Biology 210
Study Notes Exam 2
Chapter 4: Tissues: The Living Fabric
Cell-Cell Junctions & Communication:
- Adhesion junctions (desmosomes): cytoplasmic plaques within two cells are joined by intercellular filaments
- Tight junctions: plasma membrane proteins of two adjacent cells attach, producing a zipperlike fastening
· important in forming barriers to neighboring cells of a different type (e.g.: digestive tract cells with very low pH)
- Gap junctions: Channel proteins from 2 adjacent cells join, forming a continuous channel between the 2 cells
· important in muscle cell communication
Epithelial Tissue (epithelium): a sheet of cells that lines a body cavity or covers a body surface
- covering & lining epithelium: skin & lining of body cavities
- glandular epithelium: forms glands
- many functions: protection, absorption, secretion, excretion, filtration, sensory reception
Characteristics of Epithelial Tissue:
- cellularity
- specialized contacts
- polarity
- support by connective tissue
- avascular but innervated
- capable of regeneration
Classification of Epithelia:
- squamous (flattened), cuboidal (cube-shaped), & columnar (column-shaped) cells
- simple (1 layer) or stratified (multiple layers)
Simple Squamous Epithelial Tissue: single layer of flattened cells with disc-shaped nuclei & little cytoplasm
- locations: in kidney glomeruli, air sacs of lungs, heart lining, blood vessels & lymphatic vessels, lining of ventral body cavity
- functions: diffusion & filtration; secretes lubricating substances in serosae
Simple Cuboidal Epithelial Tissue: single layer of cube-shaped cells with large spherical nuclei; often seen in circular pattern when cut in cross section
- locations: in kidney tubules, ducts of small glands, ovary surface
- functions: secretion & absorption
Simple Columnar Epithelial Tissue: single layer of column-shaped cells with oval nuclei; some have cilia or microvilli; may include goblet cells
- locations: nonciliated in most of digestive tract, gallbladder & excretory ducts of some glands; ciliated in small bronchi, some regions of uterus
- functions: absorption, secretion of mucus, enzymes...; ciliated propels mucus, reproductive cells
Pseudostratified Columnar Epithelial Tissue: single layer of mostly column-shaped cells with different heights (some don't reach apical surface) & nuclei at different levels; some have cilia; may include goblet cells
- locations: nonciliated in male sperm-carrying ducts & ducts of large glands; ciliated type lines trachea & most of upper respiratory tract
- functions: secretion & propulsion of mucus
Stratified Squamous Epithelial Tissue: multiple layers; basal layer cuboidal or columnar - carry out metabolism & mitosis; outer layers are keratinized
- locations: nonkeratinized in most of digestive tract, gallbladder & excretory ducts of some glands; keratinized in epidermis of skin
- functions: protects underlying tissues
Stratified Columnar Epithelial Tissue: several layers - basal layer usually cuboidal
- locations: male urethra & some large ducts of glands
- functions: protection, secretion
Transitional Epithelial Tissue: several layers - basal layer cuboidal or columnar; surface cells dome-shaped or squamous-like (depending on stretch)
- locations: ureters, bladder & part of urethra
- functions: stretches & distends urinary organ
Glandular Epithelial Tissue
Gland: 1 or more cells that produce & secrete a specific product
- unicellular or multicellular
Endocrine glands: release product into extracellular space
- ductless glands... eventually lose their ducts
Exocrine glands: release product to an epithelial surface (to surface of skin or body cavity)
-
includes mucus, sweat, oil, & salivary glands, and
liver & pancreas
-
goblet cell:
unicellular exocrine gland
·
located in intestinal & respiratory tracts
·
produce mucus
containing the glycoprotein mucin
-
multicellular exocrine glands
· tubular: secretory cells form tubes
· alveolar (acinar): secretory cells form small sacs
· tubuloalveolar: both types
· merocrine glands: secrete product by exocytosis
· apocrine gland: loses small portions of gland during secretion
· holocrine glands: accumulate product until gland ruptures
Connective Tissue: most abundant primary tissue
- all types arise from embryonic mesenchyme
- range of vascularity
- extracellular matrix (collagen or elastin fibers; calcium phosphate (bone)
- ground substance: fills space between cells & contains fibers
·
composed of interstitial fluid, cell adhesion proteins & proteoglycans
·
proteoglycans: protein core attached to glycosaminoglycans (GAGs)
§
common GAGs include chondroitin & keratin
sulfates and hyaluronic acid
§
GAGs form large aggregates that trap water to increase viscosity of ground substance
Connective Tissue Fibers:
- collagen: thick fibers (of collagen protein); provide tensile strength (resist tension); known as white fibers
- elastic: thin fibers made of elastin protein; stretch easily; found in skin, lungs & blood vessel walls; known as yellow fibers
- reticular: very thin collagenous fibers; branch extensively & lend delicate support (lymphoid tissues); also found in basement membranes & around capillaries
Connective Tissue Cells:
-
undifferentiated cells are called blast cells
· fibroblast (many types of connective tissue)
· chondroblast (cartilage)
· osteoblast (bone)
· hematopoietic stem cell (blood)
-
after secretion of matrix & fibers of tissue, blast
cells differentiate to mature cells
·
chondrocytes & osteocytes
· white blood cells, mast cells, macrophages (blood,...)
