skeletal system - feedback loops, fractures, joints, aging

resorption > ossification effect

less bone density, weak/fragile bones

resorption < ossification effect

excess bony deposits (bone spurs)

ossification

osteoblasts building new bone tissue

types of fractures

• compound fracture

• communited fracture

• greenstick fracture

• spiral fracture

• transverse fracture

compound fracture

ends of bones protruding through the skin

communited fracture

bone splinters/fragments between the two main fragments

greenstick fracture

partial fracture; one side breaks and the other side bends

• occurs only in children whose bones are not fully ossified

spiral fracture

a bone breaks in half by a twisting force or impact

transverse fracture

breaks straight across the bone

oblique fracture

bone is broken at an angle

displaced fracture

bone breaks, moves out of alignment

nondisplaced fracture

bone breaks but does not move out of alignment

closed fracture

skin is not broken

stress fracture

a very thin crack, also called a hairline fracture

repair of bone steps (4)

1. fracture hematoma forms

2. procallus forms (soft callus)

3. bony callus forms

4. bone remodeling

fracture hematoma

blood vessels at the site of fracture form a clot

• capillaries grow into hematoma and WBCs/osteoclasts remove dead or damaged tissues

• last several weeks

procallus

• actively growing connective tissue/collagen fibers secreted

• becomes a mass of repair tissue that bridges the broken ends of the bone

• lasts about 3 weeks

bony callus

osteoblasts develop and produce spongy bone trabeculae

• tissue at fracture eventually is completely converted to spongy bone (3-4 months)

bone remodeling

compact bone replaces spongy bone at the periphery

• osteoclasts gradually resorb dead fragment of original broken bone

3 types of joint classification

• fibrous/immovable/synarthrosis

• cartilaginous/semi-movable/amphiarthrosis

• synovial/freely-moveable/ diarthrosis

fibrous/immovable/synarthrosis joint

bones held together by fibrous connective tissue rich in collagen; no synovial cavity

• ex: cranial sutures, teeth

cartilaginous/semi-movable/amphiarthrosis joint

lack synovial cavity, little movement

• ex: pubic symphysis, intervertebral discs, ribs

synovial/moveable/diarthrosis joints

have a space called the synovial cavity between articulating bones

ligaments

tough bands of connective tissue that attach bone to bone

tendons

tough bands of connective tissue that connect muscle to bone

synovial fluid

• secreted by cells in the synovial membrane

• reduces friction/lubricates

bursae

• saclike structures found near joints and other points of friction

• filled with fluid similar to synovial fluid and allows cushioning

meniscus (articular discs)

• pads of fibrocartilage that lie between the articular surfaces of the bone

• further cushions joints and prevent damage to joints

fibrocartilage

cartilage that contains thick bundles of collagen fibers

types of synovial joints

1. hinge joint

2. pivot joint

3. planar joint

4. ball and socket joint

hinge joint

angular, open-closing motion (one way)

• ex: knee, elbow

pivot joint

“peg in a hole”; allows rotation around a central axis

• ex: atlantoaxial joint - allows head to move side to side

planar joint

2 opposed flat surfaces that glide over each other; side to side and back and forth gliding

• ex: articular facets of the vertebrae; intercarpal and intertarsal joints

ball and socket joint

ball-like surface of one bone fits into the cup-like depression of another bone; wide range of motion

• ex: hip or shoulder joint

strain

damage to muscle/tendon

sprain

twisting/wrenching of a joint that stretches or tears its ligaments but does not dislocate the bone

• may damage blood vessels, muscles, tendons, and nerves

• considerable swelling

dislocation

displacement of a bone from a joint with tearing of ligaments, tendons, and articular capsule causing:

• intense pain

• joint instability

• reduced muscle strength

• difficulty moving/joint stiffness

sublaxation

partial dislocation

avulsion

unattaching fragment of bone

hyperextension

movement of a joint beyond its normal range of motion

male pelvic traits

• more vertical/less flared pelvis

• larger/rounder obturator foramen

• acute angle across pubic symphysis

• smaller diameter of pelvic inlet

female pelvic traits

• more flared pelvis

• smaller/triangular obturator foramen

• obtuse angle across pubic symphysis

• larger diameter of pelvic inlet

male skull traits

• larger, heavier appearance

• pronounced muscle attachment points

• oval/smaller eye orbits

• heavy/pronounced brow ridge

• u-shaped/broad chin

• angular jawline shape

female skull traits

• small, light appearance

• rounder/larger eye orbits

• smooth/flat brow ridge

• v-shaped/narrow chin

• rounded jawline shape

what normal bone metabolism depends on

• adequate minerals (calcium and phosphorus)

• vitamins A,C, and D

• hormonal levels (female = estrogen, males = testosterone)

• weight-bearing exercise

bone development in young children

• bones continue to grow both in length and diameter

• cartilage in ossification center are slowly converted to bone

• important to start building strong bones from a young age

when bone mass peaks

around 30 years of age

bone development during puberty

• estrogens and androgens begin being secreted in larger quantities

• cartilage in ossification centers at ends of long bone has been completely converted to bone

• epiphyseal line replaces epiphyseal plate

• growth spurt, widening of pelvis in females

bone development old age

• decreased collagen production (bones are more brittle/less flexible)

• reduction of weight bearing exercise, less active

• reduced production of specific hormones

osteoporosis

• condition of porous bones; bone resorption outpaces bone remodeling/deposition

• bone mass depleted, cannot withstand mechanical stresses of everyday life

• bones fracture easily

• shrinkage of vertebrae/height loss

• more common in females due to reduction of estrogen during menopause

testosterone

wanes only slightly in men as they age (less dramatic than drop in estrogen production for women)

osteoporosis treatments

• calcium supplements

• weight-bearing exercise

• drugs that mimic the beneficial effects of estrogen (promote bone deposition or inhibit activity of osteoclasts)

osteoporosis prevention

adequate calcium intake and exercise in earlier years