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State Board · Class 11 · Biology

Lesson 16: Skeleton and Movements

7 concepts · 56 practice questions with answers · Free to read

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Movements, locomotion and muscle pairs

Link to Std 9–10

Std 8–10 introduced bones and muscles; here we study the sarcomere, sliding filament theory, the skeleton and joints in detail.

From daily life

Opening a door bends and straightens your arm: one muscle pulls, its partner pulls the other way.

Simple definition

Locomotion = movement of the whole body from one place to another. All locomotion is movement, but not every movement is locomotion. Muscles work in antagonistic pairs.

Movement and muscle pairsMovement, locomotion and muscle pairsAmoeboidpseudopodia; leucocytesCiliarycilia; ParameciumFlagellarflagella; spermMuscularmuscle + bone + jointMuscle pairs (arm)Biceps = flexor (agonist)Triceps = extensor (antagonist)Brachialis = synergistA muscle only pulls, never pushesOrigin = fixed bone; insertion = moving boneBelly = thick middle; tendon links to boneAll locomotion is movement, not vice versa~640 muscles in the body (634 paired)Flexor / Extensorbends / straightensAbductor / Adductoraway / towards axisPronator / Supinatorpalm down / upLevator / Depressorraises / lowersProtractor / Retractorforward / backwardSphinctercircular; closes / opens

In the figure : Types of locomotion and muscle pairs.

Rule 1 : Movement and locomotion — Movements may be internal (peristalsis, heartbeat) or external; voluntary or involuntary. Smooth muscle: involuntary (gut, vessels); cardiac muscle: heart; striated muscle: voluntary (limbs, eyes). Four types of locomotion: amoeboid (pseudopodia; white cells), ciliary (cilia; airway, Paramecium), flagellar (sperm), muscular (muscle + bone + joint). Muscles attach to bone by tendons (inelastic collagen bands).

  • Easy : Locomotion ⊂ movement.
  • Medium : Tendon = muscle–bone; ligament = bone–bone.
  • Exam-type (CET) : ~640 muscles in the body.

Rule 2 : Agonists, antagonists and pairs — A muscle can only pull a bone. The agonist (prime mover) starts the movement (biceps); the antagonist opposes it (triceps); the synergist assists (brachialis). End on the fixed bone = origin, end on the moving bone = insertion, thick middle = belly (so large muscles are fusiform). Pairs: flexor–extensor (bend–straighten), abductor–adductor (away from–towards body axis; deltoid–latissimus dorsi), pronator–supinator (palm down–up), levator–depressor, protractor–retractor; sphincter = circular muscle (closes/opens).

  • Easy : Flexor bends; extensor straightens.
  • Medium : Abduct = away; adduct = adjacent.
  • Exam-type (CET) : Origin fixed; insertion moves.
Remember

A-A-S: Agonist, Antagonist, Synergist; Ab = Away, Ad = Adjacent.

Common mistake and CET trap

‘Muscles push’ is wrong (only pull). Trap: ‘tendon joins bone to bone’ is wrong (that is a ligament).

Shortcut

Memory clue : "Biceps = Bend; Triceps = straighTen".

Spot the difference

PairActionExample
Flexor / Extensorbend / straightenBiceps / Triceps
Abductor / Adductoraway / towardsDeltoid / Lat. dorsi
Pronator / Supinatorpalm down / upforearm

Practice questions

Easy
  1. 1What is locomotion?
  2. 2Four types of locomotion.
  3. 3What is a tendon?
Medium
  1. 4Example of antagonist?
  2. 5What is the origin?
  3. 6What does an abductor do?
Challenging
  1. 7Where are sphincters?
  2. 8Can a muscle push?
Show answers (try them yourself first)
  1. 1Movement of the whole body.
  2. 2Amoeboid, ciliary, flagellar, muscular.
  3. 3Band joining muscle to bone.
  4. 4Triceps (to biceps).
  5. 5End on the fixed bone.
  6. 6Moves a part away from the body.
  7. 7Anus, stomach openings.
  8. 8No; only pulls.

