3.4 Flashcards
(28 cards)
What is the integument?
Epithelium + connective tissues
What is the function of the integument?
Protective (UV irradiation, infection, physical injury
Immunity
Sensation (touch, pain, pressure, temperature)
Thermoregulation
Water balance
Waste excretion ( urea, uric acid, ammonium)
Vitamin D production
What are the features of the epidermis?
- Stratified squamous keratinised epithelium
- keratinocytes
- avascular
- keratinised
- basement membrane: attach to connective tissue, semipermeable barrier.
What are the 5 layer of the epidermis?
- Stratum corneum
- stratum lucidum
- stratum granulosum
- stratum spinosum
- stratum basal (e)
What are features of the stratum basal(e)
- germinating layer
- Continuous layer of single epithelial cells
- Constantly dividing
- basal keratinocytes (stem cells)
- tightly bound to the underlying connective tissue (dermis)
What are features of spinosum?
The prickle cell layer: spring projection of desmosome microfilaments.
Several layers
Cells are head together tightly
Strength resilience and flexibility
What are features of stratum granulosum?
Thin granular layer
Keratinocytes: accumulate granules of keratin as they migrate towards the surface. Secret keratin into the extracellular space.
What are features of stratum lucidum?
A thin clear layer of cells (starting to die, filled with an intermediate form of keratin (eleidin)
Only seen on thick skin.
What are features of stratum corneum?
Surface layer
Multiple layers of dead cells: flattened cells, no nuclei, no organelles, embedded in keratin.
Water proof barrier
Desquamation: cells shed due to wear and tear.
Very thick in thick skin
What is keratinisation?
Keratinocytes move towards the skin surface
Keratinocytes production increases
Cells flatten out
Nuclei disappear (stratum granulosum)
Layer of keratinised cells form stratum corneum.
What occurs during skin regenerations?
28 day cycle
Superficially cells lost from the cornified layer
Replaced by new cells formed in the basal layer
Describe thin skin
Cover most the body
Thin epidermis
Thin stratum corneum
No stratum lucidum
Describe thick skin
Covers palms and soles
Thick stratum corneum
Contains a stratum lucidum
No hair
What are the four cell types of the epidermis?
Keratinocytes
Langerhans cells
Merkel cells
Melanocytes
What are features of keratinocytes?
Predominant cell type
Provide protection and an environmental barrier
Produce keratin
What are features of langerhans cells?
Cells of the immune system
Antigen presenting cell (dendritic cell, long cytoplasmic processes)
Derived from bone marrow
Largely reside in the stratum spinosum
What is the langerhans cells mode of action?
Ingest foreign invading organisms
Digest them
Present antigens on the surface of the cell membrane
Migrate to lymph nodes
Warn the immune system of the invader
What are features of melanocytes?
Produce melanin (natural pigment, protects the DNA from photosynthesis-damage)
Reside in stratum basale
What is melanin’s mode of action?
Secreted by melanocytes
Ingested by keratinocytes (endocytosis)
Moved to apec to protect the nucleus
Can exposure induces melanogenesis (tan)
What are features of Merkel cells?
Mechanoreceptors (sensory structures)
Respond to stretch or torque
Present in highly sensitive skin
Long processes
Interact with cells across different layers of the skin
Reside in stratum basale
How are the epidermis and dermis attached?
Corrugated interface (border of epidermis and dermis)
Epidermal ridges (extend down into the dermis)
Dermal papilla (rise up into the epidermis)
Large surface area at the junction (ensures integrity of the joining of the two layers
What are the features of the dermis?
Two layers
Papillary dermis (thin layer just below the epidermis, loose connective tissue)
Reticular dermis (dense connective tissue, thick collagen fibres, provides strength)
What are the features of the hypodermis?
Structure: layer of adipose tissue, underlines the skin
Function: insulation, energy storage, cushioning
What are features of nerves?
Sensing: temperature, touch, pain, pressure
High density of nerve endings
Different nerve fibre for each sense
