Lecture 12 Skin Flashcards
1
Q
Largest organ of the body
A
- skin
- 15-20% of body mass
- hair, nails,
2
Q
4 functions of skin
A
- protection
- sensation
- thermoregulation
- metabolic functions
3
Q
Protection
A
- from UV, mechanical, chemical, and thermal insult
- prevents dehydration; provides physical barrier to microorganisms
4
Q
Sensation
A
- largest sense organ of body
- contains receptors for touch, pressure, pain, and temperature
5
Q
Theromoregulation
A
- insulation via hair and SQ fat; heat loss facilitated by sweat glands and dermal capillary network
6
Q
Metabolic functions
A
- energy stored in subcutaneous fat
(primarily as triglycerides); - Vit D synthesized in skin via sunlight
- Maintains homeostasis; excretory function (sweating) immune defense
7
Q
Skin has 3 main layers
A
- epidermis
- dermis
- hypodermis (subcutaneous)
8
Q
Epidermis
A
- consists of keratinized stratified squamous epithelium
- varies in thickness from <1 mm to >5
9
Q
Cells of epidermis
A
keratinocytes
10
Q
Thick skin
A
- palms of hands and soles of feet
- thick highly keratinized layer
- lacks hair (glaborus)
11
Q
Think skin
A
- thin keratinized epidermis
12
Q
Epidermis
A
- lack blood vessels – do not penetrate basement membrane
13
Q
Where is the skin thickest?
A
- if dermis is included it is the back of the neck
- predators try to attack prey there
14
Q
Epidermis supplied and nourished by blood vessels in the underlying (subadjacent) ______
A
dermis
15
Q
Dermis
A
- composed of dense irregular collagenous connective tissue (type 1 collagen)
16
Q
What happens when the elastic fibers are damaged from sunlight?
A
- sagging or “aging)
- loss of skin tone
17
Q
Is the dermis vascular?
A
- Yes, highly vascular and contains many sensory receptors
18
Q
What are the 2 layers of the dermis?
A
- superficial papillary layer
- deep reticular layer
19
Q
Papillary layer
A
relaticely thin- interdigitates with epidermis
- corrugations increase surface area for attachement, prevent shear and mechanical abrasion
20
Q
Epidermal ridges
A
- epidermal projections into epidermis
- large dermal ridges in thick skin called finger prints (dermatoglyphs) unique to individual
- form basis of study of dermatoglyphics
21
Q
What is the part of the dermis that is unique to individuals?
A
- dermatoglyphs
22
Q
Epidermal ridges (rete ridges)
A
- epidermal projections into epidermis
- large dermal ridges in thick skin called finger prints (dermatoglyphs) unique to individual
- form basis of study of dermatoglyphics
23
Q
What is the part of the dermis that is unique to individuals?
A
- dermatoglyphs
- dermal ridges
- unique to identical twins
24
Q
Dermal ridges
A
- project into epidermis
- finger prints ( dermatoglyphs)
25
What is the thickest layer of the dermis?
- the deep reticular layer
| - also less cellular
26
What layer of the dermis contains hair follicles, sweat and sebaceous glands?
- the deep reticular
27
What does the retiular layer of the dermis interdigitates with
- underlying hypodermis (subcutis)
| - thick collagen bundles and elastin fibers in reticular layer form lin
28
thick collagen bundles and elastin fibers in reticular layer form lines of tension called
Langers lines
29
When you are making skin incisions what lines should you make your incisions parallel to?
Langers lines
30
What does making skin incisions parallel to langers lines do?
- makes them heal with less scarring
| - slicing in between collagen bundles instead of across
31
What is the deepest layer of the dermis?
- hypodermis
32
What is the hypodermis composed of?
- loose irregular connective tissue and adipose tissue
| - (subcutis = superficial fascia= adiposus)
33
Three vascular plexi of skin
- superficial subpapillary plexus
- deep cutaneous plexus
- deeper subcutaneous plexus
34
Where is the subpapillary plexus located?
- at the junction of the paillary and reticular layers
35
Where is the cutaneous plexus located?
at the junction of the reticular layer and hypodermis
36
Where is the subcutaneous layer?