Connective Tissue Types:
Embryonic Connective Tissue: gel-like ground substance; star-shaped mesenchymal cells
- location: embryo
- functions: gives rise to all connective tissue types
Areolar Connective Tissue: gel-like matrix with all 3 fiber types; fibroblasts, mast cells, macrophages & some white blood cells
- location: under many epithelia (forms lamina propria); around organs & capillaries
- functions: cushions organs; many immune cells regulate immunity
Adipose Connective Tissue: closely packed adipocytes (fat cells with large fat droplet)
- location: under skin, around kidneys & eyeballs, within abdomen, breasts
- functions: cushions organs; reserve food fuel, insulation
Reticular Connective Tissue: reticular fiber network in loose ground substance; reticular cells
- location: lymphoid organs
- functions: internal skeleton for support of other cell types
Dense Regular Connective Tissue: dense (primarily) parallel collagen fibers, few elastin fibers; fibroblasts
- location: tendons, ligaments, aponeuroses
- functions: attaches muscles to bone & other muscles, attaches bones to bones; withstands high stress
Dense Irregular Connective Tissue: irregular shaped collagen fibers, few elastin fibers; fibroblasts
- location: dermis of skin, digestive submucosa, fibrous capsules of organs & joints
- functions: withstands tension, adds structural strength
Cartilage: mostly water; no blood vessels or nerves
- surrounded by a layer of dense irregular connective tissue - the perichondrium, which contains blood vessels
- contains chondrocytes in lacunae, ground substance & fibers
- ground substance contains abundant glycosaminoglycans chondroitin sulfate & hyaluronic acid
-
3 types: hyaline,
elastic & fibrocartilage
Hyaline Cartilage: amorphous firm matrix; collagen fibers form glassy (invisible) network; chondrocytes in lacunae
- location: embryonic skeleton, covers long bones in joints, costal cartilage of ribs, cartilage of nose, trachea & larynx
- functions: support, cushioning, resists stress
Elastic Cartilage: similar to hyaline cartilage, with elastin fibers in matrix
- location: external ear (pinna), epiglottis
- functions: maintains shape while adding flexibility
Fibrocartilage: similar to hyaline cartilage, less firm with thick collagen fibers in matrix
- location: intervertebral discs, pubic symphysis, knee joint discs
- functions: tensile strength, absorbs shock
Bone: hard calcified matrix, many collagen fibers, well-vascularized, osteocytes in lacunae
- location: bones
- functions: support, levers for muscles, calcium storage, blood cell formation (hematopoiesis) in marrow
Blood: red blood cells (erythrocytes) & white blood cells (leukocytes) in fluid matrix (plasma)
- location: in blood vessels
- functions: transports oxygen & carbon dioxide, nutrients, wastes & other substances
Membranes:
Cutaneous (epithelial): skin
-
keratinized stratified squamous epithelium (epidermis)
attached to dense irregular connective tissue (dermis)
- dry membrane (exposed to air)
Mucous: lines body cavities (digestive tract, respiratory tract)
- specialized cells (glands) may secrete mucus
Serous: fluid membrane surrounding organs... pleura (lungs), pericardium (heart), peritoneum (digestive organs)
- visceral & parietal layers
Synovial Membranes: line cavities of freely movable joints
- areolar CT with elastic fibers & adipocytes
- joint (synovial) cavity: potential space with synovial fluid
- synovial membrane lines all internal joint surfaces except hyaline cartilage
- synovial fluid: occupies free spaces in joint cavity; reduces friction
o mostly blood filtrate; viscous fluid containing hyaluronic acid
o weeping lubrication: fluid forced from cartilage during compression & soaked back up when pressure is relieved
- menisci (articular discs): fibrocartilage discs in some synovial joints
o separate articular surfaces & improve fit between bones
- Bursae: flattened fibrous sacs lined with synovial membrane & containing film of synovial fluid
o bunion: swollen bursa at base of big toe
- Tendon Sheath: elongated bursa wrapped around a tendon
Nervous Tissue: neurons & supporting cells
- location: brain, spinal cord & nerves
- functions: transmit electrical signals from sensory receptors to effectors
Muscle Tissue:
Smooth Muscle: uninucleate, spindle-shaped cells; centrally located nucleus; nonstriated; involuntary muscle
- location: lines hollow passageways such as: walls of blood vessels, airways to lungs, stomach, intestines & bladder
- function: contraction helps constrict or narrow lumen of blood vessels, break down & move food through GI tract, move fluids & eliminate wastes
Skeletal Muscle: multinucleate, long cylindrical cells with peripheral nuclei; striated; voluntary muscle
- location: attached to bones of skeleton
- function: contraction helps move bones
Cardiac Muscle: one centrally located nucleus (usually); striated; branched; intercalated discs (desmosomes & gap junctions) between cells
- location: myocardium of heart
- function: contraction helps propel blood from heart to tissues
Tissue Repair:
- Epidermal wound healing: abrasions & minor burns cause damage to epidermal tissue
§ Basal cells migrate to bridge gap in broken tissue
§ Epidermal growth factor stimulates basal stem cells to divide & replace damaged cells & new strata
- Deep wound healing:
§ Inflammatory phase: blood clot forms to loosely unite wound edges
· Inflammation occurs, accompanied by heat, redness, pain & swelling
§ Organization (migratory phase): clot becomes a scab, epithelial cells begin to migrate beneath scab to bridge wound , & granulation tissue forms (blood capillaries form & fibroblasts secrete collagen fibers to fill gap)
§ Regeneration (proliferative phase): extensive growth of epithelial cells beneath scab, as well as growth of fibers & blood vessels
· fibrosis: scar tissue formation
§ Maturation phase: scab sloughs off once epidermis is restored
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
Hypodermis: subcutaneous layer just deep to the dermis
