The Integument 1 Flashcards
what does the integument include
- skin
- hair and variety of skin associated glands
- claws, hoofs, and horns
what are the functions of the integument
- protective- wear and tear
- barrier- microbial penetration
- thermoregulation
- sensory perception
- storage organ
- synthesis of vit D
- glandular (sebum and sweat secretions)
- photo-protection/sensitization
- immuno-surveillance
- capture of prey
what is the structure of skin
contains
- epidermis
- dermis
- hypodermis
- often contains hair follicles, and skin associated glands (adnexa)
name the layers
epidermis
basement membrane
dermis or corium (dense irregular connective tissue layer)
subcutis or hypodermis (adipose tissue and loose CT)
what is the function of the epidermis
outer layer, protection
what does the epidermis contain
keratinocytes, melanocytes, Langerhans cells, merkel cells
what is the function of the basement membrane
below epidermis and connects epidermis to dermis
what is the function of the dermis
support + nourishment to the epidermis and skin appendages
what does the dermis contain
blood vessels
sensory nerves
motor nerves
immune cells
what are the skin appendages
hair follicles, oil + sweat glands, claws
what is the function of sebaceous glands and where are they found in dogs
secrete oily substance –> sebum
near paws, back of neck, rump, chin, tail area
what is the subcutis or hypodermis layer
innermost layer
subcutaneous fat + muscles
what is the embryological development of the skin
primitive epidermis is of ectodermal origin
dermis is of mesodermal origin
basal cells undergo proliferation, migration and differentiation resulting in cell death
stratified keratinized squamous epithelium –> forms a physical and permeability barrier
melanocytes from neural crest origin migrate to the dermal-epidermal border –> responsible for pigmentation
what are the strata layers in the epidermis
- stratum corneum (dead keratinocytes)
- stratum lucidum
- stratum granulosum (lamellar granules)
- stratum spinosum (keratinocyte, langerhans cell, melanocytes)
- stratum basale (merkel cell)
- dermis
what is the sequence of events from the dermis to the stratum corneum
- cells continuously divide at the basal layer
- cells become keratinized as they move away from the basal layer
- cells are dead and are continuously lost from the skin surface
what occurs at the stratum basale or basal layer
basal cells –> single layer of mitotically active diving stem cells move outward
tonofilaments appear in the cytoplasm (precursor of keratin)
what occurs at the stratum spinosum layer
several layers thick
layers of polyhedral cells with spiny projections
cells become progressively flattened
lamellar bodies appear –> ogranells containing lipid
what occurs at the stratum granulosum layer
cells become flattened
organelles start to break down
keratohyalin granules appear –> contain pro-filaggrin a precurso of filaggrin (causes tonofilaments to aggregate and form tonofibrils)
what occurs at the stratum lucidum layer
flattened cells lack nucleus or organelles –> cytoplasm now contains keratin aggregates
what occurs at the stratum corneum layer
layers of highly keratinzed dead cells
keratin filaments polymerize to form strong disulphide bonds (filaggrin is involved)
thickened cell envelope forms –> composed of involucrin, loricrin, and other proteins
lipids, discharged by lamellar granules fill intercellular spaces and contribute to skin barrier
special cell junctions rivet the squames together –> absent in outermost layer –> shedding
how is the skin barrier regenerated
by continuous process of keratinization –> proliferation, migration, differentation, cell death and loss
what does the control of desquamation at the surface depend on
balance between stratum corneum protease inhibitor and proteases (enzymatic degeneration of desomsomes –> junctional complexes which anchor the cells to the surface
skin pH
what are the histological features of thick hairless skin
- epidermis thick
- stratum corneum is particularly thickened (12-20 layers) –> subject to constant abrasive forces
- dermal-epidermal border interdigitates –> anchors epidermis to dermis
- no hair follicles
- sweat glands (eccrine) are often present in the dermis
what type of skin is this
thick hairless skin
what are the histological features of thin hairy skin
- epidermis is very thin –> different strata can still be recognized at thigh magnification
- hair follicles + sebaceous and sweat glands all in the dermis
which type of skin is this
thin hair skin
what cells does the dermis consist of
fibroblasts, mast cells, plasma cells, macrophages, adipocytes, melanocytes, lymphocytes, neutrophils
what fibres does the dermis contain
different types and proportions –> collagen, reticular and elastic fibres
what is the ground substance in the dermis
dense fluid (proteoglycans and glycoprotein)
what is the function of the fibroblasts in the dermis
produce/maintain the extracellular matrix
what is the blood supply to the skin
located in the dermis
nourished by diffusion
arterio-venous anastomosis –> important for thermoregulation
why is the skin sensitive
melssner’s corpuscle (touch)
free sensory nerve endings (pain, heat, cold)
pacinian corpuscle (pressure)
