Skeletal System Revised (Cueto) PDF

Skeletal System By : Marc Anthony P. Cueto MD Learning Objectives Describe the major functions of the skeletal system Describe the basic structure of bones To identify the different classification of bones Identify the different bones per region Bones  Bone is a form of con...

Skeletal System By : Marc Anthony P. Cueto MD Learning Objectives Describe the major functions of the skeletal system Describe the basic structure of bones To identify the different classification of bones Identify the different bones per region Bones  Bone is a form of connective tissue (review basic tissues) in which the intercellular substance consists of dense, white fibers embedded in a hard calcium phosphate matrix.  The fibrous tissue imparts resilience to the bone, while the calcium salts resist compression forces. Functions of Bones  1. Support. - give shape and support to the body; - individual bones or group of bones provide a framework for the attachment of soft tissues and organs  2. Protection. - skeletal elements protect against extraneous forces. - skull acts as barrier of the brain external assault. - ribs are commonly dubbed protective as they reduce the risk of impact, and respiratory movements depend upon the ribs. Functions of Bones  3. Blood Cell Production. - Hematopoietic function because of the presence of red bone marrow in spongy bones.  4. Storage. - Stores fats which are present in yellow bone marrow within the medullary cavity of long bones. - Calcium salts of bones is a valuable mineral reserve that maintain the normal concentrations of calcium and phosphate ions in body fluids.  5. Leverage. LEVER - a rigid piece that transmits and modifies force or motion Structure of Bones  A thick layer of fibrous tissue called the PERIOSTEUM covers all bone surfaces, other than the articulating surfaces.  The periosteum has an abundant vascular supply, and the cells on its deeper surface are osteogenic.  The periosteum is particularly well united to bone at sites where muscles, tendons, and ligaments are attached to bone. Bundles of collagen fibers known as Sharpey’s fibers extend from the periosteum into the underlying bone.  The periosteum receives a rich nerve supply and is very sensitive to trauma. Structure of Bones  Articular Cartilage - plate of cartilage which covers the articulating surface of bones. These surfaces are that parts of the bone which comes in contact with another bone in a joint.  Endosteum - a membrane that lines the medullary cavity of long bones. Structure of Bones  Bone Marrow - connective tissue found within bones. Types of Bone Marrow: a. Red bone marrow - concerned with production of RBC b. Yellow bone marrow – for the storage of fat. It is found within the medullary cavities of long bones  Nutrient blood vessels (nutrient artery) - enters thru the nutrient foramen to give nutrition to bones. Classification : Microscopic Appearance of Cut Surfaces  A. Compact or Dense bone  - These are hard and dense materials which forms the layer of bone structure (lamellae) just beneath the periosteum.  - the ivory surface of mature bone;  -there are no spaces between osteocytes.  B. Trabecular or Spongy Bone  – the interior of mature bone ( also termed cancellous or spongy bone);  - presence of spaces between osteocytes filled with red bone marrow. Classification : Developmental Origin  a. Intramembranous (Mesenchymal or Dermal bone) – formed by the direct formation of condensed mesenchyme. - the intramembranous bone resembles spongy bone, further remodeling around the trapped vessels can produce compact bones. - several flat bones of the skull, and the lower jaw, and clavicles are formed this way. - therefore they are found in flat bones and those that remain flat on maturation.  b. Intracartilaginous or Substitution ( Endochondral bone) -replacing a preformed cartilage model. -most human bones are preformed cartilages; -in early fetal life a long bone is prefigured by a rod of hyaline cartilage replacing a similar rod of condensed mesenchyme. Classification : Shape  Long Bones  Long bones are found in the limbs (e.g., the humerus, femur, metacarpals,metatarsals, and phalanges).  Their length is greater than their breadth  They have a tubular shaft, the diaphysis, and usually an epiphysis at each end.  During the growing phase, the diaphysis is separated from the epiphysis by an epiphyseal cartilage.  The part of the diaphysis that lies adjacent to the epiphyseal cartilage is called the metaphysis.  The shaft has a central marrow cavity containing bone marrow.  The outer part of the shaft is composed of compact bone that is covered by periosteum.  The ends of long bones are composed of cancellous bone surrounded by a thin layer of compact bone.  The articular surfaces of the ends of the bones are covered by hyaline cartilage.  Function : Support weight and facilitate movement Classification : Shape  Short Bones  Short bones are found in the hand and foot (e.g., the scaphoid, lunate, talus, and calcaneum).  They are roughly cuboidal in shape and are composed of cancellous bone surrounded by a thin layer of compact bone.  Short bones are covered with periosteum, and the articular surfaces are covered by hyaline cartilage. Classification : Shape  Flat Bones  Flat bones are found in the vault of the skull (e.g., the frontal and parietal bones).  They are composed of thin inner and outer layers of compact bone, the tables, separated by a layer of cancellous bone, the diploë.  The scapulae, although irregular in shape, are included in this group.  Function : Protect internal organs Classification : Shape  Irregular Bones  Irregular bones include those not assigned to the previous groups (e.g., the bones of the skull, the vertebrae, and the pelvic bones).  They are composed of a thin shell of compact bone with an interior made up of cancellous bone. Classification : Shape  Sesamoid bones  A sesamoid bone is one formed within a tendon where the tendon passes over a joint.  The greater part of a sesamoid bone is buried in the tendon, and the free surface is covered with cartilage.  The largest sesamoid bone is the patella (“kneecap”), which is located in the tendon of the quadriceps femoris.  Other examples are found in the tendons of the flexor pollicis brevis (in the thumb) and flexor hallucis brevis (in the big toe).  The function of a sesamoid bone is to reduce friction on the tendon; it can also alter the direction of pull of a tendon. Classification : Location  In the regional classification scheme, the bones are organized into two main groups: the axial and appendicular skeletons.  The axial skeleton consists of the elements forming the central axis of the body.  The appendicular skeleton consists of the bones forming the upper and lower limb girdles and extremities. Axial Skeleton Axial Skeleton  The axial skeleton creates framework that supports and protects organ systems in the dorsal and ventral cavities.  