Anatomy Lesson 4 - Cartilage and Bone Tissue

describe the composition, function and distribution of fibrocartilage

• composition: thickest out of all three cartilage; contains thick collagen fibers hence little ground substance; parallel collagen fibers; no perichondrium(dense irregular connective tissue layer that surrounds cartilage)

• function: shock absorber (not elastic nor flexible so it’s a shock absorber)

• location: intervertebral discs, pubic symphysis, menisci of knee, articular discs of jaw

describe the function and distribution of hyaline cartilage

most prevalent in our body

function: supports soft tissue; flexible but resilient

location: respiratory system (larynx, trachea, bronchi), costal cartialge, nose, articular cartilage, epiphyseal plate, fetal skeleton(most of fetus is cartilage not bone)

(**to remember which are hyaline cartilage, memorize fibrocartilage and elastic cartilage and the rest of the cartilage are hyaline cartilage)

describe the composition, function and distribution of elastic cartilage

composition: small amount of ECM; elastic fibers form weblike mesh around lacunae which…(continue to functions)

function: thinnest cartilage allows elasticity and flexibility

location: epiglottis (covers respiratory tract when we swallow food/water), external ear

(**to memorize, realize that Elastic, Epiglottis, and Ear all starts with the letter E)

which connective tissue is cartilage a part of?

supportive connective tissue

list the cartilages from thickest to thinnest

fibrocartilage > hyaline cartilage > elastic cartilage

What are the components of (general) cartilage? Define them

chondroblasts: cells that produce cartilage matrix

lacunae: “cave“ where chondrocytes live

chrondrocytes: mature cartilage cells that reside in lacunae

ECM: protein fibers and ground substance

perichondrium: dense irregular connective tissue

what are the functions of cartilage

• support soft tissues

• provide articular/gliding surface for joints

• provide a model for endochondrial

  • bone formation (cartilage serves as a rough draft for bone tissue)

what are the characteristics of cartilage

• semirigid, weaker than bone

• flexible & resilient due to elastic fibers and water content

  • avascular, therefore receives nutrients via diffusion

what are the functions of bone

• support & protect: creates framework of body and protects vital organs from injury

• movement: bone serves as attachment sites for muscles

• hemopoiesis or hematopoiesis (same thing): makes RBCs from red bone marrow

• storage of minerals and energy reserves: calcium phosphate and yellow bone marrow(as humans mature, red bone marrow degenerates to become yellow BM and w/in the yellow BM of shaft and long bones is potential energy stored as lipids)

identify the characteristics of long bone and classify them

long bones are longer than wide, they include…

• humerus

• radius and ulna

• metacarpals and metatarsals

• phalanges (hands and feet)

• femur

• tibia and fibula

classify short bones

carpels, tarsals, sesamoid bone on the patella (knee bone)

classify flat bones

skull, scapulae, sternum and ribs(*ribs are tricky bc one might think they’re long bones but in reality they are curved but flat)

classify irregular bones

vertebrae, sacrum, coccyx, os coxa, thmoid and sphenoid

what is another name(s) for compact bone

cortical bone

what is another name(s) for spongy bone

cancellous or trabecular

label the structures of long bone

define: medullary cavity, endosteum, periosteum, perforating fibers

• epiphyseal plate/line is found within the metaphysis

  • epiphyseal plate is made of cartilage in children, it’s a growth plate

  • epiphyseal line is in adults, and it is NOT made of cartilage

• medullary cavity: inside of bone (cortex is on the outside of the bone)

  • contains yellow bone marrow in adults and red in children

• endosteum: membrane(not bone); layer of cells lining the spongy bone and medullary cavity

• periosteum: membrane(not bone); dense regular CT, outer covering of diaphysis of long bone; lines the compact bone on the outside

  • provides stem cells for bone growth and fracture repair

• perforating fibers: what holds the periosteum to the bone

list in order of superficial to deep the layers of bone

(superficial) periosteum, compact bone, spongy bone, endosteum (deep)

differentiate between osteoprogenitor cells, osteoblasts, osteocytes, and osteoclasts in terms of function and location

osteoprogenitor cells: stem cells of bone

osteoblasts: ones that build bone by secreting osteoid(bone matrix)

osteocytes: mature bone cells that maintain bone matrix; osteocytes are encased in matrix called lacunae

osteoclasts: consumes bone (bone resorption)

describe the lifecycle of an osteoprogenitor cell

either mesenchyme or osteoprogenitor cell becomes osteoblast which then becomes osteocyte

what is bone matrix (aka bone extracellar matrix) made of? Which component is organic and which is inorganic?

made up of osteoid (collagen), which is secreted by osteoblasts, and calcium phosphate

Osteoid is organic and calcium phosphate is inorganic so we need it from our diet

