josh bones

Question 1

what is the ECM and its key role

Answer 1

Extracellular matirx
An insoluble network of macromolecules secreted by cells into their immediate environment, it acts like a glue, holding the cells together. it is also made from meshwork of fibrous protiens in a gel-like substance composed of complex CHOs.

Question 2

ist some purposes of the ECM

Answer 2

Cell adhesion, migration & formation of epithelial sheets & tubes all depend on ability of cells to form attachments to ECMs
Attachments are either extremely strong, or need to be made, broken, and made again
Can act as a permissive substrate to which cells can adhere, or migrate, or it can provide directions and signals
Growth factors are inside the ECM

Question 3

what type of macromolecules are inside the ECM

Answer 3

Glycoproteins and proteins
Glycosaminoglycans and proteoglycans

Question 4

what are some types of glycoportiens/ protiens in the ECM and their role

Answer 4

Collagen - mechanical support and architecture of the body with at least 20 types
Elastin - gives the boody elasticity, breaks down with age
Fibronectin - general adhesion molecule, acts to bind multiple cells to another and also cells to substrate

Question 5

what are some types of Glycosaminoglycans / proteoglycans in the ECM and their role

Answer 5

heparan sulfate, chondroitin sulfate, Hyaluronan
Critical role in delivery of paracrine factors - the hormone travels through the interstitial fluid in the ECM.

Question 6

what is the basal lamina and what is it made of

Answer 6

the basement membrane is a type of ECM which is characterised by closley knit sheets surronding epithelial tissue.
Important role in assembling ECM helps to anchor cells
Designed & maintained primarily by specialised cells fibroblasts

Question 7

what are the functions of integrins

Answer 7

Activate specific pathways
Widely expressed family of cell surface glycoprotein receptors linking ECM to cellular cytoskeleton
Binding of integrins to ECM substrate cells extend over a large surface area

Question 8

matrix metalloproteinases degregation is important for what

Answer 8

blood vessels foramtion and other tissues

Question 9

how does proteoglycans influence meat quality

Answer 9

H2O-holding capacity (decreased juiciness)

Question 10

how does collagen effect meat quality

Answer 10

Skeletal muscle primarily made of Type I & Type III collagen
Animal matures & ages, from Type III to Type I collagen & cross-linking in skeletal muscle increased toughness

Question 11

what is a chondrocytes

Answer 11

mature carilage cell, undifferentiated, found in the mature cartilage in lacunae. They are elongated spherical.

Question 12

cartilage matrix if fromed from what

Answer 12

Water: the most abundant compete (60-80%) of weight. They will be in the interfibrillar spaces within the collagen and hold inorganic ions (minerals)
Collagen: most common structural macromolecules, they are mostly type 2.
Proteoglycans: heavily glycosylated proteins. Compromise of a protein core (GAG)

Question 13

what are the three types of cartilage (weakest to strongest)

Answer 13

hyaline, elastic, fibrocatilages

Question 14

what are the characteristics of hyline cartilage

Answer 14

Most common, it is white, translucent and is in the center of bones for ossificaation.
Contains chondrocyte (relatively sparse)

Question 15

what are the characteristics of elastic cartilage

Answer 15

Provides elasticity and rigidity
Dense network of elastic fibres
higher amount of chondrocytes and have elastic fibers running along an axis which creates the elasticity

Question 16

what are the characteristics of fibrocartilage

Answer 16

Contains prominent type I collagen fibres forming discrete bundles
Chondrocytes present in rows
These are the strongest hence they are put in the vertebrae where the most pressure is placed.

Question 17

what are osteoprogenitor cells (origin, role, function, appearence)

Answer 17

Derived from mesenchymal stem cells
Osteoblast precursor cells
Able to divide and proliferate
Found on internal and external surfaces of bone
Periosteal and endosteal surfaces
Flattened elongated cells with an oval nucleus

Question 18

what are osteoblasts function and appearence

Answer 18

Secrete the ECM of bone, forming the tissue.
Cover bone everywhere except over articular cartilage.

cuboidal to columnar in shape with nucleus away from the surface.
Basophilic cytoplasm rich in rER and ribosomes.

Question 19

what order do the bone cells differentiatite into.

Answer 19

osteoprogenitor -> osteoblast ->osteocytes

Question 20

what are osteocytes function and appearence

Answer 20

Mature cells of bone
Theyy are enclosed by matrix which they maintain via cytoplasmic processes in canaliculi communicate with neighbouring cells by gap junctions.
they have less rER than osteoblasts

nucleuc in the ceter with long cancaliculi

Question 21

what are osteoclasts function and appearence

Answer 21

removes the bones by forming sallow despressions called Howships lacunae.

they are a large multinucleated cell with a ‘ruffled border’

Question 22

what importance does the pH have on bone

Answer 22

low pH stimulates osteoclasts activity to break down bone and inhibts osteoblasts.
- high exposure can lead to weak bones, fracture or disease.

