Muscoskeletal

Question 1

What are the two main skeletal regions, # of bones and the main regional differences in function

Answer 1

Axial skeleton (core) : 80 bones (some paired)
Appendicular skeleton (outside) : 126 bones ( all paired)
-Regional differences is that axial is mainly for support/protection and has Haemopoeisis and -Appendicular is for movement and fat storage

Question 2

What are the 6 functions of the skeletal system

Answer 2

Support (hand soft tissue),
Protection (hard and dense),
Movement (framework for pulling),
Ca+ (for AP& muscle contraction) and Phosphorous (building body) reserves,
Haemopoeisis (red bone marrow)
Fat storage (yellow bone marrow)

Question 3

What is the regional zones of long bone

Answer 3

At the ends are the epiphyses, Then inwards of that there is are transitory region called metaphyses, and then middle is the Diaphysis.

Question 4

Describe the layers of Epiphysis from out to in

Answer 4

Epiphysis has 3 layers

Outermost is Articular cartilage: in contact with another bone
Thin layer of Compact bone
5 Blood vessels: (inside compact bone and between trabeculae-> into the medullary cavities)
Spongy bone- made of trabeculae covered in Endosteum with Medullary cavities in between containing red bone marrow.

Question 5

Describe the layers of Diaphysis from out to in

Answer 5

Outermost is the Periosteum (outer fibrocellular sheath surrounding bone).
5-3 Blood vessels and nerves in the periosteum to compact bone
Perforating Sharpey’s fibers: (provide strong anchorage of collagen fibres to transition Periosteum to compact bone- tendons attach here)
Thick layer of Compact bone
Endosteum : fibrocellular layer lining the medullary cavity
Medullary cavity: yellow bone marrow

Question 6

What are the main differences between the Epiphysis and the Diaphysis

Answer 6

The epiphysis receives uniform perpendicular forces like a roof, so therefore has trabeculae cross structures
The Diaphysis receives parallel compression forces therefore has a thick compact bone section like walls

Question 7

What is a connective tissue

Answer 7

It is Cells + ECM. ECM is made of fibres and grounds substance

Question 8

Compare the properties that make bone a specialised connective tissue : Fibres vs Ground substance (forces, organicness, dry weight) and Cells

Answer 8

Fibres: Type 1 Collagen=1/3 dry weight. Resists stretching/pulling force ( tension)

GS: Hydroxyapatite (Ca and P store) =2/3 dry weight. Resists crushing, squeezing force (compression)

Overall Bone resists Torsion (twisting force)

Cells: Osteo genic, blast, cyte, clast

Question 9

Describe the Precursor, location, function of Osteogenic cell/ Osteoprogenitor cell

Answer 9

Precursor: Unspecialised stem cell from Mesenchyme, the embryonic CT
Location: Surface of bone in the periosteum and endosteum. Also found in the central canals of compact bone
Function: Normally dormant/resting but can divide and supply developing bone with bone forming cells

Question 10

Describe the Precursor, location, function of Osteoblast cell

Answer 10

Precursor: Osteogenic cell
Location: Usually in the layer under the peri or endosteum of active bone-> wherever new bone is being formed
Function: Synthesis and depositation and calcification of the osteoid

Question 11

What is the osteoid

Answer 11

The organic ECM matrix (mostly collagen) of bone, synthesised by osteoblasts prior to mineral depositation.

Made of 70% collagen, 30% proteoglycans other proteins and water.

Question 12

What is calcification and its rate + limitations of rate

Answer 12

Calcification is the deposition of mineral salts, primarily hydroxyapatite in a framework of collagen fibres, making the tissue harden.

The rate is initially very fast but then gets very slow (years) because the calcification means that nutrient movement is slow because of dense + displacement of water.

Question 13

Describe the Precursor, location, function of Osteocyte cell

Answer 13

Precursor: Osteoblast
Location: Trapped within lacunae inside bone. Osteocytes can communicate with neighbouring cells through their long cellular processes inside caniculi

Function: Bone tissue maintenance through

live lattice inside bone
localised minor repair
Rapid Ca+ exchange

Question 14

What is the organic vs inorganic part of bone as a CT

Answer 14

Organic : Type 1 collagen (70%) 30% other proteoglycans + other proteins and water (fibres)
Inorganic is the hydroxyapatite =ground substance

Question 15

What is the precursor, location and function of Osteoclast

Answer 15

Osteoclasts are from a separate lineage: they come from the fusion of monocyte progenitor cells.

