I



Chapter 8 The Skeletal System

Note: there is more detail in the notes than will be examined. It is here to provide context for some of the concepts. For example, articulations are included in this section as a preliminary look at concepts of Chapter 9.

1 Overview of the skeleton

1 Axial skeleton

80 bones in total, these bones lie around the longitudinal axis of the body.

Consist of the skull, hyoid and auditory ossicles, vertebral column and thorax.

2 Appendicular skeleton

126 bones in total, consists of the upper and lower limbs plus the bones forming the pelvic and pectoral girdles.

3 Bones of the skeletal system

The adult human has 206 bones. Most of these are paired, one member of each pair on either side of the body. Children have more than 206 because sets of bones fuse together with age.

4 Surface features of bones

The bone surface markings are structures adapted for specific functions. Most develop due to the activity of tendons, ligaments, aponeuroses and fasciae.

1 Articulations

1 Condyle

Large, round protuberance at the end of a bone e.g. lateral condyle of femur.

2 Facet

Smooth, flat articular surface e.g. superior articular facet of a vertebra.

3 Head

Rounded articular projection supported on the neck of a bone e.g. head of the femur.

2 Extensions and projections

1 Crest

Prominent ridge or elongated projection e.g. iliac crest of hip bone.

2 Epicondyle

Projection above a condyle e.g. medial epicondyle of the femur.

3 Line

Long, narrow ridge or border, smaller than crest e.g. linea aspera of the femur.

4 Process

Sharp, slender projection e.g. spinous process of vertebrae.

5 Protuberance

Bony outgrowth or protruding part e.g. mental protuberance of chin.

6 Spine

Sharp, slender, or narrow process e.g. spine of the scapula.

7 Trochanter

Very large projection e.g. greater trochanter of the femur.

8 Tubercle

Small, rounded projection e.g. greater tubercle of the femur.

9 Tuberosity

Large, rounded, usually roughened projection e.g. ischial tuberosity of the hip bone.

3 Depressions

1 Alveolus

A pit or socket e.g. tooth socket.

2 Fossa

Shallow depression e.g. mandibular fossa.

3 Fovea

A small pit e.g. fovea capitis of the femur.

4 Sulcus

Furrow along the surface of a bone that fits a blood vessel, nerve or tendon e.g. intertubercular sulcus of the humerus.

4 Passages

1 Canal

A tubular passage or tunnel through a bone e.g. condylar canal of the skull.

2 Fissure

A slit through a bone e.g. orbital fissure behind the eye.

3 Foramen

A hole through a bone e.g. foramen magnum of occipital bone.

4 Meatus

An opening into a canal e.g. acoustic meatus of the ear.

2 The skull

1 Sutures

Sutures are immovable joints of the cranial bones

2 Cavities

The skull contains several prominent cavities.

1 Cranial cavity

The largest cavity of the skull which encloses the brain.

2 Orbits

Eye sockets.

3 Nasal cavity

4 Buccal cavity

Mouth.

5 Middle and inner ear cavities

6 Paranasal sinuses

Theses cavities are named after the bones in which they occur and are connected with the nasal cavity.

1 Frontal sinuses

2 Sphenoid sinuses

3 Ethmoid sinuses

4 Maxillary sinuses

3 Foramina

Bones of the skull have some obvious holes (foramina, singular foramen). Some of these will be mentioned below.

4 Cranial bones

1 Foramen magnum

The big hole through which the spinal cord travels through the skull.

2 Fossae

The base of the skull is divided into three major basins: the anterior, middle and posterior cranial fossae.

3 Frontal bone

Single bone forms the forehead, the roofs of the orbits, and most of the anterior part of the cranial floor (upon which sits the brain).

1 Supraorbital margin

The frontal bone extends posteriorly from this margin to form the roof of the orbits, which also forms part of the cranial floor.

2 Supraorbital foramen

A hole in the supraorbital foramen.

3 Frontal sinuses

A pair of paranasal sinuses.

4 Parietal bones

The two parietal bones form the sides and roof of the cranial cavity.

5 Temporal bones

The two temporal bones form the inferior lateral aspects of the cranium and part of the cranial floor. Each temporal bone can be described by dividing it into four parts.

