Lecture 1: Introduction Flashcards
How many bones are in the human body?
206
How many bones are in the appendicular skeleton?
126
How many bones are in the axial skeleton?
80
What is the last bone to ossify?
Clavicle
What are the 4 functions of bone and connective tissue?
- ) Supports mechanical loads
- ) Protects vital organs
- ) Contributes to mineral homeostasis
- ) Serves as a site for hematopoiesis
What are the 3 germ layers?
- ) Ectoderm
- ) Mesoderm
- ) Endoderm
From what germ layer is bone formed?
Mesodermal tissue
What does long bone begin as in the fetus?
Hyaline cartilage
What are the 2 types of bone formation?
#1 Intramembranous ossification #2 Endochondral ossification
What is intramembranous ossification?
Embryonic connective tissue transforms to bone
During intramembranous bone formation growth occurs by transformation of _____ to _____ without a _____ pre-modeling.
Mesenchymal cells, bone, cartilagenous
What type of bones are formed from intramembranous bone formation?
Flat bones
Intramembranous ossification increases the _____ of bone.
Diameter
What are 4 bone that are ossified in membrane?
- ) Parietal bone
- ) Temporal bone
- ) Upper occipital squamosa
- ) Frontal bone
What are the 2 forms of ossification within cartilage?
- ) Primary ossification
2. ) Secondary ossification
What is endochondral bone formation?
Growth occurs by the laying down of bone on a cartilagenous scaffold
What types of bones are formed by endochondral ossification?
Long and short tubular bones
_____ tissue from _____ transforms to bone.
Cartilagenous tissue, mesenchymal cells
Primary ossification _____ bone.
Lengthens
When does primary ossification occurs?
In utero
How many primary ossification centers are there?
3
Where are the 3 primary ossification centers?
Vertebral body center = 1
Posterior arches = 2 (one each side with growth plate at each end)
Primary ossification centers are usually fused at the midline by what age?
7
Where does secondary ossification occur?
Within the epiphyses and apophyses
What is a growth plate?
A thin plate of cartilage between the primary center and each secondary center
When does secondary ossification occur?
Post-partum
How many secondary ossification centers are there?
9
Where are the 9 secondary ossification centers?
Transverse processes = 2
Articular processes = 4
Spinous processes = 1
Ring apophyses = 2
Secondary ossification is associated with which type of bones?
Tubular bones
Vertebrae
Ethmoids
Inferior conchae
What is the apophysis?
A protuberance
Functions as the attachment site for ligaments and tendons
What is an enthesis?
Site of attachment of tendons and ligaments
The enthesis is highly ____ with high _____ activity.
Vascularized, metabolic
What are Sharpey fibers?
Outer fibrous extensions that attach the cortex to the periosteum
What does appositional bone growth do?
Maintain the caliber of bone
The periosteum serves as a source of vascular perfusion for what part of the cortex?
The outer third of the cortex
What are the 4 functions of the periosteum?
- ) Attaches to cortex via outer fibrous extensions called Sharpey’s fibers
- ) Maintains caliber of bone by appositional bone growth
- ) Provides a transitional zone of attachment for muscles, ligaments and tendons
- ) Serves as a source of vascular perfusion for the outer third of the cortex
Is the periosteum normally seen on x-rays?
No
The periosteum also includes potential functions for what 2 types of activity?
- ) Osteolytic
2. ) Osteoblastic
What is a callus?
A periosteal new bone formation
What is a callus an important sign of?
Healing fracture
What are 2 aka’s for the growth plate?
- ) Physis
2. ) Physeal plate
What are the 2 zones of the growth plate?
- ) Zone of cartilage production
2. ) Zone of transformation
What occurs at the zone of cartilage production?
Longitudinal bone growth
What occurs at the zone of transformation?
Cartilage-to-bone ossification
Where is the perichondral groove?
Surround circumference of the physeal plate
What is the perichondral groove made from?
