Integumentary System

Chapter 6The Skin, etc.

Test is Oct. 8th!!!!Note Cards Due September 29th!!!

Integumentary System

• Consists of…– Skin– Sweat glands (sudoriferous glands)– Oil glands (sebaceous glands)– Hair– Nails

Functions of Integumentary System

• Protection from injury– Mechanical (punctures, pricks, etc.)– Pathogen entry

• Physically stops pathogens• Chemically stops pathogens

• Sensation– Feeling

• Metabolic Functions

• Temperature Regulation

• Looks

Skin Structure• Epidermis

– Superficial– avascular– Consists of 4 -5 layers of epithelial cells

• Dermis– Deep– Vascular– Fibrous connective tissue– Accessory appendages

http://missinglink.ucsf.edu/lm/DermatologyGlossary/img/Dermatology%20Glossary/Glossary%20Histo%20Images/Epidermis_20x-210.jpg

Epidermis

• Keratinized stratified squamous epithelium

• Avascular• Consists of 4-5 cell

typeshttp://missinglink.ucsf.edu/lm/DermatologyGlossary/img/Dermatology%20Glossary/Glossary%20Histo%20Images/Epidermis_20x-210.jpg

4 types of cells

• Keratinocytes– structure

• Melanocytes– pigment

• Merkel cells– sensation

• Langerhans’ cells– phagocytes

Keratinocytes• 95% of all cells in epidermis are keratinocytes

• Found in all layers of epidermis

• Produces keratin– Tough, fibrous structural protein– Protects underlying layers from environmental

factors (heat, UV radiation, water loss)– Key component of hair and nails

• Connected to each other by desmosomes (cell structure that is used for cell to cell adhesion)

Keratinocytes

• New skin is made deep and “pushed” up

• Keratin is made in the journey up from the bottom of the skin.

• By the time they reach the upper layer of skin keratinocytes are just scale-like “bags” of keratin

http://download.videohelp.com/vitualis/med/thick_skin_epidermis_w.jpg

Melanocytes

• Produce the pigment melanin

• Found in the deepest layer of the epidermis

• Spider shaped

• Package melanin into granules called melanosomes and then transfer those melanosomes to the keratinocytes

http://www.ccs.k12.in.us/chsBS/kons/kons/images/Skin_tws_16_02.jpg

Melanocytes

• Melanin granules protect the DNA in the nucleus from UV damage

Thick skin

• Found on soles of feet and palms of hands, also found on fingers and toes

• Contains 5 epidermal sheets– Stratum basale – Stratum spinosum– Stratum granulosum– Stratum lucidum– Stratum corneum

http://download.videohelp.com/vitualis/med/thick_skin_epidermis_w.jpg

Thin Skin

• Found everywhere else

• 4 layers– Stratum basale – Stratum spinosum– Stratum granulosum– Stratum corneum

• The layers themselves are thinner than thick skin

http://missinglink.ucsf.edu/lm/DermatologyGlossary/img/Dermatology%20Glossary/Glossary%20Histo%20Images/Epidermis_20x-210.jpg

Stratum Corneum

• Outermost stratum

• 20-30 layers of squamous dead cells that contain high amounts of keratin

• Helps in water absorption and retention

• Protection

• Sloughs off (ashy skin)

Stratum Lucidum

• Occurs only where skin is thick and hairless

• 3 to 5 layers of dead, flattened keratinocytes

• Appears clear under a microscope because the cells have no nuclei

Stratum Granulosum

• 2 – 4 cell layers thick

• Cells continue to flatten (nuclei and organelles disintegrate)

• Filled with keratohyalin (staining granules required for keratin formation)

• Keratinization begins here

Stratum spinosum

• 8 to 10 layers thick• Irregular shaped cells• Spinous or prickle cell• Rich in RNA (needed for protein synthesis)• Some cells can still be mitotic• Cells shrink, exposing desmosomes (causes

spiny appearance)• Lipids present create a hydrophobic barrier

Stratum basale

• Deepest layer

• Firmly attached to the dermis

• Single layer of cells

• Cells undergo mitosis

• Contain melanocytes

Stratum germinativum

• “growth” layer

• Describes strata spinosum and basale together

***this term’s definition varies based on the source***

• ..\Desktop\Videos\The_Skin.wmv

Dermis

• Layer between the epidermis and subcutaneous

• Strong, flexible fibrous tissue

• Composed of 2 layers

–Papillary layer

–Reticular layer

Papillary Layer

• Upper 1/5

• Intertwined with rete ridges (Epidermal thickenings that extend downward between dermal papillae) in the epidermis