1 The squamous part

The thin, flat portion of the temporal bone. Has two prominent features.

1 Zygomatic process

The zygomatic process projects from the inferior portion of the temporal squama. The zygomatic process of the temporal bone articulates with the zygomatic bone of the face.

1 Zygomatic arch

The zygomatic process and zygomatic bone form the zygomatic arch.

2 Mandibular fossa

Located on the inferior posterior surface of the zygomatic process.

2 The tympanic part

Small ring of bone bordering the external acoustic meatus.

1 External acoustic meatus

The external acoustic meatus directs sound waves into the ear.

2 Styloid process

Projects inferiorly from the inferior surface of the temporal bone and is the point of attachment for muscles and ligaments of the tongue and neck.

3 The mastoid part

This part of the temporal bone is located posterior and inferior to the external auditory meatus.

1 Mastoid process

This is a rounded projection of the mastoid portion of the temporal bone and is the point of attachment for several neck muscles.

4 The petrous part

This is the part of the cranial floor formed by the temporal bone.

1 Internal acoustic meatus

Passageway for the vestibulocochlear nerve.

6 Occipital bone

The single occipital bone forms the posterior part and most of the base of the cranium.

1 Foramen magnum

Located in the inferior part of the bone. The medulla oblongata of the brain connects with the spinal cord within this foramen.

1 Occipital condyles

These oval processes with convex surfaces on either side of the foramen magnum articulate with the first cervical vertebrae (the atlas).

2 External occipital protuberance

The bump on the back of the head. This is a prominent midline projection just above the foramen magnum.

1 Nuchal ligament

This is the large fibrous elastic ligament that extends from the external occipital protuberance to the 7th cervical vertebrae to help support the head.

2 Superior and inferior nuchal lines

These are two curved ridges extending laterally from the external occipital protuberance and provide attachment areas for muscles.

7 Sphenoid bone

This single bone lies in the middle part of the base of the skull. It plays a key role in the base of the skull because it articulates with all of the other cranial bones, holding them together.

It is shaped like a "bat with outstretched wings".

1 Sphenoid sinuses

2 Sella turcica

A bony saddle-shaped structure on the superior surface of the body of the sphenoid bone.

1 Hypophyseal fossa

A depression within the sella turcica that contains the pituitary gland.

3 Optical foramen

Between the body and part of the sphenoid wing on both sides is the optical foramen through which pass the optical nerve and ophthalmic artery.

8 Ethmoid bone

A single bone located in the midline in the anterior part of the cranial floor medial to the orbits. It forms (1) part of the anterior portion of the cranial floor, (2) the medial wall of the orbits, (3) the superior portion of the nasal septum and (4) most of the superior sidewalls of the nasal cavity.

1 Olfactory foramina

The holes through which the olfactory nerves pass.

2 Ethmoid sinuses

The ethmoid bone contains between 3 and 18 air spaces or cells. The ethmoid cells together form the ethmoid sinuses.

5 Facial bones

1 Maxillae

A pair of bones forming the upper jawbone. They articulate with every bone of the face except the mandible.

The mandible forms: (1) part of the floors of the orbits (2) part of the lateral walls and floor of the nasal cavity (3) most of the hard palate.

1 Hard palate

The hard palate is the bony roof of the mouth and is formed in part by the palatine bones.

2 Maxillary sinus

Each maxilla contains a large maxillary sinus.

3 Alveolar process

The alveolar process is the arch of each maxilla that contains the alveoli for the maxillary teeth.

1 Alveoli

Alveoli are the tooth sockets. (the small cavities of respiratory tissue in the lungs are also called alveoli).

4 Infraorbital foramen

A opening in each maxilla inferior to the orbit that allows the passage of the infraorbital nerve and blood vessels and branch of the trigeminal nerve.

2 Palatine bones

Two palatine bones form the posterior portion of the hard palate.

3 Zygomatic bones

Two zygomatic bones form the cheekbones. They form the prominences of the cheeks and part of the lateral wall and floor of each orbit.

Confusingly, the temporal process of the zygomatic bone articulates with the zygomatic process of the temporal bone to form the zygomatic arch.

