PREPARED BY: FLORIZA DE LEON, PTRP

INTEGUMENTARY SYSTEM

The integumentary system is the external covering of the chordate body, comprising the skin, its pigments, and various exocrine glands that produce sweat, tears, sebum and other oils, mucous, waxes, scents, and milk. It also includes all derived structures such as hair, feathers, scales, teeth, baleen, nails, claws, horns, beaks, and hooves.

The word integument is derived from the Latin word integumentum , which means “a covering”

The skin is the largest organ in the body; 12-15% of the body weight, with a surface area of 1-2 meters. Its thickness varies from 0.3-4.0 mm depending on the localization on the body. Skin is continuous with, but structurally distinct from mucous membranes that line the mouth, anus, urethra, and vagina

Skin is extremely important to normal physiologic function secondary to the roles that it plays in maintaining homeostasisThe integumentary system serves multiple functions in promoting homeostasis of the body:1. Restricts the movement of fl uids leaving and entering the body2. Cushions and protects vital organs3. Protects the body against abrupt changes in the weather and

helps to regulate temperature4. Helps excrete waste materials through perspiration5. Houses sensory receptors, which inform the brain of external

stimuli6. Provide a front l ine of defense against foreign invaders7. Provides for gaseous exchange (respiration)8. Provides coloration and protection from the sun with skin

pigments9. Generates vitamin D through exposure to UVR10. Stores water, fat, and vitamin D

FUNCTIONS

Types of animals according to regulation of body temperature

Homoiothermus animals – warm-blooded or those with a regulated body temperature because of their heat-conserving bodyEx: birds, mammals

Poikilothermus – cold-blooded animals whose body temperature closely follows that of the environmentEx: fishes

1. Protozoa – with delicate cell membrane. Ex. Amoeba2. Coelenterata – epidermis is made up of single layer

of cells3. Platyheminthes and nemathelminthes – the

epidermis contains a resistant cuticle4. Arthropods and mollusks – epidermis secretes a

protective external skeleton called chitin in insects and shrimps (arthropods) or shells in snails and bivalves

INVERTEBRATE INTEGUMENT

A. The EpidermisThe epidermis is a keratinized stratified squamous epithelium. The main function of the epidermis is to protect the body from harmful infl uences from the environment and against fl uid loss. It is the outermost layer of the skin that varies in thickness (in people) from 0.07-0.12 mm. The palms of the hands average about 0.8 mm and the soles of the feet have a thickness of about 1.4 mm. Its microscopic appearance is that of a keratinized stratifi ed squamous epitheliumContains four main cell types:1. Keratinocytes2. Melanocytes3. Merkel cells4. Langerhans cells

VERTEBRATE INTEGUMENT

There are four principal cells that compose the epidermis. These cells are as follows:1. Keratinocytes – comprise approximately 90% of all

epidermal cells. These cells produce a protein mixture known as keratin which helps waterproof and protect the skin

2. Melanocytes – comprise approximately 8% of all epidermal cells. These cells produce a group of pigments known as melanin which are responsible for skin, hair, and eye color

3. Langerhans cells – these cells arise from the bone marrow and migrate to the epidermis. These cells play an important role in the immune response

4. These cells are located in the deepest regions of the epidermis and are associated with sensory neurons and are thought to function in the sensation of touch

1. Stratum basale- Deepest layer of epidermis- Attached to underlying dermis- Cells actively divide- Contains:

Merkel cells – associated with sensory nerve endingsMelanocytes – secrete the pigment melanin

LAYERS OF THE EPIDERMIS

2. Stratum spinosum (spiny layer)- “spiny” appearance caused by artifacts of histological

preparation- Contains thick bundles of intermediate fi laments

(tonofi laments)- Contains star-shaped langerhans cells

LAYERS OF THE EPIDERMIS

3. Stratum Granulosum- Consists of keratinocytes and tonofi laments - Tonofi laments contain

keratohyaline granules – help form keratinlamellated granules – contain a waterproofing

glycolipid

LAYERS OF THE EPIDERMIS

4. Stratum Lucidum (clear layer)- Occurs only in thick skin- Composed of a few rows of flat, dead keratinocytes

LAYERS OF THE EPIDERMIS

5. Stratum Corneum (horny layer)- Thick layer of dead keratinocytes and thickened

plasma membranes- Protects skin against abrasion and penetration

LAYERS OF THE EPIDERMIS

- Second major layer of the skin- Strong, flexible connective tissue- Richly supplied with blood vessels and nerves- Has two layers:1. Papillary layer – includes dermal papillae2. Reticular layer – deeper layer – 80% of thickness of

dermis

DERMIS

Deep to the skin – also called superficial fasciaContains areolar and adipose connective tissuesAnchors skin to underlying structuresHelps insulate the body

HYPODERMIS

Three pigments contribute to skin color1. Melanin – most important pigment – made from

tyrosine2. Carotene – yellowish pigment from carrots and

tomatoes3. Hemoglobin – caucasian skin contains little melanin

- allows crimson color of blood

SKIN COLOR

Hair Flexible strand of dead, keratinized cells Hard keratin – tough and durable

Chief parts of a hair1. Root – imbedded in the skin2. Shaft – projects above skin’s surface

Hair – three concentric layers keratinized cells3. Medulla – central core4. Cortex – surrounds medulla5. Cuticle – outermost layer

APPENDAGES OF THE SKIN

Hair follicles – extend from epidermis into dermis1. Hair bulb – deep, expanded end of the hair follicle2. Root plexus – knot of sensory nerves around hair

bulb

Types and growth of Hair3. Vellus hairs – body hairs of women and children4. Terminal hairs – hair of scalp; axillary and pubic

area5. Hair thinning and baldness – due to aging; male

pattern baldness

APPENDAGES OF THE SKIN

Occur over entire body, except palms and solesSecrete sebum – an oily substance; simple alveolar

glands; holocrine secretion (entire cell breaks up to form secretion)

Most are associated with a hair follicleFunction of sebum – collects dirt, softens and

lubricates hair and skin

SEBACEOUS GLANDS

Sweat glands (sudoriferous glands) widely distributed on the body

Sweat – is a blood fi ltrate99% water with some saltsContains traces of metabolic wastes

Two types of sweat glands1. Eccrine gland – most numerous – produce true sweat2. Apocrine gland – confined to axillary, anal and

genital areas; produce a special kind of sweat

SWEAT GLANDS

Nails – scale-like modification of epidermisMade of hard keratinParts of the nail1. Free edge2. Body3. Root4. Nail folds5. Eponychium - cuticle

NAILS

Classified severityFirst degree burn – only epidermis is damagedSecond degree burn – upper part of dermis is also

damaged; blisters appear; skin heals with little scarring

Third degree burn – consume thickness of skin; burned area appears white, red or blackened

BURNS