Test 2 - Cartilage & Bone Flashcards
What are the 4 functions of cartilage?
- flexible support
- resistance to compression and deformation
- template for bone growth
- cushioning
What are the 5 general features of cartilage?
- chondrocytes in lacunae
- chondroblasts in isogenous groups
- solid, gel-like
- multiple collagen types
- avascular
Describe the appearance of hyaline cartilage while describing why the matrix appears as it does.
layered.. dense CT at top and is eosinophilic (pos. charges) … interterritorial matrix has sulfated proteoglycans around lacunae and is hemophilic (negative charges from sulfates)
What is endochondral ossification, and which type of cartilage does it use?
It is the growth of long bones and uses hyaline cartilage
Describe the appearance of elastic cartilage while describing why the matrix appears as it does.
It looks like hyaline, but the ECM is more pink and the fibers are highly branched.
It does not calcify
Type II collagen
Describe fibrocartilage’s appearance
- combo of dense connective tissue and type I and II collagen fibers
- calcified during bone repair
- no true perichondrium
- all about collagen fibers
- RARE
- looks like dense regular connective tissue but with lacunae
Hyaline cartilage function (6)
- resists compression
- cushion
- low friction (joints)
- structural support
- fetal skeleton template
- endochondral bone formation and growth
Hyaline cartilage locations (8):
- fetal skeleton
- epiphyseal plate
- articular surface of synovial joints
- costal cartilages
- nasal cavity
- larynx
- trachea
- bronchi
Elastic cartilage function
flexible support (elastic, resilient)
Elastic cartilage location
- pinna of external ear
- external auditory meatus
- Eustachian tubes
- larynx (epiglottis)
Fibrocartilage function
resist deformation under stress
Fibrocartilage locations (6)
- intervertebral discs
- symphysis pubis
- articular discs
- menisci
- triangular fibrocartilage complex
- insertion of tendons
How does cartilage ossify?
matrix change and turns cartilage into bone by adding a lot of calcium which then causes it to calcify and allows it to mineralize and harden
Describe the chemistry of bone.
formed by hydroxyapatite crystals (CA10(PO4)6(OH)2)
Contrast long bone and flat bone ossification patterns.
- Long bone use cartilage and undergo endochondral ossification
vs.
- Flat bones do not utilize cartilage and undergo intramembranous ossification
Compare and contrast immature and mature bone
Immature
- no lamellae
- cells randomly arranged (in lacuna)
- has vasculature, but not organized
Mature
- concentric lamellae
- made of organized cells in osteons (lacuna)
- vascular & nerve elements in Volkmann’s and Haversian canals
Describe the structure of an osteon an its components.
Osteon made of concentric rings, lamellae, with osteocytes in lacuna attached to each other by canaliculi with a hole in the center for vessels (Haversian canal). Volkmann’s canals run parallel to the osteon. There are also interstitial lamella that don’t make up a full osteon, but fill in the gaps in between.
What is different about an osteocyte during different functional stages?
In order of increasing maturity:
1. osteoprogenitor cells: renewable like a stem cell - come from bone marrow
2. osteoblasts: secrete type I and V collagen (building bone)
3. osteocytes: surrounded by calcified matrix - make hydroxyapatite
- osteoclast: from whole separate cell lineage in marrow - closely related to macrophages - fx: remodeling - close to osteoblasts on sides of bone communicate via gap junctions
What is the biggest difference between endochondral and intramembranous ossification types?
the types of bones and the usage of cartilage
Describe bone remodeling.
- osteoclasts are activated and reabsorb at the epiphyseal plate in the absorption zone
- osteoblasts come in and make Type II collagen which forms a reticular fiber mesh framework for a foundation
- osteoblasts make type I collagen laid on Type II framework and bone growth continues
2 zones: 1. cutting zone 2. closing zone
Describe hormones used in calcium homeostasis.
- parathyroid hormone (PTH) - activated with low blood calcium levels
- calcitonin - activated with high blood calcium levels
Parathyroid hormone
- excreted by parathyroid
- activated with low blood Ca
- decreases kidney release of Ca
- increases absorption of Ca in small intestine
- directly bind to osteoclasts to activate
- increase PO4 excretion by kidneys
Calcitonin
- excreted by thyroid
- prohibits PTH from binding to osteoclasts (agonist)
- activated with increase blood calcium
