How many bones can you find in the human body?
There are a total of 206 bones in the adult human body. They range in size from the tiniest found in the middle ear, to the largest that forms our thigh. The human body has an amazing array of different bones, many of which you can find on yourself or on a skeleton. Knowledge of the skeletal structure of the human body is essential to know before any anatomy exam, especially in clinical situations where accurate descriptions of bony trauma will be required. In this article, we will systematically go through all the bones of the body, describe their location, and joints. In addition, we will conclude with some clinical relevance using surface anatomy.
There are three main types of joints: fibrous, cartilaginous, and synovial.
Suture joint - These joints are formed between bones via short fibers of dense connective tissue. In other words, the bones are locked together like a puzzle. These are joints that allow for no movement at all (synarthrotic). Examples include the joints between the bones of the adult skull.
Syndesmotic joints - These joints are comparable to suture joints but have slightly longer joint fibers (ligamentous connection between bones). Hence, they allow for minimal movement with a slight degree of mobility (therefore they are known as amphiarthrotic joints). An example is the interosseus membrane between the radius and ulna.
Gomphosis - These are particular to the oral cavity; like a peg in a socket. This joint is the attachment of the tooth socket for the teeth and they allow for no movement (synarthrotic - exception of tooth shedding from baby to adult teeth).
Symphysis - These joints allow for very little movement (hence are termed amphiarthrotic), and are found in the midline (with the exception of the atlantoaxial joint, which is a synovial joint). They are joined together by fibrocartilage typically in the shape of a wedge or pad. Examples include the pubic symphysis and the intervertebral disc joints.
Synchondrosis joints - These joints allow for no movement, and hence are termed synarthrotic. They are joined by a rigid hyaline cartilage bridge. Examples include the diaphyseal epiphyseal joint (where the growth plate is) of any long bone, and also the first sternocostal joint. Hyaline cartilage is hard and almost bone-like.
These are the most common joints in the body. They are found in the appendicular skeleton e.g. knee, hip, and shoulder. They are also found in the axial skeleton e.g. zygapophyseal joints between the facets of adjacent vertebrae. Synovial joints are defined by the presence of a fluid filled synovial membrane lined joint cavity, which lies between the articulating bony surfaces. All synovial joints are referred to as diarthrotic, as they are freely movable in one or multiple planes. There are numerous types of synovial joints.
Plane joints (gliding) are where surfaces of the bones slide across each other. The intercarpal joints of the wrist region are an example of this. They are uniaxial, in that they only move in one surface plane making a linear motion.
Hinge joints are uniaxial joints that allow for angular motion in a single plane such as flexion and extension. The definition is when part of a bone wraps around another in a cylinder-like structure; like the hinge of a door. Examples include the knee joint which forms between the femoral condyles and the tibial plateau, and the elbow joint, which forms between the humerus and the bones of the forearm (radius and ulna).
Pivot joints are also uniaxial joints, however, they only permit rotational motion. They consist of a circular part of a bone that rotates inside the ligament of another. An example is the atlantoaxial joint, between the Atlas (C1) and axis (C2) cervical vertebrae, that allow us to rotate our head.
Condyloid joints are found between two articulating surfaces; one oval articular surface nestles within the depression of the opposing articulating surface. The difference between these and ball and socket joints, is the shape of the articulating surfaces in condyloid joints; the joint surfaces are oval instead of spherical. These are biaxial joints that produce angular motions, as they are able to flex and extend, as well as abduct and adduct. The radiocarpal joint, between the radius and the scaphoid, is an example.
Saddle joints are formed between convex and concave articulating surfaces. An example is the first carpometacarpal joint, between the trapezium and the metacarpal bone of the thumb, which enables us to oppose our thumbs. These joints create angular motions in several planes, opposition included, and are known as biaxial.
Ball and socket joints
Ball and Socket joints are characterized by the spherical shaped head of a bone lying inside a spherical or round cavity of another. Examples include the hip joint and the shoulder joint. The shoulder joint, however, is a little more complex than the hip joint, which will be discussed later. These joints are multiaxial, meaning they can move in all directions creating angular motions that include circumduction and rotation.
