Lecture 5 - Skeletal System

Added: 2026-05-15

[00:00:00]hi everyone welcome back uh this week we're going to be focusing on the skeletal system believe it or not this is our last week of new content before the midterm exam this week's focus is going to be on mainly providing you with an overview to the skeletal system looking at all the bones which are the organs that make up that organ system and then looking at how all of those bones articulate with one another to form all the various joints throughout the body now our skeletal system is divided into two main regions and we looked at those really briefly in week one and those are the axial region and the appendicular region in this diagram here you can see the axial skeleton is highlighted in blue right so that includes our skull both cranial and facial bones our spine also known as our vertebral column which runs all the way from your first cervical vertebrae all the way down to your sacrum and then the chest which is known as our thoracic cage which is composed of your 12 pairs of ribs as well as the sternum which they articulate with anteriorly and lastly but not least the highway bone is a small bone that has a lot of muscular attachments that's sort of just in front of your vertebrae and just behind the mandible now i want you to think of the axial skeleton as making up your main primary axis of the body all right when we look at the appendicular skeleton next you're going to see that then the appendicular forms all the attachments to the axial skeleton all right and the axial skeleton is made out of 80 bones in total now the appendicular division are all of these structures that you can see attaching to that axial skeleton so we have the upper extremities which start here the pectoral girdle from the clavicle anteriorly and then the scapula posteriorly all right scapula is your shoulder blade clavicle is your collar bone both of those then connect directly to your upper extremity right from your humerus down to your forearm bones your radius and your ulna then you have the carpal bones the metacarpals that form the palm of your hand and your phalanges that make up your fingers moving down then we have the lower extremities which are connected to the sacrum which is the base of your vertebral column there the base of the axial skeleton and the pelvic girdle is made up of the pelvic bone which attaches directly to the sacrum and then connects to the lower extremity through the femur which connects directly to the tibia and fibula which distributes all of its force down through the seven tarsal bones five metatarsals and your phalanges which are your toes alright so the key thing to understand at this point right now we have the two main divisions the axial which is highlighted in blue made up of the skull thoracic cage and vertebral column and then the appendicular skeleton are the attachments right so your upper extremity and your lower extremity and the bones that connect them to the axial skeleton you've seen some numbers these numbers are important we have 80 bones that make up the axial skeleton and 126 bones that make up the appendicular skeleton that gives us a grand total of 206 bones that we are going to learn about today so first off we are going to start with the axial skeleton starting at the top looking at the skull now the skull is made up of both cranial bones that make up your cranium as well as facial bones that make up your face we have the frontal bone which is located right at your forehead the sides you have the parietal bones you have the temporal bones posteriorly you have the occipital bone and then two other bones that are deeper in structure the sphenoid bone which you can see portion of it here and then the ethmoid you're seeing a very small portion but we'll take a different look by opening up the skull through a cross section and looking down in to see those bones in a little bit now each of these cranial bones that i just mentioned they form your cranium which is the structure that houses and protects your brain now learning these different names right now is going to come in really useful later on when you're going to be learning about the different lobes of the cerebral cortex each lobo cerebral cortex is named according to the bone that it's protected by now each of these cranial bones which are defined as flat bones remember we talked about the different shapes last week the flat bones are all connected by these joints that are removable and they are known as sutures now connecting the frontal bone to the parietal bone we have what's known as the coronal suture right now coronal this is running in a plane that we've already talked about the plane that cuts the face off right that was that frontal plane well the frontal plane also goes by the name the coronal plane so the suture that connects the frontal bone to the parietal bone is the coronal suture now looking laterally we have the squamous suture which is connecting the parietal bone to the temporal bone and posteriorly we have the lambdoidal suture which is connecting the parietal bone to the occipital bone so you're noticing a theme so far these main sutures that we're talking about here they're all connecting different cranial bones to the parietal bone now we have one other suture which is we can't really visualize from either a lateral or an anatomical perspective because it runs right across the top through the midline anterior to posterior a suture that runs right through that mid sagittal plane which is easy to remember because it's known as the sagittal suture all right so you have the lambdoidal suture which connects the occipital bone to the parietal you have the squamous suture that connects the temporal bone to the parietal bone you have the coronal suture connecting the frontal bone to the parietal bone and then the sagittal suture which runs right along the top of the skull connecting the left and right parietal bones now as we talked about last week there are two different processes by which bones ossify right by which the embryological structures and then fetal structures ultimately become ossified covering the brain throughout development we have membranes right and then those membranes start developing ossification centers within them which is why this process is known as intramembranous ossification now this process continues and these flat bones that surround our brain that form the cranium they continue to grow but once the fetus is born there are still regions where those bones have not fully ossified and those regions are known as fontanelles and those are those soft spots we have four main different soft spots you have one that's a sphenoid fontanelle a mastoid fontanelle an anterior fontanelle and a posterior fontanelle the one that's most useful in being able to identify whether or not an infant is dehydrated is the anterior fontanelle because it tends