BIOl 260 Exam 3

Integumentary system

The body's largest organ system, which includes the skin, hair, nails, and associated glands

Bursa

A sac filled with synovial fluid at a synovial joint, serving to facilitate muscle or joint action 

condyle

A rounded knob that articulates with another bone

Metaphysis is what?

The transitional zone, facing each marrow cavity 

Intramembranous ossification does what?

Plays an important role int he lifelong thickening, strengthening, and remodeling of the long bones

Osteogenesis (ossification): 

The process of forming bones 

• two methods: intramembranous and endochondral 

concentric lamellae 

Onlionlike layers of matrix concentrically arranged around a central (haversian) canal, connected with each other by canaliculi 

hydroxyapatite is 

A crystallized calcium phosphate salt 

Epidermal ridges

The upward waves of the epidermis that interlock with the downward waves of the dermis

• enhancing grip and sensitivity in the skin

Anagen vs catagen

Anagen is the active growth phase of hair follicles, while catagen is the transitional phase where hair growth slows and follicles shrink

Club hair vs telogen

Club hair refers to hair in the telogen phase, which is the resting phase before hair falls out, while telogen is the phase when hair has completed its growth cycle and is shed

What does stratum corneum produce that floats around as tiny white specks in the air?

Dander: dead cells that exfoliate from the epidermal surface 

Appositional growth 

The process of bone growth where new layers are added to the outer surface, increasing the width of the bone

Skin

Large organ composed of all 4 tissue types

Functions of the skin

• Resist trauma and infection s

• Act as barrier to prevent water loss, UV damage, chemical access

• Vitamin D synthesis 

• Provide sensory information about the surrounding environment 

• Thermoregulation 

• Nonverbal communication 

The epidermis is

the outermost layer of skin, serving as a protective barrier and comprising several sub-layers

• superficial portion of the skin

• composed of epithelial tissue

The dermis is

the layer of skin below the epidermis, containing connective tissue, blood vessels, hair follicles, and sensory receptors

• deeper layer of the skin

• primarily composed of connective tissue

Subcutaneous layer or hypodermis

Deep to the dermis

• not part of the skin

• consists of areolar and adipose tissue 

• fat storage, an area of pressure-sensing nerve endings 

• distinct boundary between dermis and hypodermis 

Stem cells

Divide to become keratinocytes

• only in stratum basale

Keratinocytes

Produce the protein keratin and take up melanin

• 80% of epidermal cells 

• in nearly all visible epidermal cells

Melanocytes

Pigment-producing cells containing melanin

• occur in stratum basale

• melanin absorbs damaging UV light 

Dendritic cells

Attack invaders, because they’re immune cells

• 5% of epidermal cells

• originate in the bone marrow but migrate to the epidermis and epithelia of the coral cavity, esophagus, and vagina

• found in stratum spinosum and stratum granulosum

Tactile cells

Interact with nerves to convey touch

• 2% of epidermal cells 

• found in basal layer

What are the cells of the epidermis?

• Stem cells

• Keratinocytes 

• Melanocytes

• Dendritic cells 

• Tactile cells

Layers (strata) of the epidermis?

Five layers (strata) 

• stratum corneum 

• stratum lucidum 

• stratum granulosum 

• stratum spinosum

• stratum basale

Stratum basale

Deepest layer of epidermis

• single layer of cuboidal to “low columnar” keratinocytes on the basement membrane 

• tactile cells, melanocytes, keratinocytes, & stem cells

• as stem cells divide, they produce keratinocytes that are pushed upward to replace lost cells

• site of most mitosis

• cells attach to each other & to basement membrane by desmosomes or hemi-desmosomes 

Stratum spinosum

8-10 layers of keratinocytes held together by desmosomes and tight junctions

• deepest cells of stratum spinosum can divide but upper ones have stopped

• as move superficial, increase keratin production, resulting in flattened shape

• contains dendritic cells throughout 

• during side preparation, cells shrink and appear spiny (where attached to other cells by desmosomes)

