Cephalochordate Integument Epidermis = 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 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 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 CaPO 4, 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 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.
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.
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
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.
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 = / Dog = / Mule deer = /