The cranium has 8 bones and rest on the top of the vertebral column. The skull bones are grouped into two categories; cranial bones and facial bones.
There are eight cranial bones.
- Frontal bone
- Parietal bones (2)
- Temporal bones (2)
- Occipital bone
- Sphenoid bone
- Ethmoid bone
There are fourteen facial bones;
- Nasal bones (2)
- Maxillae (maxillas) (2)
- Zygomatic bones (2)
- the Mandible
- Lacrimal bones (2)
- Palatine bones (2)
- Inferior Nasal Conchae (2)
- the Vomer
There are 6 auditory ossicles involved in hearing which are located in the temporal bones. (3 per ear) They are called’ the malleus, incus and stapes. Other than these bones the mandible is considered the only movable bone of the skull. Sutures are the immovable joints the fuse most of the skull together.
Just For Fun – In the manual healing therapy called Cranial Sacral Therapy the therapist will gently manipulate these cranial joints.
The skull has many surface markings called fissures and foramina that nerves and blood vessels pass through. The cranial bones protect and stabilize the position of the brain, blood vessels, lymphatic vessels and nerves through the attachment of their inner surfaces to meninges (membranes) The outer surface of the cranial bones provide attachment sites for muscles that move the head and face.
The frontal bone forms the forehead, the roofs of the orbits (eye sockets), and most of the anterior part of the cranial floor. Soon after birth the left and right sides of the frontal bone are joined by the metopic suture which usually disappears between 6 and 8 years old.
The two parietal bones form the greater portion of the sides and roof of the cranial cavity.
The two temporal bones make up the lateral aspects of the cranium and part of the cranial floor. The zygomatic process of the temporal bone and the temporal process of the zygomatic bone form the zygomatic arch. (Many people call this the cheek bone.)
A socket called the mandibular fossa is located on the inferior posterior surface of the zygomatic process of each temporal bone. The mandibular fossa and the articular tubercle articulate with the mandible (lower jawbone) to form the temporomandibular joint (TMJ).
The occipital bone forms the posterior part and majority of the base of the cranium. The foramen magnum is in the inferior part of the bone. The external occipital protuberance (EOP) is the most prominent mid-line projection on the posterior surface of the bone just above the foramen magnum.
The sphenoid bone sits at the middle part of the base of the skull. It articulates with all the other cranial bones and holds them together. Anteriorly it joins with the frontal bone, laterally it joins with the temporal bones and posteriorly with the occipital bone. The sphenoid sits posteriorly and slightly superior to the nasal cavity and forms part of the floor, side walls and rear wall of the orbit. The shape of the sphenoid resembles a butterfly with outstretched wings.
The ethmoid bone is located anterior to the sphenoid and posterior to the nasal bones. It is a major supporting structure of the nasal cavity as it forms the superior portion of the nasal septum and most of the superior sidewalls of the nasal cavity. It also forms the medial wall of the orbits (eye sockets).
Facial Bones (14)
The two nasal bones meet at the mid-line of the face and form the bridge of the nose. The rest of the supporting tissue is cartilage.
The two maxilla unite to form the upper jaw bone. They form part of the floor of the orbits and part of the lateral walls of the nasal cavity as well as most of the hard palate (roof of the mouth).
The two zygomatic bones (cheek bones) form the prominences of the cheeks and part of the lateral wall and floor of each orbit. The temporal process of the zygomatic bone projects posteriorly and articulates with the zygomatic process of the temporal bone to form the zygomatic arch.
The two lacrimal bones are thin and slightly resemble a fingernail. They are the smallest facial bones and forma part of the medial wall of each orbit (eye socket).
Just For Fun The lacrimal bones each contain a vertical grove formed with the maxilla called the lacrimal fossa. It houses the lacrimal sack which gathers tears and passes them in to the nasal cavity. (Its where your tears come from)
The two L-shaped palatine bones form the posterior portion of the hard palate, part of the floor and lateral wall of the nasal cavity as well as a small portion of the floors of the orbits.
