MSK Flashcards
List some functions of the skeletal system (besides the classic movement, protection, support)
minear storage and release, fat storage, haemopoiesis
Where is the proximal epiphysis located?
highest point of the bone (head of bone)
Where is the metaphysis located?
between the diaphysis and epiphysis
Where is the distal epiphysis ?
lowest part of the bone (foot of bone)
True/False; Trabecular bone is predominantly found in the diaphysis region.
False, Compact bone is predominantly found in the diaphysis region.
What is the periosteum?
outer fibro-cellular sheath surrounding bone.
prefix “peri” means “around”. Thus peri + osteum = around the bone.
What is the function of articulate cartilage?
The cartilage covers the articulating surfaces of the bones with a smooth, slippery surface which reduces friction between bones in the joint during movement and helps to absorb shock and support heavy loads. it protects the ends of bones
Where is spongy bone found?
core of the epiphysis
What is the benefit of having spongy bone in our long bones?
keeps the bones light in weight
proximal Spongy bone in the epiphysis is likely to contain what type of bone marrow?
red - closer to the axial skeleton
the medullary cavity and spongy bone in the distal epiphyseal region is likely to contain what bone marrow?
yellow - further away from axial skeleton
What is the the precursor of an osteogenic progenitor cell?
unspecialised stem cell (mesenchyme embryonic CT)
What is the function of the osteoprogenitor cell?
supplying developing bone with bone forming cells
Where can osteoprogenitor cells be found?
surface of bone in periosteum and central canals
What is the precursor to an osteoblast?
osteogenic cell
What is the function of osteoblasts?
deposition of new bone, secrete osteoid and calcify osteoid
Where can osteoblasts be found?
where new bone is being formed, usually in a layer under the peri or endosteum (active)
What are the precursors to osteocytes?
osteoblasts
What is the function of osteocytes?
bone tissue maintanence
Where can osteocytes be found?
trapped within lacunae - can communicate with neighboring cells through their long cellular processes inside canaliculi
What is the precursor of osteoclasts?
fusion of monocyte (white blood cell) progenitor cells - fuse = syncytium
how do osteoclasts remodel bone?
secreted acid and enzymes - dissolves the mineral and organic component of bone
Where can osteocalsts be found?
where bone remodelling/resorption is taking place
What is the main structure which attaches the periosteum to the bone?
- The periosteum is attached to the underlying bone by perforating fibers or Sharpey’s fibers
- thick bundles of collagen that extend from the periosteum into the bone extracellular matrix.
What is the name given to the areas between osteons?
interstitial lamellae
What is the name given to the layer on the outside of osteons of the bone?
outer circumferential lamellae
what is special about the structure of collagen in lamellar bone?
Orientation of the collagen fibres within the bone tissue alternates - creates strength
What does the endosteum surround?
- located on the inside of the concentric oesteon rings
- blood vessels and nerves
Where can the cellular processes of osteocytes be found?
canaliculi
What is the structural/functional unit of spongy bone?
trabecula
What is the function of spongy bone
support stress from multiple directions
Where is the location of blood supply from spongy bone?
in sapaces between trabecula
Where is the predominant location of spongy bone ?
epiphysis
What is the structural/functional unit of compact bone
osteon
where is the predominant location of compact bone ?
diaphysis
What is the location of blood supply of compact bone?
haversian canal, volkmanns canal
During the formation of new osteons, ____ are undergoing a process called bone ____ . These cells are formed by the fusion of many ____ cells. Cells that form this way are called a ____.
osteoclasts, resorption, monocyte progenitor, syncytium
The area in the center of the osteon is called a ____ and contains blood vessels and ____
Haversian canal, nerves
What is the outermost layer of the osteon called?
