Lecture 18 Flashcards
What is the skin also referred to as?
the integumentary system
What is the skin?
Largest organ in the body
- 12-15% body weight and 1.6-1.8m2 of surface area
What are the main functions of the skin?
Protection
- against impact, chemicals, infection…
(e.g.) burns: issue is a result of damage since the body is prone to toxins and infections
Temperature maintenance
- regulates heat gain and loss
Synthesis and storage of nutrient:
- vitamin D3 synthesis
Sensory reception
- the skin contains receptors that relay information to the nervous system
Excretion and secretion
- excretes salt, water; secrete mile (mammary glands)
Visual part of body:
- implications on social life and psychological health (pale = anaemia)
What forms the integumentary system?
Skin+accessory structures
What are the three layers of the skin?
Epidermis: has various layers
Dermis: where you have various tissues and sweat glands, hair cells nails etc
Hypodermis:
What are the accessory structures of the skin?
Glands (2 sweat of glands, sebaceous gland), hair and nails
What are the two types of skin?
Thick skin - palm of hands and feet, fingertips - no hair - 5 layers (called stratum) Thin skin - rest of the body - 4 layers
What does stratified mean?
has layers
What is squamous cells?
Contain dead cells to be removed and has active mitotic cells
What are keratinized cells?
keratinocytes produce keratin in epidermis
Skin is one of the few systems that can generate. What are other examples?
Liver, skeletal muscles
(more friction causes faster regeneration)
How long does self-regeneration last?
2-4 weeks
How often does self-regeneration occur?
life-time
Where are keratinocytes born and where do they go?
Keratinocytes are born in the lower layer and migrate upward during their life
What are the three cell types of Stratum Basale?
Keratinocytes, melanocytes, tactile cells
What are keratinocytes?
Majority are mitotic
Basal lamina separates keratinocytes from extracellular matrix (ECM)
When keratinocytes are in contact with ECM, it divides
What are melanocytes?
Provide skin color with beta-caroten Combinations of pigments form sin color - eumelanin: brown insoluble pigment - phenomelanin; red soluble pigment (e.g.) Fair skin - pigments in granules in superficial layer of epidermis Dark skin - pigments accumulate in cell layers of epidermis Tactile cells (or Merkel) - connected to sensory nerves and participate to the sense of touch - can be target of cancer
What is the stratum spinosum?
Thickest layer of epidermis, contains keratinocytes and up to 800 dendritic (Langerhans) cells
per mm2
What is the stratum spinosum composed of?
Keratinocytes (layer keratin content)
- still mitotic (especially the deeper ones
- more flattened shape
- provide elasticity to skin
- detached from basement membrane, and migrate upward
Subset of dendritic type cells
- Langerhans
- mediating immune response to infective agent
What is the Stratum granulosum?
Last layer of epidermis to have cells containing nuclei
What does the stratum granulosum contain?
Contains 3-5 layers of flat keratinocytes
Keratinocytes
- post-mitotic
- make large amount of keratin and a glycolipid
- - glycolipids
—– lipid layer
—– water resistance
—– prevent water loss and absorption from body
—– high content of granules
—– prevent diffusion beyond layer (beyond layer - dead cells only)
Keratin forms filaments that are durable
What is the stratum lucidum?
Exists only in thick skin Translucent - keratinocytes - - densely packed - - contain no nuclei or organelles
What is the Stratum corneum?
Most superficial layer of the skin
- 15-30 layers of dead, keratinized cells
- high lipid content - permeability barrier
- cells at the surface flake off
- rate depends on level of friction
Which is thicker, the dermis or the epidermis?
the dermis
