Summary lab

Skeleton functions (4)

Support/protect organs; provide levers for muscle movement; store calcium/lipids/minerals; house stem cells for hematopoiesis

Axial vs. appendicular skeleton

Axial (80 bones): skull, vertebral column, thoracic cage; Appendicular (126 bones): pectoral girdle, pelvic girdle, upper and lower limbs

Bone composition: hardness vs. flexibility

Hardness = inorganic calcium salts (hydroxyapatite) in ground substance; Flexibility = collagen protein fibers

Rickets vs. osteogenesis imperfecta

Rickets: soft/flexible bones from demineralization (vitamin D deficiency → low Ca²⁺/PO₄); OI: brittle bones from defective collagen

Cartilage types and locations

Hyaline: nasal bridge, costal cartilages, articular surfaces; Fibrocartilage: intervertebral discs, pubic symphysis; Elastic: external ear

Bone marking — foramen

Rounded passageway for blood vessels and/or nerves

Bone marking — fossa

Shallow depression

Bone marking — process/tuberosity/tubercle/crest

All are projections; tuberosity = rough, large; tubercle = small, rounded; crest = prominent ridge; process = general projection

Bone marking — condyle vs. facet vs. trochlea

Condyle = smooth rounded articular surface; facet = small flat articular surface; trochlea = grooved pulley-shaped articular surface

Bone marking — meatus/canal/sinus

Meatus = opening of a canal; canal = tunnel/duct; sinus = air-filled chamber within a bone

Skull total

22 bones: 8 cranial + 14 facial

8 cranial bones

Frontal (1), Parietal (2), Temporal (2), Occipital (1), Sphenoid (1), Ethmoid (1)

14 facial bones

Mandible (1), Maxilla (2), Nasal (2), Zygomatic (2), Palatine (2), Lacrimal (2), Inferior nasal concha (2), Vomer (1)

4 skull sutures

Coronal: frontal–parietal; Sagittal: parietal–parietal; Squamous: parietal–temporal; Lambdoid: occipital–parietal/temporal

Frontal bone markings

Supraorbital foramen (CN V branch + artery); glabella (smooth area between eyebrows); forms forehead and superior orbit

Temporal bone markings

External acoustic meatus (ear canal); mastoid process (neck muscle attachment; air cells drain to middle ear); styloid process (muscle attachment); zygomatic process; carotid canal (internal carotid artery); internal acoustic meatus (CN VII + VIII); jugular foramen (CN IX, X, XI + internal jugular vein)

Occipital bone markings

Foramen magnum (spinal cord + CN XI + vertebral arteries); occipital condyles (articulate with atlas/C1); external occipital protuberance

Sphenoid bone — key facts

Keystone bone (articulates with ALL other cranial bones); bat-shaped; forms lateral skull + posterior orbit + cranial floor

Sphenoid bone markings

Sella turcica/hypophyseal fossa (holds pituitary gland); greater wings (lateral skull/orbit); lesser wings; optic canal (CN II + ophthalmic artery); superior orbital fissure (CN III, IV, V1, VI); foramen ovale (CN V3); foramen rotundum (CN V2); pterygoid processes

Ethmoid bone markings

Crista galli (anchors dura mater); cribriform plate + olfactory foramina (CN I); perpendicular plate (upper nasal septum); superior and middle nasal conchae (warm/humidify air)

Nasal septum formed by

Perpendicular plate of ethmoid (superior) + vomer (inferior/posterior)

Mandible markings

Condyle (forms TMJ with temporal bone); mental foramen (CN V3 + mental vessels); mandibular symphysis (midline chin); alveolar margin (tooth sockets)

Maxilla markings

Infraorbital foramen (CN V2 branch); alveolar margin; maxillary sinus; forms anterior hard palate; facial keystone bone

Only movable skull bone

Mandible

Two unpaired facial bones

Mandible and vomer

Paranasal sinuses (4 bones)

Maxillary, sphenoid, ethmoid, frontal; lighten bones + resonate voice; sinusitis = inflamed mucosa → pain/pressure

Hyoid bone

U-shaped; does not articulate with any other bone; base of tongue; moves during swallowing/speech

Fontanelles

Membranous "soft spots" in newborn skull; allow compression during birth; begin closing ~2 months, fully closed by ~2 years

Vertebral column regions and counts

Cervical C1–C7 (7); Thoracic T1–T12 (12); Lumbar L1–L5 (5); Sacrum (1, 5 fused); Coccyx (1, 4–5 fused)

