ANAT 261 Lecture Notes - Dense Irregular Connective Tissue, Keratin, Loose Connective Tissue

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Lab 1 – The Skin
The skin is divided into three distinct layers:
-epidermis – outermost layer; epithelial tissue
-dermis – middle layer; connective tissue
-hypodermis – innermost layer; adipose tissue
Epidermis
- the epidermis is stratified squamous epithelium (keratinized)
oKNOW THIS!
oevery word is required for describing an epithelium, so be careful to
include it all, even the ‘keratinized’
- no blood vessels in the epidermis
- cellular layers of the epidermis:
ostratum germinativum/basale: single layer of columnar cells
innermost layer of epidermal tissue, adjacent to the dermis
rests on the basement membrane (BM)
*Note: in the lab, you can’t see the BM structurally, but you know
that it is always present between the epidermis and dermis.
darkly coloured with clearly defined nuclei
actively dividing to provide the cells for the upper layers
ostratum spinosum: polygonal cells with central nuclei
cells interconnected by desmosomes which appears like little
spines
ostratum granulosum: squamous (flat) cells
contain keratohyaline granules
granules are basophilic (give cells dark blue/purple
appearance)
cells no longer dividing and are committed to death
ostratum corneum: dead squamous cells (no nuclei are present)
top layer
composed of keratin (acts to protect and waterproof skin)
Dermis
- composed of two layers:
opapillary layer
loose connective tissuemore cells, less collagen fibres
appears paler light pink
right under BM
oreticular layer
dense irregular connective tissue – more collagen fibres; more
disorganized arrangement
fibres are acidophilic/eosinophilic (cause this layer to appear
red/pink)
- the dermis contains blood vessels for the skin
Hypodermis
- lies below the dermis
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Lab 1 – The Skin
- made primarily of adipocytes (fat cells)
odo not stain well with hematoxylin or eosin, so appear white and empty
- involved in thermoregulation
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S. corneum
S. granulosum
S. spinosum
S. germinativum
Papillary layer