Integumentary+System

=__THE INTEGUMENTARY SYSTEM__=

__Functions of the system__
Protection, Thermoregulation , Sensation , Excretion , Metabolic functions , Blood shunting mechanism

__**Components**__
Skin, Hair, Nails , Connective Tissue , Muscle , Nerves, Lymph - & Blood Vessels , Glands

Epidermis.
Stratum corneum, Stratum Lucidum, Stratum Granulosum , Stratum spinosum, Stratum Germinativum = Stratum Basale

SB contain melanocytes that produce the pigment melanin

Keratinocytes - keratin for protection

Langerhans cells - immune response to invaders of the skin

Merkel cells - associated with disc-like ending of sensory nerve

No nerves or blood vessels in this layer

Dermis.
Papillary layer: fits into stratum basale of epidermis - thin layer

Reticular layer: about 80% of dermis. Contains most of the structures located in the skin:

Hair follicles, blood vessels, receptors, nerve fibres, eccrine and

apocrine glands (sweat glands), sebaceous glands, arrector muscles

Hypodermis [Subcutaneous layer] - technically not part of the skin.
Major structural components are:


 * Areolar connective tissue and adipose tissue.


 * Anchors the skin through collagenous and elastic fibres that

run continuously through these two layers.


 * Adipose tissue helps to conserve body heat.

__Skin Colour__
melanin - primary pigment - genetically determined basically but may change depending on environment. ; haemoglobin - blood in skin - temp. dependent Abnormalities in skin colour

Lack of oxygen [vasoconstriction and capillary shunting in cold weather] may leave the skin purplish-blue = cyanosis. This condition can also be detected under nails.

If well oxygenated or in hotter weather with vasodilation, skin appears reddish = erythema

Pallor - whitish-grey skin appearance may result due to acute vasoconstriction due to shock, anger, fear, fainting spell, etc.

Unpigmented parts of the skin may appear yellow due to accumulation of carotene - ingested foods such as carrots, pumpkin etc.

Jaundice is another condition that leaves the skin yellow due to accumulation of bile pigments when the liver is not functioning properly.

Bronzing can be a sign of Addison’s disease [hypofunctioning of the adrenal cortex]. This should not be confused with modern-day bronzing creams for sun-tanning.

__HAIR and NAILS__
Bodily hair are outgrowths of the skin.

Study the diagram of the skin and the functions of all the parts of the Hair and Nails.

Functions of: eyebrows, lashes, moustache, beard , nose hairs, ear hairs etc.

Glands are all EXOCRINE
Sebaceous - oil - sebum. hyperactivity can result in Whiteheads, blackheads, acne, seborrhea

Sweat - eccrine/merocrine, apocrine Modified: ceruminous (wax)

mammary (milk producing)

THERMOREGULATION

Norm: ~37 oC. thermostat in Hypothalamus




 * Sweat glands** ...................................................................................................... **Blood vessels**

Hot: Bv dilate, more blood in skin, more............................................................. Hot: vasodilation -more blood near skin surface - heat liberated from body

sweat secreted, Evaporation cools

Cold: Converse ................................................................. ........... Peripheral capillary shunt

Hot: Arrector musc relax hairs flat on body
 * Hairs**

Cold: Arr musc contract airs erect, trap air

Chemical Barriers ............................................................................... Physical/Mechanical
Acid mantle retards repro - human defensin ............................ keratinized layer - water proofing both ways, blocks Melanin - blocks UV rays ............................................................................... microorganisms

Biological Barriers ...............................................-- Hairs
Langerhans cells, Macrophages : both antigen presenters ........................................... Warns of insects, Clustering/patching warns of disease -alopecia

DNA = UV dissipators

__CUTANEOUS SENSATION__
Sensory receptors: Meissners corpuscles & Merkel’s discs = touch- light to moderate

Pacinian corpuscles = pressure - heavy touch to gripping

Ruffinian corpuscles = heat receptors

Krause corpuscles = cold receptors

Free nerve endings = pain. Conc. at hair follicles and under nails (torture)

At hair follicle - slight movement of air.

__Metabolic Functions__
Formation of Vitamin D ,

Enzymes in keratinocytes can neutralize some carcinogenic chemicals and converse

and activate steroid hormones s.a. in topical applications (cortisone creams)

Formation of collagenase - recycling of collagen

Shunting of blood

__SKIN CANCER__
What is skin cancer.

Latest treatments - delivery of DNA-repairing enzymes through liposomes in lotions

Types of Cancer: Basal Cell carcinoma



Squamous Cell carcinoma



Melanoma: signs of melanoma to distinguish from normal moles. [ABCD]

__BURNS__
RULE OF 9's:

Distinguish between first, second and 3rd degree burns.

Precautions [infections, fluid loss] and treatments - keep in mind precautions

Prognosis/seriousness.

__WOUND HEALING__
Because the skin is our barrier to the environment, it is often ‘traumatized’ by environmental factors, be it natural, human errors or human malicious behaviour.

The layers that are affected during skin tissue trauma will determine the period for healing and the type of intervention mechanisms required.

__Natural progression of wound healing__
1. Inflammation: Haematoma, swelling & erythema,

2. Granulation and Organization: scab formation, capillary extension, elastic and collagen fibres deposited, cell replacement (mitosis), sealing of internal ‘gaps’

3. Regeneration and Reorganization: Tissue under scab reorganizes, drains and smooths.

Superficial scrapes or cuts can heal within a few days.

Trauma into the lower layers of the dermis can take up to ten days to heal.

Deep cuts need to be attended to by specialised human intervention. ‘Natural’ healing can lead to infections and pus formation if not cared properly. This can prolong the healing process tremendously.

__Aided wound healing (human intervention)__
An open wound, if into dermis, is best treated by covering up the wound. It may not need special chemicals to aid the healing, but infections should be avoided.

“If you put on a plaster, it will heal faster” is a true, helpful cliché.

Keep the wound DRY at all times - dry bandage, dry plaster etc. and do NOT wash the affected area. It disturbs the process of reorganization and may lead to scar tissue forming.

If it requires chemicals - a good antiseptic cream should do the trick. Do not disturb if not necessary. A well rested tissue can heal twice as fast without scarring. NB** If the wound was gaping and no care was taken to bring the two uppermost layers together, dermal tissue and accelerated keratinocytosis may result in a smooth layer of cells plugging the gap, forming a scar for life. No ‘wrinkling’ as with normal skin is visible, thus the area is also less flexible than the rest of the skin. This is because of excessive collagenous fibres being deposited to help ‘close the gap’ as soon as possible. [This is for healing of skin tissue only. Other trauma’s dealt with in chapters] Some questions

Explain the Peripheral Capillary shunt mechanism in thermoregulation across a variety of temperatures.

Elucidate the concept of feedback as it pertains to thermoregulation

Does hyperventilation act as a thermoregulatory mechanism ? Explain.

Sweat is considered an excretion as well as a secretion. Explain why this is so.

Describe the role of four different types of glands found in the skin.

Why does scar tissue form after even a small wound?

How can a normal mole be distinguished from a malignant melanoma?