EXAM 2

What is the largest organ in the body?

Skin.

what filaments cause the cells to flatten in stratum spinosum?

keratin filaments

About what percentage of body weight does skin make up?

About 15%.

what cells alert the immune system to foregin invaders?

Dendritic (langerhans) cells

What two tissue layers make up the skin?

The epidermis (outer layer of keratinized stratified squamous epithelium) and the dermis (deeper connective tissue layer).

what are dendritic (langerhans) cells?

modified macrophages from bone marrow

What does the skin rest on?

The subcutaneous layer, also called the hypodermis.

What stratum layer forms a protein-lipid (epidermal water barrier)

the stratum granulosum

What structures does the skin contain?

Hair follicles, sebaceous glands, and sweat glands.

what does the epidermal water barrier do?

• waterproofs the skin

• prevents dehydration

• cells above die because they are cut off from nutrients

What is the normal thickness of skin?

About 1–2 mm.

What stratum has 3-5 layers of granule and vesicle containing keratinocytes?

stratum granulosum

How thin is skin in the eyelids?

About 0.5 mm.

which stratum layer has a thin translucent layer thats in THICK skin only

stratum lucidum

How thick can skin be on the palms and soles?

About 6 mm.

Does stratum lucidum contain any nuclei or organelles?

no

What structures are absent from thick skin on the palms and soles?

Hair follicles and sebaceous glands.

Cells are filled with ____ in stratum lucidum

eleidin (lipid-rich protein)

The epidermis is _____ to the dermis.

Superficial.

How many layers does stratum corneum contain?

up to 30 layers

What type of tissue makes up the epidermis?

Keratinized stratified squamous epithelium.

What kind of cells are in stratum corneum?

dead, scaly keratinized cells which surface ones flake off (exfoliation)

What is found at the surface of the epidermis?

Dead cells and keratin.

Which stratum layer is resistant to abrasion, penetration, and water loss

stratum corneum

What is the purpose of the dead cells at the epidermal surface?

They protect the living cells underneath.

Is the epidermis avascular or vascular?

Avascular; it has no blood vessels.

Does the epidermis have abundant or sparse nerve endings?

Sparse nerve endings.

How many layers does the epidermis contain?

Thick skin has five layers; thin skin has four because it lacks the stratum lucidum.

How long does it take an epidermal cell to migrate from the deepest layer to the surface?

About 30–40 days.

What are the epidermal layers from superficial to deep?

Stratum corneum, stratum lucidum, stratum granulosum, stratum spinosum, and stratum basale.

What mnemonic helps remember the epidermal layers from superficial to deep?

Cute Little Geese Steal Bread.

In which epidermal layer does most mitosis occur?

The stratum basale; some dividing cells also occur in the lower stratum spinosum.

What is the deepest layer of the epidermis?

The stratum basale.

How are cells arranged in the stratum basale?

A single layer of cuboidal or low columnar cells resting on the basement membrane.

Where does the stratum basale receive nutrients?

From the underlying connective tissue of the dermis.

What four cell types are found in the stratum basale?

Keratinocyte stem cells, basal keratinocytes, melanocytes, and tactile epithelial (Merkel) cells.

Which epidermal cells divide rapidly?

Keratinocyte stem cells.

when does epidermal mitosis mainly occur?

At night in the stratum basale

Which cells produce the tough, fibrous protein keratin?

Keratinocytes.

Which cells produce the protective pigment melanin?

Melanocytes.

Do people of different skin colors have approximately the same number of melanocytes?

Yes; differences in skin color mainly reflect melanin production, type, distribution, and breakdown.

How does melanin protect keratinocytes?

Keratinocytes take up melanin, which shades their nuclei from ultraviolet radiation.

Which type of melanin is black or brown?

Eumelanin.

Which type of melanin is reddish or yellow?

Pheomelanin.

Which epidermal cells sense touch?

Merkel cells, also called tactile epithelial cells.

What are Merkel cells attached to?

A sensory nerve ending in the dermis

How thick is the dermis?

0.2mm to 4mm

The dermis contains _____ connective tissue

fibrous connective tissue; composed mainly of collagen with some elastic/reticular fibers

Does the dermis contain blood vessels?

yes; its vascular

what accessory structures does the dermis contain?

