Biology of skin L2 Flashcards
what does skin do (4) (overview)
physical barrier
physiological functions
appendages
site of pathology
3 layers of skin
epidermis
dermis
subcutis
what is the epithelial cells of the epidermis called
keratinocytes
What is the dermis
dense irregular connective tissue supported by fibroblasts
what does the dermis contain
glands
sensory nerves
some immune cells
what is the subcutis
loose connective tissue with adipose cells
2 types of skin
thick and thin skin
what classifies what is thin and thick skin
extent of the thickening of the layer of the epidermis
what is thick skin associated with
mechanical stress and pressure
where is thick skin found
soles of the feet and palms
what is the bottom layer of the epidermis like
protrudes deep (undulating )
which type of skin is more common
thin skin
which skin has a more defined stratum corneum
thick skin
does thick skin contain hair or sebaceous glands
no
what extra layer may thick skin have
stratum lucidum
where is the stratum lucidum
between the stratum granulosum and stratum corneum
what type of skin lines most of the body
thin skin
what is less prominent in thin skin
stratum corneum
where is the thinnest skin
eyelids
what layer of the epidermis is not in thin skin
stratum lucidum
layers of the epidermis (4) top to bottom
cornified
granular
spinous
basal
how many layers of cells in the basal layer
1
what can the cells in the basal layer of the epidermis be described as
stem cells
what are stem cells capable of
division by mitosis
How many cell layers in the stratum spinosum
multiple cells thick
in the stratum spinosum what links adjacent cells
desmosomes
what are desmosomes
cell-cell junction link them mechanically to adjacent cells
what property do differentiated cells in the stratum spinosum lose
they can no longer divide
what is formed within the cells of the spinosum
prominent intracellular keratin filaments
what is directly above the spinosum
granular layer
what happens to cells in the granular layer
further differentiation through the production of keratohyalin granules and lamellar bodies
top layer of the epidermis=
cornified layer
what happens in the cornified layer
cells undergo apoptosis, losing their nuclei and organelles to form a tough surface layer
most abundant cells of the epidermis
keratinocytes
4 cells of the epidermis
keratinocytes
Melanocytes
immune cells
Merkel cells
what do keratinocytes produce
keratin
how do cells in the basal layer attach to the basale lamina
hemi desmosomes
what are melanocytes purpose
skin pigmentation and protection of UV damage
shape of melanocytes
dendritic
where do melanocytes reside
in lower layers of the epidermis
mode of action of melanocytes=
they synthesise melanin pigment which is packaged into organelles which are transferred into keratinocytes
what are the organelles melanin is packaged into called
melanosomes
what do melanocytes arise from in early development
neural crest cells
can melanocytes divide
yes
immune cells of the epidermis=
langerhans cells
what type of immune cell are langerhans
APC (antigen presenting cells)
shape of langerhans cells=
dendritic
where do langerhans arise from
bone marrow and migrate via blood
other type of immune cell present in the epidermis
lymphocytes
what are merkel cells
they are in association with nerve fibres responsible for fine touch
where are merkel cells found
basal layer
what forms the hydrophobic layer of the epidermis (3)
lipids
insoluble proteins
(and strong filaments linked by cell-cell junctions)
scaling=
imbalance between cell renewal and cell loss
blisters=
breakage of cell-cell junction
2 layers of the dermis
papillary
reticular
most superficial layer of dermis=
papillary
which layer of the dermis gives skin flexibility
papillary dermis
what is the papillary dermis made out of
loose connective tissue made of collagen and elastin fibres
what is also contained within the papillary dermis (3)
extensive capillary network
, lymphatic networks
and nerve endings
what are the upward projections in the papillary dermis called
pili
what is the purpose of pili (2)
- provide a surface area–>good blood supply to the avascular epidermis
- Attachment to epidermis
what layer makes up the majority of skin overall
reticular dermis
what is the reticular dermis made up of
dense irregular connective tissue
what is the dense irregular connective tissue made up of
thick bundles of collagen fibres
what cells does the reticular dermis contain
fibroblasts
immune cells
what is the reticular dermis a site of
skin appendages (e.g hair follicles and glands)
3 cells of the dermis
adipocytes
immune cells
fibroblasts
what is below the dermis
subcutis
what is the subcutis made out of
adipose tissue
what is the purpose of adipose tissue in the subcutis (3)
insulator
protector
energy store
3 skin appendages
sebaceous glands
eccrine sweat glands
apocrine glands
what is a nail plate
hard kertanised plate at distal end of each digit
what is the nail plate analogous with
the cornified layer
what is the nail plate renewed by
cells within the nail root which proliferate to form the nail matrix
where is a hair follicle formed
basal layer of epidermis
what is at the end of every hair follicle
bulbous expansion containing hair papilla
3 layers of hair
cuticle
cortex
medulla
what do sebaceous glands secrete
sebum that coats hair to keep it soft, supple and waterproof
what is the structure of sebaceous glands
branched acinar structure
type of secretion of acinar glands=
holocrine secretion
eccrine sweat glands
secrete sweat directly onto skin surface
type of eccrine secretion
merocrine secretion
what type of gland are eccrine glands
coiled tubular
where are eccrine glands found
deep reticular dermis
where are eccrine glands on the body
all tissues especially palms, soles, forehead and axillae
where are apocrine glands (3)
axillae,
mammary
groin
how do secretions occur in apocrine glands
apocrine manner with secretions discharged into upper part of a hair follicle
where are apocrine glands found in the skin
deep reticular dermis or subcutis
what are hairs and nails formed from
hard keratin
which layer of the skin does vasodilation or vasoconstriction effect
papillary dermis
what is vitamin D synthesis carried out by
keratinocytes in presence of UV light
langerhans and lymphocytes are found in the
epidermis
macrophages, mast cells and lymphocytes are found in the
dermis
4 stages of wound healing
haemostasis
inflammation
fibroplasia
remodelling
whats haemostasis
formation of fibrin clot stopping blood loss and filling wound
inflammation=
removal of bacteria and damaged tissue
fibroplasia=
fibroblasts laying down new collagen and angiogenesis
angiogenesis=
bridges gap
remodelling=
initial new tissue replaced through turnover to create stronger structure
liquid filled lesions= (4)
blister
vesicle
bulla
pustule
solid lesions= (4)
papule
nodule
wheal
plaque
lesions of colour= (4)
macule
patch
naevis
erythema