4 spinal curvatures

Cervical (secondary/posterior concave); Thoracic (primary/anterior concave); Lumbar (secondary/posterior concave); Sacrococcygeal (primary/anterior concave)

Primary vs. secondary spinal curves

Primary (thoracic, sacral): develop before birth; Secondary (cervical, lumbar): develop after birth with holding head up and standing

Scoliosis / Kyphosis / Lordosis

Scoliosis: lateral S/C curve; Kyphosis: excessive upper thoracic rounding; Lordosis: excessive anterior lumbar curve

Common vertebral bone markings

Body (centrum): anterior, weight-bearing; Vertebral arch (pedicles + laminae); Vertebral foramen: spinal cord passage; Spinous process: posterior midline; Transverse processes: lateral; Superior/inferior articular processes: join adjacent vertebrae; Intervertebral discs: fibrocartilage cushion between bodies

Intervertebral disc structure

Fibrous outer annulus fibrosus surrounding gel-like nucleus pulposus

Cervical vertebrae (C3–C7) features

Small body; large triangular vertebral foramen; bifid (split) spinous process; transverse foramina (vertebral arteries/veins); great range of motion

Atlas (C1) unique features

No body; lateral masses articulate with occipital condyles → allows head flexion/extension

Axis (C2) unique features

Has dens (odontoid process) that acts as pivot for atlas → allows head rotation

Thoracic vertebrae features

Heart-shaped body with costal facets (demifacets) for rib articulation; long thin spinous process pointing inferiorly; circular vertebral foramen; transverse processes with costal facets (except T11–T12)

Lumbar vertebrae features

Largest kidney-shaped body; short blunt spinous process pointing posteriorly; smallest triangular foramen; thin tapered transverse processes with no costal facets; flexion/extension but no rotation

Sacrum landmarks

5 fused vertebrae; base (widest, articulates with L5); medial sacral crest (from spinous processes); lateral sacral crest (from transverse processes); sacral foramina (sacral nerves); alae; auricular surface (articulates with ilium at sacroiliac joint); sacral promontory

Coccyx

4–5 fused vertebrae; fuse ~age 25; attachment for ligaments/tendons

Thoracic cage components

Thoracic vertebrae (posterior), ribs (lateral), costal cartilages + sternum (anterior); protects heart/lungs/thymus

True vs. false vs. floating ribs

True (1–7): direct costal cartilage to sternum; False (8–12): no direct sternal connection; Floating (11–12): no sternal or cartilage attachment at all; Vertebrochondral (8–10): attach via cartilage of rib above

Sternum 3 parts

Manubrium (articulates with clavicles + rib 1); Body (ribs 2–7); Xiphoid process (attaches diaphragm + rectus abdominis)

Rib bone markings

Head/capitulum (articulates with vertebral body demifacets); neck; tubercle (articulates with transverse costal facet); angle; body/shaft; costal groove (protects intercostal nerves/vessels)

Demifacet

Half-facet on thoracic vertebral body; two adjacent demifacets unite to form the full articular surface for a rib head

Appendicular skeleton total

126 bones; pectoral girdle (4) + upper limbs (60) + pelvic girdle (2) + lower limbs (60)

Pectoral girdle bones and function

2 clavicles + 2 scapulae; connects arms to body; specialized for mobility; only axial connection = clavicle to manubrium

Clavicle

S-shaped collarbone; sternal end → manubrium; acromial end → scapula acromion

Scapula borders and angles

3 borders: superior, medial (vertebral), lateral (axillary); 3 angles: superior, inferior, lateral

Scapula bone markings

Glenoid cavity (shoulder socket, forms glenohumeral joint); coracoid process (anterior muscle attachment); acromion process (connects to clavicle = acromioclavicular joint); scapular spine (posterior ridge); supraspinous fossa; infraspinous fossa; subscapular fossa (anterior)

Glenohumeral joint

Ball-and-socket; head of humerus in glenoid cavity; most mobile joint; prone to dislocation (minimal bony stability, held mainly by rotator cuff + ligaments)

Humerus proximal markings

Head (fits glenoid cavity); anatomical neck (joint capsule boundary); surgical neck (common fracture site); greater tubercle (lateral contour, muscle attachment); lesser tubercle (anterior-medial, muscle attachment); intertubercular sulcus (bicipital groove, houses biceps tendon); deltoid tuberosity (deltoid attachment)

