BSC 215 Lecture Notes - Lecture 10: Ultraviolet, Invasive Species, Thermoregulation
8 Jun 2018
School
Department
Course
Professor
The Dermis
The second layer of the skin, the dermis, consists of various connective tissues. As connective
tissue, it contains fibroblasts and macrophages within a gelatinous matrix containing collagen,
elastic, and reticular fibers. The structure provides strength, extensibility (the ability to be
stretched), and elasticity (the ability to return to its original form). It is in the dermis where we
find capillaries and many nerve endings. Major blood vessels are found in the hypodermis.
The dermis consists of two layers:
• The papillary layer is a thin outer layer of areolar connective tissue with
fingerlike projections called dermal papillae that protrude into the
epidermis. In the hands and feet, the dermal papillae generate
epidermal ridges (sweat from the epidermal ridges leaves
fingerprints).
• The reticular layer is a thick layer of dense irregular connective tissue. It
lies deep to the papillary layer and makes up most of the dermis.
The Hypodermis
The hypodermis (subcutaneous layer, or superficial fascia) lies between the dermis and
underlying tissues and organs. It consists of mostly adipose tissue and is the storage site of
most body fat. It serves to fasten the skin to the underlying surface, provides thermal
insulation, and absorbs shocks from impacts to the skin.
The Skin and Its Functions
The skin is far more than just the outer covering of human beings; it is an organ just like the
heart, lung, or liver. Besides providing a layer of protection from pathogens, physical abrasions,
and radiation from the sun, the skin serves many functions. It plays a vital role in homeostasis by
maintaining a constant body temperature via the act of sweating or shivering and by making you
aware of external stimuli through information perceived within the touch receptors located
within the integumentary system. It only takes one visit to a burn unit to see the value of skin and
the many complications that arise when this organ is compromised.
The skin, or integument, is considered an organ because it consists of all
four tissue types. The skin also consists of accessory organs, such as glands,
hair, and nails, thus making up the integumentary system. A section of skin
with various accessory organs is shown in Figure 1.
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
The second layer of the skin, the dermis, consists of various connective tissues. As connective tissue, it contains fibroblasts and macrophages within a gelatinous matrix containing collagen, elastic, and reticular fibers. The structure provides strength, extensibility (the ability to be stretched), and elasticity (the ability to return to its original form). It is in the dermis where we find capillaries and many nerve endings. Major blood vessels are found in the hypodermis. The dermis consists of two layers: the papillary layer is a thin outer layer of areolar connective tissue with fingerlike projections called dermal papillae that protrude into the epidermis. In the hands and feet, the dermal papillae generate epidermal ridges (sweat from the epidermal ridges leaves fingerprints): the reticular layer is a thick layer of dense irregular connective tissue. It lies deep to the papillary layer and makes up most of the dermis.
