Skeletal System

[Terminology] What is the anatomical position?

Standing upright, head/eyes forward, arms at sides, palms anterior, feet forward.

[Terminology] Define anterior vs posterior.

Anterior = toward the front; posterior = toward the back.

[Terminology] Define superior vs inferior.

Superior = toward the head/above; inferior = toward the feet/below.

[Terminology] Define medial vs lateral.

Medial = toward the midline; lateral = away from the midline.

[Terminology] Define proximal vs distal.

Proximal = closer to trunk/origin; distal = farther from trunk/origin.

[Terminology] Define superficial vs deep.

Superficial = closer to surface; deep = farther from surface.

[Terminology] What do sagittal, coronal and transverse planes divide?

Sagittal: right/left; coronal: anterior/posterior; transverse: superior/inferior.

[Movement] Define flexion and extension.

Flexion decreases a joint angle; extension increases it.

[Movement] Define abduction and adduction.

Abduction moves away from the midline; adduction moves toward it.

[Movement] Define pronation and supination of the forearm.

Pronation: radius crosses ulna, palm posterior/down; supination: radius/ulna parallel, palm anterior/up.

[Movement] Define dorsiflexion and plantarflexion.

Dorsiflexion brings dorsum of foot toward leg; plantarflexion points foot/toes downward.

[Movement] Define inversion and eversion.

Inversion turns sole medially; eversion turns sole laterally.

[Bone Basics] What are the two major divisions of the skeleton?

Axial and appendicular.

[Bone Basics] What makes up the axial skeleton?

Skull, hyoid, vertebral column and thoracic cage.

[Bone Basics] What makes up the appendicular skeleton?

Pectoral girdles + upper limbs and pelvic girdle + lower limbs.

[Bone Basics] How many adult axial and appendicular bones are there?

Axial = 80; appendicular = 126.

[Bone Basics] What are the major functions of the skeletal system?

Support, protection, movement, mineral/lipid storage and haematopoiesis.

[Bone Basics] Bone vs bone tissue: what is the difference?

A bone is an organ containing multiple tissues; bone tissue is supportive connective tissue.

[Bone Matrix] What do hydroxyapatite and collagen contribute to bone?

Hydroxyapatite: hardness/compressive strength; collagen: flexibility/tensile strength.

[Bone Cells] What do osteoblasts, osteocytes and osteoclasts do?

Osteoblasts form matrix; osteocytes maintain it; osteoclasts resorb it.

[Bone Cells] Where are osteocytes and how do they communicate?

In lacunae; they communicate through canaliculi.

[Bone Classification] Name the main bone-shape classifications with examples.

Long: femur/humerus; short: most carpals/tarsals; flat: sternum/ribs/scapula; irregular: vertebra/os coxae; sesamoid: patella; pneumatic: air-filled skull bones.

[Bone Classification] What is a sesamoid bone? Give two important examples.

A bone developing within a tendon; patella and pisiform.

[Bony Features] What are condyle, facet, head and trochlea?

Condyle = rounded articular prominence; facet = small flat articular surface; head = rounded articular end; trochlea = pulley-shaped articular surface.

[Bony Features] What are fossa and sulcus?

Fossa = depression/pit; sulcus = groove.

[Bony Features] What are tubercle and tuberosity?

Tubercle = smaller projection; tuberosity = larger roughened projection, often for attachment.

[Bony Features] What are foramen, fissure and sinus?

Foramen = hole/opening; fissure = narrow slit; sinus = air-filled cavity.

[Long Bone] Define diaphysis, metaphysis and epiphysis.

Diaphysis = shaft; metaphysis = transition/growth-plate region; epiphysis = end.

[Long Bone] What covers articular surfaces of bones in life?

Articular hyaline cartilage.

[Long Bone] What is an epiphyseal line?

The bony remnant of a former growth plate.

[Bone Structure] Compact vs trabecular bone?

Compact/cortical = dense outer bone; trabecular/spongy/cancellous = internal lattice-like bone.

[Bone Structure] Red vs yellow marrow?

Red marrow forms blood cells; yellow marrow stores fat.

[Bone Structure] What are periosteum and endosteum?

Periosteum covers external bone surfaces; endosteum lines internal bone surfaces/cavities.

[Ossification] Intramembranous vs endochondral ossification?

Intramembranous: bone forms directly in connective tissue; endochondral: bone replaces a cartilage model.

