1. Integumentary System

3. Why hairy? Read article on p170.
Why are we hairy?
Explain hypertrichosis.
What theories do scientists have about why we have hair in the places we do?
Is there an evolutionary relationship? Explain.

4. Functions of Skin? Protects underlying tissues and organs
Excretes salts, water, and organic wastes (glands)
Maintains body temperature (insulation and evaporation)
Synthesizes vitamin D3
Stores lipids
Detects touch, pressure, pain, and temperature by sensory receptors located in dermis

5. Observed by physicians for health analysis
First line of defense
Observed by physicians for health analysis
Color
Elasticity
sensitivity

6. Parts of the Integument
The integument is made up of 2 parts:
cutaneous membrane (skin)
accessory structures
Sub-Q (subcutaneous)
The integument is the largest system of the body is 16% of body weight and 1.5 to 2 m2 in area.

7. The Subcutaneous Layer
Subcutaneous layer (superficial fascia or hypodermis): loose connective tissue, below the dermis, location of hypodermic injections

9. Accessory Structures Connections Originate in the dermis
Extend through the epidermis to skin surface:
hair
nails
multicellular exocrine glands
Receptors
Connections
Circulatory system:
blood vessels in the dermis
Nervous system:
sensory receptors for pain, touch, & temperature

10. Characteristics of epidermis: How are these cells nourished?
Avascular, stratified squamous epithelium
How are these cells nourished?
Nutrients and oxygen diffuse from capillaries in the dermis

11. Cells of the Epidermis Keratinocytes: contain large amounts of keratin
the most abundant cells in the epidermis
Assist in immune fxn by producing hormone-like substance that stimulates dev of certain WBC.
Thick Skin
Covers the palms of the hands and soles of the feet
Has 5 layers of keratinocytes
Thin Skin
Covers most of the body
Has 4 layers of keratinocytes

12. How do cells of the skin replace themselves? keritization
The formation of a layer of dead, protective cells filled with keratin
Cells begin to harden when tough fibrous waterproof keratin proteins are synthesized and stored within cell.
Occurs on all exposed skin surfaces except eyes

13. Layers of the Epidermis
From basal lamina to free surface:
stratum germinativum/basale
stratum spinosum
stratum granulosum
stratum lucidum
stratum corneum
Figure 5–3

15. Stratum Germinativum The “germinative layer”:
has many (3-5 cells thick) germinative (stem) cells or basal cells
is attached to basal lamina by hemidesmosomes
forms a strong bond between epidermis and dermis
Structures of Stratum Germinativum
Epidermal ridges (e.g., fingerprints)
Dermal papillae (tiny mounds):
increase the area of basal lamina
strengthen attachment between epidermis and dermis

16. Cells of Stratum Germinativum
Merkel cells:
found in hairless skin
respond to touch (trigger nervous system)
Melanocytes:
contain the pigment melanin
scattered throughout stratum germinativum

17. Stratum Spinosum The “spiny layer”: Cells of Stratum Spinosum
produced by division of stratum germinosum
8–10 layers of keratinocytes bound by desmosomes
cells shrink until cytoskeletons stick out (spiny)
Cells of Stratum Spinosum
Continue to divide, increasing thickness of epithelium
Contain Langerhans cells, active in immune response (against pathogens and skin cancers)

18. Stratum Granulosum The “grainy layer”
Stops dividing, starts producing:
keratin:
a tough, fibrous protein
makes up hair and nails
keratohyalin
dense granules
cross-link keratin fibers
Cells of Stratum Granulosum
Produce protein fibers
Dehydrate and die
Create tightly interlocked layer of keratin surrounded by keratohyalin

19. Stratum Lucidum The “clear layer”: Cells of Stratum Lucida
found only in thick skin
covers stratum granulosum
Cells of Stratum Lucida
Flat
Dense
Filled with keratin