Inferior Nasal Conchae
The two inferior nasal conchae, which are inferior to the middle nasal conchae of the ethmoid bone are separate bones, not part of the ethmoid bone. These scroll-like bones form part of the inferior lateral wall of the nasal cavity and project into the nasal cavity. All three pairs of nasal conchae (superior, middle and inferior) increase the surface area of the nasal cavity and help swirl and filter air before it goes to the lungs. Only the superior nasal conchae of the ethmoid bone are involved in the sense of smell.
The vomer is a triangular shaped bone on the floor of the nasal cavity that articulates with the perpendicular plate of the ethmoid bone and inferiorly with both the maxillae and palatine bones along the mid-line. it forms the inferior portion of the nasal septum.
The mandible is the largest and strongest facial bone. It consists of a curved horizontal portion (the body), and two perpendicular portions (the rami). The angle of the mandible is the area where each ramus meets the body. Each ramus has a posterior condylar process that articulates with the mandibular fossa and articular tubercle of the temporal bone to form the temporomandibular joint (TMJ). They also have an anterior coronoid process which the temporalis muscle attaches to. There is a depression between the coronoid and condylar processes called the mandibular notch. The alveolar process is an arch containing alveoli (sockets) for the mandibular (lower) teeth. The mandible also contains a mental foramen on both sides. This is near where your dentist reach the mental nerve when injecting anesthetics. Another foramen associated with the mandible is the mandibular foramen on the medial surface of each ramus which is another site often used by dentists to inject anesthetics.
Hyoid Bone (1)
The only bone in the body which does not have a joint. Many people consider this bone to be the human wishbone.
The number of vertebrae in early childhood is 33. As a child grows several vertebrae in the sacral region and coccygeal region fuse. The adult vertebral column contains 26 vertebrae:
Cervical (7) (cervic = neck)
Thoracic (12) (thorax = chest)
Lumbar (5) (lumb = loin)
Sacrum (1) – Consists of 5 sacral vertebrae (SA-KRUM = sacred bone)
Coccyx (1) – Consists of 4 fused coccygeal vertebrae (pron. KOK-siks = cuckoo, because the shape resembles the bill of a cuckoo bird)
While there are distinct differences between the vertebrae from different regions of the vertebral column these are the most common parts of a typical vertebra:
- Vertebral Foramen
- Transverse Process
- Spinous Process
- Transverse Foramen
- Superior articular facet
- Superior demifacet
- Inferior demifacet
- Superior vertebral notch
- Inferior vertebral notch
- Facet for articular part of tubercle of rib
Sternum (breastbone) – the flat narrow bone located in the center of the anterior thoracic wall. There are three parts to the sternum that usually fuse by age 25:
manubrium (ma-NOO-bre-um = hand-like)
body (largest portion)
xiphoid process (ZI-foyd = sword-shaped)
The junction of the manubrium and the body form the sternal angle.
The depression on the superior surface called the suprasternal notch. Lateral to the suprasternal notch are the clavicular notches that articulate with the medial ends of the clavicles to form the sternoclavicular joints. The manubrium also articulates with the costal cartilage of the first rib and part of the second rib.
The body of the sternum articulates directly or indirectly with the costal cartilages of part of the second rib and ribs 3 – 10.
The xiphoid process consists of hyaline cartilage during infancy and doesn’t completely ossify until about age 40. The xiphoid process provides attachment for some abdominal muscles.
There are 12 pairs of ribs numbered 1 to 12 that increase in length from the 1st through 7th and decrease in length to the 12th rib. Each rib articulates posteriorly with it’s corresponding vertebra.
The 1st through 7th ribs have a direct anterior attachment with the sternum by a strip of hyaline cartilage (costal cartilage). These ribs are called true ribs. The remaining five ribs are called false ribs because their costal cartilages attach either indirectly to the sternum or not at all. The cartilages of the 8th – 10th ribs attach to each other and then to the cartilages of the 7th ribs. The 11th and 12th ribs are considered floating ribs because their costal cartilage does not attach to the sternum. They only attach posteriorly to the thoracic vertebrae.
Pectoral (Shoulder) Girdle
There are two pectoral girdles that attach the bones of the limbs to the axial skeleton via the clavicles and scapulas. The pectoral girdles are held in position and stabilized by a large group of muscles and do not articulate with the vertebral column.