4 Lacrimal bones

Think of teardrops.

The pair of lacrimal bones form part of the medial wall of the orbits and house the lacrimal sac, which gathers tears and passes them to the nasal cavity.

5 Nasal bones

A pair of bones forming part of the bridge of the nose.

6 Inferior nasal conchae

These two bones form part of the inferior lateral wall of the nasal cavity.

7 Vomer

A single small bone on the floor of the nasal cavity. Forms part of the nasal septum.

8 Mandible

The lower jawbone is the largest, strongest facial bone and the only movable skull bone (other than the auditory ossicles).

1 Body

The curved horizontal portion of the mandible is the body.

1 Alveolar process

The alveolar process contains the alveoli for the mandibular teeth.

2 Ramus

The mandible has two rami, which are perpendicular to the body.

1 Condylar process

Each ramus has a posterior condylar process that articulates with the mandibular fossa and articular tubercle of the temporal bone.

2 Temporomandibular joint (TMJ)

The joint formed between the mandible and temporal bone.

3 Coronoid process

The coronoid process of each ramus is anterior to the TMJ and is where the temporalis muscle attaches.

3 Angle of the mandible

Where the body and each ramus meet.

6 Bones associated with the skull

1 Auditory ossicles

The three tiny bones in the middle ear.

2 Hyoid bone

U-shaped bone that does not articulate with any other bone. Located in the anterior neck between the mandible and larynx. It supports the tongue, provides attachment points for tongue muscles and muscles of the neck.

7 The skull in infancy and childhood

1 Fontanels

"Soft spots" between the cranial bones of the newborn. They are areas of unossified mesenchyme. They are eventually replaced by bone.

3 The vertebral column and thoracic cage

1 General features of the vertebral column

Composed of vertebrae. The vertebral column, sternum and ribs form the skeleton of the trunk of the body.

It surrounds and protects the spinal cord.

It also supports the head and serves as an attachment for the ribs, pelvic girdle and muscles of the back.

1 Divisions of the vertebral column

Note: these numbers correspond with the final number of bones following complete ossification.

1 7 Cervical vertebrae

2 12 Thoracic vertebrae

3 5 Lumbar vertebrae

4 1 Sacrum

5 1 Coccyx

2 Normal curves of the vertebral column

The curves of the vertebral column increase its strength, help maintain balance in the upright position, absorb shocks and help protect vertebrae from fractures.

1 Cervical curve

Relative to the front of the body, the cervical curve is convex.

2 Thoracic curve

Concave

3 Lumbar curve

Convex

4 Pelvic or sacral curve

Concave.

2 General structure of a vertebrae

1 Body

Thick, disc-shaped anterior portion. This is the weight-bearing part of the vertebra.

2 Vertebral arch

The vertebral arch extends posteriorly from the vertebral body. The vertebral arch and vertebral body surround the spinal cord.

1 Vertebral foramen

The opening formed by the vertebral arch and body.

1 Vertebral canal

The collective passageway formed by the vertebral foramina that houses the spinal cord is called the vertebral canal.

3 Processes

Seven processes arise from the vertebral arch.

1 2 Transverse processes

Project laterally.

2 1 Spinous process

Projects posteriorly.

The spinous and lateral processes provide attachment points for muscles

3 2 Superior articular processes

4 2 Inferior articular processes

The superior and inferior articular processes form the articulation between adjacent vertebra.

3 Intervertebral discs

Found between the bodies of adjacent vertebrae. The discs form strong joints, permit various movements and absorb vertical shocks.

1 Annulus fibrosus

The fibrous outer ring of tissue.

2 Nucleus pulposus

The soft, pulpy, highly elastic substance inside of the annulus.

4 Regional characteristics of vertebrae

1 Cervical vertebrae

C1-C7. These are the smallest vertebrae. They have the largest vertebral foramen: the cervical region of the spinal cord has the greatest diameter.

1 Atlas

C1. Lacks a vertebral body and spinous process. Supports the skull by articulating with the occipital bone. Allows the nodding "yes" movement.

2 Axis

C2. Has a vertebral body. Allows the side-to-side "no" movement.

