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Health Sciences
Health Sciences 2300A/B
Jamie Melling

HS 2300BAnatomy Lecture 5:Articulations February 26th, 2014 Functional Classification 1. Synarthroses – immovable (i.e., sutures between the bones of the cranium) 2. Amphiarthroses – slightly movable (i.e., joint between the ribs and sternum – the costal cartilage that creates a joint – there is movement – everytime we take a deep breath, the ribs move up to enhance the space in which our lungs can uptake oxygen from the atmosphere – this is moving with respect to one another – guided and regulated) 3. Diarthroses – freely movable (i.e., should, knees, and hips) • Typically see synarthrostic and amphiarthrotic joints in the axial skeleton • Diarthrotic are seen in the appendicular skeleton Structural Classification • Fibrous Joints  “Tight”, no joint cavity, no hyaline  Little to no movement – dense connective tissue  Sutures, sydesmoses, gomphoses  Skull, interossesus membranes, teeth  Creates a very strong bond between the two bones  Fibrous materials joining two bones together  Dense with collagen fibres – strong  You have fibres inside of the sutures that keep the bones inside the cranium together  Sydesmoses – have ligaments that join two bones together (dense regular)  Interosseus Membranes – concentrated bone, and regular; banded ligament – keeps the fibia and tibia together  Gomphosis – a type of joint in which you have a pocket in which a bone sits into attached by a ligament – exists in the teeth or the mouth – i.e., pocket on the mandible is where the tooth fits into; what holds that tooth in place is the paradontical ligament  Anwhere you have something holding two bones together is a fibrous joint  A ligament is a fibrous material • Cartilaginous Joints  Still no joint cavity, might have hyaline  Articulation bones are united with cartilage  Not very moveable  Synchondroses, symphyses  With Hyaline, without hyaline  Synchondroses – the main cell line in hyaline cartilage is a chondrocyte; it is made up of cartilaginous material – there is hyaline cartilage – i.e., knobby knee that is on the growth plate (epiphyseal plate) – until these portions of the bones are united after we have stopped growing, there are actually two separate portions of the bone – the head is separate from the shaft because you have a joint; hyaline cartilage connecting these – i.e., joint between the ribs and the sternum; costochondral joint – joins the ribs and the sternum  Symphyses – i.e. pubic symphyses; in addition to cartilage, they have fibrous material as well – they are in a disc (menisci) that we have at the pubic symphyses – i.e., intervertebral cartilage in the middle • Synovial Joints  Have it all… Joint cavity, hyaline, movement  Most joints in the body are synovial joints  Material that surrounds the articulating points of the joint – the bones that meet those surfaces, you can’t actually see those bones articulating with another because there is a capsule around them – called a joint capsule – creates a cabining inside, where the bones are articulating with one another – contained within a joint cavity  Looking at the tibia and femur – if you were to move away the muscles, you wouldn’t be able to see the femoral condyles or the tibial plateau unless you move the capsule that surrounds the knee joint  The cavity is crucial to synovial joints because it creates a closed space in which we can have fluid – called synovial fluid – the fluid’s primary function is to act as a lubricant so that the bones can glide nicely across each other  If you can see a cavity, you can identify it as a synovial joint  If you can actually see the ends of the joint it is either a cartilaginous joint or a fibrous joint – no capsule or articulation of the bones  We also describe the joints are in the presence of hyaline cartilage - fibrous joint; the hyaline cartilage isn’t connecting the bones together, you either have ligaments holding it together  A cartilaginous joint has cartilage joining bones together – there is always a presence of hyaline – but it may not be the actual tissue that is joining the bones together  It either has hyaline cartilage joining the bones together, or it has a disc – that would be a symphyses type of joint  Disc has cartilage – on the outside it has fibrous material, hyaline in the middle  You are always going to have cartilage – if you can’t see the cartilage, you can identify it as a fibrous joint  Caution: hyaline may not be responsible for joining the bones together, by being in a disc, it may be the fibrous material around the disc that may be articulating the joints together  Most of the joints in the body are synovial joint – with this type of joint you have a capsule and synovial joint so that you can reduce the amount of friction – you don’t want arthritis and the fluid prevents this Synovial Joints • Articular Cartilage (What Kind?)  Discs or menisci may be present • Articular Capsule  Outer Fibrous Capsule (irregular dense) and inner synovial membrane  We use this sporadic nature of the fibers – identify it to dissociate that it away from ligaments that support the joint  Ligament vs. Capsule?  