Orthopedic Physiology Flashcards
Stages of Intramembranous Ossification? 4
- An ossification center appears in the fibrous connective tissue membrane
- Bone matrix is secreted within the fibrous membrane
- Woven bone and periosteum form
- Bone collar of compact bone forms, and red marrow appears
How does the ossification center form?
Bone matrix is secreted within the fibrous membrane
- What is another name for bone matrix?
- What secretes this? It is mineralized in what time period?
- Trapped osteoblasts become what?
Woven bone and periosteum form:
- Accumulating osteoid is laid down b/w embyronic blood vessels which form a random network. The result is?
2 What becomes the periosteum?
Bone collar of compact bone forms, and red marrow appears:
- Trabeculae just deep to the periosteum thicken, forming a woven bone collar that is later replaced with what?
- What persists internally and its vascular tissue becomes red marrow?
Endochondral Ossification
- Begins when?
- Uses what as models for bone construction?
- Requires what prior to ossification?
- Begins in the second month of development
- Uses hyaline cartilage “bones”
- Requires breakdown of hyaline cartilage prior to ossification
Stages of Endochondral Ossification
5
- Formation of bone collar
- Cavitation of the 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 plates
Postnatal Bone Growth: Growth in length of long bones
- Cartilage on the side of the where is relatively inactive?
- Cartilage abutting the shaft of the bone organizes into a pattern that allows what?
- Cells of the epiphyseal plate proximal to the resting cartilage form three functionally different zones: what are they?
- epiphyseal plate closest to the epiphysis
- fast, efficient growth
3.
- growth,
- transformation
- osteogenic development
Functional Zones in Long Bone Growth
Define the following zones:
- Growth zone?
- Transformation?
- Osteogenic zone?
- Growth zone – cartilage cells undergo mitosis, pushing the epiphysis away from the diaphysis
- Transformation zone – older cells enlarge, the matrix becomes calcified, cartilage cells die, and the matrix begins to deteriorate
- Osteogenic zone – new bone formation occurs
Long Bone Growth and Remodeling
- Growth in length – cartilage continually grows and is replaced by what?
- What is Remodeling?
- bone
- – bone is resorbed and added by appositional growth as shown
Where are the places where cartilage is grown? 2 And then replaced by bone? 2
Where is bone reabsorbed? 2 Where is bone added and by what?
What are the 4 stages of appositional bone growth?
Hormonal Regulation of Bone Growth During Youth
- During infancy and childhood, epiphyseal plate activity is stimulated by what?
- What changes occur during puberty because of estrogen and testosterone in the skeleton system? 3
- Growth hormone
2.
- Initially promote adolescent growth spurts
- Cause masculinization and feminization of specific parts of the skeleton
- Later induce epiphyseal plate closure, ending longitudinal bone growth
What are remodeling units?
§Remodeling units – adjacent osteoblasts and osteoclasts deposit and resorb bone at periosteal and endosteal surfaces
Bone Deposition
- Occurs where?
- Requires a diet rich in what? 8
- What is essential for mineralization of bone?
- Sites of new matrix deposition are revealed by the what? 2 (Describe what these are)
- bone is injured or added strength is needed
- protein, vitamins C, D, and A, calcium, phosphorus, magnesium, and manganese
- Alkaline phosphatase
4.
- Osteoid seam – unmineralized band of bone matrix
- Calcification front – abrupt transition zone between the osteoid seam and the older mineralized bone
Bone Resorption
- Accomplished by what?
- What are reabsorption bays?
- Resorption involves osteoclast secretion of? 2
- Dissolved matrix is transcytosed scross the osteoclast’s cell where it is secreted where?
- Accomplished by osteoclasts
- Resorption bays – grooves formed by osteoclasts as they break down bone matrix
- Resorption involves osteoclast secretion of:
- Lysosomal enzymes that digest organic matrix
- Acids that convert calcium salts into soluble forms - into the interstitial fluid and then into the blood
Importance of Ionic Calcium in the Body
Calcium is necessary for? 5
- Transmission of nerve impulses
- Muscle contraction
- Blood coagulation
- Secretion by glands and nerve cells
- Cell division
Control of Remodeling: Two control loops regulate bone remodeling?
