Chapter 5 (lectures)

7%

integumentary system makes up hat percent of body mass?

Skin (integumentary system)

Largest organ in the body

1. Epidermis

2. Dermis

3. Hypodermis is underneath but not technically part of system

Two layers of integumentary system

Keratinized cells

Cells filled with soft keratin, making them waterproof and durable

keratinized stratified squamous

Cell type in epidermis

every 25-45 days. skin is constantly shedding cells

How often is epidermis replaced

1. Melanocytes: produce melanin in skin (skin colour)

2. Merkel cells: sensory function, able to sense touch/pressure

3. Dendritic cells: Involved in immune responses in skin

4. Keratinocytes: most abundant type of cell in skin. Produces keratin, provides protection.

Four types of epidermal cells

1. Stratum corneum

2. Stratum lucidim (only preset in thick skin)

3. Stratum granulosum

4. Stratum spinosum

5. Stratum basal

Five layers of epidermis

Dermis

Strong, flexible connectice tissue layer between epidermis and hypodermis. Forms the bulk of the thickness of the skin. Anchors the accessory structures in the integument

1. Papillary (superficial)

2. Reticular layer (deep)

Two layers of dermis

Nourishes epithelia and regulates temperature

Two purposes of blood supply in dermis

Papillary Layer

Forms dermal papillae - finger-like projections. Branch up into epidermis, prevents dermis from sliding on epidermis. 20% of thickness of dermis

1. Areolar connective tissue; small vessels and nerves

Tissues in papillary layer

Reticular layer

Layer of dermis that contains larger blood vessels, nerve fibers, lymph vessels, and accessory structures

1. Dense Irregular connective tissue

   1. Has collagen fibers and elastin fibers. Collagen provides strength and retaining moisture. Elastin fibers give flexibility

Tissues in reticular layer

Cleavage (tension) lines

Lines on body formed where collagen fibers are less dense. invisible from the outside. surgeons cut along these lines so it heals quicker.

Flexure lines

Lines in hands. Wrinkles/lines in knuckles and palm of hand. Deep creases in skin near joints. The dermis is more firmly attached to underlying structure and doesn’t move as freely. Also in knees, feet, elbows.

Fingerprints

lines on fingertips. Originate in dermal papillae, causes ridges/indentations. Those indentations carry up to outer surface. There to increase friction and help with gripping.

Hypodermis or subcutaneous layer

Below dermis, anchors dermis to underlying structures.

Allows skin on top to move separate from underlying tissues.

Site for SQ injections (few large vessel and no vital structures)

Consists mainly of adipose tissue, provides cushioning and insulation.

Main tissue in hypodermis

1. Amount of melanin

2. Carotene: orange pigment in vegetables

3. Hemoglobin: pink colour due to red blood vessels in capillaries that are in dermis

Three factors that determine skin colour

lack of oxygen in blood

Blue skin is a symptom of..

accumulation of bilirubin in the body, due to improper liver function

Yellow skin is a symptom of…

bruising due to blood vessels being damaged and leaking blood into tissues

Brown, yellow/ blue marks on skin are signs of…

being scared or emotionally stressed. blood can be diverted from skin to internal organs.

Pallor/ blanching (pale skin) is a sign of…

1. Hair and hair follicles

2. Sweat glands

3. Sebaceous (oil) glands

4. nails

Four types of skin appendages located in dermis

1. Vellus hair

2. Terminal hair

Two main types of hair

Vellus hair

Fine, pale bod hair found in children and adult females

Terminal hair

Coarser, longer hair of eyebrows, eyelashes, and scalp. Appears in axillary and pubic area at puberty, and of face, chest, arms, and legs (males)

Hard keratin

Cell in which hair is made of. Cells do not flake off, and are more durable than cells in epidermis.

1. Scalp: four years

2. Eyebrows: a few months

How long is lifespan of hair (scalp and eyebrows)

Shape of hair shaft

What determines hair type?

Nails

 modified epidermis

Dorsal surface of distal aspects on fingers and toes

Made of hard keratin (does not flake off)

Eccrine sweat glands

Merocrine gland secretes hypotonic filtrate of blood plasma (99% water and salts)

Apocrine sweat glands

Merocrine gland that secretes filtrate of blood plasma with added proteins. Mostly in axillary and anogenital region.

Sebaceous glands

Holocrine gland secretes sebum by rupturing. Located everywhere except palms and soles.

1. Protection

2. Body temperature regulaton

3. cutaneous sensation

4. metabolic function

5. blood resevoir

6. excretion

Six functions of the skin

1. Chemical Barrier

2. Biological barrier

3. Physical Barrier

The skin protects using three barriers:

1. Melanin pigments prevents against UV damage

2. Secretes sebum and sweat that forms chemical barrier. Low pH. Bacteria do not survive. Also bactericidal. Kills bacteria on surface

Describe skin’s chemical barrier in relation to UV rays and bacteria.

1. Dendritic cells

2. Dermal macrophages

Cells that trigger immune response in biological barrier in skin

Dendritic cells

Cells gulf foreign material and transports to lymph node. Immune system in particular

Dermal macrophages

Cells part of immune response. Disposes of virus and bacteria. Why open wounds/ burn victims can easily get infection. Barrier (skin) is removed and barrier does not unction

1.  lipid soluble substances (oxygen, carbon dioxide, fatsoluble vitamins)

2. Oleoresins in plants (oil from plants can diffuse through skin and cause allergic reaction)

3. Organic solvents like acetone, dry-cleaning fluid, paint thinner can dissolve through skin. Don't want large quantities on skin. Harmful to body, can get into blood and kidneys, can cause kidneys to shut down.

4. Salts of heavy metals (lead, mercury). Harmful to body, can get into blood and kidneys, can cause kidneys to shut down.

5. Selected drugs (nitroglycerin, anti-inflammatories like volterin,

 

 

What can penetrate skin barrier? [5]

water

Skin’s strong barrier does not allow ________ to diffuse through it

If external temperature is cooler, heat will move, via convection, from skin to air. If it gets too low: blood vessels constrict and shut down. Less blood flow to skin means less heat escapes. Keeps center of body warm. Reduce passive heat loss. When body temp rises, nervous system dilates blood vessels in dermis and stimulates sweat glands. Sweat evaporates and removes heat from the body.

Body temperature control negative feedback mechanism

Between 36.5-37.5 degrees celsius

Body temperature

Sensory receptors in skin allow us to feel. Sensing hair movement, sensing deep pressure, painful stimuli, temperature.

Cutaneous sensation allows…

1. Sunlight on skin converts modified cholesterol to produce vitamin D.

2. Skin has enzymes (speed up reaction) that suppliment those in liver. Can disarm cancer causing chemicals that get into dermis. Enzymes that can activate steroid hormones

3. Skin makes important proteins.

Three metabolic functions of skin

 hold 5% of blood volume. Control of blood vessel dilation enables blood to be moved to central organs if required.

How much blood in blood reservoir?

Profuse sweating results in loss of water and salts (need to drink fluids when exercising or in hot weather)

Excretion as a function of skin