The skull is formed by a number of plate-like bones coming together via suture joints. Together, they form the bony foundation of the cranial cavity. There are a number of bones that are joined together by suture joints, which result in the skull forming a rigid cavity in which the cerebrum and cerebellum are housed.
The frontal bone - This bone forms the anterior part of the skull’s surface, as well as the superior part of the bony section of the nose. It overlies the frontal lobe of the brain. It contains the frontal air sinus, which may become filled with fluid in cases of sinus infection and congestion, and also makes the frontal bone lighter. The frontal bone also forms the floor of the anterior cranial fossa, in which the frontal lobe of the brain resides.
The temporal bones - This bone is paired (left and right sides) where it has squamous portions and petrous portions. The squamous portion forms the external surface of the skull, and the petrous portion houses the vestibulocochlear nerve and its branches. These bones also form the posterior two thirds of the floor of the middle cranial fossa, as well as the anterior surfaces of the posterior cranial fossa. The vestibulocochlear nerve is able to leave (move laterally away from midline) the cranial vault via the internal acoustic meatus, which is a small opening that also allows the facial nerve to leave the skull. The vestibulocochlear nerve then divides in the inner ear into its vestibular and cochlear branches. The squamous portion forms the lateral inferior surface of the skull and contributes a process to the zygomatic arch. The paired bones overlie the temporal lobes of the brain. The jugular foramen and foramen lacerum are also found at the posterior and anterior borders of the bones respectively.
The parietal bones - Also paired, they form the superolateral surface of the skull, posterior to the frontal bone. These bones overlie the parietal lobes of the brain. The superior sagittal sinus is an important dural venous sinus that attaches to the internal surface of the bones and part of the frontal bone in the midline.
The occipital bone - Forms the most posterior surface of the skull and overlies the occipital lobe. The cerebellum also sits in the cerebellar fossa of this bone. The foramen magnum is found in this bone. The occipital bone has occipital condyles that project from its inferior surface and articulate with the Atlas (C1) vertebra. The most posterior surface of the occipital bone is where the highest, superior, medial, and inferior nuchal lines are found. This is where layers of muscles that move the neck and back attach.
The sphenoid bone - This is an important bone that forms the anterior and medial floor of the middle cranial fossa, and houses the pituitary gland within its body (sella turcica). The entire bone looks like a butterfly when seen from above, and has a keystone-like place in the base of the skull. It has greater and lesser wings, with the greater wings forming the floor of the middle cranial fossa, and the lesser wings forming the most posterior region of the anterior cranial fossa. The bone has many foramina, which allow numerous cranial nerves (optic via the optic canal, oculomotor via the superior orbital fissure, trochlear via the superior orbital fissure, all three divisions of the trigeminal nerve and abducens via the superior orbital fissure), to leave the cranial cavity and innervate the eyes and face. The sphenoid bone also contributes a small part of the lateral surface of the skull via its greater wing. It articulates with the frontal bone anteriorly, the temporal bone posteriorly, the parietal bone via the lateral edge of its greater wings, and with the clivus, the anterior superior projection of the occipital bone, on which the brainstem and basilar artery are found.
The ethmoid bone - This bone forms the most anterior, midline section of the anterior cranial fossa. The bone has numerous perforations in its surface, which allow the nerve fibers of the olfactory nerve(CN I) to enter the cranial cavity, and synapse with the olfactory bulb. The perpendicular plate of the ethmoid bone forms the superior part of the bony nasal septum, with the vomer forming the posteroinferior part. The septal cartilage forms the cartilaginous section of the septum anteriorly.
The auditory ossicles - The middle ear is where the three smallest bones in the body are found: Malleus, Incus, and Stapes. The tympanic membrane (eardrum) forms the boundary between the outer ear and the middle ear. The sounds cause the eardrum to vibrate, and hence these three ossicles to transmit the kinetic energy. Stapes articulates with the round window via its footplate, which then causes electrochemical transmission of sound via the changing pressures in the inner ear.
The lateral surface of the skull has a point known as the pterion, where four bones of the skull come together. This point is just superficial to the middle meningeal artery.
