Chapters 6, 7, 8 | University of Florida
Difficulty: Intermediate | Prerequisites: Module 1 (especially tissue types from Chapter 4)
Tags: bones, skeletal tissue, ossification, bone remodelling, skeleton, axial skeleton, appendicular skeleton, joints, synovial joints, fractures, cartilage, EXER 2168, UF, health professions
Module 2 moves from tissue-level organisation into the skeletal system. Chapter 6 covers what bone and cartilage are made of and how they grow, remodel, and repair. Chapter 7 is the anatomy of the skeleton itself: names, markings, and spatial relationships of every bone the exam will test. Chapter 8 then explains how bones meet at joints and the range of movements those joints allow. If you are behind, make sure you understand connective tissue (Chapter 4) before starting here, because bone and cartilage are specialised connective tissues.
Bones are dynamic, living organs that grow, remodel, and repair throughout life. The skeleton is divided into axial (skull, vertebral column, thoracic cage) and appendicular (limbs, girdles) divisions. Joints are classified by structure and function, and synovial joints are the most complex and most commonly tested type.
Tags: cartilage, hyaline cartilage, elastic cartilage, fibrocartilage, compact bone, spongy bone, osteon, osteoblasts, osteoclasts, osteocytes, ossification, endochondral, intramembranous, bone remodelling, fracture repair
Skeletal cartilages
Three types, each with different properties:
Hyaline cartilage: most abundant; provides flexible support with some rigidity (articular cartilage on joint surfaces, tracheal rings, costal cartilages, nasal septum)
Elastic cartilage: very flexible, contains elastic fibres (external ear, epiglottis)
Fibrocartilage: highly compressible, great tensile strength (intervertebral discs, pubic symphysis, menisci of the knee)
All cartilage is avascular, which is why it heals slowly.
Appositional growth
Growth at the outer surface of cartilage, where new matrix is laid down by chondroblasts in the perichondrium. Makes the cartilage wider.
Interstitial growth
Growth from within the cartilage, where chondrocytes divide and secrete new matrix. Makes the cartilage longer.
Functions of bones
Support: the skeleton is the body's structural framework
Protection: shields vital organs (skull protects brain, rib cage protects heart and lungs)
Movement: serve as levers for muscles
Mineral storage: reservoir of calcium and phosphate
Blood cell formation (haematopoiesis): occurs in red bone marrow
Triglyceride (fat) storage: in yellow bone marrow
Hormone production: osteocalcin, involved in regulating blood sugar and energy metabolism
Classifications of bones
By shape: long (femur, humerus), short (carpals, tarsals), flat (sternum, skull bones), irregular (vertebrae, hip bone), sesamoid (patella, formed within tendons).
Compact bone
Dense, smooth-looking bone forming the external layer. The structural unit is the osteon (Haversian system):
Central (Haversian) canal: contains blood vessels and nerves, runs lengthwise
Lamellae: concentric rings of bone matrix around the central canal
Lacunae: small chambers that house osteocytes
Canaliculi: tiny channels connecting lacunae, allowing nutrients and wastes to pass between osteocytes
Perforating (Volkmann's) canals: connect blood vessels between osteons and the periosteum
Spongy (cancellous) bone
Found internally, consists of trabeculae (thin plates/spicules) with open spaces between them. No osteons. Red bone marrow fills the spaces. Trabeculae are oriented along lines of stress for maximum strength with minimum weight.
Chemical composition of bone
Organic components (~35%): collagen fibres and ground substance, provide flexibility and tensile strength
Inorganic components (~65%): hydroite (calcium phosphate) crystals, provide hardness and compression resistance
Think of it this way: collagen is the steel rebar and hydroxyapatite is the concrete. Together they make bone both strong and slightly flexible.
Bone cells
Osteogenic (osteoprogenitor) cells: stem cells that differentiate into osteoblasts
Osteoblasts: bone-building cells that secrete osteoid (unmineralised bone matrix)
Osteocytes: mature bone cells trapped in lacunae; maintain the bone matrix, act as stress sensors
Osteoclasts: large, multinucleated cells that break down (resorb) bone; derived from monocytes (a white blood cell line)
Bone markings
Projections that are sites of muscle/ligament attachment: tuberosity, crest, trochanter, spine, epicondyle, process. Projections that help form joints: head, facet, condyle. Depressions and openings for vessels/nerves: fossa, meatus, foramen, fissure, sinus.
