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Surface anatomy of the abdomen and the lower extremity

Overview of the surface anatomy landmarks found in the abdomen and lower limbs.

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Transcript

Hey everyone! This is Nicole from Kenhub, and welcome to this tutorial on the surface anatomy landmarks of the abdomen and lower limb.

So, with a bit of luck, you’ll pretty unlikely to have a patient walk into your surgery without a top layer of skin. So, fortunately or unfortunately, from a diagnostic perspective, most of our anatomy is hidden away out of sight and, therefore, it’s important that we are able to recognize the landmarks that we can see, known as the surface anatomy, so that we are able to find our way around the body. In fact, knowledge of the surface anatomy is required to perform a range of classic methods of examination such as palpation, percussion, auscultation, inspection and function testing.

So, in this particular tutorial, we’re going to be focusing on the surface anatomy landmarks of the abdomen and the lower limb starting with the abdomen and the pelvis, and then moving down to the lower limb. If you’d like to learn about the surface anatomy of the other parts of the body, be sure to check out our other tutorials focusing on the head and neck as well as the thorax, upper limb and back in more detail. But, for now, let’s begin as promised by looking at the surface anatomy landmarks of the abdomen and the pelvis.

So, the first landmark of the abdomen we’re going to look at is the linea alba. Here we can see the outline of the fibrous linea alba running down the midline. And as you can see, it runs in line with the rectus abdominis muscle underneath from the level of the xiphoid process just here down to the pubic symphysis just here. It’s worth noting that the linea alba might be distended or not visible at all on a person who’s obese.

If we follow the trajectory of the linea alba, we also see the umbilicus or the navel or as it’s even more commonly known, the belly button. The umbilicus is really just a scar from where the fetal umbilical cord was once attached when we were developing in the womb.

Moving downwards slightly to the pelvic region, we can see the anterior superior iliac spine, which is the anterior extremity of the iliac crest of the pelvis. This landmark can be easily palpated and in some individuals, can be seen protruding slightly or even significantly, if a person is very underweight. And this is an important landmark as it helps in the identification of some other clinical landmarks such as McBurney’s point which is located approximately one-third of the distance between the anterior iliac spine and the umbilicus. McBurney’s point roughly corresponds to the most common location of the base of the appendix where it is attached to the cecum and it’s commonly used to determine the site of incision during some surgeries like appendectomies.

Staying around the pelvic region, the next landmark we’ll look at is known as the inguinal crease, and this is a crease that extends from the anterior superior iliac spine to the pubic tubercle. This landmark can be distinguished in most people except perhaps in obese individuals where the crease may be distended.

Moving back to our male body, we can see that the external genitalia are easily distinguished. The penis, the glans penis, and the scrotum are all useful surface anatomy landmarks. Moving over to the female external genitalia, the only landmark we can see on this particular image is the mons pubis. This is basically a rounded mass of fatty tissue that covers the pubic symphysis just here, and this fatty mound segments to create the labia major and is generally covered in hair in post pubescent females.

So, in order to show you the rest of the female genitalia, we need to move away from our model briefly to look at the body from a different viewpoint. And in this image, we can see the female genitalia as if we’re looking directly upwards from an inferior viewpoint. And here highlighted in green, we can see the opening to the vulva vestibule and this cut through here looking at things from an anterior perspective shows us more of the vulva vestibule.

Next, we have this tiny little protuberance just here known as the glans clitoris, and most of the anatomy of the clitoris is internal but we can usually see this part on the surface of the body. Just posterior to the glans clitoris, we can see the labia minora, and just a note, don’t confuse this with the labia major which we can’t see directly on this image. The labia minora is one of the most obvious landmarks of the female genitalia and are roughly indicated in green just here.

Next, we have the labia majora which is highlighted in green, and the labia majora are two folds of skin found on either side of the labia minora. And finally, just posterior to the female genitalia and anterior to the anus, we can see the perineum.