to be the most prominent and if the child's dehydrated you can actually start to see a sunken sort of depression start to create there where that opening exists all right now these fontanelles remember intramembranous ossification is going to be occurring through those first two years but typically by about the time that that child reaches two years those fontanelles will close up and those sutures will be complete now a couple of other cranial bones that are important for us to cover are the sphenoid as well as the ethmoid the sphenoid as you can see here from the superior perspective kind of reminds me of the bat symbol the sphenoid is known as the keystone of the cranium and that's because it essentially forms the floor between all of the structures of the external face such as your eyes your nose mouth and separates all of those structures that are connected to the external environment from the cranium now the sphenoid is one of four bones that contain sinuses in them so if you have ever had a sinus infection first places you're going to feel that is over top of the eyebrows and as well in front and the cheeks but you also have sinuses in the sphenoid and if the sphenoid sinuses become infected that's typically when the infection just feels like it's deep seeded kind of right between the eyes now there are a number of different foramina now foramina or foramen is an opening or a hole in a bone and the reason that we have these openings or holes is to allow for blood vessels or nerves to be able to pass through we have two main foramina in the sphenoid that allow for the passage of two very key cranial nerves first one i'm going to mention here is the optic nerve now the optic nerve passes through and innervates our eye and is responsible for our ability to be able to see and the mandibular nerve is a branch of the trigeminal which is responsible for the sensation that you experience on your face now moving a little bit more anteriorly in the cranial cavity we're looking at the ethmoid bone right now the ethmoid bone located in the anterior portion here of the cranial floor between either orbit so here we're looking at the frontal bone behind it posteriorly you have the sphenoid now something that's unique about the ethmoid is that it has a number of openings in the surface and those openings are so that the olfactory nerve which is cranial nerve one is able to extend different nerve fibers from that olfactory nerve are able to pass through and enter in to your nasal cavity here's the ethmoid as we've seen it and there's your sphenoid posterior and here you're just seeing the lateral aspect there of your sphenoid as well as the lateral aspects there of the ethmoid now as i mentioned previously the sphenoid and ethmoid both contain sinuses now the ethmoid contains a number of sinuses that are also known as air cells because there's a number of them located in the bone the sphenoid sinus and ethmoid are both located centrally between the eyes this is typically that pressure that you feel deep within the skull and centrally located now most common sinus infections are going to affect the most superficial of the sinuses first and that's why we tend to when we have any kind of sinus cold is that you start to feel the tension just above the eyebrows and then you also will tend to feel it there at either side of your nasal cavity there in the maxillary bone all right so those two bones the maxillary bone which forms your anterior cheek and the frontal bone which forms your forehead and they both contain pairs of sinuses in them now these paranasal sinuses are there and lined with mucous membranes to help to warm and also moisten the air that you're breathing in i'm sure we've all been outside at some time in the winter and we've tried to just breathe in directly through our mouth well that is going to send that air straight down into your lungs and typically that's very uncomfortable all right when we breathe in through the nose we're able to then have that air pass into those sinuses where there's increased surface area where the air is able to be moistened and worn before it then passes through into our lower respiratory tract they also help to produce the sound of our voice because they act as resonating and one other advantage is that they make the skull lighter remember all of our bones are made with thin layers of compact bone on the perimeter and then spongy bone on the inside and the reason that our bones are not made up entirely of compact bone remember is so that they are not as heavy as they would be otherwise so we also have these paranasal sinuses that are contributing in a number of positive ways but are also helping to lighten our skull and reduce the actual load that our head and neck muscles have to exert to be able to keep our head upright now basal skull fractures result typically from severe head trauma so here you're looking you know some a severe car accident or falling from a very high height two of the key identifying features would be raccoon eyes in addition to nasal discharge more particularly what we're looking for is if the sphenoid or ethmoid have been fractured in any way remember they're forming that barrier between your cranial cavity and the external environment if either there was a fracture in the ethmoid bone or the sphenoid bone that could allow for cerebral spinal fluid that bathes our brain and protects our brain to be able to leak out into the sinuses which ultimately drain into the nasal cavity and so this is where you could have an individual that might not necessarily have bloody nasal discharge but may have sort of a straw colored type of appearance okay and that would be an indication that typically either the sphenoid or ethmoid have been fractured and so there's been a breach between the external environment and the internal cranial environment now moving down from the skull the skull sits directly on top of our first cervical vertebrae then following down we have our cervical region which forms our neck the thoracic region that forms our ribcage and then the lumbar region forming our lower back and the lowest lumbar vertebrae sits directly on top of a bone known as the sacrum which is that connection between the pelvic bone and the vertebral column and extending from the sacrum we have our tailbone known as the coccyx now the vertebral column is functioning to be able to protect the spinal cord as it courses all the way down through each of these vertebrae it also acts to support the head because we have the head sitting directly on top of that first cervical vertebrae known as the atlas and then throughout the thoracic spine we have attachments on either side for each of our ribs all right so we have 12 thoracic vertebrae we have a pair of ribs for each level therefore we have 24 ribs in total and we'll talk about the different numbers of true false ribs as we progress through