Video: Body surface anatomy

Have you ever had to go to the doctor because you had a really sore stomach particularly on the lower right side of your abdomen? When you arrived at the clinic, the doctor probably started poking around to try and find out what was going on. The doctor is probably trying to locate your appendix. The surface anatomy of the appendix is also known as McBurney's point and, oh! I think she found it. Don't press too hard. I think it's safe to say that this patient probably has appendicitis. Gross! Let's clean this up and get back to our body's surface anatomy.

Surface anatomy examines the external features of our bodies. A good understanding of surface anatomy is essential in clinical practice. It is key in interpreting medical images and also allows for accurate examination and communication with regards to the location, relations, and appearance of anatomical structures. In today's tutorial, we are going to explore the anterior and posterior surface anatomy of the head, neck, and the trunk – or the axial body; the upper limb, and the lower limb. Within these three regions, we will identify three different types of surface anatomy landmarks which include bony landmarks, soft tissue landmarks, and external organs. Let's dive right in and begin by exploring the anterior surface of the axial body.

The first anterior landmark that we'll meet today is the larynx which is found in the neck. It sits just superficial to the esophagus at the level of the third to sixth cervical vertebrae. The larynx is commonly known as the voice box as it contains the vocal cords. It is an organ which aids in sound production and contributes to breathing by conducting air to the lower respiratory tract.

The larynx is a hollow structure composed of a number of muscles and cartilages which form its framework. One of these cartilages – the thyroid cartilage – forms the laryngeal prominence which is commonly known as the Adam's apple. When trying to palpate your larynx, simply find your Adam's apple.

Lateral to the larynx are the two large-headed muscles of the neck – the sternocleidomastoid muscles. These soft tissue landmarks originate at the sternum and clavicle and insert onto the skull. They are superficially situated muscles whose sternal head stand out at sharp defined ridges forming a slight V shape. They can be identified and palpated when you turn your head from left to right.

The clavicle is a bony landmark which is very noticeable when you shrug your shoulders. It is also known as the collarbone. It is a thin S-shaped bone which connects the bones of the upper limb to the bones of the trunk. Try elevating your shoulders and see if you can spot your clavicle.

Now that you know where to find the sternocleidomastoid muscle and the clavicle, locating our next landmark will be a piece of cake. The supraclavicular fossa is a shallow depression that lies just superior to the clavicle as the name suggests. It extends between the sternocleidomastoid muscle medially and the deltoid muscle laterally.

Moving inferiorly, we meet a bony landmark of the anterior thoracic cage known as the sternum. The sternum is a plate of bone that articulates with the first seven ribs and the clavicle on either side. It consists of three parts – the manubrium, the body, and the xiphoid process which we'll take a quick look at now.

The manubrium of the sternum can be palpated between the clavicular heads. It is a large quadrangular-shaped bone that lies above the body of the sternum. At the superior aspect of the manubrium of the sternum between the two sternal heads of the clavicle is a large indentation known as the jugular notch of the sternum. The jugular notch is also sometimes known as the suprasternal notch describing its location at the top of the sternum. The lower border of the manubrium articulates with the body of the sternum at the sternal angle. This slightly raised ridge can be palpated anteriorly about two centimeters below the jugular notch and is in line with the second rib.

The body of the sternum is the longest part of the sternum. It articulates with the costal cartilages of ribs two to seven. The inferior aspect of the body of the sternum articulates with the xiphoid process. The xiphoid process is the most inferior part of the sternum. It is a small projection of bone that is usually pointed and can be palpated at the base of the chest.

Just below the clavicle and lateral to the sternum is a soft tissue landmark – the pectoralis major muscle. This is a large superficial muscle of the chest. This muscle lies deep to the breast.

Breasts are anatomical landmarks found in both males and females. They are formed of fat, mammary tissue, and overlying skin in both sexes but are usually more pronounced in females. On the external surface of the breast, you can find a small area of pigmented skin. It consists of a raised nipple in the center surrounded by an areola.

We are now moving down to the inferior edge of the ribcage where we meet the costal margin. This is a bony landmark. The costal margin is formed by the cartilages of ribs seven to ten. This becomes more noticeable if you take a sharp exhale out.

Next, we come to the rectus abdominis muscle. If you're a big fan of the gym, or more specifically, if you're a big fan of working your core, you can probably locate this soft tissue landmark pretty easily. You may also know this muscle as your abs as it creates that six-pack look. This muscle originates from the pelvic bone and stretches over the anterior surface of the abdomen to insert at the xiphoid process and lower ribs.

