anatomy 3 exam

chapters 7,9,10,11

6 major functions of bones

support-body and soft organs

protection-brain,spinal cord,vital organs

movement-levers for muscle action

blood electrolyte and acid/base balance-minerals (calcium and phosphorus) can buffer blood pH

blood cell formation-(hematopoiesis) in marrow cavities

triglyceride (energy) storage-in bone cavities

2 main groups of bones

axial skeleton, and appendicular skeleton

skeletal cartilage

• contains no blood vessels or nerves

• dense connective tissue girdle of perichondrium contains blood vessels for nutrient delivery to cartilage

3 types of skeletal cartilage

1. hyaline cartilage

2. elastic cartilage

3. fibrocartilage

hyaline cartilage

provide support, flexibility, and resilience (most abundant type)

elastic cartilage

similar to hyaline cartilages, but contain elastic fibers

fibrocartilage

• collagen fibers- have great tensile strength

• act as shock absorbers

long bones

longer than they are wide (humerus)

short bones

• cube shaped bones (in ankle and wrist)

• sesamoid bones (within tendons, e.g patella)

flat bones

thin, flat, slightly curved (sternum)

irregular bones

complicated shapes (vertebrae)

compact bone

• dense outer layer

• skeleton ¾ compact and ¼ spongy bone by weight

spongy (cancellous) bone

• honeycomb of trabeculae

• found in center of ends and center of shafts of long bones and in middle of nearly all others

• covered by more durable compact bone

medullary cavity (marrow cavity)

space in the diaphysis of a long bone that contains bone marrow

epiphyses

enlarged ends of a long bone/ strengthen joint and anchor ligaments and tendons

articular cartilage

layer of hyaline cartilage that covers joint surface; allows joint to move more freely

nutrient foramina

minute holes in bone surface that allows blood vessels to penetrate

periosteum

external sheath covering most bone

outer fibrous layer of collagen

• some fibers continuous with tendons

• perforating fibers- penetrate into bone marrow

inner osteogenic layer of bone- forming cells

important to bone growth and healing of fractures

endosteum

• thin layer of reticular connective tissue lining marrow cavity

• has cells that dissolve osseous tissue and others that deposit it

epiphyseal plate (growth plate)

• area of hyaline cartilage that separates epiphyses and diaphyses of children’s bones

• enables growth in length

epiphyseal line

in adults, a bony scar that marks where growth plate used to be

microscopic anatomy of bone

bone is connective tissue that consists of cells, fibers, and ground substance

osteogenic (osteoprogenitor) cells

stem cells in periosteum and endosteum that give rise to osteoblasts

osteoblasts

bone forming cells

osteocytes

mature bone cells

osteoclasts

cells that break down (resorb) bone matrix

osteogenic cells

multiply continuously and give rise to most other bone cell types

osteoblasts

• form single layer of cells under endosteum and periosteum

• nonmitotic

• synthesize soft organic matter of matrix which then hardens by mineral deposition

• stress stimulates osteogenic cells to multiply rapidly and increase the number of osteoblasts which reinforce bone

osteocytes

• former osteoblasts that have become trapped in the matrix they deposited

• lacunae- tiny cavities where osteocytes reside

• canaliculi- little channels that connect lacunae

• cytoplasmic processes of osteocytes reach into canaliculi and contact processes of neighboring cells

• gap junctions allow for passage of nutrients, wastes, signals

osteoclasts

• bone dissolving cells found on bone surface

• osteoclasts develop from same bone marrow stem cells that give rise to blood cells (different origin from other bone cells)

• cells often reside in resorption bays (pits in bone surface)

• dissolving bone is part of bone remodeling

the matrix

matrix of osseous tissue is, by dry weight, about one third organic and two thirds inorganic matter

organic matter

• synthesized by osteoblasts

• collagen, carbohydrate-protein complexes, such as glycosaminoglycans, proteoglycans, and glycoprotein

inorganic matter

• 85% hydroxyapatite (crystalized calcium phosphate salt)

• 10% calcium carbonate

• other minerals (flouride, sodium, potassium, magnesium)

histology of compact bone reveals osteons (haversian systems)

• concentric lamellae surround a central (haversian) canal running longitudinally

• perforating canals- transverse or diagonal passages

• circumferential lamellae fill outer region of dense bone

• interstitial lamellae fill irregular regions between osteons

spongy bone consist of

• lattice of bone covered with endosteum

  • slivers of bone called spicules

  • thin plates of bone called trabeculae

• spaces filled with red bone marrow'

• few osteons and no central canals

  • all osteocytes close to bone marrow

• provides strength with minimal weight

  • trabeculae develop along bones lines of stress

bone marrow

soft tissue occupying marrow cavities of long bones and small spaces of spongy bones

red marrow (myeloid tissue)

