1. CH 5 Integumentary System

2. General Characteristics
The integumentary system includes the skin and its accessory organs.
The skin includes the epidermis, dermis and hypodermis (subcutaneous layer).
The skin is the largest organ of the body
Approximately 22 ft2
Approximately 16% of total body weight
0.5mm-4 mm thick
Thickest regions= hands and feet
Thinnest regions= eyelids and scrotum

3. THE SKIN
Epidermis
Dermis
Subcutaneous
(Hypodermis)

4. Skin Functions Thermoregulation: regulation of body temperature.
Most important function
Excess heat is carried to the skin by the blood vessels.
Skin absorbs heat and transfers it to the surrounding air.
Protection: acts as a barrier against physical trauma, chemical and biological substances.
Works the best as a barrier when it is intact- no cuts, scrapes, etc..
Approximately 50 layers of cells.

5. Skin Functions
Sense organ: provides the body with cutaneous sensations.
Sensations of touch, vibration and pain
Collects information from the outside world and sends it to the brain
What part of the body is the most sensitive?
Lips
Genitals
Hands/Feet

6. Skin Functions
Secretion and absorption: allowing certain materials to pass into or out of the skin.
Secretion:
Secretes water and oils through glands.
Can remove some waste like salts, urea, carbon dioxide and heat.
Absorption:
Taking materials into the body through the skin.
Most absorbed- fat soluble vitamins (A, D, E, K)
Some toxins are absorbed- rubbing alcohol, acetone, chlorine

7. Skin Functions
Vitamin D production: a precursor to the vitamin D molecule can be found within the skin.
When exposed to sunlight, the precursor becomes vitamin D because the light energy transforms its shapes.
It takes hours of sun exposure to produce the amount of vitamin D in a glass of milk. Is it worth it?

8. General Characteristics and Function of the Epidermis- outer layer of skin
40-50 layers of stratified squamous epithelial tissue.
Avascular
Designed to be shed and replaced frequently
Waterproof
Function: Protection

9. Cells of the Epidermis Keratinocytes- cells that produce keratin.
These cells make up 90% of the epidermis
Keratin is a tough, fibrous, water-proof protein
Most keratinocytes are dead
They don’t really become flattened until they reach the top layers due to pressures from above and below as the cells move up the epidermis.
Keratinization: the process by which the cytoplasm and organelles of a keratinocyte are replaced by keratin.
Happens as cells move up through the epidermis
This is what eventually kills the keratinocytes

10. Cells of the Epidermis Melanocytes- cells that produce melanin.
Function to protect the skin from UV radiation
Produce melanin- a brown, black pigment
It is produced by positive feedback. The more exposure- the more melanin produced- which means the more the skin can be exposed to the sun.
We all have the same # of melanocytes per square inch of the skin. Our melanocytes just produce a varying amount of melanin.
Langerhans cells- immune cells
Function to protect the body from foreign particles
These are phagocytes- engulf and destroy

11. 11

12. Cells of the Epidermis Merkel cells- touch cells.
Function to gather information (touch, temperature, vibration, and pain) and send it to the brain to be interpreted.
Melanocytes, Langerhans cells and Merkel cells account for the remaining 10% of the epidermis.

14. Layers of the Epidermis- from the bottom to top
Stratum Basale- deepest layer
Simple cuboidal layer
Lies above the dermis and blood vessels in the dermis supply this layer with blood (by diffusion)
Here is where cell division takes place, producing new skin cells and pushing older cells toward the surface.
Stratum Spinosum- superficial to the stratum basale.
8-10 layers
Cells have small projections “spiny” that help lock the cells together like velcro. 14

15. Layers of the Epidermis- from the bottom to top
Stratum Granulosum- superficial to the stratum spinosum.
3-5 layers
Cells are starting to look more squamous because of pressure from the cells above and below.
Layer where keratinization starts and cells produce keratin in large quantities.
Can see granules of keratin in the cells.
The transition layer between living and dead cells. 15

16. Layers of the Epidermis- from the bottom to top
Stratum Lucidum- superficial to the stratum granulosum.
3-5 layers
Only found on the soles and palms
Shock absorbers
Stratum Corneum- the most superficial layer of the epidermis
25-30 layers of squamous keratinocytes
Spines start to break off which causes the cells to fall off
Waterproofs the skin
Takes 5 weeks for cells to reach this layer from the stratum basale 16

17. LAYERS OF EPIDERMIS

18. Dermis- Inner Layer of Skin
General Characteristics:
Thicker than the epidermis
Composed of connective tissue
Highly vascular
Contains all accessory organs necessary for skin function (nerves, blood vessels, glands, hair follicles)
That’s why burns that extend into the dermis are much more severe. They interfere with skin’s ability to function.

19. Dermis continued…. Function:
Supports the epidermis by keeping the dividing cells of the stratum basale healthy
Regulates body temperature
Provides skin with its strength and flexibility

21. Dermis continued…. Layers of the dermis:
Papillary region: lies deep to the stratum basale of the epidermis
20% of the thickness of the dermis
Composed of areolar connective tissue with thin collagen and fine elastic fibers
Small capillary (tiny blood vessel) loops to supply nutrients to the epidermis
Contains dermal papillae

22. Dermis continued…
Dermal papillae: small projections that anchor the epidermis to the dermis
Prevent the epidermis from laterally sliding off of the dermis
Epidermal ridges: the ridges that form the fingerprints
Larger, downward projections of the epidermis that force some of the dermal papillae sideways
Function to lock the epidermis in place

23. Dermal papillae and epidermal ridges

24. What type are you?
65%
30% 5%

25. Reticular layer: lies deep to the papillary region
Includes the remaining 80% of the dermis
Composed of dense irregular tissue
Collagen fibers run in various directions which adds strength
Functions to house the accessory organs of the skin and provide the skin with strength and flexibility

26. ACT-UP
Knowing what you know about the skin, answer the following questions:
1) Why would a person with tattoos not need to have them retouched every five weeks?
2) What would cause them to fade over time?

27. Accessory Structures of the Skin
Hair- present on most surfaces of the skin
Shaft is the hair above the skin (dead keratinocytes)
Root is the hair below the skin
Follicle- Layers that surround and protect the hair root
Matrix- The dividing cells of the hair root that cause hair growth
Papillae- Small projections that anchor each hair.
Contain blood vessels that keep the matrix alive.

28. Accessory Structures of the Skin
Hair function:
Insulates against heat loss
Protects from UV radiation
Arrector pili muscle: A small muscle attached to the bulb of a hair.
Attaches to the follicle sheath
Contracts under physiological or emotional stress, which pulls the hair shafts perpendicular to the skin surface.

35. Glands- Present in different concentrations in all areas of the skin
Sebaceous glands: oil glands
Associated with hair follicles
Function to produce oil (sebum)
Keeps hair soft and flexible
Keeps skin around the hair soft and flexible
Destroys some bacteria

36. Sudoriferous glands: sweat glands
Function to release a watery secretion (sweat) to cool the body.
Two types:
Eccrine- Respond to elevated body temperatures
Apocrine- Respond to stress (adrenaline rush)
These release sweat along with some proteins and fat that bacteria LOVE! As bacteria feed on this thick sweat, they produce a stinky by-product = B.O.!!

37. Ceruminous glands: modified sweat glands that are only found within the external ear canal
Function to produce cerumen (wax) that protects the eardrum by trapping substances.
It’s important to keep this production at a low level- so water doesn’t get trapped that will support the breeding of bacteria.