5.1 - Intro to Cartilage and Bone Flashcards
What are chondroblasts?
Cells that secrete cartilage matrix
What are chondrocytes?
Cells that secreted cartilage matrix and became embedded in it
What type of cell produces cartilage matrix?
Chondroblasts
What type of cell is a component of cartilage matrix?
Chondrocytes
From which embryonic tissue does cartilage originate?
Mesenchyme
From which embryonic tissue do chondroblasts originate?
Mesenchyme
What are the 2 main components of cartilage?
- Cells (chondroblasts and chondrocytes)
2. ECM (collagen and proteoglycan complexes)
What are the 2 types of cells found in cartilage?
- Chondroblasts
2. Chondrocytes
What are the 2 components of cartilage’s ECM?
- Collagen
2. Proteoglycan complexes
Large proteoglycan molecules have numerous side chains of ___.
GAGs (glycosaminoglycans)
GAGs have strong negatively charged surfaces. What is the impact on this re: their water binding properties?
Strongly hydrophilic
Why is water attracted to highly charged molecules?
It is polarized
Why is cartilage well-hydrated?
ECM contains many GAGs, which are negatively charged and attract water molecules
Wet cartilage swells to form a hydrated gel. What restricts the swelling of this gel?
Tension in the collagen network
What is the name for the layer of dense irregular connective tissue surrounding certain types of cartilage?
Perichondrium
What is the perichondrium?
Layer of dense irregular connective tissue surrounding certain types of cartilage
Compare the two layers of perichondrium.
Outer: fibrous, contains fibroblasts, produces collagen
Inner: chondrogenic, undifferentiated, produces chondroblasts or chondrocytes
What is the fetal precursor to bone?
Hyaline cartilage
Most hyaline cartilage in the embryo is replaced by bone. What is the fate of remaining hyaline cartilage?
Forms growth plates and articular cartilage
What tissue is found in nearly all joints, between bones, and in structures that must be deformable, but strong?
Cartilage
What is chondrification?
When mesenchymal cells differentiate into chondroblasts to form cartilage
What is a primary ossification centre?
First area of a bone to start ossifying
What is a secondary ossification centre?
An area of ossification that appears after a primary officiation centre
Compare primary and secondary ossification centres.
Primary: first site of ossification, prenatal development, located on diaphyses
Secondary: appears after primary site, postnasal and adolescent years, located on epiphyses
When do primary ossification centres tend to appear?
Prenatal development
When do secondary ossification centres tend to appear?
Postnatal and adolescent years
On which part of the bone do primary ossification centres usually appear?
Diaphyses
On which part of the bone do secondary ossification centres usually appear?
Epiphyses
In children, primary ossification centres appear in the diaphyses and secondary ossification centres spear in the epiphyses. Which structure separates them?
Epiphyseal growth plate
Bone elongation halts once the growth plates close. How are bones still able to thicken?
Mesenchymal reservoir in the periosteum capable of differentiating into osteoblasts (i.e., intramembranous ossification)
What cells extend the epiphyseal growth plates?
Stacks of proliferating chondrocytes
What are the 4 zones of bone elongation at epiphyseal growth plates?
- Proliferation zone (cartilage cells proliferate, lengthening the bone)
- Hypertrophic zone (older cartilage cells hypertrophy, compressing the matrix)
- Calcification zone (matrix calcifies)
- Ossification zone (osteoblasts lay down osteoid)
Which bones of the developing body are first to ossify?
Clavicles
What is the most commonly broken bone in the body?
Clavicle
Compare the epiphysis, metaphysis, and diaphysis.
Epiphysis: rounded end of a long bone
Metaphysis: narrow portion of the long bone between the epiphysis and diaphysis
Diaphysis: shaft of a long bone
What are the 3 types of cartilage?
- Hyaline
- Elastic
- Fibrocartilage
What type of collagen forms hyaline cartilage?
Type II
What type of collagen forms elastic cartilage?
Type II
What type of collagen forms fibrocartilage?
Type I
What is the most common type of cartilage?
Hyaline
Is cartilage a living tissue?
Yes
Is cartilage innervated?
No
Is cartilage vascularized?
No
Cartilage is living, but avascular. How does it receive its nutrients?
Hyaline/Elastic: diffusion from perichondrium
Fibrocartilage: diffusion from surrounding tissues
What type of connective tissue makes up the perichondrium?
Dense irregular
Hyaline cartilage receives its nutrients via diffusion from the ___.
Perichondrium
Perichondrium is usually found at the margins of hyaline cartilage. Which surface is an exception?
Articular surfaces
Why wouldn’t you find perichondrium lining hyaline cartilage at articular surfaces?
The perichondrium highly vascularized and innervated; the compression and movement in the area would aggravate it
List 2 places where you would find perichondrium.
- Elastic cartilage
2. Hyaline cartilage (except on joint surfaces)
What type of cartilage calcifies with old age?
Hyaline
What is the result of articular cartilage degeneration?
Osteoarthritis
What is the result of articular cartilage destruction by granulating synovial membrane tissue?
Rheumatoid arthritis
What causes a slipped disc?
Rupture of intervertebral disc capsule
What type of cartilage is found in menisci?
