Skeletal System Flashcards
consists primarily of water, which accounts for its resilience
cartilage
contains no nerves or blood vessels
cartilage
surrounded by a layer of dense irregular connective tissue, the perichondrium
cartilage
a layer of dense irregular connective tissue that surrounds the cartilage
perichondrium
3 types of cartilage in the body
hyaline cartilage, elastic cartilage, fibrocartilage
look like frosted glass when freshly exposed
hyaline cartilage
provide support with flexibility and resilience
hyaline cartilage
Chondrocytes are spherical
hyaline cartilage
types of hyaline cartilages
- articular cartilages
- costal cartilages
- respiratory cartilages
- nasal cartilages
which cover the ends of most bones at movable joints
articular cartilages
which connect the ribs to the sternum (breastbone)
costal cartilages
which form the skeleton of the larynx (voicebox) and reinforce other respiratory passageways
respiratory cartilages
which support the external nose
nasal cartilages
- the external ear
- the epiglottis
elastic cartilage
the flap that bends to cover the opening of the larynx each time we swallow
epiglottis
highly compressible with great tensile strength
fibrocartilages
consist of roughly parallel rows of chondrocytes alternating with thick collagen fibers
fibrocartilages
Locations:
• padlike cartilages (menisci) of the knee
• discs between vertebrae
fibrocartilages
locations of fibrocartilages
- padlike cartilages (menisci) of the knee
- discs between vertebrae
cartilage grows in two ways:
- appositional growth
- interstitial growth
cartilage-forming cells in the surrounding perichondrium secrete new matrix against the external face of the existing cartilage tissue
appositional growth
the lacunae bound chondrocytes divide and secrete new matrix, expanding the cartilage from within.
interstitial growth
how many bones in adult human skeleton
206
Based on location: The 206 named bones of the human skeleton are divided into two groups:
axial skeleton and appendiclar skeleton
forms the long axis of the body and includes the bones of the skull, vertebral column, and rib cage
axial skeleton
protect, support, or carry other body parts.
axial skeleton
axial skeleton includes the
bones of the skull, vertebral column and rib cage
functions of axial skeleton
protect, support, or carry other body parts.
consists of the bones of the upper and lower limbs and the girdles (shoulder bones and hip bones)
appendicular skeleton
help us move from place to place (locomotion) and manipulate our environment.
appendicular skeleton
appendicular skeleton consists of the
bones of the upper and lower limbs and the girdles (shoulder bones and hip bones)
functions of appendicular skeleton
help us move from place to place (locomotion)
and manipulate our environment.
classification of bones based on shape
- long bones
- short bones
- flat bones
- irregular bones
- sesamoid bones
- sutural bones
longer than they are wide, has a shaft plus two ends which are often expanded
long bones
roughly cube shaped, sesamoid bones
short bones
thin, flattened, and usually a bit curved
flat bones
have complicated shapes
irregular bones
functions of bones
- Support.
- Protection.
- Movement.
- Mineral and growth factor storage.
- Blood cell formation.
- Triglyceride (fat) storage.
- Hormone production.
