Integument

Page 1

Function

Keratin

Keratin proteins

Un mineralised

Soft keratin

Hard keratin

Skin glands

Sebaceous glands

Empty into hair follicle

Oil glands

Secrete SEBUM

Oils hairs

Forms an oily film on skin

Lubricates skin

???

Odourless until broken down by bacteria

?

Comparative

None with feathers

Lanolin?

Horn glands of goats

?

Sweat glands

Involved in thermoregulation

Apocrine

Common in domestic species, sparce in primates

Impt in evaporative heat loss

Sympathetic adrenergic

Oily opaque secretion initially dourness but becomes smelly with bacterial breakdown

Ecrine

Common in primates, space in domestic species

Impt in evaporative heat loss

Sympathetic cholinergic

Watery NaCl solution that can be modified by aldosterone

Odourless

Both contain ?

Skin isn't waterproof

Not very permeable but not waterproof + contributes to insensible water loss

Sebaceous gland secretion contributes to water resistance

Keratinocytes

Loosing heat without sweating

Production of melanin

Impt in

Camouflage

Mimicry

Social communication

Protection against harmful effects of solar radiation

Melanocytes

Cell bodies interspersed with other cells in basal layer epidermis

Cell extensions are squeeze between stratum spinous

Melanin is synthesised and packed in vesicles

Intact vesicles are transferred to adjacent keratinocytes = pigmentation of skin + hair

?

Two pigments

Eumelanins

Pheomelanins

Control of pigment ?

Pigment synthesis in melanocytes regulated by melanocyte stimulating hormones (MSH)

Produced by pars intermedia of pituitary gland

Directly by melanocytes

MSH receptors not activated by?

Synthesis of vitamin D

Dietry sources of vit AD

Fat, Liver , blood

Supplementation in commercial food

Synthesised in skin ?

Vit D deficiency

Rickets in camelids

Deformities

Lameness

Require supplementation

Sunburn

Rare in domestics as they are protected by hairs + feathers

They do get Photosensitivisation?

????

Liver damage

Ingestion of poisonous plants

Treatment

Suntan lotion

Out of the sun

Sensory information

Mechanoreceptors

Thermoreceptors

Nocicepters

?

Sensory cells

V superficial

Free nerve endings

Sensitive to

Pain

Temperature

Surrounding hair

Tonic receptors

Fire rapidly when first activated then slow and maintain firing whilst present

Phasic receptors cease firing if strength remains constant

Sensory nerve fibre is affected by stimulation within its receptive field

Action potentials are all or nothing

Brain localises + detects intensity by

frequency of action potentials ,

number of receptors

Different receptors have?

Thermoregulation

Mammals are endotherms - their core temp is stable

Hypothalamus

Increase core temp

Shivering

Vasoconstriction

Hair stands up

Decrease core temp

Sweating

Vasodilation

Hair lies flat

Thermal sensations

Free nerve ending

Epidermis - cold receptors

Dermis - warm receptors

?

Fever

Inc in body temp when the hypothalamic set point temp is shifted to higher value than normal

Thermoregulatory centre interprets a normal temp as being too low = actions shivering

?

Caused by pyrogens

Blood flow

Blood flow to skin can vary widely by a factor of 3-5 depending on the need to dissipate heat?

Sympathetic nervous system also contracts the erector pili muscle

?

Evaporation

Requires hat energy

Contributes to thermoregulation is that due to

Sweating

Panting

Rapid shallow breathing

Not for respiration

Dogs, Cat, Pigs, Ruminants , birds

Natural frequency of ?

Wetting the body

?

Behaviour

Wallowing

Huddling

Seeking shade/shelter

Eating

Thermogenesis

Shivering

Primary involuntary mean of increasing heat production

Antagonistic muscles contract simultaneously

Non shivering

?

Heat input

Animals often put on heat pads as they loose a lot of heat being unable to move

Brown fat

Recently found that it is in adult

?

Thermo-neutral zone

Range of ambient temp without regulatory changes in metabolic heat prod or evaporated heat loss

Animals don't have to expend energy to maintain its normal body temp

Depends on

?

Energy not required to maintain core temp

Cold stress

Temp lower than LCT

Decrease heat loss

Increase heat generation

Heat temp

Increasing heat loss

Decreasing heat generation

Production affected

Page 2

Histology

Integument

Largest + heaviest organ of the body

Includes

Skin

Epidermis

Dermis

Appendages

Hair

Skin associated glands

Nails, Claws, Hoofs, Horns, Beak, Feathers, Scales, Shells

Functions

Protraction

Thermoregulation

Secretion

Sensory

Pigmentation

Motion + shape

Storage

Vit D metabolism

Synthesis + glandular

Immune - surveilance

Capture of prey

ID characteristics

Organisation of skin

Epidermis

Stratified keratinised squamous

Dermis

Vascular connective tissue

Papillary region

Reticular region ?