Cement line
What is interstitial lamella
lamella located between osteons that do not belong to osteons
During new osteon formation, osteogenic cells are depositing an initial layer called ____ , which consists mostly of ____ and is missing or has low levels of ____ which is found in mature bone.
osteoid, collagen, hydroxyapetite
movable or not
Synarthrosis is a ____ joint
immovable
Amphiarthrosis is a ____ joint
slightly movable
Diarthrosis is a ____ joint
freely movable
Give an example of synarthrosis joints
structures in the skull in adults
Give an example of amphiarthrosis joints
structures in the skull in children, pubic symphysis, intervertebral joints
Give an example of diarthrosis joints
knees, shoulders, hips, digits, jaw
Label the following on a joint:
- articulating bone
- synocial membrane
- fibrous layer
- articular cartilage
- synovial cavity
What are the two layers that make up the synovial membrane?
Thin intima and subintima
In-foldings of the synovial membrane are called?
Vili
The synovial cavity contains what primarily?
Synovial fluid
Thicker sections of the fibrous capsule are called?
Capsular ligaments
On the ____ protein, we find many ____ which together make up a ____. Many of these can bond to ____
corse, glycosaminoglycans, proteoglaycan, hyaluronic acid
What are the stages of the “loading unloading” cycle?
- Recently unloaded cartilage - removal of load allows positive ions and water to move into cartilage. -ve charges attract ions from the joint space - increases ion concentration in matrix (osmotic gradient. -water in) this causes cartilage to swell with the influx of water
- Unloaded equilibrium - as cartilage swells the collagen is placed under increasing tension - swelling force = tensional force. Swelling cancelled by tension. wants to swell but collagen wont let it
- Introduction of load - load squeezes fluid component out of cartilage into joint space. ions, water. andwaste exits
- Loaded equilibrium - loss of fluid reduces volume of cartilage = creep. pushes -ve charges together. eventually compressive load force = electrostatic repulsive forces. cartilage stops shrinking
List 4 functions of muscle, 5 of bones and 1 they share
muscles: heat production, stability, control of body openings and passages, communication
bone: support, protection, fat storage, haematopoeisis, calcium and phosphorus reserves
both: movement
List the order of the layers of what a surgeon would see if he cut from the skin down to the sarcomere level
- skin
- superficial fascia
- deep fascia
- epimysium (covers muscle)
- perimysium (covers fasicle)
- endomysium (covers myocyte)
- sarcolemma
- sarcoplasm
- myofibirl
- sarcomere (I band, A band, Z discs)
What does the epimysium cover?
muscle
What does the perimysium cover?
fasicle
What does the endomysium cover?
myocyte
What other structures besides mitochondria are found in teh sarcoplasm?
- myoglobin - binds to oxygen, O2 storage
- glycogen - broken down to glucose for use in cellular respiration
How many nuclei does a skeletal muscle fibre contain
hundred or more
how are muscle cells formed during embryonic development?
- fusion of small mesodermal cells called myoblasts.
- under the micrscope the nucleus and Satellite cells are often mistaken for each other since they occur in a similar location.
Label the following on the cross section of the lower leg:
- muscle, intermuscular septa, interosseus membrane, deep fascia, muscle compartment, subcutaneous tissue
collectively the intermuscular septa and interosseus memrane are known as?
the investing fascia
True/False
Hypertrophy is when muscle size increases due to increase in the number of myocytes.
False - Hypertrophy results in an increase in muscle size, however this is due to increase in the size of individual myocytes. This occurs due to an increase in the number of myofibrils in each myocyte.
True/False
Hyperplasia is when the number of cells in an organ increases. This is the main process by which skeletal muscles grow throughout life.
False - Hyperplasia does describe tissue/organ growth through an increase in cell number. However, the predominant method used for skeletal muscle growth is hypertrophy.
True/False
Satellite cells are created by the fusion of myoblasts. They help repair damaged myocytes.
False - myocytes are formed by the fusion of myoblasts! Satellite cells are the myoblasts that didn’t fuse - but once they divide, their daughter cells will fuse with the damaged myocyte as part of repair process. It would be more accurate to say that Satellite cells are myoblasts. They help repair damaged myocytes.
Treu/False
Atrophy can be thought of as the opposite process to hypertrophy. It describes a reduction in the number of myofibrils in myocytes.
True
True/False
Hypertrophy can be stimulated by many factors, including resistance training and the use of catabolic steroids.