Intramembranous ossification
Bone develops directly from mesenchyme (embryonic connective tissue) without a cartilage precursor. Produces the flat bones of the skull and the clavicle. Osteoblasts cluster in the fibrous membrane and begin secreting osteoid, which mineralises to form bone.
Endochondral ossification
Bone develops by replacing a hyaline cartilage model. This is how most bones of the body form. Key stages:
A hyaline cartilage model forms
A bone collar forms around the diaphysis (shaft)
The primary ossification centre develops in the diaphysis (cartilage calcifies, blood vessels invade, osteoblasts lay down bone)
The medullary cavity forms as osteoclasts break down spongy bone in the centre
Secondary ossification centres appear in the epiphyses (ends)
The epiphyseal plate (growth plate) remains between the diaphysis and epiphysis, allowing lengthwise growth until it ossifies into the epiphyseal line at maturity
Bone remodelling
A continuous process in which osteoclasts resorb old bone and osteoblasts deposit new bone. Regulated by:
Mechanical stress (Wolff's law): bone grows thicker and stronger where stress is applied
Hormones: parathyroid hormone (PTH) stimulates osteoclast activity and calcium release into blood; calcitonin (from the thyroid) inhibits osteoclasts and promotes calcium deposition into bone
Growth hormone and sex hormones also influence bone growth and closure of growth plates
Fracture classification
By position of bone ends: nondisplaced vs. displaced. By completeness: complete vs. incomplete (greenstick). By skin penetration: open (compound, bone pierces skin) vs. closed (simple). Named types include comminuted (shattered), spiral, compression, epiphyseal, and depressed.
Bone repair (fracture healing)
Four stages:
Haematoma formation: blood clot forms at the fracture site
Fibrocartilaginous callus: fibroblasts and chondroblasts bridge the gap with a soft callus of cartilage and collagen
Bony callus: osteoblasts replace the fibrocartilaginous callus with spongy bone
Bone remodelling: compact bone replaces spongy bone at the periphery; the healed area eventually resembles the original bone
Skeletal conditions / homeostatic imbalances
Osteoporosis: loss of bone mass, bones become porous and fragile; most common in postmenopausal women due to declining oestrogen
Osteomalacia / Rickets: soft bones due to inadequate mineralisation (vitamin D deficiency); rickets is the childhood form
Paget's disease: excessive and abnormal bone remodelling, producing thick but structurally weak bone
Diaphysis: the shaft, composed of compact bone surrounding a medullary (marrow) cavity
Epiphyses: the ends, composed of spongy bone covered by a thin shell of compact bone; articular surfaces coated in hyaline (articular) cartilage
Metaphysis: the region between diaphysis and epiphysis, contains the epiphyseal plate in growing bone
Periosteum: fibrous connective tissue membrane covering the external surface (except at joint surfaces); anchors tendons and ligaments, contains osteogenic cells for growth and repair
Endosteum: thin connective tissue lining the medullary cavity and internal surfaces of spongy bone
Bones are not dead, dry sticks. They are living organs with blood supply, nerves, and constant remodelling activity.
Osteoblasts build bone; osteoclasts break it down. Students frequently swap these. Remember: "blasts build, clasts cleave."
The epiphyseal plate is cartilage, not bone. Lengthwise growth happens here. Once it ossifies into the epiphyseal line, no more lengthwise growth occurs.
Compact and spongy bone are not different materials. They are the same tissue arranged differently. Compact bone is dense; spongy bone has open spaces for marrow.
⚠️ Know the stages of endochondral ossification in order and what occurs at each stage.
⚠️ Understand the four stages of fracture repair.
⚠️ Be able to distinguish osteoblasts, osteoclasts, and osteocytes by function.
⚠️ Know the components of the osteon and be able to label a diagram.
⚠️ Wolff's law and the hormonal regulation of bone remodelling (PTH vs. calcitonin) are commonly tested.
