Biology 110

Study Guide Exam 2

 

Chapter 5: The Integumentary System

 

The Skin (Integument): composed of 2 regions:

-       Epidermis: outermost layer composed of epithelial cells

-       Dermis: underlying layer composed of fibrous connective tissue; vascularized

 

Epidermis: keratinized stratified squamous epithelium

-       Layers of Epidermis:

o      Stratum Basale: basal layer; deepest epidermal layer firmly attached to dermis

       single layer of cells; cell division produces new keratinocytes for all layers

       dead cells hardened by keratin (keratinized)

       protects skin with keratin & thick plasma membranes; glycolipids prevent water loss

 

-       Cell types in epidermis:

o      keratinocytes: produce the fibrous protein keratin

       tightly connected by desmosomes

       outermost cells dead & keratinized; lifespan of 25-45 days

       thick skin has accelerated cell division & keratinization

o      Langerhans' cells (epidermal dendritic cells): macrophages; part of immune system - kill microbes

       produced in bone marrow; migrate to epidermis & form network around keratinocytes

o      melanocytes: spider-shaped cells that produce the pigment melanin

       located in deepest layer of epidermis; transfer melanin to keratinocytes

       melanin granules protect the cell nucleus from UV radiation

 

Skin Color: dictated by 3 pigments: melanin, carotene, & hemoglobin

-       melanin: passed from melanocytes to basal keratinocytes

o      melanin color ranges from yellow to reddish-brown to black

o      freckles & pigmented moles are due to local melanin accumulations

-       carotene: yellow-orange pigment found in plants (carrots...)

o      accumulates in stratum corneum & dermis; gives skin yellowish color

-       hemoglobin: oxygenated hemoglobin in dermal capillaries gives fair skin a pinkish color

 

Dermis: contains both loose & fibrous connective tissue

-       collagen fibers: flexible but resist stretching (prevent skin from being torn)

-       elastic fibers: stretch to allow movement of underlying muscles & joints

-       dermal papillae: projections that indent into & anchor epidermis

-       dermal ridges on palms of hand & soles of feet form epidermal ridges

o      increase friction for better grip

o      genetically determined pattern of ridges; leaves fingerprint

-       rich supply of blood vessels nourishing skin

o      increased blood flow: blushing; reduced blood flow: cyanosis

o      restricted blood flow (in bedridden) can lead to decubitus ulcers (bedsores)

-       accessory structures: hair follicles, nails, oil & sweat (sudoriferous) glands

-       sensory nerve fibers: take nerve impulses to & from accessory structures

 

Subcutaneous Layer (Hypodermis): layer just deep to the dermis

-       mostly adipose (fat) tissue with some other loose connective tissue

-       adipose tissue serves as reserve energy store

-       insulates, absorbs shocks, & anchors skin loosely to muscles

 

Accessory Structures of Skin:

Hair & hair follicles:

-       hair is flexible strands of mostly dead, keratinized cells

-       hair is found on all body parts except the palms, soles, lips, nipples & portions of external reproductive organs

o      puberty stimulates new hair growth (axillary & pelvic regions in both sexes, & in several other body regions in males)

-       hair follicle: extends from epidermal surface to dermis

o      cells at base of follicle continually divide, pushing older cells toward surface & away from blood vessels (nourishment) - cells become keratinized & eventually die toward top of follicle

-       hair has root within follicle & shaft extending beyond skin

-       melanin from melanocytes at base of follicle produce color

-       alopecia: hair loss brought on by aging & hormones

-       each follicle has one or more sebaceous (oil) glands that empty into follicle

-       arrector pili muscle: smooth muscle bundle that contracts to raise hair

 

Nails: scalelike epidermal modifications at dorsal surface of distal region of fingers & toes

-       nail root cells produce new growth - cells become keratinized as they grow out over nail bed

