Introduction to the upper limb, back, thorax, and abdomen

Overview and topographic anatomy

General information

Upper limb

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The upper limb is the region of the body composed of the:
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  Pectoral girdle
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  Brachium (arm)
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  Antebrachium (forearm)
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  Carpus, metacarpus, phalanges (wrist and hand)
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It is a very mobile structure that allows manipulation of objects
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All motor and sensory innervation is derived from the brachial plexus, which arises from the ventral rami of C5 to T1
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It is a frequent site of traumatic injury

Back and thorax

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The thoracic cavity is divided into:
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  2 pleural cavities
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  Mediastinum

Anterolateral abdominal wall

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Layers of the anterolateral abdominal wall:
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  Skin
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  Superficial fascia
  - •
    Fatty superficial layer (Camper’s)
  - •
    Membranous superficial layer (Scarpa’s)
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  External oblique
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  Internal oblique
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  Transversus abdominis
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  Transversalis fascia
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  Extraperitoneal fat
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  Parietal peritoneum

Abdomen

•
Part of the trunk that lies between the thorax and the pelvis, containing:
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  Peritoneal cavity
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  Gastrointestinal (GI) organs
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  Liver and biliary system
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  Adrenal glands
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  Pancreas
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  Kidneys and upper part of ureters
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  Nerves and blood vessels
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Divided into body planes:
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  Xiphisternal—T9
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  Transpyloric—L1
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  Subcostal—L3
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  Supracristal—L4
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  Transtubercular—L5
- •
  Interspinous—S2

Osteology

Upper limb

BONES OF THE PECTORAL GIRDLE

Clavicle

▪
Is convex anteriorly at the sternal end (medial 2/3) and concave anteriorly at the acromial end (lateral 1/3)
▪
Provides for the attachment of 4 muscles:
- ▪
  Pectoralis major
- ▪
  Deltoid
- ▪
  Trapezius
- ▪
  Sternocleidomastoid
▪
Transmits force from the upper limb to the axial skeleton
▪
Is paired
▪
Is frequently fractured

Scapula

▪
Is flat and triangular in shape
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Is paired
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Has numerous landmarks/components:
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  Costal surface—provides attachment for subscapularis
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  Spine—provides attachment for trapezius and deltoid
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  Acromion—provides attachment for trapezius and deltoid and articulates with clavicle
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  Glenoid cavity—articulates with the head of the humerus
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  Supraglenoid tubercle—provides attachment for the long head of the biceps brachii
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  Infraglenoid tubercle—provides attachment for the long head of the triceps brachii
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  Scapular notch—is crossed superiorly by the transverse scapular ligament; suprascapular n. passes inferior to ligament and suprascapular vv. pass superior to ligament
- ▪
  Coracoid process—provides attachment for pectoralis minor, short head of biceps brachii, and coracobrachialis

BONES OF THE UPPER LIMB

Humerus

▪
Articulates with the scapula, ulna, and radius
▪
Longest bone of the upper limb
▪
Has 8 centers of ossification
▪
Has 16 major landmarks/components:
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  Head—smooth surface that articulates with the glenoid cavity of the scapula
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  Anatomic neck—oblique passing groove that provides attachment for the articular capsule
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  Greater tubercle—provides attachment for 3 rotator cuff muscles: supraspinatus, infraspinatus, and teres minor
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  Lesser tubercle—provides attachment for 1 rotator cuff muscle: subscapularis
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  Intertubercular groove—between greater and lesser tubercles; long head of the biceps brachii located in groove
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  Surgical neck—axillary nerve and posterior humeral circumflex a. and v. lie in contact with medial portion of surgical neck
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  Radial groove—posterior surface of humerus where radial n. and profunda brachii a. and v. are located
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  Deltoid tuberosity—provides attachment of deltoid
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  Capitulum—rounded distal end of the lateral humerus that provides articulation with the radius (head)
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  Trochlea—pulley-shaped distal end of the medial humerus that provides articulation with the ulna (trochlear notch)
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  Olecranon fossa—depression on posterior humerus superior to trochlea; provides area for olecranon process of ulna to occupy during extension of antebrachium
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  Coronoid fossa—depression on anterior humerus superior to trochlea that provides area for coronoid process to occupy during flexion of antebrachium
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  Radial fossa—depression on anterior humerus superior to capitulum that provides area for radius (head) during flexion of antebrachium
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  Supracondylar ridges—sharp elevations of bone on lateral portion of distal humerus that provides attachment of brachial fascia
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  Medial epicondyle—elevation at distal part of medial supracondylar ridge; ulnar n. and superior ulnar collateral a. and v. are located posterior
- ▪
  Lateral epicondyle—elevation at distal part of lateral supracondylar ridge