2 Thoracic vertebrae

T1-T12. Larger and stronger than cervical vertebrae. Articulate with the ribs.

3 Lumbar vertebrae

L1-L5. Largest and strongest vertebrae.

4 Sacrum

Forms by the union of 5 sacral vertebrae. Begin fusion at age 16-18 years and completely fused by 30. Provides a strong foundation for the pelvis.

5 Coccyx

Triangle-shaped like the sacrum. Formed by the fusion of 4 coccygeal vertebrae. Fuse later than the sacrum.

4 The thoracic cage

Thorax refers to the entire chest. The skeletal portion of the thorax is called the thoracic cage. and is an enclosure formed by the sternum, costal cartilages, ribs and the bodies fo the thoracic vertebrae.

The thoracic cage encloses and protects the organs of the thoracic and superior abdominal cavities and provides support for the bones of the shoulder girdle and upper limbs.

1 Sternum

1 Manubrium

The superior part of the sternum. The manubrium articulates with the clavicles and the costal cartilages of the first and second ribs.

2 Body

The sternal body articulates directly or indirectly with the second through tenth ribs.

3 Xyphoid process

Does not completely ossify until the age of about 40 years. Provides attachment point for some abdominal muscles.

2 Ribs

Twelve pairs. Each rib articulates posteriorly with its corresponding thoracic vertebra.

1 Costal cartilages

The first through seventh pair of ribs have a direct attachment to the sternum via costal cartilage.

2 True ribs

The ribs that have costal cartilages and attach directly to the sternum are called true ribs.

3 False ribs

The remaining 5 pairs of ribs are false ribs because their costal cartilages either attach indirectly to the sternum or do not attach to the sternum at all.

4 Floating ribs

The 11th and 12th ribs are false ribs that are also considered floating ribs because their anterior ends do not attach to the sternum at all.

5 The pectoral girdle and upper limb

1 Pectoral girdle

Two pectoral shoulder girdles that attach bones of the upper limbs to the axial skeleton. Each pectoral girdle consists of a clavicle and a scapula. the pectoral girdles do not articulate with the vertebral column and are held in place by muscles.

1 Clavicle

The anterior bone of the pectoral girdle, superior to the first rib.

1 Articulation

1 Sternoclavicular joint

The clavicle articulates with the manubrium of the sternum at the sternal end.

2 Acromioclavicular joint

The clavicle articulates with the acromion of the scapula at the acromial end.

2 Scapula

The posterior bone of the pectoral girdle. It is situated between the levels of the second and seventh ribs.

1 Articulation

1 Acromioclavicular joint

The scapula articulates with the clavicle.

2 Glenohumeral (shoulder) joint

The scapula articulates with the humerus.

2 Parts of the scapula

1 Spine

The spine is a prominent ridge that runs diagonally across the posterior surface of the body.

2 Body

The flattened, triangular part of the scapula.

3 Acromion

The lateral end of the spine projects a flattened, expanded process called the acromion. It is the palpable high point of the shoulder.

4 Glenoid cavity

Inferior to the acromion is the glenoid cavity, which accepts the head of the humerus at the glenohumeral joint.

5 Coracoid process

Several muscles of the shoulder attach to the process on the lateral end of the superior border of the scapula, which projects anteriorly

2 Upper Limb

Each upper limb has 30 bones in four regions: 1 humerus in the arm (brachium); the radius and ulna in the forearm (antebrachium); 8 carpals of the carpus or wrist (carpus); and in the hand (manus) 5 metacarpals of the metacarpus or palm, and 14 phalanges of the digits.

1 Humerus

The largest and longest bone of the upper limb. Articulates proximally with the scapula and distally with the ulna and radius.

1 Articulation

1 Glenohumeral joint

The articulation of the proximal end of the humerus with the scapula.

2 Humeroulnar joint

The articulation of the distal end of the humerus with the ulna.

3 Humeroradial joint

The articulation of the distal end of the humerus with the radius.

2 Parts of the humerus

1 Proximal end

1 Head

The rounded structure that articulates with the glenoid cavity of the scapula to form the glenohumeral joint.

2 Anatomical neck

An oblique groove forming the margin of the head.