Stratum granulosom

3-5 layers of flat dying cells that show nuclear degeneration 

• transition between the deeper, metabolically active strata and the dead cells of the more superficial strata 

• contain lamellar granules that release lipids to repeal water 

• contain fark-staining keratohyalin granules (lamellar granules)  

Stratum lucidum

3-5 layers of clear, flat, dead cells 

• no nuclei or other organelles 

• contacts clear protein named eleidin 

• present only in the fingertips, palms of the hands, and soles of the feet (thick skin)

Stratum corneum

25 to 30 layers of flat dead cells filled with keratin and surrounded by lipids 

• barrier to light, heat, water, chemicals & bacteria 

• continuously shed (exfoliated) 

• constant exposure to friction will cause this layer to increase in depth 

  • forms a callus, an abnormal thickening of the epidermis 

How does keratinization and the growth of the epidermis occur?

• Stem cells divide to produce keratinocytes

• As keratinocytes are pushed up towards the surface, they fill with keratin and lamellar granules full of lipids 

How does stratum granulosum form the epidermal water barrier?

• Protein binds keratin in cytoskeleton into tough bundles 

• Envelope proteins just inside plasma membrane makes ‘indestructible’ sac around keratin bundles 

• lamellar granules release lipids that coat cell surfaces, waterproofing it 

• as keratinocytes are cut off from dermal blood supply, they die and leave behind only keratin bundles inside waterproofed sacs 

Thick skin

Has a significantly thicker stratum corneum compared to thin skin

• covers the palms, palmar surfaces of the digits, and soles

• features a stratum lucidum and thick epidermal ridges

• lacks hair follicles, arrector pili muscles, and sebaceous glands

• has more sweat glands than thin skin

Thin skin

Has a thinner stratum corneum compared to thick skin

• lacks a stratum lucidum and has fewer epidermal ridges

• covers all parts of the body except for the palms and palmar surfaces of the digits

• sparser distribution of sensory receptors than thick skin 

• contains sebaceous glands, hair follicles, and arrector pili muscles 

Basement membrane forms what?

A clear boundary between epidermis and dermis

Dermis layer is composed of what? Contains what?

Composed of collagen, elastic, and reticular fibers, fibroblasts, macrophages & fat cells

Contains hair follicles, glands, nerves, & blood vessels

Two major regions of the dermis

Papillary region

Reticular region

Papillary region 

The upper layer of the dermis, characterized by thin collagen fibers and dermal papillae that connect it to the epidermis

• allows mobility for leukocytes and other defenses against organisms

• vascular

Dermal papillae

Finger-like projections of dermis toward epidermal surface

• anchors epidermis to dermis 

• give rise to epidermal ridges (and fingerprints) 

Collagen and elastic fibers provide:

• Strength

• Extensibility (ability to stretch)

• Elasticity (ability to return to original shape after stretching)

Loose organization of tissue allows leukocytes and other defenses to: 

Allows them to act if invaders gets through epidermis 

Reticular region

The deeper layer of the dermis that contains dense irregular connective tissue, providing strength and elasticity

• It houses larger blood vessels, nerves, and hair follicles

• Much deeper and thicker than papillary layer, attaches to subcutaneous tissue 

• packed with oil glands, sweat gland ducts, clusters of adipocytes & hair follicles 

Stretch marks are:

Dermal collagen tears from extreme stretching that result in thin, discolored streaks on the skin

Blisters

Fluid-filled sacs that form between the epidermis and dermis, usually caused by friction, burns, or skin irritation to the dermal blood vessels

High vascular 

Tissue type with abundant blood vessels

• good site for injections 

Melanin

Produced in epidermis by melanocytes 

• UV in sunlight increases melanin production 

• Same number of melanocytes in everyone, but differing amounts of pigment produced 

Eumelanin vs Pheomelanin

Eumelanin: brown and black variations, causes tan, brown, and black tones in skin

Pheomelanin: reddish-yellow and results in these tones in skin of some Asian and indigenous American complexions 

Carotene in the dermis is?

