Histology-Integumentary System

Front 1

What covers the body protecting the internal organs from desiccation and from external toxins?

Back 1

the skin or integument

Front 2

What are the main functions of the integument?

Back 2

-acts as a barrier
-prevents desiccation
-thermoregulation
-mediates communication
-skin is a source for the photochemical production of Vitatmin D

Front 3

The integument act as a ___ to physical, biological (immunological) and chemical agents and to radiation (UV).

Back 3

barrier

Front 4

The integument functions in thermoregulation by what?

Back 4

-evaporative cooling (perspiration)
-heat radiation at the surface of the body (blood circulation)
-insulation (to a relatively small degree in humans)

Front 5

How does the integument mediate communication wtih the environment?

Back 5

-sensory receptors in the skin recieve information
-fingers and nails allow fine manipulation
-skin is prime component of social communication

Front 6

What is the largest organ in the body?

Back 6

skin

Front 7

Skin comprises how much of our body mass %?

Back 7

16%

Front 8

How many recognized skin diseases are there and which two are the most common?

Back 8

~2000; acne and eczema

Front 9

How much of the population do skin diseases affect?

Back 9

20-30%

Front 10

T/F With few exceptions skin diseases are not life threatening but are a leading cause of missed work.

Back 10

True

Front 11

Melanoma (cancer of pigment cells) is serious and the incidence has increased ___% in past five decades.

Back 11

800%

Front 12

What can be life threatening and can often result in disfigurement and loss of mobility if not properly treated?

Back 12

burns

Front 13

What are layers of skin from the outside to the inside?

Back 13

epidermis
dermis
hypodermis

Front 14

The epidermis is the outer layer of skin and is composed of what kind of epithelium?

Back 14

keratinized stratified squamous epi

Front 15

The dermis is layer of ____ tissue underlying the epidermis.

Back 15

dense irregular connective tissue

Front 16

The hypodermisis a layer of ____ tissue underlying the dermis. What is it often considered rather than just part of the skin?

Back 16

adipose connective tissue

superficial fascia covering the body

Front 17

The epidermis is composed of layers of cells called ____ that undergo a sequential program of differentiation.

Back 17

keratinocytes

Front 18

What are the cell layers that make up the epidermis?

Back 18

-basal layer (stratum basale)
-spinous layer (stratum spinosum)
-granular layer (stratum granulosum)
-cornified layer (stratum corneum)

Front 19

What is the cell type in the basal layer and where does cell division occur in this layer?

Back 19

-columnar or cuboidal
-within or just above the basal layer

Front 20

T/F All of the basal cell keratinocytes are actively cycling.

Back 20

False- only about half (others can be recruited (wounding))

Front 21

What kind of diseases appear as a result from imbalance of stimulatory and inhibitory growth factors (cytokines)?

Back 21

Hyperproliferative (psoriasis)

Front 22

How are basal cells attached to their neighbors?

How are basal layer cells attached to the basement membrane?

Back 22

-desmosomes that contain cadherin molecules (Ca dependent adhesion molecules)
-hemidesmosomes (use integrins to bind extracellular matrix molecules of the basement membrane)

Front 23

Desmosomes and hemidesmosomes of the basal layer are joined to intracellular intermediate filaments composed of what?

Back 23

keratin

Front 24

What percentage of cell mass do keratins comprise in mature keratinocytes?

Back 24

85%

Front 25

In older terminology, the term keratin was only used for what?

Back 25

the protein of the mature (dead) keratinocytes

Front 26

While keratin filaments are the most apparent intracellular organelles in all keratinocytes, living keratinocytes also contain what other cellular organelles?

Back 26

actin filaments and microtubules

Front 27

What are keratins?

How many different keratin genes are there?

Back 27

-a large family of proteins
-20 or more

Front 28

What are the types of keratin proteins and which is acidic and basic?

A member of each type of keratin protein must be present in order for what to form?

Back 28

Type 1 keratins (more acidic)
Type 2 keratins (more basic)
Filaments

Front 29

T/F
-Epithelial cells generally express one type 1 keratin and one type 2 keratin.
-Epithelia from different tissues express the same pairs of keratin genes.

Back 29

-True
-False- different pairs of keratin genes

Front 30

How are the different pairs of keratin genes turned on in the epidermis?

Back 30

as the cells move upward and proceed through their program of differentiation

Front 31

Cells destined to differentiate leave the basal layer and move into what layer?

Back 31

the adjacent spinous layer (stratum spinosum)

Front 32

In order for cells to migrate and intercalate into the upper layers what must they do?

Back 32

exchange adhesion to the basement membrane for adhesion to other keratinocytes

Front 33

As the cells leave the basal layer and migrate into the spinous layer they attain a more (flattened or cuboidal) shape and (increase or decrease) in the number of desmosomes and amounts of keratin.

