Unit 2 - Skeletal Flashcards
What 4 components does the skeletal system contain?
- Bones
- Cartilage
- Ligament
- Connective Tissue
Why is each bone considered an organ?
Bones contain: connective tissue, blood vessels, nerves, lymph vessels, cartilage, and connective tissue covering.
COMBINATION OF MANY TISSUE TYPES
What are the 6 skeletal system functions?
- Support
- Protection
- Mineral storage
- Triglyceride storage
- RBC + WBC formation
- Leverage
Where is the axial part of the body?
The middle or main part of the body.
Where is the appendicular part of the body?
Limbs and connections of limbs to the axial division.
Appendicular Girdle
Pectoral and pelvic connection points
In what division is the skull?
- cranium
- face
Axial
In what division is the hyoid?
Axial
In what division are the auditory ossicles?
Axial
In what division is the vertebral column?
Axial
In what division is the thorax?
- sternum
- ribs
Axial
In what division are the pectoral girdles?
- clavicle
- scapula
Appendicular
In what division are the upper limbs?
Appendicular
In what division is the pelvic girdle?
Appendicular
In what division are the lower limbs?
Appendicular
Describe the periosteum
- CT membrane covering external surface of bone
- Continuous with tendons + CT of joints
- Attached to bone matrix via perforating fibers
Describe the endosteum
- Lining inner surfaces of bone; marrow cavity, trabecullae of spongy bone, canals of compact bone
Describe the epiphysis
At the end of long bone. Contains red marrow.
Describe the metaphasis
The connection point between the epiphysis and diaphysis.
Describe the diaphysis
At the middle of a long bone. Contains yellow marrow.
Where can spongy bone be found?
Epiphysis
Describe the medullary cavity
Contains red and yellow marrow. Runs through epiphysis and diaphysis.
What are the endosteum and periosteum important for?
Bone growth and remodeling
What is the outer fibrous layer of the periosteum important for?
Protection
What is the inner osteogenic layer of the periosteum important for?
Growth and repair
Osteo means in correlation to…
Bone
Bone extracellular matrix is composed of…
Ground substance and fibers
What are osteogenic cells?
Immature starting cells; stem cells.
Formed from mesenchyme.
Develop into osteoblasts through mitosis and differentiation
What do osteoblasts do?
Build bone + bone matrix
What do osteocytes do?
Mature cells.
Maintain bone tissue.
What do osteoclasts do?
Break down material.
Functions in resorption + breakdown of bone matrix.
What two cells are important for bone remodeling?
Osteoblasts and osteoclasts
What is mesenchyme?
Embryonic connective tissue
What cells synthesize the organic components of the matrix?
Osteoblasts
Which cells initiate calcification?
Osteoblasts
What cells are involved in the maintenance of bone tissue?
Osteocytes
Which cells sense micro-damage and forces on bone to send repair signals?
Osteocytes
Which cells release enzymes and acids to degrade collagen and release minerals into blood?
Osteoclasts
Which cells are derived from myloid stem cells?
Osteoclasts
What are the organic components of bone ECM?
Ground substance and collagen fibers
What are the inorganic components of bone ECM?
Water and hydroxyapatite
What is hydroxyapatite?
Combination of minerals that fill spaces within collagen fibers.
What do collagen fibers contribute to bone?
Flexibility
What does hydroxyapatite contribute to bone?
Strength
If you remove minerals from bone, what happens?
Bone becomes rubbery, flexible
What happens if you remove collagen from bone?
Bone becomes brittle
What are trabeulae?
Irregular lattice of thin plates within spongy bone
Where can you find osteocytes?
Lacunae
What is the location of spongy bone?
- epiphysis of long bones
- surrounding marrow cavities
- flat, short, and irregular bones
What is the function of spongy bone?
- withstand forces from multiple directions
- lightens the skeleton
- contains red marrow for hemopoiesis
What is the location of compact bone?