3 Greater tubercle

The lateral projection distal to the anatomical neck. It is the most lateral projection distal to the anatomical neck.

4 Surgical neck

The constriction of the humerus just distal to the tubercles where the head tapers to the shaft. This is where the humerus often fracture.

2 Body

The shaft of the humerus.

3 Distal end

1 Capitulum

The rounded knob on the lateral aspect of the humerus that articulates with the head of the radius.

2 Trochlea

Located medial to the capitulum, the trochlea articulates with the ulna.

3 Medial epicondyle

Medial projection to which tendons of the forearm attach.

4 Lateral epicondyle

Lateral projection to which tendons of the forearm attach.

2 Ulna and Radius

1 Articulations

1 Elbow joint

The radius and ulna articulate with the humerus at the elbow joint. The articulation occurs at two places: 1. the head of the radius articulates with the capitulum of the humerus; 2. the trochlear notch of the ulna receives the trochlea of the humerus.

2 Articulation between radius and ulna

1 Interosseus membrane

A broad, flat fibrous connective tissue joins the shafts of the radius and ulna.

2 Proximal radioulnar joint

The head of the radius articulates with the ulna's radial notch at the proximal end.

3 Distal radioulnar joint

The head of the ulna articulates with the ulnar notch of the radius at the distal end.

3 Radiocarpal (wrist) joint

The distal end of the radius articulates with three bones of the wrist: the lunate, the scaphoid, and the triquetrum.

2 Ulna

The medial aspect (little finger side) or the forearm. The ulna is longer than the radius.

1 Olecranon

Proximal end, the olecranon forms the prominence of the elbow.

2 Coronoid process

Receives the trochlea of the humerus.

3 Head of the ulna

The head is at the distal end of the ulna

3 Radius

Located on the lateral aspect (thumb side) of the forearm.

1 Head of the radius

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.

2 Neck of the radius

Inferior to the head is a constricted region called the neck.

3 Carpal bones

The proximal region of the hand and consists of 8 carpals. The carpals are joined together by ligaments. They are arranged in two rows of 4 bones, proximal and distal. The names of the individual carpal bones are here for your interest only.

1 Intercarpal joints

The articulations between the carpal bones.

2 Proximal row, from lateral to medial

1 Scaphoid

In carpal fractures, this is the most likely bone broken as it takes the full force of a fall on an outstretched hand.

2 Lunate

3 Triquetrum

4 Pisiform

3 Distal row, lateral to medial

1 Trapezium

2 Trapezoid

3 Capitate

The largest carpal bone.

4 Hamate

4 Metacarpal bones

The palm of the hand, consists of 5 bones.

1 Metacarpals

1 Base, shaft and head

Each metacarpal consists of a proximal base, intermediate shaft and distal head.

2 Numbered I to V, lateral to medial

The thumb is numbered I.

2 Carpometacarpal joints

The articulation between the bases of the metacarpals and the distal row of carpals.

3 Metacarpophalangeal joints

The heads of the carpals articulate with the proximal phalanges.

5 Phalanges

The bones of the digits make up the distal part of the hand. There are 14 phalanges in 5 digits.

1 Numbered I to V, lateral to medial

Like the metacarpals, the thumb is I.

2 Phalanx

A single bone of a digit is called a phalanx.

3 Pollex

The thumb. It has 2 phalanges, a proximal and a distal...no middle phalanx.

4 14 phalanges

Three phalanges in each of the four digits. The thumb has two.

1 Proximal row

Articulate with the metacarpal bones and middle row of phalanges.

2 Middle row

Articulates with the proximal and distal row of phalanges.

3 Distal row

5 Base, shaft and head

Each phalanx consists of a proximal base, intermediate shaft, and distal head.

6 Interphalangeal joints

The joints between the phalanges.

6 The pelvic girdle and lower limb

1 Pelvic girdle

1 Coxal bones or os coxae

These are the two hip bones composed of three bones each: the ilium, ischium and pubis.

1 Sacroiliac joint

The hip bones unite posteriorly with the sacrum at the sacroiliac joints.

2 Pubic symphysis

the hip bones unite anteriorly at the joint called the pubic symphysis.

