Introduction

This study guide summarizes the anatomical basis of human movement, focusing on the myology (study of muscles) of the forearm and hand. It is based on lecture notes for ANAT1005, covering muscle groups, compartments, bone and joint structure, and key terminology relevant to the upper limb.

Etymology: Useful Word Roots for Key Terms

Understanding Anatomical Terminology

Many anatomical terms are derived from Latin or Greek roots that describe location, shape, or function. Recognizing these roots aids in understanding muscle names and their actions.

• Location Features:

  • Epaxial: upon, over, beside

  • Knuckle: tubercle (small, rounded projection)

  • Digit: finger or toe

  • Dorsal: back of body or body part

  • Palmar: palm of hand

  • Pollicis: thumb

• Muscle Shape/Appearance:

  • Teres: round

  • Quadratus: square, rectangular

  • Lumbrical: wormlike

• Function/Action:

  • Flexor/Extensor: bends/extends a joint

  • Adductor/Abductor: moves a limb toward/away from the midline

  • Pronator/Supinator: rotates the forearm

  • Longus/Brevis: long/short

• Other Key Terms:

  • Interosseous: between bones

  • Retinaculum: a band holding tendons in place

Learning Objectives

Muscle Compartments and Groups

Muscles of the upper limb are organized into compartments, each with a common function and attachment points. Understanding these compartments is essential for identifying muscle actions and locations.

• Compartment Identification: Know the location of compartments/groups on the skeleton and on yourself.

• Function: Understand the main function/action of muscles within a compartment.

• Attachment Points: Recognize important common attachment points for each group.

Individual Muscles

Be able to identify and name each muscle, its compartment, and its main function/action. Muscle function can often be deduced from the alignment of the muscle belly and tendons relative to the joints they cross.

Overview of Topics

• Regions & Compartments

• Extrinsic vs Intrinsic Hand Muscles

• Muscles of the Forearm

  • Anterior: FLEXOR Compartment (8 muscles)

  • Posterior: EXTENSOR Compartment (13 muscles)

• Intrinsic Muscles of the Hand

  • Three groups: thenar, hypothenar, midpalmar

Revision: Bones & Joints of the Upper Limb

Osteology of the Upper Limb

The upper limb consists of several key bones and joints that provide structure and facilitate movement.

• Pectoral Girdle:

  • Scapula

  • Clavicle

• Arm:

  • Humerus

• Forearm:

  • Ulna

  • Radius

• Wrist:

  • Carpal bones

• Hand:

  • Metacarpals

  • Phalanges

Major Joints of the Upper Limb

• Sternoclavicular Joint: Synovial, modified hinge (ball and socket/saddle properties)

• Acromioclavicular Joint: Synovial, gliding

• Glenohumeral Joint: Synovial, ball and socket

• Elbow and Forearm Joints:

  • Humeroulnar (and radial): Synovial, hinge

  • Proximal radioulnar: Synovial, pivot

  • Distal radioulnar: Synovial, pivot/hinge

• Wrist and Hand Joints:

  • Carpometacarpal, metacarpophalangeal, interphalangeal

Regions & Compartments of the Upper Limb

Compartmentalization

Muscles are grouped into compartments separated by connective tissue (fascia, intermuscular septa, interosseous membrane). Each compartment contains muscles with similar functions and innervation.

• Shoulder/Pectoral Muscles: Includes rotator cuff (deepest group)

• Arm Compartments:

  • Anterior (flexor)

  • Posterior (extensor)

• Forearm Compartments:

  • Anterior (flexor/anteromedial)

  • Posterior (extensor/posterolateral)

• Hand Compartments:

  • Intrinsic hand muscles: thenar, hypothenar, midpalmar

Extrinsic vs Intrinsic Hand Muscles

Definitions and Functional Differences

• Extrinsic Hand Muscles:

  • Located in the forearm; muscle bellies are proximal, tendons extend into the hand

  • Responsible for gross movements of the hand and fingers

• Intrinsic Hand Muscles:

  • Located entirely within the hand

  • Responsible for fine motor control and precision movements

Muscles of the Forearm

Anterior (Flexor) Compartment

The anterior compartment contains muscles that flex the wrist and fingers, and pronate the forearm.

• Superficial Layer (4 muscles):

  • Flexor carpi radialis

  • Flexor carpi ulnaris

  • Palmaris longus

  • Pronator teres

• Intermediate Layer (1 muscle):

  • Flexor digitorum superficialis

• Deep Layer (3 muscles):

  • Flexor digitorum profundus

  • Flexor pollicis longus

  • Pronator quadratus

Posterior (Extensor) Compartment

The posterior compartment contains muscles that extend the wrist and fingers, and supinate the forearm.

• Superficial Layer (7 muscles):

  • Brachioradialis

  • Extensor carpi ulnaris

  • Extensor carpi radialis longus

  • Extensor carpi radialis brevis

  • Extensor digitorum

  • Extensor digiti minimi

  • Anconeus (often ignored)

• Deep Layer (6 muscles):

  • Supinator

  • Extensor indicis

  • Abductor pollicis longus

  • Extensor pollicis brevis

  • Extensor pollicis longus

Intrinsic Muscles of the Hand

Three Groups

• Thenar Group: Muscles at the base of the thumb; responsible for thumb movement

• Hypothenar Group: Muscles at the base of the little finger; responsible for little finger movement

• Midpalmar Group: Muscles in the central palm; responsible for fine movements of digits 2-5

Key Structures: Retinacula and Carpal Tunnel

Retinacula

• Flexor Retinaculum: Forms the roof of the carpal tunnel; holds flexor tendons in place

• Extensor Retinaculum: Holds extensor tendons in place; includes intertendinous connections and extensor hoods

Carpal Tunnel

• Boundaries:

  • Medial wall: pisiform, hamate

  • Lateral wall: scaphoid, trapezium

  • Floor: carpal bones

  • Roof: flexor retinaculum

• Clinical Note: Inflammation/swelling can restrict tendons, leading to carpal tunnel syndrome

Forearm Muscle Naming Patterns

Logic and Patterns

• Muscles named for their action (flexor/extensor), location (carpi, digitorum, pollicis), and length (longus/brevis)

• "Dedicated" wrist muscles cross the wrist and act primarily on it

Summary Table: Dedicated Wrist Muscles

The following table summarizes the main dedicated wrist muscles, their insertions, and actions:

Forearm Movements: Pronation and Supination

Definitions

• Pronation: Rotation of the forearm so the palm faces downward

• Supination: Rotation of the forearm so the palm faces upward

Primary Muscles Involved

• Pronators:

  • Pronator teres

  • Pronator quadratus

• Supinators:

  • Supinator

  • Biceps brachii (arm muscle, most important for supination)

Key Equations and Concepts

Muscle Force and Joint Movement

• Torque at a Joint: where is torque, is force, and is the moment arm (distance from joint axis to line of force).

References

• Marieb et al. (2020) Human Anatomy and Physiology

• Gray's Anatomy

• Atlas of the Human Body

• Clinically Oriented Anatomy

Additional info: Some details on muscle origins, insertions, and clinical notes were inferred from standard anatomical knowledge and referenced textbooks.