-       nail body: visible portion of nail

-       cuticle: fold of skin over nail root

-       blood in dermal blood vessels beneath nail give pink color to nails

-       lunula: whitish half moon shaped base resulting from thicker skin in the area

 

Sweat (sudoriferous) glands: eccrine & apocrine

-       eccrine sweat glands: far more numerous - most abundant on palms of hands, soles of feet & forehead

o      ducts opens into pore at skin surface

o      secrete sweat: 99% water with salts, vitamin C, antibodies, metabolic wastes (form of excretion)

o      sweat prevents overheating; regulated by sympathetic division of autonomic nervous system

 

-       apocrine sweat glands: mostly confined to axillary & anogenital regions

o      ducts empty into hair follicles

o      in addition to components of sweat, secretion contains lipid & proteins

 

-       ceruminous glands: modified apocrine glands in the external ear canal

o      secrete cerumen (earwax); deters insects & blocks foreign material

 

Sebaceous (oil) glands: located all over body except palms of hand & soles of feet

-       secrete sebum (rich in oils) into hair follicle (or pore)... bacteriocidal; lubricates hair & skin

-       inflammation/infection can lead to acne; overactivity leads to seborrhea

 

Mammary glands: modified sweat glands in breasts

-       lobules within breast lobes contain numerous alveoli

-       after childbirth, alveoli secrete milk, which enters a duct leading to nipple

 

Functions of Skin:

Protection: the skin forms a protective covering over body, guarding it from physical trauma

Synthesis of Vitamin D: UV light (sunlight) assists skin cells in producing vitamin D

Sensory Reception & Communication: specialized nerve endings in dermis are sensory receptors for touch, pressure. Pain, hot & cold

Body Temperature Regulation: some energy from breaking down ATP in chemical reactions is released as heat

-       hypothalamus in brain has homeostatic mechanism for regulation of body temperature (36.2-37.7°C)

-       skin regulates body temperature:

o      blood vessels in dermis can constrict to receive less blood or dilate to receive more blood

o      sweat glands can secrete sweat to cool body

-       hyperthermia: body temperature above normal (regulatory mechanisms overcome)

o      heat exhaustion: individual becomes tired; may be accompanied by headaches, vomiting

o      heat stroke: elevated temperature (up to 43°C or 110°F); dizziness, confusion & delusions may occur

       important to cool body immediately: person is immersed in cool water, & fluids given to restore water & salt balance

o      fever: elevated body temperature brought on by illness

       bacteria release pyrogens that reset the thermostat at higher temperature (accompanied by chills)

       thermostat reset when infection is cleared & fever breaks

-       hypothermia: body temperature below normal (regulatory mechanisms overcome)

o      body temperature 90-95°C: uncontrollable shivering, incoherent speech & lack of coordination

o      body temperature 80-90°C: pulse rate slows, hallucinations occur, person loses consciousness

 

Disorders of skin:

-       athlete's foot: caused by fungal infection, usually in skin of toes, sole of foot

-       eczema & psoriasis: rapid cell division in skin cells, resulting in scaling, itching

o      eczema: caused by sensitivity to chemicals (detergents), fabrics, heat

o      psoriasis: chronic autoimmune disorder, may be hereditary (inherited); results in reddish (scaly) patches

 
-       Skin cancer

o      melanoma: malignant skin cancer; starts in melanocytes

       characterized by unusual moles that are linked to sun exposure

       may metastasize or spread to nearby organs or tissues

o      basal cell carcinoma: most common skin cancer; UV exposure causes basal cells of epidermis to overgrow, forming tumor

o      squamous cell carcinoma: tumors form in cells of lower layers of epidermis

       more likely to metastasize than basal cell carcinoma

 

-       Burns

o      first-degree: only epidermis is destroyed

o      second-degree: entire epidermis & part of dermis is destroyed

o      third-degree: full thickness (epidermis & dermis) is destroyed

o      fourth degree: tissue down to bone is destroyed

 

Wound Healing:

