Download Module 21 / Gross Anatomy of the Integumentary System

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Anatomy & Physiology (Open + Free)
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Unit 6:: Integumentary System
Introduction
Module 21 /
Integum entary Structures
and Functions
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Integum entary Lev els of
Organization
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Gross Anatomy of the Integumentary System
Describe the m ain function of
each lay er of the
integum entary sy stem .
The skin is made up of two mutually dependent layers that are distinguished based on their structure and
location. These layers – the epidermis and the dermis – contain a variety of structures, including blood
vessels, hair follicles, and sweat glands. Beneath the dermis lies the hypodermis (subcutis). It is composed
mainly of fatty tissue.
The most superficial layer, the epidermis, is composed of stratified squamous epithelia that are keratinized
at the outermost surface, melanocytes, immune cells (Langerhans that modulate immune response) and
sensory receptors (Merkel cells that detect light touch). The function of the epidermis layer is "protection."
The keratinocytes and immune cells help protect the skin.
The dermis lies beneath the epidermis and is composed of two layers of connective tissue: a loose layer
(papillary) and a dense irregular layer (reticular). Both layers of the dermis contain connective tissue
components (collagen, elastin, fibroblasts), plus blood vessels, sensory receptors and lymphatics. The dermis
is a "functional" layer. The dermis is connective tissue that can stretch and retract because of the strong and
elastic extracellular matrix. The dermis also contains nerves.
Beneath these two layers lies the hypodermis, composed of loose connective tissue (adipose and areolar). The
hypodermis is the "connection" layer. It connects the integument (epidermis and dermis) to organs and
muscles in the body. This layer contains adipose tissue and connective tissue as well as blood vessels, nerves
and immune cells.
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