the lecture we also have attachment points for the muscles of the back the erectors that allow us to stand upright and also then as i mentioned attachments for that pelvic girdle there at the sacrum now as i mentioned here forming our neck we have our cervical vertebrae on the cervical region we have seven c1 through c7 then moving down we have the thoracic vertebrae that form the thoracic spine here we have t1 through t12 then inferior to t12 we have the lumbar vertebrae so l1 through l5 so we have seven cervical vertebrae 12 thoracic and five lumbar and the way i'm going to get you to remember this breakfast lunch and dinner it's breakfast at seven lunch at 12 dinner at five all right so that helps you remember the number of bones in each of these regions here so you have seven cervical vertebrae 12 thoracic vertebrae and five lumbar vertebrae now here as i mentioned we have a bone known as the sacrum so this forms the base of the vertebral column now the sacrum is one bone in a skeletally mature individual so once we've passed puberty and we've stopped growing we have reached skeletal maturity and at that point your sacrum is completely fused into one bone now in children however the sacrum is made up of five separate sacral vertebrae and similarly with the coccyx the coccyx is our tailbone caustics is one fused bone in a skeletally mature adult however in children can be anywhere from three to four bones so you can see here there's actually a variation in number anywhere from 33 34 vertebrae in children to 26 vertebrae in adults now these vertebrae are very different from one another in their regions you'll see cervical vertebrae have key identifying features same with thoracic and lumbar as well but there are elements to the anatomy of the vertebrae that are similar throughout although they may be shaped differently they all for the most part have these key landmark features so looking here this is a lumbar vertebrae your lumbar vertebrae are the big chunky ones they're the ones that are at the base of the spine and are having to withstand all of the mechanical forces that are going to be transmitted down the length of that vertebral column all the vertebrae for the exception of c1 they all contain a vertebral body okay and that marks the anterior portion of the vertebrae so here we're looking at a lateral view of the lumbar vertebrae this is the posterior aspect and this would be your anterior aspect now extending from the vertebral body posteriorly we have the vertebral arch between the vertebral arch and the vertebral body we have this opening here known as the vertebral foramen tutorial we're going to then take a look at how when you stack up all these vertebrae one on top of the other all of those vertebral foramen line up and we end up with what's known as the vertebral canal one big long bony passageway through which the spinal cord can pass through now remember foramen means an opening so the vertebral foramen is an opening that's formed between the boundary of the vertebral arch and the vertebral body now when you stack these vertebrae on top of each other you can see the superior part of this next foramen they create what's known as the intervertebral foramen right so if we were to stack another vertebrae underneath this vertebrae here would be a lateral opening the intervertebral foramen are openings between that's what inter means all right so between the vertebrae we have these openings and these are key to allow for the passage of your spinal nerve roots and they are the nerve roots that are ultimately going to extend as the peripheral nerves that go off to innervate all the structures in your body and then generally speaking we have a number of processes so a process is essentially a projection of bone so here you can see we have the spinous process projecting posteriorly you can see this here as well all right the spinous processes those are those bumps if you just take your hand to the back of your neck and go down to rate where you sort of go from your neck into your back you should be able to feel some of those prominent bumps there so those are those spinous processes extending laterally from the vertebrae we have what are known as transverse processes and then you can see here the superior articular process see that there and then you also have inferior articular processes as you can see here articulation you're probably thinking okay we must have a bone articulating with another bone and so these articular processes are how each of the vertebrae are then connected with one another each vertebrae above and below is going to articulate with the superior articular process for the one above and the inferior articular process is going to connect with the vertebrae below now we're going to take a look at some key identifying features here within our cervical vertebrae c1 and c2 your first two cervical vertebrae they're unique they have a completely different shape they have some unique structures associated with them and so we're going to look at those individually but then c3 down through c7 they tend to all look the same now as i mentioned previously the atlas is your first cervical vertebrae this is where your skull is going to articulate with the vertebral column so the skull is literally sitting right on top of the c1 the occipital bone that we saw previously at the posterior aspect of the cranium it has prominent structures known as occipital condyles at the base of it and they are the structures that are going to be sitting here on your atlas all right now as i mentioned before the atlas is the exception to the rule so the atlas does not have a vertebral body there is no true spinous process they have what's known as a posterior and anterior tubercle and the upper surface contains those superior articular facets that are going to articulate with the occipital bone above and between the occiput and the c1 vertebrae and between the occiput and your atlas you're going to have the ability to be able to flex the upper cervical spine so allowing you to nod yes now contrast that with the axis which is your c2 vertebrae the axis now has a vertebral body it has a spinous process and something unique about the cervical vertebrae from c2 down is that they contain what's known as a bifid spinous process which means that there are two projections that come off the posterior aspect of it now you can see here another unique structure that's projecting superiorly off of that vertebral body is a structure known as the dens and this is a tooth shaped process that projects up through the vertebral foramen of the atlas all right so your dense projects superiorly and your atlas is going to sit here and articulate with those facets so the dens is going to project up superiorly through that vertebral foramen and then between c1 and c2 this is going to allow us to shake your head no so rotation so when you think occiput