- External layer of all bones
- Diaphysis of long bones
What is the function of compact bone?
To give long bones the ability to withstand forces along longitudinal axis
What is a functional unit of compact bone?
An osteon
What are soft spots on the skull called?
Fontanels
In infants, what are long bones made of?
Cartilage
How long do epiphyseal plates stay as cartilage?
Until the end of puberty
Before birth, what are bones composed of?
- Mesenchyme ; loose connective tissue
- Hyaline cartilage
What is ossification?
The replacement of connective tissue by bone
What type of ossification is from mesenchyme to bone?
Intramembranous
What type of ossification is from mesenchyme to cartilage to bone?
Endochondral
What process forms cranial bones?
Intramembranous ossification
What process forms the mandible?
Intramembranous ossification
What process forms the sternum?
Intramembranous ossification
What process forms the clavicle?
Intramembranous ossification
What process forms sesamoid bones?
Heterotropic
What are the steps to intramembranous ossification?
- deposition of osteoid into mesenchyme
- calcification of osteoid and osteocyte differentiation
- formation of spongy bone trabeculae and periosteum
- remodeling of outer spongy bone to compact bone.
What is calcification?
Deposition of calcium
What are the steps to endochondral ossification?
- cartilage model forms
- growth of cartilage model
- blood vessels penetrate model and stimulate differentiation of osteogenic cells into osteoblasts
- osteoblasts form bone on the outer surface of the model
- osteoblasts create a primary ossification center - bone replaces cartilage.
- osteoclasts create marrow cavity
- spongy bone remodeled to compact bone.
- around birth, secondary ossification center forms
- spongy bone replaces cartilage at the epiphyses with the exception of epiphyseal plates and articular cartilage
What happens in primary endochondral ossification?
- marrow cavity formed
- cartilage is replaced with bone
- occurs before birth
Where is primary endochondral ossification located?
Diaphysis
What happens in secondary endochondral ossification?
- no marrow cavity
- some cartilage is left for epiphyseal plates and articular cartilage
- occurs around the time of birth
Where is secondary endochondral ossification located?
epiphyses
What do X-rays not show?
Cartilage
What grows bone length in children?
Epiphyseal Plate
What is interstitial growth?
- Growth from within cartilage
- Growth in length @ epiphyseal plate
What is appositional growth?
- Growth at the outer surface
- Growth in width
During interstitial growth what do mesenchymal cells differentiate into?
Chondroblasts
During interstitial growth what do chondroblasts differentiate into?
Chondrocytes
What cell divides in interstitial growth?
Chondrocytes
At what level of the epiphyseal plate do chondrocytes divide?
Proliferating cartilage
At what level of the epiphyseal plate do cells increase in size?
Hypertrophic cartilage
What are the 3 steps for fracture repair?
- Fracture –> Hematoma
- Fibrocartilage callus –> Bony callus
- Bone remodeling
What 3 factors influence bone?
- Dietary
- Hormones
- Exercise
What two minerals influence bone?
Calcium and phosphorus
How does vitamin A influence bone?
stimulate activity of osteoblasts
How does vitamin C influence bone?
Needed for collagen synthesis
How does vitamin D influence bone?
Stimulates calcium absorption
How do vitamin K and B12 influence bone?
Needed for synthesis of bone proteins
What is the goal of calcium homeostatis?
To regulate blood calcium within a normal range
What is the normal range of blood calcium?
8.5 - 11.0 mg/dl
What are three reasons calcium is physiologically important?
- membrane excitability
- intracellular activity
- blood clotting
What are two ways calcium enters the blood?
Bone storage and intestinal absorption
How does calcium exit the body?
Kidney excretion
What function does calcitonin serve?
Decrease blood calcium
What is a stimulus for calcitonin?
High blood calcium
What hormone does the thyroid gland secrete?
Calcitonin
What is the target tissue of calcitonin?
