ANP 1106 Chapter Notes - Chapter 5: Holocrine, Water–Electrolyte Imbalance, Defensin

206 views20 pages

For unlimited access to Textbook Notes, a Class+ subscription is required.

Chapter 5: The Integumentary System
-the skin and its derivatives (sweat, oil glands, hairs, nails etc.) make up the
integumentary system and serves several functions that are mostly protective
The Skin
-also called integument, meaning "covering"
-composed of 2 distinct regions:
1) Epidermis
-composed of epithelial cells
-the outermost protective shield of the body
2) Dermis
-making up the bulk of the skin
-tough, leathery and composed mostly of fibrous connective tissue
-vascularised
-nutrients reach the epidermis by diffusing through the tissue fluid from blood
vessels in the dermis
-hypodermis is the subcutaneous tissue just deep to the skin
-not actually part of the skin
-shares some of the skin's protective functions
-called superficial fascia because it is superficial to the tough connective tissue
wrapping (fascia) of the skeletal muscles and is made up of mostly adipose tissue
-stores fat
-anchors the skin to underlying structures (i.e.: muscles) loosely enough that the
skin can slide relatively freely over those structures
-sliding skins protects us by ensuring that blows just glance off the body
-acts as a shock absorber and an insulator that reduces heat loss from the body
-hypodermis is the first part to thicken when a person gains weight
-accumulates around the thighs and waist in women
-accumulates around the abdomen in men
The Epidermis
-made up of a keratinized stratified squamous epithelium consisting of 4 distinct cell
types and 4-5 distinct layers
Cells of the Epidermis
-epidermal cells include keratinocytes, melanocytes, epidermal dendritic cells, and
tactile cells
1) Keratinocytes
-makes up most epidermal cells
-"keratin cells"
-produce keratin (fibrous protein that helps give the epidermis its protective properties)
Unlock document

This preview shows pages 1-3 of the document.
Unlock all 20 pages and 3 million more documents.

Already have an account? Log in
-connected by desmosomes
-arise from the deepest part of the epidermis from a cell layer called the stratum basale
-these cells undergo continuous mitosis in response to prompting by epidermal
growth factor
-cells are pushed upward by the production of new cells beneath them and the old
cells make the keratin that eventually dominate their cell content
-by the time the keratinocytes reach the free surface of the skin, they are scalelike
structures that consist of keratin-filled plasma membranes
-keratinocytes continuously rub off; a new epidermis forms every 25-45 days
-keratinocyte and keratin formation are accelerated in body areas subject to continuous
friction (i.e.: palms and soles of feet)
-persistent friction causes a thickening of the epidermis called a callus
2) Melanocytes
-spider shaped epithelial cells
-synthesize the pigment melanin (melan = black)
-found in the deepest layer of the epidermis
-as melanin is made, it accumulates in membrane-bound granules called melanosomes
which are moved along actin filaments by motor proteins to the ends of the melanocyte's
process
-they are then taken up by nearby keratinocytes
-melanin granules accumulate on the superficial (upper portion that receives the
most sunlight) side of the keratinocyte nucleus and forms a pigment shield that
protects the nucleus from UV radiation
-epidermal dendritic cells (Langerhans cells) arise from bone marrow and migrate to
the epidermis
-they ingest foreign substances and are key activators of our immune system
-tactile (Merkel) cells are present at the epidermal-dermal junction
-each tactile cell is associated with a disc-like sensory nerve ending called a
tactile or Merkel disc which functions as a receptor for touch
Unlock document

This preview shows pages 1-3 of the document.
Unlock all 20 pages and 3 million more documents.

Already have an account? Log in
Layers of the Epidermis
-thick skin covers the palms, fingertips, and soles of the feet and the epidermis consists
of 5 layers or strata
-from deep to superficial, these layers are stratum basale, stratum spinosum,
stratum granulosum, stratum lucidum, and stratum corneum
-thin skin covers the rest of the body and the stratum lucidum appears to be absent and
the other strata are thinner
*ordered from deep to superficial*
1) Stratum Basale (Basal Layer)
-the deepest epidermal layer
-attached to the underlying dermis along a wavy borderline that looks like corrugated
cardboard
-consists of a single row of stem cells that represent the youngest keratinocytes
-numerous mitotic nuclei can be found in this layer and reflect the rapid division of the
cells
-also known as stratum germinativum
-each time a basal cell divides, one daughter cell is pushed into the cell layer above and
begins to specialize into a mature keratinocyte
Unlock document

This preview shows pages 1-3 of the document.
Unlock all 20 pages and 3 million more documents.

Already have an account? Log in

Get access

Grade+
$10 USD/m
Billed $120 USD annually
Homework Help
Class Notes
Textbook Notes
40 Verified Answers
Study Guides
1 Booster Class
Class+
$8 USD/m
Billed $96 USD annually
Homework Help
Class Notes
Textbook Notes
30 Verified Answers
Study Guides
1 Booster Class