Undifferentiated mesenchymal cells beneath a layer of fibrous tissue
What do mesenchymal cells serve as precursors for?
Cartilage cells
What is the perichondral groove responsible for?
Lateral growth of physeal plate
What 3 things help regulate bone growth?
- ) Hormones
- ) Blood supply
- ) Nutrition
What 3 things can increase the rate of bone growth?
- ) Growth hormones
- ) Sex hormones
- ) Increased blood circulation
What 4 things can decrease the rate of bone growth?
- ) Glucocorticoids
- ) Malnutrition
- ) Vitamin C deficiency
- ) Vitamin D deficiency
What does growth hormone do to control closure of the growth plate?
Nothing
What is the effect of excess androgens on the closure of growth plates?
Early closure
What is the effect of excess estrogen on the closure of growth plate?
Early closure
What is the effect of testosterone deficiency on the closure of growth plates?
Delays closure
What are the 2 main events of the growth plate closure?
- ) Slowing down of cartilage cell multiplication
2. ) Invasion of cartilage plate by blood vessels that eventually reach epiphyseal side of plate
What is the vascular supply of the physis in infants?
Small percent of metaphyseal blood vessels may penetrate the cartilagenous growth plate and supply the epiphysis
What is the vascular supply of the physis in children?
Vascular supply does not cross the growth plate (there is a barrier)
What is the vascular supply of the physis in adults?
No growth plate - so the blood supply to metaphysis and distal end of bone is continuous
What does the resting zone attach the growth plate to?
Epiphysis
What happens if the resting zone is injured?
Growth stops
What happens at the zone of proliferation?
Where bone is lengthened due to active growth of chondrocytes
What happens is there is cell death at the zone of proliferation?
Growth stops
What happens at the zone of hypertrophy?
Chondrocytes mature, no active growth
What is the weakest portion of the growth plate?
Zone of hypertrophy
What type of fractures can occur at the zone of hypertrophy?
Salter-Harris fractures
What happens at the zone of degeneration/ossification?
Chondrocytes die and ossification occurs
What does the zone of degeneration/ossification attach the growth plate to?
Metaphysis
Bone is what percent mineral (hydroxyapatite)?
70 percent
Bone is what percent collagen, water and cells?
30 percent
What are osteoblasts?
Bone forming cells
What are osteoclasts?
Bone remodeling and resorption
What are osteocytes?
Living cells of bone
Where can osteocytes be found?
Within lamellar bone
What is the function of osteocytes?
Bone metabolism and maintenance
What are 2 types of bone?
- ) Compact bone
2. ) Canellous bone
What is the description of compact bone?
Dense, ivory-like
What does compact bone form?
The outer shell
Where is compact bone thickest?
Diaphysis
Compact bone makes up what percent of total bone mass?
80 percent
What type of function does compact bone have?
Mechanical
What are 3 aka’s for cancellous bone?
- ) Trabecular bone
- ) Spongy bone
- ) Medullary bone
What does cancellous bone form?
The internal cavity of bone
What is the description of cancellous bone?
Thin interconnecting trabeculae
What are the 2 components of flat bone made from dense bony tissue?
- ) Inner table
2. ) Outer table
What is between the 2 layers of dense bony tissue?
Cancellous bone (red marrow)
What 2 parts of flat bones are covered with periosteum?
- ) The outer surface of the outer table
2. ) The under surface of the inner table
Where is bone marrow be located?
Lies in spaces between trabeculae of the cancellous bone
What is the function of bone marrow?
Provision of a continual supply of RBCs, WBCs and platelets
Bone marrow contains what types of cells?
- ) Red blood cells
- ) White blood cells
- ) Platelets
- ) Fat cells
Increasing the age does what to the amount of fatty marrow?
Increases
What affect does osteoporosis have on fatty marrow?
Fat cells are needed to replace the trabecular bone that is lost
Osteoporosis converts bone from _____ to _____.
Distal to proximal
