Download - Integumentary SystemIntegumentary System Chapter 6 Sections 1 & 2Chapter 6 Sections 1 & 2
Integumentary SystemChapter 6 Sections 1 & 2
Objectives• Describe what constitutes an organ, and name the large organ of the integumentary system• Discuss the functions of the skin• Describe the structure of the layers of the skin• Summarize the factors that determine skin color
Introduction• Review: two or more tissues grouped together to perform
specialized functions constitutes an organ• The skin is the largest organ in the body by weight• The skin and its accessory structures together make up the integumentary system• Skin is composed of several types of tissues such as,
stratified squamous epithelium, dense irregular connective, and adipose tissues (see figure 6.1 p.180)• It is a versatile organ of the body and vital in maintaining
homeostasis
Characteristics & Functions of the Skin• It prevents harmful substances and microorganism from
entering the body• It lessens water loss by diffusion from deeper tissues• It regulates body temperature• It houses sensory receptors• Contains epidermal dendritic cells or Langerhans cells
which initiated the immune response to phagocytize harmful microorganisms
• It excretes small amounts of waste• Some skin cells produce the vitamin D precursor, which when
exposed to sunlight changes to an inactive form of vitamin D.
Skin & its Tissues• The skin, also known as the cutaneous membrane, has
two distinct layers:• The epidermis• The dermis
The Epidermis• The outer layer of the skin• It’s a thin layer, averaging 0.07-0.12 mm thick• Composed of stratified squamous epithelium• It lacks blood vessels• Can have five distinct layers• Stratum corneum• Stratum lucidum• Stratum granulosum• Stratum spinosum• Stratum basale
The Epidermis Overall
Stratum corneum• Is the outermost layer• Consists of many layers of keratinized, dead epithelial
cells that are flattened and non-nucleated• Keratinization is the process of older skin cells, called
keratinocytes, thickening and developing many desmosomes while hardening at the same time• Keratin is a tough, fibrous, waterproof protein that is
stored in those cells
Stratum lucidum• Found between the stratum corneum and stratum
granulosum on the soles of your feet and the palms of your hands• Cells appear clear• Nuclei, organelles and cell membranes are no longer
visible• This layer is missing where the skin is thinner
Stratum granulosum• Found beneath the stratum corneum• Consists of 3-5 layers of flattened cells that contain
shrunken fibers of keratin and shriveled nuclei
Stratum spinosum• Lies beneath the stratum granulosum• Composed of many layers of cells with centrally located,
large, oval nuclei, and developing fibers of keratin• Cells become flattened as new layers develop
Stratum Basale• The deepest layer of the epidermis• Consists of a single row of cuboidal or columnar cells • Can grow and divide because the cells receive nutrients
from the nearby dermis layer• Also contains melanocytes
The Epidermis Overall
Melanocytes• Are specialized cells that produce the dark pigment melanin
from the amino acid tyrosine in organelles called melanosomes• Melanin provides skin color and absorbs UV radiation in
sunlight• They lie in the stratum basale of the epidermis• The number of melanocytes is the same for all human
regardless of racial origins• It is the amount of melanin produced that determines how
dark your skin is, as well as, genetic factors and environmental factors
The Dermis• The boundary between the dermis and the epidermis is
uneven• Two distinct layers:• Dermal papilla• Dermis
Dermal papilla (Papillary Layer)• Are cone-shaped and extend from the dermis layer into
the uneven ridges of the epidermis• Composed of areolar connective tissue• They increase the surface area where epidermal cells
receive oxygen and nutrients from the capillaries• They are found all over in the skin of the body, but are
most abundant in the hands and feet• They form friction ridges that leave a patterned
impression better known as a fingerprint
Dermis layer (Reticular Layer)• Composed of dense irregular connective tissue with a
tough collagenous fibers and elastic fibers embedded in a gel-like ground substance• The network of these fibers, give skin its toughness and
elasticity• The dermis on average is 1.0-2.0 mm thick• On the eyelids it is 0.5 mm• On the soles of the feet it is 3.0 mm• Also contains: muscle fibers, accessory structures, nerve
cell processes, and sensory receptors
The Dermis