Week 2, Bones and Skeletal Tissues: Part A
Skeletal Car8lages
• Contain no blood vessels or nerves • Dense connec8ve 8ssue girdle of perichondrium contains blood vessels for nutrient delivery to car8lage
Skeletal Car8lages
1. Hyaline car8lages – Provide support, flexibility, and resilience – Most abundant type
3. Elas8c car8lages – Similar to hyaline car8lages, but contain elas8c
fibers
5. Fibrocar8lages – Collagen fibers—have great tensile strength
Copyright © 2010 Pearson Education, Inc. Figure 6.1
Axial skeleton Appendicular skeleton
Hyaline cartilages Elastic cartilages Fibrocartilages
Cartilages
Bones of skeleton
Epiglottis Larynx
Trachea Cricoid cartilage Lung
Respiratory tube cartilages in neck and thorax
Thyroid cartilage Cartilage in
external ear Cartilages in nose
Articular Cartilage of a joint Costal cartilage
Cartilage in Intervertebral disc
Pubic symphysis
Articular cartilage of a joint
Meniscus (padlike cartilage in knee joint)
Growth of Car8lage
• Apposi8onal – Cells secrete matrix against the external face of exis8ng car8lage
• Inters88al – Chondrocytes divide and secrete new matrix, expanding car8lage from within
• Calcifica8on of car8lage occurs during – Normal bone growth – Old age
Bones of the Skeleton
• Two main groups, by loca8on – Axial skeleton (brown) – Appendicular skeleton (yellow)
Copyright © 2010 Pearson Education, Inc. Figure 6.1
Cartilage in external ear
Cartilages in nose
Articular Cartilage of a joint Costal cartilage
Cartilage in Intervertebral disc
Pubic symphysis
Articular cartilage of a joint
Meniscus (padlike cartilage in knee joint)
Classifica8on of Bones by Shape
• Long bones – Longer than they are wide
• Short bones – Cube-‐shaped bones (in wrist and ankle) – Sesamoid bones (within tendons, e.g., patella)
Classifica8on of Bones by Shape
• Flat bones – Thin, flat, slightly curved
• Irregular bones – Complicated shapes
Copyright © 2010 Pearson Education, Inc. Figure 6.2
Func8ons of Bones
• Support – For the body and soX organs
• Protec8on – For brain, spinal cord, and vital organs
• Movement – Levers for muscle ac8on
Func8ons of Bones
• Storage – Minerals (calcium and phosphorus) and growth factors
• Blood cell forma8on (hematopoiesis) in marrow cavi8es
• Triglyceride (energy) storage in bone cavi8es
Bone Markings
• Bulges, depressions, and holes serve as – Sites of aYachment for muscles, ligaments, and tendons
– Joint surfaces – Conduits for blood vessels and nerves
Bone Markings: Projec8ons
• Sites of muscle and ligament aYachment – Tuberosity—rounded projec8on – Crest—narrow, prominent ridge – Trochanter—large, blunt, irregular surface – Line—narrow ridge of bone – Tubercle—small rounded projec8on – Epicondyle—raised area above a condyle – Spine—sharp, slender projec8on – Process—any bony prominence
Copyright © 2010 Pearson Education, Inc. Table 6.1
Bone Markings: Projec8ons
• Projec8ons that help to form joints – Head
• Bony expansion carried on a narrow neck – Facet
• Smooth, nearly flat ar8cular surface – Condyle
• Rounded ar8cular projec8on – Ramus
• Armlike bar
Copyright © 2010 Pearson Education, Inc. Table 6.1
Bone Markings: Depressions and Openings
• Meatus – Canal-‐like passageway
• Sinus – Cavity within a bone
• Fossa – Shallow, basinlike depression
• Groove – Furrow
• Fissure – Narrow, slitlike opening
• Foramen – Round or oval opening through a bone
Copyright © 2010 Pearson Education, Inc. Table 6.1
Bone Textures
• Compact bone – Dense outer layer
• Spongy (cancellous) bone – Honeycomb of trabeculae
Structure of a Long Bone
• Diaphysis (shaX) – Compact bone collar surrounds medullary (marrow) cavity
– Medullary cavity in adults contains fat (yellow marrow)
Structure of a Long Bone
• Epiphyses – Expanded ends – Spongy bone interior – Epiphyseal line (remnant of growth plate) – Ar8cular (hyaline) car8lage on joint surfaces
Copyright © 2010 Pearson Education, Inc. Figure 6.3a-b
Proximal epiphysis
(b)
(a)
Epiphyseal line
Articular cartilage
