Lecture 39: Histology and Embryology of Cartilage and Bone Flashcards
What occurs at the proliferation zone at the epiphyseal plate of growing long bone?
Chondroblasts quickly divide and push the epiphysis away from the diaphysis, lengthening the bone
Which zone at the epiphyseal plate of growing long bone has older chondrocytes enlarging and signaling the surrounding matrix to calcify?
Hypertrophic zone
What occurs at the calcification zone at the epiphyseal plate of growing long bone?
Matrix becomes calcified; chondrocytes die, leaving behind trabeculae-shaped calcified cartilage (NOT bone yet)
At the ossification zone (metaphysis), _____ digest the calcified cartilage and _____ replace it with actual bone tissue in the shape of the calcified cartilage, resulting in ______.
osteoclasts. osteoblasts, bone trabeculae
What zone at the epiphyseal plate of growing long bone has small, inactive cartilage cells?
Resting zone
What comprises the histological appearance of cartilage?
cells (chondrocytes, cartilage cells) and matrix (ECM) composed of collagen fibers, ground substance, and water
What are the three cartilage tissue types?
fibrous, elastic, and hyaline
Which cartilage tissue type has type I collagen fibers visible in the matrix and NO perichondrium?
Fibrous
What type of cartilage comprises intervertebral discs, the pubic symphysis, knee joints, tendons, and ligament insertions into bone?
Fibrous
Which type of cartilage has type II collagen and elastin in its matrix and where is it found?
Elastic found in ear and epiglottis
What are the defining features of hyaline cartilage and where is it found?
Type II collagen, homogeneous matrix (smooth appearance), and fibers NOT visible in matrix
Found in respiratory tract, ventral ends of ribs, synovial joints, and growth plates of extremity long bones
What are the three cartilage cell types?
Perichondrial cells (mesenchymal precursors) Chondroblasts (divide, grow, synthesize matrix) Chondrocytes (maintain matrix)
What are the two types of cartilage growth?
Appositional (perichondrial derived, at the periphery, adds width)
Interstitial (isogenous groups of chondroblasts, at growth plate, adds length)
What type of cartilage growth comprises chondroblast division, produces cell clusters where each cell make matrix, pushing it apart from sister cells, and where cartilage can expand from within because the matrix is gel?
Interstitial (isogenous groups)
What type of cartilage growth comprises the growth plate?
long rows of isogenous groups of chondroblasts doing interstitial growth (in proliferation zone)
What is the primary histological difference between cartilage matrix and bone matrix?
bone matrix = osteoid and crystals (not found in cartilage
What is osteoid?
uncalcified pre-bone
Most of the skeleton begins as cartilaginous template that then ossifies to become bone. This process of converting cartilage to bone is called _____.
endochondral ossification
What are the four bone cell types?
Osteoprogenitor cells
Osteoblast
Osteocyte
Osteoclast
What are osteoid canaliculi?
small channels that contain cytoplasmic processes from osteocytes; they communicate with other osteocytes via gap junctions
What type of bone growth utilizes the membrane model, features appositional growth at the periosteum, contributes to long bone width, and histology will show bone but never cartilage?
Intramembranous bone formation
What type of bone growth utilizes the hyaline cartilage model, features interstitial growth at the growth plate, contributes to long bone length, and histology will show bone AND cartilage?
Endochondral bone formation
Describe the embryological formation of long bones.
mesenchyme condenses, chondrocytes make cartilage model, blood vessels bring mineralization, and osteoblasts make bone
Bone cap is to _____.
epiphysis