True or False: Cartilage is well vascularised. (False, it is avascular)
Fill in the blank: The bone cell responsible for bone resorption is the _______. (Osteoclast)
True or False: Intramembranous ossification uses a hyaline cartilage model. (False, that is endochondral; intramembranous ossification forms bone directly from mesenchyme)
Fill in the blank: According to Wolff's law, bone grows thicker where _______ is applied. (Mechanical stress)
True or False: The periosteum covers the articular surface of a bone. (False, articular cartilage covers joint surfaces; the periosteum covers the rest of the external surface)
Tags: axial skeleton, appendicular skeleton, skull bones, cranium, facial bones, vertebral column, cervical vertebrae, thoracic vertebrae, lumbar vertebrae, thoracic cage, ribs, sternum, pectoral girdle, pelvic girdle, upper limb bones, lower limb bones, os coxae, male vs female pelvis
Axial skeleton
The bones forming the longitudinal axis of the body: skull, vertebral column, and thoracic cage. Total: 80 bones.
Appendicular skeleton
The bones of the limbs and the girdles (pectoral and pelvic) that attach them to the axial skeleton. Total: 126 bones.
The skull has two sets of bones:
Cranial bones (8) – form the cranium, which encloses and protects the brain:
Frontal (1): forms the forehead and superior part of the orbits
Parietal (2): form the superior and lateral walls of the cranium
Temporal (2): form the inferior lateral walls; contain the external acoustic meatus, mastoid process, styloid process, zygomatic process, and the mandibular fossa (TMJ socket)
Occipital (1): forms the posterior and base of the skull; contains the foramen magnum (where the spinal cord exits) and occipital condyles (articulate with the atlas/C1)
Sphenoid (1): butterfly-shaped bone in the middle of the skull base; contains the sella turcica (houses the pituitary gland), greater and lesser wings, and the pterygoid processes
Ethmoid (1): between the orbits; contains the cribriform plate (olfactory nerves pass through), crista galli, and the perpendicular plate (part of the nasal septum)
Facial bones (14):
Maxillae (2): upper jaw; form part of the orbits, nasal cavity, and hard palate
Palatine (2): posterior portion of the hard palate and part of the orbits and nasal cavity
Zygomatic (2): cheekbones
Lacrimal (2): smallest facial bones, medial wall of the orbit; contain the lacrimal fossa (for the tear duct)
Nasal (2): bridge of the nose
Vomer (1): inferior part of the nasal septum
Inferior nasal conchae (2): lateral walls of the nasal cavity; increase surface area for warming and humidifying air
Mandible (1): lower jaw; the only freely movable skull bone
Orbits: formed by seven bones (frontal, sphenoid, zygomatic, maxilla, palatine, lacrimal, ethmoid).
Nasal cavity: bounded by the nasal bones, maxillae, palatine bones, ethmoid (superior and middle conchae, perpendicular plate), vomer, and inferior nasal conchae.
Paranasal sinuses: air-filled cavities in the frontal, sphenoid, ethmoid, and maxillary bones. They lighten the skull and serve as resonance chambers for the voice.
26 bones in the adult:
7 cervical vertebrae (C1 to C7)
12 thoracic vertebrae (T1 to T12)
5 lumbar vertebrae (L1 to L5)
Sacrum (5 fused vertebrae)
Coccyx (3 to 5 fused vertebrae)
Curvatures: cervical and lumbar curves are concave posteriorly (secondary/compensation curves, develop after birth). Thoracic and sacral curves are convex posteriorly (primary curves, present at birth).
Intervertebral discs: fibrocartilage pads between vertebrae. The outer annulus fibrosus (strong ring of fibrocartilage) surrounds the inner nucleus pulposus (gel-like, acts as a shock absorber). A herniated disc occurs when the nucleus pulposus bulges or ruptures through the annulus fibrosus.
Structure of a typical vertebra: body (weight-bearing, anterior), vertebral arch (posterior, formed by pedicles and laminae), vertebral foramen (spinal cord passage), spinous process (posterior projection), transverse processes (lateral projections), superior and inferior articular processes.
Regional features:
Cervical: small body, bifid spinous process, transverse foramina (for vertebral arteries). Atlas (C1) has no body or spinous process, supports the skull with "yes" nodding motion. Axis (C2) has the dens (odontoid process) for "no" rotation.
Thoracic: heart-shaped body, long downward-pointing spinous process, costal facets for rib articulation.
Lumbar: massive body (bears the most weight), short thick spinous process, no costal facets, no transverse foramina.
Composed of the sternum, 12 pairs of ribs, and thoracic vertebrae. Protects the heart, lungs, and great vessels.
Sternum: manubrium (superior, articulates with clavicle), body, and xiphoid process (inferior landmark).
