Download Physiology Ch 5

Chapter 5 The Skeletal System
skeletal system
- consists of:
bones
joints
cartilage
ligaments
skelton - composed of 206 bones
2 divisions of the skeleton:
axial skeleton
- longitudinal axis of body
appendicular skeletal - bones of limbs and girdles
functions of the bones:
support
protection
movement
storage
blood formation
- internal framework
- supports and anchors all soft organs
- bones protect soft body organs
- skeletal muscles attach to bone by tendons and use the bones as levers to
move body
- fat is stored in bone cavities
- bone tissue stores minerals (calcium, phosphorus, etc.)
- calcium ions (Ca2+) needed in blood for the nervous system to
transmit messages, for muscles to contract, and for blood to clot
- hormones control movement of calcium to & from bones
- hematopoiesis (formation of blood cells) occurs in bone marrow cavities
2 types of osseous (bone) tissue:
compact
- dense; looks smooth
spongy
- made of needlelike bone pieces; has lots of open space
4 groups of bones (based on shape):
long bones
- longer than they are wide
- shaft with heads at both ends
- made mostly of compact bone
- examples: all bones of limbs (except wrist & ankle bones)
short bones
- generally cube-shaped
- made mostly of spongy bone
- examples: wrist & ankle bones
sesamoid bones
- special type of short bone
- form within tendons
- example:
patella (kneecap)
flat bones
- thin, flat, and usually curved
- composed of spongy bone sandwiched by 2 thin layers of compact bone
- examples: most skull bones, ribs, and sternum (breastbone)
irregular bones
- don’t fit in a preceding group
- examples: vertebrae, hip bones
long bone structure
diaphysis
periosteum
Sharpey’s fibers
epiphyses
articular cartilage
epiphyseal line
epiphyseal plate
medullary cavity
bone markings
- shaft
- made of compact bone
- fibrous CT membrane which covers the diaphysis
- AKA perforating fibers
- CT fibers that attach periosteum to bone
- ends of long bones
- composed of spongy bone enclosed by a thin layer of compact bone
- covers epiphyses (no periosteum)
- hyaline cartilage
- smooth, slippery surface; decreases friction at joints
- thin line separating epiphysis from diaphysis
- remnant of the epiphyseal plate
- AKA growth plate
- plate of hyaline cartilage in a young growing bone
- lengthwise growth of a long bone occurs here
- by end of puberty, they are replaced by bone leaving epiphyseal lines
- cavity of the shaft
- primarily stores adipose tissue (yellow marrow)
- contains red marrow in infants (blood cells made)
- in adults red marrow is confined to spongy bone cavities
- bumps, holes, and ridges
- reveal where muscles, tendons, and ligaments were attached and where
nerves and blood vessels passed
- 2 types:
projections
- grow out from bone surface
depressions - indentations in the bone
microscopic long bone structure
osteocytes
- bone cells; found in lacunae
lacunae
- tiny cavities in bone matrix which contain osteocytes
lamellae
- concentric circles of bone tissue containing lacunae
- surround central canals
central canals
- AKA Haversian canals
- run lengthwise through matrix
- contain blood vessels and nerves
osteon
- AKA Haversian system
- consists of central canal and surrounding rings (lamellae)
canaliculi
- tiny canals that radiate outward from central canals to lacunae
- allow bone cells to receive nutrients
perforating canals
- AKA Volkmann’s canals
- run at right angles to the shaft
- allow communication between inside and outside of bone
bone tissue
- very hard (due to calcium salts)
- flexible (due to collagen fibers)
bone formation
embryo skeleton
young child
- mostly hyaline cartilage
- cartilage has been replaced by bone
- hyaline cartilage is “ossified” into bone
- 2 phases:
* hyaline cartilage is covered with a bone matrix by osteoblasts (bone-forming cells)
* cartilage is digested away forming medullary cavity
ossification
long bone growth
- controlled by hormones (growth hormone, sex hormone)
- ends during adolescence (epiphyseal plates completely converted to bone)
parathyroid hormone (PTH) - produced by parathyroid glands when blood levels of calcium are low
- activate osteoclasts (bone-destroying cells)
osteoclasts
- break down bone matrix and release calcium into blood
stresses of muscle pull and gravity
physically inactive people
- cause bones to become thicker and form projections
to increase their strength
- bones loses mass & atrophy because they are no longer subjected to stress
rickets - disease of children
- bones don’t calcify due to lack of calcium or vitamin D (needed for calcium absorption)
- bones soften and legs become bowed
bone fractures - breaks
- during youth, most result from trauma during sports or car accidents
- more frequent in old age
closed (simple) fracture
open (compound) fracture
common fractures:
comminuted
compression
depressed
impacted
spiral
greenstick
- bone breaks cleanly; doesn’t penetrate the skin
- ends of bone penetrate skin
- bone breaks into fragments (common in old age)
- bone is crushed (common in old age)
- broken bone portion is pushed inward (typical in skull fractures)
- ends of broken bones are pushed into each other
