1. Integumentary System Colville & Bassert Chapter 6: p122-141 Mammals
Chapter 17: p Birds

2. Skin Functions Protects deeper tissues from: Aids in: Makes Vitamin D
Mechanical damage
Chemical damage
Damage from micro-organisms
Damage from heat and Ultra violet radiation
Drying out
Aids in:
Heat regulation
Excretion (of metabolic wastes)
Makes Vitamin D
Storage organ – whales & blubber (Fat = insulation)
Sexual attraction – scent, colour

3. Skin Structure Three layers: Epidermis – outer layer
Stratified squamous epithelium
Often keratinized (Hardened by keratin)
Dermis – middle layer
Dense irregular connective tissue
Hypodermis, Subcutaneous layer – innermost layer
Anchors the skin to underlying organs
Mainly adipose tissue

4. Skin Structure Outside the body Epidermis Dermis Hypodermis
Deeper tissues

5. Epidermis – 3 layers
Made of keratinised stratified squamous epithelium
Outer waterproof layer
Thickness varies between animals & parts of body
Keratinocytes thin layer along basement membrane continually dividing and push older layers up
Inner layer (next to the dermis)
Stratum basale
Keratin deposits increase & without nutrients cells rarely divide & cytosol, nuclei and organelles gradually disappear from cells.
Cells begin to die
Middle layer – 3 sublayers can be present
Up to ¾ of the total thickness of epidermis – lifeless sheets of keratin
Dead cells on surface separate and rub off
These are replaced from below
Outer layer
Stratum corneum
Keratinocytes located along basement membrane – plenty of blood supply from dermis) secrete keratin (tough, fibrous, waterproof protein)

7. Specialised cells found in the epidermis
Keratinocytes (covered above)
Produce keratin
Melanocytes
Produce melanin
Langerhans cells
epidermal macrophages
Engulf foreign material
Merkel cells (Mechanical receptors)
Surround nerve endings at the junction with the dermis to form Merkel discs

8. Skin Structure: Epidermis/Dermis

9. Dermis – 2 layers
Papillary Layer - next to epidermis, is loose connective tissue, contains:
Pain receptors
Capillaries
Projections called dermal papillae
Reticular layer (dense connective tissue) contains:
Blood vessels
Glands
Nerves
Fibres in both layers provide strength, support, cushioning and flexibility

10. Hypodermis – Subcutaneous layer
Layer under the dermis
Rich in adipose tissue (fat), blood & lymph vessels, touch receptors
Attaches the dermis to underlying structures
Allows skin to move freely over the underlying structures
Insulation
Shock absorption

11. Name the structures and layers

12. Associated structures of the skin
Keratin structures
Hair/ fur/ wool/ spines
Hooves, claws, pads
Horny scales, snake skin, bird’s legs, rat’s tails
Horns, Antlers
Bills or beaks
Feathers

13. Hair
Most hairy skin has relatively thin epidermis Epidermis of ‘hairy skin’ is covered in scale-like folds Hair comes from under the scales and points away from the opening Dogs have 3 hairs emerging from each follicle Hair – provides warmth and protection. Eyelashes and nose hairs have a protective function Hair pigment is produced by melanocytes at the base of the hair follicle. Grey or white hair results from a decrease in melanin production.

15. Dogs have 3 hairs emerging from each follicle
Hair – provides warmth and protection. Eyelashes and nose hairs have a protective function
Hair pigment is produced by melanocytes at the base of the hair follicle. Grey or white hair results from a decrease in melanin production.

16. Hair follicle
Extends down into dermis layer and the deep end is a bulb.
As new hair cells are produced by the base, the older part of the hair is pushed upward, and fused cells die off.
Each follicle is supplied with sebum from a sebaceous (oil) gland, this often:
Softens and lubricates the skin.
Kills bacteria

17. Appendages of the Skin - Hair
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18. Hair follicle bulb

21. Skin Structure
Figure 4.4
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22. Cortex surrounds medulla Cuticle on outside of cortex
Hair Anatomy
Central medulla
Cortex surrounds medulla
Cuticle on outside of cortex
Most heavily keratinized
Figure 4.7b
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23. Associated Hair Structures
Hair follicle
Dermal & epidermal sheath surrounds hair root
Arrector pilli
Smooth muscles –pulls hair (fur) erect
Sebaceous gland
Lubricates hair
Sweat gland
Secretes waste products & moisture

24. Guard Hairs
longer forming the top coat these have a smooth muscle which allow the hairs to stand up

25. shorter, softer, many hairs per follicle providing a dense look
Wool Hairs
shorter, softer, many hairs per follicle providing a dense look

26. Whiskers, these are specialised and aid direction.
Vibrissae
Whiskers, these are specialised and aid direction.

27. Nails, Claws & Hooves
Scale like modification of the epidermis. Grows from the bottom where the white crescent is a thickened area of skin.

30. Pads
Modifications of the skin on the feet to provide protection for those areas that come in contact with the ground. They are covered by a hairless, densely keratinized epidermis area. Pads are mainly made up from thickened hypodermis containing many collagenous and elastic fibres interspersed with adipose tissue. Both cats and dogs have sweat glands on nose and pads.

