 Welcome to this session on osteology of the abdomen. In this session, we will be revising the lumbar vertebrae as well as the bony pelvis, okay? So, let us begin with the lumbar vertebrae. So, here we can see the five lumbar vertebrae as we had learnt in cervical vertebrae as well as thoracic vertebrae. There are some typical and atypical vertebrae. Similarly, in lumbar vertebrae also, the upper four lumbar vertebrae are typical lumbar vertebrae whereas the fifth lumbar vertebrae is the atypical lumbar vertebrae, okay? And when we speak about lumbar vertebrae, is there any cardinal feature for a lumbar vertebrae? Just recollect the cardinal features for thoracic vertebrae and cervical vertebrae. For cervical vertebrae, the cardinal feature was foramen transversarium, right? And for thoracic vertebrae, the cardinal feature was presence of costal facets, okay? So, is there any cardinal feature for lumbar vertebrae? The answer is no. Lumbar vertebrae does not have any cardinal feature. It is identified by exclusion. That means absence of foramen transversarium, absence of costal facets, that means it has to be lumbar vertebrae, okay? Now, let us cover the characteristic features of a typical lumbar vertebrae and then I will cover the atypical lumbar vertebrae as well. So, here we can see the typical lumbar vertebrae. The first lumbar vertebrae is seen clearly. So, in general, when we study the vertebrae, the vertebrae has got two parts. One is the body of the vertebrae and the remaining part is referred to as the vertebral arch. Okay? So, total components are included in the vertebral arch. This is the pedicle of the vertebrae, then the articular facet, superior inferior articular facet, then transverse process, okay? And this broad plate of the bone, the lamina, then the two lamina connect in the midline. This is the spinous process, okay? So, all these components are included in the vertebral arch, okay? And this opening which we can see behind the body of the vertebrae and in front of the lamina, this is the vertebral foramen, okay? And just above and below the pedicles, there are vertebral knots. This area is the superior vertebral knots and then this area is the inferior vertebral knots, okay? So, what all are the characteristic features here? In the body of the vertebrae, the shape is such that it is referred to as kidney shape or reny form shape and the anterior posterior diameter is less as compared to that of the transverse diameter. Then the spinous process is characteristic, it is quadrangular in shape, okay? Then the direction of the articular facets, superior articular facets are directed medially, inferior articular facets are directed laterally. Then there are few processes of the tubercles which are seen here. In the transverse process, there is a projection which is called as accessory process. Then the superior articular facet gives the projection along the posterior aspect that is referred to as the mammillary process, okay? So, these are characteristic features. I am telling this is the characteristic feature, not the cardinal feature. Why? Because these features will be also seen in the 12th thoracic vertebrae, okay? That is why we cannot say that this is the cardinal feature for lumbar vertebrae, okay? So, this was about the typical lumbar vertebrae. Let us see the atypical lumbar vertebrae that is the strip lumbar vertebrae. When we see the strip lumbar vertebrae, the body of the vertebrae is the largest as compared to that of the other lumbar vertebrae, okay? So, large, massive body of the vertebrae will be seen and when we see the posterior aspect, the superior articular facet is facing posteriorly whereas in a typical lumbar vertebrae, the articular facet was facing medially, okay? So, superior articular facet facing posteriorly, inferior articular facet facing anteriorly as compared to that of facing laterally in a typical lumbar vertebrae, okay? So, these were the main differentiating features from the typical lumbar vertebrae. When I said the largest massive body, another is the direction of this articular facet, okay? And also if we try to connect this articular facet, it will form an imaginary horizontal rectangle in this region, okay? Whereas in a typical lumbar vertebrae, if we trace here, the l1 vertebrae is forming a trapezium, then other vertebrae are forming vertical rectangle or square, but this strip lumbar vertebrae, if we connect the four articular facets, it is forming a horizontal rectangle, okay? This is important for differentiating the individual lumbar vertebrae. There is a rule which is called as faucet's rule which helps in differentiating the individual lumbar vertebrae, okay? Now let's cover the applied anatomy with respect to the lumbar vertebrae. The first lumbar vertebrae may fuse with the sacrum, in that case it will be referred to as sacralization of the lumbar vertebrae, okay? Or else the first sacral vertebrae may be separate and may not fuse with the other sacral vertebrae. In that case, it will be referred to as lumbarization of the sacral vertebrae, okay? So these are two terms which are described. Then the first lumbar vertebrae may have a rib, so that rib is referred to as the lumbar rib, also referred to as the gorilla rib, okay? Then there are two clinical conditions described in this region. One is referred to as fondylolysis, another is fondylolisthesis, okay? Fondylolisthesis means the body of the vertebrae is separated from the vertebral arch, okay? And fondylolisthesis means the listeris means protrusion of the vertebrae. The vertebral body will be protruding