Human Osteology notes

Directional Terms

• Superior (cranial) – top

• Inferior (caudal) – bottom

• Anterior (ventral) – front

• Posterior (dorsal) – back

• Medial – toward midline

• Lateral – away from midline

• Proximal – nearest to torso

• Distal – furthest from the torso

• Bone as living tissue: bone responds to stress, muscle action, disease, trauma, and nutritional status

• When examining a bone, look for articulation facets (smooth surfaces where two bones meet) and for muscle/ligament attachments which are raised, roughened areas

• Attachment size reflects muscle size: larger muscles need larger attachment areas

• Terminology for surface features:

  • Line: small, slightly raised marking

  • Ridge: more protruding mark

  • Crest: prominent, protruding attachment area

• Foramina (singular: foramen): holes in the bone

• Skeleton division: cranial vs postcranial material

Cranial Components

• Skull consists of cranium and mandible

• Cranium includes face and calvarium; calvarium = brain case

• The skull is composed of a number of distinct bones; note major cranial bones and their articulations in your lab

• Sutures: lines where cranial bones meet; major sutures include Coronal, Lambdoidal, Squamosal, and Sagittal

• Sutures knit together (close) as maturity increases; degree of closure can indicate age (loose sutures in infants allow birth canal passage)

• Mandible: lower jaw; formed by left and right dentary bones fused at the midline in humans (in many mammals they do not fuse, forming a flexible joint)

• Teeth: incisors, canines, premolars, and molars visible in both maxilla (upper jaw) and mandible

• Dental pattern shorthand (dental formula) describes tooth types per quadrant

  • Example: human dental pattern in one quadrant is $2:1:2:3$

  • This means: 2 incisors, 1 canine, 2 premolars, 3 molars in each quadrant

  • Total tooth count = 32

• Palate, incisors, canine, maxilla, zygomatic, etc. are illustrated in figures; major bones and sutures shown in Figures 2–5 in the source

• Hyoid bone: a small U-shaped bone in the throat that floats (no articulation with other bones); origin for tongue and floor-of-mouth muscles; can move side to side when palpated in the throat

  

Postcranial Elements

• Postcranial skeleton = axial skeleton + appendicular skeleton

• Axial skeleton includes vertebral column + ribs + sternum; articulates with ribs via costal cartilage

• Appendicular skeleton includes pectoral girdle, upper limbs, pelvic girdle, lower limbs

Axial Skeleton - Vertebral Column, Ribs and Sternum

• Vertebral column features are shown in Figures 6–10; identify distinctive features of each vertebra

• Cervical vertebrae (7): unique for having transverse foramina (foramen transversarium)

• Atlas (C1) and Axis (C2) are the first two cervical vertebrae; Dens is a key feature on Axis

• Thoracic vertebrae (12): have rib articulation facets (costal facets) for articulation with ribs

• Lumbar vertebrae (5): distinctive S-curve; large size; short, squared spinous processes; lack of foramina or rib facets

• Sacrum: typically 5 fused sacral vertebrae; articulates with the pelvis

• Coccyx: 4–5 very small coccygeal vertebrae; represents the end of the backbone in humans; in other primates these elements would be larger and tail (caudal) vertebrae

• Anterior view vs dorsal view show key features: vertebral foramen, spinous process, transverse process, rib articulation facets

• Ribs

  • Humans have 12 ribs on each side

  • Ribs meet thoracic vertebrae dorsally and costal cartilage ventrally

  • Cartilaginous connections provide flexibility for breathing

  • Ribs 1–10 join the sternum via costal cartilage; Ribs 11–12 are floating ribs (do not join sternum)

  • First rib is relatively small and flat (superior–inferior dimension small)

  • Ribs 2–10 are flat front-to-back; superior surface rounded; inferior surface sharp

• Sternum

  • Flat bone known as the breastbone

  • Three segments: manubrium (superior), body (middle), xiphoid process (inferior)

  • In adults these segments are usually fused, though sometimes unfused

Pectoral Girdle and Upper Limb

• Scapula (shoulder blade): triangular, located dorsally on the thorax

  • Muscles envelop the blade except for the spine running along the dorsal aspect

  • Spine ends at the acromion process

  • Coracoid process projects anteriorly; glenoid fossa is the lateral surface that articulates with the humerus

  • Humeral head fits into the glenoid fossa to form the shoulder joint

  • Range of motion: humeral head rotates in the glenoid; full arm elevation is limited by shoulder joint; to raise arm above head, scapula rotates—example: touch top of head with right arm involves maximal humeral rotation plus counterclockwise scapular rotation to position the glenoid fossa upward

• Clavicle (collarbone): S-shaped, lies between the scapula and sternum

  • Very strong ligaments hold it in place; rarely dislocates

  • More likely to fracture under extreme stress than to dislocate

  • Functions as a lateral brace for the shoulder

• Upper limb bones (overview): humerus, radius, ulna, carpals, metacarpals, and phalanges

• Humerus

  • Largest bone in the arm

  • Proximal head articulates with the glenoid fossa; distal end articulates with radius and ulna (forms part of the elbow and shoulder joints collectively with the scapula)