Mechanism of muscle contraction

From daily life

Two people pulling a rope hand-over-hand come closer; actin and myosin slide in the same way.

Simple definition

The contractile unit is the sarcomere (actin + myosin). Sliding filament theory (H. E. Huxley and A. F. Huxley): actin slides over myosin.

Sliding filamentSarcomere and sliding filamentsZZActin (thin)Myosin (thick)In contraction Z lines move closer; actin slides inwardMyosin: heavy + light chains; head = ATPase; ~55% of proteinActin: F actin (G actin chain) + tropomyosin + troponinRest: tropomyosin covers actin's active sites1 Impulse → T tubule → Ca⁺⁺ into sarcoplasm2 Ca⁺⁺ binds troponin → active site uncovered3 Myosin head splits ATP; binds actin (cross bridge)4 Head tilts → pulls actin inwardRelaxation: Ca⁺⁺ returns; complex re-covers; needs ATPRigor mortis: ATP runs out → myosin cannot detach

In the figure : Sarcomere and the steps of contraction.

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Mechanism of muscle contraction

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Rule 1 : Structure of myosin and actin — Myosin (thick; ~55% of muscle protein): two heavy chains coiled together; the end folds into a globular head (cross bridge); light chains on each head; the head has ATPase (splits ATP). Actin (thin): F actin (double strand of G actin), tropomyosin (covers myosin-binding sites at rest) and troponin (binds actin, tropomyosin and Ca⁺⁺; starts contraction).

  • Easy : Myosin head = ATPase.
  • Medium : Troponin binds Ca⁺⁺.
  • Exam-type (CET) : Tropomyosin = the lid.

Rule 2 : Contraction and relaxation — A motor impulse spreads over the sarcolemma from the motor end plate → T tubule → sarcoplasmic reticulum releases Ca⁺⁺. Ca⁺⁺ binds troponin → troponin–tropomyosin shifts → actin sites uncovered. The myosin head splits ATP for energy, binds the site (actomyosin), tilts back and pulls actin inward → sarcomere shortens → contraction. Relaxation is the reverse: actomyosin breaks (needs ATP), Ca⁺⁺ is pumped back (needs energy), the complex re-covers the sites. Both contraction and relaxation are active processes.

  • Easy : Ca⁺⁺ = the contraction switch.
  • Medium : ATP needed for pulling and release.
  • Exam-type (CET) : Rigor mortis: ATP runs out.
Remember

I-C-U-A-T: Impulse → Ca⁺⁺ → Uncover → Attach → Tilt.

Common mistake and CET trap

‘Relaxation is passive’ is wrong (needs ATP). Trap: ‘filaments shorten’ is wrong (they slide).

Shortcut

Memory clue : "ATP = the ticket that releases myosin".

Spot the difference

ProteinRole
MyosinATPase head; pulls actin
Actinthin filament; active sites
Tropomyosincovers the sites
Troponinbinds Ca⁺⁺

Practice questions

Easy
  1. 1What is a sarcomere?
  2. 2Whose theory is sliding filament?
  3. 3Role of myosin head?
Medium
  1. 4What covers sites at rest?
  2. 5Source of Ca⁺⁺?
  3. 6Ca⁺⁺ binds what?
Challenging
  1. 7Why ATP in relaxation?
  2. 8Cause of rigor mortis?
Show answers (try them yourself first)
  1. 1Contractile unit of muscle.
  2. 2H. E. and A. F. Huxley.
  3. 3Splits ATP; pulls actin.
  4. 4Tropomyosin.
  5. 5Sarcoplasmic reticulum.
  6. 6Troponin.
  7. 7To release myosin and pump Ca⁺⁺.
  8. 8No ATP after death, so myosin stays bound.

Properties of muscle, levers and muscle disorders

From daily life

After heavy lifting you tire and ache; muscle builds lactic acid and you pant afterwards.

