Integument Skin = composite organ Epidermis = superficial; epithelial tissue; ECTODERMAL Dermis = deep; connective tissue; mostly MESODERMAL Neural Crest Cells = migrate into both epidermis and dermis; ECTODERMAL
Mar 31, 2015
IntegumentSkin = composite organ
Epidermis = superficial; epithelial tissue; ECTODERMAL
Dermis = deep; connective tissue; mostly MESODERMAL
Neural Crest Cells = migrate into both epidermis and dermis; ECTODERMAL
Epidermis = generalized ectoderm + neural crest (pigment cells)
Dermis = dermatomal mesoderm + scattered neural crest cells
Vertebrate Integument Devel.
Vertebrate Embryo (section)
gut
coelom
dermatome
vertebra
myotome
epidermalectoderm
developingskin
dermis
epidermis
neural crest
Cephalochordate IntegumentEpidermis = 1 cell layer (simple epithelium)
Dermis = compact alternating layers of collagen with fibroblasts
NO neural crest
EPIDERMIS
DERMIS
Mucus
Basal lamina
Vertebrate/Craniate Skin Stratified epidermis (= an epithelium)
Stratum basale (Basal Layer) = deep layer, contacts the basal lamina, mitotically activeKeratin = proteins in superficial epidermis (keratinocytes); “harden” = cornifiedStratum corneum = heavily keratinized surface layer of epidermis (only in tetrapods)
Dermis usually more complex (= conn. tissue)
Stratum laxum = more superficial & irregular (only in gnathostomes)
Stratum compactum = deep & more ordered
Vert./Craniate Epidermis Devel.Epidermis begins as a simple epithelium
Then forms two-layers.
Periderm – superficial
Basal layer (stratum basale) – deep; contacts basement memb.; forms adult epidermis.
Dermis Devel. First dermatome cells make layered collagen
and form fibroblasts under the epidermal basement membrane = stratum compactum (contiguous with the reticular lamina)
The in gnathostomes, the stratum compactum separates from the reticular lamina of the basement membrane (delaminates).
The stratum laxum forms between the stratum compactum & the reticular lamina of the epidermis after delamination.
Human Integument Stratified keratinous epidermis, strata laxum
and compactum in dermis
Hair = keratinous epidermal outgrowth (with dermal pulp cavity)
Sweat glands = coiled, produce watery sweat for cooling or traction.
Sebaceous glands = associated with hair follicles, produce sebum.
Mammary glands = produce milk (similar to sweat & sebaceous glands)
Human Integument
Epidermis
Dermis
Stratumcorneum
Hair
Sebaceousgland
Sweatgland
Human Hair & Gland Devel.
Human Mammary Ridge and Mammary Glands
Mammary glands form regionally along mammary ridge in all therian mammals (location and number vary).
Human Mammary Development Mammary Glands,
single pair with nipples, fat and glandular tissue.
Supernumary (ectopic) nipples form along developmental “milk” line.
Human Integument
Hair on all surfaces EXCEPT:
palms of hands, soles of feet, lips, nipples, penis, and clitoris
Sebaceous glands on all surfaces EXCEPT:
palms of hands and soles of feet
Sebaceous glands associated with hair follicle (except on lips, nipples, penis, and clitoris).
Human Skin Problems/DiseasePimples form when a hair follicle is
blocked and sebum builds up.
Skin Cancer
most common – basal cell carcinoma
most dangerous - melanoma
Integumentary Bones/Scales
Dermal bones = bone formed in the deep dermis around collagen by osteoblasts. e.g., some skull bones
Dermal scale = bone formed in more superficial dermis around collagen by osteoblasts. (may have epidermal contributions) e.g., some “fish” scales
Epidermal scale = proteinaceous, formed by dead keratinocytes in the epidermis. e.g., reptile scales
Dermal Bone Growth
Dermal (Bony) ScalesEpidermis can contribute enamel.
Enamel = acellular CaPO4, hardest vertebrate produced substance.
Dermis can contribute 3 kinds of bone.Dentin(e) = acellular, hard bone; under the
epidermis
Dermal Vascular Bone = cellular & vascularized/“spongy”; in stratum laxum
Dermal Lamellar Bone = cellular or acellular, formed in flat layers; in stratum laxum or stratum compactum
Dermal Scales
Epidermal
Dermal
Acellular
Cellular
Acellular or Cellular
Enamel
Dentine
Lamellar Bone
Vascular Bone
Integumentary GlandsEpidermal; secrete to skin surface
Unicellular Glands - Common in non-tetrapod epidermis; rare in tetrapods; usually produce mucus.
Multicellular Glands - Rare in non-tetrapod epidermis; common in tetrapods(Exception: Multicellular slime glands in hagfishes)
Mucus “Cuticle” – Mucus layer covering some amphibians and all non-tetrapods; protects from abrasion and pathogens
Hagfish & LampreysKeratinous (epidermal) “teeth”
No dermal or epidermal scales.
Petromyzontid Integument
Epidermis
Dermis(stratumcompactum)
Basal layer
Ammocoete larva
Basal lamina
Placoid ScalesSynapomorphy of chondrichthyans
Enamel (superficially), Dentin (deep)
Scale “erupts” from epidermis.
Central dermal pulp cavity.Enamel
Dentin
Pulpcavity
Ganoid ScalesFound in reedfishes, gars, and fossil
sturgeon and bowfin
Enamel (superficially), Lamellar bone (deep), lack a pulp cavity
Scale “erupts” from epidermis.
