1. Integumentary System

2. Facts about your Skin Inegument = means covering
Integumentary System- skin, nails, hair, membranes, sweat, & oil glands
Surface Area = 1.2 to 2.2 square meters
Weight = 4 to 5 kg
Thickness mm
7% of average body weight for an adult

3. Functions of Skin Protection Synthesizes vitamin D with UV
Cushions and insulates and is waterproof
Protects from chemicals, heat, cold
Not helpful against organic solvents, heavy metals or plant
oils from poison oak
Screens UV
Acid Mantel keeps down bacteria ~pH 5
Macrophages gobble up invaders
Synthesizes vitamin D with UV

4. Functions of the Skin Regulates body heat
Sweat 500ml a day if about C
vessel dilate & constrict
Prevents unnecessary water loss
But Lipid soluble – Vitamins and steroids in
Sensory reception (nerve endings)
Thermoreceptors
Pacinian receptors
Bumps and deep pressure
Meissner’s corpuscles & Merkel disks
Aware of caress of clothing

5. Layers of the Skin
Epidermis
Dermis
Hypodermis

6. 1) Epidermis Epi = Upon Keratinized stratified squamous epithelium
nutrients reach by diffusion/ avascular
Outer layer of dead skin cells called cuticle with living level underneath .
“Ashiness” is caused by this layer of dead skin cells being very rough and raggedy
DUST you see around is made up of dead skin cells!

7. Epithelium: layers (on left) and cell types (on right)

8. Remember… Four basic types of tissue
Epithelium – epidermis just discussed
Connective tissue - dermis
Muscle tissue
Nervous tissue

9. 2) DERMIS Thick, tough, leathery, flexible layer
Made of connective tissue
Vascularized – contains blood vessels
Anchors the epidermis
Critical in Temperature regulation – contract and expand
In the dermis:
Oil glands
Sweat glands
Hair follicles
Fat tissue
Nerves
Connective tissue
Blood vessels

10. Two layers Papillary – areolar connective tissue; includes dermal papillae Reticular – “rticulum” (network) of collagen and reticular fibers

11. Fingerprints, palmprints, footprints
Dermal papillae lie atop dermal ridges
Elevate the overlying epidermis into epidermal ridges
Are “sweat films” because of sweat pores
Genetically determined
Flexion creases
Deep dermis
from continual folding

12. Finger Print

13. 3) HYPODERMIS Subcutaneous Tissue /Hypodermis / superficial fascia
not really part of skin, but helps with protective functions
superficial to connective tissue around bones
loose enough for free movement
Adipose tissue – different patters of accumulation for men and women (grows when we gain weight)
shock absorber & insulator
Deep pressure receptors

14. Cells of the Epidermis Keratinized stratified squamous epithelium
Four distinct cell types
Keratinocytes
Melanocytes
Merkel Cells
Langerhans’/ Epidermal Dendrite Cells

15. Keratinocytes Most epidermal / superficial cells
Produce keratin – “kera”= horn . Fibrous protein that gives stretch
Constantly in mitosis & pushed upwards
By the time they are on the surface they are dead
New epidermis every days
Friction= keratin formation is accelerated therefore callus- a thickening of the epidermis

16. Melanocytes Spider shaped epithelial cells that make Melanin
Deepest layers of the epidermis
Melanin made & collects in granules called melanosomes
Actin filaments move them along till they are taken up by Keratinocytes
Granules accumulate on the superficial “sunny side” of the Keratinocytes nuclei & protect nucleus from harmful UV rays

17. Merkel Cells
Shaped like a spiky hemisphere
Help with sensory of touch

18. Langerhans’ Cells / Epidermal Dendrite Cells
Macrophages (pac mans) that help activate our immune system

19. Layers of the Epidermis
Thick skin= covers palms, fingertips, and soles of the feet
FIVE layers/ strata
Thin Skin= rest of the body
FOUR layers (no stratum lucidum)
Deep to Superficial:
stratum basal
stratum spinosum
strata granulosum
strata lucidum
strata corneum

20. Epidermis and dermis of (a) thick skin and (b) thin skin
(which one makes the difference?)

21. Stratum basale/ stratum germinativum/ Basal Layer
Deepest epidermal layer
Single row of cells
Attached to dermis w/ a wavy boarder line
10-25% of cells are melanocytes & their branches
undergoing mitosis

22. stratum spinosum/ Prickly Layer
several cell layers thick
keratinocyte in this layer are spiny

23. strata granulosum/ Granular Layer
3-5 cell layer
keratinocyets flatten & start to die
not enough oxygen and nutrients b/c pushed away from blood source

24. strata lucidum/ Clear Layer
o       thin translucent band
o       only in thick skin
o       start making distinct layer

25. strata corneum/ Horny Layer
20-30 cells thick
¾ of epidermal thickness
thickened plasma membrane of cells protects from abrasion & penetration
glycolipid acts as a “water proof”
protects body from heat and water loss
“dandruff” 18kg= 40 lbs in a lifetime

26. Skin Color 1. Melanin same # of melanocytes
kind + amount of melanin made & retained
Darker = more darker melanosomes & retain longer
Freckles & pigment moles are accumulation of melanin
Sunlight causes melanin buildup
to protect from UV

27. Skin Color 2. Carotene 3. Hemoglobin Yellow-orange pigment
Accumulate in the stratum corneum
Palms of hands, soles of feet
Eat lots of rich carotene foods- becomes more obvious
3. Hemoglobin
Pinkish hue of light skin b/c can be seen through light skin

28. Skin Appendages Derived from epidermis but extend into dermis Include
Hair and hair follicles
Sebaceous (oil) glands
Sweat (sudoiferous) glands
Nails

29. HAIR Hair growth: averages 2 mm/week Active & Resting phase then Shed
At the base of the follicle, hair papilla
Contains blood vessels and nerves
Bulb
Contains matrix – epithelial cells responsible for growth
Contains melanocytes

30. Functions of hair Hair color Warmth Sense light touch of the skin
Protection – scalp
Hair color
Amount of melanin for black or brown; distinct form of melanin for red
White: decreased melanin and air bubbles in the medulla
Genetically determined though influenced by hormones and environment

31. Hair and hair follicles: complex Derived from epidermis and dermis Everywhere but palms, soles, nipples, parts of genitalia
*“arrector pili” is smooth muscle *
Hair bulb: epithelial cells surrounding papilla
Hair papilla
is connective tissue________________

32. Nails hard keratin Corresponds to hooves and claws
Grows from nail matrix

33. Sebaceous (oil) glands
Entire body except palms and soles
Oils and lubricates

34. Sweat Glands Entire skin surface Prevent overheating
except nipples and part of external genitalia
Prevent overheating
500 ml to 12 L /day!
Humans most efficient (only mammals have)
Produced in response to stress as well as heat