20. Stratum Corneum The “horn layer”: exposed surface of skin
15 to 30 layers of keratinized cells
water resistant
shed and replaced every 2 weeks

21. What are the structures & functions of the dermis?
Is located between epidermis & subcutaneous layer
Fxns to nourish epidermis and house accessory organs of skin
Has 2 components:
outer papillary layer
deep reticular layer

22. Reticular layer Consists of dense irregular connective tissue
Contains larger blood vessels, lymph vessels, and nerve fibers
Contains collagen and elastic fibers
Houses sensory neurons: pacinian corpuscle: detects deep pressure and vibration

23. The Papillary Layer Consists of areolar tissue
Contains smaller capillaries, lymphatic vessels, and sensory neurons
Sensory neurons: meissner’s corpuscle: detects ligh touch

24. What are the structures & functions of the subcutaneous layer?
The Hypodermis
The subcutaneous layer or hypodermis:
lies below the integument
stabilizes the skin
allows separate movement
made of elastic areolar and adipose tissues
connected to the reticular layer of integument by connective tissue fibers
has few capillaries and no vital organs
is the site of subcutaneous injections using hypodermic needles

25. Adipose Tissue Deposits of subcutaneous fat:
have distribution pattern determined by hormones
are reduced by cosmetic liposuction

26. Water Gain Through Skin
Water Loss Through Skin
Dehydration results:
from damage to stratum corneum, e.g., burns and blisters (insensible perspiration)
from immersion in hypertonic solution, e.g., seawater (osmosis)
Water Gain Through Skin
Hydration: (skin is water resistant, not water proof)
results from immersion in hypotonic solution, e.g., freshwater (osmosis)
causes stretching and wrinkling skin

27. Perspiration Insensible perspiration: Sensible perspiration:
interstitial fluid lost by evaporation through the stratum corneum
Sensible perspiration:
water excreted by sweat glands

29. What causes different skin colors?
Skin color depends on:
blood circulation (red cells)
the pigments carotene and melanin
Melanin
Yellow-brown or black pigment
Produced by melanocytes in stratum germinativum
Stored in transport vesicles (melanosomes)
Transferred to keratinocytes
Carotene
Orange-yellow pigment
Found in orange vegetables
Accumulates in epidermal cells and fatty tissues of the dermis
Can be converted to vitamin A

30. Function of Melanocytes
Melanin protects skin from sun damage
Skin color depends on melanin production, not number of melanocytes
Ultraviolet (UV) radiation:
causes DNA mutations and burns which lead to cancer and wrinkles

31. Capillaries and Skin Color
Oxygenated red blood contributes to skin color:
blood vessels dilate from heat, skin reddens
blood flow decreases, skin pales
Cyanosis
Bluish skin tint
Caused by severe reduction in blood flow or oxygenation
Jaundice:
buildup of bile produced by liver
yellow color
Addison’s disease:
and other diseases of pituitary gland
skin darkening
Vitiglio:
loss of melanocytes
loss of color

32. Skin Damage
Sagging and wrinkles (reduced skin elasticity) are caused by:
dehydration
age
hormonal changes
UV exposure
Stretch Marks
Thickened tissue resulting from:
excessive stretching of skin due to:
Pregnancy
weight gain

33. Vitamin D Epidermal cells produce cholecalciferol (vitamin D3):
in the presence of UV radiation
Liver and kidneys convert vitamin D into calcitriol:
to aid absorption of calcium and phosphorus
Insufficient vitamin D:
can cause rickets

34. Epidermal Growth Factor (EGF)
Is a powerful peptide growth factor
Is produced by glands (salivary and duodenum)
Is used in laboratories to grow skin grafts
Functions of EGF
Promotes division of germinative cells
Accelerates keratin production
Stimulates epidermal repair
Stimulates glandular secretion

35. Dermatitis An inflammation of the papillary layer
Caused by infection, radiation, mechanical irritation, or chemicals (e.g., poison ivy)
Characterized by itch or pain
Strong, due to collagen fibers
Elastic, due to elastic fibers
Flexible (skin turgor)

