Pair up & answer: What is the largest organ in the body Pair up & answer: What is the largest organ in the body? (Hint: It’s also the most superficial organ…) The SKIN

What is the name of the organ system that contains the skin? The INTEGUMENTARY SYSTEM

The Integumentary System And Body Membranes

Skin Integument - another name for skin Principal organ of integumentary system Sheetlike structure called membrane Great system to study to understand how structure is related to function!

Pair up and answer: Discuss one biological example of how structure is related to function.

Classification of Body Membranes Membranes cover and protect the body surface, line body cavities, & cover inner surfaces of hollow organs Two major categories Epithelial - composed of epithelial tissue and an underlying layer of specialized connective tissue Connective - various types of connective tissue , no epithelial cells

Epithelial Membranes lumen Cutaneous - skin, one of largest organs, composes 16% of body weight Serous - found in closed cavities Mucous - lines body surfaces opening directly to exterior GOBLET CELLS (in pic) secrete mucous to line the tracheal airway (on cilia surface).

Connective Tissue Membranes Unlike other types of membranes, do not contain epithelial components. Ex: Synovial membranes lining spaces b/t joints (knee) The normal knee joint is surrounded by a membrane (the synovium-- superficial to the cartilage) which produces a small amount of thick fluid (synovial fluid). The synovial fluid helps to nourish the cartilage and keep it slippery. The synovium also has a tough outer layer (the joint capsule) which protects and supports the joint. Rheumatoid arthritis (autoimmune) is caused by immune system attacking synovium, leading to joint inflammation.

Structure of the Skin Composed of following layers: Epidermis - outermost, thin sheet of stratified squamous epithelium Dermis - deeper, thicker layer made up largely of connective tissue. Connective tissue layer - subcutaneous or hypodermis.

Parts of Skin (click)

Epidermis Epithelial cells are tightly packed into many layers. Innermost - stratum germinativum - undergoes mitosis and moves toward surface. This allows skin to repair itself! As cells are made and move up to the surface the cytoplasm is replaced by protein keratin. Keratin is tough and waterproof. Millions of cells with keratin flake off all day.

They wash off and go down the drain. Pair and answer: When you wash your hands, what happens to your most superficial skin cells? They wash off and go down the drain.

because skin cells are quickly and constantly dividing After years and years of washing, how come you don’t eventually wash down to your muscles and bones? because skin cells are quickly and constantly dividing (though at a lower rate when you get elderly-- that’s why they heal more slowly)

Epidermis continued… Deepest cell layer produces pigment, melanin, by melanocytes. Heredity (genes) determines how dark or light your skin is, to an extent. What else determines degree of color? Prolonged exposure to sun increases melanin deposits.

Dermis Have tough or stretchable fibers in between Dermis is the deeper layer Thicker than epidermis Composed largely of connective tissue. Cells are scattered apart vs. close together. Have tough or stretchable fibers in between Upward projections, dermal papillae, form ridges and grooves that make fingerprints and bind two layers together.

Fingerprints Dermal papillae patterns are unique to each person and determine fingerprints, palm patterns, and toeprints. Compare your palm patterns to your neighbor

Appendages of the Skin Hair Nails Glands

Because your nail bed (just deep to the nail body) contains lots of blood vessels, it appears red (or blue when blood oxygen levels drop).

Sebaceous Glands Secrete oil for the hair and skin But why??? “nature’s skin cream” What type of gland is this? Multicellular exocrine

Skin Receptors: http://www. sumanasinc

SKIN FUNCTIONS Before we proceed to skin disorders, let’s clarify… What are three main functions of the skin? Protection Temperature Regulation Sensation (detection of pain, etc.)

Blisters of the epidermis Cells of epidermis are tightly packed together. If weakened, blisters can form. Epidermis and dermis layers are “glued” together. If damaged or destroyed blisters will also form.