forward, okay? Then there may be intervertebral disc prolapse. This prolapse between L4 and L5 is very common and when we say disc prolapse, it is the nucleus pulposus of the intervertebral disc that protrudes forward and it compresses the nerve root, okay? If a single nerve root is compressed, it is referred to as radiculopathy, the pain will be referred to the region of that nerve, okay? If multiple nerve roots are involved, which will form the sciatic nerve, so that clinical condition is referred to as sciatica, okay? So pain radiates along the course of distribution of the sciatic nerve, okay? So this was all about the lumbar vertebrae. Now let's move on to the bony pelvis. So bony pelvis is formed by the two hip bones, sacrum and the coccyx. First we'll cover the sacrum in detail. So here we can see the sacrum, viewed from the anterior aspect, so what all are the parts of the sacrum? This upper part is the base of the sacrum, this lower part is the apex of the sacrum and there are four surfaces, anterior or the ventral surface, posterior or the dorsal surface and there are two lateral surfaces as well, okay? You see the ventral surface, there will be transverse striations will be seen in the region of the fusion of the body of the adjacent sacral vertebrae, okay? And these openings are referred to as ventral sacral foramina, okay? And the base of the sacrum, it is formed by the body of the first sacral vertebrae as well as this region is referred to as the ala of the sacrum. The word ala means wings, okay? So this region is in comparison to wings. So this region is referred to as the ala of the sacrum, okay? Then apex, this region articulates with the base of the coccyx, okay? This midline joint is the secondary cartilaginous joint, the joint between the lumbar vertebrae and the sacrum. This is also a secondary cartilaginous joint. Now let's cover the sacrum from the posterior aspect. The sacrum view from the posterior aspect, we can see the spinous process, the fused spinous process of all the sacral vertebrae, except the fifth sacral vertebrae. In this part, the spinous process is not fused and it leads to an opening here. This is referred to as the sacral hiatus, okay? In the opening of the vertebral foramine, which continues in the sacrum, this opening is referred to as the sacral canal, okay? The sacral canal is in the upper aspect, sacral hiatus is in the lower aspect, okay? And in the posterior aspect, there are sacral crests which are described. There is a median sacral crest formed by the fusion of the spinous process and there is an intermediate sacral crest formed by the fusion of the articular processes of the vertebrae. And there is a lateral sacral crest formed by the fusion of the transverse process of the vertebrae, okay? And these openings are referred to as the dorsal sacral foramina. Here we can cover the attachments also. So this U-shaped marked structure, which you can see, this is the attachment of erector spinae muscle, okay? And the gap between this U is occupied by a muscle that is multifidus muscle, okay? And in the lower part, this area on the enterolateral aspect of the sacrum as well as the lateral aspect of the coccyx on the posterior aspect, this area gives attachment to the gluteus maximus muscle, okay? It has multiple points of origin. This is one of the points, okay? Let us cover the attachments on the anterior aspect as well. On the anterior aspect, in the a lobe of the sacrum, in the lateral part, this region, the muscle is E acus muscle, okay? Then here we can see the E-shaped origin of a muscle. This muscle is pyriformis muscle, okay? Then when we see the lower part, the enterolateral part on the anterior aspect, this muscle is coxegious muscle in the upper part, and in the lower part, the muscle is levator anion, okay? So coxegious occupies the upper two coxigial vertebrae, and the lower two coxigial vertebrae is occupied by levator anion muscle, okay? And what is this written here, O-I-L-S, these refer to the relations in front of the a lobe of the sacrum. From lateral to medial, the relations are obturator nerve, iliolumbar artery, lumbosacral trunk, and the sympathetic chain, okay? So these are the relations from lateral to medial, easily remembered by mnemonic oils, okay? Then in the midline, the sacrum is related with the median sacral vessels, this adjacent to the midline, there is sympathetic chain, then sacrum is also related with the rectum, till the lower two and a half pieces of the sacrum, it is related with the rectum, okay? So this was about the description of the sacrum, and the structures passing through this opening, the ventral sacral foramina will transmit the ventral rami of the nerves, and the dorsal sacral foramina will transmit the dorsal rami of the final nerves, but as you all know on the dorsal aspect, there is a muscle, multi-pedus muscle discovering the openings as well, so the dorsal rami of the nerves will pierce the multi-pedus as well as the erector's final to reach the back, okay? Then in sacrum and bony pelvis, the sex determination is also important whether it is a male sacrum or a female sacrum, for that the most important or the most characteristic feature for identification is the ratio between the ala and the body and the opposite ala, okay? In males, the ratio is 1 is to 2 is to 1, okay? The body will be twice as wide as compared to that of the ala, okay? So the ratio is 1 is to 2 is to 1 in males, and in females, the ratio is 1 is to 1 is to 1, okay? That means the width of the body is equal to that of the width of the ala, okay? And there is