Hypodermis

Loose connective tissue

Not true part of skin

Embryological development

Epidermis is from ectoderm

Dermis is from mesoderm

Becomes stratified

Accessory structures developed from epidermis

Fully developed at birth

Histology

Invagination of epidermis = epidermal ridge

?

Thick skin vs thin skin

Refers to epidermis not dermis

Presence or absence of hairs

Thick skin

5 layers

Hairless

Thin skin

?

Presence of hair

Epidermis

Stratum corneum

Outermost layer

Flattened cells

Dead

Keratinised epidermal cells

Continuously laughed off

Sratum lucidum

No nuclei

Don't produce keratin anymore

Dead cells

Greatly reduced in thin skin

Translucent keratinised epidermal cells

St granulosum

few layers

Darkly stained , drastic increase in keratinisation

Keratohyaline granules

Highly basophilic

Stratum spinous

Spinous or prickle cell later

Cytoplasm contains tonofilament

Several layers of keratinocytes bound tightly by desmosomes

Stratum basale

Single layer of cuboidal cells

in contact with BM

Stem cells

Divide to form new keratinocytes

In epidermis 90% cells produce keratin

Cells of epidermis

Keratinocytes

Main cell type of epidermis

Stem cells in st basale

Non keratinocytes

Melanocytes

Dispersed between basal cells

Hair follicle

Produce melanin - pigment

UV protection

Coloration

Melanin

Melanosomes

Tyrosinase

Required for production of melanin

Albinos lack this

Merkel cells

Mostly present in basal layer

Sensory

Langerhans cells

Monocytes- derived from dendritic cells

Immune-surveillance cells

Important in antigen presentation

Processes in epidermis

Continuous proliferation of keratinocytes in basal layer

Migration, differentiation + keratinisation

Squamous cells subsequently sloughed off at the surface

Result in formation of relatively impermeable protective layer

Dermis

Vascular dense irregular CT layer of skin

2 layers

Papillary layer

Sub epithelial LCT

Reticular layer

DCT

Contains epidermally derived hair, sweat and sebaceous glands

Blood supply

Epidermis

No vessels

Nourished by diffusion from blood vessels in the dermis

Dermis

Consists of blood, lymphatic vessels and nerves

Artieriovenous anastomosis (thermoregulation)

Shunts blood to bypass capillaries by providing direct routed between arteries + veins

Hypodermis

Subcut layer

Technically not part of skin

LCT , irregular

Connects body + skin

On health animals has large deposits of fat

Accessory structures of the skin

Hairs

Sweat glands

Sebaceous glands

These structures are derived from the epidermis but anchored in dermis

Hairs

Covers entire body in Dom. animals

Excepting

Food pad

Hoof

Glans penis

Mucocutaneous junctions

Teat

Produced by hair follicles embedded in dermis

Functions

Mechanical protection

Thermoregulation

Sensory perception

Type and arrangement of hair follicles varies between species

Hair shaft

Outer cuticle

Single layer

Flat keratinised cells

Cortex

Compact dead cell layer under cuticle

Medulla

Central region of the shaft

Cuboidal/ flat cells

Hair root

Part of hair below surface of skin

Similar structure to hair shaft

Hair bulb

Conical mass at base of hair root

Covered by squamous epithelium.

Epithelium is indented at the base of the bulb by dermal CT - the dermal papilla

Cyclic activity of hair

Anagen = growth

Catagen = regressive/ atrophy

Telogen = Quiescent

Anagen = renewed growth

Types of hair follicles

Sinus or tactile hair = vibrissae

Specialised for tactile sense

Blood filled sinus

Skeletal muscle

Innervation

Limited facial distribution

Extremely large

Single hair follicles grouped in clusters of 2-4 follicles (pigs)

Compound hair follicles (dogs + cats)

Glands

Sebaceous

Exocrine gland

Sebum

Waterproofing

Increasing agility

Spread sweat

Secretory portion

Pale staining

Flask shaped

Holocrine method

Whole cell disintegrates to release sebum

Excretory duct

Empties into hair follicle

Sweat

Exocrine gland

Sweat

Ultrafiltrate of blood plasma

Functions

Thermoregulation

Excretion

Scent signalling

Secretory portion

Simps cuboidal epithelium

Myoepithelial or basket cells

Apocrine or meocrine?

Excretory duct

2 layers of cuboidal epithelium

Hair follicle / sweat pore

Mammary glands = modified sweat glands

Ecrine

Apocrine

Clinical relevance

Indicator of systemic conditions

Economic significance

Skin incised in almost all surgical procedures

Pathological conditions

Allergies

Dermatitis

Parasitic infection

Hyperkeratosis - hard pad disease?

Melanoma

Squamous cell carcinoma

Burns

First degree

Sun burn

Epidermis affected

Second degree

Blisters

Epidermis + dermis affected

Third degree

Epidermis + dermis + subcutaneous layer affected

Cornified epidermal structures

Hooves, Claws and horns in mammals

Claws in

Beaks in

Shells + scales in

Scales in ??

Vestigial toe?

Feathers

Contour feathers

Downs

Filoplumes

??