Clavicle/collar bone (2)
The clavicle is S-shaped because the medial half is convex and the lateral half is concave anteriorly. In males it is more curved. The medial end articulates with the manubrium and forms the sternoclavicular joint. The other, lateral end is broad and flat. It articulates with the acromion of the scapula and forms the acromioclavicular joint.
Scapula/shoulder blade (2)
The scapula is a large, triangular flat bone that sits between the levels of the 2nd and 7th ribs posteriorly. A prominent ridge called the spine runs diagonally across the posterior surface of the scapula. Both superior and inferior to the spine of the scapula are two fossae: The supraspinous fossa and the infraspinous fossa. The supraspinous fossa is an attachment site for the supraspinatus muscle of the shoulder. The infraspinous fossa serves as an attachment site for the infraspinatus muscle of the shoulder. The lateral end of the spine projects as a flattened, expanded process called the acromion. Inferior to the acromion is a shallow depression, the glenoid cavity that accepts the head of the humerus to form the glenohumeral joint.
The thin edge of the scapula closer to the vertebral column is called the medial (vertebral) border. The thick edge of the scapula closer to the arm is called the lateral (axillary) border. The medial and lateral borders join at the inferior angle. The scapular notch is a prominent indentation along the superior border that the suprascapular nerve passes through.
At the lateral end of the superior border is a projection of the anterior surface called the coracoid process. Various tendons of muscles (pectoralis minor, coracobrachialis and biceps brachii) as well as ligaments (coracoacromial, conoid and trapezoid) attach here. On the anterior surface of the scapula is a slightly hollowed out area called the subscapular fossa. This surface provides an area of attachment for the subscapularis muscle.
The humerus is the longest bone of the upper limb and articulates proximally with the scapula and distally at the elbow with two bones, the ulna and the radius.
The proximal end of the humerus has a rounded head that articulates with the glenoid cavity of the scapula to form the glenohumeral joint (GH joint). Distal to the head is the anatomical neck which is visible as an oblique groove. The greater tubercle is a lateral projection distal to the anatomical neck. It is the most laterally palpable bony landmark of the shoulder region. The lesser tubercle projects anteriorly. Between the two tubercles is a groove named the intertubercular sulcus (bicipital groove). The surgical neck is a constriction in the humerus just distal to the tubercles where the head tapers to the shaft.
The shaft (body) of the humerus is somewhat cylindrical shaped at the proximal end and gradually becomes triangular until it becomes broad and flattened at its distal end. Laterally at the middle portion of the shaft is a roughened V-shaped area called the deltoid tuberosity. This area is a point of attachment for the tendons of the deltoid muscle.
There are several prominent features at the distal end of the humerus. The capitulum is a rounded knob at the lateral aspect of the bone that articulates with the head of the radius. The radial fossa is an anterior depression above the capitulum that articulates with the head of the radius when the forearm is flexed (bent). The trochlea is medial to the capitulum and is a spool-shaped surface that articulates with the ulna. The coronoid fossa is an anterior depression that receives the coronoid process of the ulna when the forearm is flexed. The olecranon fossa is a large posterior depression that receives the olecranon on the ulna when the forearm is extended. The medial and lateral epicondyles are roughened projections on either side of the distal end of the humerus that the tendons of most muscles or the forearm attach to.
The ulna is on the medial side of the forearm and is longer than the radius. AT the proximal end of the ulna is the olecranon which forms the prominence of the elbow. With the olecranon, an anterior projection called the coronoid process articulates with the trochlea of the humerus. The trochlear notch is a large curved area between the olecranon and coronoid process that forms part of the elbow joint. Lateral and inferior to the trochlear notch is a depression called the radial notch which articulates with the head of the radius. Just inferior to the coronoid process is the ulnar tuberosity which is an attachment site for the biceps brachii muscle. The distal end of the ulna consists of the head that is separated from the wrist by a disc of fibrocartilage. A styloid process is located on the posterior side of the ulna’s distal end. It provides an attachment site for the ulnar collateral ligament.