Humerus distal markings

Capitulum (articulates with radial head); trochlea (articulates with ulnar trochlear notch); medial epicondyle (flexor muscles); lateral epicondyle (extensor muscles); olecranon fossa (receives ulnar olecranon in extension); coronoid fossa (receives coronoid process in flexion); radial fossa

Ulna proximal markings

Olecranon process (tip of elbow, fits olecranon fossa); trochlear notch (articulates with trochlea); coronoid process; radial notch (proximal radioulnar joint)

Ulna distal markings

Head of ulna (distal radioulnar joint with radius); ulnar styloid process (muscle/ligament attachment)

Radius proximal markings

Head (articulates with capitulum + radial notch of ulna); neck; radial tuberosity (biceps brachii attachment)

Radius distal markings

Ulnar notch (distal radioulnar joint); radial styloid process (wrist stabilization)

Pronation

Radius crosses over ulna; palm faces posteriorly/medially

8 carpal bones — proximal row (lateral → medial)

Scaphoid, lunate, triquetrum, pisiform

8 carpal bones — distal row (lateral → medial)

Trapezium, trapezoid, capitate, hamate

Metacarpals

5 bones; numbered 1 (thumb/pollex) to 5 (pinky); each has base (proximal), shaft, and head (knuckle = MCP joint)

Phalanges of hand

Thumb (pollex): 2 (proximal + distal only); Digits 2–5: 3 each (proximal, middle, distal)

Pelvic girdle vs. pectoral girdle

Pelvic: 2 coxal bones; limited mobility, high strength/stability; Pectoral: 2 clavicles + 2 scapulae; high mobility, less stability

Coxal bone (os coxae) 3 fused bones

Ilium (superior/largest); Ischium (posterior/inferior); Pubis (anterior); all three meet at the acetabulum

Acetabulum

Hip socket on lateral coxal bone; articulates with femoral head (hip joint)

Ilium markings

Iliac crest (palpable top of hip); ASIS; AIIS; PSIS; PIIS; greater sciatic notch (sciatic nerve); iliac fossa; auricular surface (sacroiliac joint)

Ischium markings

Ischial tuberosity ("sit bones"); ischial spine (creates lesser sciatic notch); ischial ramus (fuses with inferior pubic ramus)

Pubis markings

Superior pubic ramus; inferior pubic ramus; pubic tubercle; pubic symphysis (fibrocartilage, amphiarthrodial joint)

Obturator foramen

Large opening surrounded by ischium and pubic rami; passage for blood vessels and nerves to lower extremity

Male vs. female pelvis — 3 key differences

Female: broader/lighter/less prominent markings; wider pubic arch (>100°) vs. male (<90°); female pelvic inlet = oval/circular; male = heart-shaped/narrow; female pelvic outlet = wide; male = narrow

Femur proximal markings

Head (acetabulum); fovea capitis (ligament attachment); neck; greater trochanter (superior, muscle attachment); lesser trochanter (inferior, muscle attachment); intertrochanteric line (anterior); intertrochanteric crest (posterior)

Femur distal markings

Medial and lateral condyles (knee joint); medial and lateral epicondyles (muscle attachment); adductor tubercle (adductor magnus); intercondylar fossa (posterior); patellar surface (anterior)

Patella

Sesamoid bone; forms within quadriceps femoris tendon; triangular; protects knee anteriorly

Tibia markings

Medial and lateral condyles (articulate with femur); intercondylar eminence; tibial tuberosity (patellar ligament); medial malleolus (medial ankle); weight-bearing medial leg bone

Fibula markings

Head (proximal tibiofibular joint); lateral malleolus (lateral ankle); does NOT bear weight; does NOT articulate with femur

Medial malleolus vs. lateral malleolus

Medial malleolus = distal tibia (inner ankle); Lateral malleolus = distal fibula (outer ankle)

7 tarsal bones

Talus (superior, forms ankle with tibia/fibula); Calcaneus (heel, largest tarsal, Achilles tendon); Navicular; Cuboid; Medial, Intermediate, and Lateral cuneiforms

Foot arches

Longitudinal arch (heel to toes) and transverse arch (across foot); provide stable, springy base; flat feet = weakened supporting tissues

Metatarsals and foot phalanges

5 metatarsals (1 = hallux/great toe); Hallux: 2 phalanges (proximal + distal); Toes 2–5: 3 each (proximal, middle, distal)