Skin and Associated Glands Flashcards
What does the skin protect against
Physical barrier to bacteria
Excessive dehydration
UV radiation
drug and chemical penetration
What are the functions/roles of the skin
Protection Sensation Thermoregulation Metabolic functions Contributes to physical and sexual identity
How does the skin contribute to metabolic functions
Adipose tissue = major store of energy
Vitamin D synthesised in epidermis
What are the 3 major layers of the skin
Epidermis
Dermis
Hypodermis
What are some features of the dermis layer
dense irregular CT: highly vascular and many sensory
receptors
What are some features of the hypodermis layer
loose CT contains adipose tissue
Name some epidermal appendages
Hair follicles
Sweat glands
Sebaceous glands
Nails
What kind of epithelium is in the epidermis
Stratified Squamous Epithelium
What is the major cell type in the epidermis
Keratinocyte
What are the 4 main layers of the epidermis
- Stratum basale (basal layer)
- Stratum Spinosum (spinous layer)
- Stratum granulosum (granular layer)
- Stratum corneum (cornified layer)
What is the stratum lucidum
Only in extremely thick skin, homogenous between SG and SC
Describe a keratinocyte and what does it do
most abundant epithelial cell in epidermis, lots of intercellular junctions like desmosomes and adherent junctions
Produce keratin
What is the most abundant protein in the stratum corneum
Keratin
Where besides skin is keratin found
Hair and nails
What kind of proteins are keratins and what defines soft vs hard keratins
Fibrous structural proteins
S-S bonding defines hard vs soft
What cells are found in the stratum basal
Stem cells Transit Amplifying (TA) cells
What does the stratum basale sit on
the basement membrane
Can Transit Amplifying cells undergo cell division
TA limited cell division before undergoing terminal differentiation
What is keratinisation
The migration of keratinocytes, which become tightly bound together by desmosomes, from the basal to the corneal layer
What gives the stratum spinousum a prickly appearance
The numerous desmosomes
What is the stratum granulosum characterised by
Large, numerous basophilic granules of keratohyalin
keratinocytes from the underlying stratum spinosum migrate here and become known as granular cells here
Gives 2 examples of keratohyalin
- Filaggrin
- Involucrin
What is synthesised by the stratum granulosum
Synthesises glycoprotein granules
Describe the cells of the stratum corneum
- Terminally differentiated
- fused flattened cells without organelles and filled with mature keratin
- Thick cornified cells envelope under the plasma membrane
- cells are dead
What is the main function of the stratum corneum
main protective barrier of the skin
What are the 2 layers of the dermis
- Papillary (vascular/nervous
papillae) - Reticular (main fibrous bed,
dense irregular CT)
Describe the general features of the dermis
- Complex mix of
macromolecules - Many blood vessels
What are the main functions of the dermis
- Provides strength and elasticity to skin
- Acts as a support for epidermis
Name the features the papillary dermis and what type of collagen is in it
- Superficial layer beneath epidermis
- Contains many blood capillaries (vascular papillae)
- Loosely packed
- Type III Collagen
What fibres are found in the reticular dermis
Closely packed Type I collagen and elastin
What is the main role of the reticular dermis
- Provides much of mechanical strength of skin
Is the reticular dermis hydrophobic or hydrophilic
Hydrophilic and flexible
What is the ground substance in the reticular dermis
- an amorphous matrix that embeds the collagenous and elastic fibres and skin appendages
Name 3 GAGs found in the ground substance of the reticular dermis
- Hyaluronic acid
- Dermatan sulfates
- Chondroitin sulfates
What is the most abundant cell in the dermis
Fibroblast
What is the function of fibroblasts in the dermis
Repair
What do fibroblasts synthesise in the dermis
- Collagen
- Elastin
- Proteoglycans
Name some skin glands
- Eccrine sweat gland
- Apocrine gland
- Sebaceous gland
What are the 2 types of hair follicle
Vellus - body hair
Terminal - scalp and secondary sexual hair
What is the dermal papilla
root of the hair follicle
What in the hair matrix produces hair
keratinocytes
What does the bulge of the hair follicle contain
Hair follicle stem cells
What cells is the root of the hair follicle made of
3 inner concentric epithelial cells to form the hair shaft
2 outer concentric epithelial forms epithelial sheath
What are the 3 main phases of the hair growth cycle
- Anagen-active
- Catagen-regressive
- Telogen-resting
What kind of gland are sebaceous glands and what do they do
Exocrine
Mature sebocytes contain sebum
Cell ruptures and sebum released into sebaceous duct and onto skin to lubricate skin and hair
Gives you acne
What is the main role of the eccrine sweat gland
thermoregulation
What are the 2 main components of the eccrine sweat gland
Excretory duct - two layers of smaller cuboidal cells
Compact secretory coil - single layer of large cuboidal/columnar cells
What is the largest sweat gland and where are they found
Apocrine sweat glands
Axilla (underarm) and pubic region
Describe the secretion of apocrine sweat glands and when do they become functional
- Release volatile milky, viscous fluid
- Secretion is odourless, Body odours, Broken down on skin by bacteria
- Do not become functional until puberty
Where are melanocytes and what do they do
In epidermis, on basement membrane
- Produce melanin in melanosomes
- Melanosomes injected into keratinocytes
- Protect against UV
Name the 2 types of melanin and what colour they are
Eumelanin - Brown-black
Pheomelanin - Red-brown
Where in the epidermis are merkel cells and what is there function
- Stratum basale
- Sensory perception
Where in the skin are mast cells and what is there function
Dermis
- Immune response
- Secretes histamine