  • Deltoid tuberosity on the lateral midshaft where the deltoid muscle inserts

  • Distal end features: medial epicondyle, trochlea (articulates with ulna), capitulum (articulates with head of radius), and olecranon fossa (posterior; accommodates the olecranon of the ulna when the arm is extended)

  • The ulnar nerve runs medially near the medial epicondyle (funny bone sensation when struck)

• Radius

  • Lateral bone of the forearm (thumb side) in anatomical position; the palm faces forward

  • Proximally articulates with the capitulum of the humerus and the radial notch of the ulna

  • Distally articulates with the carpal bones and the head of the ulna

  • Pronation: turning the hand over; radius crosses over the ulna so the dorsal surface of the hand faces forward

  • Supination: returning the palm to anatomical position; radius and ulna uncross

• Ulna

  • Medial bone of the forearm; has a hook-like proximal end called the olecranon process (articulates with the humerus’ trochlea)

  • Lateral with the radial head via the radial notch

  • Distal end has the ulnar head; articulates with the radius at the ulnar notch

  • Function: flexion and extension of the forearm

  • Distal end features include a prominent styloid process

• Carpals and the Hand

  • Carpals: eight wrist bones; each with a unique shape and name (not required to learn all names in this lab)

  • Metacarpals: five long bones in the palm; numbered 1–5 from the thumb (pollex to pinky)

  • Phalanges: finger bones

  • Pollex (thumb) has two phalanges (proximal and distal)

  • Digits 2–5 each have three phalanges (proximal, middle, distal)

Pelvis

• Pelvic girdle consists of left and right innominate bones (coxal bones) that articulate with the sacrum

• Each innominate appears as a single bone in the adult but is formed from three bones in juveniles: ilium (top blade), pubis (anterior), ischium (posterior-inferior)

• In adults, these three bones fuse into a single innominate bone on each side

• The pelvis is critical for anthropological work: key for age and sex estimation and for identifying locomotion (bipedalism) patterns in humans

• Figure reference: pelvis with innominate, pubis, etc.

Lower Limb

• Femur (thighbone): largest bone in the body

  • Femoral head articulates with the acetabulum (hip socket) forming a ball-and-socket joint; highly stable but relatively less flexible than the shoulder

  • Posterior shaft commonly shows a raised line called the linea aspera, origin site for hamstring muscles

  • Distal femur articulates with the tibia via the condyles; distal anterior surface articulates with the patella via the patellofemoral joint

  • Quadriceps muscle group forms the anterior thigh; tendon crosses the knee and inserts on the tibia; the patella enhances the leverage of the quadriceps

• Patella

  • Kneecap, embedded within the quadriceps tendon; increases pull efficiency of the quadriceps across the knee

• Tibia (shinbone)

  • Large, medial bone of the lower leg; articulates with the femur at the tibial plateau

  • Tibial tuberosity: insertion site for the quadriceps tendon; located below the plateau

  • Medial malleolus: prominent projection on the medial distal tibia; forms part of the ankle joint

  • Anterior crest: a ridge along the anterior surface of the shaft

  • Distal articulation with the fibula and with the tarsal bones (
    ankle region)

• Fibula

  • Slender bone on the lateral side of the lower leg

  • Articulates with the tibia proximally and with the tarsals distally

  • Lateral malleolus: distal end projection (outer ankle bump); not weight-bearing but stabilizes the ankle

• Tarsals and Foot

  • Tarsals: seven ankle bones, including the calcaneus (heel bone)

  • Metatarsals: five long bones in the foot; numbered 1–5 from the big toe

  • Phalanges: toe bones; like the hand, the big toe (hallux) has two phalanges; digits 2–5 have three phalanges

• Figure reference: Left foot diagram illustrating phalanges, metatarsals, and tarsals

Summary of Key Concepts and Implications

• The skeleton is organized into cranial and postcranial components, with the skull housing the brain and sense organs, and the postcranial skeleton supporting movement and protection

• Sutures in the skull serve both a functional and developmental role: flexibility for birth and age estimation through suture closure

• The dental formula provides a compact summary of dentition and total tooth count; humans typically have 32 teeth with a per-quadrant pattern of $2:1:2:3$

• The vertebral column shows regional specialization: cervical with transverse foramina (specialization for vertebral arteries in the neck), thoracic with rib facets, lumbar with large bodies and short processes; sacrum and coccyx anchor the spine to the pelvis and tail region, respectively

• The rib cage articulates with the spine via costal facets and with the sternum via costal cartilage, providing protection for thoracic organs and contributing to respiration dynamics

• The pelvis is central for age and sex estimation and is essential to understanding habitual locomotion in humans

• The shoulder complex demonstrates integrated mobility: the glenoid joint with the humerus is stabilized by the scapula’s rotation and the clavicle’s anchoring role

• Pronation and supination describe forearm rotation driven by radius and ulna arrangement; the radius crossing over the ulna enables pronation, and uncrossing enables supination

• The musculoskeletal system shows consistent relationships between bone morphology and function (e.g., deltoid tuberosity as a site of shoulder muscle attachment; linea aspera as a hamstring origin)

• Practical lab insights include palpation landmarks (medial epicondyle, olecranon fossa, medial malleolus, etc.) and movements that reveal joint mechanics

• The dental and skeletal references connected to real-world applications: anatomy of movement, age/sex estimation, and anthropological interpretation of locomotion and evolution

  

Directional Terms

• Superior (cranial) – top

• Inferior (caudal) – bottom

• Anterior (ventral) – front

• Posterior (dorsal) – back

• Medial – toward midline

• Lateral – away from midline

• Proximal – nearest to torso

• Distal – furthest from the torso

• Bone responds to stress, muscle action, disease, trauma, and nutrition. Look for articulation facets (smooth surfaces) and raised muscle/ligament attachments (size reflects muscle size).