The occipital protuberance (unpaired) is an easily palpable landmark that projects from the posterior surface of the occipital bone.
The lower jaw is known as the mandible. The mandibular condyle articulates with the temporal articular process. The temporomandibular joint (TMJ) is able to protract and retract as well as elevate and depress the mandible. The TMJ is the only synovial joint found in the skull. The ramus of the mandible is the section inferior to the condyle, and forms its posterior edge. The angle is where the corner of the mandible is, and the body is the jaw itself, where the teeth attach. The mandibular foramen is an opening on the internal surface of the ramus, and allows the inferior alveolar branch of the mandibular nerve (a branch of the trigeminal nerve) to enter the mandible and innervate the lower teeth.
The upper jaw is known as the maxilla. The maxilla contains an air sinus, which lightens the bone and has a role in the sound of phonation. The maxilla articulates with the nasal bones at the lateral margin of the bony nasal septum and with the zygomatic bone at lateral margin.
The zygomatic bone forms a joint with the zygomatic process of the temporal bone to form the inferior part of the zygomatic arch. The superior part of the arch is formed by the zygomatic process of the frontal bone.
The nasal bones form the bony structures of the proximal nose, and the frontal bones join them superiorly. They lie on each side and are joined at the midline forming the bridge of the nose.
The lacrimal bones are small bones that contribute to the inferomedial part of the floor of the bony orbit. The other bones forming the orbit are the frontal bone forming the posterior superior surface and the sphenoid bone (greater wing) forming the back of the orbit. The maxilla forming parts of the inferior and posterior surfaces. The ethmoid bone forms the medial surface of the orbit.
The teeth form the gomphosis joints with the maxilla and mandible. The adult typically has 32 teeth: 8 incisors (four on the upper jaw and four on the lower), 4 canines (two on each jaw), 8 premolars (four premolars on each jaw), and 12 molars (6 molars on each jaw - includes the wisdom teeth). These are easily located, and all have defined functions. The incisors cut and slice the food, the canines shred and tear the food, and the premolars and molars grind the food.
The hyoid bone is a bone that resides in the cervical region, superior to the thyroid cartilage. It is special in the sense that it has no bony attachments, but gives support to the upper airway.
The parotid duct (Stenson’s duct) empties into the mouth opposite (lateral) to the second upper molar - location can be approximated using the tongue.
There are 7 cervical vertebrae, 12 thoracic vertebrae, and 5 lumbar vertebrae. The vertebral column also includes the sacrum, which is typically formed from 5 fused vertebrae and the coccyx, usually formed by three or more fused vertebrae. Each group of vertebrae is unique in their anatomy and therefore have adapted to their function(s).
The seven cervical vertebrae are the smallest. The 1st and 2nd cervical vertebrae are unique in their anatomy, as they articulate with the skull, and stabilize the head to enable nodding and shaking of the head. C1 is known as Atlas (after the Greek titan who holds up the skies). This vertebra has large articulating processes that form joints with the occipital condyles. It does not have a body, and is instead ring shaped. C2 is known as the axis, and has articulating surfaces that form zygapophyseal joints with the inferior facets of the Atlas. This vertebra can easily be identified by the presence of the odontoid peg (dens), a superior projection that allows the axis to remain closely bound to the atlas (and stabilized by the atlantoaxial ligaments), and enables smooth movement of the skull for rotational motions. Nodding movements occur at the atlantooccipital joint.
The remaining five cervical vertebrae are very similar in structure. They all have horizontal facet joints, and are stacked like coins. This means that they are inherently unstable, hence the uncovertebral joints. These are bony ridges on the lateral surfaces of the vertebral bodies that stabilize the cervical spine. There is also a large amount of surrounding musculature, fascia, and ligaments. The only thing to note is that C7 has a prominent spinous process, which is why it is called the vertebra prominens (palpable). The cervical spinous processes are bifid. Also, the cervical vertebrae all have foramen within their transverse processes, and they are simply called the transverse foramen. The vertebral artery ascends through these foramen and enters at the level of C6. The vertebral veins also run in this foramen.
The cervical spine itself has a large degree of mobility, including flexion, extension, lateral flexion, and rotation.