- mostly adipose with some areolar connective tissue
- insulates, absorbs shocks, & anchors skin loosely to muscles
Epidermis: keratinized stratified squamous epithelium
- 4 distinct cell types:
§ 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
§ melanocytes: spider-shaped cells that produce the pigment melanin
· located in deepest layer of epidermis; melanosomes in melanocyte processes transfer melanin to keratinocytes
· melanin granules protect the cell nucleus from UV radiation
- Langerhans' cells (epidermal dendritic cells): macrophages; part of immune system
· produced in bone marrow; migrate to epidermis & form network around keratinocytes
- Merkel cells: associate with disclike sensory nerve endings to form Merkel disc - a sensory receptor for touch
Layers of Epidermis:
- Thick skin has 5 layers (strata)
· Stratum basale, stratum spinosum, stratum granulosum, stratum lucidum & stratum corneum
- Thin skin has only 4 layers... missing stratum lucidum; stratum corneum thinner
Stratum Basale (Stratum Germinativum): basal layer; deepest epidermal layer firmly attached to dermis
- single layer of cells; cell division produces new keratinocytes for all layers
Stratum Spinosum: several layers thick; intermediate filaments form network & attach cells at desmosomes
- keratinocytes are flat & spiny (prickle cells)
- some melanin granules; Langerhans' cells
Stratum Granulosum: 3-5 cell layers thick
- keratohyaline granules: help in keratin formation
- lamellated granules: contain waterproofing glycolipid - released into extracellular space to prevent water loss
Stratum Lucidum: a few rows of clear, flat dead keratinocytes
- only in thick skin
Stratum Corneum: outermost layer; 20-30 cell layers thick
- protects skin with keratin & thick plasma membranes; glycolipids prevent water loss
- dead cells: cornified or horny cells
Dermis: strong, flexible connective tissue
- fibroblasts, macrophages, mast cells & white blood cells with collagen, elastin & reticular fibers
- rich supply of nerve fibers, blood vessels & lymphatic vessels
- houses hair follicles, oil & sweat (sudoriferous) glands
- papillary layer: upper layer composed of areolar connective tissue
§ dermal papillae: projections that indent the epidermis; contain capillary loops & touch receptors (Meissner's corpuscles)
§ dermal ridges on palms of hand & soles of feet form epidermal ridges - genetically determined pattern of ridges; leaves fingerprint
- reticular layer: lower layer (most of thickness of dermis); composed of dense irregular connective tissue
§ thick collagen fiber bundles form lines of cleavage (tension lines) in skin; used in surgery (incisions made parallel to lines to speed healing)
§ flexure lines: dermal folds near joints
Skin Color: dictated by 3 pigments: melanin, carotene, & hemoglobin
- melanin: tyrosine polymer; relies on enzyme tyrosinase in melanocytes
§ passed from melanocytes to basal keratinocytes
§ color ranges from yellow to reddish-brown to black
§ freckles & pigmented moles are due to local melanin accumulations
§ protects cell nucleus from UV light-induced mutations; UV repair mechanisms may stimulate synthesis
- carotene: yellow-orange pigment found in plants (carrots...)
§ accumulates in stratum corneum & hypodermis; most evident in thick skin
- hemoglobin: oxygenated hemoglobin in dermal capillaries gives fair skin a pinkish color
Skin Appendages:
Sweat (sudoriferous) glands: eccrine & apocrine
- eccrine sweat glands (merocrine sweat glands): far more numerous - most abundant on palms of hands, soles of feet & forehead
§ simple, coiled tubular glands; duct opens into pore at skin surface
§ secrete sweat: hypotonic blood filtrate... 99% water with salts, vitamin C, antibodies, metabolic wastes & lactic acid
§ sweat prevents overheating; regulated by sympathetic division of autonomic nervous system
- apocrine sweat glands: mostly confined to axillary & anogenital regions
§ ducts empty into hair follicles
§ in addition to components of sweat, secretion contains lipid & proteins
- ceruminous glands: modified apocrine glands in the external ear canal
§ secrete cerumen (earwax); deters insects & blocks foreign material
Sebaceous (oil) glands: simple alveolar glands (holocrine 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
Hair & hair follicles:
- hair (pili) are flexible strands of mostly dead, keratinized cells
- hair has shaft & root; 3 concentric layers: inner medulla, middle cortex, & outer cuticle
- melanin from melanocytes at base of follicle produce color
- hair follicle: extends from epidermal surface to dermis or hypodermis
§ consists of: hair bulb at base with root hair plexus (sensory nerve endings); hair papilla with capillaries
§ wall of hair follicle: outer connective tissue root sheath, glassy membrane & inner epithelial root sheath
§ hair matrix cells produce the hair
§ arrector pili muscle: smooth muscle bundle that contracts to raise hair
- types of hairs: short, fine vellus hairs; longer, coarser terminal hair
- alopecia: hair loss brought on by aging & hormones
Nails: scalelike epidermal modifications at dorsal surface of distal region of fingers & toes
- nail root: portion of nail that is buried in fold of skin
- nail body: visible portion of nail
- nail matrix: epithelial cells deep to nail root that produce new growth - cells become keratinized as they grow out over nail be
- free edge: part of nail that may extend past distal end of digit
- cuticle (eponychium): fold of skin over nail root
- hyponychium: thickened region of stratum corneum beneath free edge
- lunula: whitish half moon shaped base resulting from thicker skin in the area
- blood in dermal blood vessels beneath nail give pink color to nails
Functions of Skin:
Thermoregulation: 2 ways skin helps homeostatic body temperature regulation:
- liberating sweat at its surface
- adjusting flow of blood in dermis
- keratin in skin cells protects underlying tissues from microbes, abrasion, heat & chemicals