Ribs:
True ribs (1 to 7): attach directly to the sternum via their own costal cartilage
False ribs (8 to 12): do not attach directly to the sternum. Ribs 8 to 10 attach via the costal cartilage of rib 7 (indirect attachment). Ribs 11 and 12 are floating ribs (no anterior attachment at all).
Composed of the clavicle and scapula on each side. Attaches the upper limb to the axial skeleton. Designed for mobility rather than strength (only attachment to the axial skeleton is the sternoclavicular joint).
Clavicle: S-shaped bone, acts as a brace to hold the shoulder joint away from the body. The most commonly fractured bone.
Scapula: flat, triangular bone on the posterior thorax. Key markings: spine of the scapula, acromion (tip of the shoulder, articulates with clavicle), coracoid process, glenoid cavity (shallow socket for the humerus), supraspinous fossa, infraspinous fossa, subscapular fossa.
Humerus: arm bone. Head (articulates with glenoid cavity), greater and lesser tubercles, deltoid tuberosity, capitulum (articulates with radius), trochlea (articulates with ulna), olecranon fossa, medial and lateral epicondyles.
Radius: lateral forearm bone (thumb side). Head, radial tuberosity, styloid process.
Ulna: medial forearm bone (pinky side). Olecranon (forms the elbow point), coronoid process, trochlear notch, styloid process.
Carpals (8), metacarpals (5), phalanges (14): form the wrist, palm, and fingers.
Each hip bone (os coxae) is formed by three fused bones: ilium, ischium, and pubis. They meet at the acetabulum (deep socket for the femoral head). The pelvic girdle is built for strength and weight bearing, in contrast to the mobile pectoral girdle.
Male vs. female pelvis: the female pelvis is wider and shallower, with a larger pelvic inlet and outlet (for childbirth), a wider pubic angle (greater than 100 degrees vs. less than 90 degrees in males), and lighter, thinner bones.
Femur: thigh bone, longest and strongest bone. Head (with fovea capitis), neck, greater and lesser trochanters, linea aspera, medial and lateral condyles, medial and lateral epicondyles, patellar surface.
Patella: sesamoid bone embedded in the quadriceps tendon; protects the knee joint.
Tibia: medial leg bone, weight-bearing. Medial and lateral condyles, tibial tuberosity, anterior crest (shin), medial malleolus (inner ankle bump).
Fibula: lateral leg bone, non-weight-bearing. Head, lateral malleolus (outer ankle bump).
Tarsals (7, including the calcaneus/heel bone and talus), metatarsals (5), phalanges (14): form the ankle, foot, and toes.
The radius is lateral (thumb side) and the ulna is medial (pinky side) in anatomical position. Students often reverse these, especially because when the arm is relaxed at the side with palms forward, the radius appears to be the smaller, less prominent forearm bone.
Floating ribs are still ribs and still articulate with the vertebral column posteriorly. They simply lack an anterior cartilaginous connection to the sternum.
The pelvic girdle is much more stable than the pectoral girdle. This is by design: the pelvis bears weight, while the shoulder sacrifices stability for range of motion.
⚠️ Expect questions asking you to identify specific bones, their markings, and which structures articulate at those markings.
⚠️ Know the regional features that distinguish cervical, thoracic, and lumbar vertebrae.
⚠️ Be able to compare and contrast the pectoral and pelvic girdles in terms of mobility vs. stability.
⚠️ Differences between the male and female pelvis are commonly tested.
⚠️ Know true ribs vs. false ribs vs. floating ribs.
Tags: articulations, fibrous joints, cartilaginous joints, synovial joints, joint classification, joint movements, flexion, extension, rotation, abduction, adduction, shoulder joint, hip joint, knee joint, TMJ, range of motion, ligaments, bursae
Joint (articulation)
The point where two or more bones meet. Joints serve two sometimes competing purposes: allowing movement and providing stability.
Functional classification of joints
Synarthrosis: immovable (skull sutures)
Amphiarthrosis: slightly movable (pubic symphysis, intervertebral discs)
Diarthrosis: freely movable (all synovial joints)
Structural classification of joints
Fibrous joints: bones joined by dense fibrous connective tissue. No joint cavity. Types: sutures (skull), syndesmoses (e.g., interosseous membrane between radius and ulna), gomphoses (tooth in socket).
Cartilaginous joints: bones joined by cartilage. No joint cavity. Types: synchondroses (hyaline cartilage, e.g., epiphyseal plate), symphyses (fibrocartilage, e.g., pubic symphysis, intervertebral joints).