2 Pelvis (bony pelvis)

The bony pelvis is the entire ring of structures composed of the hip bones, pubic symphysis, and sacrum. It provides a strong support for the vertebral column and pelvic organs. It connects the bones of the lower limbs to the axial skeleton.

3 Ilium

The largest of the three components of the hip bones.

1 Superior ala

The large flat wing-shaped structure.

1 Iliac crest

The superior border of the ilium.

2 Greater sciatic notch

Below the posterior inferior iliac spine is the greater sciatic notch, through which the sciatic nerve passes. The sciatic nerve is the longest nerve in the body.

3 Iliac fossa

The medial surface of the ilium contains the iliac fossa where the tendon of the iliacus muscle attaches.

4 Iliac tuberosity

Posterior to the iliac fossa is the iliac tuberosity.

1 Auricular surface

Also posterior to the iliac fossa, the auricular surface articulates with the sacrum to form the sacroiliac joint.

2 Sacroiliac joint

2 Inferior body

The inferior body of the ilium helps to form the acetabulum.

1 Acetabulum

The acetabulum is the socket for the head of the femur.

4 Ischium

The inferior, posterior potion of the hip bone.

1 Body

The body of the ischium is the superior portion.

2 Ramus

The ramus is the inferior part.

1 Ischial tuberosity

The ischial tuberosity is a prominent tuberosity: a sitting bone.

2 Fusion with pubis

The ramus fuses with the pubis.

3 Obturator foramen

The ramus and the pubis surround the largest foramen of the skeleton called the obturator foramen. It is nearly completely closed by a fibrous membrane.

5 Pubis

The anterior and inferior part of the hip bone. It is composed of the superior and inferior rami and the body.

1 Superior ramus

2 Inferior ramus

3 Body

4 Pubic symphysis

The joint between the two hip bones.

5 Acetabulum

The deep fossa formed by the ilium, ischium and the pubis. The socket accepts the head of the femur, forming the coxal joint.

2 Lower limb

The lower limb has 30 bones in 4 locations: 1 femur in the thigh; the patella at the knee; the tibia and fibula in the leg; the 7 tarsals in the tarsus (ankle), 5 metatarsals in the metatarsus, and the 14 phalanges in the foot.

1 Femur

The longest, heaviest and strongest bone in the body. Its proximal end articulates with the acetabulum of the hip bone and the distal end articulates with tibia and patella.

1 Articulations

1 Hip (coxal) joint

The head at the proximal end of the femur articulates with the acetabulum of the hip bone to form the hip or coxal joint.

2 Parts of the femur

1 Proximal end

1 Head

The rounded head of the femur articulates with the acetabulum.

1 Fovea capitis

The head contains a small, centered depression called the fovea capitis. The ligament of the head of the femur connects the fovea capitis to the acetabulum.

2 Neck

The neck is a constricted region of the femur distal to the head. This is the usual site of fracture of the "hip".

3 Greater trochanter

The greater trochanter is the prominence felt and seen anterior to the hollow on the side of the hip, on the lateral surface of the hip. It is a point of attachment for the tendons of some of the thigh and buttock muscles.

4 Lesser trochanter

The lesser trochanter is inferior and medial to the greater trochanter: it also serves as an attachment point for tendons of the thigh and buttock.

2 Body

The body of the femur angles medially and as a result, the knee joints are closer to the midline.

3 Distal end

The medial and lateral condyles articulate with the medial and lateral condyles of the tibia.

1 Medial condyle

2 Lateral condyle

3 Patellar surface

Located between the condyles on the anterior surface.

2 Patella

The small, triangular bone located anterior to the knee joint. It is a sesamoid bone that develops in the tendon of the quadriceps femoris muscle. The patella increases the leverage of the tendon of the quadriceps femoris muscle and maintains the position of the tendon when the knee is flexed. It also protects the knee joint.

1 Base

The broad superior end of the patella.

2 Apex

The pointed inferior end.

3 Articular facets

The posterior surface of the patella contains two articular faces, one for the medial condyle fo the femur and the other for the lateral condyle of the femur.

4 Patellofemoral joint

The articulation between the posterior surface of the patella and the patellar surface of the femur.