- tightly packed keratinocytes resist invasion by microbes
- lipids released by lamellar granules protect against water loss due to evaporation & water entry
- sebum from sebaceous glands prevents skin & hair from drying out & chemicals assist in killing bacteria
- acidic pH of perspiration retards growth of some microbes
- melanin pigment protects skin cells from UV light damage
- Langerhans cells of epidermis & macrophages of dermis protect against infection
Cutaneous sensation: cutaneous sensations arise in skin
- tactile sensation such as touch, pressure, vibration & tickling as well as thermal sensations of hot & cold
- pain sensations are usually indication of tissue damage
Excretion & Absorption:
- despite waterproof nature skin loses water & heat by evaporation, & water by perspiration
- through perspiration, small amounts of salts, CO2, ammonia & urea are excreted
- absorption of water-soluble substances is negligible, but lipid-soluble substances such as fat-soluble vitamins (A, D, E & K), certain drugs (cortisol), and gases (O2 & CO2) are absorbed through skin
- harmful chemicals such as acetone, heavy metal salts (lead, mercury, arsenic) & toxins in poison ivy & poison oak can also be absorbed
Synthesis of vitamin D: vitamin D is activated in skin by UV light, & liver enzymes convert the activated molecule to calcitriol, the most active form of vitamin D
- vitamin D aids in the absorption of calcium in foods from the GI tract into blood
Metabolic functions
Blood reservoir
Homeostatic imbalances of skin:
Skin cancer
- basal cell carcinoma
- squamous cell carcinoma
- melanoma
Burns:
- first-degree: only part of epidermis is destroyed
- second-degree: portion of epidermis & part of dermis destroyed
- third-degree: portion of dermis & full thickness of dermis & associated structures destroyed
Chapter 6: Bone and Skeletal Tissues
Skeletal Cartilages: cartilage tissue... mostly water; no blood vessels or nerves
- surrounded by a layer of dense irregular connective tissue - the perichondrium, which contains blood vessels
- contains chondrocytes in lacunae, ground substance & fibers
- 3 types: hyaline, elastic & fibrocartilage
Hyaline Cartilages: frosted glass appearance - fine collagen fiber matrix
- most abundant type
- present in: articular (movable joint) cartilages, costal cartilages (connect ribs to sternum), respiratory cartilages (in larynx & upper respiratory passageways) & nasal cartilages
Elastic Cartilages: similar to hyaline cartilage, more elastic fibers (very flexible)
- present in: external ear & epiglottis (larynx covering)
Fibrocartilage: rows of chondrocytes with thick collagen fibers; highly compressible with great tensile strength
- present in: menisci of knee, intervertebral discs & pubic symphysis
Growth of Cartilage:
- appositional growth (growth from outside): chondroblasts in perichondrium secrete new matrix at external face of existing cartilage
- interstitial growth (growth from inside): chondrocytes within matrix divide & secrete new matrix
- growth of cartilage generally ends during adolescence
-
cartilage may become calcified
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
- Long bones: longer than they are wide; shaft & 2 ends (e.g.: bones of arms & legs, except wrist, ankle & patella)
- Short bones: roughly cube-shaped (e.g.: ankle & wrist bones)
- Sesamoid bones: short bones within tendons (e.g.: patella)
- Flat bones: thin, flat & often curved (e.g.,: sternum, scapulae, ribs & most skull bones)
- Irregular bones: odd shapes; don't fit into other classes (e.g.: hip bones & vertebrae)
Functions of bones:
- Support
- Protection
- Movement
- Mineral storage: calcium & phosphate
- Blood cell formation (hematopoiesis): in some red bone marrow
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)
- Membranes: periosteum covers entire surface of bone except joint surfaces
o Fibrous layer: outer layer; dense irregular connective tissue
o Osteogenic layer: inner layer, next to bone
· Osteoblasts: bone-forming cells
· Osteoclasts: bone-destroying cells
o Nutrient foramen: site of nutrient entry from vessels in periosteum at shaft of bone
o Sharpey's fibers: collagen fibers extending from fibrous layer into bone matrix; secure periosteum to underlying bone
o Endosteum: covers trabeculae of spongy bone & canals of compact bone; contains osteoblasts & osteoclasts
Gross anatomy of short, irregular & flat bones:
- periosteum-covered outer compact bone & endosteum-covered inner spongy bone
- no shaft or epiphyses
- bone marrow present between trabeculae; no marrow cavity
- diploe: folded spongy bone in flat bones
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
- osteons: cylinder oriented parallel to long axis of bone; within each cylinder is tubes (concentric circles) of bone matrix (lamellae)
- collagen fibers in lamella run in same direction.. in adjacent lamellae run in opposite direction (resists stress)
- central (Haversian) canal: runs through center of osteon; carries blood vessels & nerve fibers
- perforating (Volkmann's) canal: at right angles to long axis; connect blood vessels & nerves of periosteum to those of central canals & medullary cavity
- osteocytes: bone cells in small cavities called lacunae
- canaliculi: connect lacunae to each other & central canal
- interstitial lamellae: partially formed... fill gaps or have been replaced
- circumferential lamellae: extend around all osteons within shaft (just deep to periosteum)
Spongy bone: trabeculae... a few cell layers of irregularly arranged lamellae & osteocytes connected by canaliculi
- no osteons; nutrients delivered by capillaries in endosteum
Chemical composition of bone:
- organic component: cells (osteocytes, osteoblasts & osteoclasts) & osteoid (organic matrix... ground substance & collagen fibers)
- inorganic component: hydroxyapatites (mineral salts); mostly calcium phosphates
- calcium salt crystals pack around collagen fibers in matrix
Bone markings:
- outward projections: heads, trochanters, spines,...
