Group 8/9/19 Flashcards
general structure of cartilage
avascular, no nerves or lymphatics
tough, durable form of connective tissue
perichondrium structure and function
sheath of dense connective tissue that surrounds cartilage in most places (not in articular cartilage)
functions to grow and maintain cartilage
structure has type 1 collagen and fibroblasts on the outside, and mesenchymal stem cells on the inside
cells of cartilage, and their function
chondrocytes, these synthesize and maintain the components in the ECM
location of chondrocytes
lacunae, which are matrix cavities
matrix of cartilage
extracellular matrix (ECM) has high concentration of GAGs and proteoglycans that interact with collagen and elastic fibers
aggrecan
a proteoglycan that binds a large amount of water
functions to bind to type 2 collagen fibrils
types of cartilage
hyaline, elastic, fibrocartilage
location of hyaline cartilage
upper respiratory tract, articular ends and epiphyseal plates of long bones, fetus
location of elastic cartilage
external ear, external acoustic meatus, auditory tube, epiglottis and other laryngeal cartilages
location of fibrocartilage cartilage
intervertebral discs, pubic symphysis, meniscus, other joints, and insertion of tendons
functions of hyaline cartilage
resists compression
cushioning, smooth, low-friction surfaces for joints
structural support for respiratory system
forms foundation for development of fetal skeleton and bone growth
functions of elastic cartilage
flexible support for soft tissues
functions of fibrocartilage
resists deformation under stress
presence of perichondrium in hyaline cartilage
yes, except articular cartilage and epiphyseal plates
presence of perichondrium in elastic cartilage
yes
presence of perichondrium in fibrocartilage
no
which types of cartilage undergo calcification?
hyaline cartilage calcifies in endochrondal bone formation during the aging process
fibrocartilage calcifies the callus during bone repair
what cells is aggrecan secreted by?
chondrocytes
what cells is versican secreted by?
fibroblasts
typical arrangement of chondrocytes in hyaline cartilage
small isogenous groups
typical arrangement of chondrocytes in elastic cartilage
isolated or small isogenous groups
typical arrangement of chondrocytes in fibrocartilage
isolated or in isogenous groups, arranged axially
osteoarthritis
chronic, during aging, loss of hyaline cartilage lining articular ends of bones
chondronectin
a structural mutliadhesive glycoprotein
functions to bind to GAGs, collagen and integrins, so that chondrocytes can adhere to the ECM
chondrocytes location and function
located at the edge of cartilage in lacunae function to synthesize sulfated GAGs and secrete proteoglycans
hormone that regulate hyaline cartilage growth
somatotropin
chondrogenesis
process by which cartilage forms from mesenchyme
- mesenchymal cells multiply and pack
- chondroblasts created
- ECM encloses chondroblasts to separate them
- embryonic development
- become chondrocytes
types of cartilage growth processes
interstitial and appositional
interstitial growth
enlarges cartilage, uses mitosis for division, important for long bone development
appositional growth of cartilage
takes progenitor cells from perichondrium, and differentiates them into chondroblasts
repair of cartilage
cells from the perichondrium invade the injured area and produce new cartilage
slow and incomplete, except in young
produces a scar of dense connective tissue
bone development name
osteogenesis
types of bone development*
intramembranous ossification and endochondral ossification
process of intramembranous ossification
- in condensed mesenchyme, incomplete layers of osteoblasts form in ossification centers
- osteoblasts secrete osteoid, forms woven bone with osteocytes in lacunae and canaliculi
- neighboring ossification centers fuse
- woven bone is replaced by compact bone
- if there’s no ossification centers, the mesenchymal regions become endosteum and periosteum
process of endochondral ossification
- osteoblasts produce a bone collar around the cartilage model diaphysis
- causes chondrocytes to hypertrophy and die, the ECM is compressed and calcifies
- blood vessels from the perichondrium (now periosteum) penetrate the bone collar
- vessels and new osteoblasts move in and produce woven bone
- primary ossification center is formed during the 1st trimester
- secondary ossification centers develop similarly, later in time, at epiphyses of the cartilage model
epiphyseal cartilage
connects the epiphysis to the diaphysis and is involved in long bone growth
disappears once bones are formed
epiphyseal plates
these separate the primary ossification center in the diaphyses and the secondary ossification center in the epiphyses
disappear via epiphyseal closure by age 20
types of endochondral ossification
longitudinal and appositional growth
longitudinal growth process of endochrondral ossification
- cartilage cells in epiphyseal plates proliferate
- chondrocytes in the diaphysis cells hypertrophy, and the matrix calcifies and dies
- osteoblasts lay down a new bone layer
- epiphyseal plates are displaced away from the center, and the bone length increases
appositional growth process of endochondral ossification
- a bone collar is formed on the cartilaginous diaphysis
- new bone is added at the periosteal surface while bone is removed at the endosteal surface
- the central marrow cavity expands, so bone circumference grows
zones of activity in epiphyseal growth plate from farthest from ossification center to closest
- zone of reserve (resting) cartilage
- proliferative zone
- zone of hypertrophy
- zone of calcified cartilage
- zone of ossification
zone of reserve (resting) cartilage
composed of hyaline cartilage
proliferative zone
cartilage cells multiply, secrete type 2 collagen and proteoglycans, into columns
zone of hypertrophy
chondrocytes swell, secrete type X collagen which stiffens the matrix and promotes vascularization
zone of calcified cartilage
chondrocytes begin matrix calcification
zone of ossification
bone tissue appears. Capillaries and osteoprogenitor cells go to the lacunae, osteoblasts secrete osteoid, woven bone develops into lamellar bone
bone repair process
- blood vessels at the fracture site release blood that clots and forms a hematoma
- macrophages remove the hematoma, periosteum and endosteum replaces it with procallus tissue
- blood vessels and osteoblasts replace the procallus, new woven bone forms a hard callus
- woven bone becomes compact and cancellous bone
***LEARNING ISSUES AND LOOK-UPS
Here are the learning issues we decided on for the next group meeting:
- Histology of cartilage
- Histology of development vs healing bones
- Anatomy of the upper arm (muscles, bones, tendons, ligaments)
muscle and nerve for 0-15 degree arm abduction*
supraspinatus muscle; suprascapular nerve
muscle and nerve for 15-100 degree arm abduction*
deltoid muscle; axillary nerve
muscle and nerve for >90 degree arm abduction*
trapezius muscle; accessory nerve
muscle and nerve for >100 degree arm abduction*
serratus anterior muscle; long thoracic (SALT) nerve
which shoulder muscles form the rotator cuff muscles, and what are their innervations?*
SItS: supraspinatus (suprascapular nerve), infraspinatus (suprascapular nerve), teres minor (axillary nerve), subscapularis (upper and lower subscapular nerves)
action of supraspinatus muscle*
- abducts arm initially, 0-15 degrees
- most common rotator cuff injury, can be assessed with the empty/full can test
action of infraspinatus muscle*
externally rotates the arm
action of teres minor muscle*
adducts and externally rotates arm
action of subscapularis muscle*
internally rotates and adducts arm
greenstick fracture*
incomplete fracture extending partway through width of bone following bending stress. The bone fails on the tension side while the compression side is intact. Bent like a green twig.
Torus (buckle) fracture*
cause: axial force applied to the immature bone
effect: cortex buckles on compression side and fractures, while tension side remains intact
