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

Vertebrate Integument Devel. Epidermis = generalized ectoderm + neural crest (pigment cells) Dermis = dermatomal mesoderm + scattered neural crest cells

Vertebrate Embryo (section) dermatome vertebra myotome developing skin gut epidermal ectoderm coelom dermis epidermis neural crest

Cephalochordate Integument Epidermis = 1 cell layer (simple epithelium) Dermis = compact alternating layers of collagen with fibroblasts NO neural crest Mucus EPIDERMIS Basal lamina DERMIS

Vertebrate/Craniate Skin Stratified epidermis (= an epithelium) Stratum basale (Basal Layer) = deep layer, contacts the basal lamina, mitotically active Keratin = proteins in superficial epidermis (keratinocytes); “harden” = cornified Stratum 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 Stratum corneum Epidermis Hair Sebaceous gland Dermis Sweat

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/Disease Pimples 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) Scales Epidermis 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 Enamel Dentine Vascular Bone Lamellar Bone Epidermal Acellular Cellular Acellular or Cellular

Integumentary Glands Epidermal; 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 & Lampreys Keratinous (epidermal) “teeth” No dermal or epidermal scales.

Petromyzontid Integument Ammocoete larva Epidermis Basal layer Basal lamina Dermis (stratum compactum)

Placoid Scales Synapomorphy of chondrichthyans Enamel (superficially), Dentin (deep) Scale “erupts” from epidermis. Central dermal pulp cavity. Enamel Dentin Pulp cavity

Ganoid Scales Found in reedfishes, gars, and fossil sturgeon and bowfin Enamel (superficially), Lamellar bone (deep), lack a pulp cavity Scale “erupts” from epidermis.

Teleost Scales Lamellar bone ONLY Scale covered by epidermis. Cycloid or Ctenoid (with projections)

Craniata Chondrichthys Actinopterygii coelacanths amphibians Mammalia hagfishes lampreys lungfishes Reptilia stratified epidermis

Subphylum Vertebrata Chondrichthys Actinopterygii coelacanths amphibians hagfishes lungfishes lampreys Mammalia Reptilia ganoid scales dermal scales lost placoid scales dermal bone; dermal stratum laxum

Class Actinopterygii sturgeons & paddlefishes Amia (the bowfin) reedfishes TELEOSTS gars cycloid or ctenoid scales (enamel lost) ganoid scales

Tetrapod Integument Stratum 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 Multicellular mucous glands Multicellular poison glands Stratum corneum (thin) Epidermis Dermis Mucous gland Poison gland

Amniote Integument Thick stratum corneum (no mucus) - Primary barrier to water loss and infection. Epidermal derivatives made of keratin: epidermal scales, hair, feathers

Reptile Integument Epidermal scales = thickened stratum corneum separated by thinner areas of stratum corneum can be “tiled” or overlapping.

Avian Reptile Integument Epidermal scales on legs & feet Feathers = modified epidermal scales (with dermal pulp cavity) Few multicellular glands

Mammalian Integument Epidermal 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 Stratum corneum Epidermis Hair Sebaceous gland Sweat

Mammalian Hair

Mammalian Integument Mammary glands = produce milk for nourishment of young... derived from sweat and/or sebaceous glands. Nipple Teat cistern Monotremes lack nipples.

Vertebrate Miscellaneous Keratinous 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 Chondrichthys Actinopterygii coelacanths amphibians hagfishes lungfishes lampreys Mammalia Reptilia * thick stratum corneum, mucus layer lost stratum corneum * epidermal scales of beta keratin

Amniota lizards & snakes crocodilians montremes marsupials eutherians turtles lizards & snakes crocodilians birds beak, shell plates nipples hair; sweat, sebaceous, & mammary glands feathers, beak epidermal scales of beta keratin

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 in use developing teeth

Tooth Terms Homodont = 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 Chondrichthys Actinopterygii coelacanths amphibians hagfishes lungfishes lampreys Mammalia Reptilia revolver dentition heterodont, diphyodont teeth

Mammalian Teeth Anterior 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.

Incisors-canines-premolars-molars Mammalian Teeth Diastema = 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