- depressions & grooves
- see table 6-1
Bone development:
- osteogenesis (ossification)... in infants & adolescents for skeleton formation & growth; in adults for bone remodeling
- Intramembranous ossification: membrane bone forms from fibrous membrane
o Ossification center appears in fibrous connective tissue membrane
o Bone matrix (osteoid) is secreted within membrane
o Woven bone (trabeculae) & periosteum form
o Bone collar of compact bone forms & red marrow develops
- Endochondral ossification: bone forms by replacing hyaline cartilage (at primary ossification center)
o Bone collar forms around diaphysis of cartilage
o Central cartilage calcifies & cavitates
o Periosteal bud enters internal cavity & spongy bone forms
o Diaphysis elongates & medullary cavity forms
o Ossification of epiphyses at secondary ossification centers
- Following secondary ossification, hyaline cartilage remains only:
o On epiphyseal surfaces (joints)
o At junction of diaphysis & epiphysis (forms epiphyseal (growth) plates)
Postnatal bone growth:
- longitudinal growth (growth in bone length)
- appositional growth (growth in bone width)
- regulated by growth hormone, which is regulated by thyroid hormones; later regulated by steroid hormones
Bone Remodeling:
Bone deposit: for bone growth, or to replace injured bone
- osteoid seam of bone matrix is slowly calcified (calcification front forms)
- requires calcium & phosphate & enzyme alkaline phosphatase... hydroxyapatite begins to form & speeds mineralization of surrounding matrix
Bone resorption: for bone remodeling
- 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
Control of Remodeling:
Hormonal control:
- parathyroid hormone (PTH, from parathyroid gland): stimulates osteoclasts to resorb bone to raise blood calcium levels
- calcitonin (from parafollicular (C) cells of thyroid): inhibits osteoclasts & stimulates calcification of bone matrix to lower blood calcium levels
Mechanical stress:
- Wolff's law: a bone remodels or grows in response to the forces placed on it
- Bones are generally thickest at sites with greatest stress
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) formation
- fibrocartilagenous callus formation
- bony callus formation
- bone remodeling
Osteomalacia: bones are inadequately mineralized (osteoid not calcified)
- symptoms: pain when weight placed on bones
- cause: insufficient dietary calcium or vitamin D (helps to absorb dietary calcium from intestine)
- treatment: calcium & vitamin D supplements & sunlight
Rickets: similar disorder in children
- symptoms: bowed legs; deformities of pelvis, skull & rib cage; ends of long bones often enlarged
- cause & treatment: same as osteomalacia
Osteoporosis: bone resorption outpaces bone deposit
- normal bone matrix composition, but bone mass is reduced & bones are porous
- causes: many, including hormonal deficiencies (especially steroid hormone deficiency due to decline in old age), insufficient exercise, poor diet,...
- treatment: calcium & vitamin D supplement, & hormone replacement therapy (HRT)
Paget's disease: excessive bone formation & breakdown
- Pagetic bone : abnormally high ratio of spongy bone to compact bone
- symptoms: progressive weakening & deformity of bones (esp. spine, pelvis, femur & skull)
- cause: unknown, may be viral
- treatment: calcitonin & drug therapy to prevent bone breakdown
Chapter 7: The Skeleton
These notes are meant as a reference for bone location & functional significance. Please do not study or try to memorize the bone definitions - just know their functions & significance where applicable. Also, know the bone types (long, short, etc.), surface markings, & be able to place bones in the appropriate groups (axial vs. appendicular skeleton, bones of pectoral & pelvic girdle, upper & lower limbs, skull, etc.). There will be some questions identifying bones by their features &/or location, but the best way to learn this is by learning the bones & features from the bone models in lab or... from the website Bones Review.
