PHYSIOLOGY INTRO:The Integumentary System

Honors BiologyUnit 8 – Powerpoint #1Chapter 35 /36

Warm Up: Anticipation Guide• Complete questions #1-10 by circling agree, disagree.

What is Physiology?• Physiology is the study of the functions of living organisms

and their parts

What is Homeostasis• The ability to maintain a constant internal environment

Eleven Organ Systems

For example the Skeletal System which includes your bones, cartilage, ligaments and tendons.

Try to think of as many organ systems as you can. Write them on the lines provided.

The Eleven Organ Systems

•Skeletal •Muscular •Circulatory•Respiratory•Digestive •Nervous

•Reproductive •Excretory•Lymphatic/Immune •Endocrine• Integumentary

Today: Integumentary System•Structures: skin, hair, nails, sweat glands and oil glands.

•Functions:• Barrier against infection and injury (including UV protection)

• Helps regulate body temperature• Prevents H2O loss• Waste excretion• Vitamin D synthesis

The Largest Organ

•Skin is 12-15% of body weight•15-20 sq. ft ( 1.5-2.0 sq. meters)

•Some organisms, such as insects, and some amphibians, use the integumentary system for respiration

2 Layers

•The skin is made of 2 main layers

1) Epidermis2) DermisBelow the dermis is subcutaneous fat (known as adipose tissue)

Skin: The Layers

Epidermis: First layerStructureTop is made of squamous epithelium cells:

• Top layer is filled with keratin. Keratin is a fibrous, waterproof protein.

• Top 20-30 cells are flattened and dead, cells below are pushing upward, and not fully keratinized.

• Cells at the bottom of of the epidermis undergo mitosis

• Top cells are replaced every 30-45 days

Epidermis

Epidermis: First layerFunction

1) Water resistance2) Protection against biological/ chemical assault3) Contains MELANOCYTES

• Produce pigment MELANIN4) Contains Merkel cells – attached to nerves and detect touch5) Contains Langerhans cells – these cells guard against toxins, microbes and other pathogens that penetrate the skin. If detected, alert the immune system

Skin: DermisFound beneath the Epidermis

Dermis: Second layerStructure

Made of strong, flexible connective tissueContains:

CollagenNervesBlood vesselsLymph vesselsHair folliclesSweat glandsMuscles (attached to hair follicles)

Function1) Contains Sweat glands (3000/ in2) these: -Release sweat to maintain homeostasis-Release various wastes collected by the bloodstream-Mammary glands and ear wax glands are modified sweat glands2) Contains Sebaceous (oil) glands (2 per hair)These glands release SEBUM keeping the epidermis and hair flexible and waterproof3) Contains many sensory cells 4) Site of hair follicles5) Gives skin its elasticity and strength

Dermis: Second layer

Skin color• Skin color is due mainly to the pigment MELANIN

• Melanin may be a yellow, rust, brown or black pigment• Darker skin is due to kind and amount of melanin (everyone

has same amount of melanocytes) • Amount of melanin can vary with exposure to sunlight

Skin Markings:Freckles: Flat, melanized patches. Varies with heredity or sun exposure

Moles: Elevated patches of melanized skin, with hair

Hair • Made of Keratin• Hair covers almost every exposed surface. • Hair growth is determined by hormones• You are born with as many hair follicles as you will ever have• Hair is used for protection. From the sun, or dirt• Hair color

• Depends on kind (yellow, rust, brown, black) and amount of melanin

• Hair Texture • Related to difference in shape of hair• Straight = round, Wavy = oval, Tightly curly = flat

Hair differences• Scanning electron

micrograph of a hair fiber from a Caucasian blonde female (above) and an Asian male (below). The overlapping cells of the cuticle are readily apparent on both fibers.

Nails

• Scale-like modification of the epidermis• Made of thin, dead, scaly cells, packed together• Protect the ends of the fingers and toes• Produced by the nail root: an area of rapid mitosis• Fingernails grow 1mm/week, toenails slower

Disorders• Allergies: poison ivy• Viral infection: herpes simplex• Fungal infection: athletes foot• Bacterial infection: inflammation of hair follicle/sebaceous

glands

• Genetic disorders• Psoriasis: Dry and scaly skin. Skin cell production is 2X-3X normal

• Hypertrichosis: Dense hair growth on face and upper body.

Disorders• Skin Cancer• Basal Cell Carcinoma

• Most Common – 99% fully cured• Inability to form keratin• Strikes between epidermis and dermis

• Squamous Cell Carcinoma• Lower layer of epidermis• Induced by the sun

• Malignant Melanoma• Cancer of pigment cells = melanocytes• Rare – 1% of skin cancers• Poor chance of cure• Often begins with moles

What not to do:

Burns

• 1st Degree• Inflamed, red skin – surface of epidermis is shed

• 2nd Degree• Blisters form as fluid builds beneath epidermis

• 3rd Degree• Epidermis & Dermis is destroyed• Catastrophic loss of fluids• Highly susceptible to infection

Aging• Hair• Thin and gray as melanocytes die, and mitosis slows

• Oil Glands• Sebaceous glands atrophy (shrink) = Skin and hair become drier

• Skin Layers• Mitosis slows, Collagen lost from dermis = Skin becomes thin

and translucent, • Loose and sagging as elastic fibers are lost in dermis• Fewer blood vessels = More bruising, slower healing• Age Spots – accumulation of pigment cells

Fun Facts• You loose about 8-10 pounds of skin/year

• Globally, dead skin accounts for about a billion tons of dust in the atmosphere. Your skin sheds 50,000 cells every minute.

• http://visual.ly/50-incredible-facts-about-skin