- common when trying to break a fall with outstretched arms
- excessive twisting forces cause a ragged break (common in sports)
- incomplete break, like a green twig (common in children)
treatment of a broken bone
reduction
- bone is realigned
- doctor uses his hands with closed fractures
- surgery necessary with open fractures
immobilization
- cast or traction
healing time for a simple fracture
bone healing
hematoma forms
fibrocartilage callus forms
bony callus forms
bone remodeling occurs
axial skeleton - 3 parts:
- 6-8 weeks (longer for larger bones and in the elderly)
- due to broken blood vessels
- contains cartilage and bone matrix and cartilage fibers
- made by CT cells
- closes the gap and “splints” the bone
- made of spongy bone by osteoblasts
- replaces fibrocartilage callus
- bony callus remodeled into a strong permanent patch
skull
vertebral column
bony thorax
skull - cranium encloses and protects brain
- facial bones hold eyes in place and allow facial muscles to produce facial expressions
most bones joined together by sutures (immovable joints)
sinuses - air spaces in bone
cranium
- composed of 8 flat bones:
frontal bone
- forms forehead and superior part of each orbit (eye socket)
parietal bones
- paired bones
- form most of superior and lateral walls of cranium
temporal bones
- paired bones
- inferior to parietal bones on each side
- important markings:
external acoustic meatus
- ear canal
styloid process - needlelike just below EAM
- many neck muscles attach here
zygomatic process
- joins cheek bone
mastoid process
- below and behind EAM
- neck muscles attach here
jugular foramen
- where occipital and temporal bones meet
- jugular vein passes through
carotid canal
- anterior to jugular foramen
- carotid artery passes through
occipital bone
- forms floor and back wall of skull
- important markings:
foramen magnum
- large opening at base of occipital bone
- spinal cord passes through
occipital condyles
- rockerlike projections
- rest on first vertebrae
sphenoid bone
- butterfly-shaped
- forms part of cranial floor and eye orbits
- important markings:
sella turcica - depression that holds pituitary gland
optic canals - optic nerve passes from brain to eyes
ethmoid bone
- anterior to sphenoid
- forms roof of nasal cavity and part of orbits
facial bones - 14 bones (12 are paired)
maxillary bones
- form upper jaw and anterior hard palate
- carry the upper teeth
- paranasal sinuses
- drain into nasal passages
- throat infections can spread here causing sinusitis
palantine bones
- form posterior hard palate
- cleft palate
zygomatic bones
- cheekbones
- also form part of orbits
lacrimal bones
- form part of orbits (fingernail size)
- each has a groove for the passage of tears
nasal bones
- form bridge of nose
vomer bone
- forms nasal septum
inferior nasal conchae - part of nasal cavity
mandible
- lower jaw
- joins temporal bones on sides of face
- carries the lower teeth
hyoid bone
- “Adam’s apple”
- not really part of skull
- suspended in midneck region
- moveable base for tongue and attachment point for neck muscles that raise
and lower larynx when we swallow or speak
fontanels
- soft spots in fetal skull
- fibrous membranes not yet turned to bone
- allow skull to be compressed during birth
- also allow for brain growth
vertebral column
- AKA spine
- flexible, curved structure extending from skull to pelvis
- made of 26 irregular bones connected by ligaments
- spinal cord runs through its central cavity
vertebrae
- 24 of them
intervertebral discs - pads of fibrocartilage
- cushion vertebrae and absorb shocks
- herniated disc (slipped disc) - intervertebral disc protrudes
- may cause numbness and excruciating pain
vertebrae structure:
body
- disklike; bears weight
arch
- arch extending from the body
foramen
- spinal cord passes through
transverse processes - lateral projections from arch
spinous process
- projection from posterior part of arch
articular processes
- allow vertebra to form joints with adjacent vertebrae
cervical vertebrae
- 7 of them  C1 – C7 (think: breakfast at 7AM)
- form neck region of spine
atlas (C1)
- holds skull
- no body
axis (C2)
- acts as a pivot for atlas
- has odontoid process (pivot point)
thoracic vertebrae
- 12 of them  T1 – T12 (think: lunch at 12 noon)
lumbar vertebrae
- 5 of them  L1 – L5 (think: dinner at 5 PM)
sacrum - formed by the fusion of 5 vertebrae
- joins with L12 above and the coccyx below
- forms posterior wall of pelvis
- joins with hip bones (sacroiliac joints)
coccyx - formed by the fusion of 3-5 vertebrae
- “tailbone”
bony thorax - made of sternum, ribs, and thoracic vertebrae
- AKA thoracic cage
sternum
- breastbone
- forms from the fusion of 3 bones:
manubrium
- superior
body
- middle
xiphoid process
- inferior
- bony landmarks:
jugular notch
- concave upper border of manubrium
sternal angle
- manubrium and body meet at a slight angle
xiphisternal joint
- where body & xiphoid process meet
ribs
- 12 pairs
- forms wall of bony thorax
- all attach to vertebral column and then curve downward and toward anterior body
true ribs
- first 7 pairs
- attached to sternum by costal cartilages
false ribs
- next 5 pairs
- attached to sternum indirectly by cartilage
floating ribs - last 2 pairs
