6 The Skeletal System: Bone Tissue

Front 1

Skeletal system

Back 1

Framework of bones and their cartilages, ligaments , and tendons.

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Osteology

Back 2

The study of bones.

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diaphysis

Back 3

The shaft of a long bone.

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epiphyses

Back 4

The end of a long bone, usually larger in diameter than the shaft (diaphysis).

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metaphyses

Back 5

Region of a long bone between the diaphysis and epiphysis that contains the epiphyseal plate in a growing bone.

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articular cartilage

Back 6

Hyaline cartilage attached to articular bone surfaces.

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periosteum

Back 7

The membrane that covers bone and consists of connective tissue, osteogenic cells, and osteoblasts; is essential for bone growth, repair, and nutrition.

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perforating fibers

Back 8

Thick bundles of collagen that extend from the periosteum into the bone extracellular matrix to attach the periosteum to the underlying bone.

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medullary cavity ( marrow cavity)

Back 9

The space within the diaphysis of a bone that contains yellow bone marrow.

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endosteum

Back 10

The membrane that lines the medullary (marrow) cavity of bones, consisting of the osteogenic cells and scattered osteoclasts.

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calcification

Back 11

Deposition of mineral salts , primarily hydroxyapatite, in a framework formed by collagen fibers in which the tissue hardens.

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Osteoprogenitor cell

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Stem Cell derived from mesenchyme that has mitotic potential and the ability to differentiate into an osteoblast.

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Osteoblast

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Cell formed from an osteogenic cell that participates in bone formation by secreting some organic components and inorganic salts.

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Osteocyte

Back 14

A mature bone cell that maintains the daily activities of bone tissue.

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Osteoclast

Back 15

A large, multinuclear cell that maintains the daily activities of bone matrix.

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Compact bone tissue

Back 16

Bone tissue that contains few spaces between osteons (haversian systems); forms the external portion of all bones and bulk of the diaphysis (shaft) of long bones; is found immediately deep to the periosteum and external to spongy bone.

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osteons

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The basic unit of structure in adult compact bone, consisting of a central (haversian) canal with its concentrically arranged lamellae, lacunae, osteocytes, and canaliculi.

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central canal

Back 18

A microscopic tube running the length of the spinal cord in the gray commissure.

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lacunae

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A small , hollow space, such as that found within the syncytiotrophoblast.

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Canaliculi

Back 20

Small channels or canals, as in bones, where they connect lacunae.

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perforating canals

Back 21

A minute passageway by means of which blood vessels and nerves from the periosteum penetrate into compact bone.

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perforating fibers

Back 22

Thick bundles of collagen that extend from the periosteum into the bone extracellular matrix to attach the periosteum to the underlying bone.

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spongy bone tissue

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Bone tissue that consists of an irregular latticework of thin plates of the bone called trabeculae; spaces between trabuculae of some bones are filled with the red bone marrow; found inside short, flat, and irregular bones and in the epiphyses (ends) of the long bones.

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ossification (osteogenesis)

Back 24

Formation of bone.

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Intramembranous ossification

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The method of the bone formation in which the bone is formed directly in mesenchyme arranged in sheetlike layers that resemble membranes.

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endochondral ossification ( Intracartilaginous ossification)

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The replacement of cartilage by the bone.

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ossification center

Back 27

An area in the cartilage model of a future bone where the cartilage cells hypertrophy, secrete enzymes that calcify their extracellular matrix, and die, and the area they occupied is invaded by osteoblasts that then lay down bone.

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perichondrium

Back 28

The membrane that covers cartilage.

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interstitial (endogenous) growth

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Growth form within, as in the growth of cartilage.

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appositional (exogenous) growth

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Growth due to surface deposition of material, as in the growth in diameter of the cartilage and bone.

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periosteum

Back 31

The membrane that covers bone and consists of connective tissue, osteogenic cells, and osteoblasts; is essential for bone growth, repair, and nutrition.

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epiphyseal (growth) plate

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The hyaline cartilage plate in the metaphysis of a long bone; site of lengthwise growth of long bones.

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epiphyseal line

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The remnant of the epiphyseal plate in the metaphysis of long bone.

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Bone remodeling

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Replacement of old bone by new bone tissue.

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fracture

Back 35

Any break in a bone.

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parathyroid hormone (PTH)

Back 36

A hormone secreted by the chief (principle) cells of the parathyroid glands that increases blood calcium level and decreases blood phosphate level.

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calcitonin (CT)

Back 37

A hormone produced by the parafollicular cells of the thyroid gland that lower the amount of blood calcium and phosphates by inhibiting bone resorption (breakdown of bone extracellular matrix) and by accelerating uptake of the calcium and phosphates into the bone matrix.