classification of bones based on textures
compact bone and spongy bone
external layer
compact bone
internal layer made up of honeycomb of small needle-like or flat pieces called trabeculae
spongy bone
honeycomb of small needle-like or flat pieces called
trabeculae
general structure of long a typical long bone
- shaft
- bone ends
- membranes
the shaft
Diaphysis
Surrounds a central medullary cavity
Diaphysis
contains yellow marrow in adults
medullary cavity
the diaphysis surrounds a central
medullary cavity
the diaphysis contains
yellow bone marrow
bone ends
epiphysis
covers the joint surface of each epiphysis
articular (hyaline) cartilage
in between diaphysis and each epiphysis
epiphyseal line
a glistening white, double-layered membrane, covers the external surface except joints
Periosteum
richly supplied with nerve fibers and blood vessels
Periosteum
tufts of collagen fibers that secure the periosteum to the bone
Sharpey’s fibers
covers the external surface except joints
Periosteum
secures the periosteum to the bone
Sharpey’s fibers
covers internal bone surfaces
Endosteum
contains osteogenic cells that can differentiate into other bone cells
Endosteum
location of red marrow
within the trabecular cavities of spongy bone of long bones and flat bones
within the trabecular cavities of spongy bone of long bones and flat bones
red marrow
hematopoietic
red marrow
fats
yellow marrow
location of yellow marrow
in the medullary cavity
stem cell
osteogenic cells
matrix-synthesizing cell responsible for bone growth
osteoblast
mature bone cell that monitors and maintains the mineralized bone matrix
osteocyte
bone-resorbing cell
osteoclast
A unit of bone
Osteon (Haversian System)
- Opening in the center of an osteon
- Carries blood vessels and nerves
Central (Haversian) canal
- Canal perpendicular to the central canal
- Carries blood vessels and nerves
Perforating (Volkman’s) canal
looks like a poorly organized, even haphazard, tissue
spongy bone
align precisely along lines of stress and help the bone resist stress
trabeculae in spongy bone
trabeculae contain irregularly arranged
lamellae
trabeculae contain irregularly arranged lamellae and osteocytes interconnected by
canaliculi
in spongy bone, osteons are _______________
not present
Organic Components of bones
- cells
- osteoid
the organic part of the matrix
osteoid
osteoid is composed of
ground substance and collagen fibers
ground substance in osteoid is composed of
proteoglycans and glycoproteins
Inorganic Components in bones are
mineral salts, largely calcium phosphates
two types of bone development
- Endochondral ossification
- Intramembranous ossification
a bone develops by replacing hyaline cartilage.
Endochondral ossification
In endochondral ossification, a bone develops by replacing hyaline cartilage. The resulting bone is called a?
cartilage, or endochondral bone.
a bone develops from a fibrous membrane
Intramembranous ossification
in intramembranous ossification, a bone develops from a fibrous membrane and the bone is called a?
membrane bone
Except for the clavicles, essentially all bones below the base of the skull form by
endochondral ossification
what bones does endochondral ossification
all bones below the base of the skull
endochondral ossification forms essentially all bones below the base of the skull except for the
clavicles
Uses hyaline cartilage “bones” as models
endochondral ossification
endochondral ossification in a long bone
- bone collar forms around the diaphysis of the hyaline cartilage model
- cartilage in the center of the diaphysis calcifies and then develops cavities
- the periosteal bud invades the internal cavities and spongy bone forms
- the diaphysis elongates and a medullary cavity forms. secondary ossfication centers appear in the epiphyses.
- the epiphyses ossify. when completed, hyaline cartilage remains only in the epiphyseal plates and articular cartilages
forms the cranial bones of the skull (frontal, parietal, occipital, and temporal bones) and the clavicles
Intramembrenous ossification
Intramembrenous ossification forms the
cranial bones of the skull (frontal, parietal, occipital, and temporal bones) and the clavicles
Begins about week 8 of development
Intramembrenous ossification
intramembranous ossification growth
- ossification centers appear in the fibrous connective tissue membrane
- selected centrally located mesenchymal cells cluster and differentiate into osteoblasts, forming an ossification center that produces the first trabeculae of spongy bone - osteoid is secreted within the fibrous membrane and calcifies
- osteoblasts begin to secrete osteoid, which calcifies in a few days
- trapped osteoblasts become osteocytes - woven bone and periosteum form
- accumulated osteoid is laid down between embryonic blood vessels in a manner that results in a network (instead of concentric lamellae) of trabeculae called woven bone
- vascularized mesynchyme condenses on the external surface of the woven bone and becomes the periosteum - lamellar bone replaces woven bone, just deep to the periosteum. red marrow appears
- trabeculae just deep to the periosteum thicken. mature lamellar bone replaces them, forming compact bone plates.
- spongy bone (diploe), consisting of distinct trabeculae, persists internally and its vascular tissue becomes red marrow.
