The Skeleton System Flashcards
the entire framework of bones and cartilage
The skeletal system
a detailed study of the structure of bones, skeletal elements, teeth, morphology, function, disease, pathology, and the process of ossification of the bones
Osteology
Functions of the skeletal system
- support
- protection
- assistance in movement
- mineral homeostasis
Site of attachment for tendon and ligament
Support
Encloses the organs of the cranial and thoracic cavities
Protection
Allows for a range of movement over certain joints
Assistance in movements
stores minerals like calcium and phosphate (in extracellular matrix)
mineral homeostasis
red bone marrow helps make:
red and white blood cells
- in the medullary cavity
- contained in yellow bone marrow
triglyceride storage
long bone
humerus
flat bone
sternum
short bone
triquetrol
irregular bone
vertebra
Parts of the long bone
- Diaphysis
- Epiphysis
- Articular Cartilage
- Periosteum
- Medullary Cavity
- Endosteum
lining the cavities inside the bone
endosteum
lining that wraps around the bond
periosteum
Four types of cells in bone tissues:
- Osteogenic cells
- Osteoblasts
- Osteocytes
- Osteoclasts
- Found on the surface of a bone and in the periosteum
- Capable of mitotic division
Osteogenic Cells
- Bone forming cells
- Found in the margins of bone
Osteoblasts
- mature bone cells
- found in the lacunae
Osteocytes
*Have gaps that allow them to communicate with each other
- bone dissolving cells
- contain many nuclei (fusion of many mesodermal cells)
Osteoclasts
When the body is low on calcium, osteoclast levels do what?
Increase
What makes up the composition of bone’s matrix?
- Collagen fibers
- Hydroxyapatite (Calcium and Phosphate)
Hydroxyapitate
Calcium and Phosphate
Bone matrix has _____ water and _____ salts
less water and more salts
Percent composition of bone:
- 25% water
- 50% salt
- 25% fibrous protein
Few spaces between the hard components
Compact Bone
makes the external layer of all bones
Compact Bone
80% of bones are ____, the rest is _____
compact bone; spongy bone
Compact bone provides:
- Strength
- Site of attachment for tendons and ligaments
site of attachment for tendons and ligaments
compact bone
Parts of compact bone matrix:
- osteon
- central canal
- perforating canal
- osteocyte
- lacuna
- bone matrix
- canaliculus
extensions of membrane between osteocyte
canaliculus
What is another word for osteons?
Haversian Systems
Bones are arranged in:
Haversian Systems
Bone that does not contain true osteons
Spongy Bone
Spongy bone is made up of:
lamellae that are arranged in a lattice of thin columns of bones
spaces between them filled with red bone marrow
Trabeculae
Arranged to resist stress from many directions
Trabeculae
What occurs in the spongy bone of the long bones?
Hematopoiesis
Hormone that stimulates blood cell production
Hematoprotein
Formation of bone on a connective tissue base
Ossification/osteogenesis
- mostly cartilage
- slowly replaced by bone
Embryo Skeleton
There are two possible ways for ossification:
- Intramembraneous ossification
- Endochondral ossification
type of ossification where bones begin with sheet-like layers of connective tissues
- Broad, flat bones
- Intramembraneous bone
Intramembraneous Ossification
*Skull bones (except mandible)
Type of ossification where bones begin as hyaline cartilage, form models for future bones
-most bones of the skelton
Endochondral Ossification
*Chond= “Cartilage”
Center of ossification
osteoblasts
Osteocytes develop in the spaces of the _____
bone matrix
Bone matrix develops into:
trabeculae to form spongy bones
Mesenchyme (on the outside):
condense to make the periosteum
Endochondral Ossification beings:
in the second month of development
Uses hyaline catilage “bones” as models for bone construction
Endochondral Ossification
Requires breakdown of hyaline cartilage prior to ossification
Endochondral ossification
Stages of Endochondral Ossification:
- Formation of bone collar
- Caviation of hyaline cartilage
- Invasion of internal cavities by the periosteal bud, and spongy bone formation
- Formation of the medullary cavity; appearance of secondary ossification centers in the epiphyses
- Ossification of the epiphyses, with hyaline cartilage remaining only in the epiphyseal (growth) plates
- Cartilage cells undergo mitosis, pushing the epiphysis away from the diaphysis
- Followed by a hypertrophic zone
Growth Zone
where older cartilage cells enlarge
hypertrophic zone
In a transformation zone, the matrix becomes
calcified
-the matrix becomes calcified, cartilage cells die and the matrix begins to deteriorate
Transformation (calcification) zone
new bone formation occurs
Ossification (osteogenic) zone
Cartilage continually grows and is replaced by bone
Growth in legnth
Bone is reabsorbed and added by appositional growth
Remodeling
During infancy and childhood, epiphyseal plate activity is stimulated by:
growth hormone
During puberty, testosterone and estrogen:
- initially promote adolescent growth spurts
- Cause: masculinization and feminization of specific parts of the skeleton
Later, hormones induce epiphyseal plate closure:
ending longitudinal bone growth
What causes masculinization and feminization of specific parts of the skeleton?