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demineralization

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Loss of calcium and phosphorus form bones.

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Functions of Bone and Skeletal System

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1. Support

2. Protection

3. Assistance in Movement

4. Mineral Homeostasis

5. Blood Cell Production

6. Triglyceride Storage

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Support

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The skeleton serves as the structural framework for the body by supporting soft tissues and providing attachment points for the tendons of the most skeletal muscles.

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Protection

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The skeletal protects the most important internal organs from injury.

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Assistance in Movement

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Most skeletal muscles attach to bones; when they contract, they pull on bones to produce movement.

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Mineral Homeostasis

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Bone tissue makes up about 18% of the body weight of the human body.

　

Bone tissue stores several minerals

Acts to serve as a reservoir of critical

minerals

Calcium (99% of body’s content)

Phosphorus

Front 44

　

Blood Cell Production

Back 44

Within certain bones, a connective tissue called red bone marrow produces red blood cells, white blood cells, and platelets, a process called hemopoiesis.

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Triglyceride Storage

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Yellow bone marrow consists mainly of adipose cells, which store triglycerides.

　

Serves as a potential chemical energy reserve

　

　

　

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Long Bone Anatomy (Humerus)

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1. Diaphysis

2. Epiphyses

3. metaphyses

4. Articular cartilage

5. periosteum

6. medullary cavity

7. endosteum

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calcification

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is initiated by bone-building cells called osteoblasts

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Bone may be categorized as:

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1. Compact

2. Spongy

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Compact Bone

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Compact bone tissue provides protection and support and resists stresses produced by weight and movement. Compact bone tissue is compound of repeating structural units of osteons, or haversian system.

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concentric lamellae

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Resembling the growth rings of a tree

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trabeculae

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It consists of lamellae that are arranged in an irregular pattern of then columns.

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Periosteal arteries

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small arteries accompanied by nerves, enter the diaphysis through many perforating (Volkmann's) canals and supply the periosteum and outer part of the compact bone.

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Epiphyseal veins

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carry blood away from long bones

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Growth in Thickness

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Bones grow in thickness at the outer surface

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Remodeling of Bone

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Compact bone replaces spongy bone around the periphery of the fracture.

　

The ongoing replacement of old bone tissue by new bone tissue

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Minerals

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Large amounts of calcium and phosphorus and smaller amounts of magnesium, fluoride, and manganese are required for bone growth and remodeling

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Vitamins

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Vitamin A stimulates activity of osteoblasts

Vitamin C is needed for synthesis of collagen

Vitamin D helps build bone by increasing the absorption of calcium from foods in the gastrointestinal tract into the blood

Vitamins K and B12 are also needed for synthesis of bone proteins

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Hormones

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1. During childhood, the hormones most important to bone growth are growth factors (IGFs), produced by the liver
2. IGFs stimulate osteoblasts, promote cell division at the epiphyseal plate, and enhance protein synthesis
3. Thyroid hormones also promote bone growth by stimulating osteoblasts
4.

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Hormones

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Estrogen and testosterone cause a dramatic effect on bone growth

　

Cause of the sudden "growth spurt" that occurs during the teenage year

　

　

Promote changes in females, such as widening of the pelvis

　

Shut down growth at epiphyseal plates

　

　

　

Parathyroid hormone, calcitriol, and calcitonin are other hormones that can affect bone remodeling

　

　

　

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Fracture Types

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1. Open (compound)

2. Comminuted

3. Greenstick

　

4. Impacted

5. Pott

6. colles

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Open (compound)

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The broken ends of the bone protrude through the skin

　

　

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Comminuted

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The bone is splintered, crushed, or broken into pieces

　

　

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Greenstick

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A partial fracture in which one side of the bone is broken and the other side bends

　

　

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Impacted

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One end of the fractured bone is forcefully driven into another

　

　

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Pott’s

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Fracture of the fibula, with injury of the tibial articulation

　

　

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Colles

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A fracture of the radius in which the distal fragment is displaced

　

　

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Stress fracture

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A series of microscopic fissures in bone

　

　

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Closed (simple) fracture

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Does not break the skin

　

　

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fracture hematoma

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Blood vessels crossing the fracture line are broken. As blood leaks from the torn ends of the vessels, a mass of blood (usually clotted) forms around the site of the fracture.

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Fibrocartilaginous callus formation

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Fibroblasts invade the fracture site and produce collagen fibers bridging the broken ends of the bone

　

　

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Bony callus formation

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Osteoblasts begin to produce spongy bone trabeculae. The trabeculae join living and dead portions of the original bone fragments.