Ligaments – you can see the organized patter of collagen fibers within it – very parallel  Capsule – the fibers are disorganized – dense irregular connective tissue  A ligament is responsible for withstanding separating forces from particular direction – one ligament will be responsible for holding the bones together, when forces are applied from a certain direction to pull them apart – at another direction (i.e., extension vs. flexion), you have another ligament responsible for withstanding those separation forces  The capsule has to withstand forces from all directions – that's why we have a sporadic organization of the fibres – dense irregular tissue  Lubricating and nourishing agent • Synovial Fluid  Egg white type fluid  Nourishes/lubes articular surfaces  Lubricating agent that sits inside the agent, so that when the fibula and tibia press against one another, it lubricates the joint to reduce friction  The articular capsule that you cut open, if you peel is back, you can see it is glossy (different from the outside) – the reason is because it is membrane stuck to the membrane of the capsule – this membrane is called the synovial membrane (green tinge)  The synovial membrane is made up of epithelial tissue – epithelial cells make up epithelial tissue – works as a diffusion barrier  Epithelial tissue is avascular – vessels don’t penetrate into the joint cavity where the bones are articulating to one another  This fluid is a filtrate of the blood  Synovial membrane is the inner lining of the capsule – works as a diffusion barrier – the vessels outside of the capsule releases some of the nutrients from the plasma in the blood and cross the synovial membrane – the membrane really regulates what moves through the joint capsule – what filtrate is resulted is synovial fluid  Not only does it act as a lubricating agent, it acts as a nourishing agent (hyaline cartilage is inside the joint cavity and it needs to be nourished – and it is nourished by the synovial fluid that contains the nutrients from the blood)  Filters the plasma, and what is left as a filtrate, it is a fluid that is lubricating because it has a protein called a glycoprotein that enhances the lubricant properties of the fluid • Joint Cavity (aka Synovial Cavity)  Unique potential space holding fluid  Inside the joint cavity you have ligaments – in the case of the knee, inside the knee you have the ACL (ligament that is often torn – needs nourishment as well, but doesn’t get any because the blood doesn’t enter into the joint cavity – the ligaments need to rely on the synovial fluid for nourishment)  These ligaments inside the joint cavity are called intracapsular ligaments – inside the cavity and therefore inside the capsule  If the ligament is outside the capsule, it is called extracapsular ligaments  Both ligaments work to support the joint but have different roles  Getting back to the synovial fluid, you will hear weeping lubrication when discussing synovial fluid – this means that it describes it’s two roles – when you sit, there isn’t a lot of pressure on the articulation between the femur and tibia because the joint is open – at this time the fluid that exists inside the knee cavity created by the capsule is soaked into the hyaline cartilage (similar to sponge taking in water) and is also soaked into the intracapsular ligament in the knee joint – it is soaked in there because it is nourishing these tissues – you’re at rest and there isn’t much need for lubrication for that joint because there isn’t movement – it performing the role of nourishment  If you move quickly, you will have pressure across the joint – the femur is sitting on top of the tibial plateau and there is pressure and a need for lubrication and the bones are going to be rubbing across each other – when you squeeze the sponge, the fluid leaves the sponge, and when you stand up the pressure between the tibia and femur, the fluid leaks out of the hyaline cartilage and the ligaments and then it acts as a lubricant  This is what they mean by weeping lubrication – depending on the status or positioning of the joint  Synovial allows to perform both roles efficiently – nourishment or lubrication • Reinforcing Ligamentum  Intra or extracapsular • Nerves and Vessels  Feedback about stretch allow proprioception  Vessels in synovial membrane allow fluid production – weeping lubrication  Nerves penetrate to the level of the synovial membrane – they only get passed the epithelial tissue because inside the capsule there is no need for nerves  They also perform an essential function in terms of balance – proprioception – the CNS’awareness of the joints in the body – if you’re standing on one leg, you’re CNS are aware of the body’s position – where the joints are located at any time – constantly sending information back so that if you become unbalanced, the brain can send messages to make sure you don’t tip over – this is effective to keep us from injuring the joint  The CNS recognizes the stretching on one side of the joint and sends motor messages to the joints susceptible, contracts them, and prevents injury – part of the proprioceptive feedback  Trick Ankle (an ankle you always go over) – this is because you injure the joint at one point and you destroy the proprioceptive fibers that send information back to the brain to allow you to compensate to tell you when it is susceptible • Articulating disc that may or may not exist in a synovial joint – they are not always present – in many times where you have lots of force across a synovial joint, you will have a disc in there – not all joints face this type of force or pressure, so they don’t need the disc – the disc is also called the menisci (similar to the menisci in the knee) – menisci present in the joint cavity (inside the lining of the capsule) • You have a disc in the sternoclavicular joint – only articulating point between the upper limb of the appendicular skeleton and the axial skeleton – any force transmitted across the upper limb to get to the axial skeleton as we fall and catch ourselves with our arm is going to be met at the sternoclavicular joint, so it makes sense that there is a disc