Simple definition

Muscle responses to stimulation: twitch, summation, tetanus, refractory period, threshold, all-or-none. Bone + joint + muscle form a lever.

Properties and leversMuscle properties and leversTwitchone stimulus: latent → contraction → relaxationSummationstimulus before relaxing → more tensionTetanusvery rapid stimuli → sustained contractionRefractory~0.02 s no response after a stimulusThresholdminimum stimulus; all-or-noneO₂ debtlactic acid → fatigue, cramps; extra O₂ laterClass Ihead–atlasF in middleClass IIraising on toesR in middleClass IIIelbow flexionE in middleF = fulcrum (joint); E = effort (muscle); R = resistance (load)Rigor mortis = muscles stiffen hours after deathOxygen debt: oxidises lactic acid + restores CP/ATPCreatine phosphate = quick energy store in muscleBody = lever: joint is fulcrum, muscle is effort

In the figure : Muscle properties and the three lever classes.

Rule 1 : Properties on electrical stimulation — Twitch: contraction to one brief stimulus — latent, contraction and relaxation stages. Summation: a stimulus before the previous twitch ends → greater tension (staircase). Tetanus: stimuli so rapid that there is no time to relax → sustained contraction. Refractory period: ~0.02 s after a stimulus with no response. Threshold: minimum strength needed. All-or-none: below threshold = no contraction; at threshold = full force; a stronger stimulus adds no force.

  • Easy : Tetanus = sustained contraction.
  • Medium : All-or-none: a fibre contracts fully or not at all.
  • Exam-type (CET) : Refractory ≈ 0.02 s.

Rule 2 : Oxygen debt, levers, disorders — In strenuous exercise O₂ is short → anaerobic glycolysis → lactic acid builds up → tiredness, pain, cramps. During recovery extra O₂ oxidises lactic acid and refills creatine phosphate + ATP = oxygen debt. Levers: Class I (head–atlas), Class II (rising on toes: toes are fulcrum), Class III (elbow flexion: biceps is effort). Disorders: muscular dystrophy (inherited muscle wasting; Duchenne in boys); myasthenia gravis (autoimmune; antibodies on ACh receptors → weak eyelids, swallowing, speech).

  • Easy : Lactic acid = fatigue.
  • Medium : Class III: elbow (biceps).
  • Exam-type (CET) : Myasthenia: neuromuscular junction.
Remember

T-S-T-R-T-A: Twitch, Summation, Tetanus, Refractory, Threshold, All-or-none.

Common mistake and CET trap

‘Oxygen debt = low O₂’ is wrong (extra O₂ taken afterwards). Trap: ‘dystrophy is autoimmune’ is wrong (inherited).

Shortcut

Memory clue : "Debt = repay later with extra O₂".

Spot the difference

DisorderCause
Muscular dystrophyinherited
Myasthenia gravisautoimmune; ACh receptors
CrampsLactic acid

Practice questions

Easy
  1. 1What is a twitch?
  2. 2When does tetanus occur?
  3. 3Length of refractory period?
Medium
  1. 4What is all-or-none?
  2. 5Cause of fatigue?
  3. 6What is oxygen debt?
Challenging
  1. 7Raising on toes is which lever?
  2. 8Why creatine phosphate?
Show answers (try them yourself first)
  1. 1Contraction to a single stimulus.
  2. 2When stimuli are very rapid.
  3. 3~0.02 s.
  4. 4A fibre contracts fully or not at all.
  5. 5Lactic acid.
  6. 6Extra O₂ used in recovery.
  7. 7Class II.
  8. 8To regenerate ATP quickly.

Skeletal system and skull

From daily life

Like a building's frame, the skeleton gives the body shape and protection.

Simple definition

An adult human has 206 bones: axial (80) and appendicular (126). The skull has 22 bones (cranium 8 + face 14).

