CHAPTER 5: THE SKELETAL SYSTEM

Classification of Bones 206 bones Compact bone – dense, looks smooth and

homogeneous Spongy bone – composed of small needle-

like pieces of bone and lots of open space

SHAPES:Long bones longer than they are wide, shaft with heads

at both ends, compact bone ex: all the bones of the limbs except the

patella (kneecap) and the wrist and ankle bones

Short bones cube-shaped and contain mostly spongy

bone ex: bones of the wrist and ankle, sesamoid

bones – form within the tendons, patellaFlat bones thin, flattened, curved two thin layers of compact bone

sandwiching a layer of spongy bone between them

ex: skull, ribs, sternum (breast bone)Irregular bones ex: vertebrae (make up the spinal column)

and the hip bones

Structure of a Long BoneGross Anatomy Diaphysis – shaft, makes up most of the

bone’s length, composed of compact bone Periosteum – fibrous connective tissue

membrane that covers and protects the diaphysis

Perforating/Sharpey’s fibers – secure periosteum to the underlying bone

Epiphyses – ends of the long bone; each consists of a thin layer of compact bone enclosing an area filled with spongy bone

Articular cartilage – covers external surface of epiphyses; glassy hyaline cartilage;

provides a smooth surface that decreases friction at joint surfaces

Epiphyseal line – thin line of bony tissue spanning the epiphysis that looks a bit different from other bones (In adults)

Epiphyseal plate – flat plate of hyaline cartilage; seen in a young, growing bone; cause the lengthwise growth of a long bone

By the end of puberty, when hormones inhibit a long bone growth, epiphyseal plates have been completely replaced by bone leaving epiphyseal lines to mark their previous location.

Yellow marrow/Medullary cavity – cavity of shaft, primarily a storage area for adipose tissue (adults)

Red Marrow – cavity of shaft that forms blood cells (infants). Confined to cavities in the spongy bone of flat bones and the epiphyses of some long bones (adults)

Bone markings – reveal where muscles, tendons, and ligaments were attached and where blood vessels and nerves passed

2 CATEGORIES: Projections (grow out from the bone surface) and Depressions (indentations in the bone; all the terms beginning with T are projections, F are depressions except facet

Microscopic Anatomy Spongy bone has a spiky, open appearance.

Compact bone appears to be very dense. Compact bone is riddles with passageways

carrying nerves, blood vessels, and the like, which provide the living bone cells with nutrients and a route for waste disposal

Osteocytes – mature bone cells found within the matrix in tiny cavities called lacunae arranged in concentric circles called lamellae around central (Haversian) canals

Osteon or Haversian system – complex consisting of central canal and matrix rings

Central canals run lengthwise through the bony matrix, carrying blood vessels and nerves to all areas of the bone

Canaliculi – tiny canals that radiate outward from the central canals to all lacunae; form

a transportation system that connects all the bone cells to the nutrient supply through the hard bone matrix

The communication pathway from the outside of the bone to its interior is completed by perforating (Volkmann’s) canals which run into the compact bone at right angles to the shaft.

Bone has the ability to resist tension and other forces acting on it. Calcium salts give bone its hardiness, which resists compression

The organic parts (collagen and fibers) provide for bones flexibility and great tensile strength

Bone formation, growth, remodeling The skeleton is formed from two of the

strongest and most supportive tissues in the body – cartilage and bone

Cartilage remains only in isolated areas (bridge of the nose, parts of the ribs, joints)

Ossification – bone formation.

MAJOR PHASES: ← - first, the hyaline cartilage model is

completely covered with bone matrix by bone-forming cells called osteoblasts.

- the enclosed hyaline cartilage model is digested away, opening up a medullary cavity within the newly formed bone

- by birth or shortly after, most hyaline cartilage models have been converted to bone except articular cartilages and the epiphyseal plates

- old cartilage abutting the internal face of the articular cartilage and the medullary cavity is broken down and replaced by bony matrix

- osteoblasts widen add bone tissue to the external face of the diaphysis as osteoclasts in the endosteum remove bone from inner face of the diaphysis wall; thus the circumference of the long

bone expands and the bone widens (appositional growth)

- process of long-bone growth is controlled by growth hormone and sex hormones.

bone is a dynamic and active tissue; remodeled continually in response to changes in two factors: (1) calcium levels in the blood and (2) pull of gravity and muscles on the skeleton