Question 23

what is spongy bone

Answer 23

lighter, porus and are the iner ccenter of long bones.

Question 24

what is compact bone

Answer 24

stronger and desner they have a hard bone cortext

Question 25

describe some key aspect of bones (imagine a close diagram)

Answer 25

periosteum surronds the compact bone and edostum surronded the inner layer (spongy). and osteon are multiringed layers with an osteonal canal (haversian canal) in the center. between these rings are lamellae. the haversian calans are linked via volkmanns canals.

Question 26

describe some key aspect of long bones (imagine a general long bone diagram)

Answer 26

epiphysis - most distal and proximal area which includes the growth plate. metaphysis - area of narrowing diaphysis - area most narrow and elongated. articular cartilage, surronded the buld around the growth plat. periosteum - outer layer of bone

Question 27

what are the three types of joint

Answer 27

fibrous, cartiligenous, synovial

Question 28

describe a fibrous joint

Answer 28

Held together by fibrous connective tissue, they have no capacity for space between bones and do not move. there are three types: sutures (skull), syndesmosis (band of connective itusse, between tibia and fibula), gomphoses (teek sockets)

Question 29

describe a cartiliginous joint

Answer 29

two bones connected by cartilage there ae two types: synchondroses: Bones are joined by hyaline cartilage, Found in the epiphyseal plates of long bones Symphyses: Bones are joined by fibrocartilage, this is much stronger than hyaline. (pubic, vert)

Question 30

describe a synovial joint

Answer 30

Joints that have a space between the adjoining bones. Enclosed by synovial membrane. Cavity contains lubricating fluid, synovial fluid Synovial fluid lubricates the joint, reducing friction between bones - allows greater movement Opposing bones covered by articular cartilage. Divided into three zones: superficial, middle and deep

Question 31

what are the two types of ossificiation

Answer 31

Endochondral: the multiplication of the hyaline cartilage cells in the physis causes increased length, this method is used in the developing embryo through the continuous replacement of the cartilage by bone. Intramembranous: the process of bone development through fibrous membrane, this forms flat bones.

Question 32

explain to process of endochondral ossification

Answer 32

Stage 1 Chondrocytes in the center enlarge and the cartilage in the matrix becomes calcified. The surrounding cells will then undergo programmed death, leaving behind a cavity within the cartilage matrix. Stage 2 The perichondrium of the cartilage model becomes transformed into a periosteum as an osteogenic layer forms. The periosteum produces a thin collar of bone around the shaft of the cartilage model Stage 3 Blood vessels and osteoprogenitor cells from periosteum migrate into the cavities within the calcified cartilage matrix. The calcified cartilage breaks down and provides a surface on which osteoblasts can produce spongy bone. This then becomes a primary ossification center Stage 4 As osteogenesis continues in the primary ossification center, a cavity results as the bone is remodeled. This central cavity is called the marrow cavity. Further growth involves an increase in both the length and diameter of the bone Stage 5 Secondary ossification centers appear in the epiphyses Stage 6 Epiphyses become filled with spongy bone and only a thin piece of hyaline cartilage remains on the articular surface as articular cartilage. A thin plate of cartilage, the epiphyseal plate, now separates the bone of the epiphyses from that of the diaphysis.

Question 33

how do bones grow in length

Answer 33

Occurs by growth of the epiphyseal plate cartilage at both ends of the bone

Question 34

what are the 5 zones of the epiphyseal plate

Answer 34

Closest to epiphyseal plate Reverse: Contains small chondrocytes within the matrix Proliferate: Slightly larger chondrocytes that undergo mitosis Hypertropic: The chondrocytes enlarge and compress the matrix surrounding them Calcifaction: The enlarged cells begin to degenerate and die as the matrix around them are calcified Ossification: The cavities left by the dead chondrocytes are invaded by blood vessels containing: osteoprogenitor cells > osteoblasts > bone formation Furtherst to epiphyseal plate

Question 35

Describing how bones widen

Answer 35

Occurs by the addition of bony tissue at the surface of bones - appositional growth Growth in the diameter continue even after longitudinal growth ceases Appositional growth can occur at the endosteum or periosteum Osteoclasts resorb the old bone that lines the medullary cavity Osteoblasts deposit the new bone

Question 36

what is bone remodeling

Answer 36

Process by which old bone is continuously replaced by new one. Is essential for changes in bone shape during growth

Question 37

what cells are responsible for bone regrowth

Answer 37

osteoblasts and osteoclasts

Question 38

What is the basic multicellular unit

Answer 38

The clusters of osteoclasts and osteoblasts that are involved in the resorption and formation of bone, in each area of bone that is undergoing remodelling, are arranged within temporary anatomical structures known as “basic multicellular units” (BMU)

Question 39

Each BMU encased by bone-lining cells which creates a unique environment alowwing what to take place?

