Integument

Question 1

Skin

Answer 1

largest organ and accounts for 7% of body weight
varies in thickness from 1.5-4.4 mm
divided into two distinct layers: epidermis and dermis

Question 2

Hypodermis

Answer 2

lies deep to dermis
also called superficial fascia
contains areolar and adipose connective tissue
anchors skin to underlying structures
helps insulate the body
hypodermis is area that can thicken dramatically with development of increased adipose tissue in people with obesity (e.g., adipose deposits in the abdominal wall)

Question 3

Functions of Skin and Hypodermis

Answer 3

protection: cushions organs and protects from bumps, chemicals, water loss, UV radiation
regulation of body temperature
excretion: urea, salts, and water lost through sweat
production of vitamin D in deep epidermis
sensory reception: keeps us aware of conditions at the body’s surface

Question 4

Embryologic Origin of Skin

Answer 4

epidermis: develops from embryonic ectoderm
dermis and hypodermis: develop from mesoderm
melanocytes: develop from neural crest cells which are of ectoderm origin

Question 5

Epidermis (layers)

Answer 5

stratum of corneum
stratum of lucidum (only in thick skin)
stratum granulosum
stratum spinosum
stratum basale (straum germinativum)
vitamin D3 (cholecalciferol) is synthesized from 7-dehydrocholesterol in the deep epidermis (stratum basale & stratum spinosum)

Question 6

Epidermis (cell types)

Answer 6

epidermis is deratinized stratified squamous epithelium with four distinct cells types:
keratinocytes: most common cell type in epidermis
melanocytes: location - basal layer; manufacture and secrete pigment
tactile epithelial cells: location - basal layer; attached to sensory nerve endings
dendritic cells: location - stratum spinosum; part of immune system; macrophage-like

Question 7

Keratinocytes vs. Keratocytes

Answer 7

keratinocytes: predominant cell type in skin epidermis
keratocytes: specialized fibroblasts in the cornea

Question 8

Keratinocytes in Epidermis (1)

Answer 8

most abundant cell type in epidermis
present in all epidermis layers
cells are tightly connected by a large number of desmosomes
produce antibodies and enzymes that detoxify chemicals that are exposed to our skin
produce keratin, a tough fibrous protein that gives skin epidermis its protective properties

Question 9

Keratinocytes in Epidermis (2)

Answer 9

arise from deepest layer of epidermis (stratum basale) from cells that undergo continuous mitosis
as these cells are pushed up by the production of new cells beneath them, they make keratin that fills their cytoplasm

Question 10

Keratinocytes in Epidermis (3)

Answer 10

by the time they reach the surface of the skin they are dead flat cells full of keratin
millions of these dead cells rub off from our skin every day
35-45 days is average time from the birth of a keratinocyte until it sloughs off of the exterior skin
we form an entirely new skin epidermis every 35-45 days
the average person sheds 40 pounds of skin flakes in a lifetime

Question 11

Keratinocytes in Epidermis (4)

Answer 11

where the skin experiences friction, both the cell production and keratin production are accelerated and the epidermis can become thick in this area
persistent friction can cause a significant thickening of the epidermis called a callus
short term severe friction can result in a blister of the skin which is the separation of the epidermis from the dermis by a fluid-filled pocket

Question 12

Stratum Basale (1)

Answer 12

deepest layer of epidermis
consists of the single row of cells, most of which are stem cells representing the youngest keratinocytes
cells actively divide
attached to underlying dermis
relies on capillaries in the underlying dermis for nutrients

Question 13

Stratum Basale (2)

Answer 13

tactile epithelial cells (Merkel cells) associated with sensory nerve endings are sparsely distributed among the keratinocytes in the stratum basale
melanocytes: spider-shaped melanocytes make up 10-25% of the cells in stratum basale
melanocytes make melanin and transport it through its spider-shaped cells process to nearby keratinocytes

Question 14

Stratum Basale (3)

Answer 14

melanin shields the cell nuclei from incoming UV radiation
darker skinned people have darker melanin and more pigment in each melanocyte
melanocytes respond to ultraviolet radiation by increasing production of melanin and increasing its transfer to keratinocytes, the protective response which results in a suntan

Question 15

Stratum Basale (4)

Answer 15

vitamin D3 (cholcalciferol) is a fat-soluble secosteroid formed from 7-dehydrocholesterol in deep epidermis (stratum basale and stratum spinosum) after exposure to ultraviolet B light
vitamin D is essential for uptake of calcium from the diet and formation of healthy bones as well as providing other health benefits

Question 16

Stratum Basale (5)

Answer 16

inverse relationship between level of melanin in keratinocytes and ability to produce vitamin D given the same UV exposure
humans with high levels of melanin tend to have originated from regions of the world (e.g., equatorial latitudes) where they have been exposed to large amounts of UV light, whereas humans with low levels of melanin tend to have originated from regions of the world exposed to lower levels of UV light