Radius

▪
Articulates with capitulum of humerus and the radial notch of the ulna proximally
▪
Articulates with scaphoid and lunate carpal bones and the ulna at the ulnar notch distally
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Is shorter than ulna
▪
Is frequently fractured at distal end (Colles’ fracture)
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Has 5 major anatomic components/landmarks:
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  Head—proximal end of radius; provides articulation with capitulum of humerus
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  Radial tuberosity—provides attachment for biceps brachii
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  Styloid process—provides attachment for brachioradialis near the base of this process
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  Ulnar notch—distal articulation with ulna
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  Dorsal (Lister’s) tubercle—dorsal bony protuberance at the distal end that acts as a pulley for the extensor pollicis longus tendon

Ulna

▪
Articulates with trochlea of humerus and radius proximally and radius distally
▪
Has 6 major anatomic structures:
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  Olecranon—proximal portion of ulna; provides attachment for triceps brachii
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  Coronoid process—provides attachment for brachialis
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  Trochlear notch—depression for articulation with trochlea of humerus
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  Radial notch—depressed area for radius (head)
- ▪
  Head—distal portion of ulna
- ▪
  Styloid process—projects posterior and medial

BONES OF THE CARPUS, METACARPUS, AND PHALANGES

▪
The wrist (carpus) comprises 2 rows of small bones:
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  Proximal row (lateral to medial):
  - ▪
    Scaphoid—commonly fractured
  - ▪
    Lunate
  - ▪
    Triquetrum
  - ▪
    Pisiform
- ▪
  Distal row (lateral to medial):
  - ▪
    Trapezium
  - ▪
    Trapezoid
  - ▪
    Capitate
  - ▪
    Hamate
▪
There are 5 metacarpal bones that articulate with the distal row of carpal bones
▪
There are 14 phalanges
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  Fingers 2–5 have a total of 3 phalanges per digit (1 proximal, 1 middle, 1 distal)
- ▪
  Finger 1 (thumb) has a total of 2 phalanges (1 proximal and 1 distal)

Back

BONES OF BACK
Overview
▪ Vertebral column includes 33 vertebrae: ▪ 7 cervical ▪ 12 thoracic ▪ 5 lumbar ▪ 5 sacral—fuse to form sacrum ▪ 4 coccygeal—fuse to form coccyx ▪ Functions include: ▪ Central axis of body weight support ▪ Enables upright positioning ▪ Allows mobility ▪ Protection of spinal cord and spinal roots ▪ Important vertebral levels: ▪ T2—suprasternal notch ▪ T3—spine of scapula ▪ T7—inferior angle of the scapula ▪ T9—xiphoid process ▪ L1—transpyloric plane ▪ L3—subcostal plane ▪ L4—supracristal plane ▪ L5—transtubercular plane ▪ S2—interspinous plane
Parts of the Typical Vertebra
▪ Body ▪ Vertebral arch ▪ Pedicles ▪ Superior and inferior articulating facets (the “pars interarticularis” is the area that lies between the facets) ▪ Transverse process ▪ Lamina ▪ Spinous process ▪ Superior and inferior vertebral notches ▪ Intervertebral foramen
Types of Vertebra	Characteristics
Cervical	7 in number (C1–C7) C1 is the atlas (has no body or spinous process) C2 is the axis (has dens) C3–C6 have small bodies and spinous processes C7 has long spinous process
Thoracic	12 in number (T1–T12) Costal facets on body and transverse process Long spinous processes Heart-shaped body
Lumbar	5 in number (L1–L5) Thick body No costal facets
Sacral	5 in number (S1–S5) Fused to form sacrum 4 pairs of sacral foramina Sacral hiatus
Coccygeal	3–5 in number (typically 4) Fused to form coccyx Mainly provides muscle and ligament attachment