Periosteum
Spongy bone
Compact bone
Medullary cavity (lined
by endosteum)
Compact bone
Diaphysis
Distal epiphysis
Membranes of Bone
• Periosteum – Outer fibrous layer – Inner osteogenic layer
• Osteoblasts (bone-‐forming cells)
• Osteoclasts (bone-‐destroying cells) • Osteogenic cells (stem cells)
– Nerve fibers, nutrient blood vessels, and lympha8c vessels enter the bone via nutrient foramina
– Secured to underlying bone by Sharpey’s fibers
Membranes of Bone
• Endosteum – Delicate membrane on internal surfaces of bone
– Also contains osteoblasts and osteoclasts
Copyright © 2010 Pearson Education, Inc. Figure 6.3c
(c)
Yellow bone marrow
Endosteum
Compact bone
Periosteum
Perforating (Sharpey’s) fibers
Nutrient arteries
Structure of Short, Irregular, and Flat Bones
• Periosteum-‐covered compact bone on the outside
• Endosteum-‐covered spongy bone within
• Spongy bone called diploë in flat bones • Bone marrow between the trabeculae
Copyright © 2010 Pearson Education, Inc. Figure 6.5
Compact bone
Trabeculae
Spongy bone (diploë)
Loca8on of Hematopoie8c Tissue (Red Marrow)
• Red marrow cavi8es of adults – Trabecular cavi8es of the heads of the femur and humerus
– Trabecular cavi8es of the diploë of flat bones • Red marrow of newborn infants
– Medullary cavi8es and all spaces in spongy bone
Microscopic Anatomy of Bone
• Cells of bones – Osteogenic (osteoprogenitor) cells
• Stem cells in periosteum and endosteum that give rise to osteoblasts
– Osteoblasts • Bone-‐forming cells
Copyright © 2010 Pearson Education, Inc. Figure 6.4a-b
(a) Osteogenic cell (b) Osteoblast
Stem cell Matrix-synthesizing cell responsible for bone growth
Microscopic Anatomy of Bone
• Cells of bone – Osteocytes
• Mature bone cells
– Osteoclasts • Cells that break down (resorb) bone matrix
Copyright © 2010 Pearson Education, Inc. Figure 6.4c-d
(c) Osteocyte
Mature bone cell that maintains the
bone matrix
(d) Osteoclast
Bone-resorbing cell
Microscopic Anatomy of Bone: Compact Bone
• Haversian system, or osteon—structural unit – Lamellae
• Weight-‐bearing • Column-‐like matrix tubes
– Central (Haversian) canal • Contains blood vessels and nerves
Copyright © 2010 Pearson Education, Inc. Figure 6.6
Structures in the central canal
Artery with capillaries Vein Nerve fiber
Lamellae
Collagen fibers run in different directions
Twisting force
Microscopic Anatomy of Bone: Compact Bone
• Perfora8ng (Volkmann’s) canals – At right angles to the central canal – Connects blood vessels and nerves of the periosteum and central canal
• Lacunae—small cavi8es that contain osteocytes
• Canaliculi—hairlike canals that connect lacunae to each other and the central canal
Copyright © 2010 Pearson Education, Inc. Figure 6.7a-c
Endosteum lining bony canals and covering trabeculae
Perforating (Volkmann’s) canal
Perforating (Sharpey’s) fibers
Periosteal blood vessel Periosteum
Lacuna (with osteocyte)
(a)
(b) (c)
Lacunae
Lamellae
Nerve Vein Artery
Canaliculi Osteocyte in a lacuna
Circumferential lamellae
Osteon (Haversian system)
Central (Haversian) canal
Central canal
Interstitial lamellae
Lamellae
Compact bone
Spongy bone
Microscopic Anatomy of Bone: Spongy Bone
• Trabeculae – Align along lines of stress – No osteons – Contain irregularly arranged lamellae, osteocytes, and canaliculi
– Capillaries in endosteum supply nutrients
Copyright © 2010 Pearson Education, Inc. Figure 6.3b
(b)
Lacunae
Lamellae
Nerve
Vein
Artery
Canaliculus
Osteocyte in a lacuna
Central canal
Chemical Composi8on of Bone: Organic
• Osteogenic cells, osteoblasts, osteocytes, osteoclasts
• Osteoid—organic bone matrix secreted by osteoblasts – Ground substance (proteoglycans, glycoproteins) – Collagen fibers
• Provide tensile strength and flexibility
Chemical Composi8on of Bone: Inorganic
• Hydroxyapa8tes (mineral salts) – 65% of bone by mass
– Mainly calcium phosphate crystals – Responsible for hardness and resistance to compression
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