False - Resistance training and anabolic steroids can stimulate muscle hypertrophy. Catabolic steroids (ie corticosteroids) can cause muscle atrophy.
What are the two definitions of bone?
bone the organ - organs are made up of different tissues
bone the tissue - one of the tissues found the bones the skeleton
What is haemopoiesis?
manufacturing of RBC
Where is fat stored in the bone?
yellow bone marrow
How many are there in axial skeleton via appendicular?
80, 126 (paired)
How does the bone deal with compression?
structure of the trabecula softens load by distributing load in different directions
Trabecula is covered in?
endosteum
When bones are in contact with one another, there is no periosteum, instead we have ?
articular cartilage
What constitutes and alive tissue?
blood vessels present
What is the endosteum?
thin, inner fibro-cellular layer lining medullary cavity
What is in the medullary cavity?
bone marrow
WHat are perforating or sharpeys fibres?
matrix of connective tissue consisting of bundles of strong collagenous fibres connecting periosteum to bone
What is periosteum?
outer fibro-cellular sheath surroundign the bone
What CT can be found in the ECM of bone?
- fibres (organic): collagen
- ground substance (inorganic): Hydroxyapetite
What is the function of collagen fibres in the bone?
resist tension (stretching/pulling)
What is the function of hydroxapetite in the bone?
resist compression (squeezing/crushing)
What is an osteoid?
- unmineralized bone tissue
- the organic extracellular matrix (mainly collagen) of bone, synthesized by osteoblasts prior to mineral deposition
What is the composition of osteoid?
70% collagen, remainder is proteoglycans other proteins and water
What eventually happens to the osteoid precursor matrix?
eventually filtrated with hydroxapetite (bone salts) - calcification
makes the bone strong and dense
hydroxyapetite replaces water
What are the two mechanisms in bone remodelling?
appositional growth and bone resorption
What is appositional growth?
bone growing in width not height
adding new bone onto an existing surface
describe what happens during appositional growth
- osteogenic cells divide forming osteoblasts which deposit osteoid
- some osteoblasts become trapped in lacunae, eventually becoming osteocytes
- when growth stops, osteoblasts can covert back into osteogenic cells or die. Osteoid is fully calcified
- now only osteogenic cells are present - resting state
What constitutes active bone?
as soon as osteobalsts appear
Explain what happens during bone resorption
- monocyte precursor cells leave blood vessle and start to fuse on bone surface
- osteoclasts form and start dissolving bone
- osteoclasts eventually die (apoptosis), resorption stops
- blood vessles grow into new spacew - removing dissolved shit
- resting endosteum
How do long bones grow in lenght?
endochondral ossification - using cartilage to grow bone, replacing cartilage
What are the two types of bone?
- woven/immature
- mature/lamellar
What is the difference in collagen between immature and mature bone?
immature - randomly arranged
mature - organised to resist tension
Why as osteobalsts depost new bone do they put collagen down in sheets alternating 90°?
enables bone to withstand forces from different directions, making it significantly stronger
What are the two types of lamerllar (mature) bone?
spongy and compact bone
how is bone remoddled in spongy bone?
appositional growth on trabecula depnding onf forces on the bone
Label the diagram of spongy bone
osteocyte (in lacunae), lamellae, endosteum, osteoclast, blood vessel, canaliculi
Why is spongy bone always no thicker than 0.4 mm
because osteocyte always in 0.2 mm of a blood vessel
Why do we need canaliculi?
the ECM of bone is poor in H2O, hard for nutrients and O2 to get to the tissue - canaliculi deliver these to osteocytes more centrally
Label a diagram of compact bone
medullary cavity, circuferential lamellae, interstitial lamellae, osteon, blood vessels and nerves, concentric lamellae in osteon, central or haversian canal, perforating or volkmanns canal, periosteal vessels, periosteum
How are primary osteons formed?
formed around an existing blood vessle on the surface of bone (normally in the periosteum)
Explain the process of forming a primary osteon
- osteoblasts in the active perisoteum either side of a blood vessel put down new bone forming ridges
- as the bone continues to grow, these ridges come together and fuse forming a tunnel around the blood vessle. the tunnel is now lined with endosteum
- the osteoblasts in the endosteum build concentric lamellae onto the walls of the tunnel. the tunnel is slowly filled inward toward the centre forming a new osteon
- the bone continues to grow outwards as the osteoblasts in the periosteum build new circumferential lamellae. osteon formation repeats as new periosteal ridges fold over another blood vessel
Explain the process of forming a secondary osteon
- osteoclasts form and gather in an area that needs to be remodelled.
