The integumentary system Flashcards
What is the integumentary system?
The skin system, sensory nerves & accessory organs:
- hairs
- nails
- cutaneous glands (sweat, sebaceous mammary)
What % does the largest organ in the body (skin) make up of the total body weight?
12-15%
What is the use of skin?
- barrier to external
- insight to internal health
How does the integumentary system provide an insight into internal health?
shows blue veins if the heart isn’t pumping hard enough
What are the 2 structures of the skin?
- Epidermis (uppermost) epithelia layer
- dermis
What is thicker - dermis or epidermis?
dermis
How thick is the dermis?
0.2mm - 2mm
What do fibroblasts produce?
ECM (extracellular matrix) - mainly collagen
What are the 2 layers of the ECM (extracellular matrix)?
- papillary layer
- reticular layer
What is in the papillary layer?
thin loose connective tissue region (areolar) - mobility of leukocytes, mast & macrophage cells.
What is the function of the papillary layers?
Mobility of leukocytes, mast & macrophage cells.
What is in the reticular layer?
thick dense irregular connective tissue layer - less cells + adipocyte clusters
Which has more cells the papillary layer or reticular layer?
papillary layer
What type of clusters can be found in the reticular layer?
Adipocyte clusters
What are the accessory organs of the integumentary system?
Hair, nails, oil + sweat glands
What is the use of having a rich layer of blood & lymphatic vessels, including arteriovenous anastomoses in the accessory organs?
thermoregulation
What does the dermal (epidermal boundary look like)?
‘wavy’ boundary of finger-like projections increasing connection (interdigitation)
What do dermal papillae create?
raised areas - e.g. fingerprint
What facilities nerve fibres reaching close to the surface in highly sensitive areas?
Tall dermal papillae
What type of epithelium is found in the epidermis?
Keratinised stratified squamous epithelium
Describe the protein content in the upper layers of the epidermis
there is a high protein content in the upper layers of the epidermis
Describe the layers of the epidermis (top to bottom)
stratum corneum
stratum lucidum (translucent)
stratum granulosum
stratum spinosum
stratum basale
stratified
What are the 2 skin types?
- Thick skin
- Thin skin
Describe what thick skin can be found
- Palms (fingertips)
- Feet - no hair (glabrous)
How many layers (strata) does thick skin have?
5
Where is thin skin found?
the rest of the body (non-glabrous - areas with hair)
How many layers does thin skin?
4
Describe how many blood vessels are found in thin skin?
Lacks blood vessels - diffusion from underlying connective tissue
What is another name given to the stratum basale?
germinativum
What are the 3 type of cells found in the stratum basale?
- keratinocytes (most prevalent)
- melanocytes
- tactile/Merkel cells
What is the role of keratinocytes?
they are mitotically active in touch with BM (stem cells)
what is the role of melanocytes?
gives skin colour - pheomelanin/eumelanin - brown insoluble pigment
- protects skin from UV damage
What is the role of tactile/Merkel cells?
connected to sensory nerves (sense of touch)
What colour pigment is pheomelanin?
red/yellow pigment
What colour pigment is eumelanin?
brown/black pigment
What 2 pigments make up skin pigmentation?
melanin +
- carotene pigments (orange-yellow) - heels/corns of the feet
- blood perfusion + O2 content - haemoglobin (red)
What are melanosomes?
organelles responsible for the synthesis, storage & transport of melanin
What is usually the thickest layer in the epidermis?
stratum spinosum
What does the stratum spinosum produce?
keratin filaments (flatten)
What structures strongly link keratinoctyes?
desmosomes?
What is the advantage of having tight junctions within the stratum spinosum?
ensures water retention of skin
What is the function of the dendritic cells present in the stratum spinosum?
they are immune cells
How many layers of keratinocytes do stratum granulosum?
3-5 layers
What do the dark-staining granules found in stratum granulosum bind to?
bind to cytoskeleton (keratin precursor)
What type of vesicles are produced in the stratum granulosum?
glycolipid-filled vesicles (lamellar bodies/granules) - spread over cell surface - waterproof barrier between Stratum spinosum
Describe the cells in Stratum corneum
most part are dead and high in proteins & don’t contain nucleus
How many layers does the Stratum corneum have?
