Chapter 12: Skin system (C2429509)


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Section 1: Skin system

Skin is the soft outer covering of animals. It can be subdivided into the:

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* Epidermis, the outermost layer of skin, that forms a protective barrier over the body's surface, responsible for keeping water in the body, preventing pathogens from entering. 95% of the epidermis is made up of keratinocyte (i.e. predominant cell type of the epidermis), which as skin moves up, becomes highly organized, including keratin (i.e. fibrous structural protein [i.e. one of 3 main classes of proteins, the others being globular and conjugated proteins]), which give mechanical strength to skin. The epidermis contains no blood vessels

* Basement membrane, which is a thin sheet separating the epidermis (before) and dermis (next)

* Dermis, which is the layer beneath the epidermis (supra), consisting of connective tissue (i.e. one of 3 types of tissues, the others being epithelial, muscle and nervous), which cushions the body from stress and strain. It provides tensile strength (i.e. withstand stress without failure) and elasticity (i.e. property where materials return to their original shape after stress) to skin. It harbors many mechanoreceptors (i.e. sensory receptor for mechanical pressure), that provide sense of touch and heat. It also contains hair follicles (i.e. skin organ that produces hair), sweat glands (i.e. tubular structures of skin that produce sweat), lymphatic vessels (i.e. valved structures that carry lymph) and blood vessels

* Hypodermis (aka subcutaneous tissue [from Latin "cutis" meaning "skin", so under the skin]), which isn't apart of skin, but does lie below the dermis (supra). It attaches skin to the underlying bone and muscle, and supplies it with blood vessels and nerves (i.e. band of nervous tissue [i.e. 1 of the 4 types of tissue], that connects the peripheral nervous system [i.e. the nervous system outside the brain and spinal cord] with its organs)

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Chapter 12: Skin system - Biology - Pre-med science - MR. SHUM'S CLASSROOM