les muscules 🤌🥖

How are skeletal muscles named?

• Location (e.g., temporalis)

• Size (e.g., gluteus maximus)

• Shape (e.g., deltoid)

• Direction of fibers (e.g., rectus abdominis)

• Number of origins (e.g., biceps brachii)

• Action (e.g., flexor carpi radialis)

• Origin & Insertion (e.g., sternocleidomastoid)

key superficial skeletal muscles.

• Trapezius – Upper back

• Sternocleidomastoid – Neck

• Pectoralis major – Chest

• Biceps brachii – Upper arm

• Rectus abdominis – Abdomen

• Gastrocnemius – Calf

What are the origin and insertion of the masseter?

• Origin: Zygomatic arch

• Insertion: Angle and ramus of mandible

• Action: Elevates the mandible (closes the mouth)

What are the origin and insertion of the biceps brachii?

• Origin:

  • Long head: Supraglenoid tubercle of scapula

  • Short head: Coracoid process of scapula

• Insertion: Radial tuberosity of radius

• Action: Flexes the elbow and supinates the forearm

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• Location: Located on the upper arm, the biceps brachii has two heads (hence "biceps"), running from the shoulder to the elbow.

• Function: The biceps brachii flexes the elbow and supinates the forearm (rotating the forearm so the palm faces up).

• Identification: The biceps brachii is well-known for its bulging appearance when the arm is flexed. It is the muscle that forms the "peak" when a person shows their muscles.

What are the origin and insertion of the tibialis anterior?

• Origin: Lateral condyle and upper 2/3 of tibia

• Insertion: Medial cuneiform and first metatarsal bones

• Action: Dorsiflexes and inverts the foot

What are the origin and insertion of the sternocleidomastoid?

• Origin: Manubrium of sternum and clavicle

• Insertion: Mastoid process of temporal bone

• Action: Rotates and flexes the head

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• Location: Found on the sides of the neck, this muscle runs diagonally from the sternum and clavicle (collarbone) to the mastoid process of the skull.

• Function: It is responsible for rotating and flexing the head. When both muscles contract simultaneously, the head is flexed forward; when one side contracts, the head rotates to the opposite side.

• Identification: It is easily visible when turning the head to either side. The muscle appears as a prominent cord-like structure on each side of the neck.

What are the origin and insertion of the pectoralis major?

• Origin: Clavicle, sternum, and cartilage of ribs 1-6

• Insertion: Greater tubercle of humerus

• Action: Flexes, adducts, and medially rotates the arm

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• Location: This large, fan-shaped muscle is located on the chest, covering the upper part of the thorax.

• Function: It is responsible for flexing, adducting, and medially rotating the arm. It also plays a role in the movement of the shoulder and arm.

• Identification: It is easily visible in the upper chest, especially in muscular individuals. The pectoralis major is the muscle that gives the chest its shape.

What are the origin and insertion of the depressor labii inferioris?

• Origin: Mandible (near mental foramen)

• Insertion: Skin and muscles of the lower lip

• Action: Depresses the lower lip (frowning)

What are the origin and insertion of the gastrocnemius?

• Origin: Medial and lateral condyles of femur

• Insertion: Calcaneus via Achilles tendon

• Action: Plantar flexes the foot and flexes the knee

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• Location: Located in the calf, the gastrocnemius is the large muscle that forms the bulk of the lower leg.

• Function: It is primarily responsible for plantar flexion of the foot (pointing the toes) and also aids in knee flexion.

• Identification: The gastrocnemius is visible as a bulging muscle on the posterior part of the lower leg, especially when standing on tiptoe or flexing the knee.

What are the origin and insertion of the triceps brachii?

• Origin:

  • Long head: Infraglenoid tubercle of scapula

  • Lateral head: Posterior humerus

  • Medial head: Posterior humerus (below radial groove)

• Insertion: Olecranon of ulna

• Action: Extends the elbow

What are the origin and insertion of the rectus abdominis?

• Origin: Pubic crest and pubic symphysis

• Insertion: Xiphoid process and costal cartilages of ribs 5-7

• Action: Flexes the vertebral column and compresses abdomen

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• Location: The rectus abdominis is a long, flat muscle that runs along the front of the abdomen, from the pubic symphysis to the lower ribs and sternum.