[Ossification] Which bones are especially associated with intramembranous ossification?

Flat skull bones and parts of the mandible and clavicle.

[Ossification] Which ossification process forms typical long bones and most of the skeleton?

Endochondral ossification.

[Ossification] What is osteoid?

Newly formed unmineralised organic bone matrix produced by osteoblasts.

[Ossification] How does a long bone grow in length vs width?

Length: growth plate/endochondral ossification; width: appositional growth.

[Joint Classification] What are the four structural classes of joints?

Bony, fibrous, cartilaginous and synovial.

[Joint Classification] What are synarthrosis, amphiarthrosis and diarthrosis?

Synarthrosis = essentially immobile; amphiarthrosis = slightly movable; diarthrosis = freely movable.

[Joint Classification] What is a synostosis?

A bony union formed when a previous fibrous/cartilaginous joint ossifies.

[Joint Classification] What are synchondrosis and symphysis?

Synchondrosis = hyaline-cartilage joint; symphysis = fibrocartilage joint.

[Joint Classification] What are suture, gomphosis and syndesmosis?

Suture = fibrous skull joint; gomphosis = tooth-in-socket; syndesmosis = bones connected by ligament/interosseous membrane.

[Synovial Joint] What are the essential components of a typical synovial joint?

Joint capsule, synovial membrane, joint cavity/fluid, articular cartilage and ligaments.

[Synovial Joint] What is a labrum and what does it do?

A fibrocartilaginous/cartilaginous rim that deepens a socket and improves congruency/stability.

[Synovial Joint] What is a meniscus and what does it do?

Fibrocartilage that improves congruency/contact and distributes load.

[Synovial Joint] What general trade-off exists between joint mobility and stability?

Greater mobility generally comes at the cost of stability.

[Synovial Types] Name the six synovial joint types.

Plane, hinge, pivot, condyloid/ellipsoid, saddle and ball-and-socket.

[Synovial Types] Which synovial joint types are non-axial, uniaxial, biaxial and triaxial?

Plane = non-axial; hinge/pivot = uniaxial; condyloid/saddle = biaxial; ball-and-socket = triaxial.

[Synovial Types] Give key examples of plane joints.

Acromioclavicular, intercarpal, intertarsal and zygapophyseal joints.

[Synovial Types] Give key examples of hinge joints.

Humeroulnar, interphalangeal and talocrural joints.

[Synovial Types] Give key examples of pivot joints.

Proximal/distal radioulnar and median atlantoaxial joints.

[Synovial Types] Give key examples of condyloid/ellipsoid joints.

Radiocarpal and metacarpophalangeal joints.

[Synovial Types] Give key examples of saddle and ball-and-socket joints.

Saddle: 1st CMC (SC joint is modified saddle); ball-and-socket: glenohumeral and hip.

[Skull] How many bones form the skull proper, and how are they divided?

22: 8 cranial + 14 facial.

[Skull] Name the 8 cranial bones.

Frontal; 2 parietal; occipital; 2 temporal; sphenoid; ethmoid.

[Skull] Name the 14 facial bones.

2 maxillae, 2 palatine, 2 zygomatic, 2 lacrimal, 2 nasal, 2 inferior nasal conchae, vomer and mandible.

[Skull] Name the auditory ossicles and the additional hyoid bone.

Malleus, incus and stapes; hyoid.

[Skull] Name the four major skull sutures.

Coronal, sagittal, lambdoid and squamous.

[Skull] Which bones meet at the coronal, sagittal and lambdoid sutures?

Coronal: frontal-parietal; sagittal: parietal-parietal; lambdoid: parietal-occipital.

[Skull] Which bones meet at the squamous suture?

Parietal and temporal.

[Skull] Name the three cranial fossae.

Anterior, middle and posterior.

[Skull] What passes through the foramen magnum?

Medulla/spinal cord transition, meninges and vertebral arteries.

[Skull] What passes through the carotid canal?

Internal carotid artery.

[Skull Features] Match these features to bones: superciliary ridges, external occipital protuberance, external auditory meatus.

Superciliary ridges = frontal; external occipital protuberance = occipital; external auditory meatus = temporal.

[Skull Features] Match these features to bones: greater wing, sella turcica, pterygoid plates.

All are features of the sphenoid.

[Skull Features] Match these features to bones: crista galli, cribriform plate, superior/middle nasal conchae.

All are features of the ethmoid.