PTH activates osteoclasts – giant bone-destroying cells in the bones that break down bone matrix and release calcium ions into the blood

When blood calcium levels are too high (hypercalcemia), calcium is deposited in bone matrix as hard calcium salts

Bone remodeling – essential if bones are to retain normal proportions and strength during long-bone growth as the body increases in size and weight

Bones of bedridden or physically inactive people tend to lose mass and to atrophy because they are no longer subjected to stress

PTH determines when bone is to be broken down or formed in response to the need for more or fewer calcium ions in the blood

Stresses of muscle pull and gravity acting on skeleton determine where bone matrix is to be broken down or formed so that the skeleton can remain as strong and vital as possible

Reduction – realignment of the broken bone ends. Closed reduction – bone ends are coaxed back into their normal position by the physician’s hands. Open Reduction – Surgery is performed and the bone ends are secured together with pins or wires then immobilized by a cast to allow the healing process to begin

4 MAJOR EVENTS IN REPAIR OF FRACTURES1. A hematoma forms – blood vessels

are ruptured. Hematoma – blood-filled swelling. Bone cells deprived of nutrition die.

2. The break is splinted by a fibrocartilage callus – an early event of tissue repair is the growth of new capillaries into the clotted blood at the site of the damage and disposal of dead tissue by phagocytes. Connective tissue calls of various types form a mass of repair tissue (fibrocartilage callus) that contains some cartilage matrix, some bony matrix, and collagen fibers and acts to splint the broken bone, closing the gap.

3. The bony callus forms – fibrocartilage callus is gradually replace by one made of spongy bone, the bony callus

4. Bone remodeling occurs – Bony callus is remodeled in response to the mechanical stresses placed on it to form a strong permanent “patch” at the fracture site

Skull Formed by 2 sets of bones = cranium

(encloses and protects the fragile brain tissue) and facial bones (hold the eyes in an anterior position and allow the facial muscles to show our feelings through smiles or frowns)

Cranium Boxlike, composed of 8 large flat bones (2

paired bones = parietal and temporal)1. Frontal bone- forms the forehead, the bony

projections under the eyebrows, superior part of each eye’s orbit

2. Parietal bones- form most of the superior and lateral

walls of the cranium- meet in the midline of the skull at the

sagittal suture and form the coronal

suture, where they meet the frontal bone

3. Temporal bones- lie inferior to the parietal bones; they

join them at the squamous sutures.Bone markings: External acoustic meatus – canal

that leads to the eardrum and the middle ear; route where sound enters the ear

Styloid process – sharp, needle-like projection; inferior to the external auditory meatus; neck muscles use this as an attachment point

Zygomatic process – tiny bridge that joins with the cheek bone anteriorly

Mastoid process – full of air cavities, rough projection posterior and inferior to the external acoustic meatus. Provides an attachment site for some muscles of the neck; mastoiditis – Mastoid sinuses are near the middle ear and the brain that may become infected

Jugular foramen – allows passage of the jugular vein (largest vein of the head) which drains the brain. (internal acoustic meatus – anterior to it in the cranial cavity which transmits CN 7&8. Carotid canal – anterior to it on the skull’s inferior aspect through which the internal carotid artery runs, supplying blood to brain)

4. Occipital bone- most posterior bone of the cranium;

forms the floor and back wall of the skull; joins the parietal bones anteriorly at the lambdoid suture. Foramen magnum – base of occipital bone, large opening; surrounds the lower part of the brain and allows the spinal cord to connect with the brain. Occipital condyles – lateral to foramen magnum

on each side, rockerlike; rest on the first vertebra of the spinal column

5. Sphenoid bone- Butterfly-shaped; spans the width of

the skull and forms part of the floor of the cranial activity

- sella turcica (Turk’s saddle) – forms a snug enclosure for the pituitary gland

- Foramen ovale – large oval opening in line with the posterior end of the sella turcica that allows fibers of CN5 to pass to the chewing muscles of the lower jaw

- 2 openings: optic canal (allows the optic nerve to pass to the eye) and superior orbital fissure (CN 3,4,6 controlling eye movements pass)

- Sphenoid sinuses – central part, riddled with air cavities

6. Ethmoid bone- irregularly shaped and lies anterior to

sphenoid; forms the roof of nasal cavity and part of the medial walls of the orbits