Skeleton and skullSkeleton: 206 bonesAxial = 80Appendicular = 126Skull22 = cranium 8 + face 14Hyoid1Ear ossicles6Vertebral column26Sternum1Ribs24Pectoral girdle4Upper limbs60Pelvic girdle2Lower limbs60Skull: cranium (8) + face (14)Cranium: frontal, 2 parietal, 2 temporal, occipital, sphenoid, ethmoidForamen magnum (occipital): medulla ↔ spinal cordSella turcica (sphenoid): pituitary glandMandible = only movable skull bone; largestSutures: coronal, sagittal, lambdoid, squamousHyoid: U-shaped, joins no other boneFontanelles 6: soft until ~2 years

In the figure : Divisions of the skeleton and the skull.

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Skeletal system and skull

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Rule 1 : Skeleton: functions and divisions — The skeleton is cartilage (pliable) and bone (hard matrix); roles: shape, protection, muscle attachment, movement at joints, Ca store, haemopoiesis. Exoskeleton (nails, hair, horns, scales) and endoskeleton. Axial 80 = skull (cranium 8 + face 14) + hyoid 1 + ear ossicles 6 + vertebral column 26 + sternum 1 + ribs 24. Appendicular 126 = girdles + limb bones.

  • Easy : 80 + 126 = 206.
  • Medium : Axial = on the axis; appendicular = appendages.
  • Exam-type (CET) : Bones = Ca store + blood-cell formation.

Rule 2 : Bones of the skull — Cranium (8): frontal (1), parietal (2), temporal (2), occipital (1), sphenoid (1), ethmoid (1). Occipital: foramen magnum (medulla ↔ spinal cord) + occipital condyles (fit atlas). Sphenoid: butterfly-shaped; sella turcica holds the pituitary. Temporal: zygomatic arch, mandibular fossa. Face (14): nasal 2, maxilla 2, palatine 2, zygomatic 2, lacrimal 2, inferior nasal conchae 2, vomer 1, mandible 1 (largest; only movable). Hyoid: U-shaped, articulates with no bone. Sutures: coronal, sagittal, lambdoid, squamous. In infants 6 fontanelles ossify by ~2 years.

  • Easy : 8 + 14 = 22.
  • Medium : Foramen magnum = brain ↔ cord.
  • Exam-type (CET) : Mandible = the only movable one.
Remember

Cranium: F-P-T-O-S-E (Frontal, Parietal, Temporal, Occipital, Sphenoid, Ethmoid).

Common mistake and CET trap

‘Hyoid has joints’ is wrong. Trap: ‘skull = 29 bones’ is wrong (22; ossicles 6 + hyoid counted separately).

Shortcut

Memory clue : "206 = 80 + 126; ‘Mandible Moves’".

Spot the difference

PartBones
Cranium8
Face14
Ear ossicles6 (malleus, incus, stapes ×2)
Axial total80

Practice questions

Easy
  1. 1Adult bones?
  2. 2Axial total?
  3. 3Skull bones?
Medium
  1. 4Where is the foramen magnum?
  2. 5Role of sella turcica?
  3. 6Movable skull bone?
Challenging
  1. 7What is a fontanelle?
  2. 8Four sutures?
Show answers (try them yourself first)
  1. 1206.
  2. 280.
  3. 322 (8 + 14).
  4. 4In the occipital bone.
  5. 5Holds the pituitary gland.
  6. 6Mandible.
  7. 7Soft spot in an infant's skull.
  8. 8Coronal, sagittal, lambdoid, squamous.

Vertebral column, ribs and sternum

From daily life

The backbone bends like a flexible rod yet protects the spinal cord.

Simple definition

The vertebral column = a chain of vertebrae: 33 in a child, 26 in adults. The thoracic cage = 12 thoracic vertebrae + 12 pairs of ribs + sternum.