• Terminology for surface features:

  • Line: small, slightly raised mark

  • Ridge: more protruding mark

  • Crest: prominent, protruding attachment area

  • Foramina (singular: foramen): holes in the bone

• Skeleton division: cranial vs postcranial material

Cranial Components

• Skull = cranium (face + brain case/calvarium) + mandible.

• Cranial bones meet at sutures (Coronal, Lambdoidal, Squamosal, Sagittal), which close with age.

• Mandible: lower jaw, fused dentary bones in humans.

• Teeth: incisors, canines, premolars, molars in maxilla (upper jaw) and mandible.

• Dental pattern shorthand: human formula is $2:1:2:3$ per quadrant (2 incisors, 1 canine, 2 premolars, 3 molars), totaling 32 teeth.

• Hyoid bone: U-shaped, floats in throat, origin for tongue muscles.

Postcranial Elements

• Postcranial skeleton = axial skeleton (vertebral column + ribs + sternum) + appendicular skeleton (pectoral/pelvic girdles + limbs).

Axial Skeleton - Vertebral Column, Ribs and Sternum

• Vertebral column:

  • Cervical (7): unique with transverse foramina. Atlas (C1) and Axis (C2, with Dens).

  • Thoracic (12): have rib articulation facets.

  • Lumbar (5): large, short/squared spinous processes, no foramina/rib facets.

  • Sacrum (5 fused): articulates with pelvis.

  • Coccyx (4–5 small): end of backbone.

• Ribs:

  • 12 pairs. Meet thoracic vertebrae (dorsally) and costal cartilage/sternum (ventrally).

  • Ribs 1–10 join sternum; Ribs 11–12 are floating.

• Sternum (breastbone): manubrium, body, xiphoid process; usually fused in adults.

Pectoral Girdle and Upper Limb

• Scapula (shoulder blade): triangular; spine ends at acromion; coracoid process projects anteriorly; glenoid fossa articulates with humerus.

• Clavicle (collarbone): S-shaped; strong brace for shoulder, often fractures under stress.

• Upper limb bones: humerus, radius, ulna, carpals, metacarpals, phalanges.

  • Humerus: largest arm bone; head articulates with glenoid fossa; distal end articulates with radius/ulna (elbow joint).

  • Radius: lateral forearm bone (thumb side); crosses over ulna during pronation, uncrosses during supination.

  • Ulna: medial forearm bone; olecranon process forms part of elbow; ulnar nerve near medial epicondyle ("funny bone").

  • Carpals: 8 wrist bones.

  • Metacarpals: 5 palm bones (1-5 from thumb).

  • Phalanges: finger bones; thumb (pollex) has 2, digits 2-5 have 3.

Pelvis

• Pelvic girdle: left and right innominate bones, articulate with sacrum.

• Each innominate (adult) is fused from ilium, pubis, ischium (juvenile).

• Critical for age/sex estimation and locomotion (bipedalism) patterns.

Lower Limb

• Femur (thighbone): largest bone; head articulates with acetabulum (hip socket, stable but less flexible than shoulder); linea aspera on posterior shaft; distal end articulates with tibia (condyles) and patella.

• Patella (kneecap): embedded in quadriceps tendon, enhances leverage.

• Tibia (shinbone): large, medial lower leg bone; articulates with femur (tibial plateau); quadriceps tendon inserts at tibial tuberosity; medial malleolus (inner ankle).

• Fibula: slender, lateral lower leg bone; stabilizes ankle via lateral malleolus (outer ankle).

• Tarsals: 7 ankle bones (e.g., calcaneus/heel bone).

• Metatarsals: 5 foot bones (1-5 from big toe).

• Phalanges: toe bones; big toe (hallux) has 2, digits 2-5 have 3.

Summary of Key Concepts and Implications

• Skeleton organized into cranial and postcranial components.

• Sutures aid birth and age estimation.

• Dental formula (e.g., human $2:1:2:3$) summarizes dentition.

• Vertebral column shows regional specialization (cervical foramina, thoracic facets, lumbar size).

• Rib cage protects organs and aids respiration.

• Pelvis is key for age/sex estimation and understanding locomotion.

• Shoulder complex (scapula, clavicle, humerus) enables wide mobility.

• Forearm pronation/supination involves radius crossing over ulna.

• Bone morphology reflects function (e.g., deltoid tuberosity for muscle attachment).