WEEK 10: 10.1 Introduction to Body Defences Flashcards
(46 cards)
What are the 7 key functions of the integuement (skin)
Protection (UV, infection, injury)
Immunity
Sensation (touch, pain, pressure)
Thermoregulation
Water balance
Waste excretion
Vit D production
What are the different skin layers?
Superficial- epidermis
dermis - connective tissue
hypodermis - adipose
What is the epidermis?
it is an epithelial layer - stratified squamous keratinised (covered in keratin) epithelium
What is the predominant cell type in the epidermis
keratinocytes
What does the epidermis consist of?
a basement membrane
attachment to connective tissue
semipermeable barrier
What are the 5 layers of the epidermis
Stratum corneum (top)
Stratum lucidum
Stratum granulosum
Stratum spinosum
Stratum basal (bottom)
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Describe the stratum basal
It is a continuous layer of single epithelial cells, and is described as a germinating layer (keratinocytes start to grow)
How is the stratum basal bound to the dermis
it is tightly bound to the underlying connective tissue (dermis)
Describe the stratum spinosum
It is described as ‘the prickle cell layer’, consists of spiny projections of desmosome microfilaments
Consists of several layers, quite thick
What’s the function of the stratum spinosum
cells are held together tightly to provide strength, resilience and flexibility
Describe the stratum granulosum
It is a thin granular layer consisting of keratinocytes that accumulate as granules of keratin as they migrate towards the surface
What is the function of the stratum granulosum
To secrete keratin into extracellular space
Describe the stratum lucidum
It is a thin, clear layer of cells, starting to die and filled with an intermediate form of keratin, that is only seen in thick skin
Describe the stratum corneum
The surface layer, multiple layers of dead cells (flattened cells, no nuclei, no organelles, embedded in keratin), is waterproof and undergoes cell shedding, and is very thick in thick skin
What are the four cell types in the epidermis
Keratinocytes
Langerhans cells
Merkel cells
Melanocytes
What is the function of keratinocytes?
they are predominant cell type described as the building block, that provide protection and an environmental barrier, as well as produce keratin
What are langerhans cells?
they are cells of the immune system
they are antigen presenting cell (consisting of dendritic cell, long cytoplasmic processes)
they are deprived from bone marrow
they reside in the stratum spinosum
Mode of action of langerhans cells?
They ingest foreign invading organisms and migrate to lymph nodes, where they warn the immune system of the invader
What do melanocytes do
produce melanin, which is a natural pigment that protects DNA from photo damage (UV light)
Where do melanocytes reside?
in the stratum basale
What is melanin secreted by?
melanocytes
What is melanin ingested by, and what is that process called?
They are ingested by keratinocytes in a process called endocytosis
Where is melanin moved to, and for what purpose?
They are moved to the apex to protect the nucleus
What does sun exposure initiate?
melanogenesis (tan)