30
What are the 2 parts of the Stratum corneum?
- stratum disjunctum
- stratum compactum
What is the most superficial layer of the Stratum corneum made of?
15-30 layers of flattened corneocytes/squames
What are squames?
enucleated terminally differentiated dead keratinocytes
What is the role of Stratum disjunctum in the stratum corneum?
contains corneodesmosomes which regulate desquamation
What is the role of the stratum compactum in the stratum corneum?
focuses on cohesion
What are the keratins in the stratum corneum enclosed in?
insoluble amalgam of cross-linked proteins
What layer of the epidermis are nails derivatives of?
stratum corneum
What are nails formed of?
dead scaly cells that are densely packed with “hard” keratin fibres.
How are new cells added to nails?
mitosis in the nail matrix
What is an underlying health issue that could be indicated as a result of having flat or concave nails?
iron deficiency
What is an underlying health issue that could be indicated as a result of having clubbed nails?
long term hypoxemia (low blood oxygen levels)
What are the 3 names given to hair (pilus) throughout its lifetime)?
languo –> vellus –> terminal androgenic
Describe how hair forms?
hair bulb grow around bud of vascular connective tissue - dermal papilla
What part of hair is mitotically active, whilst the remainder is dead?
hair matrix
What are the 3 layers in hair?
Medulla - loosely arranged cells
Cortex - keratinised cuboidal cells
Cuticle - surface layer of scaly cells
What are the 5 types of skin gland types?
- eccrine/merocrine (sweat glands)
- apocrine sweat glands
- holocrine sebaceous glands
- ceruminous glands (external ear - wax)
- mammary glands (females)
What cells are involved in holocrine secretion?
sebocytes
What are sebocytes?
differentiated epithelial cells accumulate lipids, eventually rupture to release sebum
How many microflora does skin have?
1000 species
How does skin act as a physical barrier?
cross-linked keratin layer on keratinocyte scaffold (cuts/burns/vectors/breach)
How dies skin act as a biochemical barrier preventing water loss?
- mildly acidic (pH 4-6)
- contain sebaceous gland seboctyes (sebum)
- C6H can inhibit induction of antibiotic resistance
What cells are used in skin to act as an immunological barrier?
Epidermal Langerhans Cells (LC)
What layer of the Epidermis are Epidermal Langerhans Cells (LC) located?
stratum spinosum (able to self-renew)
How does skin process antigens?
- migrate to lymph nodes for antigen presentation
- present antigens to skin lymphocytes
What can be found in dermal cells?
- macrophages + monocytes
- mast cells
- eosinophils
- neutrophils
- B + T lymphocytes
- may have role in tissue remodelling, repair & proliferation
Describe the process of Vitamin D synthesis
- increases intestinal absorption of calcium
Why is calcium homeostasis?
bone development + maintenance
What type of hormone is vitamin D?
fat-soluble hormone
What type of receptor allows the synthesis of vitamin D?
Nuclear receptor
What photochemical reaction is necessary for the synthesis of vitamin D?
UVB radiation
What 4 things are involved in thermoregulation?
- receptors
- insulation (piloerection)
- sweating
- vasodilation/vasoconstriction
What volume of skin blood dissipates heat at rest?
250ml/min
How many kcal an hour is required for thermoregulation?
80kcal/hr
Where are central warm + cold receptors located?
preoptic anterior hypothalamus
Between what two blood flows does countercurrent heat exchangers occur?
arterial & venous blood flow
What type of skin is arteriole out anastomoses found?
Apical skin
How does a reduction in core temperature lead to a reduction in blood flow?
reduction in core temperature = increase in sympathetic tone = reduction in blood flow
How does an increase in core temperature lead to a increase in blood flow?
increase in core temperature = decrease in sympathetic tone = increase in blood flow
How is non-apical skin thought to act via sympathetic nervous system (SNS) to affect ACh release?
eccrine sweat glands –> vasoactive molecules –> relax VSMC –> increase in perfusion + heat loss