- long bones lengthen entirely by interstitial growth of the epiphyseal plate cartilage
- all bones grow in thickness by appositional growth
- most bones stop growing during adolescence
- some facial bones, such as those of the nose and lower jaw continue to grow almost imperceptibly throughout life
Post natal bone development
long bones lengthen entirely by
interstitial growth of the epiphyseal plate cartilage
all bones grow in thickness by
appositional growth
most bones stop growing during
adolescence
epiphyseal plate closure
- chondroblasts of the epiphyseal plates divide less often and the plates become thinner and thinner until they are entirely replaced by bone tissue
*epiphysis and diaphysis fuses
* about 18 years of age in females and 21 years of age in males
Growth in length of long bones
_________________________ beneath the periosteum secrete bone matrix on the external bone surface
osteoblasts
___________________________ on the endosteal surface of the diaphysis remove bone
osteoclasts
During infancy and childhood, the single most important stimulus of epiphyseal plate activity is
growth hormone
growth hormone is released by the
anterior pituitary gland
bone deposit and bone resorption occur at the surfaces of both the
periosteum and the endosteum
occur at the surfaces of both the periosteum and the endosteum
bone deposit and bone resorption
After resorption osteoclasts undergoes
apoptosis
- Osteoclasts move along a bone surface, digging depressions or grooves as they break down the bone matrix.
- osteoclast secretes lysosomal enzymes that digest the organic matrix and protons (H+)
- Resorption converts the calcium salts into soluble forms
- After resorption osteoclasts undergoes apoptosis
Bone Resorption
hoe does bone resorption occur
- Osteoclasts move along a bone surface, digging depressions or grooves as they break down the bone matrix.
- osteoclast secretes lysosomal enzymes that digest the organic matrix and protons (H+)
- Resorption converts the calcium salts into soluble forms
- After resorption osteoclasts undergoes apoptosis
- negative feedback hormonal loop that maintains Ca2+ homeostasis in the blood
- responses to mechanical and gravitational forces acting on the skeleton
- Calcium is absorbed from the intestine under the control of vitamin D metabolites
Control of Remodelling
Homeostatic Imbalance
what occurs if blood calcium level is high?
severe neuromuscular problems ranging from nonresponsiveness to inability to function
Homeostatic Imbalance
what occurs if blood calcium level is low?
Hypercalcemia
sustained high blood levels of Ca2+ can lead to undesirable deposits of calcium salts in the blood vessels, kidneys, and other soft organs, which may hamper their function
Hypercalcemia
holds that a bone grows or remodels in response to the demands placed on it
Wolff’s law
determine whether and when remodeling occurs in response to changing blood calcium levels.
Hormonal controls
determines where remodeling occurs.
Mechanical stress
Bone Repair
Fractures may be classified by:
- Position of the bone ends after fracture
- Completeness of the break
- Whether the bone ends penetrate the skin
Position of the bone ends after fracture:
- nondisplaced fractures
- displaced fractures
Completeness of the break:
- complete fracture
- incomplete fracture
Whether the bone ends penetrate the skin:
- open (compound) fracture
- closed (simple) fracture
the bone ends retain their normal position
nondisplaced fractures
the bone ends are out of normal alignment
displaced fractures
If the bone is broken through, the fracture is a
complete fracture
If the bone is NOT broken through, the fracture is a
incomplete fracture
if the bone ends penetrate the skin, it is a
open (compound) fracture
if the bone ends do NOT penetrate the skin, it is a
closed (simple) fracture
bone fragments into three or more pieces
comminuted
particularly common in the aged, whose bones are more brittle
comminuted
bone is crushed
compression
common in porous bones (ex. osteoporotic bones) subjected to extreme trauma, as in a fall
compression
ragged break occurs when excessive twisting forces are applied to a bone
spiral
common sports fracture
spiral
epiphysis separates from the diaphysis along the epiphyseal plate
epiphyseal
tends to occur where cartilage cells are are dying and calcification of the matrix is occuring
epiphyseal
broken bone portion is pressed inward
depressed
typical of skull fracture
depressed
bones break incompletely, much in the way a green twig breaks. only one side of the shaft breaks; the other side bends
greenstick
common in children, whose bones have relatively more organic matrix and are more flexible than those of adults
greenstick
Treatment involves ______________, the realignment of the broken bone ends.