Question 17

Stratum Spinosum (1)

Answer 17

several cell layers of keratinocytes united by desmosomes
mitosis can occur in keratinocytes in this layer, however, less often that in the basal layer
relies on capillaries in the underlying dermis for nutrients

Question 18

Stratum Spinosum (2)

Answer 18

contains thick bundles of intermediate filaments (tonofilaments) which consist of the tension-resisting protein pre-keratin
contains star-shaped dendritic cells scattered among the keratinocytes
dendritic cells are part of the immune system and engulf foreign antigens that have invaded the epidermis and generate an immune response

Question 19

Stratum Graunulosum

Answer 19

consists of 1-5 layers of flattened keratinocytes
relieson capillaries in teh underlying dermis for nutrients
contains intermediate filaments (tonofilaments) which consists of the tension-resisting protein pre-keratin
contain keratohyaline granules which help form keratin
contain lamellated granules which contain a waterproofing glycolipid which is secreted into the extracellular space

Question 20

Stratum Lucidum

Answer 20

clear layer
occurs only in thick skin e.g., palms and soles
composed of a few rows of flat, dead keratinocytes which are like cells in the stratum corneum

Question 21

Stratum Corneum

Answer 21

horny layer
thick layer (multiple layers of cells) of dead keratinocytes
keratinocytes with thickened plasma membranes
dead keratinocytes are flat sacs filled with keratin
protects skin against abrasion and penetration
intercellular glycolipid keeps layer water proof
humans shed millions of dead keratinocytes off the outer surface of teh stratum corneum each day

Question 22

Skin Color

Answer 22

pigments which contribute to skin color:

melanin: most important pigment - made from tyrosine, differences both in the amount and type of melanin in humans
carotene: yellowish pigment from carrots and tomatoes can accumulate in stratum corneum and in the hypodermis
hemoglobin: skin with low amounts of melanin allows crimson color of blood to show through skin

Question 23

Albinism

Answer 23

people with albinism lack the enzyme necessary to make melanin

Question 24

Freckles

Answer 24

both freckles and moles are localized accumulations of melanin in the skin
freckles can develop as a result of repeated exposure to sunlight
with freckles, the increase in melanin is restricted to the basal layer of the epidermis
people with light complexions are more prone to freckle formation

Question 25

Moles

Answer 25

both freckles and moles are localized accumulations of melanin in the skin moles form when clusters of melanocytes are transformed into melanin-containing cells (nevus cells) these clusters of cells are both in the lower layer of the epidermis and in the top layers of the dermis many people are born with moles which are birth marks large moles (especially moles that are increasing in size) need to be followed by a dermatologist to rule out possibility of development of a melanoma

Question 26

Skin Cancer

Answer 26

basal cell carcinoma: lease malignant and most common squamous cell carcinoma: arises from keratinocytes of stratum spinosum melanoma: a cancer of melanocytes, the most dangerous type of skin cancer, melignant are asymmetrical with irregular borders and variable color

Question 27

Dermis (1)

Answer 27

second major layer of the skin strong, flexible connective tissue binds the entire body together like a body stocking corresponds to animal hides used to make leather the connective tissue proper contains fibroblasts, macrophages, mast cells, and white blood cells as well as collagen, elastic, and reticular fibers

Question 28

Dermis (2)

Answer 28

richly supplied with nerves richly supplied with blood vessels configured in two vascular plexuses the more superficial subpapillary vascular plexus is located just below the dermal papillae and supplies superficial dermal tissue, the dermal papillae, and the epidermis the deep dermal vascular plexus is configured between the hypodermis and the dermis and it nourishes the hypodermis and deep dermis blood running through the hands plays a role in temperature regulation

Question 29

Dermis (Layers) (3)

Answer 29

papillary layer reticular layer flexure lines

Question 30

Papillary Layer (Dermis) (1)

Answer 30

made up of areolar connective tissue proper dermal papillae are finger-like projections that interface with the overlying epidermis and increase surface area for exchange of gases, nutrients, and waste products

Question 31

Papillary Layer (Dermis) (2)

Answer 31

on the palms of the hands and the soles of the feet, dermal papillae lie atop larger mounds called dermal ridges which elevate overlying epidermis into epidermal ridges (friction ridges) which create finger prints

Question 32

Reticular Layer (Dermis)

Answer 32

makes up 80% of thickness in dermis dense irregular connective tissue thick bundles of interlacing collagen and elastic fibers give skin its stretch and recoil properties

Question 33

Reticular Layer - Cleavage Lines (Dermis)