[**way to remember] Osteoid is Organic (both starts with “O”s)

describe the structure of a typical flat bone

(think of it like a sandwhich) Periosteum > compact bone > spongy bone > compact bone > periosteum

compact bone and spongy bone are both lined with periosteum

label the cross section of a compact bone

What is an osteon of compact bone and what’s its alternative name

aka Haversion system; basic functional/structural unit of mature compact bone

what is a central canal of compact bone and what is the alternative name

aka Haversian canal; cylindrical channel that lies in the center of osteon; blood vessels and nerves run w/in the canal and supplies the bone

what is a concentric lamellae of compact bone

rings of bone connective tissue that surround central canal and form the bulk of osteon

where is osteocyte located in a compact bone

housed in lacunae and occur b/t adjacent concentric lamellae

what is a canaliculi

tiny channels/passageway b/t central canal and osteocytes allowing minerals, nutrients, gases and wastes to travel to supply nutrients to osteocytes

what is a perforating canal and what is its alternative name

aka volkmann’s canal; runs perpendicular to central canals and help connect multiple central canals creating a vascular innervation connection among the multiple osteons; contains blood vessels and nerves

[**way to remember: you take a volkswagon bug across perforating caval b/t central canals]

how is a spongy bone different from a compact bone

it has tribeculae (crisscrossing bars and plates between compact bone that provide resistance to stress coming from all directions and distributes stress throughout framework)

it has parallel lamellae, osteocytes, and canaliculi but NO osteon or perforating canal bc there are no central canals like there is in compact bone

summarize the process of intramembranous ossification and the bones formed from it

aka dermal ossification; growth within a membrane that forms bones from clavicle and up

Process: mesenchymal cells become osteoblasts, which then secretes osteoid which then goes thru calcification when it comes in contact with calcium phostphates and forms a calcified matrix which traps some osteoids which then becomes osteocytes

(**specifics of the process is not really important to know for this course but know general process)

summarize the process of endochondral ossification and the bones formed from it

bone growth within a cartilage; turns fetal framework of hyaline cartilage into bone, formation of most bones but specifically bones from clavicle down (NOT including the clavicle)

Process:

1. Fetal hyaline cartilage model develops

2. cartilage calcifies and periosteal bone collar forms around diaphysis

3. primary ossification center forms in the diaphysis

4. secondary ossification centers form in epiphyses

5. bone replaces cartilage, except the articular cartilage and epiphyseal plate

6. epiphyseal plate ossifies and becomes epiphyseal line

(**specifics of the process is not really important to know for this course but know general process)

how does bone grow in length, what is it called?

interstitial growth:

• occurs at the epiphyseal plate

• Process: chondrocytes at the epiphyseal plate go thru cell division

  • this division pushes the zone of resting cartilage toward the epiphysis (flexible matrix of hyaline cartilage permits this growth)

  • this hyaline cartilage is later replaced w/ bone (endochondral ossification)

how does bone grow in thickness (width), what is it called?

appositional growth: occurs at the periosteum and endosteum

Process: osteoclasts in the inner cellular layer of the periosteum lay down bone matrix in layers

• as the number of these layers increase, the structure widens. as new bone is being laid down, osteoclasts along the medullary (inside) cavity resorbs bone matrix, making an expanded, wider hollow medullary cavity

what are the four different types of bone fractures? Define them

simple fractures: bone doesn’t pierce skin

open/compound fracture: bone pierces skin

stress fracture: think break from repetitive loads

pathologic fracture: disease weakens bones (such as osteoporosis)

explain how bone fractures are repaired

1. fracture hematoma forms where blood pools in the area where the bone fracture teared the blood vessels

2. fibrocartilage (soft) callus forms and produce collagen fibers that help connect broken ends of bones

3. hard (bony) callus forms: osteoprogenitor cells next to soft callus becomes osteoblasts and make trabeculae of primary bone. Soft callus is replaced by bone which forms hard callus

4. bone is remodeled: osteoclasts remove excess bony material and primary bone is replaced with compact bone

*periosteum provides stem cells for bone growth and fracture repair

Bone Disorder: osteomalacia

called rickets in children > soft bones which leads to bowed legs

Possible causes: vit D deficiency, calcium deficiency

Bone Disorder: osteoporosis

excessive bone resorption due to aging and post-menopause

Bone Disorder: osteitis deformans

aka Paget’s disease

• excessive osteoclast and osteoblast function

• bone is unstable and immature, so it’s more susceptible to fractures and deformation

• most common in os coxa, skull, vertebrae, femur and tibia

ossification begins in the embryo (T/F)

TRUE

vitamin A activates

osteoblasts

vitamin C is required for

normal synthesis of collagen

vit D stimulates

absorption and transport of calcium and phosphate ions into blood > basically strengthens bone