In addition, it provides an extensive surface area for the attachment of muscles that : adjusts the position of the head, neck and trunk perform respiratory movements; stabilize or position elements of the appendicular skeleton. Skull  The skull is the most modified part of the axial skeleton. It is the entire skeleton of the face including the mandible  Functions :  A skeletal complex adapted to support the brain and organs of special senses, 1. Sensation for seeing, 2. Hearing, 3. Taste, 4. Smell,  Protection of the brain from external impacts,  Serves as a barrier against stresses from powerful masticatory and axial musculature  The rigid cranial walls provide continuous isolation for cerebral circulation,  Contain openings that lead to the digestive tract, respiratory tract, and skull. Skull Vertebral Column  The vertebral column is the central, longitudinal bony pillar of the body.  It supports the skull, pectoral girdle, upper limbs, and thoracic cage and, by way of the pelvic girdle, transmits body weight to the lower limbs.  The spinal cord, the roots of the spinal nerves, and the covering meninges lie within the cavity of the vertebral column, which provides great protection to those structures. Vertebral Column  The vertebral column is composed of 33 vertebrae organized in five regions—7 cervical, 12 thoracic, 5 lumbar, 5 sacral (fused to form the sacrum), and ~4 coccygeal (the lower 3 are commonly fused).  In adults = 26 vertebrae  Numerous joints connect these many individual segments, thus making the vertebral column quite flexible. Vertebra Vertebrae  A typical vertebra consists of a rounded body anteriorly and a vertebral arch posteriorly.  These enclose a space termed the vertebral foramen. In an articulated skeleton, the vertebral foramina are aligned to form a continuous passageway termed the vertebral canal, which conveys the spinal cord and its coverings.  The vertebral arch consists of a pair of cylindrical pedicles, which form the sides of the arch, and a pair of flattened laminae, which complete the arch posteriorly.  The vertebral arch gives rise to seven processes: one spinous, two transverse, and four articular. Typical Cervical Vertebrae  Typical cervical vertebrae, such as C4 or C5, have several characteristic features that differentiate them from thoracic or lumbar vertebrae.  Cervical vertebrae have a small body, reflecting the fact that they carry the least amount of body weight.  Cervical vertebrae usually have a bifid (Y-shaped) spinous process. The spinous processes of the C3–C6 vertebrae are short, but the spine of C7 is much longer. You can find these vertebrae by running your finger down the midline of the posterior neck until you encounter the prominent C7 spine located at the base of the neck.  The transverse processes of the cervical vertebrae are sharply curved (U-shaped) to allow for passage of the cervical spinal nerves.  Each transverse process also has an opening called the transverse foramen. An important artery (vertebral artery) that supplies the brain ascends up the neck by passing through these openings.  The superior and inferior articular processes of the cervical vertebrae are flattened and largely face upward or downward, respectively. Upper six cervical vertebrae Vertebral artery Atypical Cervical Vertebrae : Atlas  The first cervical vertebra, or atlas, does not possess a body or a spinous process.  Instead, it has anterior and posterior arches.  It has a lateral mass on each side with articular surfaces on its upper surface for articulation with the occipital condyles of the skull (atlanto- occipital joints) and articular surfaces on its inferior surface for articulation with the C2 vertebra (atlantoaxial joints). Atypical Cervical Vertebrae : Axis  The second cervical vertebra, or axis, has a peglike odontoid process (dens) that projects upward from the superior surface of the body.  The dens represents the body of the atlas that fused with the body of the axis during early development. Atlanto Axial Joint Atypical Cervical Vertebra : Vertebra Prominens  The seventh cervical vertebra, or vertebra prominens, is so named because it has the longest spinous process, and the process is not bifid.  The transverse process is large, but the foramen transversarium is small and transmits the vertebral vein or veins. Typical Thoracic Vertebrae  The bodies of the thoracic vertebrae are larger than those of cervical vertebrae.  The characteristic feature for a typical midthoracic vertebra is the spinous process, which is long and has a pronounced downward angle that causes it to overlap the next inferior vertebra.  The superior articular processes of thoracic vertebrae face anteriorly and the inferior processes face posteriorly. These orientations are important determinants for the type and range of movements available to the thoracic region of the vertebral column.  Thoracic vertebrae have several additional articulation sites, each of which is called a facet, where a rib is attached.  Most thoracic vertebrae have two facets located on the lateral sides of the body, each of which is called a costal facet (costal = “rib”).  These are for articulation with the head (end) of a rib. An additional facet is located on the transverse process for articulation with the tubercle of a rib. Typical Lumbar Vertebrae Sacrum and Coccyx  The sacrum provides support to the pelvic bones and forms the lower back portion of the pelvis.  Coccyx also known as tail is the rear end of the spinal column Thoracic Cage / Rib Cage  The thoracic cage (rib cage) forms the thorax (chest) portion of the body.  It consists of the 12 pairs of ribs with their costal cartilages and the sternum.  The ribs are anchored posteriorly to the 12 thoracic vertebrae (T1–T12). The thoracic cage protects the heart and lungs. Thoracic Cage/Rib Cage  The upper seven pairs of ribs are known as true ribs because their costal cartilages articulate anteriorly directly with the sternum.  The lower five pairs of ribs (ribs eight to twelve) are known as false ribs because their costal cartilages do not articulate directly with the sternum.  The costal cartilages of ribs eight to ten connect with the costal cartilages of the ribs above.  The costal cartilages of the ribs eleven and twelve have no articulation with other ribs or with the sternum and are know as floating ribs. Sternum  The sternum is the elongated bony structure that anchors the anterior thoracic cage.  It consists of three parts: the manubrium, body, and xiphoid process. Ribs  Each rib is a curved, flattened bone that contributes to the wall of the thorax.  The ribs articulate posteriorly with the T1– T12 thoracic vertebrae, and most attach anteriorly via their costal cartilages to the sternum.  