Thorax

BONES OF THORAX
Overview
▪ Landmarks include: ▪ Midclavicular line—vertical line passing through the midpoint of the clavicle ▪ Midaxillary line—vertical line passing through the midpoint of the axilla ▪ Scapular line—vertical line passing through the inferior angle of scapula ▪ Suprasternal notch—T2 ▪ Sternal angle—T4 ▪ The thoracic apertures: ▪ Superior thoracic aperture ▪ Boundaries ▪ Body of T1 vertebra ▪ 1st pair of ribs and cartilages ▪ Manubrium (superior portion) ▪ Major contents ▪ Trachea ▪ Esophagus ▪ Great vessels and nerves ▪ Thoracic duct ▪ Lungs ▪ Inferior thoracic aperture ▪ Boundaries ▪ Body of T12 vertebra ▪ 12th pair of ribs ▪ Costal margins ▪ Xiphoid process
Sternum
Parts	Characteristics
Manubrium	Superior part of sternum Quadrangular in shape Superior border is known as jugular notch or suprasternal notch (vertebral level T2) Articulates with: ▪ Clavicle ▪ 1st costal cartilage ▪ 2nd costal cartilage ▪ Body of sternum
Body	Longest part of sternum Articulates with 2nd–7th ribs Articulates with: ▪ Manubrium at manubriosternal joint (vertebral level T4) ▪ Xiphoid process (vertebral level T9)
Xiphoid process	Cartilaginous process, which ossifies
Ribs
Type	Characteristics
Vertebrosternal	Ribs 1–7 Known as “true ribs” because they articulate with the sternum through the costal cartilage Articulate with the sternum through the costal cartilage
Vertebrochondral	Ribs 8–10 Known as “false ribs” because they do not possess a direct articulation to the sternum These ribs articulate to a common cartilaginous connection to the sternum
Vertebral	Ribs 11 and 12 Most commonly known as “floating ribs” They also are “false ribs” because they do not possess a direct articulation to the sternum Do not articulate with the sternum and end in the posterior abdominal wall

Abdomen

BONES OF ABDOMEN AND PELVIS
Overview
▪ The 5 lumbar vertebrae are in the abdomen region ▪ Bones of the pelvis comprise 3 structures: ▪ Sacrum ▪ Coccyx ▪ Os coxae (hip bone) ▪ Ilium ▪ Ischium ▪ Pubis ▪ The pelvis is the inferior portion of abdomen providing a connection of the spinal column to the femurs ▪ Multiple functions: ▪ Bear weight (transmission of weight from lower limbs to spine) ▪ Allow locomotion ▪ Maintain upright posture ▪ Support and protection of pelvic organs ▪ Provide for muscle and ligament attachment ▪ Has a pelvic cavity that is divided by the pelvic brim into: ▪ False pelvis—superior to pelvic brim and contains inferior portion of abdominal cavity ▪ True pelvis—inferior to pelvic brim and contains the: ▪ Bladder ▪ Terminal colon and rectum ▪ Some reproductive and accessory reproductive organs: ▪ Prostate ▪ Seminal vesicles ▪ Vas deferens ▪ Uterus with uterine tubes and ovary ▪ Vagina
Os Coxae (Pelvis)
Part	Characteristics
Ilium	Largest part of the pelvis Comprises the: ▪ Ala (wing) ▪ Body Provides muscle and ligament attachments
Ischium	Most posterior and inferior portion of the pelvis Comprises the: ▪ Body ▪ Superior ischial ramus ▪ Inferior ischial ramus Provides muscle and ligament attachments
Pubis	Most anterior portion of the pelvis Comprises the: ▪ Superior pubic ramus ▪ Inferior pubic ramus Provides muscle and ligament attachments Right and left pelvic bones articulate at the pubic symphysis