- not attached to sternum
appendicular skeleton - bones of the shoulder girdle, upper limbs, pelvic girdle, and lower limbs
shoulder girdle (pectoral girdle)
very flexible yet easily dislocated
consists of:
clavicle
scapula
- collarbone
- attaches to manubrium of sternum and scapula
- acts as a brace holding arm away from thorax
- shoulder blade
- loosely held in place by muscles
- glenoid cavity
- shallow socket that receives head of arm
bone
upper limbs
30 bones form each upper limb (arm, forearm, and hand)
arm
humerus
- heads fits into glenoid cavity
forearm
radius - lateral to ulna (on thumb side) in anatomical position
- connected to ulna by interosseous membrane
ulna - medial to radius in anatomical position
hand
carpals - 8 of them (2 rows of 4)
- form the wrist
metacarpals - 5 of them
- form palm of hand
- heads form knuckles
phalanges
- 14 of them
- form fingers
- 3 in each finger (proximal, medial, and distal)
- 2 in the thumb (proximal and distal)
pelvic girdle
formed by 2 coxal bones (hip bones)
bears the weight of upper body
each hip bone consists of:
ilium
- connects to sacrum posteriorly
- large, flaring bone
ischium
- inferior part of hip bone (“sit-down bone”)
pubis
- pubic bone
- most anterior part of hip bone
acetabulum - deep socket formed at site where the 3 hip bones join
- head of femur fits here
lower limbs
30 bones form each lower limb
thigh
femur - thigh bone
- heaviest, strongest bone in body
- head fits into acetabulum of hip bone
- neck of femur
- frequently fractured in elderly
patella - kneecap
leg
tibia
- shinbone
- larger and more medial than fibula
- forms inner bulge of ankle
- connected to fibula by interosseous membrane
fibula - thin bone
- forms outer bulge of ankle
foot
tarsals
metatarsals
phalanges
- 7 of them
- form back of foot (tarsus)
calcaneous
- heelbone
- 5 of them
- form sole of feet
- 14 of them
- form toes (3 in each toe, except great toe which has 2)
joints
joints - AKA articulations
- hold bones together
- give skeleton mobility
types of joints (based on function)
synarthroses - immovable joints
amphiarthoses - slightly immovable joints
diarthroses
- freely movable joints
types of joints (based on structure)
fibrous joints
- fibrous tissue separates bones
- immovable
- example:
sutures of the skull - CT fibers bind bones tightly
cartilaginous joints - cartilage separates bones
- most are slightly immovable (some immovable)
- examples: pubic symphysis
- joins pubic bones together
intervertebral joints - fibrocartilage discs join vertebrae
together
epiphyseal plates
- hyaline cartilage
joints between ribs and sternum
synovial joints
- bones separated by a cavity filled with synovial fluid
- freely movable
synovial joints - all have 4 features:
articular cartilage
fibrous articular capsule
joint cavity
- hyaline cartilage covering bone ends
- sleeve of fibrous CT enclosing joint surfaces
- lined with a synovial membrane
- enclosed by the capsule
ligaments
bursae
- contains synovial fluid for lubrication
- reinforce joint
- flattened sacs lines with a synovial membrane & filled with synovial fluid
- often part of synovial joints
tendon sheaths - long bursa that wraps around a tendon subject to friction
types of synovial joints
plane joint
- short gliding movements
- example:
intercarpal joints of the wrist
hinge joint
- angular movement in 1 plane (back-and-forth)
- examples: elbow joint
ankle joint
joints between phalanges of the fingers
pivot joint
- rounded end of 1 bone fits into a sleeve or ring of bone
- example:
atlas and dens of the axis
condyloid joint
- moving bone moves from side to side and back and forth
- example:
knuckle joints (metacarpophalangeal)
saddle joint
- moving bone moves from side to side and back and forth
- example:
thumb joint ( carpometacarpal)
ball-and-socket joint - spherical head of 1 bone fits into a socket of another bone
- allow movement in many directions
- most freely moving joints
- examples: shoulder
hip
dislocation
reduction
- bones is forced out of its normal position
- process of returning the bone to its proper position
- should only be done by a physician
bursitis - inflammation of bursae or synovial membrane
sprain - ligaments or tendons reinforcing a joint are stretched & damaged
- extremely painful
- heal slowly (poor blood supply)
arthritis
- 1 out of 7 Americans suffer from it
- over 100 inflammatory or degenerative diseases that damage the joints
- joints are painful, stiff, and swollen
osteoarthritis - most common form of arthritis
- affects the aged
- joint cartilage softens and breaks down over the years
- exposed bone can thicken to form bone spurs which restrict movement
- progresses slowly and is irreversible
- rarely crippling
rheumatoid arthritis
gout
- chronic inflammatory disease
- autoimmune disease
- many joints affected (especially fingers, wrists, ankles, & feet)
- bones ends can become fused and/or deformed
- may be severely crippling
- uric acid accumulates in blood and is deposited as needle-like crystals in the joints
- agonizingly painful
- often affects the great toe
osteoporosis
- bone-thinning disease
- bones become fragile
- vertebrae often collapse resulting in a hunched-over posture