- crista galli – superior surface, “cock’s comb”; the outermost covering of the brain attaches to this projection; cribriform plates – each side of the crista galli are these many small holes; allow nerve fibers carrying impulses from the olfactory receptors to reach the brain

- Superior and middle nasal conchae – extensions; form part of the lateral walls of the nasal cavity; increase the turbulence of air flowing through nasal passages

Facial Bones 14 bones compose the face (12 paired;

mandible and vomer are single)

1. Maxillae

- The 2 maxillary bones fuse to form the upper jaw, “keystone” bones of the face

- All facial bones, except the mandible, join the maxillae

- Carry the upper teeth in the alveolar margin

- Palatine process: extensions of the maxillae that form the anterior part of the hard palate of the mouth

- Contain sinuses which drain into the nasal passages; these paranasal sinuses lighten the skull bones and amplify the sounds we make as we speak

2. Palatine bones- Lie posterior to the palatine

processes of the maxillae- Cleft palate: faiure of palatine

bones/processes to fuse medially3. Zygomatic bones

- Cheekbones; good-sized portion of the lateral walls of the orbits

4. Lacrimal bones- Fingernail-sized bones forming part

of the medial walls of each orbit- Each lacrimal has a groove that

serves as a passageway for tears5. Nasal bones

- Small rectangular bones forming the bridge of the nose are the nasal

6. Vomer bone- Single bone in the median line of

the nasal cavity- Vomer = “plow”; the bone’s shape- Forms most of the bony nasal

septum7. Inferior nasal conchae

- Thin, curved bones projecting medially from the lateral walls of the nasal cavity

8. Mandible- Lower jaw; largest and strongest

bone of the face

- Joins the temporal bones on each side of the face, forming the only freely movable joints in the skull

- Horizontal part of the mandible (body) forms the chin; two upright bars of bone (rami) extend from the body to connect the mandible with the temporal bone; the lower teeth lie in the alveoli (sockets) in the alveolar margin at the superior edge of the mandibular body

The Hyoid Bone Closely related to the mandible and

temporal bones; the only bone of the body that does not articulate directly with any other bone

Suspended in the midneck region about 2cm above the larynx

Horseshoe-shaped, with a body and two pairs of horns (cornua), the hyoid bone serves as a movable base for the tongue and as an attachment point for neck muscles that raise and lower the larynx when we swallow and speak

Fetal Skull Adults skull represents only one-eighth of

the total body length, whereas that of a newborn infant is one-fourth as long as its entire body

When a baby is born, its skeleton is still unfinished

Fontanels – fibrous membranes connecting the cranial bones

Rhythm of baby’s pulse can be felt in these “soft spots”

The largest fontanel is the diamond shaped anterior fontanel; The fontanels allow the fetal skull to be compressed slightly during birth. Because they are flexible, they allow the infant’s brain to grow during the later part of the pregnancy and early infancy

Fontanels are gradually turned into bone during early part of infancy; can no longer be felt by 22-24 months after birth

Vertebral Column Spine; Axial support of the body; extends

from the skull, which it supports, to the pelvis, where it transmits weight of the body to the lower limbs

26 irregular bones connected and reinforced by ligaments in such a way that a flexible, curved structure results

Before birth: 33 separate bones called vertebrae; 9 of these eventually fuse to form the two composite bones (sacrum and coccyx); of the 24 single bones, the 7 vertebrae of the neck are cervical vertebrae, the next 12 are the thoracic vertebrae, and the remaining 5 supporting the lower back are lumbar vertebrae

Individual vertebrae are separated by pads of flexible fibrocartilage – intervertebral discs – that cushion the vertebrae and absorb shocks while allowing the spine flexibility

In a young person, the discs have high water content and are spongy and compressible. As a person ages, the water content of the discs decreases and becomes harder and less compressible

The discs and the S-shaped structure of the vertebral column work together to prevent shock to the head when we walk or run and make the body trunk flexible

Primary curvatures – spinal curvatures in the thoracic and sacral region; present when we are born; the 2 primary curvatures produce the C-shaped spine of the newborn baby

Secondary curvatures – curvatures in the cervical and lumbar regions; develop some time after birth. In adults, this allows us to center our body weight on our lower limbs with minimum effort; The cervical curvature appears when a baby begins to raise its head, and lumbar curvature develops when the baby begins to walk