• Composed of loose (areolar) CT

• Contains lots of blood vessels that constrict in cold weather and dilate in hot weather

Reticular Layer

• Lower 4/5 of the dermis

• Dense irregular CT

• Primary location for elastic fibers

• Most skin appendages are found here

http://missinglink.ucsf.edu/lm/DermatologyGlossary/img/Dermatology%20Glossary/Glossary%20Histo%20Images/Papillary_vs_Reticular_Dermis_10x-208.jpg

Dermal Growth & Repair• Dermis does not continually regenerate

• If it is not repaired with new skin, a scar will form

• Where an incision has been made plays a role in whether or not it will heal quickly.

• Stretch marks – elastic fibers are stretched too quickly or for too long

Langer’s Cleavage Lines• Dense

bundles of white collagenous fibers that make up the reticular layer of the dermis orient themselves in a pattern

Langer’s Cleavage Lines

• Incisions made across Langer’s cleavage lines heal more slowly than cuts made along or parallel to Langer’s cleavage lines

What color is your skin?

• Well, that depends on your…

–Melanin

–Carotene

–Hemoglobin

• Only melanin is actually skin

Skin Color• Melanin

– Polymer of tyrosine – synthesis is catalyzed by tyrosinase (Albinos lack this enzyme)

– Range in color from yellow, reddish brown to black

– All people have the same # of melanocytes– Skin color variation depends on how much

and what type of melanin is made– Freckles and moles are local spots of

melanin

Skin Color

• Carotene–Yellow to orange pigment found in

food–Eat too much and it is temporarily

deposited in the stratum corneum of thick skin

• Hemoglobin–Causes a somewhat pink color in

caucasians

http://media.photobucket.com/image/skin%20color/Yoshi1684/04-skin-color-map_cl.png

Skin Appendages

• Sebaceous glands

• Sudoriferous glands

• Ceruminous glands

• Hair

• Nails

Sebaceous Glands

• Alveolar glands found everywhere but palms of hands and soles of feet

• Secrete oil (sebum) for the hair and skin

• Reduces fungal activity on the skin surface

• Oxidation can cause sebum to darken, forming a blackhead.

Sudoriferous Glands

• Sweat glands

– Classified as either eccrine (merocrine) or apocrine

Eccrine (Merocrine) glands

• Distributed all over the body

• Simple, coiled, tubular glands

• Produce sweat– Contains salts, ammonia, uric acid, urea– Eliminates waste– Maintains constant core temperature– pH of sweat is 4-6, creating an “acid shield”

on the body

Apocrine glands

– Deep in subcutaneous layer (armpit, areola of the breast, pigmented anus)

– Larger than eccrine sweat glands– Sweat is thicker than eccrine sweat– Odor is often associated with theses glands– Become active at puberty

Ceruminous Glands

• Modification or variety of apocrine sweat glands

• Excretory ducts that open onto the ear canal and/or with skin hair follicle on the neck area

What else is attached to the skin????

http://assets.babycenter.com/ims/2008/03mar/20080327/april_2008_hair_new_mamma21.jpg

http://blogs.smarter.com/blogs/long%20nails.jpg

Hair

• Hair is a flexible strand made of highly keratinized dead cells.

• Cells do not flake off individually like they do on the skin.

• Made by the living hair follicle

Hair follicle

• Hair has a shaft that protrudes from the skin.

• Root gets wider at the base

• Made of 3 concentric rings– Medulla– Cortex– Cuticle

Medullahttp://shs.westport.k12.ct.us/forensics/09-trace_evidence/splitting_hairs.htm

• The innermost layer of the hair. 

• It is made of cells that form a shaft through the middle of the hair. 

• Different amounts of medulla may be present in the hair.

• Medulla

Cortexhttp://shs.westport.k12.ct.us/forensics/09-trace_evidence/splitting_hairs.htm

• The intervening layer of the hair (i.e., between the cuticle and the medulla). 

• It is made of spindle shaped cell and pigment granules (these give color to the hair). 

• You may also find ovoid bodies (look like large pigment granules) and cortical fusi (small bubble-like structures) in the cortex.

Cuticlehttp://shs.westport.k12.ct.us/forensics/09-trace_evidence/splitting_hairs.htm

• The outermost layer of the hair. 

