2.2 skin histology Flashcards
Skin functions
barrier, immunity. sensory functions, exocrine functions, homeostasis, excretion
Skin layers
Epidermis, dermis, hypodermis
Epidermis: characteristics
superficial layer resist abrasion ectoderm avascular nourishment from diffusion of capillaries in papillary layer of dermis
Dermis: characteristics
contains hair, glands, ducts and bvs
mesoderm
Hypodermis: characteristics
subcutaneous tissue
loose CT
adipose tissue
Epidermis layers `
Stratum corneum stratum lucidium stratum granulosum stratum spinosum stratum basale
Stratum corneum
superficial layer
keratinised cells - flat + non-nucleated
stratum lucidium
thick skin, flat cells
stratum granulosum
keratohyalin granules
terminal differentiation - nucleus + other organelles degenerate -> cell death
flat + polygonal cells
stratum spinosum
thickest layer
keratin fibre synthesis
cuboidal cells
stratum basale
high mitotic activity
on basement membrane
cuboidal/low columnar
Epidermal cells
keratinocytes
melanocytes
merkel cells
langerhan cells
Desquamation
cells in deeper layer undergo mitosis
cells move up toward the surface
older cells slough off
epidermis renewed ~15 days
keratinisation
cells move upward through layer fill with keratin and die
layer resists abrasion + forms waterproof layer
thick vs thin skin
thick - hairless, thick stratum corneum, stratum lucidium present, 5 layers
thin - hair, thin stratum corneum, no stratum lucidium , 4 layers
dermis: characteristics
structural strength
connective tissue with: fibres, fibroblasts, macrophages, adipocytes
contains: BVs, nerves, hair follicles, smooth muscles, glands
dermis: function
support endothelial cells of epidermis
connect epidermis to hypodermis
changes in thickness
dermis: layers
papillary
reticular
dermis: papillary layer
superficial
loose ct with elastic fibres, collagen fibres
dermal papillae
dermis: reticular layer
dense irregular ct
thick collagen bundles
coarse elastic fibres
hair follicles, nerves, adipose, oil glands
thick vs thin skin: dermal papillae
thick skin - well formed rete ridge system
thin skin - poorly formed rete ridge system
rete ridge system
interface between epidermis + dermis held together by interlocking epidermal ridges
prevents epidermal separation
free nerve endings
fine touch
heat and cold
pancinian corpuscle
crude touch
high freq vibrations
reticular dermis
meissner’s corpuscle
discriminative touch
low freq vibrations
in papillary dermis
hypodernis: consists of
loose CT adipose cells fibroblasts macrophages contains 50% of body's adipose tissue
hypodermis: function
energy source
insulation
padding
supplies the dermis
determination of skin colour
pigment
blood circulation through skin
thickness of stratum corneum
melanin
protect against UV
eumelanin: brown -> black pigments
pheuomelanin: yellow -> red pigments
melanocytes
produce melanin then passed into keratinocytes via dendritic processes that extend between keratinocyte
melanocytes in light vs dark skin
light skin: stratum basale
dark skin: stratum granulosum
accessory skin structures
hair
sebaceous glands
sweat glands
type of sweat glands
eccrine -
apocrine -
types of malignant melanoma
basal cell carcinoma
squamous cell carcinoma
malignant melanoma
basal cell carcinoma
basale layer 30% incidence rate slow growth arises from hair follicle treatment: surgical removal
squamous cell carcinoma
atypical cells of epidermis
disruption of basement membrane
tumour spread into lymph
malignant melanoma
metastatic and invasive
effects melanocytes -> abnormal with dark keratin granules that migrate through epidermis and dermis entering the lymph
stages of wound healing
- Blood clot formation
- Macrophages remove damaged CT fibres
- Re-epithelialisation
- Deposition and remodelling of CT and the CT matrix
Eccrine sweat glands: characteristics
- most common
- temp regulation
- coiled tubular glands - produce sweat
- excretes ammonia, urea, uric & lactic acid
Apocrine sweat glands: characteristics
- active at puberty
- coiled, compound tubular glands
- secretes odourless compounds that become odiferous when acted upon bacteria
- found in axillae, genitalia
sebaceous glands: characteristics
- pheromones
- holocrine secretion
- oily sebum secretion
- empties into hair follicles
epithelium: characteristics `
- presence of basement membrane
- high cell turnover
- defined apical surface
- involved in formation of exocrine and endocrine glands