- Bore their way through existing bone - “cutting cone” creating tunnel inside bone
- osteoblasts move in and line tunnel wall
- osteoblasts form new active endosteum and start depositing osteoid onto the walls of the tunnel
- osteoid layer calcified forming new lamella
- blood vessel will grow into the newly formed tunnel to supply the cells
- osteoblasts depost layer upon layer of new concentric lamellaw onto the walls of he tunnel slowly filling it in
- area behind the cutting cone is called the closing cone
- some osteoblasts get trapped in the newly formed lamellae becomes osteocytes
- tunnel reduced to size of haversian canal - remaining osteoblasts die or become osteogenic cells
Where are secondary osteons created?
inside existing bone
What is the cement line?
line at the junction between the outermost lamella of the new osteon and the preexisting older bone
What is the difference in unit formation between spongy and compact bone?
spongy - grows outwards
compact - grows inwards
Besides supporting forces from multiple direction, spongy bone is also repsonsible for?
rapid trunover of Ca and P
cancellous and cortical bone are terms for?
spongy and compact bone
What is a joint?
any point at which two or more bones interconnect
What are the three functions of joints?
- movement
- force transmission
- growth
From the axial to appendicular skeleton, list the types of joints in order of proximity
synarthrosis - amphiarthrosis - dairthrosis
What are the most common joints found in the body?
simple synovial joints - diarthrosis
What are the 4 common features to all synovial joints?
- articular cartilage
- articular capsule
- joint cavity
- synovial fluid
What type of cartilage is articular cartilage?
specialised hyaline cartilage (CT)
What is the main function of hyaline cartilage?
protect the ends of bones
What are the cells of the articular cartilage?
chondrocytes
5%
What is the function of chondrocytes?
- build, repair and maintain cartilage
- live in spaces of lacunae
- they can occur in groups called nests (cells undergoing mitossi)
Explain the composition of the extracellular matrix of cartilage (95%)
Ground subsatnce
- water and soluble ion s(75% WW)
- Glycosaminoglycans
- proteoglycans
Fibres
-collagen (mainly type II)
What is the function of water in the ECM of cartilage?
the fluid compartment that can move in and out of the tissue
What is the function of glycosaminoglycans and proteoglycans in the ECM of cartilage?
- provides the swelling and hydrating mechanism for the proper function of cartilage
- part of the solid compartment that is fixed inside teh tissue
What is the function of collagen in the ECM of cartilage?
- provides the structural integrity to the tissue
- specific zonation patterns
- also part of the solid compartment that is fixed inside the tissue
How are chondrocytes nourished?
diffusion only - no blood vessles, nerves or lymphatics
What are the three layers of cartilage?
- surafce zone - low PG
- middle zone - PG content increases as you go down
- depp zone - highest PG content
What is the orientation of collagen in the three layers of cartilage?
- surface: fine collagen firbes parallel to surface
- Middle zone: thicker random fibres (strength)
- deep: fibres perpendicular to surface
Why are the collagen fibres in the surface zone parallel?
resist the shear, tensile, and compressive forces
What is the orientation of chondrocytes in the deep layer of cartilage?
nests of chondrocytes in stacks - rejuvinatethe layer by secreting ECM between them
List the layers of cartilage to bone
- surface zone
- middle zone
- depp zone
- tide mark
- calcified cartilage
- osteochondral junction
- subchondral bone
What is the tide mark?
junction between functional and calcified cartilage
What is calcified catilage?
- thin interlayer of hard tissue, between the hyaline articular cartilage and the subchondral bone
- stress resistant to shearing forces
What is the composition of calcified cartilage?
