Comparative Anatomy of the Vertebrates: The Integument

1. INTEGUMENT

2. EPIDERMIS
Two kinds of nonliving coverings:
• MUCUS
• STRATUM CORNEUM
Minimizes water loss through skin that is
exposed to air.

3. Epidermal Glands
Fishes
-Most of the integumentary glands are single cells; goblet cells and
granular cells
-Secrete Mucus
-In some multicellular glands, Alkaloids are produced to repel
predators

4. Epidermal Glands
Aquatic Amphibians
-mostly multicellular mucus or granular glands
-keep the skin moist in air, acting as a respiratory membrane
-sometimes serves as holdfast (i.e. frogs and tree toads)
-assist in restraining the female during amplexus (male anurans)

5. Photophores
-light-emitting pigments
-serves for species recognition
-serves as sex recognition, sometimes as a lure or as a warning

6. Keratin
-Most fishes synthesize little or not keratin in their epidermis
-in some aquatic urodeles, have a thin stratum of cornified cells
-in lampreys, conical cornified epidermal spines and “teeth” develop in the buccal funnel
-anuran tadpoles have rows of horny toothlike structures
-generally a feature of the skin of terrestrial craniates than of fishes
and aquatic amphibians.

7. EPIDERMIS OF TETRAPODS

8. Epidermal glands
-SACCULAR OR TUBULAR
-Sacs are known as alveoli
THREE BASIC CATEGORY OF GLANDS (how their cells liberate the substances
they synthesize)
MEROCRINE GLANDS- most common; secrete products via cell
membrane; cell remains intact; Human sweat glands
HOLOCRINE GLANDS- cells constitute secretion; Oil glands and sebaceous
gland of mammals
APOCRINE GLANDS- exhibit intermediate condition; Mammary glands

9. Mucous Glands
Mucus-secreting epidermal glands
-mostly confined to where lubrication is
essential

10. Granular Glands
-present in toads and reptiles, absent in birds and mammals
-secrete toxic alkaloids that are defensive and ward off predators.
-source of many but not all, pheromones
PHEROMONES- substances that affect the behavior or physiology of other
organisms of the same or different species; may signal the sex of an
organism; identify members of the same population; leave trails on a
substrate
PAROTOID GLANDS- secretes toxic substance
FEMORAL GLANDS- secretes substance that hardens to form temporary
spines to restrain females during copulation.

11. AVIAN OIL GLANDS
-found in birds
-secretes oily substance
UROPYGIAL GLAND- prominent swelling at the rump immediately
behind the pygostyle
-abundant in aquatic birds and the domestic fowl
-the secretion is water-repellent; transferred to feathers during
preening.
-smaller oil glands line the outer ear canal and encircle the vent in
some species.

12. SEBACEOUS GLANDS
Alveolar glands with an oily exudate.
-Present with the presence of hairs and secretes sebum, usually exuded into hair follicles.
-In the outer ear canal, CERUMINOUS GLANDS secrete cerumen.
MEIBOMIAN GLANDS assist in moistening the limbs
SCUTES- Large, thin, polygonal scales; found in snakes’ belly for
Locomotion.

13. Claws, Hoofs and Nails
-modifications of the stratum corneum at the end of the
Digits.
Consists of two curved parts:
1) Unguis – horny, dorsal plate
2) Subunguis – softer, ventral plate

14. FEATHERS

15. Morphologic Varieties of Feathers
Contour feathers- gives a bird its contour or general shape. Consists of: 1) a horny shaft and 2)
two flattened vanes.