Traveling through the center portion of this muscle is the linea alba. It is a tendinous fibrous raphe that runs vertically down the midline of the abdomen. It extends between the inferior limit of the sternum and the pubis separating the rectus abdominis muscles. This can be clearly visible if you have a low body fat percentage.

On the lateral aspect of the rectus abdominis muscle, we find another soft tissue landmark, the linea semilunaris. This is the tendinous intersection that separates the lateral edge of the muscle from other muscles of the anterior abdominal wall. It usually extends from the tip of the ninth costal cartilage to the pubic tubercle. A weakness at this point can lead to the development of a hernia known as Spigelian hernia.

Next, we come to the umbilicus. This is an easy find. This surface landmark is also known as the navel, or as many people know it, the belly button. It does not depict any underlying soft tissue or bone but rather represents a scar at the attachment site of the fetal umbilical cord.

Moving inferiorly, we meet another bony landmark – the anterior superior iliac spine. This is a component of one of the bones of the pelvis – the ilium. To find this bony landmark, pop your hands on your hips, move your fingers to the anterior aspect of your hips, and see if you can find a sharp notch on either side. These are your anterior superior iliac spines.

The inguinal ligament is another soft tissue landmark. It extends from the anterior superior iliac spine to the pubic tubercle on the pubic bone. This structure can be a little tricky to see but can be palpated along its root from the anterior superior iliac spine.

A surface structure only present in the female is the mons pubis. This is a large fatty tissue situated over the pubic symphysis of the pelvis. The mons pubis segments inferiorly to create the labia majora and in most post-pubescent females is generally covered in hair. The mons pubis is part of the female external genitalia which is known as the vulva. The vulva includes all external parts of the female genitalia.

The male external genitalia include the external portion of the penis which you can see here highlighted in green. This is an external organ of the male reproductive system and the urinary tract. The distal end of the penis is known as the glans penis. The glans penis is covered by a double layer of skin and connective tissue that extends from the neck of the glans penis to just beyond the tip of the penis. This double layer of skin is known as the foreskin or the prepuce.

Just posterior to the penis is the scrotum. The scrotum is essentially a sac composed of the superficial fascia of the abdominal wall internally and the skin externally. It houses the testes, the epididymis, and the dorsal portion of the spermatic cord.

Now that we've had a look at the anterior surface anatomy of the axial body, let's take a look at the posterior surface anatomy.

On the posterior aspect of the base of the head, we find a bony protrusion known as the external occipital protuberance. Distal to this landmark at the bottom of the posterior neck, we meet another bony landmark – the seventh cervical vertebra of the spine. The C7 vertebra has the longest spinous process out of all the cervical vertebrae and can be easily palpated especially when you bend your head forward.

On the posterior aspect of the neck and proximal back, we find the trapezius muscle. This diamond-shaped muscle sits superficially on the posterior neck and proximal back and therefore can be easily palpated.

Let's now take a look at the scapula. The scapula is commonly known as the shoulder blade and is a paired structure located in the upper back. While the scapula itself is not very easy to palpate or see on the surface of the body, three of its landmarks are. The first is the spine of the scapula. It is a long, thin elevation traversing the superior part of the posterior scapula and it protrudes posteriorly making it an easy structure to palpate. The spine of the scapula separates the supraspinous fossa superiorly and the infraspinous fossa inferiorly.

The medial border of the scapula can also be easily identified and palpated under the skin. This thin medial border runs parallel to the vertebral column and as such can also be referred to as the vertebral border of the scapula. The interscapular region of the back lies between the medial borders of both scapulae.

The final point of the scapula that can be palpated is the inferior angle of the scapula. This angle can be a little trickier to find, however, can be easily palpated on someone who has a low body fat percentage. The imaginary scapular line travels through the inferior angle of the scapula.

Inferior to the scapula is a large muscle of the back which actually acts on the arm – the latissimus dorsi muscle. It is a wide muscle and can be palpated from the mid to lower back. This is our climbing muscle as it aids in pulling the arms downward and inward helping you climb. Therefore, if you are big into doing lat pulldowns, you will have very noticeable latissimus dorsi muscles.

Towards the inferior aspect of the latissimus dorsi muscle, we meet the iliac crest. The ilium is a wing-shaped bone which contributes to the structure of the hip and pelvis. Its superior border is the part known as the iliac crest. This landmark can be palpated at the lower back just above the buttocks.