Vertebral column and thoracic cageVertebral column, ribs, sternumCervical 7Thoracic 12Lumbar 5Sacral 5 → 1Coccygeal 4 → 133 in a child → 26 in adultsAtlas (C1): no centrum; ‘Yes’ jointAxis (C2): odontoid process; ‘No’ pivot jointC7: vertebra prominens; straight spineThoracic: heart-shaped centrum; rib facetsLumbar: kidney-shaped centrum; strongestNeural arch → neural canal → spinal cordCurves: cervical, lumbar (secondary); thoracic, sacral (primary)Ribs 12 pairs: true 1–7; false 8–10; floating 11–12Sternum: manubrium + body + xiphoid; ~15 cmRib's head + tubercle meet the vertebraIntervertebral disc: shock absorber; slipped disc

In the figure : Regions of the column, ribs and sternum.

Rule 1 : Vertebrae and curves — Regions: cervical 7, thoracic 12, lumbar 5, sacral 5 (fused = sacrum), coccygeal 4 (fused = coccyx) → 26. Each vertebra has a centrum, a neural arch enclosing the vertebral foramen (together the neural canal; spinal cord), neural spine, transverse processes, zygapophyses, intervertebral foramen (spinal nerve). Atlas (C1): no centrum; ‘Yes’ joint with occipital condyles. Axis (C2): odontoid process → ‘No’ pivot joint. C3–C6: bifid spine; C7: vertebra prominens. Thoracic: heart-shaped centrum; lumbar: kidney-shaped. Four curves: cervical + lumbar (secondary), thoracic + sacral (primary) — balance, shock absorption. Intervertebral discs absorb shocks.

  • Easy : 7-12-5-5-4 = 33 → 26.
  • Medium : Atlas = Yes; Axis = No.
  • Exam-type (CET) : Neural canal = spinal cord.

Rule 2 : Ribs and sternum — Rib: C-shaped; head + tubercle meet the thoracic vertebra; 12 pairs. True ribs 1–7 (directly to sternum by costal cartilage); false ribs 8–10 (attached to the 7th); floating ribs 11–12 (no front attachment). Space between ribs = intercostal space (for muscles). Sternum ~15 cm: manubrium (clavicle + first 2 ribs), body, xiphoid process (cartilage at first, ossifies in adults; diaphragm attachment). About 8% of people have an extra ‘gorilla rib’ on the lumbar vertebra.

  • Easy : True 7 + False 3 + Floating 2 = 12.
  • Medium : Xiphoid = lowest part of sternum.
  • Exam-type (CET) : Costal cartilage joins rib to sternum.
Remember

C-T-L-S-C = 7-12-5-5-4.

Common mistake and CET trap

‘Atlas has a centrum’ is wrong. Trap: ‘floating ribs are 8–10’ is wrong (11–12).

Shortcut

Memory clue : "7 true, 3 false, 2 floating (7-3-2)".

Spot the difference

TypePairs
True1–7
False8–10
Floating11–12

Practice questions

Easy
  1. 1Vertebrae in a child?
  2. 2In an adult?
  3. 3Number of cervical vertebrae?
Medium
  1. 4Feature of atlas?
  2. 5Where is the odontoid process?
  3. 6True ribs?
Challenging
  1. 7Floating ribs?
  2. 8Parts of sternum?
Show answers (try them yourself first)
  1. 133.
  2. 226.
  3. 37.
  4. 4No centrum; ‘Yes’ joint.
  5. 5On the axis (C2).
  6. 6Pairs 1–7.
  7. 7Pairs 11–12.
  8. 8Manubrium, body, xiphoid.

Appendicular skeleton

From daily life

Limb bones attach to the trunk through the shoulder and hip, like branches to a trunk.

Simple definition

The appendicular skeleton = girdles (pectoral, pelvic) + limb bones; total 126.