Answer 33

separations or less dense regions between the collagen bundles form the cleavage lines or tension lines in the reticular dermis of the skin over the entire body the cleavage lines run longitudinally in the skin of the limbs and head and in circular patterns around the neck and trunk knowledge of cleavage lines is important to surgeons; when possible it is best of cut parallel cleavage lines

Question 34

Reticular Layer - Striae (Dermis)

Answer 34

stria are stretch marks extreme sustained stretching of the skin which can occur with obesit and pregnancy can tear the collagen in the reticular dermis resulting in linear patches on the skin called striae which are also known as stretch marks

Question 35

Flexure Lines (Dermis)

Answer 35

arise from the deep part of the dermis and result from the repeated folding of the skin such as in the palms of your hands and around joints e.g., at the wrist, fingers, and toes

Question 36

Skin Burns (Types)

Answer 36

first-degree burn: only epidermis is damaged second-degree burn: epidermis and upper part of dermis are damaged resulting in blister formation from separation of the epidermis from the dermis; typically heals with no scar formation third-degree burn: damages entire thickness of skin and produces permanent scar

Question 37

Tissue Response to Injury

Answer 37

inflammatory response: nonspecific, local response; limits damage to injury site immune response: takes longer to develop and very specific; destroys particular microorganisms at infection site

Question 38

Acute Inflammation (Tissue Response to Skin Injury)

Answer 38

``` heat redness swelling pain chemicals signal nearby blood vessels to dilate and histamine increases permeability of capillaries producing edema in region ```

Question 39

Edema (Tissue Response to Skin Injury)

Answer 39

accumulation of fluid in tissue as local blood vessels become more permeable helps dilute toxins secreted by pathogen brings white blood cells and antibodies from blood to fight infection brings nutrients from blood brings clotting factors from blood

Question 40

Repair (Skin)

Answer 40

inflammation: with blood clot in incised wound organization: clot is replaced by granulation tissue which restores blood supply fibrosis: proliferation of underlying scar tissue regeneration: fibrosed area matures and contracts and scar tissue is covered by a fully regenerated epithelium

Question 41

Sebaceous Glands

Answer 41

``` skin glands occur over entire body except palms and soles secrete sebum (an oily substance): simple branched alveolar glands, holocrine secretion (entire cell breaks up to form secretion), most are associated with a hair follicle functions of sebum: softens and lubricates hair and skin ```

Question 42

Sweat (Sudoiferous) Glands

Answer 42

widely distributed on body sweat is a blood filtrate 99% water with some salts contains traces of metabolic wastes including urea and ammonia humans typically produce 500 ml of sweat a day, however with heat exposure and intensive exercise the production can increase dramatically

Question 43

Eccrine Gland (Merocrine)

Answer 43

sweat gland | most numerous type of sweat gland, these produce true sweat and are present on palms, soles, and forehead

Question 44

Apocrine Gland (1)

Answer 44

large sweat glands confined to axillary, anal, and genital areas and their ducts open into hair follicles produce a special kind of odorless sweat which contain fats and proteins mixed in with sweat organic compounds in the sweat are broken down by bacteria on the skin resulting in a musky odor (body odor)

Question 45

Apocrine Gland (2)

Answer 45

secretions function as a pheromone and can contribute to mate attraction activity of these glands increases with sexual foreplay and around the time of ovulation in women signal information about a person's immune system, MHC (major histocompatibility complex) women tend to be more attracted to body odor scents of males with immune systems different than their own

Question 46

Other Specialized Sweat Glands

Answer 46

ceruminous glands: modified apocrine glands in external ear canal that produce cerumen (wax) mammary glands: specialized glands modified to secrete milk

Question 47

Nails

Answer 47

scale-like modification of epidermis made of hard, dead keratinized cells which do not flake off corresponds to the hoof or claw of other mammals nail rests on nail bed of deep epithelium nail matrix: actively growing part of a nail in thickened bed at proximal end of nail lunule: visible white crescent of proximal nail which represents the thickened nail matrix

Question 48

Hair (1)

Answer 48

flexible strand of dead, keratinized cells hard keratin - tough and durable hair roots are associated with sebaceous oil glands and arrector pili muscles cheif parts of a hair: root (imbedded in the skin) shaft (projects above skin's surface)

Question 49

Hair (2)

Answer 49

round cross-section of hair shaft is associated with straight hair oval cross-section of hair shaft is associated with wavy hair flattened cross-section of hair shaft is associated with kinky hair head lice has more difficulty attaching to hair with flattened cross-section compared to round cross-section

Question 50

Hair Color

Answer 50

hair pigment is made by melanocytes at the base of the hair follicle and is transferred into cells of the hair root different proportions of two types of melanin (black-brown and yellow-rust in color) combine to produce the common hair colors - black, brown, red, and blonde