The twelve thoracic vertebrae have heart shaped bodies, and have inferiorly directed spinous processes. The transverse processes articulate with the neck of each of the ribs. The vertebral canal get progressively smaller as you descend in the vertebral column since spinal nerves gradually leave to innervate the limbs and the trunk. The zygapophyseal joints are directed in a vertical orientation, which limits anterior and posterior movement of the vertebrae.
The lumbar vertebrae have large kidney bean shaped bodies, with thick short pedicles and short sturdy spinous processes. The zygapophyseal joints connect to each other in a horizontal configuration, which allows the lumbar region to have a great degree of mobility, including flexion, extension, and rotation.
Between each two vertebrae of the vertebral column, intervertebral foramen (paired) can be found. These paired foramina are where the mixed spinal nerves leave the spinal canal, and form the nerve plexi and other innervations.
There are 7 true ribs, 3 false ribs, and 2 floating ribs. They all form costovertebral joints with the thoracic vertebrae. The true ribs are named as such since they form a direct articulation with the sternum anteriorly. The false ribs also form a connection with the sternum anteriorly, but it is via costal cartilage, and the floating ribs do not form connections anteriorly at all.
Posteriorly, the ribs form costovertebral joints with the thoracic vertebrae, which consist of one facet joint with the margin between two adjacent thoracic vertebrae, and another joint between the neck of the rib and the transverse process of the thoracic vertebra. These joints allow for the bucket handle movement, allowing for expansion of the lungs during the breathing mechanisms.
The spinous process of C7 known as the vertebral prominens is easily palpable at the posterior base of the neck.
The scapula is a triangular shaped bone that sits on the surface of the posterior thoracic wall. It forms the scapulothoracic joint via its anterior surface. This is a purely physiological joint, as there is no bony connection between the scapula and thoracic wall itself.
The glenoid fossa projects from the superolateral surface of the scapula, and articulates with the head of the humerus. The glenoid fossa is deepened by the glenoid labrum (a ring of cartilage), which also provides a suction effect for the joint. The glenohumeral joint is a highly mobile joint, but is unstable as a result. Although the glenohumeral joint is a ball and socket joint, the glenoid fossa (the socket) is shallow like a dish. The head of the humerus is also semi-spherical, and has little bony support. This is counteracted by the rotator cuff muscles forming a strong muscular cuff formed of four muscles (supraspinatus, infraspinatus, teres minor and subscapularis). The rotator cuff muscles surround the head of the humerus and holds it in place in the glenoid fossa. There is also significant ligamentous support in the form of glenohumeral ligaments. The tendon of the long head of biceps (which runs in the intertubercular sulcus or bicipital groove and inserts onto the supraglenoid tubercle) also provides inferior support during external rotation of the shoulder.
The scapula has a supraspinous fossa and an infraspinous fossa, which are the points of origin of the supraspinatus and infraspinatus muscles. The scapular spine divides the two. The suprascapular notch is a small notch found on the superior margin of the supraspinous fossa. The suprascapular nerve runs in the space, and the suprascapular artery runs above it.
The clavicle articulates with the manubrium of the sternum medially via its rounded medial surface. Laterally, its flat surface articulates with the acromion of the scapula. The bone is s shaped and lies superficially under the skin. The sternoclavicular joint is a saddle synovial joint, and the acromioclavicular joint is a gliding synovial joint.
The humerus articulates with the glenoid fossa at the glenohumeral joint i.e. the shoulder joint. It has an anatomical neck (directly below the head of the humerus) and a surgical head (the initial section of the superior shaft, below the tubercles). The shaft is the long part of the bone, and it has two articulating surfaces at its distal end, the trochlea and capitulum, which articulate with the ulna and radius, respectively. The humerus also has a spiral groove in which the radial nerve runs. Due to this anatomy, humeral fractures may result in radial nerve palsy causing wrist drop.
This region is formed by the radius and ulna. The head of the radius lies proximally, and sits within the annular ligament, which attaches onto the ulna above the flat quadrate ligament. The head of the radius articulates with the capitulum of the humerus. The base of the radius is large and forms the radioscapholunate component of the wrist joint.