Answer 39

coupled resorption-formation

Question 40

there are four step in bone remodeling, what are they

Answer 40

Activation, Resorption, Reversal, Formation

Question 41

during the activation step in bone remodeling, what occurs?

Answer 41

Detection of the initiation remodeling signal. This signal is a direct mesenchymal strain on the bone that results in structural damage. The hormone (PTH sensed by osteocytes > biological signals for bone remodelling. This is how skeletons differ based on lived practices like jobs and weight ect.

Question 42

during the Resorption step in bone remodeling, what occurs?

Answer 42

Activated osteoclasts resorb the bone Resorbing osteoclast secrets H+ ions lowering the pH to 4.5 within the bone resorbing compartment to mobilise the minerals Secrete enzymes such as matrix metalloproteinases to digest the organic matrix Results in formation of cavities- called Howship’s lacunae Osteoclasts undergo apoptosis ending the resorption phase

Question 43

during the Reversable step in bone remodeling, what occurs?

Answer 43

Major characteristic is that mononuclear cells (monocytes/macrophages), osteocytes and pre-osteoblasts appear on the resorption cavities These cells are also referred to as reversal cells These cells removes the collagen remnants, prepare the surface for new osteoblasts to begin bone formation Reversal cells also provide signals for osteoblast differentiation and migration

Question 44

during the Formation step in bone remodeling, what occurs?

Answer 44

Proliferation of mesenchymal cells Differentiation into osteoblast precursor cells Maturation of osteoblasts Formation of matrix And finally mineralization

Question 45

Discuss the role RANKL/RANK/OPG signalling

Answer 45

signal for bone remodeling RANKL - on the osteoblasts RANK - on the osteoclasts OPG - secreted by the osteoblasts RANK L binds to RANK and bind to cause to osteoclasts to break down bone RANKL binds to OPG, this prevents the binding for RANK, slowing bone absoprtion.

Question 46

if there is a high OPG to RANKL ratio, what effect does this have on bone formation

Answer 46

inhibits osteoclast differentiation and favours the bone formation

Question 47

if there is a low OPG to RANKL ratio, what effect does this have on bone formation

Answer 47

promotes osteoclast differentiation, favoring bone reabsorption.

Question 48

why is calcium important

Answer 48

bones retain 99% of calcium and 85% of phosphate. cofactor for blood clotting important for signalling (intracellular)

Question 49

what roles does PTH play in calcium homeostasis

Answer 49

parathyroid hormone is synthesised by the parathyroid gland, it effects to bones, intestine and kidneys. Bone: enhances bone reabsorption, breaking down and taking minerals Kidney: increases calcium uptake and activates vit D3 Intestin: Vit D3 increases calcium absorption

Question 50

what roles does 1,25-dihydroxy vitamin D3 play in calcium homeostasis

Answer 50

Vit D sythesized in the skin, then liver and finaly in the kindey, this finally produces active vitamin D 3 PTH helps activate the synthesis in the kindies. Works in intestine to increase calcium uptake

Question 51

what roles does Calcitonin (CT) play in calcium homeostasis

Answer 51

synthesied by C cells in the thyroid gland. decreased Calcium in the blood by: inhibiting intestine Ca uptake. inhibits kidney Ca reabsorption promotes deposition of calium in the bones

Question 52

list the three hormones which play a large role in calcium homeostasis

Answer 52

calcitonin Parathyroid hormone (PTH) 1,25-dihydroxy vitamin D3

Question 53

what is Osteochondrosis

Answer 53

impaired endochondral ossification in the growth plate leading to structural weakness and fracturing or bone distortion. Caused by the necrosis of vessels in the cartilage canals (ischemia of growth cartilage) and results in a failure of the blood supply.

Question 54

what is Dyschondroplasia

Answer 54

Growth plate disorder common in poultry. It is an abnormal cartilage mass under the growth plate of long bones. This is commonly observed in the proximal tibiotarsus and that’s why it is also called as tibial dyschondroplasia (TD) Can also be observed in proximal and distal femur, distal tibia and proximal humerus Affected chickens reluctant to move and lame

Question 55

what is rickets

Answer 55

Disease that has a bone growth plate, leading to insufficient growth. This is commonly caused by dietary insufficiency of phosphorus or vitamin D. Failure of mineralisation of osteoid and cartilaginous matrix, especially in the growth plate