[Skull Features] What forms the bony nasal septum?

Perpendicular plate of ethmoid + vomer.

[Skull Features] What forms the hard palate?

Palatine processes of maxillae anteriorly + horizontal plates of palatine bones posteriorly.

[Mandible] What are the main mandibular regions/features to recognize?

Body, ramus, angle, coronoid process, condylar process, mandibular notch, mental and mandibular foramina.

[TMJ] How is the temporomandibular joint described in this course?

A modified hinge synovial joint.

[Hyoid] What should you know about the hyoid?

Anterior neck bone that does not directly articulate with another bone; supports tongue and provides muscle attachment for swallowing/speech.

[Neonatal Skull] What are fontanelles and why are they important?

Connective-tissue gaps between infant skull bones; permit moulding during birth and allow brain/skull growth.

[Vertebral Column] How many cervical, thoracic and lumbar vertebrae are there?

7 cervical, 12 thoracic, 5 lumbar.

[Vertebral Column] How many segments form the sacrum and coccyx in the course material?

Sacrum = 5 fused; coccyx ≈ 4 fused.

[Vertebra] What are the major parts of a typical vertebra?

Body, vertebral arch (pedicles + laminae), vertebral foramen, spinous/transverse processes and superior/inferior articular processes/facets.

[Vertebra] Main function of the vertebral body and vertebral foramen?

Body = weight-bearing; foramen = passage forming the vertebral canal for spinal cord.

[Vertebra] What is a zygapophyseal/facet joint?

Synovial plane joint between articular processes of adjacent vertebrae.

[Cervical Vertebrae] How do you recognize a typical cervical vertebra?

Transverse foramina, bifid spinous process, small oval body and large triangular vertebral foramen; uncovertebral lips.

[Cervical Vertebrae] Are cervical vertebral foramina relatively large or small?

Relatively large.

[Atlas C1] How do you recognize the atlas (C1)?

No body or true spinous process; anterior/posterior arches and lateral masses.

[Atlas C1] What articulates with the superior facets of C1?

Occipital condyles.

[Axis C2] How do you recognize the axis (C2)?

Presence of the dens/odontoid process.

[Thoracic Vertebrae] How do you recognize a typical thoracic vertebra?

Costal facets for ribs, long inferiorly directed spinous process and relatively small circular vertebral foramen.

[Thoracic Vertebrae] What articulates with thoracic body costal facets vs transverse costal facets?

Rib head with body facets; rib tubercle with transverse-process facet.

[Lumbar Vertebrae] How do you recognize a lumbar vertebra?

Very large body with short, robust/stumpy spinous process; no transverse foramina or rib facets.

[Sacrum] What sacral features are high yield for spotters?

Base, apex, sacral canal/hiatus, anterior/posterior foramina, median sacral crest, auricular surface and sacral tuberosity.

[Sacrum] What does the sacral auricular surface articulate with?

Ilium at the sacroiliac joint.

[Ribs] Name the main features of a typical rib.

Head, neck, tubercle, body/shaft, angle and costal groove.

[Ribs] Which rib feature articulates with vertebral bodies and which with a transverse process?

Head → vertebral bodies; tubercle → transverse process.

[Ribs] Which ribs are true, false and floating?

True 1–7; false 8–12; floating 11–12.

[Sternum] Name the three parts of the sternum.

Manubrium, body and xiphoid process.

[Sternum] Which sternum landmarks should you recognize?

Jugular/suprasternal notch, clavicular notches, sternal angle and costal notches.

[Thoracic Joints] What is the key sternocostal-joint exception?

The 1st sternocostal joint is a cartilaginous synchondrosis; the others are generally synovial.

[Upper Limb] What bones form the pectoral girdle?

Clavicle and scapula.

[Clavicle] What should you recognize on the clavicle?

Sternal/medial end, acromial/lateral end, conoid tubercle and costal tuberosity.

[Clavicle] What is unusual about clavicular ossification?

Central portion intramembranous; ends endochondral.

[SC Joint] What articulates at the sternoclavicular joint and how is it classified?

Clavicle with manubrium/1st costal cartilage; synovial modified saddle, biaxial diarthrosis.

[AC Joint] How is the acromioclavicular joint classified?

Synovial plane; non-axial diarthrosis.

[Scapula] Name the 3 borders and 3 angles of the scapula.

Borders: superior, medial, lateral. Angles: superior, inferior, lateral.