Always a part of you

Most living things are made up of one or more cells. These are more cells from our bodies and from plants.

Skin Skin is the body's largest organ (yes, it's an organ!). If the skin of a 150-pound person were spread out flat, it would cover approximately 20 square feet. The skin is made up of two main layers, the dermis, an inner, living layer, and the epidermis, an outer layer of dead cells. The epidermis is several cells thick and is composed of a stratified squamus epithelium of keratinized cells. What does THAT mean? An epithelium is a layer of cells that serves as a protective covering over some surface. Squamus means that they are flattened. Stratified means that it is layered. Keratin is a fibrous protein that makes the cells stiff and horny. Your hair and fingernails are made up of keratin. This is what makes the epidermis act as a protective layer (BROWN). The GREEN part is known as the prickle layer. These epidermal cells are constantly being shed (and provide food for dust mites!) and are replaced from below by a basal layer of columnar (column-shaped) cells (BLUE with PURPLE) The epidermal layer of your skin is totally replaced every 52 to 75 days. The dermis is made up of collagen and elastic fibers, permeated by hair follicles, nerves, blood vessels, nerves, fat globules, and sweat glands. (ORANGE). The average square inch ( 6.5 sq. cm) of skin holds 650 sweat glands, 20 blood vessels and 60,000 melanocytes (pigment cells). The skin is also a huge sensory receptor for heat, cold, pain, touch, and tickle. Are you ticklish?

 

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Lung		Skin 1		Skin 2		Skin 3		Cell Surface
Red Blood Cells		Red Blood		Red Blood Cell		Macrophage		Sperm
Muscle TEM		Golgi		Mitochondria		Synapse
Cell - TEM		Cell - TEM		Stomata		Stomata 2