-       if blood vessel is torn, blood clots at vessel tear & forms scab

-       basal layer of epidermis produces new cells at rapid rate to replace damaged cells

-       if wound is deep, scar tissue may form (many collagen fibers add strength, but few cells present)

 

Effects of Aging: epidermis maintains thickness, but there is decreased turnover of skin cells; epidermis becomes less firmly attached to dermis; adipose tissue declines

-       decline in numbers of: blood vessels, sweat glands, hair follicles, sebaceous glands & melanocytes

-       UV radiation can cause rough skin, unusual pigmentation, wrinkles

 

 

 

 

 

 

 

Chapter 6: The Skeletal System

 

Classification of bone:

Human Skeleton: 206 named bones

-       Axial skeleton: 80 bones... bones of skull, vertebral column & rib cage

-       Appendicular skeleton: 126 bones... bones of upper & lower limbs, pectoral & pelvic girdles

 

Functions of bones:

-       supports body & its organs against pull of gravity

-       protects soft body parts

-       blood cell formation (hematopoiesis): in some red bone marrow

-       mineral storage: calcium salts (calcium phosphate)

-       bones (particularly those of arms & legs) provide sites for muscle attachment & permit flexible movement

 

Bone structure:

Gross anatomy of long bones:

-       compact bone: dense outer layer of bone

-       spongy bone (cancellous bone): trabeculae - needle-like or flat pieces internal to compact bone; spaces between trabeculae filled with red or yellow bone marrow

-       diaphysis (shaft): forms long axis of bone; thick collar of compact bone surrounding medullary (marrow) cavity

o      In adults, marrow cavity contains fat - yellow bone marrow cavity

-       epiphyses: ends of bone; often more expanded than diaphysis; outer compact & internal spongy bone

o      Joint surfaces covered by articular cartilage

o      Epiphyseal line: between diaphysis & each epiphysis - remnant of epiphyseal plate (site of bone growth during childhood)

-       Periosteum: membrane that covers entire surface of bone except joint surfaces

o      continuous with tendons & ligaments that anchor bones

o      contains blood vessels that enter bones & deliver nutrients to bone cells

-       Endosteum: inner membrane covers trabeculae of spongy bone & canals of compact bone; contains osteoblasts & osteoclasts

 

Hematopoietic tissue in bones:

-       Hematopoiesis occurs in red marrow (in cavities of spongy bone of long bones & diploe of flat bones)

-       In infants, medullary cavity & all spongy bone have red bone marrow

-       In adults, red bone marrow in the head of the femur & humerus, & diploe of flat bones & some irregular bones (hip bone)

-       During anemia (blood cell deficiency), yellow marrow can revert to red marrow

 

Microscopic structure of bone:

Compact bone (lamellar bone): units called osteons or Haversian systems

-       within each cylnder (osteon) is tubes (concentric circles) of bone matrix (lamellae)

-       central (Haversian) canal: runs through center of osteon; carries blood vessels & nerve fibers

-       osteocytes: bone cells in small cavities called lacunae

-       canaliculi: connect lacunae to each other & central canal

-       lacunae separated by bone matrix containing collagen fibers & mineral deposits (calcium phosphate)

 

 

Spongy bone: trabeculae... a few cell layers of irregularly arranged lamellae & osteocytes connected by canaliculi

-       no osteons; nutrients delivered by capillaries in endosteum

 

Bone development:

-       osteogenesis (ossification)... in infants & adolescents for skeleton formation & growth; in adults for bone remodeling

-       most of skeleton is cartilage model (cartilage shaped like future bones) during prenatal development

-       cartilage models converted to bone when calcium salts deposited in bone matrix, first by cartilage cells & later by osteoblasts (bone-forming cells)

