Skin and Tissue Flashcards
what is keratinisation
organic process by keratin is deposited in cells and these become horny as in dead skin, nails and hair
what are the 2 layers of the dermis
papillary layer
reticular layer
what is the papillary layer
1st layer of dermis
loose connective tissue
cellular
protective against pathogens
what is the reticular layer
dense irregular connective tissue
fibrous
collagen bundles in 3 planes
elastic fibres
what tissues does skin consist of
epithelium
connective
muscle
nerve
what are epidermal cells termed
keratinocytes
whats the function of the dermis
maintains epidermis w blood flow
body cooling
uv protection
immune surveillance
What’s the hypodermis?
adipose (fatty) layer beneath skin
subcutaneous tissue, anchors skin to underlying structures
what is the epithelial
The tissue covering and protects the body surface and internal organs
stratified squamous keratinising epithelium
what are the 4 types of epidermal cells
keratinocytes, melanocytes, langerhans cells, merkel cells
What are keratinocytes?
epidermal cells, contain keratin, resistant to abrasion, extrude lipids
constantly dividing, self regeneration protect from trauma
what are melanocytes
epidermal cells, pigment formation
What are Langerhans cells?
Specialised dendritic cells found in the skin
immune surveillance
What are Merkel cells?
touch receptors
what are the epidermal layers
(superficial) stratum corneum, stratum lucidum, stratum granulosum, stratum spinosum, stratum basale
Where does skin colour come from and what layer of the epidermis is it in?
melanin - protects agaisnt UV
melanocytes
in stratum. germinativum
explain hair
it is NOT thermoregulatory in humans
practical use in skin repair
from epithelial layer
explain the origin of hair follicles
from epidermis in utero downgrowth of epithelial cells invasion of knot of blood vessels growth of hair continuity with layers of epidermis
describe hair follicle structure
hair + sheath
- arrector pilli muscles: attached to follicle root and base epidermis
follicle at angle
hair straightens when muscle contracts
- sebaceous glands: between follicle and arrector pilli muscle
secretes sebum
in DERMIS
explain nails
strong plate of hard keratin , grows out of nail bed
nail plate analogous to stratum corneum
eponychium
hyponchium
what is the eponychium and its function
cuticle, thickened layer of skin around nail
protect skin from exposure to bacteria
what is the hyponchium
thickened portion of epithelium underlying free edge of the nail plate on the nail
what are the type of skin glands
sebaceous - hair + sebum
2 types of sweat glands
- eccrine (everywhere)
- apocrine (pubic areas, arm pit)
all in dermis
explain eccrine sweat glands
simple tubular glands in dermis coiled secretory portion coiled and straight ducts in dermis spiral channels in epidermis
how does thermoregulation happen in the skin
through sweat glands +
blood vessel dilation (absorption and radiation)
what are the sensory nerve ending in the skin
meissner’s corpuscles - light touch, fingertips
paccinian corpuscles - vibration and pressure
pain receptors
thermoreceptors
what are the 4 types of tissue
epithelium
connective
muscle
nerve
whats the function of the epidermis
covers surfaces
cells connected
separates compartments
forms glands
what are examples of connective tissue
blood, bone, adipose tissue
describe muscle tissue and 3 types
contractile
long thin cells
skeletal, cardiac and smooth
describe skeletal muscle
striated, highly ordered
describe cardiac muscle
striated, branched
describe smooth muscle
non-striated
randomly ordered.
one nucleus per cell
function of nervous tissue?
communication
receives, generates and transmits electrical signals.
describe neurone structure
cell body (soma)
dendrites
axon
terminals
how does epithelial tissue connect cells
no contact inhibition
cell - cell junctions
cell - ECM junctions
what are desmosomes
adhering junctions function - firm anchorage
what are tight junctions
occluding junctions
- seals intercellular spaces
what are gap junctions
communicating junctions
cell - cell communication
what is the basement membrane and what does it consist of
layer of proteins, separates epithelium from lamina propia
made up of basal lamina and reticular lamina
what are some cell-ecm junctions
hemidesmosomes
what is cilia
epithelium secondary roles - movement
what is microvilli
epithelium secondary roles – absorption
whats the difference between simple and stratified epithelium
simple - one cell thick
stratified - more than 1 layer
what are the types of epithelium structure
squamous, cuboidal and columnar
what are glands
collections of secretory epithelial cells
single or multicellular
exocrine or endocrine
What are endocrine glands
secrete into blood
what are exocrine glands
secrete into tubes
what types of exocrine glands to you get
simple - tubular and acinar
compound - tubuloacinar
mucous and serous glands
what r mucous glands
secretion rich in proteoglycans
secretion + water = mucus
what are serous glands
watery, enzymes
protein rich secretion
what are the methods of exocrine secretion
- diffuse through cells
- pinched off portion of cell
- disintegrating cell and its contents
what are myoepithelial cells
they expel the secretions of exocrine glands
what is the pituitary gland
secretes growth hormone
can over produce and under produce
where is adipose tissue found
in bone marrow + mesenteric fat around intestines
what fibres are there in the ECM in connective tissue
collagen and elastin
what are the types of collagen
Type 1 - tendons
type 3 - reticulin
type 4 - in basal lamina
explain elastic fibres
protein elastin stretch 1.5 times resting length microfibrils and amorphous component found in sheets yellow colour (aorta)
what are the components of the ECM in connective tissue
fibres
ground substance - like jelly
tissue fluid
whats in the ground substance
semi-solid gel
proteoglycans
hyaluronic acid
glycoproteins
what types of connective tissue are there
loose
dense regular
dense irregular
describe loose connective tissue
permanent (fixed) cells fibroblasts macrophages adipcytes mast cells
transient cells - wbc
what are the layers of the skin
epidermis and dermis
whats the function of the epidermis
prevents water loss by evaporation