- consists of bones arranged along (longitudinal) axis of body
- includes: skull bones, auditory ossicles (ear bones), hyoid bone, ribs, sternum (breastbone) & vertebral column (backbone)
- consists of the bones of the upper & lower limbs (extremities), & the bones forming the pectoral & pelvic girdles (shoulder & hip bones) that connect the limbs to the axial skeleton
Bone Types:
- long bones: have greater length than width; consist of diaphysis (shaft) & epiphyses; slightly curved to absorb stress
o mostly compact bone in diaphysis, with both spongy & compact bone in epiphyses
o includes: femur, tibia & fibula, humerus, radius & ulna & phalanges of fingers & toes
- short bones: cube-shaped; spongy bone with thin outer layer of compact bone
o includes: carpal (wrist) bones (except pisiform, which is a sesamoid bone) & tarsal (ankle) bones (except calcaneus, which is an irregular bone)
- flat bones: thin; composed of 2 parallel plates of compact bone enclosing a layer of spongy bone
o offer protection & broad surface for muscle attachment (tendons)
o includes: cranial bones, sternum & ribs, & scapulae (shoulder blades)
- irregular bones: complex shapes; don't fit into other categories
o includes: vertebrae, coxal (hip) bone, calcaneus (heel bone), & some facial bones
- sesamoid bones: sesame shaped bones that develop in tendons to protect against friction & stress
o includes patellae (kneecaps) & pisiform (smallest wrist bone)
- sutural bones: small bones located within immoveable joints (sutures)
o vary in number among individuals & not included in named bones
Bone Surface Markings:
- surface markings: structural features of bones adapted for specific functions
- may develop or change later in life at sites of tendons, ligaments, aponeuroses or fasciae in response to tension
- depressions & openings: sites allowing passage of soft tissue (blood vessels, nerves, etc.) or formation of joints
o fissure: narrow slit between adjacent bone parts where blood vessels & nerves pass
o foramen: opening through which blood vessels, nerves or ligaments pass
o fossa: shallow depression
o sulcus: groove along a bone that fits a blood vessel, nerve or tendon
o meatus: tubelike opening
- processes: projections or outgrowths of bone that form joints or attachment points for tendons & ligaments
o condyle: large round projection at end of bone; usually participates in joint
o facet: smooth, flat articular (joint) surface of bone
o head: rounded projection of bone supported by neck; often fits with complementary depression on another bone within joint
o crest: prominent ridge on bone
o epicondyle: projection above a condyle (above joint)
o line (linea): long, narrow ridge or border; less prominent than crest)
o spinous process: sharp, slender projection (on vertebrae)
o trochanter: very large projection (on femur)
o tubercle: small, rounded projection
o tuberosity: large, rounded, usually roughened projection
- cranial bones: 8 bones which enclose & protect the brain
o frontal bone: forms the forehead, roofs of the orbits & anterior part of cranial floor
· glabella: smooth portion between orbits
· frontal sinuses: cavities in frontal bone lateral to glabella
· supraorbital foramen (notch): complete (foramen) or incomplete (notch) opening above orbits
o parietal bones (2): form the greater portions of the sides & roof of the cranial cavity
o temporal bones (2): form the inferior lateral aspects of the cranium & part of the cranial floor
· zygomatic process: articulates with the temporal process of the zygomatic bone to form zygomatic arch
· external auditory meatus: ear canal
· mastoid process: rounded projection posterior to external auditory meatus; point of attachment for several neck muscles (sternocleidomastoid)
· styloid process: sharp, toothlike projection that serves as the point of attachment for muscles & ligaments of the tongue & neck
· internal auditory meatus: opening for passage of cranial nerves VII & VIII
· carotid & jugular foramina: openings on the inferior surface of the skull for passage of the carotid arteries & jugular veins
o occipital bone: forms the posterior part & most of the base of the cranium
· foramen magnum: large opening at base of skull where the medulla oblongata of brain connects with the spinal cord
· occipital condyles: oval processes on either side of the foramen magnum that articulate with the atlas (1st cervical vertebra)
o sphenoid bone: forms middle part of the base of the skull
· articulates with all the other cranial bones, holding them together
· sphenoidal sinuses: cavities at medial aspect that drain into nasal cavity
· sella turcica: saddle-shaped structure on superior surface of medial aspect that houses the pituitary gland of brain
· greater wings: project laterally from body of sphenoid bone & form anterolateral floor of cranium (inferior to lesser wings)
· lesser wings: pointed winglike projections above greater wings; form posterior part of orbits
· optic foramen: opening just anterior to sella turcica & between lesser wings in posterior aspect of each orbit for passage of optic nerve
o ethmoid bone: spongelike bone located on the midline in anterior part of cranial floor, intermediate to orbits
· ethmoidal sinuses: air cavities between nasal cavity & orbits
· perpendicular plate: forms superior portion of nasal septum
· cribriform plate: in anterior floor of cranial cavity; forms roof of nasal septum
· crista galli: ridge above cribriform plate; point of attachment for membranes covering brain
· superior & middle nasal conchae: lateral projections in nasal cavity; help to filter & warm inspired air
§ superior nasal conchae are usually not visible within nasal cavity
§ inferior nasal conchae are separate bones (not part of ethmoid bone)
- Facial Bones: 14 bones
o nasal bones (2): form part of bridge of nose (rest of nose is cartilage)
o maxillae (2): form the upper jawbone
· articulate with every other bone of face except mandible (jawbone)