in c1 it's also known as coc1 i want you to think flexion nodding yes and then between c1 and c2 i want you to think rotation right so shaking your head no so then moving down to the thoracic spine we have thoracic vertebrae t1 through t12 now besides being larger and much stronger than the cervical vertebrae they have additional landmark features known as facets which are flat joint surfaces that are there for articulating with the ribs all right so there are two articulating facets one on the vertebral body and one here on the transverse process so for each rib you're going to have two joints that are going to be produced by the articulation of the rib with that thoracic vertebrae and remember this is the same for both sides now these ribs remember are going to then continue anteriorly where they then connect with the sternum and here at the sternum this is where the ribs are going to then connect by costocartilage directly to the sternum anteriorly and that is going to limit the amount of motion that we can exhibit within the thoracic spine so moving inferiorly we're now entering into the lumbar region of our vertebral column where we look at those lumbar vertebrae and remember i mentioned that they are the largest and they're the strongest of the unfused vertebrae right between your cervical thoracic and lumbar the lumbar ones are the ones that are going to look chunky because they have to be able to withstand all of the stresses and forces that are being transmitted down the entire length of the vertebral column and so the projections tend to be a lot thicker and shorter to be able to allow for the large muscles of the back to be able to have very strong attachments and then from your five lumbar vertebrae we then have the last l5 sitting directly on top of the sacrum specifically a portion known as the sacral promontory and here in anatomical position but also from a posterior perspective you can see these openings which actually mark the separation between the original unfused sacral vertebrae and those are known as the sacral foramina as i mentioned before remember any opening is there to allow blood vessels and nerves to be able to pass through the cotta equina that passes through the sacral canal is going to pass then out through the individual sacral foramina and then ultimately connect together to form the different nerves that pass into your lower extremity now between each of the vertebral bodies we have these fibrocartilaginous discs fibrocartilage is the strongest cartilage that we have in the body you find it primarily in the intervertebral discs as well as in the pubic symphysis which we're going to look at in the lower appendicular skeleton now between each of the vertebral bodies you have an intervertebral disc and i want you to picture this intervertebral disc sort of like a jelly donut so the outer portion is made out of a very strong fibrous cartilage but in the inside you have a structure known as the nucleus pulposa it's a very fluid like tissue now these intervertebral discs act as shock absorbers for the spine and they're extremely effective in being able to withstand forces like compressive forces where they don't do as good of a job though is on more shear type of forces those would be forces that would be shearing the disc laterally and what can happen if say an individual was in a forward flex position and there was just enough of that shear stress in addition to compression there on the disc that can force that nucleus pulposa to then project posteriorly and in some cases either cause a bulge to the disc or can actually break through the fibrous cartilage and enter into the spinal canal causing lots of irritation and pain and when it does that's known as an intervertebral disc herniation so you may have heard of this as a slipped disc there's different layman's terms that are used to describe this condition so you can either have bulging of the disc which can still put pressure on the spinal cord and the associated spinal nerve roots or a complete herniation and nervous tissue does not like to have any kind of foreign body or substance in around it right because it becomes irritated and when it does it sends pain signals through the body now i'm sure you may have noticed already but if you were to take a look at the vertebral column from a lateral perspective you'd notice there are a number of s-shaped curves that occur throughout and this is to help with distributing forces throughout the vertebral column all right you'll notice here that the cervical curvature as well as the lumbar curvature are the same and the thoracic curvature and the sacral curvature are both the same now when we all start off when we are first born we're all born with a c-shaped curvature if you're looking to the anterior that is known as a kyphosis and you can see remnants of that initial c-shaped kyphosis in the thoracic spine as well as in the sacrum and then as an infant develops they are going to be developing these secondary curvatures known as lordosis all right so you have a cervical lordosis and a lumbar lordosis a thoracic kyphosis and a sacral kyphosis the way this works is that when we're first born we have that c-shaped curvature to the spine that's the primary curve the kyphosis and then as we start to crawl well we'll be lifting our heads up and as we do that we start to develop this lordic curve in the cervical region and then what's next well from crawling then we start standing right and as soon as we start standing we start to develop this lumbar curvature as well so the cervical and lumbar lordosis is known as a secondary curve whereas the thoracic kyphosis and the sacral kyphosis are both remnants of that primary curvature now you can have accentuations of either a lordosis or a kyphosis so two examples here are accentuations of those where it would be a hyper lower doses such as sway back that you can see in pregnant women as they're trying to arch their back to redistribute their center of mass hyperkyphosis would be someone with more of a hunchback so sort of a stooped posture where you would see an accentuation of this curve now comparing that to a lateral deviation of the spine lateral deviation of the spine is known as a scoliosis there are different reasons that a scoliosis may develop if an individual is not yet reached skeletal maturity they will be monitored on an ongoing basis to ensure that the curvature that exists does not surpass a certain level typically it's about 35 degrees that they would be looking for if the patient was young enough and still had a lot of growing to do and had a severe enough curve they may then qualify for surgery such as putting in rods to try to stabilize the spine now you can have a structural scoliosis due to you know a malformation or an anatomical anomaly of one of your vertebrae or you can have a functional scoliosis you know say there's a leg