There are 12 pairs of ribs. The ribs are numbered 1–12 in accordance with the thoracic vertebrae. Appendicular Skeleton Pectoral Girdle Pectoral Girdle : Clavicle  The appendicular skeleton includes all of the limb bones, plus the bones that unite each limb with the axial skeleton.  The bones that attach each upper limb to the axial skeleton form the pectoral girdle (shoulder girdle). This consists of two bones : the scapula and clavicle.  The clavicle (collarbone) is an S-shaped bone located on the anterior side of the shoulder. It is attached on its medial end to the sternum of the thoracic cage, which is part of the axial skeleton.  The lateral end of the clavicle articulates (joins) with the scapula just above the shoulder joint. Pectoral Girdle : Clavicle  Functions  Connect the arm with the rest of the skeleton.  Allow free movement of the shoulder away from the body.  Transmit force or any physical impact from the upper limb to the axial skeleton.  Protect the neurovascular bundle supplying the upper limb.  Along with the rib cage, they protect the heart from external shock. Pectoral Girdle : Clavicle 1. Sternal (Medial) End  The part of the clavicle that lies towards the sternum is called the sternal end or the medial end.  It is curved and convex, bearing a rounded end that articulates with the sternum, forming the sternoclavicular joint. i) Sternal Facet  On the far edge of the sternal end, a triangular facet, called the sternal facet is present.  It bears a posterior tip and an anterior base, connecting the clavicle to the manubrium of the sternum at the sternoclavicular (SC) joint.  The articular surface extends to the inferior side, articulating with the costal cartilage of the first rib. Pectoral Girdle : Clavicle 2. Acromial (Lateral) End  The broad, flat region of the clavicle lying towards the scapula is known as the acromial end or lateral end.  It is both the widest and thinnest portion of the clavicle.  This region bears a facet known as acromial facet that articulates with the scapula.  The lateral end has two borders: anterior and posterior.  The anterior border is concave forward, whereas the posterior border is convex backward. i) Acromial Facet  At the extreme edge of the acromial end, there is a small, flattened, and oval facet called the acromial facet.  This helps the clavicle to articulate with the acromion of the scapula, forming the acromioclavicular (AC) joint. Pectoral Girdle : Clavicle 3. Shaft  The middle region of the clavicle, i.e., the region between the sternal and acromial end, is the shaft. Several muscles originate from or get attached in this part.  The shaft can be divided into two regions, depending on its location and spread.  The region lying on the side of the sternal end, covers the maximum portion, approximately two- thirds of the bone.  This region is known as the medial two-third.  On the other hand, the region of the shaft that lies towards the acromial end covers the remaining one- third of the bone.  This region is known as the lateral third. Several important bony landmarks are found in these regions. Pectoral Girdle : Clavicle Medial two-third i) Costal Tuberosity  On the inferior side of the sternal end, the bone bears a roughened oval elevation, called the costal tuberosity.  It is over 2 cm in length and acts as a site of attachment for costoclavicular ligament.  This ligament attaches the clavicle to the costal cartilage of the first rib. Pectoral Girdle : Clavicle  Lateral third  i) Conoid Tubercle  On the inferior surface of the bone, there is a rough, bumpy projection called the conoid tubercle.  It serves as an attachment site for the conoid ligament, a part of the coracoclavicular ligament.  The coracoclavicular ligament attaches the clavicle to the coracoid process of the scapula.  The prominence of the conoid tubercle serves as a useful landmark to identify the inferior surface of the clavicle. Pectoral Girdle : Clavicle  ii) Trapezoid Line  It is an elevation or ridge that runs obliquely from the conoid tubercle to the lateral end of the clavicle.  It provides an attachment point for the trapezoid ligament, which is also a part of the coracoclavicular ligament mentioned above.  Iii) Subclavian groove or sulcus  It is an indentation that runs horizontally along the inferior surface of the shaft, from the costal tuberosity to the conoid tubercle.  It acts as a site of attachment for the subclavius muscle. Pectoral Girdle : Scapula  The scapula (shoulder blade) lies on the posterior aspect of the shoulder.  It is supported by the clavicle, which also articulates with the humerus (arm bone) to form the shoulder joint.  The scapula is a flat, triangular-shaped bone with a prominent ridge running across its posterior surface – spine of the scapula.  This ridge extends out laterally, where it forms the bony tip of the shoulder and joins with the lateral end of the clavicle – acromion  Glenoid fossa – articulates with the head of the humerus Pectoral Girdle : Scapula  Functions  The scapula helps in several daily movements and smooth motion of the upper arm.  It assists in both forward and backward movement of the pectoral girdle and chest muscles by moving closer and away from the vertebral column.  During some motions, like shrugging the shoulders, the entire shoulder capsule moves up and down due to elevation and depression of this bone.  It stabilizes the shoulder capsule during excessive arm motion by rotating upwards and downwards. Pectoral Girdle : Scapula  The body of the scapula consists of a triangular-shaped flat blade, with an apex pointed below. Since it is triangular, it bears three borders.  Borders and angles  Superior border: It is the shortest and thinnest border.  Medial border: It is a thin border running parallel to the vertebral column and is often referred to as the vertebral border.  Lateral border: It is alternatively known as the axillary border, running towards the apex of the axilla. Out of the three borders, it is the thickest and strongest. It also bears the glenoid cavity, which articulates with the rounded head of the humerus, forming the shoulder joint or glenohumeral joint. Pectoral Girdle : Scapula  It also has three angles:  Lateral angle: where the superior border converges with the lateral border.  Superior angle: Where the superior border also meets with the medial border.  Inferior angle: Where the medial and lateral borders meet. Pectoral Girdle : Scapula Surfaces 1. Costal Surface  It is the anterior surface of the scapula facing the thoracic cage or ribcage.  It has a large concave depression over most of the surface, called the subscapular fossa, from where the rotator cuff muscle subscapularis originates.  This region is marked by longitudinal ridges, out of which a thick ridge joins the lateral border. This part of the bone acts as a lever for the action of the serratus anterior muscle, helping to move the arm away from the body.  