Synovial joints: bones separated by a fluid-filled joint cavity. Most complex and most movable.
Synovial joint features
Articular (hyaline) cartilage on the bone ends
Joint (articular) cavity filled with synovial fluid
Articular capsule: outer fibrous capsule (dense irregular connective tissue) and inner synovial membrane (secretes synovial fluid)
Synovial fluid: viscous fluid that lubricates, nourishes articular cartilage, and absorbs shock
Reinforcing ligaments: intrinsic (thickenings of the capsule) or extrinsic (external to the capsule)
Additional features in some joints: menisci (fibrocartilage discs), bursae (fluid-filled sacs reducing friction), tendon sheaths, fat pads, labra (fibrocartilage lips deepening a socket)
Factors influencing stability of synovial joints
Shape of the articular surfaces (deeper socket = more stable)
Number and position of ligaments
Muscle tone of surrounding muscles (the most important stabilising factor for most joints)
Movements of synovial joints
Gliding, angular movements (flexion, extension, hyperextension, lateral flexion, abduction, adduction, circumduction), rotation (medial/lateral), and special movements (supination, pronation, dorsiflexion, plantar flexion, inversion, eversion, protraction, retraction, elevation, depression, opposition).
Types of synovial joints
Plane (gliding): flat articular surfaces, short gliding movements (intercarpal joints)
Hinge: movement in one plane, flexion/extension only (elbow, knee, ankle)
Pivot: rotation around a single axis (atlas/axis joint, proximal radioulnar joint)
Condyloid (ellipsoid): oval surface fits into an oval depression, biaxial movement (metacarpophalangeal/knuckle joints, wrist)
Saddle: each surface is concave and convex, biaxial (carpometacarpal joint of the thumb)
Ball-and-socket: most freely movable, multiaxial (shoulder, hip)
Temporomandibular joint (TMJ): between the mandibular condyle and the mandibular fossa of the temporal bone. Modified hinge joint. Allows depression/elevation (opening/closing the mouth), protraction/retraction, and lateral excursion (side-to-side grinding). Contains an articular disc.
Glenohumeral (shoulder) joint: ball-and-socket joint between the humeral head and the glenoid cavity of the scapula. Most freely movable joint in the body but also the most commonly dislocated, because the glenoid cavity is shallow. Stability comes mainly from the rotator cuff muscles and the glenoid labrum.
Humeroulnar (elbow) joint: hinge joint between the trochlea of the humerus and the trochlear notch of the ulna. Very stable due to the shape of the articulating surfaces and strong collateral ligaments.
Femoroacetabular (hip) joint: ball-and-socket joint between the femoral head and the acetabulum of the os coxae. More stable than the shoulder because the acetabulum is deep and reinforced by a strong fibrocartilaginous labrum, thick capsular ligaments, and surrounding muscle.
Tibiofemoral (knee) joint: the largest and most complex joint. Primarily a hinge joint (modified). Contains the medial and lateral menisci, anterior cruciate ligament (ACL), posterior cruciate ligament (PCL), and medial and lateral collateral ligaments.
The shoulder prioritises mobility (shallow socket, loose capsule, huge range of motion) at the cost of stability (frequent dislocations). The hip prioritises stability (deep socket, strong ligaments, significant muscle support) while still allowing multiaxial movement but with a smaller range than the shoulder.
Valgus stress (force from the lateral side): can damage the medial collateral ligament (MCL), medial meniscus, and ACL (the "unhappy triad")
Varus stress (force from the medial side): can damage the lateral collateral ligament (LCL)
Hyperextension or sudden deceleration: common ACL injury mechanism
PCL injuries: often from a direct blow to the anterior tibia (e.g., dashboard injury)
Students often think "fibrous joint" means it does not move at all. Syndesmoses (a type of fibrous joint) do allow slight movement.
The knee is not a simple hinge. It allows a small amount of rotation when flexed and is classified as a modified hinge joint.
Ligaments connect bone to bone; tendons connect muscle to bone. This is one of the most commonly confused pairs in anatomy.
The ACL and PCL are named for where they attach on the tibia, not the femur. The ACL attaches to the anterior intercondylar area of the tibia.