in this region Bursae and Tendon Sheaths • Not part of synovial joint proper but a common and friendly neighbor! • Bursa where layers of bone, muscle, skin or tendons may rub together • Tendon sheath bursa with a tendon through it “Pigs in a Blanket” • Bursas are usually confused with the capsule around a joint • Bursa – a little pocket filled with fluid that is similar to synovial fluid, but is just a little sac • The membrane lining the sac (similar to synovial membrane that filters the plasma and creates a viscous lubricating agent inside the sac) – there are not bones or joints articulating inside the sac • Wherever there is friction not just with bones, but also with tissue where there is movement across that is the potential for friction • I.e., skin moving on the back of elbow when flexing or extending – the skin will rub across the bone – you have bursas just underneath the skin to reduce the friction of the skin rubbing against the elbow • I.e., under the skin where the knee cap (patella) is, there is a bursa to reduce the potential of friction there • There are 15 bursas supporting the new joint – reducing the friction across the joint (whether across the skin, or muscles that are across the knee joint that are constantly moving and as a result causes friction across muscles or other bones) • When rupturing a bursa, the fluid that is inside it will leak out and an inflammatory response is likely to occur and inside the bursa will be inflamed (bursitis) – anywhere you have a bursa and quite painful • The patella is quite smooth – this is the bursa (fluid-filled sac) – if there is no longer a bursa there, the surface becomes rough • Tendon Sheath – a bursa that wraps itself around a tendon; muscles are constantly flexing, tendons are constantly pulling at bones – because there is constant movement across the tendons, there is a need for the tendon sheath to protect against friction that results from this – we have many tendon sheaths • A bursa by itself is a sac that is all over the body to reduce friction, but when you have a tendon sheath, it is the same structure but just around a tendon • “Pigs in a Blanket” ** (weiner is a tendon, pastry around it is the bursa) • Synovial Joint – you see a capsule, and you know it’s not a bursa • Bursas rely on having fluid inside them • In a human, if you were to perform an operation on a knee, you will see these sacs are much different than the capsule around a joint – the main feature that you look for is the orientation of the fibres – you will see a dense irregular network of collagen fibres – whereas a bursa is just a membrane that is glossy in its appearance Synovial Joint Examples • 6 different types of synovial joints based on the movements • Plane Joint • Hinge Joint  Seen at the elbow  Trochlear notch of the ulna and how it fits into the humerus  The movement across this joint is somewhat limited – you can only flex and extend  The Ulna is only involved in flexion and extension – this is because the interaction between these bones – a tight fit (little wiggle room for other than flexion and extension)  This joint is also known as a unidirectional/uniaxial joint – only moves in one direction – hinge joint  What guides this controlled movement is how the bones articulate with each other  You typically have a cylindrical bone that fits into a troph-like end to a bone (like the trochlear notch on the ulna) – how they interact with one another is you have one direction to move in a hinge-like motion that is unidirectional • Pivot Joint  Ulna and Radius  The head of the radius is articulating into the radial notch on the ulna  You have a cylindrical end to a bone that fits into a troph-like notch of the bone that allows for one particular movement  This is a unidirectional/uniaxial joint that moves in one direction – pivot joint  The head of the radius is going to pivot within the radial notch on the ulna  More of a ring structure – the cylindrical structure fits into the ring  You complete the ring with a ligament that is called the annular ligament  I.e., Interaction between the C2 and C1 – the dens of the axis (C2) penetrates up into the vertebral foramen of the atlas (C1) – the cylindrical structure is the dens that represents this type of shape and the ring structure is the vertebral foramen, so C1 pivots on top of C2 – C1 doesn’t move side to side or back and front, it only twists • Hinge and pivot only moved in only one direction – unidirectional/uniaxial • Condyloid Joint and Saddle Joint are both bidirectional/biaxial – able to move in two directions • Think about the x-y-z axis – if you are unidirectional, you are only moving along one of those axis, if you are bidirectional, you are moving along two of the axis • Condyloid Joint  You have a oval end to a bone fitting into an oval depression on a bone  Very common in the body  I.e., Metacarpal and phalanx – the distal end of the metacarpal is very round, whereas the proximal end of the proximal phalanx has an oval depression and fits nicely into the distal end of the metacarpal – you can move side to side, and up and down (two directions)  Bidirectional • Saddle Joint  Commonly seen between the capals and the metacarpals as well as the tarsals and the metatarsals  You have two saddle ends to a bone and they fit nicely with one with one another  They can move side to side, and up and down (bidirectional) • Ball-and-Socket Joint  Very similar to the condylar joint where you have a round end fitting into a round depression  But in a condylar joint you have an oval end to the bone and in a ball- and-socket you have a rounded end  It is
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