Teleost ScalesLamellar bone ONLY
Scale covered by epidermis.
Cycloid or Ctenoid (with projections)
Craniata
hagfis
hes
lam
preys
Chondrichth
ys
Actin
optery
gii
coel
acan
ths
lungfis
hes
amphib
ians
Mam
mal
ia
Reptil
ia
stratified epidermis
Subphylum Vertebrata
hagfis
hes
lam
preys
Chondrichth
ys
Actin
optery
gii
coel
acan
ths
lungfis
hes
amphib
ians
Mam
mal
ia
Reptil
ia
placoidscales
ganoidscales
dermal bone; dermal stratum laxum
dermalscaleslost
sturg
eons
&
paddle
fishes
gars
Amia
(the
bowfin)
TELEOSTS
reed
fishes
Class Actinopterygii
cycloid orctenoidscales(enamel lost)
ganoid scales
Tetrapod IntegumentStratum corneum =
superficial layer of dead keratinocytes (outer epidermis)
prevents water loss; protects- thin, underlies mucous layer in lissamphibians.
- thick, “replaces” mucous layer in amniotes.
Lissamphibian Integument
Epidermis
Dermis
Multicellular mucous glands
Multicellular poison glands
Mucous gland Poison gland
Stratumcorneum(thin)
Amniote IntegumentThick stratum corneum (no mucus) -
Primary barrier to water loss and infection.
Epidermal derivatives made of keratin: epidermal scales, hair, feathers
Reptile IntegumentEpidermal scales = thickened stratum
corneum separated by thinner areas of stratum corneum
can be “tiled” or overlapping.
Avian Reptile IntegumentEpidermal scales on legs & feet
Feathers = modified epidermal scales (with dermal pulp cavity)
Few multicellular glands
Mammalian IntegumentEpidermal scales LOST
Hair = keratinous epidermal outgrowth (with dermal pulp cavity)
Sweat glands = coiled, produce watery sweat for cooling or traction. (Scent glands) = modified sweat glands
Sebaceous glands = associated with hair follicles, produce sebum.
These form by sinking of regions of epidermis into the dermis.
Mammalian Integument
Epidermis
Dermis
Stratumcorneum
Hair
Sebaceousgland
Sweatgland
Mammalian Hair
Mammalian IntegumentMammary glands = produce milk for
nourishment of young...
derived from sweat and/or sebaceous glands.
NippleTeat
cisternMonotremes lack nipples.
Vertebrate MiscellaneousKeratinous claws, nails, or hooves
(Tetrapoda)
Keratinous beaks (Aves & Testudinea)
Shell plates (Testudinea & armadillos) = dermal bone & keratinous sheets
Horns (various amniotes) = dermal bone & keratinous sheath
Antlers (cervid mammals) = dermal bone (shed yearly)
Reptilian Keratinous Beaks
Amniote “Shells” of Dermal Bone
Horns and Antlers
Subphylum Vertebrata
hagfis
hes
lam
preys
Chondrichth
ys
Actin
optery
gii
coel
acan
ths
lungfis
hes
amphib
ians
Mam
mal
ia
Reptil
ia
stratumcorneum
thickstratumcorneum,mucus layer lost
* epidermal scales of beta keratin
*
Amniota
montre
mes
mar
supia
ls
euth
eria
ns
turtl
es
lizar
ds & s
nakes
croco
dilian
s
birds
feathers,beak
beak,shellplates
epidermalscales of beta keratin
hair;sweat, sebaceous,& mammary glands
nipples
Teeth
Teeth formed by the epidermis & dermis.
Thought to be derivatives of “placoid” scales around mouth.
Epidermis contributes enamel.
Neural crest cells in dermis contribute dentin and constitutes some of the pulp cavity.
Tooth Development
Enamel organ = epidermis that sinks into dermis, ameloblasts make enamel.
Dermal papilla = dermis surrounded by enamel organ, odontoblasts make dentine.
- primarily of neural crest cells.
Chondrichthyan Teeth
Revolver Dentition = teeth develop further back in the mouth and as they mature move to the crest of the bone.
Eventually fall out.
teeth inuse
developingteeth
Tooth TermsHomodont = all teeth
similar.Heterodont = teeth that
differ.Polyphyodont = teeth
replaced continually throughout life.
Diphyodont = teeth replaced once in life (2 sets of teeth). - Mammals
Subphylum Vertebrata
hagfis
hes
lam
preys
Chondrichth
ys
Actin
optery
gii
coel
acan
ths
lungfis
hes
amphib
ians
Mam
mal
ia
Reptil
ia
heterodont,diphyodont
teeth
revolverdentition
Mammalian TeethAnterior to Posterior
Incisors = flattened teeth, 1 cusp.
Canines = conical teeth, 1 cusp.
Premolars = multicusped teeth, present in both first and second sets of teeth.
Molars = multicusped teeth, present only in second set of teeth.
Mammalian TeethDiastema = space between teeth.
Dental Formula = Count of tooth types in one half of a mammal jaws.
Incisors-canines-premolars-molars
upper first, lower jaw second.
Human = 2-1-2-3 / 2-1-2-3
Dog = 3-1-4-2 / 3-1-4-3
Mule deer = 0-0-3-3 / 3-1-3-3
Human Teeth
2 - 1 - 2 - 3