A pigment that contributes to yellow-orange coloration of the skin, enhancing skin tone

• found in stratum corneum, dermis, and subcutaneous adipose 

Hemoglobin 

A protein in red blood cells that carries oxygen and gives blood its red color

Cyanosis

Blue or gray hue of skin and mucous membranes due to low oxygen in blood

Erythema

Abnormal redness of skin due to increased blood flow; common sign of infection and inflammation 

Pallor

Pale or ashen color when blood flow (or O2 in blood) is so low that white of dermal collagen shows through 

Albinism 

Genetic lack of melanin results in white hair and skin and blue-gray eyes 

Jaundice

Yellowing of skin and whites of eyes due to elevated bilirubin in blood; results from breakdown of RBCs 

Hematoma 

Mass of clotted blood showing through skin aka bruise or internal bleeding that occurs due to injury or trauma

Friction ridges

Markings on fingertips that cause us to leave fingerprints

Flexion lines (creases

lines on flexor surfaces of digits, palms, wrists, elbows, etc where skin folds along joints when folded

Freckles

Flat patch of tan to black aggregations of melanized keratinocytes

Mole (nevus) 

Elevated path of melanized skin, often with hair 

Hemangiomas (birthmarks)

Patches discolored by benign tumors of blood capillaries

Types of hemangiomas

Capillary hemangiomas (strawberry birthmarks) that develop a month after birth, most disappear by 5-6 years old

Cavernous hemangiomas which enlarge then regress, most gone by age 9 

Port-wine stain which can be large and remains for life 

How do skin accessor organ develop?

• Develop from the embryonic epidermis

• Cells sink inward during development to form hair, oil glands, sweat glands, and nails 

Hair (pili)

Filament of hard keratin that are present on most skin surfaces except the palms, palmar surfaces of the digits, soles, and plantar surfaces of the digits

Functions of the hair

• Prevents heat loss 

• decreases sunburn

• Guard hairs (vibrissae) guard nostrils and ear canals, eyelashes help protect eyes

• Touch receptors (hair root plexus) senses light touch 

• Facial expression (eyebrows)

• Identity 

Lanugo aka downy hair

Fine, unpigmented or lightly pigmented hair that appears on a fetus in the last 3 months of development

Vellus hair

Fine, pale or lightly pigmented hair that replaces lanugo by time of birth

• all of the hair of children except for eyebrows, lashes, and scal hair 

Terminal hair

Longer, coarser, more heavily pigmented hair that forms eyebrows, eyelashes, and covers scalp

• forms axillary and pubic hair after puberty

• dense facial hair and body hair after puberty

Shaft vs Root of the hair

Shaft: visible portion of hair at surface

Root: portion of hair below the surface

• penetrates the dermis and subcutaneous layer, ends at the hair bulb

Three layers of a hair

Medulla, cortex, cuticle

Hair follicle

Tube that contains the hair root

• external & internal root sheaths (epithelial)

• dermal (connective tissue) root sheath 

• base of follicle is a bulge containing stem cells for hair growth 

Arrector pili

Muscle that contracts to erect hair follicles and causes goosebumps

• contracts with cold or fear 

• forms goosebumps as hair is pulled vertically (piloerection)

Hair receptors

Nerve fibers in each follicle that detect hair movement 

Sebaceous (oil) glands

Glands associated with hair follicles that secrete sebum to lubricate and protect the hair and skin

What causes hair color?

Hair color is determined by the type and amount of melanin produced in the hair follicles

Graying hair is a result of?

Decline in melanin production

• it has air bubbles in the medullary shaft 

What does hair texture depend on?