A hook-like projection, called the coracoid process, originates from the superior border of the head of the scapula, projecting forward and curving laterally, lying underneath the clavicle. Pectoral Girdle : Scapula 2. Lateral Surface  This surface of the scapula faces the humerus.  Its important bony landmarks are:  Glenoid fossa – It is a shallow pyriform cavity located at the lateral angle of the scapula. It articulates with the rounded head of the humerus, forming the glenohumeral (shoulder) joint.  Supraglenoid tubercle – It is a small rough projection located immediately above the glenoid fossa near the base of the coracoid process.  Infraglenoid tubercle – It is a rough impression located on the lateral part of the scapula, immediately below the glenoid fossa. Pectoral Girdle : Scapula  3. Posterior Surface  This surface of the scapula faces outwards. Most of the rotator cuff muscles of the shoulder arise from here. Its important anatomical landmarks are:  Spine: It is a triangular plate of bone located on the posterior surface, running transversely across the scapula, dividing the dorsal surface of the scapula into supraspinous and infraspinous fossae.  The two fossae remain connected by the spinoglenoid notch, situated lateral to the root of the spine, bridged by the spinoglenoid ligament.  It has three borders and two surfaces. Its posterior border, the crest of the spine, bears upper and lower lips. Pectoral Girdle : Scapula  Supraspinous fossa: It is the area above the spine of the scapula.  It is concave, smooth, and broader at its vertebral than at its humeral end. The supraspinatus muscle originates from the middle of this area.  It is much smaller than the infraspinous fossa, bearing the spinoglenoid fossa on its side.  The fossa houses the suprascapular canal, connecting the suprascapular notch and the spinoglenoid notch conveying the suprascapular nerve and vessels. Pectoral Girdle : Scapula  Infraspinous fossa: It is the area below the spine of the scapula. It is convex and much larger than the preceding one.  At its upper part, towards the vertebral margin, it shows a shallow concavity. In the center, it is convex, while near the lateral border, it has a deep groove running from the upper toward the lower part.  Acromion: It is a large bony projection on the upper end of the scapula. It arches over the shoulder joint, articulating with the clavicle at the acromioclavicular (AC) joint. Pectoral Girdle : Scapula Articulations  Glenohumeral joint: This is a ball and socket joint formed between the glenoid fossa of the scapula and the rounded head of the humerus.  Acromioclavicular joint: It is a gliding joint between the acromion of the scapula and the clavicle. Upper Limb Upper Limb  The upper limb is divided into three regions.  These consist of the arm, located between the shoulder and elbow joints; the forearm, which is between the elbow and wrist joints; and the hand, which is located distal to the wrist.  There are 30 bones in each upper limb. The humerus is the single bone of the upper arm, and the ulna (medially) and the radius (laterally) are the paired bones of the forearm.  The base of the hand contains eight bones, each called a carpal bone, and the palm of the hand is formed by five bones, each called a metacarpal bone.  The fingers and thumb contain a total of 14 bones, each of which is a phalanx bone of the hand. Upper Limb : Humerus  The humerus (Latin : upper arm; shoulder) is the longest and largest bone in the upper limb. it forms the framework of the arm and it has expanded ends and a shaft.  Proximally a round head forms with the scapular glenoid cavity  The distal end, loosely termed ‘condylar’, is adapted to the forearm bones at the elbow joint.  https://sketchfab.com/3d-models/humero- humerus- 9b83b59269ad4c2abfe0a0fb18fec8b9 Upper Limb : Humerus  Functions  It helps in the functioning of the upper limb by providing structural support, and serving as an attachment site to 13 muscles that aid in the movements of the hand and elbow.  The humeral head makes up a portion of the ball-and-socket shoulder joint, which is the insertion point for muscles making up the shoulder girdle.  Several ligaments present in this area assist with securing the musculature. They also provide motion to the shoulder joint.  The basilic vein, traveling close to the humerus, helps drain parts of the hand and forearm.  The brachial plexus lying across the front portion of the bone provides sensation and motion to every muscle in the arm and certain portions of the neck and spinal cord.  Upper Limb : Humerus  The humerus comprises a proximal region, a shaft, and a distal region. All of these are important anatomical landmarks.  1. Proximal Landmarks of Humerus  Head: The proximal end of the humerus forms a smooth, spherical structure known as the head.  It is the ball in the the ball-and-socket joint in the shoulder, where the glenoid cavity of the scapula acts as the socket.  Due to its round shape, the head rotates around its axis at the shoulder joint and moves in all directions.  Upper Limb : Humerus  Anatomical Neck: Just below the head, the humerus narrows into the anatomical neck.  It separates the head from the other two regions: greater and lesser tuberosities.  Greater Tubercle (Greater Tuberosity): It lies on the lateral side of the bone, with an anterior, and a posterior surface.  The three rotator cuff muscles, supraspinatus, infraspinatus, and teres minor, attach to the greater tubercle’s superior, middle, and inferior facets, respectively.  Upper Limb : Humerus  Lesser Tubercle (Lesser Tuberosity): It is much smaller than the greater tubercle located inferior to the head, bearing only an anterior surface.  This is where the the fourth and last rotator cuff muscle, the subscapularis, attaches.  Intertubercular Sulcus: Separating the two tuberosities is a deep groove known as the intertubercular sulcus or bicipital groove.  The tendon of the bicep’s long head emerges from the shoulder joint and runs through this groove.  The edges of the intertubercular sulcus are known as lips, where pectoralis major, teres major, and latissimus dorsi get inserted.  Upper Limb : Humerus  Surgical Neck: It is the part between the tuberosities and the shaft where the humerus narrows down to form the surgical neck before extending toward the elbow joint.  Here, circumflex humeral vessels and the axillary nerve lie against the bone.  The surgical neck is a common site for fractures (hence its name), while fractures of the anatomical neck are rare. Upper Limb : Humerus  2. The Shaft  A long, cylindrical shaft (body) composes the middle part of the humerus.  It bears a roughened surface on the lateral side, known as the deltoid tuberosity, as the deltoid muscle gets attached there.  