36. Lines of Cleavage Collagen and elastic fibers in the dermis:
are arranged in parallel bundles
resist force in a specific direction
Lines of Cleavage
Lines of cleavage establish important patterns:
a parallel cut remains shut, heals well
a cut across (right angle) pulls open and scars

37. Dermal Circulation Arteries Veins Cutaneous plexus: Papillary plexus:
a network of arteries along the reticular layer
Papillary plexus:
capillary network from small arteries in papillary layer
Veins
Venous plexus:
capillary return deep to the papillary plexus
Contusion:
damage to blood vessels resulting in “black and blue” bruising
Figure 5–8

38. What determines hair growth, texture,& color?
Location of Hair
The human body is covered with hair, except palms, soles, lips, portions of external genitalia
Protects and insulates
Guards openings against particles and insects
Is sensitive to very light touch
Hair FollicleIs
located deep in dermis
Produces nonliving hairs
Is wrapped in a dense connective-tissue sheath
Base is surrounded by sensory nerves (root hair plexus)

39. Accessory Structures of Hair
Arrector pili:
involuntary smooth muscle
causes hairs to stand up
produces “goose bumps”
Sebaceous glands:
lubricate the hair
control bacteria

40. Regions of the Hair Hair root: Hair shaft: lower part of the hair
attached to the integument
Hair shaft:
upper part of the hair
not attached to the integument

41. How Hair Grows Hair Matrix Layers in a Hair
Hair begins deep in the dermis:
the hair papilla contains capillaries and nerves
the hair bulb produces hair matrix
Hair Matrix
A layer of dividing basal cells
Produce hair structure
Push hair up and out of skin
Layers in a Hair
Medulla:the central core
Cortex:the middle layer
Cuticle:the surface layer

42. Keratin Layers in the Follicle As hair is produced, it is keratinized:
medulla contains flexible soft keratin
cortex and cuticle contain stiff hard keratin
Layers in the Follicle
Internal root sheath:
the inner layer
contacts the cuticle in lower hair root
External root sheath:
extends from skin surface to hair matrix
Glassy membrane:
a dense connective-tissue sheath
contacts connective tissues of dermis

43. Hair Growth Cycle Growing hair: Club hair: New hair growth cycle:
is firmly attached to matrix
Club hair:
is not growing
is attached to an inactive follicle
New hair growth cycle:
follicle becomes active
produces new hair
club hair is shed

44. Types of Hairs Hair Color Vellus hairs: Terminal hairs:
soft, fine
cover body surface
Terminal hairs:
heavy, pigmented
head and eyebrows
other parts of body after puberty
Hair Color
Produced by melanocytes at the hair papilla
Determined by genes

45. What are the skin glands & secretions?
Exocrine Glands
Sebaceous glands (oil glands):
Simple branched alveolar glands:associated with hair follicles
Sebaceous follicles:discharge directly onto skin surface
holocrine glands
secrete sebum
Contains lipids and other ingredients
Lubricates and protects the epidermis
Inhibits bacteria

46. Sweat Glands Apocrine: Merocrine glands
found in armpits, around nipples, and groin
Associated with hair follicles
Produce sticky, cloudy secretions
Break down and cause odors
Merocrine glands
widely distributed on body surface especially on palms and soles
Cools skin, flushes microorganisms and harmful chemicals from skin

47. Other Integumentary Glands
Mammary glands:
produce milk
Ceruminous glands:
protect the eardrum
produce cerumen (earwax)

48. What is the structure of nails, & how do they grow?
Nails protect fingers and toes:
made of dead cells packed with keratin
metabolic disorders can change nail structure
produced in a deep epidermal fold near the bone called the nail root
Nail body:
the visible portion of the nail
covers the nail bed
Lunula:
the pale crescent at the base of the nail