6. Integumentary system Flashcards
What are the 3 key layers of the skin?
Outer layer (epidermis)
Middle layer (dermis)
Deepest layer (hypodermis/subcutaneous layer)
Description of the hypodermis (subcutaneous layer).
Not classified as a layer of skin
It is a layer of fat (adipose tissue) which provides protection as insulation
It connects the dermis to muscle and bone
What does the dermis contain?
Elastic fibres, reticular fibres, collagen, hair follicles, sweat glands, nerve endings, sebaceous glands and blood vessels.
What is the function of the dermis?
Provide strength and flexibility.
Epidermal nutrition - contain blood vessels which carry nutrient to the epidermis and remove waste products.
What is the structure of the epidermis?
Most superficial (outer) layer of skin.
Avascular (no blood supply).
Main cell content: keratinocytes, melanocytes, langerhans and merkel cells.
Subdivided into 5 layers - basal layer is the deepest.
Function of keratin.
Protein which makes skin strong, tough and waterproof.
Function of melanin.
Pigment, more active melanocytes = darker hair + skin.
Shield skin from UV light.
Function of langerhan cells.
Protect against viruses, bacteria and fungi.
Breakdown pathogens.
Help T lymphocytes to recognise antigens.
Function of merkel cells.
Have mechanoreceptors which detect pressure on skin.
Why do we shed dead skin?
More cells are produced in basal layer, older cells get pushed through to surface. As they are moving further from the blood supply they end up dying.
What are the functions of the skin?
Regulates temperature:
~ vasoconstriction/vasodilation (opening and closing of vessels).
~ sweating
~ piloerection (muscles pull hair upright, reduce heat loss).
Protection:
~ physical barrier
~ prevents water loss - sebum
Cutaneous sensation: receptors within the skin respond to temperature, touch, pressure and pain.
Synthesise vitamin D
Excretion of waste products and sebum
How do pressure sores occur?
When the pressure of bone on hard surface compresses the blood supply. In the case the blood supply does not restore it can lead to permanent damage.
Cancers of the skin.
- Malignant melanoma - common, caused by UV damage, increasing incidence in young people.
- Non melanoma - Basal cell carcinoma (75%), Squamous cell carcinoma (20%), Merkel cell carcinoma, kaposi sarcomas, cutaneous lymphomas. These are most common in older generations.
Overview of hair (keratin)
Follicle - where hair grows +is held in position
Shape of hair stands determines curly/straight
Hair is important for heat preservation, sebum production, preventing friction and protection.
Overview of structure nails
Main exterior is called nail plate (layers of keratin)
Nail bed (sterile matrix) - provide smooth surface for nail to grow over.
Eponychium (cuticle) - layer of skin that extends from the finger over the nail plate.
What is the function of nails?
Fine motor movement and add strength to grip.