length and a quality that causes you know the one hip in this case here you know it would be more that your right hip would be sitting slightly lower and you would have a bit of a tilt in your pelvis causing this and the rest of it compensates right that would be for more of a functional that could be dealt with just simply with equaling out those leg lengths so now we're moving on to the thoracic region where we're going to take a look at the thoracic cage okay that makes up the primary protective structures of that region now the thorax is made up of your 12 rib pairs remember you have 12 thoracic vertebrae and to each vertebrae you have a pair of ribs so 12 pairs of ribs your 12 thoracic vertebrae which they each attach to posteriorly and then the sternum which they attach to anteriorly now you'll notice that we have a number of them that are attaching directly to that sternum and ribs one through seven are known as true ribs for that reason the true rib is a rib that is going to attach directly to the sternum by its own costo cartilage all right so we see as we walk our way down seven is still attached directly to the sternum as we move down into eight 9 and 10 you can see that each of these are all going to insert into a common cartilage which is then shared with seven right so because 8 9 and 10 do not connect directly to the sternum they are considered false ribs now if we move down further 11 and 12 they don't connect at all they are known as floating ribs the floating ribs are also a type of false rib because they do not connect to the sternum all right so if you were to separate your thorax into true versus false ribs you have pairs one down through seven would be true ribs and then pairs eight nine ten eleven and 12 would all be false ribs because they do not attach directly to the sternum now watch out for the way in which a question may be asked because if you're asked how many true ribs do you have well here we're looking at pairs right so if you're to look at how many in total you have 14 in total right seven on each side how many false ribs do you have well five on each side so you have 10 in total how many floating ribs do you have two on each side so you have four in total all right so look out for that the difference in language there between how many ribs or how many pairs of ribs now one thing you've probably noticed is that the sternum is not one single bone in fact it's made up of three separate portions we have this most superior portion which is the heart shaped portion known as the manubrium and you can see here the manubrium attaches directly to your clavicle which we'll talk about later is the only bony connection to the appendicular skeleton in the upper extremity and also connects to ribs one and two and then if we move down more inferiorly we have the sternal body and then inferiorly to the sternal body the xiphoid process so if you're trying to palpate this on yourself the manubrium would be sort of rate at the base of your neck anteriorly where you feel that divot between your collarbones okay that's the beginning of the manubrium down slightly and then you're into the body right now if you come to the terminal portion there of the vertebral body the xiphoid process is kind of tucked in a little bit so you almost feel like you're right within that hollow area here formed by the costal cartilage don't push too hard because it can be uncomfortable but the xiphoid process extends inferiorly from the sternum at that point so we have covered the axial skeleton giving you a bit of an overview there looking at the different portions of both the skull the vertebral column as well as the thoracic h now we're going to move on to the appendicular skeleton and remember the appendicular skeleton are the parts that attach to that axial division so think the axial is the main axis of the body right and then appendicular is everything that attaches to it and that includes not just your extremities but the bones that form the girdles that attach to the axial skeleton directly so we're going to take a look here at the clavicle and scapula as well as your upper extremities and then we're going to move to looking at the pelvic bone as well as the lower extremity so the upper region of the appendicular skeleton starts here at the pectoral girdle we have the clavicle which is your collar bone anteriorly and it attaches if you follow your collarbone walk out laterally with your fingers you'll eventually feel a bump on the lateral portion of the clavicle and that's the articulation here with the scapula specifically this portion known as the acromion now the scapula is the bone that then articulates directly with the humerus the humerus forms your arm bone so attaching here at the distal portion of the humerus we have the radius laterally and how do we know we're lateral well because going to anatomical position the thumb is always lateral so associate the thumb with the radius all right and then the ulna running medially through the forearm down towards your fifth digit now connected directly to the radius and ulna we have our carpal bones and they form the bones of our wrist right you have eight carpal bones in total we won't be learning their individual names but just know you have two rows of four and they form your wrist right then extending distally from the carpal bones you have the metacarpals and the metacarpals are forming essentially the palm of your hand all right you can visualize them on the posterior aspect as well but just think about them as being the uh palm of your hand then extending out from the metacarpals we have the phalanges we have 14 in total okay so to look at this in a little bit more detail just to orient ourselves here is the lateral aspect right here's your radius here is your ulna and then we have our eight carpal bones okay so the eight carpal bones that are forming the wrist extending from those carpal bones we have our metacarpals now the way that you count your digits whether it be the metacarpals or the your actual fingers is that the thumb is number one right so give me a thumbs up thumbs number one so you start there laterally and then you move medially okay so one is thumb and two three four five which would be your pinky finger so those would be your five metacarpals and then extending from the metacarpals we have our fingers right and those are made up of our phalanges now you'll notice here in the second third fourth and fifth digits you have three phalanges three bones that make up your fingers the one closest to the trunk is known as the proximal phalanx or phalange uh middle phalange and distal phalange right phalanx is the singular moving over here to the first digit we only have two that make up the thumb so you have a proximal phalanx and a distal phalanx all right as we're going to see this anatomy here pretty much holds true in terms of numbers and connections once