Common features of vertebrae:- Body/Centrum: disclike, weight-

bearing part of the vertebra facing anteriorly in the vertebral column

- Vertebral arch: formed from the joining of all posterior extensions (laminae and pedicles) from the vertebral body

- Vertebral foramen: canal where spinal cord passes

- Transverse Processes: two lateral projections from vertebral arch

- Spinous process: single projection arising from the posterior aspect of vertebral arch (fused laminae)

- Superior & inferior articular processes: paired projections lateral to the vertebral foramen; allow vertebra to form joints with adjacent vertebrae

Cervical Vertebrae (7) Form the neck region of the spine First two: atlas and axis; different because

they perform functions not shared by other cervical vertebrae

Atlas – no body; superior surfaces of its transverse processes contain large depressions that receive occipital condyles of the skull; nod “yes”

Axis – pivot for the rotation of atlas; has a large upright process (dens) that acts as a pivot point; rotate head from side to side, “no”

Smallest, lightest vertebrae; spinous processes are short and divided into two branches

Transverse processes of cervical vertebrae contain foramina where vertebral arteries pass on their way to the brain above

Thoracic Vertebrae (12) Larger than cervical vertebrae; only

vertebrae to articulate with the ribs Body is heart-shaped and has 2 costal facets

on each side (receive head of ribs) The two transverse processes of each

thoracic vertebra articulate with the nearby knoblike tubercles of the ribs

Spinous process: long and hooks sharply downward

Lumbar Vertebrae (5) Have massive, blocklike bodies Spinous processes: hatchet-shaped Sturdiest of the vertebrae

Sacrum Formed by fusion of 5 vertebrae Superiorly, it articulates with L5, and

inferiorly it connects with the coccyx Alae – winglike; articulate laterally with the

hip bones forming the sacroiliac joints Forms the posterior wall of the pelvis Its posterior midline surface is roughened

by the median sacral crest, the fused spinous processes of the sacral vertebrae; flanked laterally by the posterior sacral foramina

vertebral canal continues inside the sacrum as the sacral canal and terminates in a large inferior opening called sacral hiatus

Coccyx formed from the fusion of 3-5 tiny,

irregularly shaped vertebrae; “tailbone”

Thoracic Cage Bony thorax; forms a protective, cone-

shaped cage of slender bones around the organs of the thoracic cavity (heart, lungs, major blood vessels)

Sternum Breastbone; flat bone and the result of

fusion of 3 bones – manubrium, body, xiphoid process.

Attached to the first 7 pairs of ribs 3 important body landmarks

1. Jugular notch – concave upper border of the manubrium; can be palpated easily; generally at the 3rd level of thoracic vertebra

2. Sternal angle – results when the manubrium and body meet at a slight angle to each other, so that a transverse ridge is formed at the level of 2nd ribs; provides a handy reference point for counting ribs to locate the

second intercostals space for listening to certain heart valves

3. Xiphisternal joint – point where the sterna body and xiphoid process fuse; lies at the level of the 9th thoracic vertebra

Sternal puncture – needle is inserted into the marrow of sternum, and sample is withdrawn

Ribs 12 pairs from the walls of the bony thorax True ribs – first 7 pairs, attach directly to

sternum by costal cartilages False ribs – next 5 pairs, either attach

indirectly to sternum or are not attached to sternum at all

Floating ribs – last 2 pairs of false ribs lack the sternal attachments

Intercostal spaces (spaces between ribs) are filled with the intercostals muscles that aid in breathing

Composed of 126 bones of the limbs, pectoral and pelvic girdles, which attach the limbs to the axial skeleton

Bones of the Shoulder Girdle Each shoulder/pectoral girdle consists of 2

bones – clavicle and scapula Clavicle – collarbone; slender, doubly

curved bone; attaches manubrium of the sternum medially and the scapula laterally where it helps form the shoulder joint; acts as a brace to hold the arm away from the top of the thorax and helps prevent shoulder dislocation

Scapula – shoulder blades, triangular and are commonly called “wings” because they flare when we move our arms posteriorly; each scapula has a flattened body and 2 important processes – the acromion (enlarged end of the spine of the scapula) and the beaklike coracoid process

Acromion connects with the clavicle laterally at the acromioclavicular joint. The coracoid process points over the top of the shoulder and anchors some of the muscles of the arm. Suprascapular notch – medial to coracoid process, nerve passageway

Scapula not directly attached to axial skeleton; loosely held in place by trunk muscles. 3 borders: superior, medial, lateral. 3 angles: superior, inferior, lateral.