31. Horns are paired and protrude from the front of the skull
Horns & Antlers
Horns are paired and protrude from the front of the skull
They are unbranched and epidermal in origin
Made up of a bony core and a keratinized sheath.
Mature horns are hollow and composed of keratin
In most animals they grow throughout life – not shed
Antlers are also paired structures that protrude from the front
They are branched and dermal in origin
Primarily in males
They are shed annually;
American proghorn sheds its horns anually
Antlers grow from pedicels, which are bony supporting structures that develop in the lateral region of the frontal bones. Secretions from the pituitary initiate the growth in April or May. In the northern hemisphere increasing day length also plays a role. Early in their development, antlers have high water and protein content. As they grow, antlers are covered with skin and soft hair called velvet, which carries blood vessels and nerves. As antlers near the end of the growing process, spongy bone in their outer edges is replaced by compact bone, while their centers become filled with coarse, spongy, lamellar bone and marrow spaces. The velvet dies and is removed in part by the animals rubbing and thrashing their antlers against vegetation. The antlers also are stained during this action, giving them the brown, polished, wooden look.

32. Other types of horns
Giraffe horns are paired, short, unbranched, permanent, bony processes that are covered with skin and hair.
They differ from other horns in that they do not project from the frontal bones, but lie over the sutures between the frontal and parietal bones.
Giraffe horns begin as cartilaginous structures in the fetus and may not fuse to the cranium until the animal is 4 years old.
Horns are present in both sexes of giraffes and even on newborns.

33. Other types of horns Rhino horns have no core or sheath.
They are made up of multitude of epidermal cells and bundles of dermal papillae,
Cells from each papilla form a horny fibre These are held together by the mass of epidermal cells, are not true hairs.
Rhino horns grow from dermal papillae which extend up into the horn.
The rhino horn is situated over the nasal bones.
In species that have two horns, the second horn lies over the frontal bones.

34. Skin Colouration
Colour is due to pigments that either reflect or refract light. Often found within the epidermis layer, feathers or hair. Cuttlefish have special cells called chromatophores. Some animals chromatophores produce a range of different colours

35. http://www. youtube. com/watch
Pigment cells have sphincter muscles and can squeeze the pigment up into disc near the surface. When muscles relax the colour runs down into the cell Cuttlefish with this ability can generate a wide range of colors and many interesting patterns. By perceiving the color of a backdrop and constricting the right combination of chromatophores, the animal can blend in with all sorts of surroundings. Cuttlefish may also use this ability to communicate with each other.

36. Colour Colour is used for: Concealment
In most cases, either changing amounts of daylight or shifts in temperature trigger a hormonal reaction in the animal that causes it to produce different biochromes.

37. Where is the frog?

38. A leafy sea dragon, photographed off the coast of Australia
A leafy sea dragon, photographed off the coast of Australia. Leafy sea dragons have developed flowing appendages and vivid coloration that lets them blend in with the undersea plant life in their environment.
Leafy Sea Dragon
flowing appendages and vivid coloration that lets them blend in with the undersea plant life

39. Communication
Colour often serves as social communication, help members of the same species identify individuals, their gender, reproductive status, social rank etc..
bright yellow color of the male American goldfinch. Many male bird's, like the northern cardinal,

40. Often changes colour
Depending on environmental and social cues - temperature
Not always to blend in with the environment
the chameleon, alters its skin color using a similar mechanism, but not usually for camouflaging purposes. Chameleons tend to change their skin color when their mood changes, not when they move into different surroundings.

41. Melanin
Pigment (melanin) is produced by Melanocytes found in deepest epidermal layers (only type of chromoatophore in mammals)
Cells have long projections from which melanin is released and absorbed by keratinocytes.
Colour is yellow to brown to black
Most melanocytes are in the innermost layer of the epidermis
The amount of melanin depends on the inheritance of the animal and the exposure to sunlight

42. Structures of the Skin - Glands
Located in dermis but really invaginations of epithelium from epidermis
Sebaceous glands
Produce oil
Lubricant for skin
Kills bacteria
Most with ducts that empty into hair follicles
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43. Structures of the Skin - Glands
Sweat glands
Widely distributed in skin
Two types
Eccrine
Open via duct to pore on skin surface
Apocrine
Ducts empty into hair follicles
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44. Sweat and Its Function Composition Function
Mostly water
Some metabolic waste
Fatty acids and proteins (apocrine only)
Function
Helps dissipate excess heat
Excretes waste products
Acidic nature inhibits bacteria growth
Odour is from associated bacteria
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45. Circumoral glands: in lips of cats – secretion to mark territory.
Other Skin Glands
Circumoral glands: in lips of cats – secretion to mark territory.
Tail glands: gland found on the dorsal side of the tail in some carnivores
Circumanal glands: in the skin of dogs
Glands of the anal sacs: scent glands- secreted after faeces
Mammary glands: covered in reproductive system