Lecture 12 The Integument (skin) Flashcards
What are the 4 key functions of the skin? Give examples for each function
- Protecting
- injury, infection, UV radiation - Regulating
- temperature, water balance, excrete waste - Sensing
- touch, pressure, vibration, pain, heat, cold (light) - Producing
- vitamin D, nitric oxide
What are the layers of the skin
- Epidermis (kerantinocyte)
- Papillary dermis (fibroblast)
- Reticular dermis (fibroblast)
- Hypodermis
Features of skin (8)
-Langerhans cells (epidermis)
- Melanocyte
- Merkel cell
- sebaceous gland
- Arrector Pili muscle
- hair follicle
- eccrine sweat gland
- apocrine sweat gland
Features of thick skin. Where do you find thick skin?
- increase in sensory receptors
- no hair follicles, arrector pili muscles or sebaceous glands
- find it on palms & soles
Features of thin skin. Where do you find thin skin?
- decrease in stratum spinsom & stratum corneum
- no stratum lucidium
- found on most of the body
What type of epithelium makes up the epidermis
Stratified squamous epithelium
What are the layers of the epidermis called ? (5)
- Stratum corneum
- Stratum lucidum
- Stratum granulosum
- Stratum spinosum
- Stratum basale
Where are epidermal keratinocytes produced and where do they migrate?
-Produced in stratum basale (basal layer)
- migrate upward
What is the uppermost layer of epidermis made of and where are lamellar granules secreted?
- Uppermost layer of keratinocytes are dead, dry, scale like cells
- Upper layer of keratinocytes secrete lamellar granules, forming an impermeable, lipid-containing membrane that serves as a water barrier
How long does it take the epidermis to turn-over?
4 weeks
Where are new keratinocytes produced?
New keratinocytes produced at bottom of epidermis and push the old ones up
Name 4 cell types of the epidermis and the percentage of them in the epidermis ?
- Keratinocytes (90%)
- Melanocytes (8%)
- Langerhans Cell
- Merkel Cell
What do Langerhans cells do ?
Recognise and process microbial invaders
Function of melanocytes
Melanocytes transfer melanosomes to surrounding keratinocytes through their dendrites
What is the ratio between melanocyte and basal cells (keratinocyte at the basal layer) ?
Around 1:4 to 1:20
What is the dermis made up of and where is it located?
-made up of connective tissue mainly collagen (limits flexibility) and elastic fibres (provides flexibility)
- found between epidermis & hypodermis
- dermis is much thicker than epidermis
What are the cell types in the dermis (5)
- Fibroblasts (main)
- Mast cells
- Phagocytes
- Blood vessels
- Adipocytes
What is the Papillary dermis?
Uppermost layer of dermis
What % of the dermis is the papillary dermis ?
20%
What is papillary dermis made up of ?
Areolar connective tissue
Fine collagen & elastic fibres
What do dermal papillae contain?
- capillary loops
- nerve endings (Meissner corpuscles; sensitivity to light touch)
- free nerve endings
What % of the dermis does the reticular dermis make up?
85%
What is the reticular dermis made of?
Irregular dense connective tissue
Thick collagen/elastin fibres
Most of skins strength & flexibility
What does reticular dermis contain?
- Epidermal appendages (hair,sweat & sebaceous glands)
- Nerve endings (Pacinian corpuscles; detects vibrations & pressure)
What are 4 accessory skin structures?
- Hair
- Sebaceous (oil) glands
- Sweat glands
- Nails
What are the layers of the hair shaft ? (3)
- Inner layer - medulla - soft core
- Cortex - main bulk & pigment
- Cuticle - outer protective layer
(4. Root sheath - Outer layer - connective tissue sheath )
What is hair made up of ?
- Hair shaft
- Root sheath
- Hair buldge
- Dermal papilla
What is hair shaft made from? (2)
Keratinocytes
Keratin
What does bathe hair bulge contain?
Stem cell population
What does the dermal papilla contain in hair shaft?
Specialised mesenchymal cells
What does the near dermal papilla contain in hair shaft?
Melanocytes
Blood vessels
What is the shape of sebaceous (oil) glands and what are they usually connected to?
- simple branched acinar gland
- usually connected to hair follicles
What is the function of sebaceous gland?
Secrete oily sebum which:
- moisturise and protect skin & hairs
- antibacterial
What can too much sebum/inflammation cause?
Acne
What are the shape of sweat glands?
Simple coiled tubular gland
General functions of sweat glands (3)
- Produce body odour
- Excrete waste
- Regulates body temperature
What are the 2 types of sweat glands?
- Eccrine
- Apocrine
Function of eccrine sweat glands
- secrete sweat onto body surface
- which regulates body temperature
What does sweat contain & how much is produced per day?
Contains:
- water
- sodium ions
- chloride ions
- urea
- uric acid
- ammonia
- amino acids
- glucose
- lactic acid
- produce 600ml per day
Function of apocrine sweat glands
- Merocrine secretion (not apocrine secretion)
- Body odour
- Secrete ‘thick’ sweat into hair follicle ducts
What does nail consist of ?
Dead, tightly compressed cells packed with keratin
Where do nails grow from?
Grow out of nail root - an epidermal fold not visible from surface