The radius is the smaller forearm bone located on the lateral aspect (thumb side) of the forearm. It is narrow at its proximal end and widens at its distal end. The proximal end of the radius has a disc-shaped head that articulates with the capitulum of the humerus and the radial notch of the ulna. Inferior to the head is the constricted neck which is a roughened area inferior to the neck on the medial side, called the radial tuberosity. This is an attachment site for the tendons of the biceps brachii muscle. The shaft of the radius widens distally to form a styloid process on the lateral side. The styloid process provides attachment for the brachioradialis muscle as well as the radial collateral ligament to the wrist.
The ulna and radius articulate with the humerus at the elbow joint. The articulation occurs both where the head of the radius articulates with the capitulum of the humerus, and where the trochlear notch of the ulna articulates with the trochlea of the humerus.
The ulna and the radius connect with one another at three sites: A broad flat connective tissue called the interosseous membrane joins the shafts of the two bones. This membrane also provides a site of attachment for some tendons of deep skeletal muscles of the forearm. The ulna and radius articulate proximally where the head of the radius articulates with the ulna’s radial notch. This is called the proximal radioulnar joint. Distally the head of the ulna articulates with the ulnar notch of the radius. This is called the distal radioulnar joint. The distal end of the radius also articulates with three bones of the wrist: the lunate, scaphoid and triquetrum to form the radiocarpal (wrist) joint.
Each wrist has 8 small bones called carpals. Articulations among the carpals are called intercarpal joints. they are arranged in two rows of 4 bones each. Their names reflect their shapes.
Just for Fun – Beginning proximally from lateral to medial a good mnemonic for remembering the names of the bones is: Some Lovers Try Positions That They Can’t Handle.
The first letter of the carpal bones from lateral to medial corresponds to the first letter of each word in the mnemonic.
The anterior concave space formed by the pisiform and the hamate (on the ulnar side) and the scaphoid and trapezium (on the radial side), with the roof-like covering of the flexor retinaculum is the carpal tunnel. The long flexor tendons of the digits & thumb and the median nerve pass through the carpal tunnel. Carpal Tunnel Syndrome happens when these tendons become enflamed causing pressure on the median nerve.
The metacarpal bones are numbered 1 -5 starting with the thumb. Each metacarpal has a base, body and head. The bases articulate with the distal row of carpal bones to form the carpometacarpal joints. The heads of the carpal bones are what people commonly refer to as knuckles.
Phalanges are bones of the digits (fingers). There are 14 phalanges in each hand and are also numbered 1 -5 starting from the thumb. A single bone of a digit is called a phalanx. Each phalanx consists of a proximal base, an intermediate shaft and a distal head. The thumb (pollex) has two phalanges while the other four digits have three. There is no middle phalange in the thumb. Joints between the phalanges are called interphalangeal joints.
Proximal Phalanges – First row of phalanges articulate with the metacarpal bones and second row of phalanges.
Middle Phalanges – The second row of phalanges, (middle row) articulates with the proximal row and the distal row (3rd row). The thumb has no middle phalanx.
Distal Phalanges – The third row articulate with the second row with the exception of the thumb. Because it has no middle phalanx.
Sesamoid bones – Develop in certain tendons where there is considerable friction, tension and physical stress such as the palms and soles. The vary in location and number from person to person, are not always completely ossified and are typically only a few mms in diameter. The patellae are the two exception to the rule. An explanation of this is below under the patella heading. Sesamoid bones protect tendons from excessive wear and tear. They often change the direction of pull of a tendon which improves the mechanical advantage at a joint.
Pelvic (hip) Girdle
The pelvic girdle consists of the two hip bones aka coxal, pelvic bones or os coxa. The hip bones unite anteriorly at a joint called the pubic symphysis. Posteriorly they unite with the sacrum at the sacroiliac joints. (SI joints) This formation is known as the bony pelvis. The bony pelvis provides the stable support for the vertebral column and pelvic and lower abdominal organs. It also connects the bones of the lower limbs to the axial skeleton.
a couple important differences in the pelvic girdle and pectoral (shoulder) girdle is that the pelvic girdle offers more strength than mobility where as the pectoral girdle offers more mobility than strength. One of the main reasons for this is that the the sockets (glenoid fossae) in the pectoral girdle aren’t as deep as the sockets (acetabula) of the pelvic girdle.