Testosterone and Estrogen
Adjacent osteoblasts and osteoclasts that deposit and reabsorb periosteal and endosteal surfaces
Remodling units
Occurs where bone is injured or added strength is needed
Bone Deposition
Bone Deposition requires a diet that is rich in:
- Proteins
- Vitamins A, C, and D
- Calcium, phosphorus, magnesium, and manganese
Production of collagen fibers
Vitamin C
Help promote activity associated with osteoblasts/osteoclasts
Vitamin A
Helps body absorb Calcium
Vitamin D
What do bones store Calcium for:
- transmission of nerve impulses
- muscle contractions
- blood coagulation
- secretion by: glands and nerve cells
- cell division
What does the Parathyroid do?
4 masses release PTH (Parathyroid Hormone) is released when blood calcium levels are too low. Hormone stimulates osteoclast activity to break down the bone’s matrix and puts the Ca++ back into the blood
Thyroid releases _____ when blood calcium is too high. Stimulates osteoblasts to take Ca++ out of the blood and add to the bone matrix
Calcitonin
Bone fractures are classified by:
- the position of the bone ends after fracture
- the completeness of the break
- the orientation of the bone to the long axis
- whether or not the bone ends penetrate the skin
A break in any bone
Fracture
- Compound Fracture
- Bone breaks through soft tissues
Open fracture
- Simple fracture
- Bone does not break through the soft tissue
Closed fracture
- bone fragments into three or more pieces
- common in the elderly
Comminuted fracture
- incomplete fracture where one side of the bone breaks and the other side bends
- common in children, because children still have a lot of cartilage
Greenstick fracture
One part of the bone is crushed into another part of the bone
Impacted Fracture
Epiphysis separates from diaphysis along the epiphyseal line
-occurs where cartilage cells are dying
Epipheseal Fracture
A fracture that occurs at the distal end of the radius
Colle’s Fracture
- Hairline Fracture
- Type of incomplete fracture
- Caused by: repeated or unusual stress often to a weight bearing bone
Stress Fracture
Steps in bone repair:
- Form a fracture hematoma
- Fibrocartilagenous callus formation
- Bony callus formation
- Bone remodling
What happens to the shape of bones when they repair themselves?
Width is greater than it was at the beginning and this will persist for the rest of their lives
Decreases in sex steroids causes a:
decrease in bone mass
Bones grow:
from birth through adolescense
Group of diseases in which bone reabsorption outpaces bone deposit
osteoporosis
During osteoporosis, ____ is most vulnerable
spongy bone of the spine
Osteoporosis occurs most often in:
Post-menopausal women
Bones become so fragile that sneezing or stepping off a curb can cause fracture:
osteoporosis
Treatments for osteoporosis:
- Calcium and Vitamin D supplements
- Increase weight-bearing exercise
- Hormone (estrogen) replacement therapy (HRT) slows bone loss
- Natural progesterone cream prompts new bone growth
- Statins increase born mineral density
- Bones are inadequately mineralized, causing softened, weakened bones
- Main symptom is: pain when weight is put on the affected bone
- Caused by insufficient: Calcium in diet, or Vitamin D deficiency
*In adults
Osteomalacia
- Bones of children are inadequately mineralized, causing softened, weakened bones
- Bowed legs and deformities of pelvis, skull, and rib cage are common
- Caused by insufficient calcium in the diet, or by vitamin D deficiency
Rickets
Why do isolated cases of Rickets occur?
Infants of breastfeeding mothers who are deficient in Vitamin D will also be deficient in Vitamin D and develop rickets
- characterized by excessive bone formation and breakdown
- bone with an excessively high ratio of woven bone to compact bone is formed
- Causes spotty weakening of bones
- Osteoclast activity wanes, but osteoblast activity continues to work
Paget’s Disease
Where is Paget’s disease localized?
spine, pelvis, femur, and skull
What is the treatment for Paget’s disease?
the drugs Didronate and Fosamax
- Person is very short but has normal body proportions
- Human growth hormone stimulates growth along the epiphyseal plates (without this hormones, this disease occurs)
Pituitary Dwarfism
- An excess of human growth hormone is released
- Before epiphyseal plates seal, height may be up to 8 feet
Pituitary Gigantism
- Excess secretion of human growth hormone in adults
- Causes enlargement of hands, feet, and jaw
Acromegaly
Produce membranes and cartilages that form the embryonic skeleton
embryonic mesenchymal cells
____ cells give rise to embryonic mesenchymal cells
Mesoderm
The _____ ossifies at a known rate
embryonic skeleton
fetal age is easily determined from ____
sonograms
At birth, most long bones are ____
ossified
*except at the epiphyseal plate
By age ____, nearly all bones are completely ossified
25
A single gene codes for:
- the tendency to accumulate bone mass early in life
- the risk for osteoporosis later in life
in old age, bone absorption
outpaces bone growth