· maxillary sinus: cavity in each maxilla that empties into nasal cavity
· palatine process: forms anterior 3/4 of hard palate (roof of mouth)
· infraorbital foramen: opening in each maxilla below orbit
· cleft palate & cleft lip may be due to incomplete fusion of the palatine processes or palatine bones
o zygomatic bones (2): cheek bones; form prominences of cheeks & part of lateral wall & floor of orbits
· temporal process: projection toward temporal bone that, with zygomatic process of temporal bone, forms zygomatic arch
o lacrimal bones (2): form anterior part of medial wall of orbits
· lacrimal fossa: depression in each lacrimal bone that houses a lacrimal foramen, through which tears pass into nasal cavity
o palatine bones (2): form posterior 1/4 of hard palate & part of the floor & lateral wall of nasal cavity, & a small portion of orbits
o inferior nasal conchae (2): lateral projections in walls of nasal cavity; inferior to middle nasal conchae of ethmoid bone
o vomer: forms superior aspect of nasal septum
o mandible: jawbone
· only movable facial bone (other than auditory ossicles)
· mandibular angle: curved portion at posteriolateral aspect of mandible
· mandibular condyles (condylar processes): articulate with temporal bone to form temporomandibular joint (TMJ)
· coronoid processes: anterior to mandibular condyles; point of attachment for temporalis muscle
· mental foramen: openings at anterior aspect of mandible
- Skull Features:
o nasal septum: formed by the perpendicular plate of the ethmoid bone (superior) & vomer (inferior) posteriorly & septal cartilage anteriorly
· deviated septum: break at junction of vomer & septal cartilage - blocks air passageways & may lead to infection; usually can be surgically corrected
o orbits: eye sockets; contains eyeball & associated structures
· formed by 3 cranial bones (frontal, sphenoid & ethmoid) & 4 facial bones (palatine, zygomatic, lacrimal & maxilla)
o sutures: immovable joints (in adults) between flat bones of skull
· sutures in child & infant skulls are often movable
· many sutures throughout skull; 4 prominent sutures:
§ coronal suture: joins frontal bone with both parietal bones
§ sagittal suture: joins 2 parietal bones
§ lambdoid(al) suture: joins 2 parietal bones with occipital bone
§ squamous(al) suture: joins parietal bone with temporal bone on both lateral aspects of skull
o paranasal sinuses: paired cavities in bones surrounding nasal cavity that produce mucus & resonate to aid in voice production
· present in frontal, sphenoid, ethmoid & maxillary bones
· sinusitis: inflammation of mucosa of paranasal sinuses due to infection or allergic reaction; blockage leads to pressure buildup & headaches
o fontanels (soft spots): fibrous membrane-filled spaces in fetal & newborn skull between cranial bones that allow for growth of skull & flexibility during childbirth
· replaced later by bone to become sutures
· anterior fontanel: at midline between 2 parietal bones & frontal bone
· posterior fontal: at midline between 2 parietal bones & occipital bone
· anteriolateral fontanels: lateral on skull between, frontal, parietal, temporal & sphenoid bones
· posteriolateral fontanels: lateral on skull between, parietal, temporal & occipital bones
Hyoid Bone: U-shaped bone suspended from the styloid processes of the temporal bones by ligaments & muscles
- doesn't articulate with any other bone
- located in anterior neck between mandible & larynx; supports tongue & attaches to muscles of tongue, neck & pharynx
Vertebral Column (spine or backbone): forms skeleton of trunk of the body with sternum & ribs
- encloses & protects spinal cord, supports head & is point of attachment for ribs, pelvic girdle & back muscles
- composed of 24 vertebrae, sacrum & coccyx
o 7 cervical vertebrae in neck region
o 12 thoracic vertebrae posterior to thoracic cavity
o 5 lumbar vertebrae in lower back region
o sacrum: 5 fused sacral vertebrae
o coccyx: 4 fused coccygeal vertebrae
- cervical, thoracic & lumbar vertebrae are movable; sacrum & coccyx are not
- 4 slight bends seen from the side called normal curves
o cervical & lumbar curves are convex (bulge out)
o thoracic & sacral curves are concave (cup in)
o abnormal curves: kyphosis, lordosis & scoliosis; due to various disorders
- intervertebral discs: fibrocartilage & elastic tissue discs between bodies of adjacent vertebrae
- form intervertebral joints; highly resistant to shock
- vertebra parts:
o body: broad flat region that accommodates intervertebral disc
o pedicles: connect body to processes
o lamina: flat smooth surface on either side of spinous process
o vertebral foramen: opening between body & processes for spinal cord
o transverse processes: lateral processes on either side of spinous process
o spinous process: posterior process
o superior articular processes
o inferior articular processes
- cervical vertebrae (7)
o have transverse foramen in transverse processes for vertebral artery, vein & nerve to pass (thoracic & lumbar vertebrae do not have transverse foramen)
o spinous process of C2 - C6 is bifid (split into 2 parts)
o atlas (C1): 1st cervical vertebra; articulates with occipital condyles at base of skull
· lacks body & spinous process
· joints provide up & down head movement (yes)
o axis (C2): 2nd cervical vertebra
· dens (odontoid process): peglike projection that makes a pivot the atlas & head rotate around (no)
- thoracic vertebrae (12): giraffe/elephant
o larger than cervical vertebrae; spinous process projects inferiorly
o articulate with ribs
- lumbar vertebrae (5): moose
o larger that thoracic vertebrae; spinous process projects posteriorly
- sacrum (5 fused vertebrae)
o vertebrae begin to fuse between 16-18 years of age; ends around age 30
o sacral tuberosity on anterior medial sides joins with ilium to form sacroiliac joint
- coccyx (usually 4 fused vertebrae)
o vertebrae fuse between 20-30 years of age