reduction
the realignment of the broken bone ends
reduction
the physician’s hands coax the bone ends into position
closed (external) reduction
the bone ends are secured together surgically with pins or wires
open (internal) reduction
stages in the healing of a bone fracture
- a hematoma forms
- fibrocartilaginous callus forms
- bony callus forms
- bone remodeling occurs
includes a number of disorders in which the bones are poorly mineralized
Osteomalacia (“soft bones”)
symptom of Osteomalacia
pain when weight is put on the affected bones
is the analogous disease of osteomalacia in children is
Rickets
symptom of Rickets
Bowed legs and deformities of the pelvis, skull, and rib cage
Causes of Osteomalacia and Rickets
insufficient calcium in the diet or by a vitamin D deficiency
cure to Osteomalacia and Rickets
Drinking vitamin D– fortified milk and exposing the skin to sunlight (which spurs the body to form vitamin D) usually cure these disorders.
is hastily made and has an abnormally high ratio of spongy bone to compact bone
Pagetic bone
characterized by excessive and haphazard bone deposit and resorption
Paget’s Disease
causes weakening of the bones
Paget’s Disease
are most often involved and become increasingly deformed and painful
spine, pelvis, femur, and skull
cause of Paget’s Disease is
unknown but a virus may trigger it
rarely occurs before age 40
Paget’s Disease
prevents bone breakdown
Drug therapies include calcitonin
refers to a group of diseases in which bone resorption outpaces bone deposit
Osteoporosis
bones become so fragile
Osteoporosis
bone mass declines and the bones become porous and light
Osteoporosis
Osteoporosis is vulnerable to
compression fractures of the vertebrae, broken hip
- most often in the aged, particularly in postmenopausal women
- estrogen deficiency is strongly implicated in osteoporosis in older women
Osteoporosis
Risk Factors for Osteoporosis
- most often in the aged, particularly in postmenopausal women
- estrogen deficiency is strongly implicated in osteoporosis in older women
Several other factors can contribute to osteoporosis:
- Petite body form
- Insufficient exercise to stress the bones
- A diet poor in calcium and protein
- Abnormal vitamin D receptors
- Smoking (which reduces estrogen levels)
- Hormone-related conditions such as hyperthyroidism, low blood levels of thyroid-stimulating hormone, and diabetes mellitus
Treating Osteoporosis
- calcium and vitamin D supplements
- weight-bearing exercise
- hormone (estrogen) replacement therapy (HRT
Drugs for Treating Osteoporosis
- Bisphosphonates
- Selective estrogen receptor modulators (SERMs)
- statins
- denosumab
decrease osteoclast activity and number, and partially reverse osteoporosis in the spine
Bisphosphonates
such as raloxifene, mimic estrogen’s beneficial bone-sparing properties without targeting the uterus or breast.
Selective estrogen receptor modulators (SERMs)
drugs used to lower cholesterol levels, have an unexpected side effect of increasing bone mineral density up to 8% over four years
statins
significantly reduces fractures in men fighting prostate cancer and improves bone density in the elderly
monoclonal antibody drug denosumab
Preventing Osteoporosis
- Get enough calcium while your bones are still increasing in density
- Reduce intake of carbonated beverages and alcohol that leaches minerals from bone and decreases bone density
- get plenty of weight-bearing exercise (walking, jogging, tennis, etc.)
small bone commonly found embedded within a muscle or tendon near joint surfaces
sesamoid bones
also known as Wormian bones
Sutural bones
occur where the interlocking joints of the skull, called sutures, branch and isolate a small piece of bone
Sutural bones
interlocking joints of the skull
sutures
an unmineralized band bone matrix 10-12 micrometers wide
osteoid seam
marks areas of new matrix deposits by osteoblasts
osteoid seam
when Ca2+ product reaches a cirtain level, tiny crystals of _____________________ form
hydroxyapatite
cartilage cells undergo mitosis
proliferation zone
older cartilage cells enlarge
hypertrophic zone
matrix calcifies; cartilage cells die; matrix begings deteriorating; blood vessels invade cavity.
calcification zone
new bone forms
ossification zone
tiny canals readiating outward from a central canal to the lacunae of the first lamella and then from lamella to lamella
canaliculi
