skin Flashcards
Skin layers?
Epidermis ( stratified squamous epithelium) from surface ectoderm
Dermis - connective tissue framework from mesoderm
Hypodermis/ subcutaneous layer - loose connective tissue w adipocytes
Epidermis
- epithelial cells: ?
- non-epithelial cells: ?
epithelial cells: keratinocytes
non-epithelial cells:
melanocytes - protect against sunlight
langerhans cells - recognise external antigens
merkel cells - provide touch receptors
Layers in epidermis (SEE PIC 1 in notes)
- Stratum corneum
- Stratum lucidum
- Stratum granulosum
- Stratum spinosum
- Stratum basale
Basement membrane
Stratum basale/ germinativum
- function
- appearance
- what cells are present
- made up of cells that divide to provide new cells for constant regeneration of the other layers of the epidermis
- single layer of cuboidal or low columnar cells
- melanocytes and merkel cells present
-stimulated to produce more melanin by exposure to UV light
Stratum spinosum (see pic 2 in notes)
- composed of what cells and components
- composed of polyhedral cells (keratinocytes) filled with bundles of tonofilaments called tonofibrils
- tonofibrils (red arrow) converge into desmosomes (yellow arrows) that form strong contacts between adjacent keratinocytes
- langerhans’ cells and some melanocytes present
Stratum granulosum
1.
2.
- keratinocytes contain dense basophilic granules
- contain proteins which combine w tonofibrils to produce keratin - contain lamellar bodies containing various lipids → undergo exocytosis to produce a lipid-rich layer around the cells
Stratum lucidum
1.
2.
3.
4.
- cells lose their nuclei and cytoplasmic organelles
- contain keratin filaments
- present only in thick skin
- homogeneous layer
Stratum corneum (…layer)
1.
2.
[SEE PIC 3 in notes]
Stratum corneum (keratin)
1. composed of sheets (multiple layers) of dead cells filled w keratin [keratinocytes] which are shed off (exfoliated) regularly
2. water resistant
Disorder of melanocytes
1. Vitiligo-…
2. Moles/ nave -…
Vitiligo: depigmentation of the skin occurs –> autoimmune destruction of melanocytes
‘Moles’ or naevi are benign accumulations of melanocytes in the dermis, epidermis or both
How are blisters formed
disruption of the basement membrane will detach epidermis from dermis
Dermis - 2 layers
1.
2.
papillary dermis
reticular dermis
papillary dermis
top 20% of dermis
contains finer collagen compared to reticular dermis
anchors epidermis to dermis
contains capillaries that feed epidermis
contains Meissner’s corpuscles (touch) and free nerve endings for sensations of heat, cold, pain, tickle and itch
reticular dermis (after that see pic4)
Dermis rests on subcutaneous tissue (hypodermis or
superficial fascia)
dense irregular connective tissue
interlacing collagen and elastic fibers
contain sweat glands, fat and hair follicles
Arrector pili muscles (smooth muscles) in thin skin are attached to the hair follicles and connective tissue of the dermis in the papillary layer
collagen fibres in reticular layer lie parallel to each other
nerve receptors: ruffini corpuscles - pressure touch; Pacinian corpuscles - vibratory pressure and touch
appendages associated w skin (see pic 5)
hair follicle
sweat gland
sebaceous gland
nail
Exocrine VS endocrine glands
see pic 6
Merocrine (eccrine) sweat glands VS apocrine
see pic 7
How does sebaceous gland work
alveoli
Inner cells are filled with lipid which is discharged by
disintegration of the cells (holocrine secretion).
Proliferation of outer cells replaces the degenerated inner cells
Sebaceous gland
(i) (ii)
(a) typical sebaceous glands - secrete into hair follicles
(b) sebaceous follicles - secrete onto skin surface
external genitalia (some parts) → open directly onto skin surface e.g. eyelids - modified sebaceous glands (tarsal glands)
Hair follicle, sebaceous glands and arrector pili muscle form the pilosebaceous unit
See pic 8 and 9
Burns
- Superficial
- Partial thickness
- Full thickness
- Fourth degree
Superficial – epidermal injury with no blisters
Partial thickness – epidermis and dermis are partially involved
Superficial–Blisters
Deep - hair follicles and glands are damaged
Full thickness – All layers of the skin are involved . Subcutaneous tissue may be affected
Fourth degree –They extend beyond the skin into the soft tissue and are considered as most severe type of burns