Each of the two hip bones actually consist of 3 bones separated by cartilage at birth which fuse. They are; the ilium which is the most superior, an inferior and anterior pubis as well as an inferior and posterior ischium. These bones fuse together by approximately 23 yrs.
The ilium is the largest of the 3 bones and is composed of a superior ala (wing) and an inferior body. The body helps for the acetabulum which is the socket for the femur. The superior border of the ilium is the iliac crest which ends anteriorly at the anterior superior iliac spine (ASIS). Posteriorly The iliac crest ends in a sharp posterior superior iliac spine. These spines serve as attachment points for the tendons of muscles of the trunk, hip and thighs.
The medial surface of the ilium contains the iliac fossa, a concavity where the tendons of the iliac muscle attaches. Posterior to this fossa are the iliac tuberosity which is an attachment point for the sacroiliac ligament. Three other markings of the ilium are three arched lines on its lateral surface called the posterior gluteal line, anterior gluteal line and inferior gluteal line. The gluteal muscles attach to the ilium between these lines.
The ischium is the inferior, posterior portion of the hip bone and is comprised of a superior body and inferior ramus. The ramus is the portion of the ischium that fuses with the pubis. The ischium has an ischial spine, a lesser sciatic notch below its spine and a rough thickened area called the ischial tuberosity. Some people refer to the ischial tuberosity as the ‘sits bones.
Together the pubis and ischium form the obturator foramen which is the largest foramen of the skeleton.
Pubis (Pubic Bone)
The pubis is the anterior and inferior part of the hip bone. It has a superior ramus, inferior ramus and a body. The anterior superior border of the body is the pubic crest. At its lateral end is a projection called the pubic tubercle.
The pubic symphysis is the joint between the pubes of the two hip bones. It consists of a disc of fibrocartilage. Inferior to this joint the two inferior rami of the two pubic bones meet to for the pubic arch.
The acetabulum is a deep fossa formed by the ilium, ischium and pubis and functions as the socket for the head of the femur. The acetabulum and femoral head form the hip (coxal) joint/acetabulofemoral joint. On the inferior side of the acetabulum is the acetabular notch which is a deep indentation that forms a foramen that nerves and blood vessels pass through and also serves as an attachment point for ligaments of the femur.
The lower limbs have 60 bones in total:
- Femur (2)
- Patella (knee cap)(2)
- Tibia (2)
- Fibula (2)
- Tarsals (14)
- Metatarsals (10)
- Phalanges (28)
Femur (thigh bone)
The Femur is the longest, heaviest and strongest bone in the human body. Proximally it articulates with the acetabulum of the hip bone. Distally it articulates with the patella and tibia. The body (shaft) of the femur angles medially. The angle in females is greater because the female pelvis is broader.
The proximal end of the femur contains a rounded head that articulates with the acetabulum to form toe hip (coxal) joint. The head contains a small centered depression called the fovea capitis which is a connection point for the ligament of the head of the femur which connects the femur to the acetabulum of the hip bone. The neck of the femur is a constricted region distal to the head. The greater trochanter and lesser trochanter are projections from the neck that serve as attachment sites for the tendons of some of the thigh and buttock muscles. A ridge called the intertrochanteric crest forms between the posterior surfaces of the trochanters.
Inferior to the intertrochanteric crest is a vertical ridge called the gluteal tuberosity. This blends with another ridge called linea aspera. Both of these ridges serves as attachment points for the tendons of several thigh muscles.
The distal end of the femur includes the medial condyle and the lateral condyle. These articulate with the medial and lateral condyles of the tibea. Superior to the condyles are the medial and lateral epiconyles to whihc the ligaments of the knee joint attach. A depression on the posterior surface is called the intercondylar fossa. The patellar surface is located between the condyles on the anterior surface.
Patella (knee cap)
The patella is a sesamoid bone located on the anterior surface of the knee joint. The base (proximal end) of the patella develops in the tendon of the quadriceps femoris muscle. The distal end of the patella is known as the apex. The posterior surface of the patella contains to articular facets; one for the medial condyle and one for the lateral condyle of the femur. The patellar ligament attaches the patella to the patella to the tibial tuberosity.