Glenoid cavity – shallow socket that receives the head of the arm bone; lateral angle

Shoulder girdle is very light and allows the upper limb to have free movement. Factors:

- Each shoulder girdle attaches to axial skeleton at only one point: Sternoclavicular joint

- Loose attachment of the scapula allows it to slide back and forth against thorax as muscles act

- Glenoid cavity is shallow; shoulder joint is poorly reinforced by ligaments

Drawback: shoulder girdle is easily dislocated

Bones of the Upper Limbs 30 separate bones Foundations of arm, forearm, hand

Arm Humerus – typical long bone; at its proximal

end is a rounded head that fits into the shallow glenoid cavity of the scapula

Anatomical neck – slight constriction inferior to head

Anterolateral to the head are 2 bony projections, greater and lesser tubercles (sites of muscle attachment), separated by intertubecular sulcus

Surgical neck – most frequently fractured part of the humerus, distal to tubercles

Deltoid tuberosity – large, fleshy, deltoid muscle of the shoulder attaches; midpoint of shaft; rough ended

Radial groove – runs obliquely down the posterior aspect of the shaft; marks the course of radial nerve

Trochlea – distal end of the humerus is this medial; looks like a spool, and the lateral ball-like capitulum. Both articulate with bones of the forearm

Above the torchlea anteriorly is a depression called coronoid fossa; posterior surface is the olecranon fossa. These 2 depressions flanked by medial and lateral epicondyles, allow the processes of ulna to move freely when the elbow is bent and extended

Forearm In anatomical position, radius is the lateral

bone (thumb side of the forearm) Styloid process – both radius and ulna Radial tuberosity – tendon of the biceps

muscle attaches In anatomical position, ulna is the medial

bone (on the little finger side) Coronoid process (anterior of ulna);

olecranon process (posterior of ulna);separated by the trochlear notch; These 2 processes grip the trochlea of the humerus in a pliers-like joint

Hand Carpal bones (8) – arranged in 2 irregular

rows of 4 bones each; form the part of the hand called the carpus (wrist); bound together by ligaments that restrict movements between them

Palm of the hand consists of the metacarpals. Phalanges – bones of the fingers; each hand contains 14 phalanges

Bones of the Pelvic Girdle Pelvic girdle – formed by 2 coxal bones

called hip bones With sacrum and coccyx, the hip bones

form the bony pelvis Bones are large and heavy, attached

securely in the axial skeleton; bearing

weight is the most important function of the girdle

Each hip bone is formed by the fusion of 3 bones: ilium, ischium, pubis

Ilium – connects posteriorly with the sacrum at the sacroiliac joint, is a large flaring bone that form most of the hip bone

Iliac crest – important landmark to those who give injections; ends anteriorly in the anterior superior iliac spine and posteriorly in the posterior superior iliac spine

Ischium – “sit-down bone”; forms the most inferior part of the coxal bone

Ischial tuberosity – roughened area that receives body weight when you are sitting

Ischial spine – superior to the tuberosity; important landmark for pregnant women because it narrows the outlet of the pelvis through which the baby must pass during birth

Greater Sciatic notch – allows blood vessels and the large sciatic nerve to pass from the pelvis posteriorly into the thigh (keep away from injection)

Pubis – most anterior part of a coxal bone Obturator foramen – an opening that

allows blood vessels and nerves to pass into the anterior part of the thigh; pubic bones of each hip bone fuse anteriorly to form a cartilaginous joint, the pubic symphysis

Acetabulum – “vinegar cup”; deep socket where the ilim, ischium, and pubis fuse; receives the head of thigh bone

Bony pelvis divided into 2 regions: false pelvis (superior to the true pelvis, area medial to the flaring portions of the ilia); true pelvis (surrounded by bone and lies inferior to the flaring parts of the ilia and pelvic brim

Bones of the Lower Limbs Carry out total body weight when we are

erect Bones are much thicker than upper limbs

Thigh

Femur – thigh bone; only bone in the thigh; heaviest and strongest bone in the body

Its proximal end has a ball-like head, neck, and greater and lesser trochanters

These markings and the gluteal tuberosity, located in the shaft, all serve as sites for muscle attachment

Femur slants medially as it runs downward to join with the leg bones; brings knees in line with the body’s center of gravity