On the lower portion of the back, we can find the lumbar triangle. This is an anatomical space which is bounded inferiorly by the iliac crest, posteriorly by the latissimus dorsi muscle, and anteriorly by the external oblique muscle. Another bony landmark of the pelvis is the posterior superior iliac spine which is located at the posterior most point of the iliac crest. This bony prominence can easily be identified by two smaller circular depressions known as the back dimples or the dimples of Venus.

Between the two posterior superior iliac spines, we can see a shallow triangular depression known as the sacral triangle. The sacral triangle overlies the sacrum and lies between the dimples of Venus. In this region, the ilium articulates with the sacrum at the sacroiliac joint. This joint is extremely strong as it supports the full weight of the upper body. It can be palpated just below the posterior superior iliac spine. Just find the dimple and move distally to reach the joint.

The final posterior landmark of the axial body that we'll explore today is the anal region. The anal region is made up of the anal canal, the muscular sphincters, and the anus. The anal region is located just anterior to the tip of the coccyx. The anal canal begins as a continuation of the rectum and terminates at the anus. The anus is the most distal portion of the digestive system.

Moving on to the upper limb, let's take a look at the anterior and posterior surface anatomy of the upper limb.

Let's begin on the anterior surface. The upper limb articulates with the axial skeleton at the clavicle. The distal end of the clavicle articulates with the acromion of the scapula at the superior aspect of the shoulder forming the acromioclavicular joint. The acromion is a bony process which extends laterally from the spine of the scapula. It is easily palpated at its point of articulation with the clavicle.

The surface anatomy of the shoulder is mainly formed by the deltoid muscle. This large muscle sits superficially as a cap over the shoulder extending on the lateral aspect of the arm. If you are a gym buff, then this superficial muscle should be pretty easy to locate and palpate.

Another muscle which can be easily identified is the biceps brachii muscle of the arm. This muscle is a major flexor of the arm at the shoulder and forearm at the elbow. Even if you're not big into working your arms at the gym, if you flex your arm, you should be able to find this muscle.

Towards the distal end of the biceps brachii muscle at the bend of your elbow is the cubital fossa. This triangularly-shaped area of depression contains important neurovascular structures of the arm and the forearm as well as the tendon of the biceps brachii that we just saw.

We're moving distally now to the wrist and the hand where we find the radial foveola, also known as the anatomical snuffbox. This shallow depression on the posterolateral aspect of the hand and wrist junction is named after the historical practice of having ground tobacco – otherwise known as snuff – placed in the depression and then inhaling it through the nose. If you extend and abduct the thumb, the snuffbox becomes more noticeable.

On the palm of the hand, we meet the thenar and hypothenar eminences. The thenar eminence is the soft tissue prominence at the base of the thumb. The four thenar muscles forming this eminence all act on the thumb. On the opposite side of the palm of the hand at the base of the little finger, we find the hypothenar eminence. This soft tissue prominence is formed by the four hypothenar muscles, all of which act at the little finger. The hypothenar eminence is slightly less prominent than the thenar eminence.

Let's flip the arm around now and take a look at the posterior surface anatomy of the upper limb. On the posterior aspect of the arm, we find a long three-headed muscle which is known as the triceps brachii muscle. Like many muscles of the body, this muscle is also more noticeable if it is used regularly. Tricep dips are a handy workout to make your triceps really pop. The triceps brachii muscle inserts onto a bony prominence known as the olecranon of the ulna. This prominence forms the posterior protrusion of the elbow joint. It can be identified in either the flexed or extended position.

Okay, onto the lower limb next.

Moving down to the anterior surface anatomy of the lower limb, we meet the quadriceps muscle group. This is a group of four muscles as its name suggests. As with many muscles, these are more pronounced if you do leg day regularly at the gym. These muscles form the contour of the anterior and lateral thigh and the major flexors of the thigh at the hip.

On the medial aspect of the anterior thigh, we find the femoral triangle. This is a small region located just distal to the inguinal ligament. The femoral triangle contains important vessels which can be easily accessed in this area if necessary.

On the anterior aspect of the knee, we meet a bony landmark known as the patella. This triangular bony protrusion is the largest sesamoid bone or a bone embedded in a tendon in the body and is commonly known as the kneecap. The patella can be easily palpated with the leg in any position. Just distal to the patella, we find another bony landmark – the tibial tuberosity. The tibia is one of the major bones of the leg and articulates with the patella and femur at the knee joint.