Alright, now that we’ve looked at the abdomen and the pelvic region, let’s move on to look at the surface anatomy of the lower limb.

So starting on the anterior aspect of the upper part of the lower limb, we can see the form of the quadriceps femoris muscle, and this muscle is very large and pretty much takes up the majority of the front of the thigh. If we take a look at the muscle underneath, we can see more clearly how the form of the anterior thigh is largely thanks to this muscle’s shape.

The next surface landmark on the anterior part of the lower limb is the patella. You probably may now this as the kneecap. So, if we take a closer look, we can see that this is a roughly triangularly-shaped bone that covers the front of the knee and this bone forms and fuses gradually, meaning that young infants don’t usually have them but it’s easy to see and palpate on all the children and, of course, on adults.

Let’s move downwards from the patella to the lower leg, where we can see a small lateral bump highlighted here just below the knee and this is due to part of the fibula – one of the two long bones that form the lower part of the leg. The proximal head of the fibula highlighted here has an irregular shape and is directed upward, forward, and medially. This bony protuberance gives rise to the small bump just here.

Another long bone of the lower limb is the tibia, and I want to focus your attention on a particular part of the tibia’s anatomy known as the tibial tuberosity. Now this tuberosity provides an attachment point for the tendons of the quadriceps femoris muscle and results in another bump inferior to the patella that can be easily palpated particularly in individuals with power quadriceps femoris muscles. The shaft of the tibia itself is also easily distinguishable and palpable, and this long bone that can be seen extending from the knee to the foot is our tibia and is what is commonly referred to the shin or the shin bone.

Now, let’s scoot around to look at the body from a posterior view so that we can get a better look at the next few surface anatomy landmarks on the back of the leg, and the first of these that I want to show you is the semimembranosus muscle, which is one of the three muscles of the hamstrings. This muscle has a membranous tendon which runs medially to the tibia and the visibility of this particular landmark depends a lot on the body fat percentage of the individual. It may be tricky to distinguish in an overweight or an obese person.

Moving on downwards to the posterior aspect of the knee joint, we can see a shallow depression known as the popliteal fossa. And this fossa has several structures running through it including the popliteal artery where the popliteal pulse can be taken, the popliteal vein, and the small saphenous vein which terminates around about here as well as the tibial nerve, the common peroneal nerve and the popliteal lymph nodes.

Moving downwards to just below the popliteal fossa, we can see where the triceps surae muscles make up the fleshy bulge seen here at the back of the lower leg. And the larger of these, the gastrocnemius muscle, along with the smaller soleus muscle are collectively referred to as the calf.

The next major landmark we can see on the posterior view of the leg is the calcaneal tendon, more commonly known as the Achilles tendon, and if you know your Greek mythology, you’ll know that this nomenclature is referring to Achilles and his weak heel. But, in contrast to the myth, this tendon is anything but weak. In fact, it’s the thickest tendon in the human body making it easy to palpate in pretty much everyone and is very important in weightbearing during walking and running.

The calcaneal tendon which is the common tendon of the triceps surae muscles and the plantaris muscle inserts onto the calcaneus or the heel bone.

Next, we’re going to take a look at the ankles. At the distal medial end of the tibia is a broad prominence known as the medial malleolus and this prominence protrudes on the medial side of the leg and is commonly referred to as the inner ankle. And now if we take a closer look at the bones, you can get a better view of the part of the tibia that I’m referring to.

Hopping over to the lateral side of the ankle at the lower end of the fibula is the bony prominence known as the lateral malleolus. And the lateral malleolus which is more commonly known as the outer ankle can be better seen here and one thing to notice here is how the medial malleolus and the lateral malleolus are not at a level with one another and you can see how the medial malleolus is a little bit higher.