Back 33

flattened
increase

Front 34

What appears in the upper spinous layers?

Back 34

novel organelles termed membrane-coating granules or lamellar bodies

Front 35

What is the granular layer (stratum granulosum) characterized by?

Back 35

the appearance of keratohyalin granules among the keratin filaments

Front 36

What do the keratohyalin granules in the granular layer contain that serve to bundle the keratin filaments together?

Back 36

filaggrin

Front 37

What enzyme is produced in the granular layer but NOT activated?
What does this enzyme do?

Back 37

transglutaminase
a Ca dependent enzyme that cross links gamma amide groups of gluatamine w/ epsilon amino groups of lysine to form a very stable covalent protein crosslink on the inside of the cell membrane

Front 38

What is the cornified layer composed of?

Back 38

layers of dead cells

Front 39

Sometimes in thick epidermis there is an extra layer bw the granular and cornified layers called what?

Back 39

stratum lucidum

Front 40

What is the sharp transition seen bw the granular and cornified layers?

Back 40

keratin filaments become highly cross-linked by the formation of S-S bonds and by action of keratohyalin

Front 41

In the cornified layer membrane coating granules are exocytosed into intercellular space where their content of lipid is important in forming what?

Back 41

a permeability barrier for water retention and resistance

Front 42

The cornified layer provides what percentage of water retention ability?

Back 42

98%

Front 43

The plasma membrane of the cornified layer becomes thickened along its inner surface by deposition of ____ at the plasma membrane and their cross-linking by _____, activated by an increase in calcium to form what?

Back 43

proteins
translutaminase
cornified envelope

Front 44

The sloughing of dead cells at skin surface seems to be a programmed event that can be altered in certain what?

Back 44

skin diseases

Front 45

___ of skin surface serves as an inhospitable environment for growth of microorganisms.

Back 45

dryness

Front 46

The epidermis turns over on the order of about ____ days depending on the region of the skin. (different regions show different thickness of epidermis and the epidermis thickens in repsonse to use)

Back 46

14-30

Front 47

What are certain diseases of living cell layers of the epidermis due to?

Back 47

genetic or acquired defects in keratinocyte organelles

Front 48

What in the epidermis provides clues to the cause of a disease?

Back 48

location of blistering in the various levels

Front 49

Diseases due to autoimmune attach on cell surface adhesion proteins:
-____ results from an autoimmunity to proteins mediating adhesion bw basal epidermal cells and the basement membrane
-_____ results from autoimmunity to cell adhesion proteins in the spinous layer

Back 49

-Bullous pemphigoid
-Pemphigus vulgaris

Front 50

Genetic diseases due to mutations in keratin genes:
-____ results from a mutation in keratin genes expressed in basal layer cells
-____ results from a mutation in keratin genes expressed in spinous layer cells

Back 50

-Epidermolysis bullosa simplex
-Epidermolytic hyperkeratosis

Front 51

During Vitamin D production, ____ is concentrated into the living layers of epidermis where it is photochemically converted to vitamin D3 so technically not a vitamin but rather a ____.

Back 51

7-dehydrocholesterol
steroid hormone

Front 52

Without exposure of skin to sunlight, how must vitamin D be supplied?

Back 52

in the diet

Front 53

What is the primary effect of vitamin D deficiency?

Back 53

failure to absorb dietary calcium

Front 54

What does a vitamin D deficiency in children result in?

Back 54

a lack of mineralization of growing bones- rickets

Front 55

What is derived from the neural crest and produces melanin, the primary coloration of the epidermis?

Back 55

Melanocytes

Front 56

Melanocytes occur in what layer of the epidermis?

Back 56

basal layer

Front 57

Melanocytes send processes to contact many ____ (usually ___) primariy in the basal layer and in layers immediately above.

Back 57

keratinocytes
30

Front 58

T/F Melanocytes have many desmosomal connections to keratinocytes.

Back 58

False- have no connections

Front 59

Melanocytes convert ___ to melanin which is deposited in ____ and transferred to the keratinocytes by phagocytosis.

Back 59

tyrosine
melanosomes

Front 60

What are arranged to protect nuclei from irradiation by ultraviolet light?

Back 60

melanosomes

Front 61

How does the epidermis respond to irradiation by ultraviolet light?

Back 61

-Melanin undergoes an immediate darkening through a photochemical reaction
-Melanocytes increase production of melanin & numbers of melanosomes. Inactive melanocytes become active.
-Melanocytes increase the arborization of their cell processes.
-Keratinocytes increase the uptake of melanosomes from melanocytes.

Front 62

Melanosomes within the keratinocytes are degraded as keratinocytes move (downward, upward, sideways)?

