Chapter 5 - The Skeletal System Flashcards
Two divisions of the skeleton and their meanings
- Axial - head and center of body (skull, ribs, vertebral column)
- Appendicular - movement (limbs, pelvis)
How many bones are in the body?
206
Two types of bone tissue and their meanings
- Compact bone - dense smooth bone
2. Spongy bone - bone with open spaces within
The skeletal system makes up how much of the body?
20% of total body mass
Four components to the skeletal system
- Cartilage
- Bone
- Tendons
- Ligaments
Functions of the skeletal system along with their specific meanings
- Protection
- Support - rigid structure
- Movement - bones act as levers
- Storage - Ca, P, and fat
- Blood cell production
What does cartilage consist of?
- Cells
2. Extracellular matrix
Cartilage cells
Chondrocytes
Where are the chondrocytes found in cartilage?
Lacunae
Two components to the extracellular matrix in cartilage
- Collagen and Elastic fibers
2. Ground substance of chondrotin sulfates
What does cartilage lack and what is the cause of lacking this?
- Lacks arteries, veins, and lymphocytes
- It heals very slowly
Types of cartilage
- Hyaline
- Elastic
- Fibrocartilage
What is the most common but weakest cartilage?
Hyaline cartilage
Structure and location of hyaline cartilage
Structure: Chondrocytes, chondroitin sulfate, some collagen
Location: Embryonic skeleton, Articular surfaces, respiratory passages, nasal septum, between ribs and sternum
Structure and location of Elastic Cartilage
Structure: Chondrocytes, chondrotin sulfate, densely packed elastic fibers
Locations: auricle, tip and lateral walls of nose, epiglottis
Most flexible type of cartilage
Elastic cartilage
The strongest type of cartilage
Fibrocartilage
Structure and location of fibrocartilage?
Structure: Chondrocytes, chondrotin sulfate, densely packed collagen fibers
Location: Intervertebral disc, pubic symphysis, articular cartilage in kneww
Surrounds the cartilage
Perichondrium
What is the perichondrium made out of?
Fibrous connective tissue
What does the perichondrium provide?
- Support and protection
- New chondrocytes
Where is the perichondrium located?
- Hyaline cartilage
- Elastic cartilage
Where is the perichondrium absent?
- Articular surfaces
- Fibrocartilage
The layers and the functions of the layers for the Perichondrium
- Outer: binds cartilage to adjacent tissues; provides support and protection
- Inner: For growth and maintenance
Six steps to appositional growth in cartilage
- Starts in perichondrium
- Mesenchymal cells form inner layer of perichondrium
- Mesenchyme move toward matrix to become chondrogenic cells
- Chondrogenic cells aggregate and become chondroblasts
- Chondroblasts secrete matrix which forces cells apart
- Chondroblasts become enclosed in matrix and become chondrocytes
Three steps to Interstitial growth
- Chondrocytes are enclosed in matrix and divide
- As they move apart, matrix forms in between them
- Growth of cartilage from within
Three characteristics of Osseous tissue
- Made of supportive CT
- Contains specialized cells
- Solid extracellular matrix
What is the solid extracellular matrix in osseous tissue composed of?
- Osteoid - organic portion, protein fibers
- Ground substance - Ca salts
- Water
Order of the creation of bone cells
- Osteoprogenitor
- Osteoblasts
- Osteocytes
What do osteoprogenitor cells do?
- Mesenchymal cells
- Predecessor to osteoblasts
- Play role in initial bone growth and fracture repair
Increased osteoblast activity equates to what?
Stronger bone
Characteristics and derivations of osteoblasts?
- Derived from osteogenic cells and predecessor to osteocytes
- Secrete osteoid
- Common in growing bone
Characteristics of osteocytes
- Mature cells
- Exist within matrix
- Maintain Ca and PO4 homeostasis
- Found in spaces called lacunae
Break down of bone
Osteolysis
Cells involved in osteolysis
Osteoclasts
Increase in osteoclast activity equate to what?
Weaker bone
How do osteoclasts form?
They form from the fusion of many white blood stem cells
Two components that make up the bone matrix
- Inorganic materials
2. Osteoid
What composes the inorganic materials in the bone matrix?
- Brittle salts - Hydroxyapatite, calcium carbonate, ions
How much of the bone matrix is composed of inorganic materials?
65%
What are the things that up the osteoid in the bone matrix?
- Organic
2. Collagen, glycoproteins, and proteoglycans
What percentage of the cell matrix in bone is composed of osteoid?
35%
What are the two prominent qualities to the bone matrix?
Flexible because of the fibers
Strong because of the inorganic materials
Two types of bone
- Compact
2. Spongy
How is compact bone arranged?
in Osteons
How is spongy bone arranged?
Arranged in trabeculae
Osteoctyes communicate through ____
Canaliculi
What do canaliculi do?
Radiate outward and connect one cell to the next cell in compact bone
A unit of compact bone
Osteon
Three structural components to osteons
- Concentric lamellae of matrix surrounding a central (Haversian) canal
- Contains blood vessels and nerves
- Osteons connected to each other by perforating canals
Three different kinds of lamellae
- Concentric
- Interstitial
- Circumferential
- Layers of bone surrounding the central canal
- Make up osteons
Concentric lamellae
- Found between the osteons
- Represents older osteons partially removed during tissue remodeling
Interstitial lamellae
- Surrounded the compact bone
- Directly produced from periosteum
Circumferential
What does spongy bone (cancellous) contain?
- Trabeculae
- Ostecytes in lacunae
- Canaliculi
- Matrix
What does spongy bone not contain?
Osteons and central canal
Latticework of thin plates of bone oriented along lines of stress
Trabeculae
The spaces on trabeculae are filled with what?