• contains hemopoietic tissue- produces blood cells

• in nearly every bone in a child

• in adults, found in skull, vertebrae, ribs, sternum, part of pelvic girdle, and proximal heads of humerus and femur

yellow marrow

• found in adults

• fatty marrow that does not produce blood

• can transform back to red marrow in the event of chronic anemia

osteogenesis (ossification)

bone

intramembranous ossification

• membrane bone develops from fibrous membrane

• forms flat bones: clavicles and cranial bones

endochondral ossification

• cartilage (endochondral) bone forms by replacing hyaline cartilage

• forms most of the rest of the skeleton

bone growth and remodeling

ossification continues throughout life with the growth and remodeling of bones

bones grow in two directions

length and width

• increased/decrease load (Wolffs Law)

bone elongation- epiphyseal plate- cartilage transitions to bone

• functions as growth zone where bone elongates

• has typical hyaline cartilage in the middle with transition zones on each side where cartilage is replaced by bone

• metaphysis is zone of transition facing the marrow cavity

• this is interstitial growth- growth from within

• epiphyses close when cartilage is gone- epiphyseal line of spongy bone marks site of former epiphyseal plate

  • lengthwise growth is finished

  • occurs at different ages in different bones

bone widening and thickening

• appositional growth- occurs at bone surface

  • continual growth in diameter and thickness

  • intramembranous ossification

  • osteoblasts of inner periosteum deposit osteoid tissue

    • become trapped as tissue calcifies

  • lay down matrix in layers parallel to surface

    • forms circumferential lamellae

    • osteoclasts of endosteum marrow cavity

bone remodeling (absorption and deposition)

• occurs throughout life- 10% of skeleton per year

  • repairs micro fractures, releases minerals into blood, reshapes bones in response to use and disuse

Wolffs law of bone

• architecture of bone determined by mechanical stresses placed on it

  • remodeling is a collaborative and precise action of osteoblasts and osteoclasts

  • bony processes grow larger in response to mechanical stress

puberty and bone growth

• bone growth especially rapid in puberty and adolescene

  • surges of growth hormone, estrogen, and testosterone occur and promote ossification

  • these hormones stimulate multiplication of osteogenic cells, matrix deposition by osteoblasts, and chondrocyte multiplication and hypertrophy in metaphyses

  • girls grow faster than boys and reach full height earlier

    • estrogen has stronger effect than testosterone on bone growth

  • males grow for a longer time and also taller

• anabolic steroids cause growth to stop

  • epiphyseal plate “closes” prematurely

  • results in abnormally short adult stature

physiology of osseous tissue

• a mature bone remains a metabolically active organ

  • involved in its own maintanence of growth and remodeling

  • exerts a profound influence over the rest of the body by exchanging minerals with tissue fluid

    • distrubance of calcium homeostasis in skeleton disrupts function of other organ system

      • especially in nervous and msucular

mineral deposition (mineralization)

• process in which calcium, phosphate, and other ions are taken from blood and deposited in bone

  • osteoblasts produce collagen fibers that spiral the length of the osteon

  • fibers become encrusted with minerals

mineral resorption

• process of dissolving bone and releasing minerals into blood

  • performed by osteoclasts

  • hydrogen pumps in membranes secretes H+ into space between osteoclasts and bone surface

  • hydrochloric acid (pH 4) dissolves bone minerals

  • acid protease enzyme digests collagen

calcium and phosphate are used for much more than bone structure

• phosphate is a component of DNA, RNA, ATP, phospholipids, and pH buffers

• calcium needed in neuron communication, muscle contraction, blood clotting, exocytosis

minerals are deposited in the skeleton and withdrawn when they are needed for other purposes

• total of about 1,100 g of calcium in adult body with 99% of it in bones

• normal calcium concentration in blood plasma is 9.2 to 10.4 mg/dL

calcium homeostasis depends on a balance between

dietary intake, urinary and fecal losses, and exchanges between osseous tissue

calcium homeostasis is regulated by three hormones

1. calcitriol: secreted when blood Ca2+ low (raises blood Ca2+)

2. parathyroid hormone: secreted when blood Ca2+ low (raises blood Ca2+)

3. calcitonin: secreted when blood Ca2+ high (lowers blood Ca2+)

calcitriol synthesis and action

• calcitriol is a hormone that raises blood calcium levels

• produced by converting UV radiation at skin and actions of the liver and kidneys

hypocalcemia

• deficient calcium in blood

• changes membrane potentials and causes overly excitable nervous system and tetany (muscle spasms)

  • laryngospasm can cause suffocation

• caused by vitamin D deficiency, diarrhea, thyroid tumors, underactive parathyroid glands

• pregnancy and lactation increase risk of hypocalcemia

hypercalcemia

• excessive calcium levels

• makes ion channels less responsive and thus nerve and muscle are less excitable

  • can cause emotional disturbance, muscle weakness, sluggish reflexes, cardiac arrest

• hypercalcemia rarely occurs

factors influencing bone growth

• at least 20 or more hormones, vitamins, and growth factors affect osseous tissue