- deep within the hypodermis
| - largest of three plexi
37
What are the vascular plexi used for?
- thermoregulation
38
Where are these plexi commonly found?
- in fingertips and ears
| - associated with AV shunts containing glomus bodies
39
What are these glomus bodies made up of?
- thickened regions of smooth muscle in wall of arterioles surrounded by connective tissue
40
When its cold what do these glomus bodies do?
- bypass capillary bed and re route blood from arterial to venous circulation
- why you cant feel your fingers
- help maintain internal body temp by bypassing them
- could cause frostbite
41
Does the epidermis stop growing?
- No continuously grows and is replaced
42
How long does it take for skin cells to travel from deep germinal layer, mature, and be sloughed from superficial epidermis?
- 25-50 days
43
What is the disease where keratinocyte maturation only takes 1 week?
- psoriasis
44
What are some features of psoriasis?
- absence of a granular layer and abnormal keratohyaline and tonofibrils
45
What is the deepest layer of epidermis?
- stratum basale = stratum germinativum
46
Stratum basale
- mitotic layer consisting of cuboidal germinal cells that rest on basement membrane adjacent to the dermis
- these cells are bound to basement membrane by hemidesmosomes
47
Hemidesmosomes
- attach to underlying dermis via anchoring filaments and microfibrils
48
Stratum spinosum
- prickle cell layer- cells look spiny
49
What is the thickest layer of epidermis in think skin?
- stratum spinosum
50
What type of cells make up the stratum spinosum?
- polyhedral cells with prominent intercellular bridges (desmosomes)
- numerous cytoplasmic processes and lateral folding of cell membrane
51
Why would overstaining be useful when looking at stratum spinosum?
- can see lines between cells
| - junctions called desmosomes (intercellular strructure)
52
What is the predominant cell product of stratum spinosum?
- cytokeratin
53
What does the cytokeratin do?
- forms tonofilaments, which aggregate into larger tonofibrils that anchor onto desmosomes
54
How many types of keratin to humans produce?
- 54 alpha keratin
55
B keratin
- tougher
| - birds
56
Stratum granulosum
- granular cell layer
57
What is stratum granulosum charcterised by?
- cells containing basophilic kerathohyline granules
58
What are keratohyaline granules?
- non-membrane bound electron dense granules
59
Keratinization
respresents interaction between keratohyaline granules and tonofibrils
60
How is keratinization initiated?
- release of lyposomal enzymes
61
What does releasing lyposomal enzymes do?
- causes rupture of keratohyaline granules and polymerization of their contents
- this forms a matrix for tonofibrils of cytokeratin --> amorphous mass of mature keratin
62
Release of lysosomes also leads to
cell death
63
What happens when keratinocytes mature?
they die and lose nuclei
64
Keratinosomes
- membrane boud structures that contain glypolipids
| - provide waterproof coat for skin cells
65
Cells of granular level
- mature to form waterproof layer of keratinized cells, with glycolipid coating on surface of epidermis
66
Stratum lucidum
- present only in thick skin
| - homogenous compact layer of enucleate cells between stratum granulosum and stratum corneum
67
What is the most superficial layer of the epidermis?
- stratum corneum (cornified layer)
68
Squames
- present in stratum corneum
| - flattened, enucleate, dead cell remnants
69
What is the squames made up of?
- primarily of soft keratin (acts as hydrophobic barrier, prevents desiccation)
- waxy coating
70
What does the soft keratin do?
- acts as a hydrophobic barrier - prevents desiccation
71
dead cells are continuously exfoliated
- slough them off
72
In females, exfoliated cervical epithelial cells routinely examined in Pap smear, why?
- to detect cervical cancer
| - pap smears taken from cervix
73
Dogs tracking criminals
- smelling odors attached to exfoliated skin cells
74
Vet practices
- only want to ship dog if they are receptive
75
Common skin tumors
- squamous cell carcinoma
- basal cell carcinoma
- melanoma
76
Where are squamous cell carcinomas and basal cell carcinomas derives from?
epithelial cells
77
Where are melanomas derived from?
- melanocytes