we move to the foot now we're going to be moving down into the lower region of the appendicular skeleton looking at the pelvic girdle which is formed by your pelvic bone so here you have one pelvic bone on the right and one here on the left right this slide is showing you the difference between the male pelvis as well as the female pelvis we'll talk about that in a second but for now what you need to understand is that the pelvic bones connect posteriorly to the sacrum which is the main attachment to the axial skeleton and then they connect anteriorly by each of the pubic bones at the pubic symphysis all right now the pubic symphysis is also made up of fibrocartilage remember that really strong cartilage that makes up your intervertebral discs well the pubic symphysis is also made up of that fibrocartilage now in an adult we have the one single pelvic bone but in an infant or a skeletally immature individual the pelvic bone is actually made up of three separate portions and those separate portions are the fan shape portion that you can see here known as the ilium you can see part of the ischium down here forming the ischial tuberosities and then here the pubic bone so those are the three separate bones that form the pelvic bone within a skeletally immature individual now within an adult they are all fused forming one single bone and here on the lateral aspects of the pelvis we have a structure known as the acetabulum the acetabulum is essential for the articulation between the pelvic bone and your femur to form your hip joint and the acetabulum is essential for articulation with the head of your femur which is your thigh bone to form your hip joint now if we take a look here at the male and the female pelvis it's probably a few things that you can identify already one of them and this is just typically speaking right not speaking to specific individuals generally speaking the size of the male skeleton is generally larger than the female skeleton but as i mentioned you have males with smaller stature and females with larger stature right so there are individual variations but the general trend tends to be that the male skeleton is generally larger now the shape of the pelvis the male pelvis is much deeper and a lot narrower whereas the female pelvis is a lot shallower and the brim is a lot wider the pelvic inlet as you can see here is also much narrower in the male whereas in the is much broader and all of these adaptations of the female pelvis are so that this opening here the pelvic inlet and outlet are as large as possible to allow for the accommodation of the fetus to be able to pass through during delivery and lastly part of this opening of the pelvis here in the female is that the pubic angle which is created by the two pubic bones here connected to the ischial tuberosities the pubic angle is much wider in the female than it is in the male and you can see here as well the pelvic outlet which we can measure between the coccyx and the pubic bone see much broader here within the female and the distance here would also be increased whereas in the male the distance between the caustics and the pubic bone would be a lot smaller now connecting directly with the pelvis at the acetabulum we have the femur which is your thigh bone connecting then from the femur you can see here directly transmitting that force through your shin bone which is the tibia all right and sitting over top of that knee joint you have the patella and the patella is a sesamoid bone known as a floating bone the patella is there to be able to transmit the stresses from the quadriceps tendon which inserts on the superior aspect to the patellar tendon that then inserts here on the tibial tuberosity so if you were to landmark this on yourself if you just go find your kneecap right now if you walk with your fingers to the inferior portion of the patella eventually you're going to feel like you kind of drop off the patella and now you're sort of into that shallow depression there that joint space if you continue to walk down you'll eventually hit a bump there just at the top of your tibia that's the tibial tuberosity so if you were to just relax your leg you probably won't feel much here but if you go and contract your quad which is your anterior thigh muscle try to extend your legs straighten it out further and you're going to feel that that patellar tendon is getting very tight because the quadriceps tendons pulling on it so that is the tibia and then laterally if you move to the lateral portion of your leg and move slightly distal you should be able to feel the bump on the outside part of your leg and that is the head of the fibula the fibula is your other lower leg bone so sort of similar to how our forearm is set up with the radius and the ulna and in this case here the fibula is running laterally both sides and the tibia runs medially all right so you take your hands all the way down you'll lose the fibula for a while as you go through your calf musculature and then continue you're going to start to feel the bony portion a little bit more as you get to the distal end here and that's where you're going to feel that outer ankle bump that's known as the lateral malleolus if you follow down from your tibia here so find your patella walk off the patella and walk down your front of your shin bone you should be able to feel the tibia running all the way down your leg and then you're going to feel it kind of move and course towards the medial aspect where you're going to end up on your medial malleolus so your inner ankle bump all right so those two bumps that you've always known about on the inside and outside of your ankles those are called malleoli right an individual is a malleolus so you have your medial malleolus which is part of your tibia and your lateral malleolus which is part of your fibula all right and then the tibia is going to form the true ankle joint here with the first tarsal bone so remember how you had the carpals in your wrist well here in the ankle and the hind foot we have what are known as tarsal bones the first one here that you can see the talus is going to be articulating directly with the inferior portion of the tibia forming that true ankle hinge joint all right the talus then sits on top of the calcaneus so if you grab your heel right now you're grabbing your calcaneus okay it is your heel bone and is the largest of the tarsal bones all right so the force is going to be transmitted from the tibia to the talus inferiorly through the calcaneus right now looking anteriorly we have five other tarsal bones all right you don't need to worry about their names but for completion's sake you have the navicular which is anterior to the talus and then anterior to the navicular you have the cuneiforms one two and three and then on the outer portion here on the lateral aspect you have the cuboid bone all right so that makes up your seven tarsals