Distally on the femur are the lateral and medial condyles (articulate with the tibia below); posteriorly these condyles are separated ny the deep intercondylar fossa; anteriorly on the distal femur is the smooth patellar surface which forms a joint with the patella

Leg Tibia – shinbone; larger and more medial;

medial and lateral condyles articulate with the distal end of the femur to form the knee joint; patellar ligament attaches to the tibial tuberosity (roughened area on the antereior tibial surface); medial malleolus – forms inner bulge of the ankl; anterior border – anterior surface of tibia with sharp ridge, unprotected by muscles

Fibula – lies alongside the tibia and forms joints; no part in forming the knee joint; lateral malleolus – distal end of fibula that forms outer part of ankle

Foot Tarsals, metatarsals, phalanges 2 functions: supports body weight and

serves as a lever that allows us to propel our bodies forward when we walk and run

Tarsus – forming posterior half of the foot; composed of 7 tarsal bones; body weight is carried mostly by the 2 largest tarsals: calcaneus (heel bone) and talus (ankle)

5 metatarsals from the sole, 14 phalanges form the toes

Bones in the foot are arranged to form 3 strong arches: 2 longitudinal, 1 transverse

Ligaments bind the foot bones together; tendons help hold bones firmly in the

arches position but still allow a certain amount of give or springiness; weak arches are “fallen arches” or “flat feet”

Articulations; 2 functions: hold bones together and give the rigid skeleton mobility

Classified in 2 ways: functionally and structurally

Functional classification focuses on the amount of movement the join allows. Synarthroses – immovable joints; amphiarthroses – slightly movable joints; diathroses – feely movable joints

Structurally, there are fibrous, cartilaginous, synovial joints; based on whether fibrous tissue, cartilage, or a joint cavity separates the bony regions at the joint

Fibrous Joints Bones are united by fibrous tissue Ex: sutures of skull In sutures, the irregular edges of the bones

interlock and are bound tightly together by connective tissue fibers, allowing essentially no movement

Syndesmoses – connecting fibers are longer than those of sutures; joint has more “give”; joint connecting distal ends of the tibia and fibula

Cartilaginous Joints Bone ends are connected by cartilage Ex: slightly movable; pubic symphysis of

pelvis and intervertebral joints of spinal column where articulating bone surfaces are connected by pads of fibrocartilage

Hyaline cartilage epiphyseal plates of growing long bones

Cartilaginous joints between the first ribs and sternum

Synovial Joints Joints in which the articulating bone ends

are separated by a joint cavity containing synovial fluid; account for all joints of the limbs

4 distinguishing features:1. Articular cartilage – covers the ends of

bones forming the joint2. Fibrous articular capsule – joint

surfaces are enclosed by a sleeve or capsule of fibrous connective tissue; capsule is lined with a smooth synovial membrane

3. Joint cavity – articular capsule encloses a cavity which contains lubricating synovial fluid

4. Reinforcing ligaments – fibrous capsule is usually reinforced with ligaments

Bursae – flattened fibrous sacs lined with synovial membrane and containing a thin film of synovial fluid

Tendon Sheath – elongated bursa that wraps completely around a tendon subjected to friction

Types of Synovial Joints Based on Shape Plane joint

- articular surfaces are flat, short slipping or gliding movements are allowed

- movements of plane joints are nonaxial

- Ex: intercarpal joints of wrist

Hinge joint- cylindrical end of one bone fits into

a trough-shaped surface on another bone

- Angular movement is allowed in just one plane

- Ex: elbow joint, ankle joint, joints between phalanges

- Unaxial; allow movement around one axis only

Pivot joint

- Rounded end of one bone fits into a sleeve or ring of bone

- Unaxial joints- Ex: proximal radioulnar joint and

joint between the atlas and the dens

Condyloid joint- “knuckle-like”; egg shaped articular

surface of one bone fits into an oval concavity in another

- Allow the moving bone to travel from side to side and back and forth, but bone cannot rotate around its long axis

- Movement occurs in 2 axes, biaxial- Ex: knuckle joints

Saddle joints- Each articular surface has both

convex and concave areas like a saddle

- Biaxial joints; allow the same movements as condyloid joints

- Ex: carpometacarpal joints in the thumb

Ball-and-socket joints- spherical head of one bone fits into

a round socket in another- multiaxial joints; allow movement

in all axes; most freely moving synovial joints

- Ex: Shoulder and hips