PHYSIOLOGY : The Integumentary System Biology Unit 8 – Powerpoint #1 Chapter 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 Helps regulate body temperature Provides protection from UV light from the sun Waste excretion Vitamin D synthesis

The Largest Organ Skin is 12-15% of body weight sq. ft ( 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) Epidermis 2) Dermis Below the dermis is subcutaneous fat (known as adipose tissue)

Skin: The Layers

Epidermis: First layer Structure Top is made of squamous epithelium cells: Top layer is filled with keratin. Keratin is a fibrous, waterproof protein. Top cells are flattened and dead, cells below are pushing upward, and not fully keratinized. Cells at the bottom of the epidermis undergo mitosis Top cells are replaced every days

Epidermis: First layer Function 1) Water resistance 2) Protection against biological/ chemical assault 3) Contains MELANOCYTES Produce pigment MELANIN 4) Contains Merkel cells – attached to nerves and detect touch 5) Contains Langerhans cells – these cells guard against toxins, microbes and other pathogens that penetrate the skin. If detected, alert the immune system

Skin: Dermis Found beneath the Epidermis

Dermis: Second layer Structure Made of strong, flexible connective tissue Contains: Collagen Nerves Blood vessels Lymph vessels Hair follicles Sweat glands Muscles (attached to hair follicles)

Function 1) Contains Sweat glands (3000 in 2 ) these: - Release sweat to maintain homeostasis -Release various wastes collected by the bloodstream -Mammary glands and ear wax glands are modified sweat glands 2) Contains Sebaceous (oil) glands (2 per hair) These glands release SEBUM keeping the epidermis and hair flexible and waterproof 3) Contains many sensory cells 4) Site of hair follicles 5) 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 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

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

Burns 1 st Degree Inflamed, red skin – surface of epidermis is shed 2 nd Degree Blisters form as fluid builds beneath epidermis 3 rd 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