Outline-1, BIO 3220, Integumentary System


A. Function

1. Protection and Support

2. Sensory

3. Respiratory exchange

4. Thermoregulation

a. Dissipate heat

1. Blood vessels

2. Sweat

b. Conserve heat

5. Locomotion

6. Water balance

7. Protective coloring, behavior

8. Vitamin D synthesis

B. Structure


a. Ectodermal derivative

b. Nonvascular

c. Stratum germinativum –Actively mitotic layer

d. Superficial layer

1. Mucus cells –Amphibians & Lower classes

Mucus, poisons, photophores

2. Proteinaceous cells/Granular glands

a. Slime, poisons, enamels, photophores, pheromones

b. Keratin (Cornified, Horny) – Tetrapod feature

-Feather, claw, scales

-Stratum corneum

3. Glands are epidermal in origin


a. Dermatome, lateral and ventral somatic mesoderm, +/- neural crest cells

b. Collagen, mucopolysaccharide, elastic fibers, +/- smooth muscle (e.g. erectors = arrectors) ,+/- fat, blood and lymph vessels, follicles, gland bases

c. Bone potential –Ancient potential of forming bone

4. Hard Tissues

a. Enamel –Calcium Phosphate, Calcium Hydroxide present; Permanent external tissue made from ectoderm.

b. Dentin(e)– Similar to bone in makeup; formed from mesoderm; about 25% organic fibers; Odontoblasts retreat after formation.

c. Bone– Tends to be deeper; organic fibers, calcium crystals, usually has cells present

1. Lamellar =Compact bone; cellular and acellular types

2. Spongy

d. Phylogeny –Bone is primitive tissue

5. Chromatophores – Dermal origin –From neural crest cells

a. Melanophores – homeotherms –pigment injected into epidermis

b. Poikilotherms– pigment remains in dermis

c. Iridophores

d.  Xanthophores

e.  Erythrophores


1. Epidermis

a. Cyclostomes –Thin, unicellular mucus glands

b. Jawed

1. Mucous glands – Unicellular Help to clean & protect skin, decrease resistance when swimming

2. No keratin

3. Photophores –May invade dermis and serve as lures, warning, and recognition

2. Dermis

a. Cyclostomes– No scales

b. Armor shields –Ostracoderms, Placoderms

1. Lamellar Bone, Spongy Bone, Dentin(e), Enamel

2. Denticle

3. Protective; Reservoir

c. Cosmoid scales –Cosmine is modified thick dentin layer; found in extinct sarcopterygians

d. Ganoid scales –Ganoine is modified enamel layer; found in gars

e. Placoid scales –Found in Chondrichthyes; ancestor to teeth; denticle points decrease friction when swimming

f. Modern scales –Acellular, thin lamellar bone; found in teleosts and modern lobe fin fish

1. Cycloid

2. Ctenoid


1. Major differences

a. No scales

b. Multicellular glands –Abundant; primarily mucus glands

c. Stratum corneum –Prevents against abrasion & desiccation

2. Epidermis

a. Thin

b. Stratum corneum with keratin –Only about 5-8 layers thick

c. Mucous and granular glands sometimes secreting alkaloid material

3. Dermis –Firmly attached, may have chromatophores; caecilians may have bony scales


1. Major differences

a. THICK stratum corneum

b. Epidermal scales

c. Horny surface structures –Helps to protect against predators

d. Few glands

e. Some have bony dermal scales/plates

2. Epidermis

a. Stratum corneum with keratin

1. Scales –All have scales. They overlap & are shed.

2. Scutes –Keratin plates of epidermis; e.g. rattles on snake, turtle outer shell

b. No mucus glands

c. Some have granular/scent glands –But small & very few

3. Dermis

a. Thin

b. Osteoderm –e.g. Crocodile

c. Turtle shell – Carapace & Plastron

d. Gastralia –Splints of bone in ventral abdominal wall of crocodiles; dermal scale derivative


1. General differences

a. Thin skin –Only thick at foot & beak

b. Feathers

2. Evolution –Perhaps from epidermal scales OR a new structure

3. Epidermis

a. Thin

b. Horny scales –Not shed

c. Beak

d. Uropygial glands

e. Feathers

1. Contour feathers

a. Shaft

1. Calamus = quill

2. Rachis

b. Vane

1. Barb

2. Barbule

3. Hooklet

4. Preening

2. Down feathers

3. Molt – Feather Follicle –Ectoderm, but activated by mesoderm

4. Dermis– Thin arrector pullorum muscles present


1. Major differences

a. Hair

b. Glands –Quite a variety – sweat, oil, mammary

c. Stratified cornified epidermis –Highly keratinized. Thick dermis

2. Epidermis

a. Stratum germinativum

b. Stratum granulosum

c. Stratum corneum

1. Horny scales –Beaver tail

2. Claws, hooves, nails, armadillo shell

3. Horns

a. True horns –Dermal bony core with horny cover; not shed; e.g. antelope horn

b. Hair horns –Males & female rhinos, not shed

c. Antlers and giraffe horns –Bone; velvet is skin which is shed on antlers but not giraffe horns

d. Glands are epidermal in origin

1. Sweat – Sudoriferous –Unique

2. Sebaceous

3. Scent

4. Mammary

e. Hairs

1. Origin –Mechanoreceptors of reptile skin??

2. Shaft

a. Cortex –Pigment present

-cuticle – No pigment; scaly

b. Medulla

3. Root

Follicle has mitosis – bulb is widened area invaded with blood vessels

4. Arrector pili muscle

5. Types

a. Guard

b. Underfur

c. Vibrissae

d. Quills –heaviest hair

3. Dermis

a. Very thick

b. Contents