The calcaneus is a bone of the foot which creates the heel. It’s also known as the heel bone and is the largest of the tarsal bones which can be seen protruding on the posterior aspect of the foot and is the attachment site of the plantaris, gastrocnemius and soleus muscles via the calcaneal tendon as we saw earlier.

Finally, we have the dorsum of the foot which constitutes the upper surface of the foot and contains the extensor digitorum brevis muscle and the extensor hallucis brevis muscle. Among the other structures that are found on the dorsum of the foot is the dorsalis pedis artery whose pulse can be easily palpated here in order to measure the pedal pulse.

Alright, now before we conclude the tutorial, let’s quickly recap the surface anatomy landmarks we’ve just talked about.

So, we saw how the surface anatomy landmarks play an important role in classic methods of examination such as palpation, percussion, auscultation, inspection, and function testing. The first of these landmarks we looked at was the linea alba which runs from the xiphoid process down to the pubic symphysis and is formed by the fibers of the abdominal muscles underneath. The second landmark we looked at was the umbilicus, which is more commonly referred to as the navel or the belly button, and this is essentially just a scar left over from our umbilical cord when we were developing in the womb.

Next were the landmarks created by the anterior iliac spine of the pelvis, and this point is particularly useful in that it helps us to identify McBurney’s point which is located approximately one-third of the way from the anterior iliac spine towards the navel. Running from the iliac spine to the pubic tubercle, we then have the inguinal crease, and this crease can be distinguished in most people except in obese individuals where it may be distended. Next, we looked at the male external genitalia which consists of the penis, the glans penis, and the scrotum. And then we looked at the female external genitalia starting with the mons pubis followed by the vulva vestibule, the glans clitoris, the labia minora, the labia majora, and the perineum.

Moving down onto the lower limb, the next landmark we discussed was the quadriceps femoris muscle which forms the basic shape of the front of the thigh. Next, I showed you the patella more commonly referred to as the kneecap and this is easily palpated in most individuals except young infants as this bone forms and fuses gradually after birth. Moving downward slightly, we next talked about the head of the fibula which forms a small bump on the lateral side of the leg, and not far from this, we also have the tibial tuberosity which is the attachment site for the tendons of the quadriceps femoris muscle discussed earlier and forms a small bump on the anterior aspect of the leg just below the knee. The shaft of the tibia itself also forms a surface anatomy landmark commonly referred to as the shin.

Turning our model around, we went back to the top of the lower limb to look at the semimembranosus muscle which forms the shape that we see here and is a part of the hamstrings. We then moved down to look at this depression on the back of the knee known as the popliteal fossa where several important structures pass through. Below the popliteal fossa, we have the triceps surae muscles which consist of the gastrocnemius muscle and the smaller soleus muscle which together make up the fleshy bulge seen at the back of the lower leg known as the calf.

The next landmark we looked at was the ridge formed by the thickest tendon of the body – the calcaneal tendon – and more commonly known as the Achilles tendon is very important in weightbearing during walking and running and can be easily palpated. We then went on to look at the bones that form our ankles. First of all, looking at the medial malleolus which is formed by the distal end of the tibia and is commonly known as the inner ankle. Slightly lower than the medial malleolus, the lateral malleolus is formed by the end of the fibula and is commonly known as the outer ankle.

Next, we talked about the calcaneus which is a bone of the foot which forms the heel and also aptly known as the heel bone. This is the largest of the tarsal bones and can be seen protruding on the posterior aspect of the foot forming the attachment site of the calcaneal tendon.

Finally, we looked at the dorsum of the foot. This is the upper surface of the foot and contains the extensor digitorum brevis muscle and the extensor hallucis brevis muscle, and the dorsalis pedis artery can also be palpated here in order to measure the pedal pulse.

And that concludes this tutorial today on the surface anatomy landmarks of the abdomen and lower limb. If you’d like to learn about the surface anatomy landmarks elsewhere on the body, go ahead and check out our other videos that cover these in more detail.

Thanks for joining me and see you next time.

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