The patellofemoral joint is between the posterior surface of the patella and the patellar surface of the femur. The patella increases the leverage of the tendon of the quadriceps femoris muscle, protects the knee joint and maintains the position of the tendon when the knee is bent.
Tibia (shin bone)
Just for Fun – The term tibia means flute, as the tibial bones of birds were used n ancient times to make musical instruments.
The tibia articulates at its proximal end with the femur and fibula. At its distal end it articulates with the fibula and the talus bone of the ankle. The tibia and fibula, like the ulna and radius are connected by an interosseous membrane.
The proximal end of the tibia expands into a lateral and medial condyle which articulate with the condyles of the femur to form the lateral and medial tibiofemoral (knee) joint. The inferior surface of the lateral condyle articulates with the head of the fibula. The slightly concave condyles are separated by an upward projection called the intercondylar eminence.
The medial surface of the distal end of the tibia forms the medial malleolus. The medial malleolus articulate with the talus and can be be felt as the prominence on the medial surface of the ankle. The fibular notch articulates with the distal end of the fibula to form the distal tibiofibular joint.
Just for fun – The tibia is the most fractured long bone of the body and most frequent site of open compound fractures.
The fibula is lateral and parallel to the tibia but smaller. The fibula does not articulate with the femur but helps stabilize the ankle joint. The head of the fibula (proximal end) articulates with the inferior surface of the lateral condyle of the tibia to form the proximal tibiofibular joint. The distal end of the fibula is arrow-head shaped and has a projection called the lateral malleolus which articulates with the talus. This forms the prominence on the lateral surface of the ankle. As previously mentioned, the fibula articulates with the tibia at the fibular notch to form the distal tibiofibular joint.
Just for Fun – A good way to distinguish the location of the two bones is to remember that the tibia is on the same side as your great (big) toe and the name tibia starts with the the letter ‘T’ as does the word toe. Your great toe is your biggest toe and the tibia is larger than your fibula.
Tarsals, Metatarsals and Phalanges
The tarsus (ankle) consists of seven bones called tarsals
- Cuneiform bones (3) – 1st (medial) cuneiform, 2nd (intermediate) cuneiform, 3rd (lateral) cuneiform
The talus is the most superior tarsal bone and is the only bone in the foot to articulate with the tibia and fibula. These articulations are called the talocrural (ankle) joint. When walking the talus transmits about half the weight of the body to the calcaneus. The rest of the weight is transmitted to the other tarsals. The calcaneus is the largest and strongest tarsal bone.
Just for Fun – A good way to remember that carpals are in your wrist and tarsals are in your ankle is to remember that tarsals starts with the letter ‘T’ and you have toes on your feet. The word toes also starts with the letter ‘T’.
The metatarsus is the intermediate region of the foot and has five metatarsal bones number 1 – 2 from medial to lateral position. Similar to the metacarpals of the palm of the hand each metatarsal has a proximal base, intermediate shaft and distal head. The metatarsals articulate proximally with the first second and third cuneiform bones and with the cuboid bone to form the tarsometatarsal joints. Distally they articulate with the proximal row of phalanges to form the metatarsophalangeal joints. The first meta tarsal is thicker than the others because it bears more weight.
Arches of the Foot
The bones of the foot create two arches that held in position by ligaments and tendons which enable the foot to support the weight of the body, properly distribute the body weight over the foot and provide leverage while walking. Healthy arches should yield when as weight is applied and spring back when the weight is lifted, thus storing energy for the next step and absorb shock. The arches are usually fully developed by 12 or 13 years.
The longitudinal arch has two parts which consist of tarsal and metatarsal bones arranged to form an arch from the anterior to posterior of the foot. The medial portion of the arch is so high that the medial portion of the foot between the ball and the heel doesn’t touch the ground when walking on a hard surface.
The transverse arch is found between the medial and lateral aspects of the foot and is formed by the navicular, three cuneiforms and the bases of the five metatarsals.
Just for Fun – Normally the balls of the feet carry about 40% of the weight and the heel carries about 60%. When a person wears high-heeled shoes the distribution of weight changes so that the balls of the feet are damaged, joint pain develops and structural changes in a person’s body may occur.