Human Muscular Anatomy and Model Identification

Muscles of the Torso and Abdominal Wall

• Serratus Anterior     * Location and Model Identification: Found on the side of the body.     * Origin: Originates on the ribs.     * Insertion: Inserts on the medial border of the scapula or the scapula.     * Action: Functions to immediately rotate or protract the scapula.

• External Obliques (Identified as Number $3$)     * Description: Muscles that run crosswise across the abdomen.     * Actions:         * Permits flexion of the torso and spine.         * Allows for rotation of the torso.

• Internal Obliques (Identified as Number $5$)     * Model Context: Mentioned as present on the left side of the "crucial model," which represents the deep muscles, whereas the right side displays superficial muscles.     * Anatomy: The origin and insertion points are flipped compared to the external obliques.     * Actions: Similar to external obliques; they flex the torso and allow for rotation of the torso.

• Transverse Abdominis     * Anatomical Landmarks: Associated with the abdominal fascia.     * Extent: Stretches from the lower thoracic vertebrae down to the lumbar vertebrae and ends at the sacrum.     * Insertion: Inserts on the infracovertial sulcus.

Muscles of the Shoulder Girdle and Scapula

• Pectoralis Minor (Identified as Number $4$)     * Origin: Originates from ribs $2, 3, ext{ and } 4$ or $3, 4, ext{ and } 5$ (not as many ribs as the serratus anterior).     * Insertion: Goes up to the fourthoid process of the scapula.     * Action: Pulls the scapula forward; works in conjunction with the serratus anterior to pull the scapula forward or rotate it.

• Deltoid (Identified as Number $6$ and Number $1$)     * Origin: Originates all the way along the spine, along the acromion, and across the clavicle.     * Insertion: Inserts into the deltoid tuberosity.     * Action: Adducts the arm, pulling it up to the sides.     * Clarification: The speaker explicitly notes it does not "flex," despite common student errors.

• Rhomboids (Identified as Numbers $10 ext{ and } 11$)     * Note: Often not visible on certain models.     * Anatomy: Runs from the vertebrae to the scapula.     * Action: Retracts the scapula; may also provide slight elevation.

Posterior Shoulder and Rotator Group

• Supraspinatus (Identified as Number $12$)     * Anatomical Context: Located above the spine of the scapula.     * Description: Mentioned as one of the muscles worked on in "clay." It passes underneath the acromion.     * Insertion: Attaches to the head of the humerus.     * Action: Assists the deltoid with abduction by helping to pull the humerus up.

• Infraspinatus (Identified as Number $13$)     * Origin: Originates in the infraspinous fossa.     * Insertion: Inserts on the head of the humerus.     * Action: Pulls the humerus back (retraction).

• Teres Minor (Identified as Number $14$)     * Description: Referred to as the "little buddy" of the infraspinatus.     * Origin: Originates more or less from the infraspinous fossa.     * Insertion: Inserts on the head of the humerus.     * Action: Retracts the scapula (and/or humerus).

• Teres Major (Identified as Number $15$)     * Insertion: This is the third muscle mentioned that inserts on the intracavicular sulcus.     * Action: Adducts the fibrous (interpreted in context as humerus).

Muscles of the Thoracic Cage

• Internal Intercostals     * Origin: Originates from the inferior rib.     * Insertion: Inserts on the upper rib.     * Action: Depresses the ribs, ribcage, or the thoracic cavity by pulling the upper rib down.

• External Intercostals (Identified as Number $25$)     * Note: Present on the models mentioned.

Muscles of the Arm and Elbow Flexors

• Biceps Brachii (Identified as Number $2 ext{ and } 6$)     * Origin: Two heads—one from the scapula at the supraglenoid tubercle and one from the thoracoitic process.     * Insertion: Radial tuberosity.     * Action: Flexes the forearm and flexes the elbow.     * Clinical Distinction: Within a healthcare setting, one must differentiate between flexing the arm and flexing the forearm (elbow flexion).

• Brachialis (Identified as Number $3$ and observed behind the Biceps)     * Origin: Starts about halfway down the hubris (humerus) at the lateral hubris/anterior tuberous.     * Insertion: Down to the proximal part near the joint.     * Action: Flexor of the elbow.     * Identification: Can be distinguished from biceps because it starts much lower than the scapula.

• Brachioradialis (Identified as Number $4$ and $35$)     * Origin: Originates from the distal part of the humerus.     * Insertion: All the way down to the thyroid process of the radius.     * Action: Acts as an elbow flexor by pulling the styroid process toward the humerus.

Muscles of the Hip and Anterior Thigh

• Sartorius (Identified as Number $12$)     * Origin: Anterior superior iliac spine.     * Path: Crosses over the femur down to beneath the medial epicondyle of the tibia.     * Extent: Spans the whole length of the femur and almost the whole length of the pelvis.     * Action: Pulls up on the tibia to flex the hip or flex the fever (femur).

• Rectus Femoris (Identified as Number $13$)     * Origin: Anterior inferior iliac spine (pelvis).     * Path: Runs straight down the fever (femur).     * Insertion: Tibial porosity (tuberosity).     * Actions:         * Flexes the thigh or fever (femur).         * Extends the lower leg.

• Vastus Lateralis (Identified as Number $14$)     * Identification: Located laterally; associated with the long strip of fascia from the tensor fascia lata.     * Action: Extends the lower leg.

