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5 million ec

Skin Blood Vessels

An organ, such as the skin, is composed of several kinds of tissues (30x).

Subcutaneous layer —

Subcutaneous layer —

Nerve Cell Dermis

Hair shaft Sweat gland pore

Sweat gland

Nerve cell process

Adipose cells

Blood vessels

Hair shaft Sweat gland pore

Dermal papilla Basement membrane Touch receptor Sweat gland duct Sebaceous gland Arrector pili muscle Hair follicle

Sweat gland

Nerve cell process

Adipose cells

Blood vessels

Figure 6.2

A section of skin.

The skin includes two distinct tissue layers. The outer layer, called the epidermis (ep iwder mis), is composed of stratified squamous epithelium. The inner layer, or dermis (dermis), is thicker than the epidermis, and it is made up of connective tissue containing collagen and elastic fibers, epithelial tissue, smooth muscle tissue, nervous tissue, and blood. A basement membrane that is anchored to the dermis by short fibrils separates the two skin layers.

Beneath the dermis, masses of loose connective and adipose tissues bind the skin to underlying organs. These tissues are not part of the skin. They form the subcutaneous layer (sub ku-ta ne-us la evr), or hypodermis (fig. 6.2).

D Name the three types of epithelial membranes, and explain how they differ.

List the general functions of the skin.

Name the tissue in the outer layer of the skin. Name the tissues in the inner layer of the skin.

A group of inherited conditions collectively called epidermolysis bullosa (EB) destroy the vital integrity of the skin's layered organization. Symptoms include very easy blistering and scarring. Different types of EB reflect the specific proteins affected. In EB simplex, blisters form only on the hands and feet and usually only during warm weather. EB simplex is an abnormality in the protein keratin in epidermal cells. In the severe dystrophic form, collagen fibers that anchor the dermis to the epidermis are abnormal, causing the layers to separate, forming many blisters. The basement membrane form of EB is so severe that it causes death in infancy. It is a defect in epiligrin, a protein that anchors the epidermis to the basement membrane.

Stratum Basale

Stratum lucidum —Stratum granulosum

—Stratum spinosum Stratum basale

(a) The layers of the epidermis are distinguished by changes in cells as they are pushed toward the surface of the skin.

(b) Micrograph from the palm of the hand (50x).

Stratum corneum

Stratum lucidum Stratum granulosum

Stratum spinosum

Stratum basale Basement membrane

Dermis

Stratum lucidum —Stratum granulosum

—Stratum spinosum Stratum basale

Figure 6.3

Essentials of Human Physiology

Essentials of Human Physiology

This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.

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