Back 62

upward

Front 63

T/F
-All humans have different numbers of melanocytes.
-Skin color differences are due to differences in teh number, size and arrangement of melansomes.

Back 63

-False: about the same number
-True

Front 64

In darkly pigmented skin, ____ persist longer as ____ move upward.

Back 64

melanosomes
keratinocytes

Front 65

What plays significant roles in cancer by protecting the skin from the carcinogenic effects of UV light?
However, when these become cancerous, they give rise to aggressive tumors called what?

Back 65

melanocytes
melanomas

Front 66

What are other unique cells the epidermis contains?

Back 66

Langerhans cells and Merkel cells

Front 67

Langerhans cells:
-____ derived dendritic cells found commonly in living layers of epidermis
-they are antigen presenting cells mediating ___ immunity and play a role in ____
- At electron microscope level they contain granules with a "tennis racket shape" called ____

Back 67

-monocyte
-T cell; allergic contact dermatits
-Birbeck granules

Front 68

Merkel cells
-present in what layer of thick skin of palms and soles?
-posses what attachments to keratinocytes?
associated w/ an expanded nerve terminal and thought to be involved in what?
-contain dense granules containing what?

Back 68

-basal
-keratins and desmosomal
-touch sensation
-neuroendocrine components

Front 69

What is the connective tissue underlying the epidermis called?

Back 69

dermis

Front 70

What do the dermis acellular components consists of?

Back 70

primarily collagen (80% type 1 and 15% type 3), elastin, and glycosaminoglycans

Front 71

What contains an extensive vascular system, neurons, smooth muscle and fibroblasts?

Back 71

dermis

Front 72

Is the dermis or epidermis thicker?

Back 72

dermis (comprises 80-90% total epidermis and dermis)

Front 73

What is considered the principal mechanical barrier of the skin?

Back 73

dermis

Front 74

What are the layers the dermis is divided into?

Back 74

papillary layer
reticular layer

Front 75

Which layer of the dermis is named for the dermal papillae that extend up in ridges into the overlying epidermis?

Back 75

papillary layer

Front 76

What does the papillary layer of the dermis include?

Back 76

the basal lamina (type IV collagen, laminin, bullous pemphigoid antigen) adjacent to the basal layer of the epidermis

Front 77

Underneath the basement membrane, the papillary layer of the dermis is composed of what?

Back 77

thin collagenous and elastic fibers

Front 78

Anchoring fibers composed of type ___ collagen anchor adjacent to hemidesmosomes of basal epidermal cells in the papillary layer of the dermis.

Back 78

VII

Front 79

The papillary layer of the dermis contains a large number of what?

Back 79

fibroblasts, mast cells, and macrophages

Front 80

What is the reticular layer of the dermis composed of?

Back 80

coarse collagenous and elastic fibers (irregular dense CT)

Front 81

Which layer of the dermis has fewer cells?

Back 81

reticular layer

Front 82

Arteries and veins run through which skin layer and branch upward to form plexuses of anastomosing vessels?

Back 82

hypodermis

Front 83

What plexus is at the junction of the hypodermis and dermis?

Back 83

cutaneous plexus

Front 84

What plexus is just beneath the epidermis?

A similar plexus exists for what?

Back 84

papillary plexus

lymphatic drainage

Front 85

The vascular system provides ___ to the dermis and by diffusion to the epidermis.

Back 85

nourishment

Front 86

What does the vascular system function in?

Back 86

thermoregulation

Front 87

Vascular system: blood flow is controlled by contraction of arterioles and venules to send blood through capillary beds for ____. In some regions of the skin, ___ or shunts can send blood directly from arterioles to venules.

Back 87

-heat radiation
-arteriovenous anastomoses

Front 88

Which layer of skin contains a number of neuronal elements responsible for touch, pain, itch, and temperature reception? (in some cases these receptors are represented by free nerve endings w/out specialized structure). Some of these nerve endings are associated with what types of cells in the epidermis?

Back 88

dermis

Merkel

Front 89

In some cases, nerves end in specialied structures such as ___ found in the dermal papillae and function as mechanoreceptors in touch perception; or ____ which found deeper in the dermis (and in the hypodermis) and function in pressure sensation.

Back 89

Meissner corpuscles
Pacinian corpuscles

Front 90

What is the hypodermis composed of?

Back 90

loose CT w/ large numbers of adipose cells

Front 91

Which layer of the skin provides insulation, shock absorption, energy storage, and ability of skin to slide over joints?

Back 91

hypodermis

Front 92

Which layer of the skin provides the major blood vessels of the skin?

Back 92

hypodermis

Front 93

Many epidermal appendages extend down into the hypodermis and provide a source of ___ when the surface epidermis is destroyed by abrasion or burns.

