The Integumentary System

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The Integumentary System
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Function

• Protection
• Covers and protects underlying organs from the
  environment.
• Temperature maintenance
• Regulated heat gain or loss to the environment.
• Synthesis and storage of nutrients
• Vitamin D synthesis and large stores of lipids
• Sensory reception
• Detect touch, pressure, pain and relay info to
  nervous system
• Excretion and secretion
• Excretes salts, water and wastes and produces
  milk.

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Components of the Integumentary System
5.
8.
Epidermal ridge
4.
1.
7.
2.
6.
3.
13.
10.
11.
15.
Arrector pilli muscle
12.
14.
9.
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The Integument Structure Overview

• Two main components
• 1. Cutaneous membrane (skin)
• Epidermis - outer
• Dermis - inner
• 2. Accessory organs
• Hair, nails and sebaceous and sweat glands

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The Epidermis outer layer

• Avascular - it has no blood supply of its own
• Oxygen and nutrients diffuse from the underlying
  dermis
• 5 distinct layers can be identified
• Germinativum
• Spinosum
• Granulosum
• Lucidum
• Corneum

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• The stratum germinativum
• is the deepest layer of the epidermis (closest to
  the dermis). It is found close to the dermal
  blood supply. Basal cells are the stem cells of
  the epidermis. Their mitotic activity replenishes
  the cells in more superficial layers.
• Cells die as they are pushed away from the source
  of nourishment. Cells undergo keratinization as
  a tough protein, keratin, is deposited within the
  cell. Keratin hardens and flattens the cells as
  they move outward and it waterproofs the skin.

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Layers of the Epidermis
Shed every 2-4 wks
Oldest cells Lose oxygen supply Lose nucleus

Important evolutionary development
Stratum germinativum
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• In the stratum corneum
• cells are keratinized and form a layer that is
  about 30 cells thick. Individual cells are
  difficult to observe because (1) nuclei can no
  longer be identified, (2) the cells are very flat
  and (3) the space between the cells has been
  filled with lipids, which cement the cells
  together into a continuous membrane.
• Cells are constantly shed from this part of the
  skin. This layer makes up three fourths of the
  epidermal thickness.
• The protection of the body by the epidermis is
  due to the functional features of the stratum
  corneum.

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Layers of the Epidermis
Shed every 2-4 wks
Oldest cells Lose oxygen supply Lose nucleus

Important evolutionary development
Stratum germinativum
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The Dermis

• dense fibrous connective tissue with numerous
  collagenous and elastic fibers.
• The dermis is much thicker than the epidermis.
• Blood vessels, nervous tissue, some muscle
  tissue, certain glands, hair and nails are found
  in the dermis.
• Nerve endings allow us to sense pain,
  temperature, pressure, and touch.

Collagen strong protein fiber
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Other Components of the Dermis

• Blood vessels provide nutrients and remove
  waste, defense and repair
• Lymph vessels defense and repair
• Nerve fibers control blood flow, adjust gland
  secretion rates, monitor sensory receptors

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Red and Orange

• The red and yellow hues of the skin are due to
  hemoglobin in the red blood cells, which pass
  through the capillaries beneath the epidermis,
  and
• carotene (yellowish pigment), which accumulates
  in fat cells found in the dermis and hypodermis
  (subcutaneous layer beneath dermis).

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Melanocytes

• The brown in skin color is due to melanin, which
  is produced in the skin itself in cells called
  melanocytes - located in the epidermis.
• melanin is located in membrane-bound organelles
  called melanosomes.
• Melanin protects the chromosomes of mitotically
  active basal cells against light-induced damage.
• Pigmentation is not just under the control of
  light. Hormones produced by the pituitary and the
  adrenal glands also affect pigmentation.
• Diseases of these two endocrine organs often
  result in changes of pigmentation of the skin.

Melanin pigment
Melanocyte
Nucleus
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Malfunctioning Melanocytes

• Albinism melanocytes completely fail to secrete
  melanin. Hair, skin, and iris are white.
• Vitiligo loss of pigment in certain areas of
  the skin producing white patches.
• Freckles and moles are formed when melanin
  becomes concentrated in local areas.
• Malignant melanoma a cancerous change in a mole
  that may metastasize (spread) rapidly and is most
  difficult to treat. Exposure to sunlight
  increases risk.

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Burns
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First degree burn 

• the mildest type, are usually described as red,
  dry and painful. All but the worst kinds of
  sunburn fall into this category

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Second degree burn 

• wet, red and very painful. Blisters usually form.

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Third and Fourth Degree burn

• Third-degree burns are dry and leathery to the
  touch. The skin is numb, often white and feels
  hard or waxy. These burns do not heal on their
  own.
• Fourth-degree burns involve the tissues beneath
  the deepest layers of the skin, including
  muscles, tendons and even bones.

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Accessory Structures
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Hair Follicles

• Produced in hair follicles
• Invagination of epidermis
• Hair papilla contains capillaries and nerves
• Repeated mitotic division
• As daughters cells are pushed towards surface the
  hair lengthens
• http//www.ingrownhairs.com/flashanimate.html

Hair papilla
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Functions of Hair

• Protect from UV light, cushion, insulation
• Filter foreign particles
• Injury prevention mosquito
• Goose-bumps arrector pilli muscle

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Hair Color and Texture

• Hair color is determined by the amount and type
  of melanin present.
• Melanocytes become less active with age. Gray
  hair is a mixture of pigmented and non-pigmented
  hairs.
• Red hair results from a a modified type of
  melanin that contains iron.
• The shape of the hair shaft determines texture.
• Round shaft straight hair
• Oval shaft wavy hair
• Flat shafts curly or kinky hair
• Perms use chemicals to flatten shafts and makes
  hair curly.
• Alopecia is the term for hair loss.

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Sebaceous Glands

• Oil glands discharge a waxy, oily secretion onto
  hair follicles or skin
• Contraction of arrector pilli squeezes the
  sebaceous gland
• Sebum lubricates hair and skin, inhibits
  bacterial growth
• Accelerated secretion during puberty (acne)

Acne http//www.healthscout.com/animation/68/44/m
ain.html
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Sweat Glands

• Apocrine
• Secrete into hair follicles in armpits, nipples,
  groin
• Sticky secretion that becomes odorous when broken
  down by bacteria

• Merocrine
• 2-5 million
• Palms and soles highest number
• Perspiration to cool skin surface (99 water)

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FUN FACTS!

• House dust is mainly skin flakes!
• If you laid out all your skin on a flat surface,
  it would have an area of about 2 square meters.
• Skin weighs about 2.5 kilograms - the largest
  organ in the body.
• What hurts if you pull it, but doesn't hurt if
  you cut it? Your hair, of course!
• Skin is elastic - it springs back into shape when
  stretched. Some medicines (estrogen, nicotine)
  can pass through the skin, but others cannot
  (insulin). Why is that? Because only fat-soluble
  substances can enter the skin, not water-soluble
  ones.
• Your hair stands on end and you develop 'goose
  bumps' because there are tiny muscles attached to
  the hair follicles and they contract when you are
  frightened or cold.