Transcript Skin and the Integumentary System

Skin and the Integumentary
System
Chapter 6
Introduction
• An organ is two or more tissues grouped
together and performing specialized
functions
• The cutaneous membrane (skin) together
with certain accessory organs make up the
integumentary system
Integumentary system
http://methiscool.files.wordpress.com/2012/04/cross-section.png
Types of Membranes
• Serous membranes – line body cavities
that lack openings to the outside
– Form inner linings of thorax and abdomen
(visceral and parietal)
– Cover the organs within these cavities
• Secretes watery serous fluid, which
lubricates membrane surfaces
Serous membranes
http://www.daviddarling.info/images/serous_membranes.jpg
• Mucous membranes – line cavities and
tubes that open to the outside of the body
– Include oral, nasal, and tubes of the digestive,
respiratory, urinary, and reproductive systems
– Secrete mucous from goblet cells
http://classconnection.s3.amazonaws.com/998/flashcards/60998/jpg/membranes_-_mucous21341005104874.jpg
• Synovial membranes – form the inner
linings of the joint cavities between the
ends of bones at freely movable joints
(synovial joints)
– Secrete a synovial fluid which lubricates the
ends of bones within the joint
http://upload.wikimedia.org/wikipedia/commons/thumb/f/fc/Illu_synovial_joint.jpg/250px-Illu_synovial_joint.jpg
• Cutaneous membrane - skin
http://www.edzone.net/~fulton/high/winkler/team3/The%20Integumentary%20System_files/image003.jpg
Skin and its tissues
• What it does:
– Maintains homeostasis
– Protective covering
– Regulates body temp
– Prevents water loss from deeper tissues
– Houses sensory receptors
– Creates biochemicals
– Excretes small quantities of wastes
• Has two distinct tissue layers:
• Epidermis – outer layers
– Made of stratified squamous epithelium
• Dermis – inner layer
– Thicker than the epidermis and contains all
other types of tissue
• Beneath that is the subcutaneous layer
which contains loose connective tissue
and adipose tissue that connects it to
organs
http://www.wildmedcenter.com/uploads/5/9/8/2/5982510/7422370_orig.png
Epidermis
• Made of stratified squamous epithelium and
lacks blood vessels
• As the cells of the lower layer (stratum basale)
divide they get pushed upward towards the
surface and divide
• These cells harden by the protein keratin filling
into the cell membrane – Keratinization
• This forms the outermost layer (stratum
corneum)
• The loss of skin cells is equal to the death
in healthy skin
• Rate of cell division increases in skin that
is rubbed or pressed a lot (causes calluses
or corns-keratinized masses on toes)
• Functions: shields excessive water loss,
mechanical injury and harmful chemicals,
also keeps out disease-causing organisms
when not cut
http://t0.gstatic.com/images?q=tbn:ANd9GcTXpxGXOQ_Eik8z40jw9QrRzL6qeic2FdGWma8APEJ2Fahuz_Un
Skin color
• Melanocytes are specialized cells in the
epidermis which produce melanin, a dark
pigment that provides skin color
• They also absorb UV radiation in sunlight
which prevents mutations and damaging
effects
• Located in deepest layer of epidermis
http://www.mayoclinic.com/images/image_popup/sn7_skinlayers.jpg
• All people have the same # of
melanocytes but the amount of melanin
that they produce varies
• Mostly genetically determined…more
melanin produced, darker the skin
• Sun causes additional pigment to be
produced
sciencedaily.com
Dermis (fun fact)
• The dermal papillae is uneven which
causes fingerprints
• This is due to genes and when the fetus
presses against the uterine wall
skincarebylouisa.com
Dermis
• Binds the epidermis to underlying tissues
• Made of dense connective tissue with
collagenous and elastic fibers which gives
skin toughness and elasticity
• Filled with blood vessels which supply
nutrients and also regulate body
temperature
• Also has nerve cells throughout which
send impulses to sensory receptors (like
touch)
• It also contains hair follicles, sebaceous
glands (oil producing), and sweat glands
http://www.wildmedcenter.com/uploads/5/9/8/2/5982510/7422370_orig.png
Subcutaneous layer
• Beneath dermis and consists of loose
connective and adipose tissue
• No sharp boundary separates these two layers
• Adipose helps insulate the body
• This layer also contains the major blood vessels
that supply the skin and underlying adipose
tissue
health.rush.edu
Accessory organs of the skin: Hair
Follicles
• Hair is present except on the palms, soles,
lips, nipples, and parts of reproductive
organs
• Hair follicle – tubelike depression in the
skin in which hair develops
• Hair is composed of dead epithelial cells
that develop in the dermis and get pushed
toward surface and keratinized
http://www.wildmedcenter.com/uploads/5/9/8/2/5982510/7422370_orig.png
• A bundle of smooth muscle cells (arrector
pili muscle) attaches to each hair follicle
and contracts which makes hair stand up
(goose bumps)
http://www.ivy-rose.co.uk/HumanBody-Images/Structure_of_Skin/Arrector-Pili-Muscle.jpg
Sebaceous gland
• Contain groups of specialized epithelial cells that secrete
an oily mixture through ducts in hair follicle
• Sebum is the mixture and it helps keep the hair and skin
soft, pliable, and waterproof
http://www.umm.edu/graphics/images/en/19666.jpg
Nails
• Protective coverings on the ends of the
fingers and toes made of keratinized
epithelial cells
• Made of a nail plate and overlies a nail
bed
• The lunula makes up the base of the nail
plate and that is where the nail grows
http://www.handresearch.com/finger-nails/Menu_bestanden/nail-unit.jpg
Sweat glands
• Exocrine glands made of a tube that starts in the
subcutaneous layer and is lines with sweatsecreting epithelial cells
• Two types:
– Eccrine glands-respond to body temp, common in
areas of lots of sweat (forehead)
• Carried by a duct out a pore in the skin
– Apocrine glands-active when a person is emotionally
upset, frightened, or in pain
• (ear wax and mammary glands are modified
sweat glands)
http://topnews.in/healthcare/sites/default/files/Sweat_Glands.gif
Regulation of body Temperature
• If too hot:
– hypothalamus has muscles in the blood vessels relax and
dilate (vasodilatation) which causes heat to leave blood
through skin
– Eccrine glands release sweat (evaporation cools skin)
• If too cold:
– Muscles next to blood vessels contract which causes
(vasoconstriction) and less heat loss
– Sweat glands are inactive
– If keeps getting worse, skeletal muscles are forced to
contract which increases cellular respiration and produces
heat (shivering)
http://faculty.southwest.tn.edu/rburkett/integu27.jpg
Healing of Wounds
• Inflammation – when a wound an the area
surrounding it become red and painfully swollen
in response to injury or stress
• Inflamed skin may become reddened, warm,
swollen, and painful
• Blood vessels dilate which allows more blood to
flow to that area with helpful nutrients and
oxygen
http://www.clinchem.org/content/54/1/24/F3.large.jpg
• If break in skin is shallow:
– Epithelial cells are stimulated to divide and
new cells fill the gap
• If injury extends into the dermis or deeper:
– 1.Blood vessels break and blood clots (forms
scab)
– 2.Fibroblasts come and form new collagenous
fibers that bind wound together
– 3.Blood vessels come back and phagocytic
cells remove dead cells and other debris
– 4.Scab falls off and if wound is bad it forms a
scar
Integumentary system review Video