Muscles

Upper limb

MUSCLES OF PECTORAL REGION
Muscle	Origin	Insertion	Action(s)	Nerve Supply
Pectoralis major	Clavicular head ▪ Clavicle (medial 1/2) Sternocostal head ▪ Anterior surface of sternum ▪ Upper 6 costal cartilages	Lateral lip of intertubercular groove	Flexion of humerus Adduction of humerus Medial rotation of humerus	Medial pectoral n. Lateral pectoral n.
Pectoralis minor	Ribs 3–5	Coracoid process	Protraction/anterior tilt of scapula Aids in stabilization of scapula	Medial pectoral n.
Serratus anterior	Ribs 1–8	Medial border of scapula	Protraction of scapula Rotates the scapula Aids in stabilization of the scapula	Long thoracic n.
Subclavius	1st rib and 1st costal cartilage	Inferior surface of clavicle	Clavicular stabilization during upper limb movement or aids elevation of first rib	Subclavius n.

MUSCLES OF SHOULDER
Muscle	Origin	Insertion	Actions	Nerve Supply
Deltoid	▪ Lateral 1/3 of clavicle ▪ Acromion ▪ Spine of scapula	Deltoid tuberosity	Elevation of humerus Anterior fibers aid in flexion of humerus and medial rotation of humerus Middle fibers aid in abduction of humerus Posterior fibers aid in extension of humerus and lateral rotation of humerus	Axillary n.
Teres major	Inferior angle of posterior scapula	Medial lip of intertubercular groove	Adduction of humerus Medial rotation of humerus	Lower subscapular n.
Supraspinatus	Supraspinous fossa	Greater tubercle (superior facet)	Abduction of humerus (1st 10–15 degrees) Aids in holding humerus in glenoid cavity	Suprascapular n.
Infraspinatus	Infraspinous fossa	Greater tubercle (middle facet)	Lateral rotation of humerus Aids in holding humerus in glenoid cavity Aids in adduction	Suprascapular n.
Teres minor	Lateral border of scapula	Greater tubercle (inferior facet)	Lateral rotation of humerus Aids in holding humerus in glenoid cavity Aids in adduction	Axillary n.
Subscapularis	Subscapular fossa	Lesser tubercle	Medial rotation of humerus Aids in holding humerus in glenoid cavity Aids in adduction	Upper subscapular n. Lower subscapular n.

MUSCLES OF BRACHIUM
Flexor Compartment
Muscle	Origin	Insertion	Action(s)	Nerve Supply
Biceps brachii	Long head ▪ Supraglenoid tubercle Short head ▪ Coracoid process	Radial tuberosity of radius	Flexion of antebrachium Supination of antebrachium Aids in flexion of brachium	Musculocutaneous n.
Brachialis	Anterior surface of distal portion of humerus	▪ Coronoid process of ulna ▪ Ulnar tuberosity	Flexion of antebrachium	Musculocutaneous n.
Coracobrachialis	Coracoid process	Middle 1/3 of medial humerus	Flexion of brachium Adduction of brachium	Musculocutaneous n.
Extensor Compartment
Triceps brachii	Long head ▪ Infraglenoid tubercle Lateral head ▪ Superior to radial groove Medial head Inferior to radial groove	Olecranon of ulna	Extension of antebrachium Long head aids in slight adduction of brachium	Radial n.
Anconeus	Lateral epicondyle of humerus	Olecranon of ulna	Extension of antebrachium	Radial n.

