ANAT 100 Lecture Notes - Lecture 2: Bone Marrow, Perichondrium, Axial Skeleton

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Week 2: Skeletal System
Chapter 4: 101-107, Chapter 6: 147-156, 167-168
Chapter 7: 174-200, 204-214, Chapter 8: 220-244
Chapter 9: 253 - 282
Chapter 4: 101-107
Supportive Connective Tissue:
Includes: Cartilage and bones, semisolid and solid extracellular matrix
Cartilage: Firm, gel-like extracellular matrix
oComposed of protein fibers and ground substance
Chondrocytes: Matured cartilage cell, occupies space called Lacunae, which is within extracellular matrix
oChondrocytes prevent blood vessel formation via chemicals within extracellular matrix, This is called
Avascular, where no blood vessel form
Cartilage is stronger and more resilient than any other connective tissue, more flexible than bones
Strength in cartilage is from collagen fibers, Resilience from elastic fibers and amount of ground substance
Cartilage is covered by Perichondrium, there are two layers:
1) Outer layer-Fibrous region, dense irregular CT
Protection and mechanical support, secures perichondrium to cartilage and other structures
2) Inner layer-Cellular layer
Have stem cells (Chondroblasts), which is responsible for growth and maintenance of
cartilage
Types of Cartilage:
Hyaline Cartilage:
Function: Support soft tissue, model for future bone growth
Location: Articular end of bones, most of larynx, nose,
trachea, costal cartilage (cartilage on ribs)
Most common and weakest, IE-Joints
Chondrocytes within Lacunae are scattered, strong and
flexible tissue, poor regeneration
Is flexible and resilient, surrounded with perichondrium,
low friction and wear resistant
Fibro Cartilage:
Function: Shock absorber and resists compression
Location: Intervertebral discs, Menisci (in Knees) and
between anterior parts of pelvic bone
Strong and inflexible (no perichondrium), IE- Knee and in
between vertebrae
Elastic Cartilage:
Function: Deformation resistance
Location: Ear, Larynx, and Epiglottis
More flexible than Hyaline, IE-Ear
Bones:
Dry weight: 40% - Organic (Protein and carbohydrate molecules), 60% - Inorganic (Calcium salts, Primarily
Calcium Phosphate)
Supports soft structures, provides lever for movement, and protects organs
Bone Connective Tissue:
I) Organic: Attributes for tensile strength and flexibility in bones
II) Inorganic: Attributes for compressional strength in bones
Periosteum: Similar to perichondrium in Connective Tissues, but covers bone surfaces instead of cartilage surface
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Bone Cells
Osteoclast Resorb dissolved bones
Osteoblasts Forms bones
Osteocytes (Bone cells) Maintain bones and line cells that cover the bone
(Periosteum)
Canaliculi: Involved in exchanging material
Forms of Bone CT:
1) Compact Bone: Solid, but perforated by vascular canals, forms hard out shell of bones
2) Spongy Bone: Located within bones with spaces, Bone CT form latticework structure (interlacing strips),
lightweight and strong
Osteons: Also known as “Haversian system”, run parallel to long bone shafts
Lamellae: Concentric ring of bones in osteons and encircle Central canal, which allows blood vessels and nerves to
travel
Chapter 6: 147-148
Chondroblasts: Cells that product matrix of cartilage, encased in matrix and produce secretions of Chondrocytes
(mature cartilage cells)
Cartilage Functions:
1) Support soft tissue
2) Provide gliding surface at articulations (Joints) where two bones meet
3) Provide models for bone formation
Cartilage Growth Patterns: Multistep process in each (Page 148 for detailed)
1) Interstitial Growth: Located within internal regions of cartilage
a. Chondrocytes within lacunae stimulated and begin mitotic cell division
b. Two cells in Lacunae after division, Chondroblasts
c. Chondroblasts synthesize, each cell has its own Lacuna it occupies, Chondrocytes
d. Continue growth and production of matrix
2) Appositional Growth: Increases width along outside edge of cartilage
a. Mitotic activity is stem cells within perichondrium
b. Undifferentiated cells and committed cells differentiate into Chondroblasts, secrete matrix
c. Matrix push Chondroblasts apart and form chondrocytes, continues matrix production
Chapter 6: 148-150
Functions of the Bone:
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