Location: At sites where bone reabsorption is occuring

Function: Secretes acid to dissolve the mineral and enzymes to dissolve the organic components of bone

Question 16

How does the osteoclast control the destructive enzymes

Answer 16

It has a clear zone close to its ruffled border which collects the enzymes that it secretes and forces it to be endocytosed so it can be neutralised. The enzymes are also only active in an acid environment.

Question 17

In what layers are the osteogenic cells in inactive bone and what does inactive bone not have ?

Answer 17

Layer under blood vessels in the periosteum, on top of the osteocytes

Under the mineralised bone, in the endosteum, on top of the medullary cavity where there is bone, marrow and bv.

Bones don’t have osteoblasts if inactive

Question 18

What does bone remodelling mean

Answer 18

Ongoing replacement of old bone tissue, involving bone reabsorption (removal of minerals and collagen fibres) by osteoclasts and appositional growth (addition of minerals and collagen fibres) by osteoblasts on existing bone.

Question 19

Describe the process of appositional growth 3 steps from active to inactive.

Answer 19

Osteogenic cells divide, forming osteoblasts which deposit osteoid
Some osteoblasts become trapped in the lacunae where they will eventually become osteocytes
When growth stops, osteoblasts can convert back to osteogenic cells or die. The osteoid is fully calcified

Question 20

Why does the bone grown appositional instead of interstitial

Answer 20

The tissue bone is too rigid for interstitial growth which involves the cells dividing inside the tissue, excreting more ECM and growing the tissue from within. It can only grow by having more stuff added on top.

Question 21

Are the appositional growth and bone reabsorption always happening at the same time. Where can they occur

Answer 21

No, they occur throughout the skeleton independently of each other. They can occur in the endosteum or the periosteum

Question 22

How do long bones grow in length and why does it do that

Answer 22

Endochondral ossification= There is a plate of hyaline cartilage that can grow by interstitial growth underneath the epiphysis which is the epiphyseal plate. This cartilage grows, dies then is replaced by bone.
It does it this way because it can’t lay bone down on the articulate cartilage on the ends.

Question 23

What is the two types of mature lamellar bone and what characterises this bone subset

Answer 23

Mature lamellar bone is characterised by many layers of bone, with collagen fibres put down in the same direction within one layer but alternating out of phase between layers. This enables bone to withstand forces from different directions.
The two types are spongey and compact bone

Question 24

Describe the structure of spongey/cancellous/trabecular bone and where you find it usually

Answer 24

Made of lamellae arranged in irregular thin columns called trabeculae. The spaces in between are filled with bone marrow (called medullary cavity). Usually found in the interior of a bone, always covered by compact bone for protection.

Question 25

What are the main different characteristics of spongey bone that is different to compact bone

Answer 25

spongey bone is light which allows the skeleton to move more readily spongey bone supports red bone marrow so is the site of haemotpoeisis Spongey bone is the site where bone remodelling is greater because the greater SA means that its easier for osteoclasts to settle on trabeculae to + and - Ca and P

Question 26

Describe the structure and organisation of compact/cortical bone and where you find it usually

Answer 26

Made of repeating osteons/haversian systems. This consists of concentric lamellae arranged around a central canal containing blood vessels and nerves. There are alternating arrangements of collagen fibres between lamellae.

Question 27

Compare how spongey bone and compact bone resist stresses- and therefore perform function

Answer 27

Spongey bone isn’t for heavy stresses but its trabeculae are orientated to resist stress from multiple directions and help to support outer cortex of compact bone. Whereas Compact bone is for heavier stresses, resisting bending because osteons are aligned in the same direction and parallel to the length of the diaphysis. It also thickens in area exposed to large forces.