The width of the bone gradually increases past the deltoid tuberosity, becoming double as it moves towards the elbow joint. Upper Limb : Humerus  A shallow depression called the radial (or spiral) groove runs diagonally down the posterior surface of the humerus, parallel to the deltoid tuberosity. This groove contains the radial nerve and the profunda brachii artery.  The shaft serves as the surface for attachment of several muscles  Anterior Side: Coracobrachialis, brachialis, deltoid, brachioradialis  Posterior Side: The medial and lateral heads of the triceps. Their origin is marked by the spiral groove on the posterior side of the humerus. Upper Limb : Humerus  3. Distal Region of Humerus  The lower end of the humerus is the distal humerus, containing two joint- forming processes, the capitulum and the trochlea.  The trochlea tightly hinges with the forearm’s ulna, forming half of the elbow joint.  On the other hand, the convex capitulum articulates with the concave radial head on the lateral side of the arm.  The joint thus formed is the elbow that allows the human arm to bend and fold in the middle. Upper Limb : Humerus  A small cavity called the olecranon fossa on the posterior side of the bone locks the olecranon or the tip of the ulna into the bone.  This locking prevents us from extending the elbow beyond 180 degrees.  Despite this, the distal portion of the humerus also contains two other depressions, known as the coronoid and radial fossae.  They lodge the forearm bones during flexion or extension of the elbow. Upper Limb : Humerus  The medial and lateral borders of the distal humerus form the medial and lateral supracondylar ridges.  Among the two ridges, the lateral supracondylar ridge is relatively roughened, providing the common origin site of the forearm extensor muscles.  The extracapsular projections of the bone, the lateral and medial epicondyles, are found immediately distal to the supracondylar ridges.  Both of the epicondyles can be felt at the elbow from the outside.  Among the two, the medial is larger, extending more towards the elbow joint.  The ulnar nerve passes through a groove present on the posterior side of the medial epicondyle. Upper Limb : Radius  The radius, also known as the radial bone, is one of the two forearm bones in the human body, with the other being the ulna. It is instrumental in the shaping and use of hands.  Where is the Radius Bone Located in the Arm  It is located on the thumb side of the hand, lying laterally in the lower arm, parallel in reference to the ulna.  https://sketchfab.com/3d-models/radio- radius- f71bb6cf71914e22b7b860c8b9151f78 Upper Limb : Radius  Functions of the Radius  Proper functioning of the radius is essential for performing any day-to-day activity with our hand, from holding something, balancing with the arm, throwing something, writing, typing, using the phone, etc.  It forms a hinge joint with the humerus bone, which allows us to flex and extend the elbow.  The radius moves around the ulna at the wrist, enabling us to turn our hand’s palm up and down.  The bone also forms an ellipsoidal joint with the proximal carpal row that allows us to move, rotate, bend, and flex the wrist.  Upper Limb : Radius  The proximal end of the radius are The head is discoid, its proximal surface has a shallow cup for the humeral capitulum. Its smooth articular periphery is vertically deepest medially, where it contacts the ulnar radial notch. The neck is the constriction distal to the head, which overhangs it, especially on the lateral side. The tuberosity is distal to the medial part of the neck; it is posteriorly rough but anteriorly usually smooth. Upper Limb : Radius  The distal end are describe as Its lateral surface is slightly rough, projecting distally as a styloid process palpable when tendons around it are slack. Distal is the smooth carpal articular surface, divided by a ridge into medial and lateral areas. The anterior surface is a thick, prominent ridge, palpable even through overlying tendons. The medial surface is the ulnar notch, smooth,anteroposteriorly concave for articulation with the ulna’s head. Upper Limb : Ulna  Ulna (plural: ulnae; pronunciation: úl-nu) is one of the two primary bones forming the forearms in humans, the other one being the radius.  There is one ulna bone in each arm. It is a long bone and is vital in forming both the wrist and elbow joints.  Where is the Ulna Bone Located in the Human Body  It is the medial bone of the forearm, located on the side opposite to the thumb, that is on the side of the little finger, extending from the region of the wrist to the elbow.  In other words, the ulna can be found between the proximal carpal row and the upper arm bone humerus, running parallel to the other lower arm bone radius. Upper Limb : Ulna  The proximal end has the following The olecranon process is bent forwards at its summit like beak, which enters the humeral olecranon fossa in extension. The coronoid process projects anteriorly distal to the olecranon process Distal to which, on the lateral surface, is a shallow, smooth, oval radial notch for articulation with the radial head. The coronoid’s anterior surface is triangular, its distal part being the tuberosity of the ulna. The radial notch , an oval proximal depression on the lateral aspect of the coronoid, articulates with the peripheryof the radial head The trochlear notch articulates with the trochlea of the humerus https://sketchfab.com/3d-models/ulna- 3bccfa9e2e0a4dab99035605fa9ac059 Upper Limb : Ulna  The distal of ulna is  a.The head is visible in pronation on the posteromedial carpal aspect and can be gripped when the supinated hand is flexed.  b.The latter, the styloid process a short round, posterolateral projection of the ulna’s distal end. Upper Limb : Carpal Bones  The CARPAL bones contains eight bones in proximal and distal rows of four.  The term "carpus" is derived from the Latin carpus and the Greek καρπός (karpós), meaning "wrist".  Proximally, in lateral to medial order, are the : the scaphoid, the lunate, the triquetral, and the pisiform https://sketchfab.com/3d-models/bones-of- the-hand-turntable- cd8e31d740824d6b93791d52d53be525 Upper Limb : Carpal Bones  Distal row, are composed of: trapezium, trapezoid, capitate and hamate Upper Limb : Metacarpals  The METACARPALS is composed of five metacarpal bones, conventionally numbered in lateromedial order. These are miniature long bones with a distal head, shaft, and expanded base.  "the middle bones of the hand," 1650s, Modern Latin, from Greek metakarpion, from meta "between; next after" (see meta-) + karpos "wrist" (see carpus). In humans, the part of the hand between the wrist and the fingers or thumb  There are 14 PHALANGES, three in each finger, two in the thumb. Each has a head, shaft and proximal base. Pelvic Girdle Pelvic Girdle  The pelvic girdle is a ring-like bony structure, located in the lower part of the trunk. It connects the axial skeleton to the lower limbs.  