Bone marrow where blood cells develop
Where is trabeculae found?
Found in ends of long bones and inside flat bones
What does trabeculae do?
Lightens the bone and allows for movement
Encloses bone
Periosteum
Where is periosteum absent?
- Site of attachment of muscles, tendons, and ligaments
- Instead, surface are covered by articular cartilage
Two layers of the periosteum and their respective jobs
- Outer fibrous: gives rise to collagen
2. Inner: for growth or new cells and maintenance
One cell layer that covers surfaces of spongy bone and medullary cavity
Endosteum
Cell types in the endosteum
- Osteogenic, osteoblasts, and osteoclasts
Five components to the anatomy of a long bone
- Diaphysis
- Epiphysis
- Metaphysis
- Articular cartilage
- Medullary cavity
Shaft of a long bone
Diaphysis
One end of a long bone
Epiphysis
Growth plate region of a long bone
Metaphysis
Over joint surfaces and acts as friction and shock absorber
Articular cartilage of a long bone
Marrow cavity of a long bone
Medullary cavity
Two types of bone marrow
Yellow and red
Components to red bone marrow
- Areolar and myeloid tissue
2. Produces all types of blood cells
Locations of red bone marrow
In medullary cavities of infants and in spongy bone in adults
Four components to yellow bone marrow
- Composed of arelolar and adipose CT
- In medullary cavity of long bones
- Energy storage
- Absent in infants
Supplies arteries with blood and nerve supply
Periosteal arteries
- Enter through nutrient foramen
- Supplies compact bone of diaphysis and yellow marrow
Nutrient arteries
Nutrient arteries enter through _____
Nutrient foramen
Supply red marrow and bone tissue of epiphyses and metaphyses
Metaphyseal and epiphyseal arteries
All arteries have corresponding _____
Veins
Replacing CT with bone
Ossification
Mesenchymal cells -> spongy bone
Intramembranous
Hyaline cartilage -> spongy bone
Endochondral
When does intramembranous ossification begin and end?
Begins at about week 8 in embryo and finishes by week 15
What does the intramembranous ossificiation form?
- Cranial flat bone
- Facial bones
- Dentary bones
- Clavicle
- Sesmoid bones
Location where bone growth begins
Primary ossification center
Steps to intramembranous ossification
- Primary ossification center
- Mesenchymal cells arrange around blood vessels
- Bone morphogenic proteins released
- Mesenchymal cells are recruited, divided, and differentiated into osteoblasts
- osteoblasts secrete osteoid
- Osteoblasts become isolated and turn into osteocytes
- Produce spicules of bone that interconnect
- Mesenchymal cells at surface form inner layer of periosteum
- Calcified matrix is degraded by osteoclasts to form spongy bone
- End = spongy bone covered with thin layer of compact bone
When bone replaces a cartilage model
Endochondral Ossification
When does endochondral ossification begin?
Week 7 of embryo
What does endochondral ossification
- Long bones
- Most short bones
- Non-cranial irregular and flat bones
- Middle ear ossicles
Steps to endochondral ossification
- Hyaline cartilage forms model of future bone
- Cartilage enlarges; chondrocytes near center hypertrophy
- Blood vessels grow around and penetrate cartilage
- Cells differentiate into osteoblasts
- Compact bone forms around the diaphysis
- Spongy bone forms in the primary ossification center
- Remodeling of the shaft
- Formation of the medullary cavity
- Length increases
- Blood vessels penetrate the ends of the model
- Secondary ossification centers form at both epiphyses
- Ends with incomplete ossification of epiphysis
- Some cartilage remains
What does it mean when the chondrocytes are near hypertrophy
- Matrix reduced to struts
2. Chondrocytes deprived of nutrients and die
At the ends of endochondral ossification, what cartilage remains?
- Articular cartilage - contact points of bone
2. Epiphyseal plate - growth plate
Explain the process of bone growth: elongation
- Occurs at epiphyseal plate
- Growth in length continues until 2 ossification centers meet
- Relative thickness of epiphyseal plate does not change until growth complete
- Cartilage depleted and epiphyseal plate narrows to epiphyseal line
Explain bone growth: appositional
- Compact bone deposited beneath periostium
- Bone thickens
- Bone remodeling occurs throughout life (Due to osteoclasts and osteoblasts)
Continual redistribution of bone matrix along lines of mechanical stress
Bone remodeling
Why is bone remodeling ongoing?
Osteoclasts carve out small tunnels and osteoblasts rebuild osteons
What percentage of bone is remodeled each year?
4% compact bone and 20% of spongy bone
This bone is fully remodeled every 4 months
Distal femur
Two types of fractures in bones with their meanings
- Closed (simple): break that does not penetrate skin
2. Open (compound): broken bone penetrates through skin
Fractures are treated by ____ and ____
Reduction and immobilization
Four ways for fractures to be repaired
- Fracture hematoma
- Fibrocartilage callus
- Bony callus
- Remodel tissue
Factors affecting growth, repair, and development
- Nutrition: Vit. D
- Sunlight
- Hormones: PTH, calcitonin, GH, thyroid hormone, sex hormones
- Physical stress
Abnormal reduction of bone mass
Osteoporosis
Reasons for osteoporosis
- Loss of estrogen at menopause
- Deficiency of minerals in youth
- Imbalance in activity between osteoblasts and osteoclasts
Explain the illness of fibrodysplasia ossificant progressiva and its affect on the body and treatment plan
- Fibrous tissue becomes ossified
- Genetic
- Injury results in inappropriate bone formation
- Early adulthood: freezing of major joints
- Early 20s: confined to wheel chair
- Starvation and pneumonia can result
- No treatment