something called as sacral index, which is breadth upon the height of the sacrum multiplied by 100, it is about 116 or more in females because the breadth of the sacrum is more. The breadth of the sacrum is more in females, why? Because the ala of the sacrum is wide, okay? That's why the ratio is 1 is to 1 is to 1, okay? So sacral index is more in females, it will be less in males, and this point also you can say the ratio between ala, body and the opposite ala for sex determination of the sacrum. And also the shape of curvature of the sacrum, if you see the curvature, in males it is a smooth, C-shaped curvature, okay? Whereas in females, it is an abrupt curvature is referred to as day-shaped curvature, okay? This pelvis is of male, so that's why all male features we are able to see. Also in the bony pelvis, if we see for sex determination, the subcutic angle is the most important feature. The subcutic angle is acute or less than 90 degrees in males, and it is more than 90 degrees in females, okay? Now let's cover the other features of the bony pelvis. So the sex determination we covered about the subcutic angle, what all other questions can be asked in bony pelvis? First of all, you should be clear about the individual hip bones, okay? Any part of the hip bone may be asked, okay? Then the pelvic inlet and outlet, the boundaries of pelvic inlet and outlet can be asked. So we should know, there's something called as pelvic brim. Here we can see this purple colored marked structure, this is the pelvic brim. So the structures forming the pelvic brim are important, we'll cover the structures one by one. So in the midline, there will be pubic symphysis, the secondary cartilaginous joint, right? And there is pubic crest, then if it raise forward, there is pectin pubis or the pectinial line, then there's an elevation here that is referred to as the heliopubic eminence and which will continue as the arcuate line, so on the medial aspect of the hip bone. This line is referred to as the arcuate line, then it will reach up to the sacroiliac joint, then the anterior margin of the aloe of the sacrum, then anterior margin of the body of the sacrum, okay? This anterior most projection is referred to as sacral promontory, okay? So once we raise the sacral promontory, we can continue on the other side as well as that it becomes a complete circular structure that is referred to as the pelvic brim, okay? While describing the pelvic brim, there is a line called as linea terminalis which has been described, which includes this pubic crest, pectin pubis as well as the arcuate line, okay? So if we just raise this entire line, that is referred to as linea terminalis, okay? And when we trace it completely, so that will be the pelvic brim, okay? So all these margins are also forming the pelvic inlet. So above this pelvic brim, this whatever area is seen that is referred to as false pelvis and inert to this the area which is seen that is referred to as true pelvis, also referred to as lesser pelvis, okay? Now let's cover the boundaries of the pelvic outlet. Here we can appreciate the pelvic outlet, so it will be formed by the pubic symphysis on the anterior aspect. Then this is the ischio-pubic ramus connecting the ischium and the pubis, ischio-pubic ramus and the ischial tuberosity and connecting the ischial tuberosity to this coccyx and the sacrum there is a ligament which is referred to as the sacro tuberous ligament. So sacro tuberous ligaments will form the boundary of the pelvic outlet and posteriorly in the midline there is coccyx, okay? So all these structures will form the boundaries of the pelvic outlet, okay? Boundaries of pelvic inlet, pelvic outlet, why this is important? Because when you study the passage of the birth canal, okay, so all these diameters are important. So we will be repeating these things in the final year obstetrics, okay? So in final year obstetrics by also you will be asked about these things, okay? And in obstetrics there is something called as conjugates which are described with respect to the pelvis. So what do we understand by conjugate? It is the distance between the pubic symphysis and the sacrum but there are many points which are described. I will just quickly brush through one by one. One is referred to as external conjugate which extends from the upper margin of this pubic symphysis to the spine of the first sacral vertebrae, okay? That is on the posterior aspect that is the external conjugate and there is one true conjugate which extends from the upper margin of the pubic symphysis to the sacral promontory that is a true conjugate. And there is a diagonal conjugate which extends from the lower margin of the pubic symphysis to the sacral promontory, okay? Clinically this diagonal conjugate is very important because this can be measured in the clinic by per vaginal examination, okay? So this diagonal conjugate becomes one of the parameters to assess the pelvic outlet, okay? Then there is one conjugate which is referred to as obstetric conjugate that refers to the smallest diameter between the pubic and the sacrum, okay? That is a obstetric conjugate. And when you study more in details, we will find that there are various types of pelvis which are described, gynaecoid pelvis, android pelvis, anthropoid pelvis, platypalloid pelvis, okay? Details of all this you will be learning in final year obstetric, okay? So this was all about this particular session. If you all want PDF handout, you all can send a WhatsApp message at this number and please do watch the other sessions of this YouTube channel, okay? Thank you.