The bony pelvis consists of the two hip bones (also known as innominate or pelvic bones), the sacrum and the coccyx.  There are four articulations within the pelvis:  Sacroiliac joints (x2) – between the ilium of the hip bones, and the sacrum  Sacrococcygeal symphysis – between the sacrum and the coccyx.  Pubic symphysis – between the pubis bodies of the two hip bones.  Ligaments attach the lateral border of the sacrum to various bony landmarks on the bony pelvis to aid stability. Functions of the Pelvis  The strong and rigid pelvis is adapted to serve a number of roles in the human body. The main functions being:  Transfer of weight from the upper axial skeleton to the lower appendicular components of the skeleton, especially during movement.  Provides attachment for a number of muscles and ligaments used in locomotion.  Contains and protects the abdominopelvic and pelvic viscera. The Greater and Lesser Pelvis  The osteology of the pelvic girdle allows the pelvic region to be divided into two:  Greater pelvis (false pelvis) – located superiorly, it provides support of the lower abdominal viscera (such as the ileum and sigmoid colon). It has little obstetric relevance.  Lesser pelvis (true pelvis) – located inferiorly. Within the lesser pelvis reside the pelvic cavity and pelvic viscera.  The junction between the greater and lesser pelvis is known as the pelvic inlet. The outer bony edges of the pelvic inlet are called the pelvic brim. Pelvic Inlet  The pelvic inlet marks the boundary between the greater pelvis and lesser pelvis. Its size is defined by its edge, the pelvic brim.  The borders of the pelvic inlet:  Posterior – sacral promontory (the superior portion of the sacrum) and sacral wings (ala).  Lateral – arcuate line on the inner surface of the ilium, and the pectineal line on the superior pubic ramus.  Anterior – pubic symphysis.  The pelvic inlet determines the size and shape of the birth canal, with the prominent ridges a key site for attachment of muscle and ligaments. Pelvic Outlet  The pelvic outlet is located at the end of the lesser pelvis, and the beginning of the pelvic wall.  Its borders are:  Posterior: The tip of the coccyx  Lateral: The ischial tuberosities and the inferior margin of the sacrotuberous ligament  Anterior: The pubic arch (the inferior border of the ischiopubic rami).  The angle beneath the pubic arch is known as the sub-pubic angle and is of a greater size in women. Composition of the Hip Bone  The hip bone is comprised of the three parts; the ilium, pubis and ischium. Prior to puberty, the triradiate cartilage separates these parts – and fusion only begins at the age of 15-17.  Together, the ilium, pubis and ischium form a cup-shaped socket known as the acetabulum (literal meaning in Latin is ‘vinegar cup‘). The head of the femur articulates with the acetabulum to form the hip joint.  https://sketchfab.com/3d-models/female- pelvis-2b6d64eef5d840bda4b998e27895038e The Ilium  The ilium is the widest and largest of the three parts of the hip bone, and is located superiorly. The body of the ilium forms the superior part of the acetabulum (acetabular roof). Immediately above the acetabulum, the ilium expands to form the wing (or ala).  The wing of the ilium has two surfaces:  Inner surface – has a concave shape, which produces the iliac fossa (site of origin of the iliacus muscle).  External surface (gluteal surface) – has a convex shape and provides attachments to the gluteal muscles.  The superior margin of the wing is thickened, forming the iliac crest. It extends from the anterior superior iliac spine (ASIS) to the posterior superior iliac spine (PSIS).  On the posterior aspect of the ilium there is an indentation known as the greater sciatic notch. The Pubis  The pubis is the most anterior portion of the hip bone. It consists of a body, superior ramus and inferior ramus (ramus = branch).  Pubic body – located medially, it articulates with the opposite pubic body at the pubic symphysis. Its superior aspect is marked by a rounded thickening (the pubic crest), which extends laterally as the pubic tubercle.  Superior pubic ramus – extends laterally from the body to form part of the acetabulum.  Inferior pubic ramus – projects towards the ischium.  Together, the superior and inferior rami enclose part of the obturator foramen – through which the obturator nerve, artery and vein pass through to reach the lower limb. The Ischium  The ischium forms the posteroinferior part of the hip bone.  Much like the pubis, it is composed of a body, an inferior ramus and superior ramus.  The inferior ischial ramus combines with the inferior pubic ramus forming the ischiopubic ramus, which encloses part of the obturator foramen.  The posterorinferior aspect of the ischium forms the ischial tuberosities and when sitting, it is these tuberosities on which our body weight falls. The Ischium  Near the junction of the superior ramus and body is a posteromedial projection of bone; the ischial spine.  Two important ligaments attach to the ischium:  Sacrospinous ligament – runs from the ischial spine to the sacrum, thus creating the greater sciatic foramen through which lower limb neurovasculature (including the sciatic nerve) transcends.  Sacrotuberous ligament – runs from the sacrum to the ischial tuberosity, forming the lesser sciatic foramen. Lower Limb The Femur Femur  The femur is the only bone in the thigh and the longest bone in the body.  It acts as the site of origin and attachment of many muscles and ligaments, and can be divided into three parts; proximal, shaft and distal.  https://sketchfab.com/3d- models/femur-femur- 440a8bf36c2a43d6a16c0d776c783b 45 Proximal Femur  The proximal aspect of the femur articulates with the acetabulum of the pelvis to form the hip joint.  It consists of a head and neck, and two bony processes – the greater and lesser trochanters. There are also two bony ridges connecting the two trochanters; the intertrochanteric line anteriorly and the trochanteric crest posteriorly.  Head – articulates with the acetabulum of the pelvis to form the hip joint. It has a smooth surface, covered with articular cartilage (except for a small depression – the fovea – where ligamentum teres attaches). Proximal Femur  Neck – connects the head of the femur with the shaft. It is cylindrical, projecting in a superior and medial direction. It is set at an angle of approximately 135 degrees to the shaft. This angle of projection allows for an increased range of movement at the hip joint.  Greater trochanter – the most lateral palpable projection of bone that originates from the anterior aspect, just lateral to the neck.  