and then extending from the tarsals we have our metatarsals right so this is set up the same way that it was in the upper extremity where you had your carpals that form the wrist the metacarpals that extend and form the palm of your hand and then the phalanges formed your fingers well in this case the hind foot is formed by the tarsals the midfoot is formed by the metatarsals right this is right where your arch of your foot would be right through here and then extending from the distal portions of the metatarsals we have our phalanges all right and again start with one being your big toe on the medial aspect and then you count out laterally all right so in anatomical position we're actually going in the reverse direction in the foot we're starting from the medial aspect with the big toe and moving lateral whereas with in the upper extremity and anatomical position we start with the thumb which is lateral and count medial all right so the big toe is number one we have two phalanges there the distal and the proximal and then within the second third fourth and fifth toes we have the um three phalanges so the distal the middle and the proximal and we're going to finish off our lecture today looking at how all of these bones that we've just learned about articulate with one another now there are three types of joints classified by the specific degree of movement allowed by them and they are synarthrosis amphiarthrosis and diarthrosis all right so the way that you could refer this is as a synarthrotic joint or an amphiarthrotic joint or a diarthrotic joint now synarthrotic joints are ones that allow for no movement all right so right away what i want you to think of with center arthroses the sutures of the skull all right so those are examples of center arthroses that exist within the body okay so we have still articulations of the flat bones with one another but they are fibrous in nature and they allow for no movement so they would be classified as a synarthrosis now in amphiarthrosis amphi means both so a little bit of movement and amphiarthrotic joints are typically cartilaginous where you have two bones that are connected by cartilage between them you know two examples are the pubic symphysis that exists between the two pubic bones of the pelvis and the intervertebral disc joints so between each vertebral body you have those intervertebral discs so each of these connections where you have the disc that is connecting the two vertebral bodies the one above and the one below that's considered a cartilaginous amphiarthrotic joint and also the pubic symphysis which you can see identified here at the interior portion of the pelvis where you have the two pubic bones connected to one another now both the pubic symphysis as well as the intervertebral discs they are both made out of fibrocartilage which makes them extremely strong and durable and then lastly but the one that we're going to spend most of our time on for the rest of today are the diarthrotic joints now a diarthrotic joint can also be referred to as a synovial joint and that's because they all contain a synovial cavity that contains fluid that lubricates the joints and allows for free movement all right so comparatively with the center arthrosis synarthrotic joints which allow no movement and amphiarthrotic which allow for slight movement every joint in the body that is freely movable would be considered a diathrotic joint here this image is just outlining your center arthrotic joints the sutures of the skull this is showing you the fibrocartilage that makes the amphiarthrotic joint of the pubic symphysis now as i mentioned the diathrotic joints these are the ones that allow for free movement and this is where most joints that you think about are going to fall into you know any of your your interphalangeal joints your elbow your shoulder hip knee ankle all of those they are all considered diarthrotic now all the diathrotic joints all have a similar structure to them so we're going to discuss that briefly here so what i want you to do is to find your second digit all right so remember which is your first how do you find your first digit on your hand right your thumb is number one so then from your thumb in anatomical position you're going to count medially so your second digit would be your pointer finger all right now i want you to go and find the interphalangeal joint between the proximal and the middle phalange now move your finger around that joint that you're on that is this structure right here this is going to represent the proximal phalange and this will represent the distal phalange and this will represent the proximal phalange and this will represent your middle phalange all right so this would be your interphalangeal joint now each diathrotic joint contains the following structures we have number one articular cartilage at the articulating surfaces of both epiphyseal regions of the articulating bones and the articular cartilage here remember is made of hyaline cartilage and this is meant to provide that smooth lubricating surface to help to reduce friction when the joint is moving then continuous with the articular cartilage here and then wrapping around the entire internal aspect of the joint you can see it all throughout here we have a synovial membrane and that synovial membrane is essential because it is responsible for producing uh and secreting synovial fluid all right so this entire joint cavity that you can see here right this whole space is going to be full of synovial fluid and synovial fluid is essential for not only providing lubrication but also for being able to provide nutrients for the joint and then lastly we have the joint cavity in which all of that synovial fluid exists surrounding all of this you have a joint capsule that's responsible for providing reinforcement as well as stability to the joint now we have a number of different types of diathrotic joints and for most of these we have one example that we're going to go through to cover these so let's start off here with one of the easier ones so we have hinge joints one of the places that we find these are at the elbow but we can also find hinge joints at the knee as well as the true ankle joint formed between the tibia and the talus now hinge joints think about a door right a door just swings in that one plane open and closed so your hinge joints work very similarly to that next type of joint we're going to talk about are the pivot joints now with the pivot joints these are going to contain two structures so you have one bone that acts as the axis and then you'll have another bone that's going to be rotating around that axis that's what makes it a pivot joint so where we see rotation there's two structures we're going to look at first between the atlas and the axis remember up in the upper cervical spine c1 and c2 and then also between the head of the radius and the ulna we also have a