BIOLOGY 2401ANATOMY & PHYSIOLOGY

PART ICHAPTER 6

Bones and Skeletal Tissues

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Skeletal Cartilages• The skeletal cartilages are surrounded by a

dense irregular connective tissue called the perichondrium.– Supplies nutrients & removes wastes from

cartilage through diffusion from a rich vasculature

• Three types– Hyaline cartilage– Elastic cartilage– Fibrocartilage

• Chondrocytes located within lacunae. 2

Cartilage Locations

3

Classification of Bones• The 206 bones of the skeleton are classified into 2 Regions:

– Axial – cranium, vertebrae, rib cage– Appendicular – legs, arms, pelvis, shoulder girdle

• Bones are also classified into 4 Shapes:– Long bones – all are limb bones

• Humerus, radius, ulna, metacarpals, phalanges• Femur, tibia, fibula, metatarsals, phalanges

– Short bones – all are limb bones, too• patella, wrist & ankle bones

– Flat bones – sternum, ribs, skull and scapula– Irregular bones – pelvis & vertebrae

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Bone Shapes

Long

Short

Flat

Irregular5

Functions of Bones

• Support

• Protection

• Movement

• Mineral storage

• Blood cell formation

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Long Bone Structure

• Diaphysis – shaft– Compact bone surrounded by periosteum & endosteum

• osteoblasts and osteoclasts– Central medullary cavity

• in adults: filled with yellow bone marrow – fat storage• Epiphyses – ends – proximal and distal

– Spongy bone– Hyaline cartilage at articulations

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Long Bone Structure

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Structure of Other Bone Shapes

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• Short, irregular, and flat bones– Periosteum and endosteum– Dense bone on outer part– Spongy bone in middle part

Hematopoietic Tissues

• Red bone marrow– In adults red bone marrow is found in the spongy

bone of the femur, humerus, sternum, and pelvic girdle (hip bone)

– In infants, red bone marrow is found in all the bones.

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Microscopic Structure of Bone: Compact (Dense) Bone

The osteons are the structural units of dense bone (formerly known as Haversian systems).– Columns that run parallel to long axis of the bone.– Each is ringed like a tree.

• A lamella is an individual ring. • A lacuna is a space found between the lamellae. • Osteocytes are the cells that occupy the lacunae.

The osteon is traversed by canals for blood vessels and nerves.

Central (Haversian) canal runs down the center of the osteon

Perforating (Volkman) canal runs perpendicular to the osteon

Canaliculi connect the lacunae. 11

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Chemical Composition of Bone• 35% of bone is organic

– Osteocytes, osteoblasts, osteoclasts.– Ground substance and collagen fibers.

• 65% of bone is inorganic– Calcium phosphate

• Also known as Hydroxyapatites • The minerals form small crystals around the

collagen fibers

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Types of Fractures

Comminuted fracture – bone breaks into 3 or more pieces

Compression fracture – bone is crushed

Spiral fracture – ragged break in bone due to twisting

Epiphyseal fracture – epiphysis separates from diaphysis

Depressed fracture – skull fractures inward

Greenstick fracture – only one side of bone breaks; the other

side bends. Common in children.

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Repair of Fractures: 4 steps1) Hematoma formation – mass of clotted blood

2) Callus formation – “soft callus” (cartilaginous) splint

3) Bony callus formation – “hard callus” (spongy bone)

4) Bone remodeling – remove spongy bone of hard callus, replace with compact bone

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Homeostatic Imbalances of Bone• Osteomalacia

– Inadequate bone mineralization– Pain with stress on bones– Known as Rickets in children– Due to insufficient calcium leading to inadequate

mineralization in youth.– Bowed bones and improper formation.– Vitamin D deficiency

• Osteoporosis– Over activity of osteoclasts.

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Practice Questions

 

A condition that produces a reduction in bone mass sufficient to compromise normal function is

A. osteopenia. 

B. osteoporosis. 

C. osteitis. 

D. osteomyelitis. 

E. osteomalacia.

A major difference between bone tissue and other connective tissues lies in which of the following?

A. The limited blood supply available to bone tissue 

B. The inability of bone cells to metabolize nutrients for energy 

C. The presence of collagen fibers in bone 

D. The presence of elastic fibers in bone 

E. The composition of the intercellular substance of bone

How would increasing the proportion of organic molecules to inorganic components in the bony matrix affect the physical characteristics of bone?

A. The bones would be stronger.  B. The bones would be more brittle.  C. The bones would be more flexible.  D. The bone would be less flexible.  E. The bones would be less compressible.

Long bones differ from flat bones in that long bones 

A. have an outer layer of compact bone. 

B. have epiphyses. 

C. contain marrow. 

D. have a periosteum membrane. 

E. contain spongy bone.

The bones of the skeleton store energy reserves as lipids in areas of

A. yellow marrow. 

B. red marrow. 

C. the ground substance. 

D. spongy bone. 

E. the matrix of bone tissue.

The cells that maintain mature compact bone are

A. osteocytes. 

B. lacunae. 

C. osteoclasts. 

D. chondrocytes. 

E. osteoblasts.

The lacunae of bone contain

A. blood cells. 

B. osteons. 

C. chondroblasts. 

D. bone marrow. 

E. osteocytes.

A fracture in the shaft of a bone would occur in the  

A. metaphysis. 

B. epiphysis. 

C. diaphysis. 

D. epiphyseal line.

Osteocytes maintain contact with the blood vessels of the central canal through 

A. periosteum. 

B. canaliculi. 

C. drainage canals. 

D. concentric lamellae.

Spongy bone contains all of the following except 

A. true osteons. 

B. collagen fibers. 

C. hydroxy apatite. 

D. trabeculae.

Collagen in the bone matrix provides flexible strength. 

 True False

Mature bone cells are called chondrocytes. 

 True False

The central canal of an osteon contains osteocytes. 

 True False

The most abundant mineral in the human body is calcium. 

 True False

The shaft of the long bone is called the diaphysis. 

 True False

Vitamin D is necessary for the formation of the organic framework of bone. 

 True False

Osseous tissue is avascular. 

 True False

A metacarpal is an example of a long bone. 

 True False

Increasing the percentage of collagen in a bone would make it become more rigid. 

 True False