It is the site of attachment for many of the muscles in the gluteal region, such as gluteus medius, gluteus minimus and piriformis. The vastus lateralis originates from this site.  An avulsion fracture of the greater trochanter can occur as a result of forceful contraction of the gluteus medius. Proximal Femur  Lesser trochanter – smaller than the greater trochanter. It projects from the posteromedial side of the femur, just inferior to the neck- shaft junction.  It is the site of attachment for iliopsoas (forceful contraction of which can cause an avulsion fracture of the lesser trochanter). Proximal Femur  Intertrochanteric line – a ridge of bone that runs in an inferomedial direction on the anterior surface of the femur, spanning between the two trochanters. After it passes the lesser trochanter on the posterior surface, it is known as the pectineal line.  It is the site of attachment for the iliofemoral ligament (the strongest ligament of the hip joint).  It also serves as the anterior attachment of the hip joint capsule. Proximal Femur  Intertrochanteric crest – like the intertrochanteric line, this is a ridge of bone that connects the two trochanters.  It is located on the posterior surface of the femur.  There is a rounded tubercle on its superior half called the quadrate tubercle; where quadratus femoris attaches. The Shaft  The shaft of the femur descends in a slight medial direction.  This brings the knees closer to the body’s centre of gravity, increasing stability.  A cross section of the shaft in the middle is circular but flattened posteriorly at the proximal and distal aspects.  On the posterior surface of the femoral shaft, there are roughened ridges of bone, called the linea aspera (Latin for rough line).  This splits distally to form the medial and lateral supracondylar lines. The flat popliteal surface lies between them. The Shaft  Proximally, the medial border of the linea aspera becomes the pectineal line.  The lateral border becomes the gluteal tuberosity, where the gluteus maximus attaches.  Distally, the linea aspera widens and forms the floor of the popliteal fossa, the medial and lateral borders form the medial and lateral supracondylar lines.  The medial supracondylar line ends at the adductor tubercle, where the adductor magnus attaches.  The Distal Femur  The distal end of the femur is characterised by the presence of the medial and lateral condyles, which articulate with the tibia and patella to form the knee joint.  Medial and lateral condyles – rounded areas at the end of the femur.  The posterior and inferior surfaces articulate with the tibia and menisci of the knee, while the anterior surface articulates with the patella.  The more prominent lateral condyle helps prevent the natural lateral movement of the patella; a flatter condyle is more likely to result in patellar Condyle and epicondyle occur at the end of the long dislocation. bones. The condyle is more prominent than the epicondyle. The condyle is smooth and round whereas epicondyle is rough. Epicondyle is a projection on the condyle. The main difference between condyle and epicondyle is that condyle forms an articulation with another bone. whereas epicondyle provides sites for the attachment of muscles.  The Distal Femur  Medial and lateral epicondyles – bony elevations on the non-articular areas of the condyles. The medial epicondyle is the larger.  The medial and lateral collateral ligaments of the knee originate from their respective epicondyles.  Intercondylar fossa – a deep notch on the posterior surface of the femur, between the two condyles. It contains two facets for attachment of intracapsular knee ligaments; the anterior cruciate ligament (ACL) attaches to the medial aspect of the lateral condyle and the posterior cruciate ligament (PCL) to the lateral aspect of Condyle and epicondyle occur at the end of the long bones. The condyle is more prominent than the the medial condyle. epicondyle. The condyle is smooth and round whereas epicondyle is rough. Epicondyle is a projection on the condyle. The main difference between condyle and epicondyle is that condyle forms an articulation with another bone. whereas epicondyle provides sites for the attachment of muscles. The Patella Patella  The patella (kneecap) is located at the front of the knee joint, within the patellofemoral groove of the femur. Its superior aspect is attached to the quadriceps tendon and inferior aspect to the patellar ligament.  It is classified as a sesamoid type bone due to its position within the quadriceps tendon, and is the largest sesamoid bone in the body. In this article we will look at the anatomy of the patella – its surface features, functions and clinical relevance.  The patella has two main functions:  Leg extension – Enhances the leverage that the quadriceps tendon can exert on the femur, increasing the efficiency of the muscle.  Protection – Protects the anterior aspect of the knee joint from physical trauma.  https://sketchfab.com/3d-models/patela- patella-f0e558f9a8734e459bee82a319876621 Patella  The patella has a triangular shape, with anterior and posterior surfaces. The apex of the patella is situated inferiorly and is connected to the tibial tuberosity by the patellar ligament. The base forms the superior aspect of the bone and provides the attachment area for the quadriceps tendon.  The posterior surface of the patella articulates with the femur, and is marked by two facets:  Medial facet – articulates with the medial condyle of the femur.  Lateral facet – articulates with the lateral condyle of the femur. The Tibia Tibia  The tibia is the main bone of the lower leg, forming what is more commonly known as the shin.  It expands at its proximal and distal ends; articulating at the knee and ankle joints respectively. The tibia is the second largest bone in the body and it is a key weight-bearing structure.  https://sketchfab.com/3d-models/tibia- 77bcff2d834e47f4bb19fe19f912f44b Proximal tibia  The proximal tibia is widened by the medial and lateral condyles, which aid in weight- bearing.  The condyles form a flat surface, known as the tibial plateau.  This structure articulates with the femoral condyles to form the key articulation of the knee joint.  Located between the condyles is a region called the intercondylar eminence – this projects upwards on either side as the medial and lateral intercondylar tubercles.  This area is the main site of attachment for the ligaments and the menisci of the knee joint.  The intercondylar tubercles of the tibia articulate with the intercondylar fossa of the femur. Tibial Shaft  The shaft of the tibia is prism-shaped, with three borders and three surfaces; anterior, posterior and lateral. For brevity, only the anatomically and clinically important borders/surfaces are mentioned here.  Anterior border – palpable subcutaneously down the anterior surface of the leg as the shin. The proximal aspect of the anterior border is marked by the tibial tuberosity; the attachment site for the patella ligament.  