Sternum (breastbone): located in center of anterior thoracic wall
- composed of 3 parts:
o manubrium: superior rounded part
· suprasternal (jugular) notch: depression on superior surface
· articulates with costal cartilage of 1st & 2nd ribs
o body: long middle part
· articulates directly or indirectly with costal cartilage of 2nd through 10th ribs
o xiphoid process: inferior, smallest part
Ribs (24; 12 pairs): give structural support to sides of thoracic cavity & protection to organs of thoracic cavity
- most (rib pairs 1 though 10) attach directly or indirectly to sternum
- all ribs attach posteriorly to thoracic vertebrae
- 7 true pairs of ribs: attached directly to sternum through costal cartilage
- 5 false pairs of ribs: attached indirectly (through cartilage-costal cartilage connection) ,or not at all, to sternum
o 2 pairs of floating ribs (rib pairs 11 & 12): not attached to sternum
- rib fractures are most common chest injuries
o may puncture heart or great vessels, lungs, trachea, bronchi, esophagus, spleen, liver or kidneys
- clavicle (2): (collarbone); S-shaped bone in anterior & superior thoracic cavity, above 1st rib
o rounded medial end articulates with manubrium of sternum
o flat lateral end articulates with acromion of scapula
o one of the most frequently broken bones (falling on arm)
- scapula (2): (shoulder blade); large triangular flat bone in posterior thoracic between 2nd & 7th ribs
o spine: sharp ridge running diagonally across posterior surface
o acromion: lateral end of spine; articulates with clavicle
o glenoid cavity (fossa): lateral shallow depression; articulates with head of humerus
o coracoid process: lateral projection at anterior surface; point of tendon attachment
- humerus (2): longest & largest bone of arm; articulates proximally with scapula & distally with ulna & radius
o head: rounded superior portion; articulates laterally with glenoid cavity of scapula to form glenohumeral joint
o greater tubercle: lateral projection distal to head & neck
o lesser tubercle: projects anteriorly
o deltoid tuberosity: lateral roughened area at middle of shaft; point of attachment for tendons of deltoid muscle
o capitulum: lateral rounded knob that articulates with head of radius
o trochlea: medial spool-shaped projection that articulates with ulna
o coronoid fossa: anterior depression that receives coronoid process of ulna
o olecranon fossa: posterior depression that receives olecranon of ulna
o medial & lateral epicondyles: projections on either side of distal end; points of tendon attachment
- ulna: at medial (pinky) aspect of forearm; looks like wrench
o olecranon: superior process that fits with olecranon fossa of humerus
o coronoid process: inferior to olecranon; fits with coronoid fossa of humerus
o trochlear notch: receives trochlea of humerus
o styloid process: medial process
- radius: at lateral (thumb) aspect of forearm
o head: articulates with capitulum of humerus
o styloid process: lateral process
- carpals (8): wrist bones
o arranged in 2 transverse rows
o proximal row; from lateral to medial
· scaphoid
· lunate
· triquetrum
· pisiform
o distal row; from lateral to medial
· trapezium
· trapezoid
· capitate
· hamate
o Sally Left The Party To Take Cathy Home
- metacarpals (5 on each hand)
o numbered I - V, starting at thumb
- phalanges (14 on each hand)
o each finger has proximal, middle & distal phalanges, except thumb has only proximal & distal phalanges
Pelvic Girdle: Coxal Bone - connects lower limbs with sacrum & vertebral column
- Coxal Bone (Hip Bone): 3 fused bones: ilium, ischium & pubis
o ilium: broad flat bone; forms superior part of pelvic girdle
· iliac crest: rounded /curved region at top of ilium
· anterior superior & anterior inferior iliac spines
· acetabulum: lateral socket for head of femur
o ischium: posterior & inferior part of pelvic girdle
· ischial tuberosity: rough region at posterior & inferior aspect
· greater & lesser sciatic notches
· ischial spine: between greater & lesser sciatic notches
o pubis: anterior & inferior part of pelvic girdle
· pubic symphysis: fibrocartilage joint between 2 pubic bones
· obturator foramen: large opening running blood vessels & nerves between ischium & pubis
o Female pelvis is wider & shallow that male's, which accommodates childbirth
Bones of Lower Limb (Leg):
- femur (2): upper leg (thigh) bone
o articulates with tibia - tibiofemoral joint
o head: articulates with acetabulum of coxal bone; points medially
· fovea capitis femoris: small shallow depression at center of head
o neck: slender region inferior to head
o greater & lesser trochanters: lateral & medial projections (greater trochanter is lateral & superior)
o linea aspera: narrow ridge posterior on shaft of femur
o medial & lateral condyles: articulate with medial & lateral condyles of tibia
- patella (kneecap): triangular (sesamoid) bone anterior on leg at junction of femur & tibia
o base: flat superior surface
o apex: pointed inferior surface
- tibia (shin bone): wider bone of lower leg; articulates with femur & fibula at proximal end & talus & fibula at distal end
o anterior crest: sharp ridge on anterior surface (can be felt close to skin surface of shin)
o intercondylar eminence (tubercles): 2 small superior projections in articulation with femur
o medial malleolus: projection at inferior (distal) aspect
- fibula: thin, smaller bone of lower leg; articulates with tibia proximally & talus distally
o anterior crest: sharp ridge on anterior surface
o lateral malleolus: projection at inferior (distal) aspect
- tarsals (7 on each leg): ankle bones
o calcaneus: heel bone
o talus: anterior & superior to calcaneus; has wheel-like projection articulates with tibia & fibula
o cuboid
o navicular
o lateral, intermediate & medial cuneiforms
- metatarsals (5 on each foot)
o numbered I - V, starting at big toe
- phalanges (14 on each foot)
- each toe has proximal, middle & distal phalanges, except big toe has only proximal & distal phalanges