• Function: It is responsible for flexing the vertebral column and compressing the abdomen, playing a major role in movements like bending forward and maintaining posture.

• Identification: It is often visible in the form of the "six-pack" in individuals with low body fat. It is the muscle that gives the abdomen a segmented appearance when well-defined.

Origin & Insertion - Trapezius

• Origin: Occipital bone, ligamentum nuchae, and spinous processes of C7-T12

• Insertion: Lateral third of clavicle, acromion, and spine of scapula

• Action: Elevates, retracts, and rotates the scapula

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• Location: The trapezius muscle is located in the upper back, covering the neck, shoulders, and part of the upper back.

• Function: It moves and stabilizes the scapula (shoulder blade). It is involved in actions such as raising, retracting, and rotating the scapula, and it also helps to extend the head and neck.

• Identification: It forms a large, triangular shape on the upper back. When a person shrugs their shoulders, the trapezius becomes very prominent.

Flexion

Decreasing the angle between two bones

Extension

Increasing the angle between two bones

Abduction

Moving a limb away from the midline (being abducted away)

Adduction

Moving a limb toward the midline (addressed to you)

Rotation

Circular movement around an axis

Circumduction

Circular movement of a limb

Supination

Palm facing up or forward

Pronation

Palm facing down or backward

Dorsiflexion

Flexing the foot upwards

Plantar flexion

Pointing the toes downward.

Masseter

• Action: Elevates the mandible (closes the jaw)

• Origin: Zygomatic arch

• Insertion: Angle and ramus of mandible

• Bones Involved: Mandible (lower jaw), zygomatic bone (cheekbone)

Biceps Brachii

• Action: Flexes the elbow and supinates the forearm

• Origin:

  • Long head: Supraglenoid tubercle of scapula

  • Short head: Coracoid process of scapula

• Insertion: Radial tuberosity of the radius

• Bones Involved: Scapula (shoulder blade), radius (forearm bone)

Tibialis Anterior

• Action: Dorsiflexes and inverts the foot

• Origin: Lateral condyle and upper 2/3 of tibia

• Insertion: Medial cuneiform and first metatarsal bones

• Bones Involved: Tibia (shin bone), tarsal bones (foot bones), metatarsal bones (foot bones)

Sternocleidomastoid

• Action: Rotates and flexes the head

• Origin: Manubrium of sternum and clavicle

• Insertion: Mastoid process of temporal bone

• Bones Involved: Sternum (breastbone), clavicle (collarbone), temporal bone (skull)

Pectoralis Major

• Action: Flexes, adducts, and medially rotates the arm

• Origin: Clavicle, sternum, and cartilage of ribs 1-6

• Insertion: Greater tubercle of humerus

• Bones Involved: Clavicle (collarbone), sternum (breastbone), ribs, humerus (upper arm bone)

Depressor Labii Inferioris

• Action: Depresses the lower lip (frowning)

• Origin: Mandible (near mental foramen)

• Insertion: Skin and muscles of the lower lip

• Bones Involved: Mandible (lower jaw)

Gastrocnemius

• Action: Plantar flexes the foot and flexes the knee

• Origin: Medial and lateral condyles of femur

• Insertion: Calcaneus (heel bone) via Achilles tendon

• Bones Involved: Femur (thigh bone), calcaneus (heel bone)

Triceps Brachii

• Action: Extends the elbow

• Origin:

  • Long head: Infraglenoid tubercle of scapula

  • Lateral head: Posterior humerus

  • Medial head: Posterior humerus (below radial groove)

• Insertion: Olecranon of ulna

• Bones Involved: Scapula (shoulder blade), humerus (upper arm bone), ulna (forearm bone)

Rectus Abdominis

• Action: Flexes the vertebral column and compresses the abdomen

• Origin: Pubic crest and pubic symphysis

• Insertion: Xiphoid process and costal cartilages of ribs 5-7

• Bones Involved: Pubis (pubic bone), xiphoid process (sternum), costal cartilages (rib cartilages)

Trapezius

• Action: Elevates, retracts, and rotates the scapula, extends the head and neck

• Origin: Occipital bone, ligamentum nuchae, and spinous processes of C7-T12

• Insertion: Lateral third of clavicle, acromion, and spine of scapula

• Bones Involved: Occipital bone (skull), clavicle (collarbone), scapula (shoulder blade)