Wk 5: Integumentary (Skin) Flashcards
What kind of epithelia in skin
Skin consists of stratified squamous epithelium
Metaplasia
The transformation of an epithelium into another type of epithelium
Dysplasia
The enlargement of a tissue by proliferations of cells of an abnormal nature
Adenocarcinoma
Malignant tumour formed from glandular structures in epithelial tissues
5 functions of skin
- Protection
- Thermoregulation
- Sensation
- Secretion/excretion
- Synthesis of Vit D
What are the 3 layers of skin
- Epidermis - outer
- Dermis - middle
- Hypodermis - inner (subcutaneous layer)
What is the primary structure of the epidermis
Keratinocytes
What is the primary structure of the dermis (2)
- Connective tissue
- Dermal capillaries
What is the primary structure of hypodermis (2)
- Loose connective tissue
- Adipose tissue
What other cells are found in the epidermis
- Keratinocytes
- Melanocytes
- Merkel cells
- Langerhans
3 functions of epidermis
- Maintenance of fluid & electrolyte balance
- Protection from UV light (mediated through melanocytes)
- Sensory (Merkel cells) & immune function (Langerhan cells)
What are the 4 layers of epidermis
- Stratum corneum
- Stratum granulosum
- Stratum spinosum
- Stratum basale
What is the thickest layer of the epidermis
The stratum corneum
What does the stratum corneum contain
- Dead cells called corneocytes
- Keratin
(Corneocytes dead in the sense that they have no nucleas but do contain large amounts of keratin, corneocytes are the final stage of differentiation of keratinocytes)
What do the granules in the stratum granulosum contain & for what purpose
Granules contain glycolipids.
For waterproofing.
What are the keratinocytes linked by in the stratum spinosum
Desmosomes
What do cells in the stratum spinosum contain
Cells contain bundles of prekeratin
What does the stratum basale consist of
- Stem cells
- Younger keratinocytes
There is a 5th layer of the epidermis found only in thick skin, what is this called
Stratum lucidum
Where are melanocytes found in the epidermis & what is their function
- Found in the stratum basale
- They scavenge free radicals to protect against UV (damage to nucleus = uncontrolled proliferation
Where are merkel cells found in the epidermis & what is their function
- Found in the stratum basale
- Function as sensory receptors for touch
Where are langerhans cells found in the epidermis & what is their function
- Mainly found in the stratum spinosum
- Function as a type of macrophage - engulf pathogens, become antigen presenting cells, release signalling molecules that attract cells of immune system to area of invading pathogen
What is basal cell carcinoma derived from
Derived from basal keratinocytes
What is squamous cell carcinoma derived from
Derived from mature differentiated keratinocytes
What is malignant melanoma derived from
Derived from melanocytes - uncontrolled proliferation
What are the 2 layers of the dermis
- Papillary dermis
- Reticular dermis
What does the papillary dermis contain & what is the function of these
- Includes the dermal papilla which project into the epidermis
- These increase contact area preventing epidermal detachment
Components of the dermis
- Connective tissue
- With fibroblasts
- Macrophages
- In a collagen & elastin matrix
- Large numbers of capillaries, nerve endings & lymphatics
What are the specialised structures found in the dermis
- Sweat glands
- Apocrine glands
- Sebaceous glands
- Hair follicles
What are the two types of sweat glands
- Eccrine glands
- Apocrine glands
Where are eccrine glands found
Almost everywhere
Where are apocrine glands found
Mainly in axilla & anogenital area
What’s the difference between eccrine & apocrine glands
- Secretions in apocrine glands contain more fat & protein than eccrine glands - bacterial breakdown of this is the basis of body odour
- Secreted onto hair follicles, not skin
What do sebaceous glands secrete
Oily substance called sebum
What are sebaceous glands activated by
Androgens
Functions of the hypodermis
- Connects skin to underlying fascia of bones & muscles
- Insulator
- Shock absorber
- Protection
Structure of hypodermis
- Well vascularised, loose, areolar connective tissue & adipose tissue