• Vastus Medialis     * Location: Medial side of the thigh.     * Action: Extends the lower leg.

• Tensor Fascia Lata (TFL)     * Description: Located near the lia (ilium); identified by a long strip of fascia going to the lateral side.

The Gluteal Region and Posterior Thigh (Hamstrings)

• Gluteus Maximus (Identified as Number $17$)     * Origin: Distal part of the ileum (posterior distal ileum) and the sacrum.     * Insertion: West patrol canter.     * Action: Extension; used to raise the body up, such as when going upstairs.

• Biceps Femoris (Identified as Number $18$)     * Location: Lateral muscle of the posterior thigh.     * Origin: Ischial tuberosity.     * Insertion: Tibia or epicondyle.     * Actions: Flexes the lower leg and extends the thigh.

• Semitendinosus (Identified as Number $19$)     * Location: Medial; lies right on top of the semimembranosus.     * Origin: Ischial tuberosity.     * Insertion: Tibia.     * Actions: Flexes the lower leg and extends the thigh.

• Semimembranosus (Identified as Number $20$)     * Description: Flatter muscle located beneath the semitendinosus.

Medial Thigh (Adductor Group)

• Gracilis (Identified as Number $21$)     * Insertion: Tibia.     * Action: Adducts the thigh.

• Adductor Magnus (Identified as Number $22$)     * Origin: Ischial tuberosity.     * Action: Adducts the thigh.

• Adductor Longus (Identified as Number $23$)     * Action: Adducts the thigh.

• Collective Adductor Attributes     * Origins: Superior pubic ramus, pubic body, and inferior pubic ramus.     * Insertions: Medial side of the femur (pectoralis toward the top, adductor longus further down).     * General Action: Adduct the thigh (pulling the thigh inward).

Muscles of the Lower Leg and Foot

• Tibialis Anterior (Identified as Number $26$)     * Action: Dorsiflexion; pulls up on the metatarsal and tarsal bones to allow standing on the heel.

• Extensor Digitorum Longus (Identified as Number $27$ "extension digit para lemongus")     * Insertion: Distal flanges (phalanges) of the four smaller toes.     * Action: Extends the four smaller toes.

• Extensor Hallucis Longus (Unnumbered small/tiny muscle)     * Origin: Referred to as "extension of palate is on this."     * Insertion: Distal phalange of the big toe (digit $1$).     * Action: Extends the big toe.

• Fibularis Longus (Identified as Number $28$)     * Location: Lateral side, named after the fibula.     * Origin: Posterior along the fibula.     * Insertion: Medial tarsals and metatarsals.     * Action: Plantar flex (raises the body onto the toes) because the origin is posterior.

• Gastrocnemius (Identified as Number $29$)     * Description: Superficial muscle.     * Origin: Epicondyle of the femur.     * Insertion: Calcaneus (calcaneopagus).     * Action: Plantar flex.

• Soleus (Identified as Number $30$)     * Description: Deeper muscle beneath the gastrocnemius.     * Action: Plantar flex.

Muscles of the Forearm and Hand

• Pronator Teres (Identified as Number $31$)     * Action: Short muscle that rotates the radius over the bone (ulna).

• Flexor Carpi Radialis (Identified as Number $32$)     * Location: Anterior side.     * Action: Flexes the wrist and pulls fingers forward.

• Palmaris Longus (Identified as Number $33$ "ulnaris elongation")     * Action: Flexes the palm or the wrist.

• Flexor Carpi Ulnaris (Identified as Number $34$ "flexor par five ulnaris joint")     * Note: Runs near the flexor ligature.

• Extensor Carpi Radialis Longus (Identified as Number $35$ "radial radial")     * Description: Listed as an extensor (though Number $35$ is also labeled brachioradial in transcript context, specific extensor carpi radialis longus is noted as stretching from the arm to the thumb).

• Extensor Carpi Radialis Brevis (Identified as Number $37$)     * Description: Shorter than the longus; previously not on the student list but mentioned for addition.

• Extensor Digitorum (Identified as Number $38$ "extensor digit part")     * Action: Extends the four shorter fingers.

• Extensor Carpi Ulnaris (Identified as Number $38$)

• Hand Muscle Mentions     * Mention of Adductor Pollicis Longus and Extensor Pollicis regarding thumb movement.

Questions & Discussion

• Common Errors Regarding Deltoid: Students often incorrectly state that the deltoid "flexes" because they see it moving. The speaker clarifies that its action is abduction, pulling the arms up to the sides.

• Clarification on Rib Origins: For Pectoralis Minor, the speaker initially mentions ribs $2, 3, ext{ and } 4$, then corrects/includes $3, 4, ext{ and } 5$.

• Elbow Flexion Terminology: The speaker emphasizes the importance of clinical accuracy: "clutches the forearm" really means "flexes the elbow." Understanding the difference between flexing the arm (shoulder) and flexing the forearm (elbow) is critical in healthcare settings.

• Distinguishing Biceps vs. Brachialis: A student can identify the brachialis because it originates halfway down the humerus, whereas the biceps brachii originate at the scapula.

• Distinguishing Vastus Muscles: Because the toes/feet aren't always visible on models, one should look for the Tensor Fasciae Latae to identify the lateral side (Vastus Lateralis) and the Adductor group to identify the medial side (Vastus Medialis).