Question 28

Whats the difference between circumferential lamellae and interstitial lamellae in compact bone

Answer 28

Interstitial lamellae is areas between neighbouring osteons that contain lamellae with osteocytes and canaliculi. They are fragements of older osteons destroyed during rebuilding. Whereas Circumferential lamellae is developed during initial bone formation and line the inner and outer boundaries of the compact bone.

Question 29

What lines the central canal

Answer 29

endosteum

Question 30

Describe 4 steps how a primary osteon forms from appositional growth

Answer 30

Osteoblasts in the active periosteum either side of the blood vessel put own new bone forming ridges Bone continues ridges come together and fuse forming a tunnel around the blood vessel. The tunnel is now lined with endosteum. The osteoblasts in the endosteum build concentric lamellae onto the walls of the tunnel. The tunnel fills inward toward centre The bone continues to grow outwards as the osteoblasts in the periosteum build new circumferential lamellae. Process repeats as new ridges fold over blood vessels

Question 31

Where and what purpose of primary osteon formation happen compared to secondary osteon formation

Answer 31

Primary osteon tunnel formation happens around existing blood vessels in the active periosteum, which happens when bone is growing. Whereas secondary osteons the tunnels are created inside existing bone to help repair/ increase vasculature.

Question 32

What are the 5 steps of forming a secondary osteon

Answer 32

Osteoclasts form and gather in an area that needs to be remodelled. They start boring its way through the existing bone. Osteoblasts move in behind the cutting cone and line tunnel wall as new endosteum and start depositing osteoid. Osteoid calcifies to form new lamella and a blood vessel will grow into the tunnel to supply the cells. Osteoblasts deposit layer upon layer of new concentric lamellae on the wall of the tunnel to fill it in. Some osteoblasts get trapped and become osteocytes When the tunnel is reduced to size of normal Haversian canal, remaining osteoblasts die or become osteogenic cells part of the resting endosteum.

Question 33

What is the cement line

Answer 33

This is the junction between the closests to outer surface lamella of the new osteon and the pre existing older bone. It is filled with GAGs which are glue between old and new bone.

Question 34

What is the closing cone

Answer 34

The active area of osteoblasts depositing new layers of concentric lamellae behind the cutting cone front of osteoclasts.

Question 35

Compare blood supply of spongy and compact bone and therefore nutrient flow

Answer 35

Spongy bone has blood vessels in medullary cavity so nutrient flow is outside to in but in Compact bone, blood vessels are within Haversian and Volkmanns canals. so flow is from inside to out.

Question 36

Compare the units of spongy bone and compact bone and their direction of growth

Answer 36

Spongey bone units are trabeculae that grow outwards. Whereas compact bone unit is haversian system/ osteon and grows inwards.

Question 37

What are the 3 types of structural classification of joints and what is their major distinguishing features

Answer 37

Fibrous joints: bones held together by dense irregular CT rich in collagen. no synovial cavity. Cartilaginous joints: bones held together by cartilage, no s cavity. Synovial joints: bones forming joint have synovial cavity and united by dense irregular CT of articular capsule + acessory ligaments.

Question 38

What is the definition of a joint and what is its aka. What are the 3 primary functions of a joint

Answer 38

Joint is any point where two or more bones interconnect. aka articulation. 3 functions: Movement Force transmission Allowing spaces for growth

Question 39

What are the 3 functional classifications of a joint and their definitions

Answer 39

Synarthrosis : immovable (wanting to fuse) Amphiarthrosis : slightly movable Diarthrosis: freely movable

Question 40

Compare the stability, movement and therefore common location of the 3 functional classification of joints

Answer 40

Synarthrosis has high stability and very little movement. Amphiarthrosis has a little less stability and a little more movement. However both are limited by the tissue types holding them together. and are prob closer to Axial skeleton. But not Diarthrosis has a low stability and high movement: Appendicular skeleton

Question 41

What are the 4 defining features of synovial joints

Answer 41

Articular cartilage Articular capsule made of fibrous layer and synovial membrane containing bv and nerves Synovial Cavity Synovial fluid

Question 42

Explain simply how synovial joint structure means that its a diarthrosis

Answer 42

They are not restricted by the properties of the specific tissue which hold the bones together. Actually the ends of the articulating bones are mostly free apart from its attachment to the articular capsule, permitting wide mobility

Question 43

What is the type of CT and 4 functions of articular cartilage and what does its degradation cause

Answer 43

A specialised type of hyaline cartilage, forming thin layer on top of bone. Function: 1. protect ends of bones 2. absorb microshock 3. support heavy loads for long periods 4. provide smooth frictionless surface.