Back 93

keratinocytes

Front 94

What do the epidermal appendages include?

Back 94

hair follicles, nails, and various glands

Front 95

Hair follicles are tubular invaginations of the (demis/epidermis/hypodermis) that give rise to hair.

Back 95

epidermis

Front 96

Hair is composed of ___ cells that have undergone a modified keratinization w/ the expression of specific keratin proteins that are highly crosslinked by ___ bond.

Back 96

dead epidermal
disulfide

Front 97

In human infants and children most hair (except for the scalp) is what type?

Back 97

vellus (fine)

Front 98

During puberty production of androgens causes much of the vellus hair to be converted to what type of hair?

Back 98

terminal (thick) hair

Front 99

In most mammals, hair functions in ____ and smooth muscle cells called ____ cause hair to stand on end for better insulation (goose pimples).

Back 99

thermoregulation
arrector pili

Front 100

In humans and in animal whiskers, hairs are well innervated and used for what?

Back 100

touch reception

Front 101

The hair follicle undergoes a active phase and then a resting phase during which the hair does what?

Back 101

falls out (eventually a new active phase is initiated and a new hair is started)

Front 102

What are found all over the body except hands and soles?

Back 102

sebaceous glands

Front 103

Where are sebaceous glands most prominent?

Back 103

face, neck and upper body

Front 104

What do sebaceous glands structure consists of?

Back 104

several acini that join in a short duct adn empty into hair follicles

Front 105

In sebaceous glands, the basal layer undifferentiated cells ____ as they move inward into the gland where they develop ___ containing droplets that grow and fuse. The cells autolyze and their contents become the secretion, ____ secretion.

Back 105

proliferate and differentiate
lipid
holocrine

Front 106

Sebaceous gland (holocrine) secretion is an oily material known as what and what is its function?

Back 106

sebum
subums function is unclear but it possibly works as an emollient for skin or hair, an anti-microbial, or as a pheromone.

Front 107

When do sebaceous glands begin to function appreciably?

Back 107

at puberty

Front 108

Where are eccrine sweat glands located and what is their primary function?

Back 108

at the lowermost part of the dermis over most of the body

function= cooling

Front 109

Eccrine sweat glands are simple coils of what kind of epithleium?
What kind of cells do eccrine sweat glands have and what do they do?

Back 109

cuboidal
dark cells-produce sialomucins
clear cells-produce water and electrolytes

Front 110

The final scretion produced by eccrine sweat glands is a (hypertonic/hypotonic) solution containing what?
How much do adults produce each day?

Back 110

-hypotonic (99% water)
-salts, lactate, and urea
-0.5 liters/day, ten times that if stressed

Front 111

What type of cells support and constrict the gland in response to cholinergic stimulation?

Back 111

Myoepithelial

Front 112

What is myoepithelial cell secretion controlled by?

Back 112

heat stress in most of body but is under emotional control in palms and soles

Front 113

Reabsorbtion of what occurs in sweat ducts?
What are the ducts composed of?

Back 113

-sodium and chloride ions
-2 layers of cuboidal epithelium

Front 114

People who have ___ have an impaired ion uptake resulting in sweat w/ a high salt content.

Back 114

cystic fibrosis (defective chloride channel)

Front 115

What type of sweat gland are simple tubular glands (sometimes coalesced) that empty into hair follicles in axillary and anogenital regions?

Back 115

apocrine sweat glands

Front 116

Where are apocrine cells located?
What are they composed of?
What are its ducts composed of?

Back 116

-lowermost part of dermis
-single layer of cuboidal epi
-2-3 cell layers

Front 117

How do apocrine glands produce secretions?

Back 117

by normal exocytosis

Front 118

What kind of stimulation do apocrine glands resond to that stimulates contraction of the myoepithelial cells?

Back 118

adrenergic or cholinergic

Front 119

What gland produces a secretion that is a mixture of proteins, carbs, and ferric ions that is odorless when secreted, but is acted upon by commensal bacteria?

Back 119

apocrine

Front 120

When do the apocrine glands begin to function?

What is their function in humans?

Back 120

at puberty

its unclear

Front 121

What are considered modified aprocrine sweat glands?

Back 121

mammary glands that produce milk and ceruminous glands that produce earwax

Front 122

What are products of modified epidermal keratinization and thus cmoposed of differentiated keratinocytes?

Back 122

nails

Front 123

Growth of nails occurs where?

Back 123

at the base in the nail matrix

Front 124

Cells grow (up/down) and push (mesially/distally) to force the growing nail outward.

Back 124

up, distally

Front 125

What is the epidermis called underlying most of the nail that does NOT contribute to the growth of the nail?

Back 125

nail bed