16. Smooth erector muscles (arrectores plumarum)- enables a bird to fluff its feathers
Down feathers- small, fluffy feathers lying underneath the contour feathers.
Filoplumes are hairlike structures consisting of barbs and associated barbules at the tip.
Morphologic Varieties of Feathers

18. Development of a feather

19. Origin of feathers

20. HAIR

21. Morphology of a Hair

22. Development
of a Hair

23. Origin of Hair
Neomorphs- structures that have no ancestral precursors

24. Horns and Antlers
Horn- means that the surface is composed of keratin.
Three varieties of mammalian horns:
1. Bovine horns
2. Hair horns
3. Pronghorns

25. Bovine Horns and Pronghorns
Abundant in the family Bovidae and pronghorn antelopes
Pronghorns are branched
Present in both sexes
TRUE horns
Consists of: core dermal bone covered by a sheath of horn

26. Hair horns
-Composed of agglutinated keratinized hairlike epidermal fibers.
-Form a solid horn perched on a roughened area of the nasal bone.
-Present in both sexes.

27. Antlers and Giraffe Horns
-Charasteristic of the deer family.
-Not cornified structures but with dermal bone attached to the frontal bone.
-Antlers only develop only in males
-Antlers replaced annually
-Giraffe “horns” are short and bony projections of the frontal bones (remains for life.

28. Other Cornified Structures
Baleen- broad, thin, horny sheets of oral epithelium found in whales aka whalebone

29. Other Cornified Structures
Rattles- rings of horny stratum corneum that remain attached to the tail after each molt. Found
in Rattlesnakes

30. Other Cornified Structures
Beaks- covered with a horny sheath

31. Other Cornified Structures
Combs- covered with a thick, warty stratum corneum.

32. Other Cornified Structures
Ischial Callosities- common in Monkeys and Apes.

33. Other Cornified Structures
Knee pads- on Camels

34. Other Cornified Structures
Tori- epidermal pads that most mammals except ungulates walk on.

35. Other Cornified Structures
Corns & Calluses- temporary thickenings of the stratum corneum that develop where the skin is
subjected to unusual friction.

36. THE DERMIS

37. Dermis
-Composed of collagenous connective tissue
Also includes:
•Blood Vessels
•Small Nerves
•Pigment Cells
And in some:
•Lymphatics
•Naked and encapsulated exteroceptors
•Bases of Hair and feathers
•Erector Muscles

38. The Bony Dermis of Fishes
Dermal Bone- varied in histologic details among many fishes but generally composed of:
1. Lamellar bone
2. Spongy Bone
3. Dentin
4. Enamel-like substance
Denticles- Knobby or spiny elevations of the dentinal layer

40. Dermal Plates and Scales
Classified as:
•Placoid- a dentine crown whith a pulp cavity and covered by enameloid/enamel
•Rhomboid- named after their shape; retain the primitive four layers of dermal bone
•Elasmoid- independently seen in most teleosts, Amia, Latimeria, and dipnoans.

41. Placoid scales
-Found in Elasmobranchs aka today’s sharks, skates and rays.
-Consists of lamellar bone, dentin and enameloid covering.

42. Rhomboid Scales
Classifies as:
Cosmoid- Has Cosmine tissue
that represents a complex
canal system associated with
the dentin and enamel layers.
No living fish has cosmoid
scales anymore.
Ganoid- Has Ganoine, a form
of enamel. Found today only in
basal actinopterygians
Polypterys and Calamoichthyes

43. Elasmoid Scales
Classified into:
Ctenoid- Possesses small spines; found in teleosts
(perciforms)
Cycloid- Composite group of ctenoid-like scales without
the spine; found in Telesosts, Amia, Latimeria and
Dipnoi.

44. Dermal Ossification in Tetrapods
Osteoderms- large bony plates in the dermis.

45. Dermal Pigments
Chromatophores- cells that contain pigment granules. Responsible for skin coloration.

46. Dermal Pigments
Chromatophores- cells that contain pigment granules. Responsible for skin coloration.

47. Chromatophores
-named for the color of their granules.
Melanophores- contain melanin granules;
varying shades of brown
Xanthophores- contain yellow granules
Erythrophores- contain red granules
Iridophores- contain guanine, which reflects
and disperses light and produces silvery skin.

49. Pigmentation of hair and feathers

50. Two structural forms of melanin: