sseeccoonndd eeddiittiioonn

AANNAATTOOMMYY

RREEVVIISSIIOONN OOFF TTHHEE

UUPPPPEERR LLIIMMBB ,,

LLOOWWEERR LLIIMMBB

&& BBAACCKK

NN II MM AA

RR AA ZZ II II

ANATOMY REVISION OF THE

UPPER LIMB, LOWER LIMB

& BACK

Second Edition

This book is sponsored by the Medical Protection Society and Wesleyan Medical Sickness:

medicalprotection.org/uk/students insight.wesleyan.co.uk/juniordoctors

www.mps.org.uk www.wesleyan.co.uk

Copyright © 2012 by Nima Razii

All rights reserved

1

p r e f a c e

Fellow Medic,

The first edition of Anatomy Revision of the Upper Limb, Lower Limb & Back was compiled in 2009, intended as a study aid for medical students. I hoped it would prove to be of some benefit during those challenging times of revising - that I remember all too well from my own first year in medicine - when an examination or viva was impending, and the 1000 + pages of Gray’s Anatomy for Students seemed somewhat overwhelming to browse through!

I could not have imagined at the time, that what started out as a series of diagrams and annotations, would develop into something that has been so well received. I am incredibly grateful to have obtained so much constructive feedback from students and staff alike throughout the process, and I have attempted to incorporate as many of the practical suggestions I received as possible into this second edition of the publication.

Naturally, this guide does not, by any means, intend to be a replacement for comprehensive anatomy textbooks and atlases – such as Gray’s or McMinn’s – but is rather designed to complement them as a lighter way of revising and / or reminding yourself of some of the more fundamental anatomical features of the upper limb, lower limb and back that you are likely to be tested on.

Looking beyond exams and assessments, I hope you also develop an enjoyment of anatomy and an appreciation of the marvel of nature that is the human body.

Finally, the very best of luck in all your medical studies, now and in the future.

Sincerely,

Many thanks to the staff of the Department of Anatomy at the School of Biosciences, Cardiff University, without whom the writing of this guide would have been impossible,

and for promoting the study of anatomy in a practical & engaging manner.

2

i n t r o d u c t i o n The study of anatomy can seem daunting, as the human body is a complex system in terms of both structure and function. However, the fact remains that a sound grasp of anatomy is essential in any branch of medicine. Fortunately, there are ways to familiarize oneself with the way in which the body’s structures are organized and also to develop the propensity for viewing the human body from a clinical perspective. For the purposes of this revision guide, we will introduce the anatomy to each body section with an overview of the fundamental movements of that area. Learning these early on will prove useful, not only in further studies, but also in a clinical context, where terms relating to anatomical movements are frequently used.

Following this, the osteology of each region is considered, with the important features and prominences of bones being labelled in highlighted black text, and sites of muscle attachments in blue.

Cross-sections of the upper and lower limbs give an indication of the positioning of various structures in relation to each other. Prosections are often used in anatomy examinations, with questions asking for specified structures (e.g. muscles or nerves) to be correctly identified. In the final section, a structured strategy is developed for orientating oneself before going on to identify various individual structures on a cross-section, useful for when under the time constraints of a spotter examination or viva.

Muscles of the upper limb, lower limb and back are arranged into tabulated groups, and the origin, insertion, action, and nervous innervation for each is given.

The major nerves & plexi supplying the upper and lower limbs are illustrated, along with the dermatomes of these regions. Dermatomes are used in neurological examination, as they can indicate the location of damage to spinal nerves, although it is noteworthy that they do overlap, and that there is variation between individuals. The organization of various structures within the vertebral canal is depicted after a section on the anatomy of the vertebral column itself.

Vasculature is a fundamental part of human anatomy, and the distribution of major blood vessels throughout the upper limb, lower limb and back is described and illustrated in turn for each region.

In terms of studying anatomy from a clinical perspective, it is worth adopting a mindset that encourages one to think about the possible consequences arising from certain dysfunctions; accordingly, a section is dedicated to some notable clinical scenarios and commonly associated anatomical causes.

3

c o n t e n t s

page

ANATOMY OF THE UPPER LIMB 4

Upper Limb Osteology 5 – 7

Cross Sectional Anatomy of the Upper Limb 8

Musculature of the Upper Limb 9 – 13

Neurology of the Upper Limb 14 – 15

Vasculature of the Upper Limb 16 – 17

ANATOMY OF THE LOWER LIMB 18

Lower Limb Osteology 19 – 22

Ligaments of the Knee 22

Cross Sectional Anatomy of the Lower Limb 23

Musculature of the Lower Limb 24 – 28

Neurology of the Lower Limb 29 – 30

Vasculature of the Lower Limb 31 – 32

ANATOMY OF THE BACK 33

Structural Anatomy of the Vertebral Column 34 – 35

Structures of the Vertebral Canal 36 – 37

Musculature of the Back 38 – 39

CLINICAL ANATOMY 40 – 41

CROSS SECTIONAL ANATOMY – EXAMINATION TIPS 42

4

ANATOMY OF THE

UPPER LIMB

FUNDAMENTAL MOVEMENTS OF THE UPPER LIMB

Retraction

Flexion

Extension

Pronation

Supination

Palm posterior

Palm anterior

Lateral rotation

Medial rotation

Adduction

Abduction

Protraction

Extension

Flexion

5

UPPER LIMB OSTEOLOGY – SCAPULA

LEFT SCAPULA – POSTERIOR VIEW

LEFT SCAPULA – ANTERIOR VIEW ( Suprascapular nerve passes through

suprascapular notch )

Coracobrachialis, Pectoralis minor & Short head of biceps

Long head of triceps Subscapularis

Serratus Anterior

Levator Scapulae

Supraspinatus

Trapezius

Rhomboid minor

Rhomboid major

Infraspinatus

Latissimus dorsi

Teres major

Teres minor

Long head of triceps

Deltoid

Coracobrachialis, Pectoralis minor & Short head of biceps

Long head of biceps

6

UPPER LIMB OSTEOLOGY – SHOULDER UPPER LIMB OSTEOLOGY – WRIST

RIGHT PROXIMAL HUMERUS – ANTERIOR &

POSTERIOR VIEWS

Triquetrum and styloid process of ulna lie

posterior to pisiform, which in turn cannot be

seen when hand is pronated.

CARPAL BONES RIGHT HAND

RIGHT DISTAL ULNA & RADIUS – ANTERIOR VIEW

SUPINATED POSITION Brachioradialis

Pronator quadratus

Subscapularis

Supraspinatus Supraspinatus

Infraspinatus

Teres Minor

Lateral head of triceps

Medial head of triceps

Brachialis

Teres major

Latissimus dorsi

Deltoid

Pectoralis major

7

UPPER LIMB OSTEOLOGY – ELBOW

RIGHT DISTAL HUMERUS – ANTERIOR, POSTERIOR & LATERAL VIEWS

RIGHT PROXIMAL ULNA – ANTERIOR, POSTERIOR & LATERAL VIEWS

RIGHT PROXIMAL RADIUS – ANTERIOR, POSTERIOR & MEDIAL VIEWS

Flexors Extensors

Brachialis Brachialis

Supinator

Biceps brachii

Triceps brachii

Brachialis Supinator

Brachialis

Trochlea articulates with ulna.

Capitulum articulates with head of radius.

Biceps brachii

Flexor pollicis longus

Brachioradialis

Extensors

Annular ligament

Supinator

8

CROSS-SECTIONAL ANATOMY OF THE ARM & FOREARM

Cephalic vein

Biceps brachii

Brachialis

Musculocutaneous nerve

Median nerve

Brachial artery & veins

Basilic vein

Ulnar nerve

Superior ulnar collateral artery

Humerus

Radial nerve

Profunda brachii artery

Triceps brachii

Posterior cutaneous nerve

Brachioradialis Cephalic vein Radial nerve, artery & veins Lateral cutaneous nerve Flexor carpi radialis Palmaris longus

Medial cutaneous nerve

Flexor digitorum superficialis

Flexor pollicis longus

Median nerve

Flexor carpi ulnaris

Ulnar nerve, artery & veins

Radius

Anterior interosseous nerve & artery

Basilic vein

Interosseous membrane

Extensor pollicis longus

Ulna

Flexor digitorum profundus Extensor carpi ulnaris Posterior interosseous artery

Extensor digiti minimi

Abductor pollicis longus

Extensor digitorum

Extensores carpi radiales (longus & brevis)

MUSCULATURE OF THE AXILLA, ARM & FOREARM

ORIGIN INSERTION INNERVATION

ACTION

TRAPEZIUS Ligamentum Nuchae; Spinous processes of C7-T12

Lateral third of clavicle; Acromion;

Spine of scapula Accessory nerve

Elevates shoulder & rotates scapula during abduction of humerus above

horizontal; middle fibres retract scapula; lower fibres depress scapula

DELTOID Lateral third of clavicle ; Acromion ; Spine of scapula

Deltoid tuberosity of humerus Axillary nerve Abducts arm beyond initial 15° (accomplished by supraspinatus)

LEVATOR SCAPULAE Transverse processes of C1-C4 Upper medial border of scapula C3 & C4 anterior rami; Dorsal scapular nerve

Elevates scapula

RHOMBOID MAJOR Spinous processes of T2-T5 Lower medial border of scapula

Dorsal scapular nerve

Retracts (adducts) & elevates scapula RHOMBOID MINOR Ligamentum Nuchae;

Spinous processes of C7 & T1 Medial border at spine of scapula

ROTATOR CUFF MUSCLES are designed to stabilize the shoulder (glenohumeral joint) by attaching the humerus to their respective scapular fossae:

SUPRASPINATUS Supraspinous fossa

Greater tubercle of humerus

Suprascapular nerve Abducts arm up to 15°

INFRASPINATUS Infraspinous fossa Laterally (externally) rotates arm

TERES MINOR Lateral border of scapula Axillary nerve

SUBSCAPULARIS Subscapular fossa Lesser tubercle of humerus Subscapular nerve Medially (internally) rotates arm

9

ORIGIN INSERTION INNERVATION ACTION

TERES MAJOR Posterior surface of inferior angle of scapula

Intertubercular groove on anterior surface of humerus

Subscapular nerve Medially (internally) rotates & extends arm at glenohumeral joint

PECTORALIS MAJOR

Clavicular head : Anterior surface of clavicle Sternocostal head : Sternum ; costal cartilages 1-7 ; aponeurosis of external oblique

Lateral edge of intertubercular

groove of humerus

Medial & lateral pectoral nerves

Flexes, adducts & medially (internally) rotates arm at glenohumeral joint

PECTORALIS MINOR Ribs 3-5 Coracoid process of scapula Medial pectoral nerve Depresses shoulder & protracts scapula

SUBCLAVIUS Medial aspect of rib 1 Inferior surface of clavicle Nerve to subclavius Depresses clavicle

SERRATUS ANTERIOR Lateral surfaces of ribs 1-9 Medial border of scapula Long thoracic nerve Protracts, stabilizes & rotates scapula

ANTERIOR COMPARTMENT OF ARM

BICEPS BRACHII Long head : Supraglenoid tubercle of scapula Short head : Apex of coracoid process

Tuberosity of radius

Musculocutaneous nerve

Flexes & supinates forearm

CORACOBRACHIALIS Apex of coracoid process Medial aspect of humerus Flexes & adducts arm

BRACHIALIS Anterior aspect of humerus Tuberosity of ulna Flexes forearm

TRICEPS BRACHII Long head : Infraglenoid tubercle of scapula Medial & lateral heads : Posterior surface of humerus

Olecranon process of ulna

Radial nerve Extends forearm

POSTERIOR COMPARTMENT OF ARM

10

ANTERIOR COMPARTMENT OF FOREARM – Comprises flexors & pronators

ORIGIN INSERTION INNERVATION ACTION

FLEXOR DIGITORUM SUPERFICIALIS

Medial epicondyle of humerus (Common flexor tendon)

Middle phalanges of fingers (except thumb)

Median nerve

Flexes proximal IP joints of fingers (except thumb)

FLEXOR POLLICIS LONGUS

Anterior surface of body of radius; interosseous membrane

Distal phalanx of thumb Flexes MCP & IP joints of thumb

PRONATOR QUADRATUS Distal anteromedial surface of ulna Distal anterior surface of radius

Pronates forearm PRONATOR TERES Medial epicondyle of humerus;

medial aspect of coronoid process Body of radius

PALMARIS LONGUS

Medial epicondyle of humerus _

(Common flexor tendon)

Palmar aponeurosis of hand Flexes wrist

FLEXOR CARPI RADIALIS 2nd & 3rd metacarpals Flexes & abducts wrist

FLEXOR CARPI ULNARIS Pisiform ; ligaments into hamate & 5th metacarpal

Ulnar nerve

Flexes & adducts wrist

FLEXOR DIGITORUM PROFUNDUS

Anteromedial surface of body of ulna; interosseous membrane

Distal phalanges of fingers (except thumb)

Flexes wrist, MCP & distal IP joints of fingers (except thumb)

Distal interphalangeal joints (DIJ) IP: Interphalangeal joints

Proximal interphalangeal joints (PIJ)

MCP: Metacarpophalangeal joints

CMC: Carpometacarpal joints

Midcarpal joint

Distal phalanges

Intermediate phalanges

Proximal phalanges

Metacarpals

Carpal bones

JOINTS OF THE HAND

11

POSTERIOR COMPARTMENT OF FOREARM – Comprises extensors & supinator, innervated by RADIAL NERVE

ORIGIN INSERTION ACTION

BRACHIORADIALIS * Lateral supracondylar ridge of humerus

Distal aspect of radius Flexes forearm at elbow

EXTENSOR CARPI RADIALIS LONGUS Base of 2nd metacarpal Extends & abducts wrist

EXTENSOR CARPI RADIALIS BREVIS

Lateral epicondyle of humerus

(Common extensor tendon)

Base of 2nd & 3nd metacarpals

EXTENSOR CARPI ULNARIS Base of 5th metacarpal Extends & adducts wrist

EXTENSOR DIGITORUM Extensor expansion of middle & distal phalanges of all fingers (except thumb)

Extends all fingers (except thumb) & wrist

EXTENSOR DIGITI MINIMI Extensor expansion of proximal phalanx of little finger

Extends joints of little fingers

ABDUCTOR POLLICIS LONGUS Posterior surfaces of distal radius & ulna ; Interosseous membrane

Lateral aspect of base of 1st metacarpal Abducts CMC joint of thumb ; assists in extension of thumb

EXTENSOR POLLICIS BREVIS Posterior surface of radius Base of proximal phalanx of thumb Extends MCP joint of thumb

EXTENSOR POLLICIS LONGUS Posterior surface of ulna Base of distal phalanx of thumb Extends IP joint of thumb

EXTENSOR INDICIS Posterior surface of distal ulna Extensor expansion of index finger Extends index finger

SUPINATOR Lateral epicondyle of humerus ; Supinator crest of ulna ; Radial collateral & annular ligaments

Lateral aspect of proximal radius Supinates forearm

(* Although categorized in the posterior compartment, Brachioradialis flexes the elbow joint.)

12

UPPER LIMB MUSCLES ANTERIOR VIEW POSTERIOR VIEW

RIGHT UPPER LIMB LEFT UPPER LIMB

Flexor carpi ulnaris

Hypothenar muscles :

Abductor digiti minimi Flexor digiti minimi brevis Opponens digiti minimi

Palmaris brevis

Flexor carpi radialis

Pronator teres

Pectoralis major

Deltoid

Biceps brachii

Serratus anterior

Brachioradialis

Extensor digitorum

Extensor carpi ulnaris

Latissimus dorsi

Triceps brachii

Deltoid

Trapezius

Infraspinatus

Thenar muscles:

Abductor pollicis brevis Flexor pollicis brevis Opponens pollicis Adductor pollicis

Extensores carpi radialis longus & brevis

14

NEUROLOGY OF THE UPPER LIMB

C 4

C 3

T 2

C 5

T 1

C 7

C 6

C 8

POSTERIOR VIEW

C 4

C 6

C 5

T 2

T 1

C 7

C 8

DERMATOMES OF THE UPPER LIMB

ANTERIOR VIEW

C 3

RIGHT UPPER LIMB

LEFT UPPER LIMB

MUSCULOCUTANEOUS NERVE

AXILLARYNERVE

MEDIAN NERVE

RADIAL NERVE

ULNAR NERVE

BRACHIAL PLEXUS

Long thoracic nerve

Medial pectoral nerve

Medial cutaneous nerve of

arm

Medial cutaneous nerve of forearm

Suprascapular

nerve

Lateral pectoral nerve

Thoracodorsal nerve

Nerve to subclavius

Superior subscapular

nerve Inferior subscapular nerve

15

MAJOR NERVES OF THE UPPER LIMB (ANTERIOR VIEW OF RIGHT UPPER LIMB)

Brachial plexus

Musculocutaneous nerve

Axillary nerve

Radial nerve

Median nerve

Interosseous nerve

Ulnar nerve

16

VASCULATURE OF THE UPPER LIMB AXILLARY ARTERY passes medial to head of the humerus and becomes BRACHIAL ARTERY. PROFUNDA BRACHII ARTERY branches off posterior aspect of BRACHIAL ARTERY, passes through radial groove and down lateral side of humerus. BRACHIAL ARTERY passes between lateral and medial epicondyles of humerus and bifurcates in the cubital fossa, giving rise to the RADIAL ARTERY & ULNAR ARTERY. RADIAL ARTERY runs down the anterolateral part of the forearm, between flexor pollicis longus & brachioradialis, and forms the DEEP PALMAR ARCH of the hand. RADIAL ARTERY is accompanied by the RADIAL NERVE. ULNAR ARTERY runs down the anteromedial part of the forearm, between flexor digitorum profundus & superficialis, and forms the SUPERFICIAL PALMAR ARCH of the hand. ULNAR ARTERY is accompanied by ULNAR NERVE. DORSAL VENOUS NETWORK OF THE HAND gives rise to BASILIC & CEPHALIC VEINS. BASILIC VEIN runs up medial aspect of upper limb; CEPHALIC VEIN runs up anterolateral aspect of upper limb. Both are subcutaneous. BASILIC VEIN becomes AXILLARY VEIN, and CEPHALIC VEIN drains into AXILLARY VEIN at the deltopectoral triangle. BASILIC & CEPHALIC VEINS communicate via MEDIAN CUBITAL VEIN, a superficial vein located in the cubital fossa (from where blood is often taken). DEEP VEINS accompany arteries of the upper limb & share their names (e.g. ulnar & radial veins).

17

MAJOR VESSELS OF THE UPPER LIMB (ANTERIOR VIEW OF LEFT UPPER LIMB)

Brachial artery

Brachial vein

Profunda brachii artery

Basilic vein

Axillary artery

Ulnar artery

Cephalic vein

Radial artery

Superficial palmar arch

Anterior interosseous

artery

Deep palmar

arch

Axillary vein

Ulnar vein

Median cubital

vein

Radial vein

Median antebrachial

vein

Dorsal venous network of the hand

18

ANATOMY OF THE

LOWER LIMB

FUNDAMENTAL MOVEMENTS OF THE LOWER LIMB

Extension Flexion Adduction

Abduction

Medial (internal) rotation

Dorsiflexion

Plantarflexion Extension

Flexion

Eversion Inversion

Lateral (external) rotation

19

LOWER LIMB OSTEOLOGY – PELVIS

ANTERIOR VIEW

POSTERIOR VIEW

Iliacus

Sartorius

Quadratus femoris

(Connected to pubic tubercle by inguinal ligament)

Obturator internus

Gluteus medius Gluteus

maximus Gluteus minimus

External oblique

Tensor fasciae

latae

Semimembranosus

Semitendinosus & Long head of biceps femoris

Quadratus femoris

Adductors brevis, longus & magnus

Quadratus externus

Adductor magnus

Piriformis

20

LOWER LIMB OSTEOLOGY – FEMUR & PATELLA

LEFT FEMUR – ANTERIOR & POSTERIOR VIEWS

LEFT PATELLA – POSTERIOR VIEW LEFT PATELLA

ANTERIOR VIEW

Piriformis

Gluteus minimus

Vastus lateralis

Gluteus maximus

Vastus intermedius

Vastus medialis

Psoas major & Iliacus

Quadratus femoris

Obturator externus

Gluteus medius Obturator

internus

Psoas major & Iliacus

Pectineus

Vastus medialis

Adductor magnus

Adductor brevis

Biceps femoris (Short head)

Vastus intermedius

Lateral head of gastrocnemius

Plantaris

Popliteus

Adductor magnus

Medial head of gastrocnemius

Adductor Magnus

Vastus intermedius

Rectus femoris

Vastus lateralis

Vastus medialis

21

LOWER LIMB OSTEOLOGY – TIBIA & FIBULA

LEFT TIBIA – ANTERIOR, POSTERIOR & LATERAL VIEWS

LEFT FIBULA

Interosseous membrane

Soleus

Biceps femoris

Fibularis longus

Fibular collateral ligament

Biceps femoris

Soleus

Tibialis posterior

Fibular collateral ligament

Biceps femoris

Extensor digitorum

longus Fibularis longus

Tibialis posterior

Soleus Popliteus

Tibialis posterior

Tibialis anterior

Semitendinosus

Gracilis

Sartorius Tibialis anterior

Semimembranosus

Vastus medialis Iliotibial

tract

Posterior cruciate ligament Semimembranosus

Iliotibial tract

Extensor digitorum longus

Fibularis longus

Fibularis tertius

22

OSTEOLOGY OF THE FOOT LIGAMENTS OF THE KNEE JOINT

LEFT FOOT –DORSAL SURFACE

MEDIAL VIEW

LATERAL VIEW

RIGHT KNEE (FLEXED) – ANTERIOR VIEW

Fibularis brevis

Extensor digitorum

brevis

Achilles tendon (Calcaneal tendon)

Plantaris

Femur Posterior cruciate ligament

Medial (tibial)

collateral ligament

Medial meniscus

Tibia Fibula

Lateral (fibular) collateral ligament

Lateral meniscus

Anterior cruciate ligament

Fibula

Lateral (fibular)

collateral ligament

Lateral meniscus

Femur

Anterior cruciate ligament

Medial (tibial)

collateral ligament

Tibia

Posterior cruciate ligament

Posterior meniscofemoral

ligament

Medial meniscus

RIGHT KNEE (EXTENDED) – POSTERIOR VIEW

23

CROSS-SECTIONAL ANATOMY OF THE THIGH & LEG

Vastus lateralis Rectus femoris

Vastus intermedius

Femur

Vastus medialis

Profunda femoris artery & vein

Adductor longus

Sartorius

Saphenous nerve

Femoral artery & vein

Great saphenous vein

Adductor magnus

Gracilis Perforating artery & vein

Adductor magnus Semimembranosus

Semitendinosus

Sciatic nerve

Biceps femoris (long head)

Biceps femoris (short head)

Iliotibial tract of fascia lata

Extensores digitorum longus & hallucis

Tibialis anterior

Deep fibular nerve

Anterior tibial artery & vein

Interosseous membrane

Tibia

Flexor digitorum longus

Great saphenous vein

Saphenous nerve

Tibialis posterior

Posterior tibial artery & vein

Tibial nerve

Tendon of plantaris Gastrocnemius

Soleus Fibular artery & vein Gastrocnemius

Medial cutaneous nerve Small saphenous vein Lateral cutaneous nerve

Gastrocnemius

Fibula

Superficial fibular nerve

Fibularis longus & brevis

MUSCULATURE OF THE GLUTEAL REGION, THIGH & LEG

ORIGIN INSERTION INNERVATION

ACTION

TENSOR FASCIAE LATAE Lateral aspect of iliac crest Iliotibial tract of fascia lata Superior gluteal nerve Stabilizes knee during extension

GLUTEUS MAXIMUS Posteromedial aspect of ilium & sacrum

Gluteal tuberosity on posterior aspect of femur & iliotibial tract

Inferior gluteal nerve Extends hip joint ; laterally (externally) rotates & abducts thigh

GLUTEUS MEDIUS External surface of ilium (under gluteus maximus)

Lateral aspect of greater trochanter of femur

Superior gluteal nerve Medially (internally) rotates & abducts thigh

GLUTEUS MINIMUS External surface of ilium (under gluteus medius)

Anterolateral aspect of greater trochanter of femur

PIRIFORMIS Anterior surface of sacrum Medial aspect of greater trochanter of femur

Nerve to piriformis

Laterally (externally) rotates thigh during hip extension ;

abducts thigh during hip flexion

OBTURATOR INTERNUS Ischiopubic ramus & obturator membrane

Medial aspect of greater trochanter of femur Nerve to

obturator internus SUPERIOR GEMELLUS Muscular fasciculi associated with the upper & lower

margins of the obturator internus tendon INFERIOR GEMELLUS Nerve to quadratus femoris QUADRATUS FEMORIS Ischial tuberosity Intertrochanteric crest of femur Laterally (externally) rotates thigh

Piriformis is the landmark muscle of the gluteal region and passes through the greater sciatic foramen. Piriformis syndrome can occur when the sciatic nerve passes through piriformis in 15% of the population, predisposing them to referred pain known as sciatica.

Piriformis, obturator internus, quadratus femoris & gemelli lie deep to the gluteus muscles.

Tensor fasciae latae is the most lateral of the thigh muscles.

24

QUADRICEPS FEMORIS

ANTERIOR COMPARTMENT OF THIGH – Innervated by FEMORAL NERVE

ORIGIN INSERTION ACTION

PSOAS MAJOR Transverse processes of T12 – L5 Lesser trochanter of femur Flexes thigh at hip joint

ILIACUS Iliac fossa

VASTUS MEDIALIS, INTERMEDIUS & LATERALIS

Proximal aspect of femur

Patella via quadriceps femoris tendon

Extends leg at knee joint

RECTUS FEMORIS Anterior inferior iliac spine & iliac boundary of acetabulum Extends leg at knee joint

& flexes thigh at hip joint SARTORIUS Anterior superior iliac spine Anteromedial surface of proximal tibia

PECTINEUS Pectineal line of pubis Posterior aspect of femur (linea aspera) Flexes & adducts thigh

MEDIAL COMPARTMENT OF THIGH – Innervated by OBTURATOR NERVE

GRACILIS Ischiopubic ramus Anteromedial surface of proximal tibia Adducts thigh & flexes leg

ADDUCTOR LONGUS Body of pubis Posterior aspect of femur (linea aspera)

Adducts & medially (internally) rotates thigh ADDUCTOR MAGNUS

Adductor part: Ischiopubic ramus Posterior aspect of femur

Hamstring part: Ischial tuberosity Adductor tubercle & supracondylar line of femur

ADDUCTOR BREVIS Body of pubis & inferior pubic ramus Posterior aspect of proximal femur (linea aspera) Adducts thigh

OBTURATOR EXTERNUS Obturator membrane Trochanteric fossa on greater trochanter of femur

Adducts thigh & laterally (externally) rotates thigh 25

POSTERIOR COMPARTMENT OF THIGH – Innervated by SCIATIC NERVE ORIGIN INSERTION ACTION

HAMSTRINGS

SEMIMEMBRANOSUS Ischial tuberosity

Medial tibial condyle Extends & medially rotates thigh at hip joint ; flexes &

medially rotates leg at knee joint SEMITENDINOSUS Anteromedial surface of proximal tibia

BICEPS FEMORIS Long head : Ischial tuberosity Short head : Linea aspera of femur

Head of fibula Extends & medially rotates thigh ; flexes & laterally rotates leg

ANTERIOR COMPARTMENT OF LEG – Innervated by DEEP FIBULAR NERVE

LATERAL COMPARTMENT OF LEG – Innervated by SUPERFICIAL FIBULAR NERVE

TIBIALIS ANTERIOR Lateral aspect of tibia & interosseous membrane Medial cuneiform & 1st metatarsal Dorsiflexes & inverts foot

EXTENSOR HALLUCIS LONGUS

Medial aspect of fibula & interosseous membrane Dorsal surface on base of distal phalanx of hallux (big toe)

Extends hallux (big toe) & dorsiflexes foot

EXTENSOR DIGITORUM LONGUS

Medial aspect of proximal fibula & lateral tibial condyle

Dorsal surface of middle & distal phalanges of lateral 4 digits

Extends lateral 4 digits & dorsiflexes foot

FIBULARIS TERTIUS Anteromedial aspect of distal fibula Dorsal surface of 5th metatarsal Dorsiflexes & everts foot

FIBULARIS LONGUS Anterolateral aspect of proximal fibula & lateral tibial condyle

Lateral surface of medial cuneiform & 1st metatarsal

Plantarflexes & everts foot

FIBULARIS BREVIS Lateral aspect of fibula Lateral tuberosity of 5th metatarsal Everts foot

26

POSTERIOR COMPARTMENT OF LEG – Comprises superficial & deep groups, innervated by TIBIAL NERVE

DORSAL FOOT MUSCLES – Extensor hallucis brevis , Extensor digitorum brevis

PLANTAR FOOT MUSCLES – Abductor hallucis , Flexor digitorum brevis , Abductor digiti minimi ; Quadratus plantae , Lumbricals ; Flexor hallucis brevis , Adductor hallucis , Flexor digiti minimi brevis ; Dorsal interossei , Plantar interossei

SUPERFICIAL GROUP ORIGIN INSERTION ACTION

GASTROCNEMIUS Medial head : Distal femur, immediately superior to medial femoral condyle Lateral head : Lateral femoral condyle

Posterior aspect of calcaneus (via calcaneal tendon)

Plantarflexes foot & flexes knee

PLANTARIS Lateral surface of lateral femoral condyle

SOLEUS Posterior aspect of proximal fibula; medial border & soleal line of tibia

Plantarflexes foot

DEEP GROUP

TIBIALIS POSTERIOR Posterior aspect of interosseous membrane ; inner posterior borders of tibia & fibula

Navicular & medial cuneiform Inverts & plantarflexes foot

POPLITEUS Lateral femoral condyle Posterior aspect of proximal tibia Plantarflexes foot & flexes knee

FLEXOR HALLUCIS LONGUS Posterior aspect of fibula & interosseous membrane

Plantar surface of distal phalanx of hallux (big toe)

Flexes hallux (big toe)

FLEXOR DIGITORUM LONGUS Posteromedial aspect of tibia Plantar surfaces on bases of distal phalanges of lateral 4 digits

Flexes lateral 4 digits

27

LOWER LIMB MUSCLES ANTERIOR VIEW POSTERIOR VIEW

SUPERFICIAL MUSCLES DEEP MUSCLES DEEP MUSCLES

Extensor hallucis longus

Tensor fasciae

latae

Extensor retinaculum

Soleus

Gastrocnemius

Vastus medialis

Adductor magnus

Psoas major & Iliacus

Pectineus

Adductor longus

Gracilis

Sartorius

Rectus femoris

Vastus lateralis

Iliotibial tract

Fibularis longus, brevis & tertius

Tibialis Anterior

Gastrocnemius

Semitendinosus

Semimembranosus

Biceps femoris

Iliotibial tract

Gluteus maximus

Gluteus medius

Gluteus medius

Piriformis

Obturator internus

Quadratus femoris

Adductor magnus

Semimembranosus

Popliteus

Soleus

Soleus

Flexor hallucis longus

Flexor digitorum longus

Calcaneal tendon (Achilles tendon) SUPERFICIAL

MUSCLES

29

NEUROLOGY OF THE LOWER LIMB

L 1

L 2

L 3

S 3

L 4 L 5

S 1

S 4 L 2

S 3

S 2 L 3

L 4 L 5

S 1 L 5

L 4

DERMATOMES OF THE LOWER LIMB

ANTERIOR VIEW

POSTERIOR VIEW

Common fibular part

Tibial part

SCIATIC NERVE

Pudendal nerve

To levator ani, coccygeus & external anal sphincter Posterior femoral

cutaneous nerve

To quadratus femoris

To obturator internus

SACRAL PLEXUS LUMBAR PLEXUS

Dorsal divisions

Ventral divisions

Iliohypogastric nerve

Ilio-inguinal nerve

Genitofemoral nerve

Lateral cutaneous nerve of thigh

To iliacus & psoas

FEMORAL NERVE

OBTURATOR NERVE

To piriformis

Inferior gluteal nerve

Superior gluteal nerve

30

MAJOR NERVES OF THE LOWER LIMB (POSTERIOR VIEW OF RIGHT LOWER LIMB)

Obturator nerve

Sciatic nerve

Common fibular (peroneal) nerve

Superficial fibular (peroneal) nerve

Tibial nerve

Saphenous nerve

Femoral nerve

Deep fibular (peroneal) nerve

31

VASCULATURE OF THE LOWER LIMB COMMON ILIAC ARTERY bifurcates in front of the sacrum to form EXTERNAL & INTERNAL ILIAC ARTERIES. SUPERIOR & INFERIOR GLUTEAL ARTERIES branch off INTERNAL ILIAC ARTERY in the pelvic cavity, and supply gluteal region via greater sciatic foramen. OBTURATOR ARTERY supplies medial compartment of the thigh via obturator foramen after branching off INTERNAL ILIAC ARTERY. FEMORAL ARTERY begins where EXTERNAL ILIAC ARTERY passes under the inguinal ligament to enter anterior aspect of upper thigh. PROFUNDA FEMORIS ARTERY (DEEP ARTERY OF THE THIGH) branches off in femoral triangle on lateral side & travels down posteriorly adjacent to femur; from it originate LATERAL & MEDIAL CIRCUMFLEX ARTERIES and 3 PERFORATING BRANCHES which pass through adductor magnus to supply posterior compartment of thigh. FEMORAL ARTERY passes through adductor hiatus in adductor magnus, becoming POPLITEAL ARTERY, which in turn bifurcates, giving rise to POSTERIOR & ANTERIOR TIBIAL ARTERIES (the latter of which passes through aperture in interosseous membrane to supply anterior leg compartment). FIBULAR ARTERY branches off POSTERIOR TIBIAL ARTERY, running laterally adjacent to it. It has a PERFORATING BRANCH to the POSTERIOR TIBIAL ARTERY, and a COMMUNICATING BRANCH to the ANTERIOR TIBIAL ARTERY. LATERAL & MEDIAL PLANTAR ARTERIES supply the sole of the foot, arising from the POSTERIOR TIBIAL ARTERY. DORASLIS PAEDIS ARTERY supplies dorsal aspect of the foot, arising from the ANTERIOR TIBIAL ARTERY. DORSAL VENOUS ARCH OF THE FOOT gives rise to SMALL & GREAT SAPHENOUS VEINS (superficial veins of the lower limb). GREAT SAPHENOUS VEIN runs up medial side of leg, passing over medial epicondyle of femur before tending toward anterior aspect of thigh, joining FEMORAL VEIN at the saphenofemoral junction in the femoral triangle.

32

SMALL SAPHENOUS VEIN runs up posterior aspect of leg, before passing between the heads of gastrocnemius and draining into the POPLITEAL VEIN at the knee. FIBULAR VEIN drains into POSTERIOR TIBIAL VEIN, which joins with ANTERIOR TIBIAL VEIN before contributing to the POPLITEAL VEIN. POPLITEAL VEIN becomes FEMORAL VEIN at the adductor canal. FEMORAL VEIN drains into EXTERNAL ILIAC VEIN, which in turn joins INTERNAL ILIAC VEIN at the level of the pelvic brim to form the COMMON ILIAC VEIN. INTERNAL ILIAC VEIN initially receives OBTURATOR & GLUTEAL VEINS, amongst others from the pelvis & perineum.

MAJOR VESSELS OF THE LOWER LIMB (ANTERIOR VIEW OF LEFT LOWER LIMB)

Common iliac artery External

iliac artery Internal

iliac artery

Profunda femoris artery

Profunda femoris

vein

Femoral artery

Popliteal artery Anterior tibial artery

Posterior tibial artery Fibular

artery

Dorsalis paedis artery

Lateral plantar artery

External iliac vein

Common iliac vein

Femoral vein

Great saphenous

vein Popliteal

vein

Posterior tibial vein

Anterior tibial vein

Dorsal venous

arch

Small saphenous

vein

33

ANATOMY OF THE

BACK

FUNDAMENTAL MOVEMENTS OF THE BACK

Extension

Flexion

Lateral flexion Rotation

34

STRUCTURAL ANATOMY OF THE VERTEBRAL COLUMN

Vertebral column comprises 33 vertebrae: 7 cervical, 12 thoracic, 5 lumbar, 5 sacral (fused), 4 coccygeal (fused). Each vertebra (with the exception of C1 & C2) consists of a vertebral body, located anteriorly, and a vertebral arch (where most of the prominences and features are to be found), situated posterior to the body and surrounding the vertebral canal. Cervical vertebrae are distinguished by foramen transversarium, through which vertebral arteries pass, and also bifid spinous processes. Atlas (C1) and axis (C2) are atypical and have special distinguishing features (see diagram). Thoracic vertebrae are distinguished by the presence of facets on the sides of vertebral bodies for articulation with the heads of ribs, and long spinous processes directed obliquely downwards. Lumbar vertebrae are distinguished by their large vertebral bodies and mammillary processes. The joint between the superior articular process of a vertebrae and the inferior articular process of the vertebrae directly above it is called a zygapophyseal joint. Articular processes emerge from the junctions of the pedicles and laminae.

ATLAS (C1)

AXIS (C2)

THORACIC VERTEBRA

CERVICAL VERTEBRA

35

LUMBAR VERTEBRA

SPINAL LIGAMENTS

Anterior and posterior longitudinal ligaments run along anterior and posterior surfaces of vertebral bodies respectively. (Posterior longitudinal ligament situated in vertebral foramen). Ligamenta flava connect adjacent laminae. Interspinous ligaments pass between adjacent spinous processes. Supraspinous ligament passes along tips of spinous processes from C7 to sacrum. Above C7, supraspinous ligament becomes the much thicker ligamentum nuchae.

AXIAL CROSS SECTION

Intervertebral discs lie between adjacent vertebral bodies. They consist of an outer, fibrocartilaginous anulus fibrosus, surrounding the inner, jelly-like nucleus pulposus. The disc nucleus acts as a shock absorber for the spine, and has a certain degree of movement in relation to its surrounding disc anulus.

SAGITTAL CROSS SECTION

SPINAL LIGAMENTS

36

STRUCTURES OF THE VERTEBRAL CANAL The spinal cord is part of the central nervous system situated in the superior two-thirds of the vertebral canal. It extends from the foramen magnum (an opening at the base of the skull) to between L1 & L2 (around L3 in newborn infants). The distal end is called the conus medullaris. The pial part of the filum terminae continues inferiorly from the apex of the conus medullaris, along with spinal nerves arranged in a bundle, collectively referred to as the cauda equina. The spinal cord has a cervical enlargement and a lumbosacral enlargement which correspond to spinal nerves C5 - T1 and L1 - S3 respectively. Anterior spinal artery & anterior spinal vein follow the course of the anterior median fissure. Posterior spinal arteries run along each posterolateral sulci. Posterior spinal vein runs along posterior median sulcus. Internal vertebral plexus of veins occurs in extradural space, surrounding the dura mater (which in turn wraps around the spinal cord / cauda equina). Dura mater extends to envelop spinal nerve roots, becoming the epineurium (outer covering) of these nerves. Within the spinal dura mater lies the arachnoid mater, a thin delicate membrane which ends at the level of S2. Pia mater is a membrane firmly attached to the surface of the spinal cord. It extends into the anterior median fissure and bilaterally outwards (denticulate ligaments).

CROSS SECTION

SPINAL CORD

37

Between the arachnoid mater and pia mater is the subarachnoid space, which contains cerebrospinal fluid (CSF). Spinal anaesthesia involves injection of a local anaesthetic into the CSF. The various maters are collectively referred to as meninges, a system of membranes enveloping the central nervous system.

There are 31 pairs of spinal nerves, formed from the merging of the dorsal and ventral roots which emerge from the spinal cord. The name of each spinal nerve corresponds to the vertebra above it, with the exception of spinal nerves C1 – C8 in the cervical region, which emerge above their respective vertebrae C1 – T1. It is also noteworthy that the coccygeal nerve is the only spinal nerve of the coccygeal region.

CROSS SECTION OF STRUCTURES WITHIN THE VERTEBRAL CANAL

MUSCULATURE OF THE BACK – EXTRINSIC MUSCLES

Extrinsic muscles of the back are comprised of: – SUPERFICIAL GROUP (Related to movements of the upper limb)

– INTERMEDIATE GROUP (Attached to ribs, serving a respiratory function)

ORIGIN INSERTION INNERVATION ACTION

TRAPEZIUS Ligamentum Nuchae; Spinous processes of C7-T12

Lateral third of clavicle; Acromion; Spine of scapula

Accessory nerve Rotates, elevates, adducts & depresses scapula

LATISSIMUS DORSI Spinous processes of T9-L5 & sacrum; Iliac Crest; Ribs 10-12

Floor of intertubercular groove of humerus

Thoracodorsal nerve Extends, adducts & medially (internally) rotates humerus

LEVATOR SCAPULAE Transverse processes of C1-C4 Upper medial border of scapula C3 & C4 anterior rami; Dorsal scapular nerve

Elevates scapula

RHOMBOID MAJOR Spinous processes of T2-T5 Lower medial border of scapula

Dorsal scapular nerve Retracts (adducts) & elevates scapula RHOMBOID MINOR Ligamentum nuchae ;

Spinous processes of C7 & T1 Medial border at spine of scapula

SERRATUS POSTERIOR SUPERIOR

Ligamentum nuchae; Spinous processes of C7-T3;

Supraspinous ligament Upper border of ribs 2-5 Anterior rami of upper

thoracic nerves (T2-T5) Elevates ribs 2 – 5

SERRATUS POSTERIOR INFERIOR

Spinous processes of T11-L3; Supraspinous ligament

Lower border of ribs 9-12 Anterior rami of lower thoracic nerves (T9-T12)

Depresses ribs 9 -12 & prevents elevation of lower ribs during diaphragm contraction

38

INTRINSIC MUSCLES

ORIGIN INSERTION INNERVATION ACTION

ERECTOR SPINAE MUSCLES

Spinous processes of lower thoracic vertebrae

Spinous / transverse processes of higher thoracic vertebrae

& cervical vertebrae

Posterior rami of spinal nerves

Extension, flexion & lateral flexion of vertebral column (and certain

movements of the head)

INTERMEDIATE GROUP OF

EXTRINSIC MUSCLES

SUPERFICIAL GROUP OF EXTRINSIC MUSCLES

Levator scapulae

Supraspinatus

Infraspinatus

Teres minor

Teres major

Rhomboid minor

Rhomboid major

External oblique

Latissimus dorsi

Deltoid

Trapezius Serratus posterior superior

Thoracolumbar fascia

Serratus posterior inferior

Erector spinae muscles are comprised of: iliocostalis (lateral column) ; longissimus (intermediate column) ; spinalis (medial column)

39

40

CLINICAL ANATOMY Studying anatomy from a clinical perspective involves a fundamental approach that considers both structure & function. An awareness of this cause & effect relationship enables the practical application of anatomical knowledge to clinical scenarios, and the essence of this is to be able to make the necessary association between the two. In this section, a number of important clinical manifestations and their commonly associated anatomical causes are listed. Rotator cuff: Either trauma or prolonged degeneration can cause irritation or damage to the tendons (or, in some cases, muscles) of the rotator cuff. Most commonly affected is the supraspinatus tendon, which passes inferolaterally to the acromion process and inserts onto the greater tubercle of the humerus. Rotator cuff tears or tendonitis can cause inflammation within the shoulder capsule, impairing the shoulder’s normal range of movement, with the gradual onset of pain and/or weakness. Radial nerve palsy: The most common cause is damage to the radial nerve as it passes through the radial groove on the posterior aspect of a fractured humeral shaft, between the medial and lateral heads of triceps brachii. This presents with wrist drop (inability to extend the muscles of the forearm & hand) and can cause sensory changes across the dorsal aspect of the hand. Median nerve palsy: Trauma to the upper limb or neuropathy can damage the median nerve. Depending upon the level of the injury, these are categorized into high and low median nerve palsies. Paralysis of the thenar muscles (innervated by the median nerve) causes an inability to oppose or abduct the thumb, referred to as ‘ape hand deformity’. Weakness in forearm pronation, wrist and finger flexion can also potentially manifest. Compression of the median nerve can occur at various levels, such as between the shaft of the humerus and its medial epicondyle (if Struthers' ligament has calcified), but by far the most common example is median nerve entrapment in carpal tunnel syndrome: Pressure upon the median nerve as it passes through the carpal tunnel causes pain and paraesthesia across the distribution. Atrophy of the thenar eminence and associated muscle weakness is also possible. Surgical decompression of the flexor retinaculum may be necessary to alleviate this condition. Ulnar nerve palsy: Compression or injury of the ulnar nerve as it passes posterior to the medial epicondyle of the humerus (either due to degenerative changes of the surrounding retinaculum or direct trauma) manifests as cubital tunnel syndrome, which presents with paraesthesia of the little finger and the medial aspect of the ring finger, and can be followed by weakness in the corresponding muscles of the hand. Entrapment of the ulnar nerve as it passes through the wrist is termed Guyon’s canal syndrome, resulting in sensory and/or motor impairment. In more severe cases of ulnar nerve lesions, an ulnar claw can develop, where hyperextension in the MCP joints and flexion in the proximal & distal IP joints of the 4th and 5th digits sets in.

Ulnar claw can be distinguished from the similar claw appearance of Dupuytren’s contracture (thickening &_ fibrosis of the palmar aponeurosis), in that the MCP joints are hyperextended in the former, but flexed in the latter.

41

Anatomical snuff box (radial fossa): The scaphoid and trapezium form the floor of the anatomical snuff box, located between the radial styloid process and the base of the thumb. The extensor pollicis longus tendon is the posterior border, whilst the anterior border comprises the extensor pollicis brevis and abductor pollicis longus tendons. The radial artery passes through the anatomical snuff box, and the wrist articulation between the radius and scaphoid tends to bear the brunt of force during a fall on an outstretched hand. A scaphoid fracture tends not to present with any significant wrist deformity, but rather swelling and tenderness, and must be diagnosed correctly since the proximal scaphoid is at risk of avascular necrosis. Long thoracic nerve: The long thoracic nerve is susceptible to injury, either due to trauma, (direct, stretching or compressive forces), neuritis, or iatrogenic damage – for instance, during breast surgery. Such damage results in paralysis of the serratus anterior, and presents with a winged scapula. Pain (often described as a burning sensation) can occur in the scapular region. Piriformis syndrome: In approximately 15% of the population, the sciatic nerve passes through piriformis, and thus can become compressed or irritated at this position. This condition presents with pain and paraesthesia radiating down the affected leg, called sciatica, which in turn can be caused by (and therefore should be distinguished from) an intervertebral disc herniation – most commonly occurring in the lumbar region, impinging upon the cauda equina. Gluteal intramuscular injections should be given on the upper, outer quadrant of the gluteal region in order to avoid injury to the sciatic nerve and resultant neuropathic complications. Knee ligaments & menisci: Since the anterior cruciate and medial (tibial) collateral ligaments are attached to the medial meniscus, an ACL or MCL tear (often due to sports injuries and direct knee trauma) can also damage the medial meniscus. Conversely, the lateral meniscus is less commonly injured as there is no attachment to the lateral collateral ligament or joint capsule. It is important to note that either meniscus can rupture alone, either due to trauma or age-related degeneration. Either the Lachman or drawer test can be used to examine the integrity of the cruciate ligaments; excessive anterior displacement of the tibia in relation to a stabilized femur is indicative of a torn ACL, whereas excessive posterior displacement suggests a PCL tear. Fibular (peroneal) nerve palsy: Traumatic injury involving abnormal forces applied to the knee or below, chronic compression (at the head of the fibula), or peripheral neuropathy can cause damage to the common (or deep) fibular nerve, which typically manifests as foot drop. The muscles in the anterior compartment of the leg are unable to dorsiflex the foot, causing it to drag during walking, with toes pointing downwards. In turn, this may be accompanied by sensory loss upon the dorsal surface of the foot and lateral aspect of the distal leg. Tarsal tunnel syndrome – tibial nerve entrapment: This is a compression neuropathy where compression of the tibial nerve by the flexor retinaculum posterior to the medial malleolus causes paraesthesia across the heel and plantar aspect of the foot, radiating to the hallux (big toe) and adjacent two digits.

42

CROSS-SECTIONAL ANATOMY – EXAMINATION TIPS Before identifying any individual structures on a cross-section, it is important to orientate oneself and recognize which part of the body is being observed. Under the time constraints of a spotter examination or viva, a structured strategy, such as follows, can be beneficial:

ARM: Find neurovascular bundle, comprising brachial artery & veins, median nerve, ulnar nerve and basilic vein – MEDIAL ASPECT Find remaining prominent superficial vein (Cephalic vein) – ANTEROLATERAL

FOREARM: Ulna (POSTEROMEDIAL) is more subcutaneous and triangular in cross-section

than radius (LATERAL). Basilic & cephalic veins similarly positioned as in arm. Flexors positioned anteriorly to bones (and their connecting interosseous membrane); extensors positioned posteriorly & laterally.

THIGH: Find prominent superficial vein (Great saphenous vein) – MEDIAL ASPECT

Find largest, most prominent nerve (Sciatic nerve) – POSTERIOR ASPECT Rectus femoris most anteriorly positioned muscle in thigh. Vastus muscles surround femur. Hamstrings immediately posterior to sciatic nerve.

LEG: Find prominent superficial vein (Great saphenous vein) – MEDIAL ASPECT

Subcutaneous surface of tibia – ANTEROMEDIAL Interosseous membrane connects tibia to much smaller (& more posterolaterally positioned) fibula; separates tibialis anterior & posterior muscles. Small saphenous vein positioned posteriorly.

How many bones?

Arm / Thigh Forearm / Leg

1 2

?

Are the bones (a) similar in size or (b) is one considerably larger than the other with a subcutaneous border?

a b

Forearm Leg

?

The thigh has a much greater muscle mass (comprising 3 compartments)

than the arm (which has only 2 muscle compartments). The humerus

is almost circular in cross-section; the femur is slightly more triangular.