These slides contain the information regarding the various integumentary system of the living organisms. The data is retrieved from Hickman's Integrated Principles of Zoology

2. Integument among Various Groups of Animals
• Integument: Outer covering of the body
 Protective wrapping including skin and all structures
derived from or associated with it
 Hair, setae, scales, feathers, and horns
• In most animals it is tough and pliable, providing
mechanical protection against abrasion and puncture
• Forms an effective barrier against invasion of bacteria
• May provide moisture proofing against fluid loss or
gain

3. Skin
• Helps protect the underlying cells against the damaging
action of the ultraviolet rays of the sun
• It serves a variety of important regulatory functions
 In endothermic animals, it is vitally concerned with
temperature regulation
 Contains sensory receptors that provide essential
information about the immediate environment
 Has excretory functions and in some animals respiratory
functions as well
 Through skin pigmentation the organism can make itself
more or less conspicuous
 Skin secretions can make the animal sexually attractive or
repugnant
 Provide olfactory cues that influence behavioral
interactions between individuals

4. Invertebrate Integument
• Many protozoa have only the delicate cell or plasma membranes for
external coverings
• Paramecium, have developed a protective pellicle
• Most multicellular invertebrates, however, have more complex
tissue coverings
 The principal covering is a single-layered epidermis
• Some invertebrates have added a secreted non-cellular cuticle over
the epidermis for additional protection
• The molluscan epidermis is delicate and soft and contains mucous
glands, some of which secrete the calcium carbonate of the shell
• Cephalopod molluscs (squids and octopuses) have developed a
more complex integument, consisting of cuticle, simple epidermis,
layer of connective tissue, layer of reflecting cells (iridocytes), and
thicker layer of connective tissue

6. • Arthropods have the most complex of invertebrate
integuments, providing not only protection but also skeletal
support
 Development of a firm exoskeleton and jointed appendages
suitable for attachment of muscles has been a key feature
in the extraordinary diversity of this phylum
 Their integument consists of a single-layered epidermis
(also called more precisely hypodermis)
 Secretes a complex cuticle of two zones:
1. Thicker inner zone, the procuticle, is composed of protein
and chitin laid down in layers much like veneers of
plywood
2. Outer zone of cuticle, lying on the external surface above
the procuticle, is the thin epicuticle, a non-chitinous
complex of proteins and lipids that provides a protective
moisture-proofing barrier to the integument

7. Arthropod Integument

8. • Their cuticle may remain as a tough but soft and flexible
layer, as it is in many microcrustaceans and insect larvae
 It may be hardened by either of two ways:
1. In the decapod crustaceans, for example, crabs and
lobsters, the cuticle is stiffened by calcification
2. In insects hardening occurs when protein molecules bond
together with stabilizing cross-linkages within and
between adjacent lamellae of the procuticle
• Result of this process, called sclerotization, is formation of a
highly resistant and insoluble protein, sclerotin
• Arthropod cuticle is one of the toughest materials
synthesized by animals
 Strongly resistant to pressure and tearing and can
withstand boiling in concentrated alkali, yet it is light,
having a specific mass of only 1.3 (1.3 times the weight of
water)

9. • When arthropods molt, the epidermal cells
first divide by mitosis
Enzymes secreted by the epidermis digest
most of the procuticle
Digested materials are then absorbed
In the space beneath the old cuticle a new
epicuticle and procuticle are formed
After the old cuticle is shed, the new cuticle is
thickened and calcified or sclerotized

10. Vertebrate Integument and Derivatives
• The basic plan of the vertebrate integument includes a thin,
outer stratified epithelial layer, the epidermis, derived from
ectoderm and an inner, thicker layer, the dermis, or true skin,
which is of mesodermal origin
• Although the epidermis is thin and appears simple in
structure, it gives rise to most derivatives of the integument,
such as hair, feathers, claws, and hooves
• The dermis contains blood vessels, collagenous fibers, nerves,
pigment cells, fat cells, and connective tissue cells called
fibroblasts
 These elements support, cushion, and nourish the epidermis,
which is devoid of blood vessels

12. • The epidermis is a stratified squamous epithelium
consisting usually of several layers of cells
 The basal part is made up of cells that undergo
frequent mitosis to renew layers that lie above
 As outer layers of cells are displaced upward by new
generations of cells beneath, an exceedingly tough,
fibrous protein called keratin accumulates in the
interior of the cells
 Keratin replaces all metabolically active cytoplasm
 Cell dies and is eventually shed, lifeless and scalelike
 This process is called keratinization, and the cell, thus
transformed, is said to be cornified

14.  Cornified cells, highly resistant to abrasion and water
diffusion, comprise the outermost stratum corneum
 This epidermal layer becomes especially thick in areas
exposed to persistent pressure or wear such as
calluses, foot pads of mammals, and the scales of
reptiles and birds
• The dermis mainly serves a supportive role for the
epidermis
• True bony structures, where they occur in the
integument, are always dermal derivatives
• Heavy bony plates were common in ostracoderms and
placoderms of the Paleozoic era and persist is some
living fishes, such as sturgeons

15. Ostracoderm
Placoderm

16. Sturgeon (Bony fish)

17. • Scales of contemporary fishes are bony dermal
structures that have evolved from the bony
armor of the Paleozoic fishes but are much
smaller and more flexible
• Fish scales are thin bony slivers covered with a
mucus-secreting epidermis
• Most amphibians lack dermal bones in their skin
• In reptiles dermal bones provide the armor of
crocodilians, the beaded skin appearance of
many lizards, and also contribute to the shell of
turtles
• Dermal bone also gives rise to antlers, as well as
the bony core of horns

19. • Structures such as claws, beaks, nails, and horns
are made up of combinations of epidermal
(keratinized) and dermal components
Their basic structure is the same, with a central
bony core covered by a vascularized nutritive
layer of the dermis, and an outer epithelial layer
This epithelial layer has a germinative component
responsible for the continual growth of horns,
hooves, claws, and beaks
The outer epithelial layer is keratinized
Overgrowth of these structures is prevented by
constant wear and abrasion