On the anterior surface of the proximal tibia just below the articulation with the patella, we find a bony protrusion which is known as the tibial tuberosity. In order to palpate this, first identify your patella and move slightly distally. Traveling over the anterior shaft of the tibia, we find a soft tissue landmark – the tibialis anterior muscle. This muscle aids in forming the shape of the anterior surface of the leg.

The final anatomical landmarks of the anterior surface of the lower limb are the knobbly bony protrusions that you find at your ankle. The raised area on the medial aspect of the leg is called the medial malleolus and is formed by the distal end of the tibia. The bony lateral malleolus is formed at the distal aspect of the fibula and is found on the lateral aspect.

Now that we've had a look at the anterior landmarks, let's explore the posterior surface anatomy of the lower limb.

Let's begin with the gluteal region. This is a large region known as our buttocks. The gluteal region gets its obvious shape with the three large gluteus muscles. The gluteus maximus muscle is easily palpated and identified within this region. The gluteal region is separated down the midline by the intergluteal cleft. The intergluteal cleft runs from the sacrum to the perineum and is often colloquially referred to as the butt crack.

Forming the inferior border of the buttocks is this crease seen here known as the gluteal sulcus. It is worth noting that the gluteal sulcus is not actually formed by the inferior border of the gluteus maximus muscle although the crease does line up with the border. It is instead formed by a fold of the skin.

On the lateral aspect of the thigh, we find a soft tissue landmark known as the iliotibial tract. This large thick band of fascia is a continuation of the tensor fasciae latae muscle. It travels down the lateral thigh to insert into the lateral condyle of the tibia. It aids in stabilizing the hip during working.

On the posterior aspect of the thigh, we find three muscles which together form the ischiocrural, or hamstring muscles as they are more commonly known. The hamstrings comprise the bicep femoris, the semitendinosus, and the semimembranosus muscles which originate at the pelvic bone and insert at either the posterior aspect of the tibia or the fibula of the leg. They form the bulk of the posterior thigh. You can easily palpate the long tendons of these muscles on the medial and lateral aspects of the posterior knee.

The distal aspect of the hamstring muscles form the superior boundary of the popliteal fossa which is the next landmark we're going to look at. The popliteal fossa is a diamond-shaped depression located posterior to the knee joint. The inferior boundary of the popliteal fossa is formed by the two heads of the large calf muscle – the gastrocnemius. Important neurovascular structures travel through this region.

Moving distally, we meet the triceps surae muscles. These are the large muscles of the calf. It is made up of the two heads of the superficial gastrocnemius muscle and the deeper soleus muscle. These muscles can be easily palpated on the posterior aspect of the leg. If you ever watch the Tour de France, you might notice the two heads of the gastrocnemius muscle popping out on the back of cyclists’ legs.

The long tendons of the gastrocnemius and soleus muscle fuse together to form the soft tissue landmark – the calcaneal tendon – which is also known as the Achilles tendon. This thick and strong tendon is both visibly noticeable and palpable at the distal end of the calf. It travels down to insert onto the posterior aspect of the calcaneal bone of the heel.

That brings us to the end of the main landmarks of the surface anatomy of the human body. Before we finish, let's quickly go over some clinical notes on the importance of knowing your surface anatomy.

At the beginning of this video, we briefly mentioned McBurney's point. McBurney's point is the approximate location of the appendix. This point can be simply identified by drawing a line from the umbilicus to the anterior superior iliac spine on the anterior abdomen. The surface projection of the base of the appendix is at the junction of the lateral and middle third of the line from the anterior superior iliac spine to the umbilicus. If a patient presents with pain at the right distal aspect of the abdomen, McBurney's point should be lightly palpated and assessed to examine for appendicitis. This will aid in quickly identifying if further examinations and procedures are necessary to be carried out in order to benefit the patient.

Phew! That was a lot of information. Let's go over a quick summary to wrap it all up.

We began this tutorial by looking at the surface anatomy of the anterior axial body. We meet the most proximal structure – the larynx – which can be simply identified by its cartilaginous structure which forms the Adam's apple protrusion on the neck. Just lateral to the larynx, we identified the sternocleidomastoid muscles of the neck. Just inferior to the sternocleidomastoid muscles, we met the bony clavicle. The clavicle is easily palpated but is particularly noticeable when you elevate your shoulders.