Fibrocartilage
How does weight-bearing exercise protect against osteoporosis?
Encourages remodelling
Compare the histological appearance of hyaline cartilage, elastic cartilage, and fibrocartilage.
Hyaline: smooth ECM
Elastic: prominent elastic fibres in ECM
Fibrocartilage: prominent collagen fibres in ECM
Compare the location of chondroblasts and chondrocytes.
Chondroblasts: close to perichondrium
Chondrocytes: throughout ECM
Compare the histological appearance of chondroblasts and chondrocytes.
Chondroblasts: flattened, irregular, close to perichondrium
Chondrocytes: ovular, in lacunae, throughout ECM
Which cartilage cell is flat and irregular?
Chondroblasts
Which cartilage cell is ovular and enclosed by lacunae?
Chondrocytes
List 4 places where you would find elastic cartilage. (Hint: all begin with “e.”)
- Eustachian tube
- Ear canal
- External ear
- Epiglottis
What type of cartilage would you find in the Eustachian tube?
Elastic
What type of cartilage would you find in the ear canal?
Elastic
What type of cartilage would you find in the external ear?
Elastic
What type of cartilage would you find in the epiglottis?
Elastic
What is the name for the flap that diverts passage to the trachea or the esophagus?
Epiglottis
List 4 places where you would find hyaline cartilage.
- Articular surfaces
- Rib margins
- Respiratory passageways
- Tip of the nose
What type of cartilage would you find on articular surfaces?
Hyaline
What type of cartilage would you find at rib margins?
Hyaline
What type of cartilage would you find in the respiratory passageways?
Hyaline
What type of cartilage would you find in the larynx?
Hyaline
What type of cartilage would you find in the trachea?
Hyaline
What type of cartilage would you find at the tip of the nose?
Hyaline
List 6 places where you would find fibrocartilage.
- Pubic symphysis
- Menisci
- Articular discs
- Intervertebral discs
- Shoulder labra
- Hip labra
What type of cartilage would you find in the pubic symphysis?
Fibrocartilage
What type of cartilage would you find in the menisci?
Fibrocartilage
What type of cartilage would you find in the articular discs?
Fibrocartilage
What type of cartilage would you find in the intervertebral discs?
Fibrocartilage
What type of cartilage would you find in the shoulder labra?
Fibrocartilage
What type of cartilage would you find in the hip labra?
Fibrocartilage
What is the main function of hyaline cartilage?
Firm, flexible support
What is the main function of elastic cartilage?
Tolerate distortion without damage
What is the main function of fibrocartilage?
Strong, rigid support
What is endochondral ossification?
Osteoblasts from circulating osteoprogenitors invade hyaline cartilage to lay down osteoid
What are osteoprogenitor cells and where do they originate?
Cells that can differentiate into osteoblasts or chondrocytes
Originate from mesenchymal stem cells
What is osteoid?
The organic, un-mineralised portion of the bone matrix
What type of cells secrete osteoid?
Osteoblasts
What is the main component of osteoid?
Type I collagen
What is intramembranous ossification?
When osteoblasts differentiate from local mesenchymal cells to deposit osteoid
Where does intramembranous ossification take place?
Mesenchymal tissue
Compare endochondral ossification and intramembranous ossification.
Endochondral: osteoblasts from circulating osteoprogenitors invade hyaline cartilage to lay down osteoid
Intramembranous ossification: osteoblasts differentiate from local mesenchymal cells to deposit osteoid
By which method do most bones of the body develop?
Endochondral ossification
How do most flat bones develop?
Intramembranous ossification
Histologically, can you distinguish between bones arising from intramembranous ossification and bones arising from endochondral ossification?
No
What are the 2 ways cartilage can grow?
- Appositional growth
2. Interstitial growth
Describe appositional growth.
Fibroblasts in the perichondrium differentiate into chondroblasts and secrete new ECM
Describe interstitial growth.
Chondrocytes in isogenous groups (i.e., nests) separate as they produce more ECM
What are isogenous groups?
Nests of chondrocytes
What is a lacuna?
A hollow containing a chondrocyte in cartilage or an osteocyte in bone
What type of cartilage forms epiphyseal growth plates?
Hyaline
What is an epiphyseal growth plate and what is it made of?
Site of growth near the ends of long bones
Made of hyaline cartilage
How does bone grow at epiphyseal growth plates?
Chondrocytes undergo hyperplasia and hypertrophy followed by cell death and ossification
What happens after epiphyseal growth plates ossify?
Capacity for elongation is lost
Why are epiphyseal growth plates no longer visible in a fully grown adult?
Area has ossified
What are the 3 steps of fetal hyaline cartilage ossification?
- Cartilage model (general shape laid down by chondrocytes; surrounded by perichondrium)
- Bone collar (cartilage is calcified; perichondrium becomes periosteum)
- Primary ossification centre (blood vessels and osteoblasts invade calcified matrix; osteoid laid down)
How might fractures increase risk of osteoarthritis?
Wear down articular cartilage, which is slow to regenerate
What is the most common cause of total knee and hip replacements?