• It is made of keratin.  • The cuticle is really a

series of overlapping scales - very resistant to chemical decomposition

http://www.answersingenesis.org/assets/images/articles/am/v2/n3/Human_Hair3.jpg

http://academic.pgcc.edu/~aimholtz/AandP/LectureNotes/ANP1_Lec/205Lec.html

Hair and Hair Follicles• The hair follicle surrounds

much of the hair root.• It contains an outer

connective tissue sheath and an inner epithelial root sheath.

• At the base of the hair follicle is a single layer of mitotic cells derived from the stratum basale. This is the hair matrix.

• All the cells of the hair are derived from the hair matrix. Just beneath the hair matrix is an obvious dermal papilla called the hair papilla. It contains the blood vessels that nourish the matrix and the cells of the hair follicle.

http://academic.pgcc.edu/~aimholtz/AandP/LectureNotes/ANP1_Lec/205Lec.html

Notice the hair shaft, hair follicle, papilla, and the multiple sebaceous glands.

http://academic.pgcc.edu/~aimholtz/AandP/LectureNotes/ANP1_Lec/205Lec.html

Hair and Hair Follicles http://academic.pgcc.edu/~aimholtz/AandP/LectureNotes/ANP1_Lec/205Lec.html

• Wrapped around the bulb of the follicle is a network of sensory nerve endings known as the hair root plexus. Allow the hairs to serve a sensory function.

• Attached to each hair is a bundle of smooth muscle known as an arrector pili muscle. In times of fright or cold, these muscles contract and cause the hair to stand on end – and produces goose bumps.– Increases airflow in mammals with

significant hair (i.e., not humans) and increases the apparent size of an animal with significant hair. Vestigial in humans.

The arrow indicates an arrector pili muscle. In this picture, you should also try to identify the shaft, root, follicle, hair papilla, and sebaceous gland.

http://academic.pgcc.edu/~aimholtz/AandP/LectureNotes/ANP1_Lec/205Lec.html

Nails• Nail body – visible part

of the nail

• Nail Root – hidden under the cuticle

• Cuticle – fold of skin

• Lunula – crescent shaped white area

• Nail bed – appears pink because of the number of blood vessels, under the nail body

• Free edge – the “white” part that hangs over http://4.bp.blogspot.com/_TGR8TxUfiIw/

RmtdbrJUuTI/AAAAAAAAAF0/78AjZ0Jmdbg/s400/14.jpg

Cell Cycle

• Interphase• Cell growth, where cell spends most of its time

• Mitosis– Prophase– Metaphase– Anaphase– Telophase

• Cytokinesis

http://www.biologycorner.com/resources/cell_cycle.jpg

A schematic representation of the mammalian cell cycle.

Collins K et al. PNAS 1997;94:2776-2778

©1997 by The National Academy of Sciences of the USA

• S = Synthesis (DNA replication)

• G1 and G2 = growth and reorganization

• G0 = state of quiet (cells stop cycling)

• Cell checkpoints = quality control

Cell Cycle and Cancer

• Two things happen…

• Checkpoint doesn’t register that something is wrong and allows the “bad” cell to continue through the cell cycle

• “bad” cells are insensitive to the signals that tell the cell what to do (i.e. die)

What type of cancers do I need to know about?

• Basal cell carcinoma

• Squamous cell carcinoma

• Melanoma

Skin Disorders

• Impetigo – bacterial infections

• Tinea – fungal infection (ringworms, jock itch, athelete’s foot)

• Warts – viral infection

• Boils – Staph infections of hair follicles

Vascular and Inflammatory

• Bed sores

• Hives

• Scleroderma – autoimmune diseases

• Psoriasis

• Eczema

Body Temperature….ooops• The skin helps sense changes in the

external temperature and then allows the body to maintain homeostasis.

• Sometimes though, there are problems in the body temperature

• Fever– unusually high body temperature– Pyrogens (“fire-makers”) cause the body to

produce a fever– Is thought best to let the fever “run its course”

• Malignant hyperthermia– Genetic condition– Abnormally high body temp– Muscles become rigid when exposed to

certain muscle relaxers or anesthetics

• Heat exhaustion– Body loses too much fluid from heat-loss

mechanisms– Normal body temperature is maintained– Treated with rest in a cool area and fluid

replacement

• Heat Stroke– Body cannot maintain normal temperature– Age, disease, drugs, heat play a role– 105 degrees or higher– Immediate cooling down and fluid

replacement required

• Hypothermia– Cannot maintain normal body temperature in

cold conditions– Body temperature is 95 degrees or lower– Slowly warm the person back up– ..\..\Desktop\Videos\Hypothermia.asf

• Frostbite– Localized damage– Necrosis and gangrene can occur– ..\..\Desktop\Videos\Frostbite.asf