pivot joint there so as you recall the atlas is your c1 and your axis is your c2 the axis has that vertical projection that passes superiorly through the vertebral foramen of c1 this allows for then the atlas to be able to rotate around the dens right so that's where between c1 and c2 this allows you to rotate your head right to shake your head no all right and finally then between the radius and the ulna you have a ligament that attaches from the ulna and wraps around the radius and so every time that you pronate and supinate your arm the radius is going to be rotating within that space and so both of those are considered pivot joints now the saddle joint we're gonna go to the hand take a look at the carpal metacarpal joint of the thumb now carpal metacarpal these joints are named based on the two bones that form the articulation so carpo so think carpal and then metacarpal of the thumb all right so we know our thumb is our first digit so let's find our first metacarpal and now let's look at where the carpal bone articulates with that metacarpal so that's the saddle joint that we're talking about where the trapezium articulates with the base of the first metacarpal that forms a saddle joint and it's named as such because the shape of the base of the first metacarpal actually is like a saddle that would sit on top of a horse we also have condyloid joints and one example is the atlanto-occipital joint that exists between our occiput and the atlas so as you may recall the occipital bone forming up the base of the skull the occipital bone has two projections from the posterior aspect of it those are known as occipital condyles and they sit right on top of your atlas and it's this joint between co which is your occiput and c1 that allows for you to nod your head yes we also have gliding joints which are also sometimes referred to as planar joints and these exist wherever you have flat articular surfaces that essentially glide against one another and one of the places we see this is all throughout the vertebral column here you can see that each vertebrae is going to articulate with a vertebrae above and a vertebrae below and so it's those articular processes that are going to be articulating with one another and form those gliding joints and i jumped over because last but not least we have our ball and socket joints and so the two that we've briefly looked at so far would be the shoulder joint formed between the head of the humerus and the glenoid cavity of the scapula and the hip joint formed by the femoral head which is the ball sitting in the socket of the pelvis which is the acetabulum okay so those are the six types of diathrotic joints that we find throughout the body and giving you just you know pretty much one example for each of them and we're going to wrap up today just taking a look at a couple of conditions that can affect the joints of the body comparing the difference between your degenerative types of arthritis and inflammatory joint disorders right so here we're looking at an individual with osteoarthritis now most of us at some point in our life are going to be experiencing some sort of degeneration of the joints of our body okay some of us more than others there are genetic components as well as just wear and tear on the body now osteoarthritis is due to the wear and tear the breakdown of the articular cartilage that you find in the synovial joints and one sign that is pretty typical with osteoarthritis is that you have these nodes known as bouchard's nodes at the proximal interphalangeal joints because osteoarthritis is degenerative it's normal as well to have you know certain joints that are affected and not necessarily see it systemically involved across both digits where you tend to see more systemic involvement is with your inflammatory types of arthritis now here we're looking at an image of an individual with rheumatoid arthritis so rheumatoid arthritis is a type of inflammatory arthritis it's a systemic autoimmune disease and results in chronic inflammation of the synovial membrane now typically with rheumatoid arthritis other tissues are involved as well now in this patient here what you're seeing here is a sign known as ulnar deviation right where there has been such inflammation to these metacarpal phalangeal joints that you're seeing this progressive deformity that's resulted from the inflammatory arthritis and it's referred to as ulnar deviation because all of the joints as you can see all the fingers are all deviating towards the ulnar side there two other types of inflammatory arthritis would be gaudy arthritis which results from inflammation caused by gout which is a condition where an individual has a buildup of uric acid crystals within their joints another type of arthritis known as infectious arthritis results from two different bacteria that can be passed on from tick bites one being associated with lyme disease and the other one associated with a different type of bacteria now lastly taking a look here at bone fractures we're just going to briefly go over some of the terminology any type of a break in the bone is defined as a fracture now you can have incomplete or partial fractures such as your hairline or a green stick fracture right essentially this would be a crack in the bone all right it hasn't necessarily cracked all the way through here you can see though an example of a complete fracture now with complete fractures you can have non-displacement or you can have displacement and the degree of displacement is going to determine whether or not you're likely to have an open fracture which is known as a compound fracture or a closed fracture which is known as a simple right so in both of these cases this is a complete break however here we have a significant degree of displacement which has then caused the fractured bone fragment to then pierce the skin which would make it a compound fracture right and in this case here we're looking at a simple but complete fracture over here you can see a few different examples of just the ways in which bones can break so you can have transverse straight across linear you can have green stick fractures which are more of an incomplete fracture that looks something like this they tend to occur in young children and then oblique which are also known as spiral fractures and typically these occur as a result of some sort of torsion or shear stress through the bone okay and that brings us through to the end of our lecture today also brings us through to the end of our new material before our midterm so this week in tutorial we're going to be spending a lot of our time looking at the 3d models to be able to go through the entire skeletal system and look at some of these joints up close to hopefully give you a better appreciation for them if you have questions please feel free to send me an email otherwise i look forward to seeing you all in tutorial take care