The ulna has a large proximal end, which has the trochlear notch, in which the trochlea of the humerus articulates. The posterior part of the ulna has a large olecranon process also known as the elbow. The ‘funny bone’ is a common saying that actually does not include a bone at all. It’s the ulnar nerve that runs behind the medial epicondyle which projects from the medial surface of the humerus. If you knock this region of the elbow, it sends a tingling sensation down the forearm, hence the name. The radius and ulna are connected along their length by a strong interosseous membrane, which is perforated by vessels. They have radial and ulnar styloid processes on the lateral surface of their distal sections (when looking at the bones individually).
The carpal bones form the bony basis of the wrist region. They are best learnt by dividing them into rows. The proximal row consists of the lunate which articulates with the medial section of the distal radial articulating surface. The triquetrum articulates with the triangular fibrocartilaginous complex and indirectly with the distal articulating surface of the ulna. The pisiform is a pea-like sesamoid bone (a bone that lies in a tendon) that sits on top of the triquetrum and lies within the tendon of flexor carpi ulnaris. The scaphoid articulates with the distal radius and is cashew shaped. It links the proximal and distal rows of carpals.
The distal row consists of the trapezium, which articulates with the first metacarpal (remember trapezium with the thumb). Next to the trapezium, is the trapezoid, a smaller carpal bone that articulates with the second metacarpal. The capitate lies radially, and articulates with the third metacarpal (think of capitate as in capital city found in the centre of a country). The hamate has a prominent hook you can locate on its anterior surface, and forms joints with the fourth and fifth metacarpals.
The wrist joint itself is formed between the distal articulating surface of the radius, and the scaphoid and lunate carpal bones. The distal articulating surface of the ulna also articulates with the triquetrum via the triangular fibrocartilaginous complex.
The hand is formed by the metacarpals and phalanges. It is a complex structure with numerous small interconnecting bones. The metacarpals connect the carpals to the phalanges. The first metacarpal articulates with the trapezium carpal. The second metacarpal articulates with the trapezoid carpal bone. The middle metacarpal articulates with the capitate carpal bone. The fourth and fifth metacarpals articulate with the hamate bone.
The phalanges are divided into proximal, middle, and distal, which get progressively smaller the more distal you look. The thumb only has proximal and distal phalanxes, and forms a bi-concave convex saddle joint with the trapezium via its metacarpal. It is the combination of this joint and our elongated thumbs that allow us to oppose the thumb and therefore perform complex tasks with our hands.
The clavicle has a subcutaneous course and is easily palpable along its course. The manubrium and sternum lie in the midline of the chest, and are also easy to palpate.
The radial and ulnar styloid processes can be found close to the wrist joint (distal in lateral and medial anatomical position).
The posterior surface of the radius is where we find the dorsal tubercle of Lister. The extensor pollicis longus wraps around this landmark.
The olecranon arises from the posterior surface of the ulna and is the insertion point of the triceps brachii.
The sacrum articulates with the wedge shaped body of L5 and also with the sacral articular processes. This reduces the pressure on this level of the vertebral column. There are strong sacrospinous, sacrotuberous, and iliolumbar ligaments that offer support to the bony anatomy. The sacrum sits in the midline as the posterior margin of the pelvic inlet. The sacrum has ala (wings) and sacral foramina, which allow the sacral spinal nerves to leave the vertebral canal two nerves at a time.
The pelvis is a unified bone formed by three separate bones. These are the ilium, ischium, and pubis. All three bones join together in the acetabulum (hip socket). The ilium has a large crest that forms the bony superior edges of the false pelvis. Notable landmarks on the ilium include the anterior superior iliac spine (ASIS), to which the inguinal ligament attaches. The anterior inferior iliac spine (AIIS) lies below the ASIS, and is where the rectus femoris muscle attaches.
The ischium is the inferior of the three bones, and it has prominent tuberosities on its inferior surface. It is where the hamstring muscles attach, and is the surface we sit on (sit bones). The ischial spines are found superiorly to these, and form the insertion point of the sacrospinous ligament. This ligament divides this space of the superior and inferior sciatic notches which forms the greater and lesser sciatic foramen. The sacrotuberous ligament (which runs from the sacrum to the ischial tuberosity) then forms the inferior margin of the sciatic foramina.