Superior to the clavicle was the supraclavicular fossa which extended from the sternal end of the sternocleidomastoid muscle to the medial edge of the deltoid muscle. At the sternal end of both clavicles, we met the sternum which is made up of three components. The superior aspect of the sternum is the manubrium. The bony indentation of the superior aspect of the manubrium is known as the jugular notch. The inferior portion of the manubrium articulates with the body of the sternum at the sternal angle. The most inferior portion of the sternum is known as the xiphoid process which can be palpated at the center of the chest just below the sternum.

Just lateral to the sternum, we meet the soft tissue pectoralis major muscle, and overlying it, we saw the breast. On the external surface of the breast is the pigmented areola with the nipple at its center. Below the chest, we identified the costal margin which is formed by the medial margin of ribs seven to ten. Attached to the aspects of the costal margin is the rectus abdominis muscle with the linea alba down the midline and the linea semilunaris which travels on the lateral aspect. On the midline of the abdomen, we also saw the umbilicus.

Moving distally, we met the palpable anterior superior iliac spine and attaching inguinal ligament. These structures are part of the pelvic region. The external organs of the trunk included the male and female external genitalia.

Next we had a look at the surface anatomy of the posterior axial body. The posterior landmarks began with the bony external occipital protuberance on the posterior aspect of the skull. The bony spinous process of the seventh cervical vertebra is also palpable at the base of the posterior neck. Overlying the vertebrae is the soft tissue landmark – the trapezius. This is a large muscle of the proximal back and neck which attaches to the bony scapula. The scapula contains several prominent regions such as the spine of the scapula, the medial border, and the inferior angle.

Inferior to the scapula is the latissimus dorsi muscle. This is a large muscle of the lower back which sits superficially. At the inferior end of the latissimus dorsi muscle is the iliac crest. The iliac crest contributes to the composition of the lumbar triangle which is situated on the lateral aspect of the lower back. The posterior superior iliac spine is a posterior extension of the iliac crest and forms a dimple at the medial gluteal region. The sacral triangle sits between the two posterior spines. The articulation between the sacrum and ilium is known as the sacroiliac joint. This joint can be palpated just below the posterior superior iliac spine. Next we saw the anal region which sits just medial to the gluteal regions.

We then had a look at the surface anatomy of the anterior and posterior upper limb. The distal end of the clavicle articulates with the scapula at the acromion process. Attaching to the distal aspect of the clavicle and spine of the scapula, we saw the deltoid muscle. This soft tissue landmark forms the contour of the shoulder. A soft tissue landmark of the anterior arm is the biceps brachii muscle. Its tendon is contained in the cubital fossa, a triangular depression on the anterior elbow.

The most distal structure of the upper limb we discussed were the radial foveola and the thenar and hypothenar eminences of the hand. On the posterior surface, we identified the three-headed triceps brachii muscle. This muscle travels distally to insert onto the olecranon of the ulna.

Onto the anterior surface anatomy of the lower limb. Here we identified the quadriceps femoris muscle group of the thigh. The femoral triangle were also identified at the medial region of the anterior thigh. At the insertion of the quadriceps femoris tendon, we identified the patella or the kneecap. The tibial tuberosity of the tibia was identified as a bony protrusion just below the structure. The final bony landmarks of the anterior lower limb were the bony medial and lateral malleoli at the ankle.

Moving on to the posterior surface anatomy of the lower limb, we saw the gluteal region formed by the large gluteal muscles. In between the two gluteal mounds, we found the intergluteal cleft. Inferior to the buttocks was a crease which is known as the gluteal sulcus.

On the lateral aspect of the thigh lies the iliotibial tract while posteriorly, the surface anatomy of the thigh is formed by the hamstring muscles. Posterior to the knee, we saw the diamond-shaped depression, the popliteal fossa, which can be felt as the hollow behind the knee. Distal to this fossa are the triceps surae muscles made up of the two gastrocnemius heads and the soleus muscles of the calf.

Finally, we identified the large calcaneal tendon on the posterior aspect of the distal leg. It attaches to the posterior aspect of the calcaneal bone.

Concluding this tutorial, we identified the location of the appendix, McBurney's point, and highlighted the importance of locating this structure in suspected appendicitis.

That brings us to the end of this tutorial. We hope this has been helpful in guiding you on the surface anatomy of the human body. Thanks for watching, see you next time, and happy studying!