Transcript Slide 1

INTEGUMENTARY SYSTEM
 The
integumentary system comprises
the skin with its adnexal structures (e.g.
hair and glands), horns, hoofs, claws,
and other modifications of the epithelial
covering of the body
 All the components of integument are
modification of the surface epithelium.
SKIN
 largest
organ in the body: 12-15% of
body weight, with a surface area of 1-2
meters sq.
 Continuous with, but structurally
distinct from mucous membranes that
line the mouth, anus, urethra, and
vagina.
 Two distinct layers occur in the skin:
1. Epidermis.
2. Dermis
1.Epidermis:
Avascular layer, no nerve endings.
Divided histologically into (deep to
superficial):
1. Stratum basale-mitotically active cells.
2. Stratum spinosum-spiny appearance
due to inter-cellular bridges.
3. Stratum granulosum-spindle shaped
cells
4. Stratum lucidum
5. Stratum corneum-layer of dead
flattened cells.
2. The dermis
A connective tissue layer under the
epidermis, and contains nerve endings,
sensory receptors, capillaries,
lymphatics and elastic fibers.
3. Hypodermis
 A layer of loose connective tissues
seperating skin from underlying
tissues.
 Allows movement of skin without
tearing.
 Varying amount of fat is found in this
layer.
FUNCTIONS OF SKIN
 Protection
 Thermoregulation
 Sensory
reception
 Water balance
 Synthesis of vitamins and hormones
 Absorption of materials.
Protection:
 Serve as a barrier to the entry of
microbes.
 Prevent water and extracellular fluid
loss.
 Acidic secretions from skin glands also
retard the growth of fungi.
 Melanocytes - second barrier:
protection from the damaging effects of
ultraviolet radiation.
Skin and Water balance:
 Evaporation
 Sweating
 In hot weather up to 4 liters per hour
can be lost by these mechanisms.
 Skin damaged by burns is less effective
at preventing fluid loss, often resulting
in a possibly life threatening problem if
not treated.
Skin and Thermoregulation:
 Heat and cold receptors - located in the
skin.
 When the body temperature rises-the
hypothalamus sends a nerve signal to
the sweat-producing skin glandsrelease about 1-2 liters of water per
hour- cooling the body.
 The hypothalamus - causes dilation of
the blood vessels of the skin-more blood
to flow - heat convected away from the
skin surface.
 When
body temperature falls-sweat
glands constrict and sweat production
decreases.
 If the body temperature continues to
fall, the body will engage in
thermiogenesis, or heat generation, by
raising the body's metabolic rate and
by shivering.
Skin and Sensory Reception :
 Sensory receptors -pain, pressure
(touch), and temperature.
 Deeper within the skin are Meissner's
corpuscles, -in the tips of the fingers
and lips-very sensitive to touch.
 Pacinian corpuscles respond to
pressure.
Skin and Synthesis:
 Skin cells synthesize melanin and
carotenes, which give the skin its color.
 Also assists in the synthesis of vitamin
D.
 Children lacking sufficient vitamin D
develop bone abnormalities known as
rickets.
Skin and absorption:
 Skin
-selectively permeable to fat-soluble
substances such as vitamins A, D, E, and
K, as well as steroid hormones such as
estrogen.
 Enter the bloodstream through the
capillary networks in the skin.
 Patches have been used to deliver a
number of therapeutic drugs in this
manner. These include estrogen,
scopolamine (motion sickness),
nitroglycerin (heart problems), and
nicotine (for those trying to quit smoking).
GLANDS
Sebaceous gland Empty oily secretion called sebum into
hair follicles.
 Some empty directly onto the surface of
the skin-ear cannal, around anus, in
the penis, prepuce, vulva.
Specialized sebaceous glands:
 Marking glands
 Characteristic of their species.
 Sheep:
1. Infra-orbital pouches-in the medial
canthus of eyes
2. Inter-digital pouches-on the midline
above the hooves.
3. Inguinal pouches-Naer the base of the
udder or scrotum.
 Goat-horn
glands- Located Caudal to
the base of the horns. Secretions
becomes more in breeding seasons
giving pungent smell of bucks.
 Pigs-carpal glands- Located on the
medial aspect of the carpus.
Sudoriferous glands/ Sweat glands
 Tubular glands found all over the body.
 Well developed in horses.
 Sparse in cow, sheep and pigs.
 Mammary gland is modification of
sweat gland.
HAIR
 Defining
characteristic of mammals
 Three main types of hair on domestic
mammals:
1. Guard hairs, which form the smooth
outer coat
2. Woolhairs, also called the undercoat,
which are fine and often curly.
3. Tactile hairs, long stiff hairs with
specialized innervation that renders
them effective as organs of touch.
 An
individual hair arises from a
modification of the epidermis, the hair
follicle.
 An individual hair has a medulla at its
center, surrounded by a scaly cortex,
outside of‘ which is a thin cuticle.
 The bulk of the hair comprises the cortex.
 All
parts of the hair are‘ composed of
compressed, keratinized epithelial
cells.
 The amount and type of melanin in
cortical cells determine whether the
hair will be black, brown, or red.
 Wool hairs lack a medulla or have only
a very small one, accounting for their
fine, flexible nature.
 Cuticle is a single layer of thin, clear
cells covering the cortex.
 Arrector
pili muscle-A tiny bundle of
smooth muscle that extends from the
deep portion of the hair follicle at an
angle towards epidermis.
 Contraction of this muscle raises the
hair to 90 degrees. This increases the
insulation property during cold
exposure and also increases apparent
size of the animal to the oponent
during fight-or-flight reaction.
 Contraction of this muscle also
compresses the sebaceous glands and
helps in emptying it.
MODIFIED EPIDERMIS
Hoof
 A defining characteristic of ungulates
 Ungulates- well-developed hoof
associated with the distal phalanx.
 Although the hoofs of pigs, ruminants,
and horses differ significantly in their
gross appearance, they share certain
features.
COMMON FEATURES
 Have
an outer avascular epidermal layer
and an inner vascularized dermis
 The dermis of hoofs and horns are
commonly called as corium.
 The outside -covered by a thin, waxy layer
called the periople.
 The thick hoof wall grows from a belt of
epidermis at the coronary band.
 The deep side of the hoof wall is
intimately connected to the underlying
corium, which blends with the periosteum
of the distal phalanx.
HORNS
Formed over the cornual process-from the frontal
bone of the skull
 Animals that lack horns naturally are called
polled.
 The corium of the horn completely envelops the
comual process and blends with its periosteum.
 The hom itself consists of dense keratin, much
like the hoof wall, and elongates from the base.

Dewclaws
 The accessory digits
 Ruminant dewclaws do not bear
weight.
 Dairymen occasionally have the
medial dewclaws on the pelvic limbs
removed-prophylactic measure against
injury to the udder
 Porcine dewclaws occasionally make
contact with the ground when the pig
stands on soft surfaces.
Chestnuts and Ergots
 Chestnuts are hornlike growths on the
medial sides of horses' limbs.
 Ergots are small projections of
cornifined epithelium in the center of
the palmar (plantar)part of the fetlock
of the horse. The tuft of hair at the
fetlock hides the ergot in most
instances