Question 44

What makes up the cell component of articular cartilage and what is its function and location

Answer 44

Chondrocytes: live in lacunae and can occur by themselves or groups depending on zone Function: build, repair and maintain cartilage

Question 45

What makes up the fibre component of articular cartilage and what is its function and location

Answer 45

Type 2 collagen which is thinner and supple. It has specific patterns in different zones. Function: Provides structural integrity by linking surface zone to osteochondral junction.

Question 46

What makes up the ground substance component of articular cartilage and what is its function and location

Answer 46

Water and soluble ions Function: hydrate transport nutrients and wastes + Glycosaminoglycans + Proteoglycans. Function: Hydrophillic so provides swelling and hydrating mechanism for the proper function of cartilage

Question 47

What are the solid component and fluid component of articular cartilage and what is the dry weight/ wet weights

Answer 47

Fluid (can move in and out) water and soluble ions (Ca2+, Na+, K+): 75% WW Solid (fixed inside): GAGs, PG: 25% DW Collagen: 75% DW

Question 48

What is the PG content, arrangement of fibres and appearance of chondrocytes in Surface zone

Answer 48

There is low PG content, only to lubricate The dense arrangement of fine fibres is parallel to the surface to resist shear forces. The chondrocytes are small and flattened in their lacunae.

Question 49

What is the PG content, arrangement of fibres and appearance of chondrocytes in middle zone

Answer 49

PG content is increasing Fibres are thicker and less densely packed. Orientated at 45 degrees to the surface Chrondrocytes are fatter and have a round lacunae

Question 50

What is the PG content, arrangement of fibres and appearance of chondrocytes in deep zone

Answer 50

Has highest PG content Collagen fibres are orientated perpendicular to the surface Chondrocytes are stuck in vertical columns called nests because they are mitotically dividing. They secrete ECM between them to ‘move up’ to the surface

Question 51

What is the PG content, arrangement of fibres at the tide mark and what two functional zones does it separate

Answer 51

PG content has been replaced by hydroxyapatite (calcified) so low PG Fibres continue straight perpendicular Separates deformable + functional from calcified

Question 52

What is the PG content, arrangement of fibres and appearance of chondrocytes in calcified cartilage

Answer 52

Low PG content, high in hydroxyapatite from chondrocyte Fibres continue straight perpendicular chondrocytes in calcified lacunae

Question 53

What is the PG content, arrangement of fibres at the Osteochondral junction and what two functional zones does it separate

Answer 53

PG content high as it is cement line and PG= glue 2. The fibres are attached to convoluted osteochondral junction perpendicular to surface.

Question 54

How is delamination (cracking into layers) of bone prevented by the structure of articular cartilage

Answer 54

Having a layer of calcified cartilage provides a transitory area that provides more SA for the shear forces on cartilage to be distributed rather than just on the osteochondral junction.

Question 55

Does cartilage contain BV, nerves and lymphatics? How are chondrocytes nourished

Answer 55

No. Chondrocytes are nourished by diffusion only .

Question 56

Describe the structure of a PG complex

Answer 56

These are PGs attached to a long hyaluronic acid chain. (GAG) and these attach to collagen fibres

Question 57

Describe the structure of a PG and give eg

Answer 57

Many GAGs (sans hyaluronic acid) attached to a protein core. They stand out from each other because of the repulsion from their negative charges. eg. Aggrecan

Question 58

Describe the structure of a GAG and give eg

Answer 58

Repeating disaccharide (2 sugars) unit (carrying a negative charge). Eg. Chondroitin sulphate and keratin sulphate

Question 59

Describe the 6 steps of loading cycle of articular cartilage from recently unloaded cartilage

Answer 59

Ion conc in the matrix increases because negative charges on disaccharide units attract positive ions into the cartilage from the joint space Osmotic gradient is created by moving of ions causing water to move into the matrix and the cartilage to swell. The cartilage swells until the swelling force = the tension force placed on collagen. At this point : unloaded equilibrium and the volume of cartilage doesn’t change When a load is introduced the fluid component is squeezed out of the cartilage back to the joint space synovial fluid or other parts of uncompressed cartilage. The volume of the cartilage decreases because the loss of fluid = creep. Eventually the compressive load will be supported by solid component and the repulsion of negative charges and will stop shrinking= loaded equilibrium.