MUSCLES OF FLEXOR SURFACE OF ANTEBRACHIUM
Superficial Group
Muscle	Origin	Insertion	Action(s)	Nerve Supply
Pronator teres	Medial epicondyle of humerus Coronoid process of ulna	Lateral surface of radius (middle portion)	Pronation of antebrachium Weak flexion of antebrachium	Median n.
Flexor carpi radialis	Medial epicondyle of humerus	Base of 2nd and 3rd metacarpal	Weak flexion of antebrachium Flexion of wrist Abduction (radial deviation) of wrist	Median n.
Palmaris longus	Medial epicondyle of humerus	Palmar aponeurosis	Weak flexion of antebrachium Flexion of wrist	Median n.
Flexor carpi ulnaris	Medial epicondyle of humerus Posterior ulna	Pisiform Hamate (hook) Base of 5th metacarpal	Weak flexion of antebrachium Flexion of wrist Adduction (ulnar deviation) of wrist	Ulnar n.
Intermediate Group
Flexor digitorum superficialis	Medial epicondyle of humerus Coronoid process Radius (oblique line)	Middle phalanges of digits 2–5	Weak flexion of antebrachium Flexion of hand Flexion of proximal interphalangeal joints of digits 2–5	Median n.
Deep Group
Flexor digitorum profundus	Anterior and medial surface of ulna Interosseous membrane	Base of distal phalanges of digits 2–5	Flexion of hand Flexion of distal interphalangeal joints of digits 2–5	Anterior interosseous of the median n. (lateral 1/2) Ulnar n. (medial 1/2)
Flexor pollicis longus	Anterior surface of radius Interosseous membrane	Base of distal phalanx of thumb	Flexion of thumb	Anterior interosseous of the median n.
Pronator quadratus	Anterior surface of distal ulna	Anterior surface of distal radius	Pronation of antebrachium	Anterior interosseous of the median n.

MUSCLES OF EXTENSOR SURFACE OF ANTEBRACHIUM
Muscle	Origin	Insertion	Action(s)	Nerve Supply
Brachioradialis	Lateral supracondylar ridge of humerus	Styloid process of distal radius	Flexion of antebrachium	Radial n.
Extensor carpi radialis longus	Lateral epicondyle of humerus	Base of 2nd metacarpal	Extension of wrist Abduction (radial deviation) of wrist Weakly aids in flexion of forearm	Radial n.
Extensor carpi radialis brevis		Base of 3rd metacarpal	Extension of wrist Abduction of wrist Weakly aids in flexion of forearm	Deep radial n.
Extensor digitorum		Joins extensor expansion of digits 2–5	Extension of wrist Extension of digits 2–5	Posterior interosseous n. from the radial n.
Extensor digiti minimi		Joins extensor expansion of the extensor digitorum tendon of proximal phalanx 5th digit	Extension of 5th digit (little finger)	Posterior interosseous n. from the radial n.
Extensor carpi ulnaris	Lateral epicondyle of humerus Posterior ulna	Base of 5th metacarpal	Extension of wrist Adduction (ulnar deviation) of wrist	Posterior interosseous n. from the radial n.
Supinator	Lateral epicondyle of humerus Ulna	Radial tubercle Oblique line of radius	Supination	Deep radial n.
Extensor indicis	Posterior ulna Interosseous membrane	Joins extensor expansion of the extensor digitorum of index finger (2nd digit)	Extension of index finger (2nd digit)	Posterior interosseous n. from the radial n.
Abductor pollicis longus	Lateral posterior ulna Interosseous membrane Posterior radius	Base of 1st metacarpal (lateral side)	Abducts 1st digit Abducts wrist	Posterior interosseous n. from the radial n.
Extensor pollicis longus	Posterior ulna Interosseous membrane	Base of distal phalanx of 1st digit	Extension of distal phalanx of 1st digit Helps extend and abduct wrist	Posterior interosseous n. from the radial n.
Extensor pollicis brevis	Posterior ulna Interosseous membrane Posterior radius	Base of proximal phalanx of 1st digit	Extend and abduct 1st digit	Posterior interosseous n. from the radial n.

MUSCLES OF THE HAND
Muscle(s)	Origin	Insertion	Action(s)	Nerve Supply
Abductor pollicis brevis	Flexor retinaculum Tubercle of scaphoid Tubercle of trapezium	Base of proximal phalanx of thumb (radial side)	Abduction of thumb Aids in opposition of thumb Aids in extension of thumb	Recurrent branch of median n.
Opponens pollicis	Flexor retinaculumTubercle of trapezium	1st metacarpal (radial side)	Opposition of thumb
Flexor pollicis brevis	Flexor retinaculumTubercle of trapezium	Base of proximal phalanx of thumb (radial side)	Flexion of thumb at metacarpophalangeal joint
Abductor digiti minimi	Flexor retinaculumPisiform	Base of proximal phalanx of 5th digit	Abduction of 5th digit (little finger)	Deep branch of ulnar n.
Opponens digiti minimi	Flexor retinaculum Hamulus of hamate	Shaft of 5th metacarpal	Flexion of 5th metacarpal Laterally rotate 5th metacarpal
Flexor digiti minimi brevis	Flexor retinaculum Hamulus of hamate	Base of proximal phalanx of 5th digit	Flexion of metacarpophalangeal joint of 5th digit
Palmaris brevis	Flexor retinaculum Palmar aponeurosis	Skin of palm	Raises hypothenar eminence	Superficial branch of ulnar n.
Adductor pollicis ▪ Oblique head ▪ Transverse head	▪ Capitate, 2nd and 3rd metacarpals ▪ Shaft of 3rd metacarpal	Base of proximal phalanx of thumb	Adduction of thumb	Deep branch of ulnar n.
Lumbrical ▪ 1st and 2nd are unipennate 3rd and 4th are bipennate	1st and 2nd —radial side of flexor digitorum profundus tendons of middle index and fingers 3rd —side of flexor digitorum profundus tendons of middle and ring fingers 4th —side of flexor digitorum profundus tendons of ring and little fingers	Extensor expansion	Flexion of proximal phalanx Extension of middle and distal phalanges	▪ Median n. for 1st and 2nd lumbricals ▪ Deep branch of ulnar n. for 3rd and 4th lumbricals
Dorsal interosseous (bipennate)	1st —radial side of 2nd metacarpal; ulnar side of 1st metacarpal 2nd —radial side of 3rd metacarpal; ulnar side of 2nd metacarpal 3rd —radial side of 4th metacarpal; ulnar side of 3rd metacarpal 4th —radial side of 5th metacarpal; ulnar side of 4th metacarpal	1st —radial side of 2nd proximal phalanx; extensor expansion 2nd —radial side of 3rd proximal phalanx; extensor expansion 3rd —ulnar side of 3rd proximal phalanx; expansion extensor 4th —ulnar side of 4th proximal phalanx; extensor expansion	Abduction of fingers from the middle finger Aid in flexion of metacarpophalangeal joint Aid in extension of interphalangeal joints	Deep branch of ulnar n.
Palmar interosseous (unipennate)	1st —ulnar side of 2nd metacarpal 2nd —radial side of 4th metacarpal 3rd —radial side of 5th metacarpal	1st —ulnar side of proximal phalanx of 2nd digit 2nd —radial side of proximal phalanx of 4th digit 3rd —radial side of proximal phalanx of 5th digit	Adduction of fingers toward the middle finger Aid in flexion of metacarpophalangeal joint Aid in extension of interphalangeal joints	Deep branch of ulnar n.

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Feb 15, 2025 | Posted by drzezo in General Dentistry | Comments Off

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Introduction to the upper limb, back, thorax, and abdomen

Overview and topographic anatomy

General information

Upper limb

Back and thorax

Anterolateral abdominal wall

Abdomen

Osteology

Upper limb

Back

Thorax

Abdomen

Muscles

Upper limb

Related

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Pocket Dentistry

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Introduction to the upper limb, back, thorax, and abdomen

Overview and topographic anatomy

General information

Upper limb

Back and thorax

Anterolateral abdominal wall

Abdomen

Osteology

Upper limb

Back

Thorax

Abdomen

Muscles

Upper limb

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