-       endochondral ossification: bone forms by replacing hyaline cartilage

-       intramembranous ossification: membrane bone forms from fibrous membrane

-       endochondral ossification:

o      primary ossification center in middle of bone

o      bone collar forms around diaphysis of cartilage

o      central cartilage calcifies & cavitates

o      diaphysis elongates & medullary cavity forms

o      ossification of epiphyses at secondary ossification centers

o      epiphyseal (growth) plates form at junction of diaphysis & epiphysis

 

Bone Remodeling: for bone growth, or to replace injured bone

-       osteoclasts (giant multinucleate cells from same stem cells that differentiate into macrophages) secrete lysosomal enzymes to digest organic matrix & acids to release calcium into solution

-       osteoclast damage repaired by osteoblasts

-       osteoblasts take calcium from blood for new bone matrix

-       some osteoblasts within new matrix become osteocytes (bone cells)

-       requires calcium & phosphate & enzyme alkaline phosphatase

 

Repair of fractures:

Fracture types:

-       displaced (ends out of alignment) & nondisplaced fractures

-       complete (bone broken through) & incomplete fractures

-       linear (along axis) & transverse (perpendicular to axis) fractures

-       open (compound, breaks skin) & closed (simple) fractures

 

Reduction: realignment of broken bone ends

-       closed reduction: bones coaxed into position by physician (or someone)

-       open reduction: bone ends are secured together by pins or wires

-       hematoma (mass of clotted blood) forms in space between broken bone as blood escapes from injured blood vessels

-       fibrocartilage callus forms to fill space between broken ends of bone (collagen fibers tie bone ends together)

-       bony callus forms from fibrocartilage callus as osteoblasts produce spongy bone to join bone ends together

-       bone remodeling: osteoblasts build new compact bone at periphery & form medullary cavity from spongy bone

 

Axial Skeleton: 80 bones

-       consists of bones arranged along (longitudinal) axis of body

-       includes: skull bones, auditory ossicles (ear bones), hyoid bone, ribs, sternum (breastbone) & vertebral column (backbone)

 

Skull: 22 bones

-       cranial bones: 8 bones which enclose & protect the brain

o      frontal bone: forms forehead & part of nose & orbits

o      parietal bones (2): posterior to frontal bone; form roof & sides of cranium

o      temporal bones (2): inferior to parietal bones; help form base of cranium

       external auditory meatus: canal to middle ear

       mandibular fossa: articulates with mandible

       mastoid process: point of attachment for neck muscle (sternocleidomastoid)

       styloid process: point of attachment for muscles of tongue & larynx

       zygomatic process: helps form cheekbone

o      occipital bone: forms dorsal part of skull & base of cranium

       foramen magnum: large opening where spinal cord joins brain

       occipital condyles: articulate with 1st cervical vertebra

o      sphenoid bone: forms sides & base of cranium & part of orbits

       articulates with all other cranial bones

       sella turcica: depression that houses pituitary gland of brain

o      ethmoid bone: forms part or orbits & nasal cavity

       perpendicular plate: upper nasal septum

       cribriform plate: contains opening for olfactory (smell) nerve fibers

       crista galli: ridge at base of cranial cavity for meninges attachment

       superior & middle nasal conchae: projections in mucous membranes of nasal cavity for filtering & warming air

 

-       Facial Bones: 14 bones

o      nasal bones (2): form bridge of nose (most of outer nose is cartilage)

o      maxillae (2): form upper jaw

       palatine process: forms anterior portion of hard palate (roof of mouth)

o      zygomatic bones (2): form sides of orbits & cheekbones

       temporal process: joins zygomatic process of temporal bone

o      lacrimal bones (2): at medial walls of orbits (eye sockets)

       lacrimal fossa: has opening for tears

o      palatine bones (2): form posterior portion of hard palate

o      inferior nasal conchae (2): projections in mucous membranes of nasal cavity for filtering & warming air (like nasal conchae of ethmoid bone)

o      vomer: forms lower part of nasal septum (joins with perpendicular plate of ethmoid bone)

o      mandible: lower jaw