Question 60

What are the main purposes of the loading cycle of articular cartilage

Answer 60

allow nutrients and O2 to enter with the fluid phase and then waste products + CO2 to be removed when the load is placed on it To self lubricate the surfaces of the joint with the fluid phase

Question 61

What is structure and function of the joint capsule

Answer 61

Comprised of fibrous outer layer and inner synovial membrane, perforated by nerves and bv and may be reinforced by ligaments. Function: 1. Connection between two bones. - is loose to allow movement at the joint but 2. Protection: becomes tight at the extreme limits of range of motion

Question 62

What is the CT, structure, and function of the Fibrous layer of articular capsule

Answer 62

CT: irregular+ regular dense CT Structure: parallel, interlacing bundles of white collagen fibres that are continuous with periosteum of bone. transitory bv but richly innervated. Function: -resist tensional forces and check abnormal joint movement. -support and protect the synovial membrane + whole joint

Question 63

What is the CT, structure, and function of the synovial membrane layer of articular capsule

Answer 63

CT: loose CT of variable thickness Structure: 2 layers. Can form villi which increase SA and reduce volume of synovial cavity. Lines all non articular surfaces inside the joint cavity up to the edge of articular cartilage. Synovial subintima: highly vascularised, containing macrophages, fat cells and fibroblasts. F: maintains and protect articular capsule during normal movement, reduces volume of joint cavity to cushion Synovial intima: 1-3 cells thick, contains synoviocytes that F: secrete lubricating features of synovial fluid

Question 64

What is the structure and function of Joint cavity

Answer 64

Small area between articulating surfaces with peripheral margins filled with villi (in foldings of the synovial membrane). F contains small amount of synovial fluid

Question 65

What is the make up and function of synovial fluid

Answer 65

Made of 1. ultrafiltrate of blood plasma from bv in the subintima + 2. secretions of lubricating proteins eg. Hyaluronic acid from synoviocytes . 3. free cells: monocytes, lymphocytes, macrophages and synoviocytes Function: joint lubrication, shock absorption, chondrocyte metabolism and overall joint maintenance

Question 66

List the functions of muscle

Answer 66

Movement : movement of bones, transport of gut content, lymph transport (smooth), circulating blood (cardiac) Stability : stabilising joints with wide range of movement through active contraction (instead of ligaments articular capsule). + maintaining posture Communication: facial expression, body language, writing, speech Control of body openings and passages: sphincters in pupil, mouth (entry) + urethral, anal (smooth + skeletal) for exit Heat production: produces 85% of body heat which maintains body at 37 degrees for normal function

Question 67

Compare the terms Origin, Insertion, Osteotendinous junction, Myotendinous junction, tendon and muscle belly to describe the general anatomy of skeletal muscle

Answer 67

The muscle belly is the organ which attaches to the bone by tendons. The attachment that moves the least during muscle contraction is the origin (us.axial) whereas the attachment that moves the most during muscle contraction is the insertion (us. append) On the two sides of the tendon are osteotendinous junction to the bone and myotendinous junction to the muscle. OTJ is much stronger (sharpeys fibres) than MTJ.

Question 68

List the order of layers of skeletal muscle from Epimysium to myofibril

Answer 68

Epimysium, perimysium, fascicle, endomysium, myocyte, sarcolemma, sarcoplasm, myofibril

Question 69

Describe the features of a myocyte - what makes it up

Answer 69

Multinucleated, has a sarcolemma that conducts AP well for uniform contraction. It has a sarcoplasm containing lipids, glycogen and myoglobin (O2 store) and many myofibrils

Question 70

Describe the structure of a myofibril

Answer 70

They are made of contracting units called sarcomeres. which are divided by Z discs

Question 71

Describe the structure of a sarcomere

Answer 71

Dark A band in the middle and Light I bands on the outside. Z discs separate the I bands into half.