1 Tibiofemoral (knee) joint

See below.

3 Tibia and fibula

1 Articulations

1 Tibiofemoral joint

The articulation between the lateral and medial condyles of the tibia with the lateral and medial condyles of the femur.

2 Distal tibiofibular joint

The distal end of the tibia articulates with the fibular notch of the fibula to form the distal tibiofibular joint.

3 Proximal tibiofibular joint

The inferior surface of the lateral condyle of the tibia articulates with the head of the fibula in the proximal tibiofibular joint.

4 Interosseus membrane

The tibia and fibula, like the radius and ulna, are connected by an interosseus membrane.

5 Talocrural (ankle) joint

The medial malleolus of the tibia and the lateral malleolus of the fibula articulates with the medial and lateral side (respectively) of the talus bone (a tarsal bone) to form the talocrural (ankle) joint.

2 Tibia

The shin bone is the larger, medial, weight-bearing bone of the leg. The tibia articulates at its proximal end with the femur and fibula, at its distal end with the fibula and talus bone of the ankle. The tibia and fibula are connected together with an interosseus membrane.

1 Lateral condyle

The proximal end of the tibia is expanded into the lateral and medial condyles. They articulate with the condyles of the femur to form the tibiofemoral (knee) joint.

2 Medial condyle

3 Medial malleolus

The medial surface of the distal end of the tibia forms the medial malleolus, which articulates with the talus of the ankle. It forms the prominence that can be felt on the medial surface of the ankle.

3 Fibula

The fibula is parallel and lateral to the tibia and is considerably smaller.

1 Head

The head of the fibula on the proximal end articulates with the inferior surface of the lateral condyle of the tibia, below the level of the knee joint to form the proximal tibiofibular joint.

2 Lateral malleolus

The distal end of the fibula has a projection called the lateral malleolus that articulates with the talus of the ankle. The lateral malleolus forms the prominence on the lateral surface of the ankle.

4 The ankle and the foot

1 Tarsus

The tarsus is the ankle and is the proximal region of the foot. It consists of seven bones, the tarsal bones. The names of the specific tarsal bones are here for your information only.

1 Tarsals

1 Intertarsal joints

The joints between the tarsal bones are called intertarsal joints.

2 Posterior tarsals

1 Talus

The talus is the most superior tarsal bone. It is the only bone of the foot that articulates with the fibula and tibia to form the talocrural (ankle) joint (see above).

2 Calcaneus

The largest and strongest tarsal bone.

3 Anterior tarsals

1 Navicular

On the medial side of the foot. Located distal to the talus and proximal to the cuneiform bones.

2 Three cuneiform bones

1 First (medial) cuneiform

2 Second (intermediate) cuneiform

3 Third (lateral) cuneiform

3 Cuboid

Lateral to the third cuneiform tarsal.

2 Talocrural (ankle) joint

The articulation between the talus and the fibula and tibia (see above).

2 Metatarsus

The intermediate region of the foot, consisting of five metatarsal bones.

1 Metatarsals

1 Base, shaft, and head

Like the metacarpals, each metatarsal has a proximal base, intermediate shaft, and distal head.

2 Numbered I to V

Like the metacarpals, numbered I to V, medial to lateral.

2 Tarsometatarsal joints

The metatarsals articulate proximally with the first, second and third cuneiform bones and with the cuboid bone to form the tarsometatarsal joints.

3 Metatarsophalangeal joints

The metatarsals articulate distally with the proximal row of the phalanges to form the metatarsophalangeal joints.

3 Phalanges

The distal component of the foot and resemble those of the hand in number and arrangement.

1 Numbered I to V, lateral to medial

Beginning with the great toe (I).

2 Phalanx

A single bone of the toe.

3 Hallux

The great toe. Has two large phalanges, proximal and distal....no middle phalanx.

4 14 phalanges

Three phalanges in each of the four toes. The great toe has two.

1 Proximal row

2 Middle row

3 Distal row

5 Base, shaft and head

Each phalanx consists of a proximal base, intermediate shaft, and distal head.

6 Interphalangeal joints

The articulations between phalanges of the foot.

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