Bone, kidney, and intestine
What is the goal of calcitonin?
To decrease blood calcium
What cell activity does calcitonin inhibit?
Osteoclasts
Inhibit bone resorption
What is a stimulus for the parathyroid hormone?
Low blood calcium
What excretes the parathyroid hormone?
Parathyroid gland
What are the target tissues of the parathyroid hormone?
Bone, kidney, and intestine
What is the goal of the parathyroid hormone?
To increase calcium
What cell does the parathyroid hormone stimulate?
Osteoclast
Increased bone absorption
What is the active form of vitamin D called?
Cacitriol
Describe vitamin D
A steroid hormone that is derived from cholesterol (hydrophobic)
What are the precursors to active vitamin D?
Cholecalciferol and Calcidiol
What cell does calcitriol (active vitamin D) stimulate?
Osteoclasts
What does calcitriol work with to stimulate absorption?
Parathyroid
What is the goal of calcitriol?
Increase blood calcium
Which people need higher levels of calcium per day?
Teenagers, pregnant women, and post menopausal women
Which two hormones act on osteoclasts?
Calcitonin and parathyroid
What two hormones act on osteoblasts?
Growth hormone (somatotropin) and estrogen/testosterone
What does growth hormone (somatotropin) stimulate?
Cell growth and protein synthesis (collagen)
What is the growth hormone stimulation process?
Stimulates insulin like growth factors –> Osteoblasts –> bone formation
Describe pituitary dwarfism
Low levels of growth hormone
–> slow epiphyseal growth
Describe achondroplastic dwarfism
normal GH levels, failure of cartilage growth at epiphyseal plate, only affects long bones
Describe pituitary giantism
hyper secretion of GH in childhood causing accelerated epiphyseal growth
Describe acromegaly
hyper secretion of GH after puberty causing appositional growth
What do estrogen and testosterone stimulate?
Osteoblasts
Bone formation
What hormones increase at puberty?
estrogen and testosterone
What do increased levels of estrogen and testosterone cause?
Bone growth / growth spurts
Bone will change in response to what?
Stress
What is the muscle pulling on bone force called?
Joint reaction
What is the impact for on bones called?
Ground reaction forces
Spongy bone is more metabolically active meaning…
it can respond to changes in mechanical loading more readily
Most likely places to fracture due to high spongy content:
Hip, wrist, spine
What does exercising early in life lead to?
Increase in peak bone mass
What does exercising later in life cause?
prevention of bone loss
Why does exercising prevent falls?
Improved strength and balance
Explain why exercising creates higher bone formation than absorption…
The mechanical force on bone signal the osteocytes to increase calcium and proliferation of osteoblasts
Describe osteoporosis
Porous bones
Reduced bone mass
Increased risk of fractures
How does bone change in osteoporosis?
The proportion of collagen and minerals is normal, but there’s a decrease in bone mass
What causes reduced bone mass?
Any factor that stimulates bone resorption or inhibits bone formation
Define articulation
A point of contact between bone, cartilage, and teeth
What is an immovable joint called?
synarthrosis
What is a slightly movable joint called?
Amphiarthrosis
What is a freely movable joint called?
Diarthrosis
What type of joints are sutures between skull bones?
Fibrous synarthroses
What types of joints are teeth in sockets?
Fibrous synarthroses
All diarthroses are what joints?
synovial
Describe fibrous joints
synarthrosis
Adjacent bones are joined by collagen fibers from one bone that penetrate into the other bone
Describe cartilaginous bones
Amphiarthrosis
Two bones linked by cartilage
What are the two types of cartilaginous joints?
Synchondroses and symphyses
Describe synovial joints
Diathrosis
A point where two bones are separated by a narrow, encapsulated space filled with lubricating synovial fluid.
Most are freely mobile.
What is the difference between chondroblasts and osteoblasts?
Chondroblasts - growth and development of cartilage
Osteoblasts - growth and development of bone