- Hormonal mechanism maintains calcium homeostasis in the blood
- Mechanical and gravitational forces acting on the skeleton
Hormonal Mechanism
- Rising blood Ca2+ levels trigger the thyroid to release what?
- Calcitonin stimulates what?
- Falling blood Ca2+ levels signal what?
- PTH signals osteoclasts to do what? 2
- calcitonin
- calcium salt deposit in bone
- the parathyroid glands to release PTH
4.
- degrade bone matrix
- release Ca2+ into the blood
Response to Mechanical Stress
- What is wolff’s law?
- Observations supporting Wolff’s law include? 2
- Wolff’s law – a bone grows or remodels in response to the forces or demands placed upon it
- Observations supporting Wolff’s law include
- Long bones are thickest midway along the shaft (where bending stress is greatest)
- Curved bones are thickest where they are most likely to buckle
Response to Mechanical Stress
- Trabeculae form along lines of what?
- Large, bony projections occur where?
- stress
- where heavy, active muscles attach
Bone fractures are classified by: 4
- 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 bones ends penetrate the skin
Types of Bone Fractures: Describe the following
- Nondisplaced?
- Displaced?
- Complete?
- Incomplete?
- Linear?
- Transverse?
- Compound/open?
- Simple/closed?
- Nondisplaced – bone ends retain their normal position
- Displaced – bone ends are out of normal alignment
- Complete – bone is broken all the way through
- Incomplete – bone is not broken all the way through
- Linear – the fracture is parallel to the long axis of the bone
- Transverse – the fracture is perpendicular to the long axis of the bone
- Compound (open) – bone ends penetrate the skin
- Simple (closed) – bone ends do not penetrate the skin
Common Types of Fractures: Describe the following types
- Comminuted?
- Spiral?
- Depressed?
- Compression?
- Epiphyseal?
- Greenstick?
- Comminuted – bone fragments into three or more pieces; common in the elderly
- Spiral – ragged break when bone is excessively twisted; common sports injury
- Depressed – broken bone portion pressed inward; typical skull fracture
- Compression – bone is crushed; common in porous bones
- Epiphyseal – epiphysis separates from diaphysis along epiphyseal line; occurs where cartilage cells are dying
- Greenstick – incomplete fracture where one side of the bone breaks and the other side bends; common in children
Stages in the Healing of a Bone Fracture
First: Hematoma Formation
Describe the three steps in this?
- Torn blood vessels hemorrhage
- A mass of clotted blood (hematoma) forms at the fracture site
- Site becomes swollen, painful, and inflamed
Stages in the Healing of a Bone Fracture:
Second: Fibrocartilaginous callus formation
Describe the three steps in this?
- Fibrocartilaginous callus forms
- Granulation tissue (soft callus) forms a few days after the fracture
- Capillaries grow into the tissue and phagocytic cells begin cleaning debris
Stages in the Healing of a Bone Fracture
The fibrocartilaginous callus forms when:
4
- Osteoblasts and fibroblasts migrate to the fracture and begin reconstructing the bone
- Fibroblasts secrete collagen fibers that connect broken bone ends
- Osteoblasts begin forming spongy bone
- Osteoblasts furthest from capillaries secrete an externally bulging cartilaginous matrix that later calcifies
Stages in the Healing of a Bone Fracture
Bone callus formation
What are the 3 steps in this?
- New bone trabeculae appear in the fibrocartilaginous callus
- Fibrocartilaginous callus converts into a bony (hard) callus
- Bone callus begins 3-4 weeks after injury, and continues until firm union is formed 2-3 months later
Stages in the healing of a bone fracture
Bone remodeling
2 steps?
- Excess material on the bone shaft exterior and in the medullary canal is removed
- Compact bone is laid down to reconstruct shaft walls