Understanding knee injury mechanics is essential for sports medicine and rehabilitation. The "unhappy triad" is a classic athletic injury pattern seen when a planted foot is hit from the lateral side (common in football/rugby). Shoulder dislocations are the most common major joint dislocation, and understanding the shallow glenoid cavity explains why.
⚠️ Be able to classify a joint by structure and function when given a description.
⚠️ Know the six types of synovial joints and be able to give an example of each.
⚠️ The five specific joints listed on the topic sheet (TMJ, shoulder, elbow, hip, knee) will be tested. Know their type, key ligaments, and how their structure relates to their function.
⚠️ Compare and contrast the shoulder and hip joints in terms of stability and mobility.
⚠️ Know the ligaments of the knee and what forces injure each one.
True or False: A symphysis is a type of synovial joint. (False, it is a cartilaginous joint)
Fill in the blank: The most important factor stabilising most synovial joints is _______. (Muscle tone)
True or False: The shoulder joint is more stable than the hip joint. (False, the hip is more stable)
Fill in the blank: Ligaments connect _______ to _______. (Bone to bone)
True or False: The ACL is named for its attachment on the femur. (False, it is named for its tibial attachment)
Q: What are the four stages of fracture repair, in order?
A: (1) Haematoma formation, (2) fibrocartilaginous callus formation, (3) bony callus formation, (4) bone remodelling.
Q: Distinguish between intramembranous and endochondral ossification.
A: Intramembranous ossification forms bone directly from mesenchyme without a cartilage model (produces flat bones of the skull and the clavicle). Endochondral ossification replaces a hyaline cartilage model with bone tissue (produces most bones of the body).
Q: Name three features that distinguish cervical vertebrae from thoracic and lumbar vertebrae.
A: Cervical vertebrae have transverse foramina (for vertebral arteries), a bifid spinous process (C2 to C6), and a relatively small, oval body. Thoracic vertebrae have costal facets and long, downward-pointing spinous processes. Lumbar vertebrae have massive bodies and short, thick spinous processes.
Q: Why is the shoulder joint so prone to dislocation?
A: The glenoid cavity of the scapula is shallow, providing minimal bony support. The joint capsule is loose to permit a wide range of motion. Stability depends largely on the rotator cuff muscles and the glenoid labrum, which can be overwhelmed by strong forces.
Q: A football player is tackled from the lateral side while his foot is planted. Which structures of the knee are most at risk?
A: The medial collateral ligament (MCL), medial meniscus, and anterior cruciate ligament (ACL). This combination is known as the "unhappy triad."
Q: Explain Wolff's law and give an example.
A: Wolff's law states that bone grows and remodels in response to the mechanical stresses placed upon it. Bone deposited where stress is applied becomes thicker and stronger; bone resorbed where stress is absent becomes thinner. Example: the racket arm of a tennis player develops thicker cortical bone than the non-dominant arm.
Q: What is the difference between true ribs, false ribs, and floating ribs?
A: True ribs (1 to 7) attach directly to the sternum via their own costal cartilage. False ribs (8 to 12) do not attach directly to the sternum; ribs 8 to 10 connect indirectly via the costal cartilage of rib 7. Floating ribs (11 and 12) have no anterior attachment at all.
The skeletal system connects directly to the muscular system (Module 3): muscles attach to bone markings via tendons and pull on bones to produce movement at joints. The lever systems covered in Chapter 10 depend on understanding the joint types from Chapter 8 and the bone markings from Chapter 7. Bone remodelling and calcium homeostasis also tie into the endocrine system (PTH from the parathyroid glands, calcitonin from the thyroid) and into cell biology (osteoblasts and osteoclasts are living cells that respond to signals). The nervous system (Module 4) connects through sensory nerves in the periosteum and pain perception following fractures.
Skeletal system study guide, EXER 2168 module 2, bones and skeletal tissues, osteon Haversian system, osteoblast osteoclast osteocyte, endochondral ossification steps, intramembranous ossification, bone remodelling Wolff's law, fracture repair stages, axial skeleton bones, appendicular skeleton bones, skull bones cranial facial, vertebral column curvatures, cervical thoracic lumbar vertebrae, thoracic cage ribs sternum, pectoral girdle scapula clavicle, pelvic girdle os coxae, male female pelvis differences, upper limb bones humerus radius ulna, lower limb bones femur tibia fibula, joint classification, synovial joint features, shoulder vs hip joint, knee ligaments ACL MCL, unhappy triad, TMJ temporomandibular joint