1. hair follicles

2. sebaceous glands

3. sweat glands

4. nail roots

5. nerve endings

Dermal papillae do what in the dermis?

they are upward extensions of the dermis into the epidermis that form the ridges of the fingerprints

pilo erector muscles are in the dermis and do what?

make your hairs stand up; also smooth muscle

the papillary layer is __ of the dermis

20%

the reticular layer is ___ of the dermis

80%

What are the two dermal layers?

1. Papillary layer

2. Reticular layer

What is the papillary layer?

• loosely organized areolar tissue

• allows for motility of white blood cells

What is the Reticular layer?

• deepest 4/5

• dense irregular connective tissue

• thick collagen (responsible for stretch marks)

• adipocytes

• 80% of the dermis

What is the study of joint structure?

arthrology

what is the study of musculoskeletal movement

kinesiology

which fibers hold bones together in a fibrous joint?

collagen fibers

what cartilage is found between the bones of the symphysis joints?

fibrocartilage

what cartilage is found lining the joint surfaces of synovial joints?

hyaline cartilage

what are immovable joints called?

synostosis or bony joints

how are synostosis or bony joints formed?

formed by ossification of fibrous or cartilaginous joints

what kind of joints are produced by embryonic bones that fuse seamlessly into one adult bone?

synostosis or bony joints

which fibrous joints have short fibers and little movement

sutures and gomphoses joints

which fibrous joints have long fibers and mobile movement

syndesmoses joints

what are sutures?

• fibrous joints

• immobile or slightly mobile movement

• attach two bones on the skull together

what are serrate sutures?

wavy lines

what are lap (squamous) sutures?

overlapping beveled (slant) edges

what are plane (butt) sutures?

straight non-overlapping edges

ex: roof of mouth

how are syndesmoses joints held together

by a bond of long collagen fibers

which fibrous joint contains an interosseous membrane

syndesmoses joints

what holds the ends of an amphiarthodial (limited movement) joint together?

cartilage

the epiphyseal plate in a growing bone is called a _________ joint

synchondrosis

how are synchrondosis joints formed?

by hyaline cartilage

which joints are separated by a narrow, fluid-filled encapsulated space?

synovial joints (freely movable joints)

the pubic symphysis is a ______ joint

cartilaginous

what are tendons made out of?

tough collagenous connective tissue

what do ligaments do?

ligaments connect bone to another bone

what is a bursa?

a sac filled with synovial fluid at a synovial joint that facilitates muscles or joint action

what is a tendon sheath?

a bursa wrapped around a tendon which prevents friciton

What does the hypodermis do?

• binds skin to underlying tissue

• contains more adipose (fat) than dermis

is the hypodermis thicker in men or women?

8% thicker in women

where is subcutaneous fat distributed in men?

1. abdomen

2. thighs

3. hips

4. gluteal region

where is subcutaneous fat distributed in women?

1. breasts

2. abdomen

3. thighs

4. posterior neck

5. lateral parts of the humerus

6. gluteal region

What is hemoglobin?

red pigment of red blood cells

• visible through dermal collagen fibers

what is carotene?

yellow pigment from diet

• concentrates in stratum corneum and subcutaneous fat

what is melanin?

pigment produced by melanocytes (hereditary)

• pigment synthesis stimulated by UV radiation from sunlight

• produces yellow, brown, black and reddish hues

• concentrated in moles and freckles

what is cyanosis?

blueness resulting from deficiency of oxygen in the circulating blood (cold weather)

what is erythema?

redness due to dilated cutaneous vessels

what is flushing?

anger, sunburn, embarassment

what is jaundice?

yellowing of skin and sclera

• due to excess bilirubin in blood (liver disease)

• golden-brown color

• bronzing

• related to addison disease

what is addison disease?

deficiency of glucocorticoid hormone

what is pallor?

pale color from lack of blood flow

what is albinism?

genetic lack of melanin

what is a hematoma?

a bruise (visible clotted blood)

what are hemangiomas?

• birthmarks

• discolored skin caused by benign tumors of dermal blood capillaries

• strawberry birthmarks disappear in childhood

• port wine birthmarks last for life

what are freckles?

flat aggregation of melanocytes

• from heredity and sun exposure

what are moles

elevated melanized skin

• sometimes with hair, usually benign