Week$2,$Bones$and$Skeletal$ Tissues ... - Master...

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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

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)

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

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

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

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

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

Proximal epiphysis

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

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

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

(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

(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

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

Endosteum lining bony canals and covering trabeculae

Perforating (Volkmann’s) canal

Perforating (Sharpey’s) fibers

Periosteal blood vessel Periosteum

Lacuna (with osteocyte)

(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

Lacunae

Lamellae

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

Week$2,$Bones$and$Skeletal$ Tissues ... - Master...

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