Osteoarthritis
Compare the effects of aging on hyaline cartilage and elastic cartilage.
Hyaline: calcifies with age
Elastic: does NOT calcify with age
What are the 2 components of fibrocartilage?
- Dense regular connective tissue
2. Hyaline cartilage
What type of cartilage lacks a perichondrium?
Fibrocartilage
Fibrocartilage has no perichondrium. From where does it receive its nutrition?
Surrounding tissues
What are the 2 primary function of menisci in the knee?
- Provide CUSHIONING between tibia and femur
2. Prevent DEGENERATION of articular cartilage underneath
Compare the most common causes of meniscal lesions in young people and middle-aged/elderly people.
Young: sports-related injuries
Middle-aged/elderly: degeneration from overuse
What are the 5 main functions of bone?
- Provide support
- Protect organs
- Enable movement
- Store minerals
- Produce RBC and WBC
Compare the axial and appendicular skeleton.
Axial: bones of the head, neck, and trunk
Appendicular: bones of the limbs, shoulder, and pelvis
What are 3 areas that make up the axial skeleton?
- Head
- Neck
- Trunk
What are 3 areas that make up the appendicular skeleton?
- Limbs
- Shoulder
- Pelvis
What are the 6 bone shapes?
- Long
- Short
- Flat
- Irregular
- Sesamoid (round bones that reinforce tendons)
- Pneumatic (contain air spaces)
What type of bone reinforces tendons?
Sesamoid
What type of bone contains air spaces?
Pneumatic
Bone is composed of both organic and inorganic matter. The ___ minerals give it its rigidity.
Organic
Bone is composed of both organic and inorganic matter. The ___ collagen gives it its flexibility/resistance to tension.
Inorganic
What gives bone its rigidity?
Minerals (i.e., calcium hydroxyapatite crystals)
What gives bones its flexibility/resistance to tension?
Collagen
What are the 2 types of bones?
- Spongy bone
2. Compact bone
What is a synonym for compact bone?
Cortical bone
Spongy bones consists of fine, bony columns. What fills the spaces?
Bone marrow
Describe the structure of spongy bone.
Fine, bony columns with bone marrow filling the spaces
What type of bone is abundant in the epiphysis?
Spongy bone
Where would you find compact bone?
External surfaces of bones
What percentage of skeletal mass is formed by cortical bone?
80%
Compare the placement of Haversian canals and Volkmann’s canals.
Haversian: at the centre of osteons
Volkmann: connecting adjacent osteons to the periosteum; PERPENDICULAR to Haversian canals
What are Haversian canals?
Channels of nerves, vessels, and lymphatics at the centre of osteons
What are Volkmann’s canals?
Channels of nerves, vessels, and lymphatics connecting the periosteum to osteons
What is an osteon?
Basic unit of cortical bone; consists of lamellae surrounding a Haversian canal
What is the periosteum?
Dense irregular connective tissue covering bones, except at articular surfaces
What is a lamella?
A concentric layer of bone tissue
What do lacunae contain in bone?
Osteocytes
What do lacuna contain in cartilage?
Chondrocytes
What are canaliculi?
Tiny canals connecting adjacent lacunae
How do osteocytes communicate with each other?
Via canaliculi
Does spongy bone contain either Haversian or Volkmann’s canals?
No
What are trabeculae?
Honeycomb-like bone tissues found in spongy bone
Compare the internal structure of osteons and trabeculae.
Osteons: DO contain Haversian and Volkmann’s canals, round lamellae
Trabeculae: DO NOT contain Haversian or Volkmann’s canals, irregularly-shaped lamellae
What are the 2 types of cells found in bone marrow?
- Adipose (yellow marrow)
2. Hemopoietic (red marrow)
What is a spicule?
Projection of new forming bone
Compare the location of osteoblasts, osteoclasts, and osteocytes in an osteon
Osteoblasts: near edges
Osteoclasts: near edges
Osteocytes: all over
Compare the functions of osteoblasts, osteoclasts, and osteocytes.
Osteoblasts: build bone
Osteoclasts: break down bone
Osteocytes: maintain bone
What is a cutting cone?
A bone remodelling unit; osteoclasts break down bone and trailing osteoblasts lay down new bone
What are the 3 zones of a cutting cone?
- Cutting zone
- Reversal zone
- Closing zone
Compare the activities occurring in the 3 regions of a cutting cone.
Cutting zone: osteoclasts break down bone
Reversal zone: mix of osteoclast and osteoblast avidity
Closing cone: osteoblasts lay down new bone
How would you increase the number of cutting cones you have?
Mechanical loading
What happens to bone density in outer space?
Decreases due to reduction in gravitational forces
How does sport cause bone hypertrophy?
Increased remodelling
List 3 factors that decrease rate of bone remodelling.
- Low gravity
- Age
- Inactivity
Normally, lamellae are able to slip relative to each other to help disperse forces. What happens when this fails?
Fracture
Why would a bone fracture cause pain?
Damage to nerves
What are the 4 steps of fracture repair?
- Hematoma formation (blood clot)
- Fibrocartilaginous callous formation (fibres and cartilage)
- Bony callus formation (spongy bone)
- Remodelling (compact bone)