• The integument (or skin) is a composite organ.
• On the surface, is the epidermis, below it is the dermis, and between them
lies the basement membrane (basal lamina and reticular lamina).
• The epidermis is derived from the ectoderm and produces the basal lamina.
The dermis develops from the mesoderm and mesenchyme and produce sthe
• Between the integument and the deep body musculature is a transitional
subcutaneous region made up of loss connective and adipose tissues.
• In microscopic examination, this region is termed the hypodermis.
• In gross anatomical dissection, the hypodermis is referred to as the
• Makes up 15% of the human body weight, the epidermis produces hair,
feathers, baleen, claws, nails, horns, beaks, and some types of scales.
• The dermis gives rise to dermal bones and osteoderms of reptiles.
• Collectively, epidermis and dermis form teeth, denticles, and scales of fish. In
fact the absence of one, the other by itself is incapable of or inhibited from
producing these structures.
• As the critical border between the organism and its exterior environment, the
o Forms part of the exoskeleton and thickens to resist mechanical injury.
o Prevents the entrance of pathogens.
o Helps hold the shape of an organism.
o Osmotic regulation and movement of gases and ions to and fom the
o Gathers needed heat, or radiates the excess, and house sensory
o Holds feathers for locomotion, hair for insulation, and horns for
o Block UV light and display bright colors during courtship.
Embryonic Origin and Development of Skin:
• By the end of neurulation in the embryo, most skin precursors are delineated.
The single-layered surface ectoderm proliferates to give rise to the
• The deep layer of the epidermis, the strautum basale (Strautum
germinativum), rests upon the basement membrane. Through active cell
division, the stratum germinativum replenishes the single layer of outer cells
called the periderm.
• The dermis arises from several sources,principally from the dermatome. The
segmental epimeres (somites) divide, producing the sclerotome medially, the
embryonic source of the vertebrae, and the dermomyotome layerally. Inner
cell of the dermomyotome become rearranged into the myotome, the major
source of skeletal muscle. The outer wall of the dermomyotome spreads out