Limbs and girdlesAppendicular skeleton: 126Upper limb = 60Clavicle 2 + Scapula 2Humerus 2 · Radius 2 · Ulna 2Carpals 16 · Metacarpals 10Phalanges 28each limb = 30Lower limb = 60Hip bone 2 (ilium, ischium, pubis)Femur 2 · Patella 2Tibia 2 · Fibula 2Tarsals 14 · Metatarsals 10Phalanges 28Scapula: glenoid cavity (humerus head); acromion, coracoidClavicle: S-shaped; links sternum + acromionHumerus: tubercles + bicipital groove; trochleaRadius = thumb side; ulna = olecranon (elbow)Acetabulum: formed by three bones; femur headFemur = longest; patella = sesamoid boneTibia thick; fibula slender; malleoli at the anklePhalanges: 3 per finger, 2 in thumb

In the figure : Limb bones and counts.

Rule 1 : Pectoral girdle and upper limb — Pectoral girdle: each side has a clavicle (S-shaped; sternum + acromion) and a scapula (triangular; glenoid cavity receives the humerus head; acromion, coracoid). Upper limb (30 each): humerus (greater/lesser tubercle, bicipital groove, trochlea), radius (thumb side) and ulna (olecranon = elbow), carpals 8, metacarpals 5, phalanges 14 (3 per finger, 2 in thumb).

  • Easy : Humerus head → glenoid.
  • Medium : Radius = thumb side.
  • Exam-type (CET) : Arm: 3 + 8 + 5 + 14 = 30.

Rule 2 : Pelvic girdle and lower limb — Pelvic girdle: two coxal (hip) bones, each ilium + ischium + pubis; acetabulum where the three meet (ball-socket with femur); pubic symphysis in front; obturator foramen between ischium and pubis. Lower limb (30 each): femur (longest; head, neck, trochanters, condyles), patella (sesamoid, kneecap), tibia (thick) and fibula (slender), tarsals 7 (talus, calcaneum…), metatarsals 5, phalanges 14.

  • Easy : Acetabulum = hip socket.
  • Medium : Femur is the longest.
  • Exam-type (CET) : Tarsals = ankle bones.
Remember

Arm 30 = 3 + 8 + 5 + 14. Leg 30 = 4 + 7 + 5 + 14.

Common mistake and CET trap

‘Carpals are in the foot’ is wrong (tarsals). Trap: ‘fibula is thick’ is wrong (tibia).

Shortcut

Memory clue : "Carpal = wrist (hand); tarsal = ankle (foot)".

Spot the difference

ArmLeg
HumerusFemur
Radius, UlnaTibia, Fibula
CarpalsTarsals
MetacarpalsMetatarsals

Practice questions

Easy
  1. 1Appendicular bones?
  2. 2What is the glenoid cavity?
  3. 3Clavicle joins what?
Medium
  1. 4Carpals in a hand?
  2. 5Longest bone?
  3. 6Where is the acetabulum?
Challenging
  1. 7Type of patella?
  2. 8Tarsals in a foot?
Show answers (try them yourself first)
  1. 1126.
  2. 2Socket for the humerus head.
  3. 3Sternum + acromion.
  4. 48.
  5. 5Femur.
  6. 6On the hip bone (where 3 bones meet).
  7. 7Sesamoid.
  8. 87.

Joints and disorders of bones and joints

From daily life

A door hinge opens one way; the shoulder turns in every direction.

Simple definition

A joint = where two or more bones meet. Three types: fibrous (fixed), cartilaginous (slightly movable), synovial (freely movable).

Joints and disordersJoints and disordersFibrous (fixed)CartilaginousSynovial (free)Suture · Syndesmosis · GomphosisSynchondrosis · SymphysisPivot, Ball-socket, Hinge,Condyloid, Saddle, GlidingPivotatlas–axis (No)Ball-socketshoulder, hipHingeelbow, kneeCondyloidwrist, knucklesSaddlethumb carpometacarpalGlidingintercarpal, intertarsalSynovial: cavity + hyaline cartilage + synovial fluid (hyaluronic acid) + ligamentMuscular dystrophygenetic; muscle wasting (Duchenne = boys)Myasthenia gravisautoimmune; ACh receptors blocked; eyelids, swallowingOsteoarthritiscartilage wears; age, obesityGouturic acid crystals in joints; foot jointsRheumatoidautoimmune; synovial swelling; pannusOsteoporosisporous bones; low Ca; estrogen fall; more in womenSutures: butt, scarf, lap, serrate

In the figure : Joint types and disorders.

