lower muscles
Muscles that Position the Pectoral Girdle
Location of Muscles
Anterior Thorax Muscles:
Subclavius
Pectoralis Minor
Serratus Anterior
Posterior Thorax Muscles:
Trapezius
Rhomboid Major
Rhomboid Minor
Functionality of Muscles
Rhomboids Contraction:
Moves scapula medially
Involves pulling shoulder and upper limb posteriorly
Muscle Table
Anterior thorax:
Movement: Rotates shoulder anteriorly; assists with inhalation
Target motion direction: Scapula depresses, ribs elevate
Prime mover: Pectoralis Minor
Origin: Anterior surfaces of certain ribs (2–4 or 3–5)
Insertion: Coracoid process of scapula
Anterior thorax:
Movement: Moves arm from side of body to front of body; assists with inhalation
Target motion direction: Scapula protracts, ribs elevate
Prime mover: Serratus Anterior
Origin: Ribs (1–8 or 1–9)
Insertion: Scapula
Posterior thorax:
Movement: Elevates shoulders (shrugging); pulls shoulder blades together; tilts head backward
Target motion direction: Scapula rotates inferiorly, retracts, elevates and depresses; spine extends
Prime mover: Trapezius
Origin: Skull; vertebral column
Insertion: Acromion and spine of scapula
Posterior thorax:
Movement: Stabilizes scapula during pectoral girdle movement
Target motion direction: Retracts, rotates inferiorly
Prime mover: Rhomboid Major
Origin: Thoracic vertebrae (T2–T5)
Insertion: Medial border of scapula
Posterior thorax:
Movement: Stabilizes scapula during pectoral girdle movement
Target motion direction: Retracts, rotates inferiorly
Prime mover: Rhomboid Minor
Origin: Cervical and thoracic vertebrae (C7 and T1)
Insertion: Medial border of scapula
Muscles of the Humerus and Rotator Cuff
Composition:
Muscles crossing the shoulder joint and moving the humerus include both axial and scapular muscles.
Axial Muscles: Pectoralis Major, Latissimus Dorsi
Pectoralis Major: Thick and fan-shaped, covering much of the superior portion of the anterior thorax.
Latissimus Dorsi: Broad and triangular, located at the inferior back; inserts into a thick connective tissue sheath called an aponeurosis.
Muscles of the Forearm
Flexors of the Forearm:
Biceps Brachii:
- Two-headed muscle, crosses shoulder and elbow joints.
Function: Flexes the forearm and aids in supination at radioulnar joints.
Brachialis:
Located deep to biceps brachii.
Function: Provides additional power for flexing the forearm.
Brachioradialis:
Function: Flexes forearm quickly or aids in lifting a load slowly.
Anatomic Context:
These muscles, nerves, and blood vessels comprise the anterior compartment of the arm, known as the anterior flexor compartment of the arm.
Muscles of the Wrist and Hand
Anterior Compartment Superficial Muscles:
Flexor Carpi Radialis
Palmaris Longus
Flexor Carpi Ulnaris
Flexor Digitorum Superficialis
Function: Flexes hand and digits at knuckles,
allows rapid finger movement such as typing or playing musical instruments.
Posterior Compartment Superficial Muscles:
Extensor Radialis Longus
Extensor Carpi Radialis Brevis
Extensor Digitorum
Extensor Digiti Minimi
Extensor Carpi Ulnaris
Muscle Movements Table:
Biceps Brachii:
Target: Flexion; Supination
Target Motion Direction: Palm raises toward body while flexing
Origin: Coracoid process; tubercle above the glenoid cavity
Insertion: Radial tuberosity
Brachialis:
Target: Assists and stabilizes elbow during bicep-curl motion
Origin: Front of distal humerus
Insertion: Coronoid process of ulna
Brachioradialis:
Target: Flexion
Target Motion Direction: Forearm flexion
Origin: Lateral supracondylar ridge at distal end of humerus
Insertion: Base of styloid process of radius
Muscles of the Lower Jaw
Chewing Mechanism: Chewing termed as mastication.
Muscles involved:
Masseter: Main muscle for chewing, elevates the mandible to close mouth.
Temporalis: Assists in retracting the mandible.
Feel/Location: To feel the temporalis, press at the temple while chewing.
Muscle Movements Table:
Masseter:
Target: Closes mouth; aids chewing
Target Motion Direction: Superior (elevates)
Origin: Maxilla arch; zygomatic arch
Insertion: Mandible
Temporalis:
Target: Closes mouth; pulls lower jaw in
Target Motion Direction: Superior (elevates); posterior (retracts)
Origin: Temporal bone
Insertion: Mandible
Lateral Pterygoid:
Target: Opens mouth; pushes lower jaw out
Target Motion Direction: Inferior (depresses); posterior (protracts); lateral (abducts); medial (adducts)
Origin: Pterygoid process of sphenoid bone
Insertion: Mandible
Muscles of the Abdomen
Group Division: Four pairs of abdominal muscles covering the anterior and lateral regions:
External Obliques
Internal Obliques
Transversus Abdominis
Rectus Abdominis
Muscle Movements Table:
External Obliques:
Movement: Twisting at the waist; bending to the side
Target Motion Direction: Supination; lateral flexion
Origin: Ribs 5–12; ilium
Insertion: Ribs 7–10; linea alba; ilium
Rectus Abdominis:
Movement: Sitting up
Target Motion Direction: Flexion
Origin: Pubis
Insertion: Sternum; ribs 5–7
Transversus Abdominis:
Movement: Squeezing abdomen during exhalation
Target Motion Direction: Compression
Origin: Ilium; ribs 5–10
Insertion: Sternum; linea alba; pubis
The Intercostal Muscles
Role: assist in breathing by changing dimensions of the rib cage
Muscle Movements Table:
External Intercostals:
Movement: Inhalation; exhalation
Target Motion Direction: Elevation (expands thoracic cavity)
Origin: Rib superior to each intercostal muscle
Insertion: Rib inferior to each intercostal muscle
Internal Intercostals:
Movement: Forced exhalation
Target Motion Direction: Movement along superior/inferior axis
Origin: Rib inferior to each intercostal muscle
Insertion: Rib superior to each intercostal muscle
Mnemonic Device for Latin Roots
Muscles to Know:
Occipitofrontalis
Zygomaticus Major
Zygomaticus Minor
Masseter
Buccinator
Lateral Pterygoid
Medial Pterygoid
Temporalis
Orbicularis Oris
Orbicularis Oculi
External Obliques
Internal Obliques
Rectus Abdominis
Transverse Abdominis
External Intercostals
Internal Intercostals
Example Latin/Greek Translations:
ad: to; toward → "ADvance toward your goal"
ab: away from → n/a
sub: under → "SUBmarines move under water"
ductor: something that moves → "A conDUCTOR makes a train move"
anti: against → "If you are antisocial, you are against engaging in social activities"
epi: on top of → n/a
apo: to the side of → n/a
Length Descriptors:
longissimus: longest → "Longissimus is longer than the word long"
longus: long → long
brevis: short: brief → mini
maximus: large → max
medius: medium → "Medius and medium both begin with med"
minimus: tiny; little → mini
rectus: straight → "To RECTify a situation is to straighten it out"
multi: many → "If something is MULTIcolored, it has many colors"
uni: one: “A UNIcorn has one horn.”
bi/di: two → "If a ring is DIcast, it is made of two metals"
tri: three → "TRIple the amount of money is three times as much"
quad: four → "QUADruplets are four children born at one birth"
externus: outside → EXternal
internus: inside → INternal