The pubis is the anterior bone of the pelvis. The pubic symphysis joint is a joint between the two pubic bones in the anterior midline. Lateral to this joint on the superior pubic rami, is where the pubic tubercle can be found. This is where the inguinal ligament attaches medially. There is a superior and inferior pubic ramus on each side, which are separated by the obturator foramen. The obturator nerve leaves via this foramen to innervate the medial compartment of the thigh.
The hip joint is a ball and socket joint and is formed between the head of the femur and the acetabulum. It is a deep joint reinforced by the acetabular labrum and strong ligaments, namely the iliofemoral, ischiofemoral, and pubofemoral. The iliofemoral is the strongest ligament in the human body and has two distinct bundles. Hence it is also known as the ‘y ligament of Bigelow.’ It is a highly strong and mobile joint.
The thigh is the proximal region of the leg and the bony basis is the femur. The femur is a long bone that forms two condyles distally that articulate with the tibial plateau. The shaft of the bone angles inferomedially, which makes an angle from the vertical called the Q angle. The lateral surface of the superior femoral shaft gives rise to the greater trochanter, which is the site of insertion of the short external rotators of the hip. The lesser trochanter projects from the medial surface of the shaft, lower than the greater trochanter, and is the site of insertion of the iliopsoas muscle. The posterior surface of the femoral shaft gives rise to the linea aspera (bony landmark), which is the insertion site of the vastus lateralis and medialis.
The medial condyle (distal) is more rounded and projects further forwards. The condyles sit on the C shaped medial and rounded lateral menisci, respectively. The menisci act as a cushioning for the femur and improve the congruence of the joint. The patella (kneecap) is a sesamoid bone (a bone that lies in a tendon), that sits anterior the knee. It protects the knee joint, and improves the momentum about which the quadriceps act on the leg to cause knee extension.
The leg is the distal part of the lower limb, and is formed by the tibia medially and the fibula laterally. The tibia is the bone that forms the knee joint with the femur as the fibula attaches to the tibia via the proximal tibiofibular joints. The bones are connected along their length by a strong interosseous membrane, which is perforated by vessels. The tibial plateau is the term given to its superior articulating surface, and is divided in the midline by an intercondylar eminence. The anterior cruciate ligament attaches just anterior to the eminence, and runs upwards in a diagonal fashion to insert on the medial surface of the lateral femoral condyle. The posterior cruciate ligament arises from the medial surface of the medial condyle posteriorly, and inserts onto the posterior aspect of the superior tibia.
The foot has numerous bones. The heel is formed by the calcaneus. The ankle joint is formed between the distal articulating surface of the tibia, medial surface of the fibula, and the talus. This forms a mortice like joint, which enables the ankle to move like a hinge joint, allowing for dorsiflexion and plantarflexion.
The cuboid bone lies laterally while the navicular and cuneiform bones lie medially proximally and distally, respectively. There are three cuneiform bones; medial, intermediate, and lateral. These articulate with the first, second, and third metatarsals. The cuboid articulates with the fourth and fifth metatarsals. The metatarsals articulate with the proximal phalanges, which articulate with the middle phalanx, which articulate with the distal phalanx. The hallux (big toe) only has two phalanges, like the thumb. The base of the fifth metatarsal is prominent and projects posterolaterally. It is easily palpated along the middle of the lateral border of the foot.
The medial malleolus (medial ankle) is a rounded projection, and is a distal landmark of the tibia. The lateral malleolus (lateral ankle) is a rounded projection and is a distal landmark of the fibula.
The greater trochanter is palpable as a projection from the superior shaft of the femur.
The anterior superior iliac spine (ASIS) is the origin of the inguinal ligament, and the pubic tubercle is the insertion point. The femoral artery is found one centimeter below the midpoint of this ligament. The deep ring is found at the midpoint of the ligament, just above the artery.
The head of the fibula is the insertion point of the biceps femoris. The common peroneal nerve wraps around the neck of the fibula, and compression here can result in foot drop.