- low in proteoglycans, high in hydorxyapetite
What is a glycosaminoglycan?
repeating disaccharide unit
What is a proteoglycan?
many glycosaminoglycans attached toa core protein
Explain how proteoglycans work
-ve charges from GAGS (chondroitin and keratin sulphate) repel eachoter
- molecular spring: compress cartilage- bounce back
What is the function of the articular capsule?
forms a sleeve around joint
not to tightly hold bones toggether - suitably loose to permit joint function properly
What are ligaments
dense regular connective tissue connecting bone. to bone
can be found at articular capsule
What is the fibrous layer of the articular capsule?
outer layer of dense connective tissue both regular and irregular
What is the fibrous layer of the articular capsule made of?
parallel but interlacing bundles of white collagen continuous with periosteum of the bone
What are capsular ligaments responsible for?
resist tensional forces
designed to check excessive and abnormal joint movement
Is the fibrous layer vasuclar/nerve supply?
poorly vasuclarised, richly innervated
What is the synovial membrane of the articular capsule?
inner layer of loose connective tissue of variable thickness
What does the synovial membrane line?
all non-articular surfaces inside joint cavity
What can the synocial membrane be divided into?
subintima and intima
What is the intima?
1-3 cells thin
synoviocytes secrete components found in synovial fluid
What is the subintima?
between fibrous layer and intima
highly vascular, macrophages, fat cells, fibroblasts
What is synovial fluid?
yellowish fluid, ultrafiltrate of blood plasma
(HA secretd. by synoviocytes)
FUNCTION OF SYNOVIAL FLUID?
lubrication, shock absorption, chondrocyte metabolism, joint manintenance
What do muscles stabalise?
joints and psoture
What is the origin of muscle?
attachment that moves the least during muscle contraction
What is the insertion of muscle?
attachment that moves the most during muscle contraction
What. isa tendon?
links muscle to bone
What is the osteotendinous junction?
between bone and tendon
blends with periosteum
very strong
What is the myotendionus junction?
weaker
between muslce and tendon
What is the epimysium?
dense irregular connective tissue surrounding the perimysium and entire muscle
What. is the perimysium?
dense irregular connectie tissue surrounding the fasicles (continous with epi and endo)
What is the endomysium?
loose irregular connective tissue surrounding myocytes
contains enrves and blodo vessels that supply myocytes
What does the basement membrane between the endomysium and myocyte consit of?
secretions from fibroblasts in endomysium + myocyte secretions
What is a myocyte/myofibre?
muslce fibre - contains many myofibrils
How variable is myocyte size?
x10 fold 10um to 100um
What is deep fascia?
dense connective tissue (regular and irregular)
Where is the dep fascia found?
underlies skin and subcutaneous layer
Muscles that are supplied by the same nerves or have simular functions can sometimes be found geouped in a ____. Of which the outer layer is made up of ____
muscle compartment, deep fascia
What are the deeper walls of the dascia reffered to as?
investing fascia (eg. intermuscular septa, interosseous membranes)
Can muscle move under the deep fascia?
- most areas epimysium can move. andglide udner deep fascia
- other areas deep fascia part of muscle tendon and can act as attachment point
What is hyperplasia
when an organ or tissue undergoes increases in size due to increase inc ell number. skeletel doesnt usually do this
What is hypertrophy?
increase in muscle size due to increase in size of myofibirls as a result of increased myofifbril size NOT NUMBER
What causes hypertrophy?
heavy resistance training, anabolic steroids
What are anabolic steroids?
- variants of testosterone
- increase protein synthesis through interaction with skeletal m and bone
- side effects of intercation with other tissues - coronary artery disiease, mood swings - roid rage, liver failire, shrivelled testes, infertilitry
What is muscle atrophy?
decrease in size due to reduction of myofibrils in the myocytes
When does muscle atrophy occur?
when muscles arent used or stimulated by motor neruons
What. ishypoplasia?
loss of myocyte cell intelf
Wher are satelitte cells found?
lie beside the muscle fibres, outside the sarcolemma but within the same basement membrane