Question 72

Describe the structure of Fascicle

Answer 72

A bundle of myocytes surrounded by endomysium: Loose irregular CT. With a basement membrane in between the sarcolemma and endomysium (secreted by both). This contains lots or nerves and capillaries that supply the myocytes

Question 73

Describe the structure of muscle (organ)

Answer 73

A bundle of fascicles that are surrounded by perimysium (dense irregular). Then layer of epimysium that surrounds the perimysium, getting coarser and stronger as you get to the outside border of muscle.

Question 74

Compare the CT of skeletal muscle and how are they arranged in muscle in to out

Answer 74

endo: loose irregular peri + epi: dense irregular Arranged in to out : endo, peri, epi but all blended together.

Question 75

Where is the deep fascia found

Answer 75

It underlies the skin and subcutaneous tissue called superficial fascia. It covers the epimysium of muscle but allows it to glide underneath, - around bones it can blend with the periosteum or -can be part of muscle tendon as an attachment for muscle.

Question 76

Function of deep fascia

Answer 76

Often, it separates muscles with similar action or supplied with same nerves / bv into compartments by making these walls of deep fascia.

Question 77

What is investing fascia

Answer 77

Deep fascia that are deeper walls or septa- a continuation of the lining that goes between muscles (intermuscular septa) or bones (interosseous membrane). Where investing fascia comes into contact with bone it fuses with the periosteum.

Question 78

Compare hyperplasia vs hypertrophy.

Answer 78

# of cells. This is due to increases in size of individual myocytes by increasing number of myofibrils. Hyperplasia: when tissue/organ increases in size due to an increase of cell number. (skeletal muscle can’t) Hypertrophy: increase in size due to increase in cell size but not number of cells. This is due to increases in size of individual myocytes by increasing number of myofibrils.

Question 79

What stimulates hypertrophy

Answer 79

Heavy resistance training - use to maximum fatigue and use of anabolic steroids.

Question 80

How do anabolic steroids increase size of muscle

Answer 80

Anabolic steroids are variants of testosterone that overstimulate skeletal muscle and bone to increase protein synthesis. But it has other side effects like 2nd puberty.

Question 81

What is atrophy and what causes it. compared to hypoplasia

Answer 81

When muscles decrease in size due to the reduction of myofibrils in the myocyte. Caused by muscles not being stimulated by motor neurons. ie paralysed, sedentary due to other disease. reversable Whereas hypoplasia is a reduction in the number of myocytes as a result of dying when no more myofibrils. hard to reverse.

Question 82

What are satellite cells (myoblasts) location, function.

Answer 82

Found outside sarcolemma but under basement membrane. They are the only cells that can divide and fuse with each other and the myocytes to repair limited damage/ replace myocytes as they are created in embryonic stage so limited amount.

Question 83

Why can’t skeletal muscle undergo hyperplasia

Answer 83

Myocytes are created by fusion of many myoblasts during embyronic stage of life and can’t divide mitotically because they have lots of nuclei and are big cells.

Question 84

What are 4 functions of skeletal muscle connective tissue

Answer 84

To provide organisation and scaffolding upon which the muscle is constructed To provide a medium for bv and nerves to gain access to myocytes To prevent excessive stretching and therefore damage to myocytes To distribute the forces generated by muscle fibre contraction.

Question 85

How do Z lines move during sarcomere contraction

Answer 85

they move closer together as i band is shortening

Question 86

How does myofibril cut in vivo still exert a pulling force on muscle tendons

Answer 86

The Z lines of adjacent myocytes are held together by structural proteins called desmins. This allows contractile force from sarcomere either side of the cut to be transmitted to neighbouring. sarcomeres.

Question 87

How does an entire myocyte cut in vivo still exert a pulling force on muscle tendons

Answer 87

The Z lines of outermost sarcomere is bound to the sarcolemma, basement membrane and endomysium by the Protein complex containing dystrophin. This allows the contracting forces either side of the cut to be transmitted to the surrounding endomysium–>myotendinous junction