Texture depends on the cross-sectional shape of the hair shaft

• straight hair is round 

• wavy is oval 

• tightly curled hair is fairly flat/ribbon-like 

What are the specialized exocrine glands that are found in the dermis?

• Sudiferous (sweat) glands 

• Sebaceous (oil) glands 

• Ceruminous (wax) glands 

• Mammary (milk) glands 

Eccrine sweat glands

Have an extensive distribution in most areas of skin

• secretory portion is in dermis with duct to surface

• exocytosis

• regulate body temperature through evaporation

• helps eliminate wastes such as urea 

Apocrine sweat glands

Limited in distribution to the skin of the axilla, pubis, and areolae (near nipple)

• produce a thicker, milky secretion that is often odorous and is triggered by emotional stress or hormonal changes

• secretory portion in dermis, duct that opens onto hair follicle 

• exocytosis 

• secretions are viscous (thick)

How does sweat move out of the skin?

Sweat moves out of the skin through glands via exocytosis, traveling through ducts to the skin surface, where it evaporates to regulate body temperature

Myoepithelial cells

Specialized cells located between the basal lamina and the epithelial cells of sweat glands that contract to help expel sweat from the gland into the duct

• They play a crucial role in the secretion process of both eccrine and apocrine sweat glands.

Insensible perspiration

The process of sweat evaporation from the skin that occurs without noticeable moisture, allowing for thermoregulation without conscious awareness

Diaphoresis 

Excessive sweating, often due to exertion, heat, or medical conditions that actually dampens the skin 

Secretory portion of gland is located where?

Holocrine secretion

Sebaceous glands are found in?

The dermis layer of the skin, associated with hair follicles, but absent in the palms and soles 

What does sebum do?

Sebum is an oily substance that contains cholesterol, proteins, fats, & salts

• moistens hairs 

• waterproofs and softens the skin 

• inhibits growth of bacteria and fungi 

What is acne?

Acne is a common skin condition that occurs when hair follicles become clogged with oil and dead skin cells

• hormones increase sebum secretion with puberty 

• sebum overproduction clogs hair follicle 

• bacteria proliferate in clog, causing inflammation 

Ceruminous glands 

Modified apocrine sweat glands that produce a waxy substance called cerumen (ear wax)

Where is cerumen found?

• Found int he external auditory (acoustic) meatus

• contains secretions of oil (sebaceous) and wax glands 

What is the function of ceruminous glands/cerumen

• Keep eardrum pliable

• Waterproof ear canal

• Kill bacteria 

• Coats guard hairs of ear canal to make them sticky so they trap foreign particles better and prevent infections

Mammary gland

Modified apocrine sweat glands that produce milk during lactation 

• growth triggered by hormones, so all sexes can lactate if certain hormones are present

• fluid is channeled through ducts to a nipple 

Breast

Tissue of chest found along pectoral region

• present in all sexes

• contains only small traces of mammary gland under standard circumstances, growth of gland in response to hormones 

What is the structure of nails?

Nails are composed of keratinized epithelial cells, forming a hard surface that protects the tips of fingers and toes

Why is the lunule white?

Due to thickened stratum basale

Types of skin cancers

Basal cell carcinoma: impacts mitotically active cells in stratum basal

Melanoma: starts in melanocytes near stratum basal

Squamous cell carcinoma: originates in the stratum spinosum 

Metastasis

Process where cancer cells spread to other organs or regions in the body

How to diagnose melanoma?

ABCDE mnemonic 

ABCDE mnemonic

Asymmetry - the two sides are not symmetrical

Borders - the edges are irregular in shape 

Color - the color is varied shades of brown or black 

Diameter - it is larger than 6 mm (0.24 in) 

Evolving - its shape has changes

What do you use to diagnose more serious form, nodular melanoma?

Elevated - it is raised on the skin surface

Firm - it feels hard to the touch

Growing - it is getting larger 

Eczema

Allergic reaction manifesting as itchy dry patches of skin

• resembles a rash