Rule 1 : Fibrous, cartilaginous and synovial joints — Fibrous (synarthrosis): bones held by fibrous tissue, no movement — sutures (skull; butt, scarf, lap, serrate), syndesmosis (tibia–fibula membrane), gomphosis (tooth–jaw). Cartilaginous (amphiarthrosis): synchondrosis (hyaline; epiphyseal plate, rib–sternum) and symphysis (fibrocartilage; intervertebral disc, pubic symphysis). Synovial (diarthrosis): synovial cavity, hyaline cartilage on the bones, synovial membrane (makes the fluid), synovial fluid (hyaluronic acid; lubricates, absorbs shock, nourishes), ligaments.

  • Easy : Synarthrosis = fixed.
  • Medium : Synovial = cavity + fluid.
  • Exam-type (CET) : Symphysis = midline.

Rule 2 : Synovial joint types and disorders — Pivot (atlas–axis; rotation only), ball-and-socket (shoulder, hip; all directions), hinge (elbow, knee; flexion–extension), condyloid (wrist; 2 axes), saddle (thumb carpometacarpal; a human feature), gliding (intercarpal, intertarsal). Disorders: osteoarthritis (cartilage degenerates), gout (uric acid salts in joints), rheumatoid arthritis (autoimmune; synovial swelling, pannus), osteoporosis (porous bones; low Ca/estrogen/vit D; more in women) — Ca and exercise from youth help.

  • Easy : Ball-socket = all directions; hinge = one.
  • Medium : Gout = uric acid.
  • Exam-type (CET) : Rheumatoid = autoimmune.
Remember

P-B-H-C-S-G: Pivot, Ball, Hinge, Condyloid, Saddle, Gliding.

Common mistake and CET trap

‘Gout is autoimmune’ is wrong (uric acid). Trap: ‘intervertebral disc is fibrous’ is wrong (symphysis).

Shortcut

Memory clue : "Shoulder = sphere (ball); elbow = door (hinge)".

Spot the difference

JointExample
PivotAtlas–axis
Ball-socketShoulder, hip
HingeElbow, knee
SaddleThumb base

Practice questions

Easy
  1. 1What is a joint?
  2. 2Three types.
  3. 3Example of gomphosis?
Medium
  1. 4Role of synovial fluid?
  2. 5Shoulder joint?
  3. 6Cause of gout?
Challenging
  1. 7Type of rheumatoid arthritis?
  2. 8Preventing osteoporosis?
Show answers (try them yourself first)
  1. 1Meeting point of bones.
  2. 2Fibrous, cartilaginous, synovial.
  3. 3Tooth in jaw.
  4. 4Lubricates, absorbs shock, nourishes.
  5. 5Ball-and-socket.
  6. 6Uric acid salts.
  7. 7Autoimmune.
  8. 8Calcium diet and exercise.

Quick revision of the whole lesson

ConceptKey fact
LocomotionAmoeboid, ciliary, flagellar, muscular
ContractionCa⁺⁺ → troponin; ATP; sliding
PropertiesTwitch, tetanus, all-or-none
Skeleton206 = 80 + 126
Column7-12-5-5-4 → 26
Limbs30 bones per limb
JointsFibrous, cartilaginous, synovial

🎯 Most important points for the exam

  • Muscle pairs.
  • Steps of sliding filament.
  • Oxygen debt, levers.
  • Skeleton 80 + 126.
  • Vertebrae and ribs.
  • Limb bones.
  • Joints and disorders.
Study mantra

Understand the concept → draw the figure → memorise the key points → solve questions yourself.