Chapter 6: Cartilage & Bone

mature cartilage is ___________

avascular (non penetrated by blood vessels) so nutrients must diffuse through the matrix

chondroblasts

cells that produce the matrix of cartilage

Steps of appositional growth

1. Undifferentiated stem cells at the internal edge of the perichondrium begin to divide (perichondrium contains mesenchymal & stem cells) 2. New undifferentiated stem cells & committed cells that differentiate into chondroblasts are formed & are located at the periphery of the old cartilage where they begin to produce & secrete new cartilage matrix 3. chondroblasts push apart as a result of matrix formation & become chondrocytes; each occupying its own lacuna 4. Cartilage continues to grow at the periphery as chondrocytes continue to produce more matrix

Steps of interstitial growth

1. chondrocytes in lacunae are stimulated to undergo mitosis 2. 2 cells occupy a single lacuna after cell division; now called chondroblasts 3. As chondrocytes begin to secrete & synthesize new cartilage matrix, they are pushed apart. These cells now reside in their own lacuna and are called chondrocytes 4. Cartilage continues to grow in the internal region as chondrocytes continue to produce more matrix

osteoblasts

Formed from osteoprogenitor stem cells Cuboidal structure Secrete osteoid - initial semisolid, organic form of bone matrix Later calcified & hardens Once osteoblasts become entrapped in the matrix they produce & secrete & differentiate into osteocytes

appositional growth

Growth along the cartilage outside edge

Interstitial growth

Growth from within the cartilage itself

3 types of cartilage

Headline Elastic fibrocartilage

Interstitial lamellae

Leftover parts of osteons that have been partially reabsorbed; no central canal; incomplete

osteoclasts

Multi-nuclear pahagocytic cells Derived from fused bone marrow cells

Spongy bone is composed of ___________

Parallel lamellae

hemopoiesis

Process of red blood cell production - produces in red bone marrow in spongy bone

Growth hormone

Produced by the anterior pituitary gland Stimulates the formation of somatomedin which is produced in the liver and directly stimulates the growth of cartilage in the epiphyseal plate

osteolysis

Release of stored calcium and phosphate from the bone matrix

Osteoclasts ______ while osteoblasts _________ to the matrix

Remove; add

Concentric lamellae

Rings of bone connective tissue that surround the central canal Each contains collagen fibers oriented in perpendicular directions

circumferential lamellae

Rings of bone immediately internal to the periosteum of the bone; runs around the edge of the bone

Perforating canals

Run perpendicular to the central canals; connecting them under w/ blood vessels and nerves

Thyroid hormone

Secreted by thyroid gland Influences the basal metabolic rate of bone cells

osteoprogenitor cells

Stem cells Derived from mesenchyme Located both in the periosteum & endosteum When they divide, they produce another stem cell & a "command cell" that matures to become an osteoblast

Perforating fibers

Strong collagen fibers

Functions of bone

Support & protection Movement hemopoiesis Storage of mineral and energy reserves

3 major functions of cartilage

Supporting soft tissues Providing a gliding surface at articulations where 2 bones meet Providing a model for the formation of most of the bones in the body

canaliculi

Tiny, interconnecting channels within the bone tissue that extend from each lacuna, travel through the lamellae & connect to other lacunae & the central canal

Central canal

Where blood vessels & nerves that supply the bone travel

Osteocytes

lacunae - small spaces within the matrix in which osteocytes reside Maintain the bone matrix & detect mechanical stress on a bone

Spongy bone contains no ____________

osteons

Cells of bone

osteoprogenitor osteoblasts osteocytes osteoclasts

chondrocytes

when chondroblasts become encased within the matrix they have produced & secreted & occupy small spaces called lacunae