Skeletal Review + Integumentary and Circulatory Systems

Types of Bones Bones are classified according to function: Long – used for large movement; ie: femur Short – for small movement; ie: carpals and tarsals Flat – thin bones usually protect organs; ie: cranium, scapulae, ribs Irregular – used for special functions; ie: vertebrae Sesamoid – usually embedded in tendons, used to protect the integrity of tendons; ie: patella

The Integumentary System The integument is an organ, and is an alternative name for skin. The integument is the body’s largest organ and accounts for 15% of body weight. Derivatives of the integument: Hair Nails Skin Glands

We will focus on the skin… Which is made up of two layers, the epidermis and the dermis, plus a layer below the dermis called the hypodermis or the subcutaneous layer. Can you guess what this bottom layer is made of?

Layers of the Epidermis The epidermis is made mostly of keratinocytes (95%), which provides a barrier against environmental damage such as______________________________________________. Stratum corneum: the outermost layer, made of 10-30 layers of dead flat keratinocytes. These cells are water repellant and are continuously shed & replaced. Stratum lucidum: Only found in the fingertips, palms of hands, & soles of feet. This layer is made up of 3-5 layers of flat dead keratinocytes. Stratum granulosum: made up of 3-5 layers of keratinocytes, where the keratinocytes start to lose their nuclei. Stratum spinosum: appears covered in thornlike spikes, provide strength & flexibility to the skin. Stratum basale: The deepest layer, made up of a single layer of epithelial cells. Cells produced here are constantly dividing & move up to the apical surface. Basement membrane: primary function to anchor epidermis to the dermis.

The Dermis is the deeper, thicker layer composed of connective tissue, blood vessels, nerves, glands and hair follicles. There are two main divisions of the dermal layer: Papillary region - The papillae are the finger-like projections that extend toward the epidermis, which strengthens the connection between the two layers. Reticular Region - Made of protein fibers which give the dermis its properties of strength, extensibility, and elasticity. Contains roots of hairs, sweat glands, oil glands, sensory receptors, nails, and blood vessels.

The Hypodermis The hypodermis is NOT part of the skin It contains 50% of body fat, which serves as padding and insulation Its purpose: to attach the skin to the underlying bone and muscle tissues To supply bone and muscle with nerves and blood vessels