1. growth hormone

2. deficiency of thyroid hormone

growth hormone

• stimulates epiphyseal plate activity

  • low HGH: dwarfism

  • high HGH: gigantism

defiency of thyroid hormone

sex hormones

• promote bone formation

• stimulate ossification of epiphyseal plates

bone deposit requires

• vitamins a,c,d, and several minerals (including calcium and phos

physical stress

• stimuates bone growt

orthopedics

• branch of medicine dealing with prevention and correction of injuries and disorders of bones, joints, and muscles

• name implies its origin as field treating skeletal deformities in children

• includes the design of artificial joints and limbs and the treatment of athletic injuries

stress fractures

• break caused by abnormal trauma to

pathological fracture

• break in a bone weakened by disease (e.g. bone cancer or osteoporosis)

most common bone disease

osteoporosis

osteoporosis

• bone lose mass and become brittle due to loss of organic matrix and minerals

  • affects spongy bone the most since it is the most metabolically active

  • subject to pathological fractures of hip, wrist, and vertebral column

  • kyphosis (widows hump) deformity of spine due to vertebral bone loss

osteoporosis

• estrogen maintains bone density in both sexes; inhibits resorption by osteoclasts

  • postmenopausal white women at greatest risk

  • ovaries cease to secrete estrogen

  • white women begin to lose bone mass as early as age 35

    • by age 70, average loss is 30% of bone mass

risk factors of osteoporosis

• race, age, gender, smoking, diabetes mellitus, diets poor which are poor in: calcium, protein, vitamin C and D

• also seen in young female athletes with low body fat causing them to stop ovulating and decrease estrogen secretion

treatments for osteoporosis

• estrogen replacement therapy slows bone resorption, but increases risk of breast cancer, stroke, and heart disease

• drugs fosamax, actonel destroy osteoclasts

• PTH slows bone loss if given as daily injection

  • forteo increases density by 10% in 1 year

    • may promote bone cancer so use is limited to 2 years

• best treatment is prevention

  • excersise and a good bone building diet between ages 25 and 40

osteomalacia and rickets

• calcium salts not deposited

• rickets (childhood disease) causes bowed legs and other bone deformities

• soft bones

• cause: vitamin D deficiency or insufficient dietary calcium

joint or articulation

site where two or more bones meet

function of joint

• give skeleton mobility

• hold skeleton together

3 functional classifications based on amount of movement allowed by the joint

• synarthroses- immovable

• amphiarthroses- slightly movable

• diarthroses- freely movable

3 structural classifications based on material binding bones together and whether or not a joint cavity is present

• fibrous

• cartilaginous

• synovial

fibrous joints

• bones joined by dense fibrous connective tissue

• no joint cavity

• most are synarthrotic (immovable)

3 types of fibrous joints

• sutures

• syndesmoses

• gomphoses

cartilaginous

• bones united by cartilage

• no joint cavity

2 types of cartilaginous joints

• synchondroses

• symphyses

synovial joints

• all are diarthrotic (freely moveable)

• includes all limb joints; most joints of the body

6 types of synovial joints

• plane

• hinge

• pivot

• condyloid

• saddle

• ball and socket

synovial joints

• a joint in which two bones are separated by a joint cavity

  • most familiar type of joint

  • most are freely movable

  • most structurally complex type of joint

  • most likely to develop painful dysfunction

  • most important joints for physical and occupational therapists, athletic coaches, nurses, and fitness trainers

  • their mobility makes them important to quality of life

6 distinguishing features of all synovial joints

1. articular cartilage: hyaline cartilage

2. joint (synovial) cavity: small potential space

3. articular (joint) capsule

   1. outer fibrous capsule

   2. inner synovial membrane

4. synovial fluid

   1. viscous slippery filtrate of plasma and hyaluronic acid

   2. lubricates and nourishes articular cartilage

5. 3 possible types of reinforcing ligaments

   1. capsular (intrinsic) part of the fibrous capsule

   2. extra capsular- outside the capsule

   3. intracapsular- deep to capsule, covered by synovial membrane

6. rich nerve and blood vessel supply

   1. nerve fibers detect pain, monitor joint position and stretch

   2. capillary beds produce filtrate for synovial fluid

anatomy of synovial joints

• bursa

• tendon sheath

• meniscus

bursa

fibrous sac filled with synovial fluid, located between muscles, where tendons pass over bone, or between bone and skin

tendon sheath

• elongated cylindrical bursa wrapped around a tendon

meniscus

• moon shaped cartilage in knee, in each knee, menisci extend inward from the left and right

• these cartilages absorb shock and pressure

• guide bones across each other and improve their fit together

• stabilize the joints, reducing the chance of dislocation

basic components of a lever

• long bones act as levers to enhance the speed or power of limb movement

• lever; any elongated, rigid object that rotates around a fixed point called a fulcrum (pivot)

• rotation occurs when an effort applied overcomes resistance (load) at some other point

types of levers

• first class lever

• second class lever

• third class lever