Posterior surface – marked by a ridge of bone known as soleal line. This line is the site of origin for part of the soleus muscle, and extends inferomedially, eventually blending with the medial border of the tibia. There is usually a nutrient artery proximal to the soleal line.  Lateral border – also known as the interosseous border. It gives attachment to the interosseous membrane that binds the tibia and the fibula together. Distal Tibia  The distal end of the tibia widens to assist with weight-bearing.  The medial malleolus is a bony projection continuing inferiorly on the medial aspect of the tibia.  It articulates with the tarsal bones to form part of the ankle joint.  On the posterior surface of the tibia, there is a groove through which the tendon of tibialis posterior passes.  Laterally is the fibular notch, where the fibula is bound to the tibia – forming the distal tibiofibular joint. The Fibula Fibula  The fibula is a bone located within the lateral aspect of the leg. Its main function is to act as an attachment for muscles, and not as a weight-bearer.  It has three main articulations:  Proximal tibiofibular joint – articulates with the lateral condyle of the tibia.  Distal tibiofibular joint – articulates with the fibular notch of the tibia.  Ankle joint – articulates with the talus bone of the foot.  https://sketchfab.com/3d- models/fibulafibula- 4976343a75af43cdb5573d653562e11d Fibula  Proximal  At the proximal end, the fibula has an enlarged head, which contains a facet for articulation with the lateral condyle of the tibia. On the posterior and lateral surface of the fibular neck, the common fibular nerve can be found.  Shaft  The fibular shaft has three surfaces – anterior, lateral and posterior. The leg is split into three compartments, and each surface faces its respective compartment e.g anterior surface faces the anterior compartment of the leg.  Distal  Distally, the lateral surface continues inferiorly, and is called the lateral malleolus. The lateral malleolus is more prominent than the medial malleolus, and can be palpated at the ankle on the lateral side of the leg. Bones of the Foot: Tarsals, Metatarsals and Phalanges Bones of the Foot: Tarsals, Metatarsals and Phalanges  The bones of the foot provide mechanical support for the soft tissues; helping the foot withstand the weight of the body whilst standing and in motion.  They can be divided into three groups:  Tarsals – a set of seven irregularly shaped bones. They are situated proximally in the foot in the ankle area.  Metatarsals – connect the phalanges to the tarsals. There are five in number – one for each digit.  Phalanges – the bones of the toes. Each toe has three phalanges – proximal, intermediate, and distal (except the big toe, which only has two phalanges).  The foot can also be divided up into three regions: (i) Hindfoot – talus and calcaneus; (ii) Midfoot – navicular, cuboid, and cuneiforms; and (iii) Forefoot – metatarsals and phalanges. Tarsals  The tarsal bones of the foot are organised into three rows: proximal, intermediate, and distal.  Proximal Group  The proximal tarsal bones are the talus and the calcaneus. These comprise the hindfoot, forming the bony framework around the proximal ankle and heel.  https://sketchfab.com/3d-models/foot- bones- 40e73f63fb0146f594f87239192494e4 Tarsals  Talus  The talus is the most superior of the tarsal bones. It transmits the weight of the entire body to the foot. It has three articulations:  Superiorly – ankle joint – between the talus and the bones of the leg (the tibia and fibula).  Inferiorly – subtalar joint – between the talus and calcaneus.  Anteriorly – talonavicular joint – between the talus and the navicular.  The main function of the talus is to transmit forces from the tibia to the heel bone (known as the calcaneus). It is wider anteriorly compared to posteriorly which provides additional stability to the ankle.  Whilst numerous ligaments attach to the talus, no muscles originate from or insert onto it. This means there is a high risk of avascular necrosis as the vascular supply is dependent on fascial structures. Tarsals  Calcaneus  The calcaneus is the largest tarsal bone and lies underneath the talus where it constitutes the heel. It has two articulations:  Superiorly – subtalar (talocalcaneal) joint – between the calcaneus and the talus.  Anteriorly – calcaneocuboid joint – between the calcaneus and the cuboid.  It protrudes posteriorly and takes the weight of the body as the heel hits the ground when walking. The posterior aspect of the calcaneus is marked by calcaneal tuberosity, to which the Achilles tendon attaches. Tarsals Intermediate Group  The intermediate row of tarsal bones contains one bone, the navicular (given its name because it is shaped like a boat).  Positioned medially, it articulates with the talus posteriorly, all three cuneiform bones anteriorly, and the cuboid bone laterally.  On the plantar surface of the navicular, there is a tuberosity for the attachment of part of the tibialis posterior tendon. Tarsals Distal Group  In the distal row, there are four tarsal bones – the cuboid and the three cuneiforms. These bones articulate with the metatarsals of the foot  The cuboid is furthest lateral, lying anterior to the calcaneus and behind the fourth and fifth metatarsals. As its name suggests, it is cuboidal in shape. The inferior (plantar) surface of the cuboid is marked by a groove for the tendon of fibularis longus.  The three cuneiforms (lateral, intermediate (or middle) and medial) are wedge shaped bones. They articulate with the navicular posteriorly, and the metatarsals anteriorly. The shape of the bones helps form a transverse arch across the foot. They are also the attachment point for several muscles:  Medial cuneiform – tibialis anterior, (part of) tibialis posterior, and fibularis longus  Lateral cuneiform – flexor hallucis brevis Metatarsals  The metatarsals are located in the forefoot, between the tarsals and phalanges. They are numbered I-V (medial to lateral).  Each metatarsal has a similar structure. They are convex dorsally and consist of a head, neck, shaft, and base (distal to proximal).  They have three or four articulations:  Proximally – tarsometatarsal joints – between the metatarsal bases and the tarsal bones.  Laterally – intermetatarsal joint(s) – between the metatarsal and the adjacent metatarsals.  Distally – metatarsophalangeal joint – between the metatarsal head and the proximal phalanx. Phalanges  The phalanges are the bones of the toes. The second to fifth toes all have proximal, middle, and distal phalanges. The great toe has only 2; proximal and distal phalanges.  They are similar in structure to the metatarsals, each phalanx consists of a base, shaft, and head. Thank you !