissue homeostasis
* Tissue regeneration
82
2 types of connective tissue
* CT proper
* CT specialized
83
5 types of CT proper and their associated levels of cellularity
* Loose CT (very cellular)
* Loose CT (cellular)
* [Intermediate CT]
* Irregular dense CT (relatively acellular)
* Regular/oriented dense CT (relative acellular)
84
Define CT specialized
Basically, CT proper that has been mineralized
85
3 exampels of CT specialized
* Bone
* Cartilage
* Teeth (dentin, cementum)
86
6 major cell types of cennective tissue
* Mesenchymal cell
* Fibrobast/fibrocyte
* Adipocyte
* Macrophage/histiocyte
* Mast cell
* Plasma cell
87
Most abundant protein of the body
Collagen (20% of all proteins)
88
Structure of collagen fibrils
Triple helix of collagen alpha chains
89
Describe how scurvy is a collagen-related disease
Vitamin C deficiency --\> lack of hydroxylation so no stable triple helix of alpha chain --\> no ordered fibrils
90
Define Ehlers-Danios syndrome
Mutations in colalgen I, III, and V --\> hyperextensive skin, hyper joint mobility and dislocation
91
3 fibres of the ECM
* Collagen (fibrillar)
* Reticular fibres
* Elastic fibres
92
Collagen types that are fibrillar (6)
* I
* II
* III
* V
* VII
* XI
93
Define amorphous ground substances (i.e. of the ECM)
Substances found between fibres that resist compressive forces
94
5 amorphous ground substances of the ECM
* Small proteoglycans
* Large proteoglycans
* Glycoproteins
* Water, metabolites, mineral ions, etc
* Plasma proteins
95
Describe how Marfan's syndrome is an elastin-related disease
Fibrillin-1 gene mutation --\> aortic aneurysm/rupture, lax joints and dislocations, and ectopia lentis
96
Define cutis laxa
Elastin and fibulin-5 mutations, and other elastic fibre degeneration events
97
Describe how mast cells release their secretory granules
After initial sensitization by antigens, degranulation after IgE binding to Fc receptors
