Arm Muscles Anatomy

Arm Muscles

Biceps

• Located in the anterior compartment of the upper arm
• Composed of two heads: long head and short head
• Origin: scapula (long head) and coracoid process (short head)
• Insertion: radial tuberosity
• Functions: flexion of the elbow, forearm supination, and shoulder flexion

Triceps

• Located in the posterior compartment of the upper arm
• Composed of three heads: medial, lateral, and long head
• Origin: scapula (long head) and posterior surface of the humerus (medial and lateral heads)
• Insertion: olecranon process of the ulna
• Functions: extension of the elbow and locking of the elbow joint

Brachialis

• Located in the anterior compartment of the upper arm
• Origin: anterior surface of the humerus
• Insertion: ulnar tuberosity
• Functions: flexion of the elbow

Anterior Compartment

• Muscles: biceps, brachialis, and coracobrachialis
• Functions: flexion of the elbow, forearm supination, and shoulder flexion
• Nerve supply: musculocutaneous nerve

Posterior Compartment

• Muscles: triceps and anconeus
• Functions: extension of the elbow and locking of the elbow joint
• Nerve supply: radial nerve

Arm Muscles

Biceps

• Located in the anterior compartment of the upper arm
• Composed of two heads: long head and short head
• Originates from the scapula (long head) and coracoid process (short head)
• Inserts into the radial tuberosity
• Functions include flexion of the elbow, forearm supination, and shoulder flexion

Triceps

• Located in the posterior compartment of the upper arm
• Composed of three heads: medial, lateral, and long head
• Originates from the scapula (long head) and posterior surface of the humerus (medial and lateral heads)
• Inserts into the olecranon process of the ulna
• Functions include extension of the elbow and locking of the elbow joint

Brachialis

• Located in the anterior compartment of the upper arm
• Originates from the anterior surface of the humerus
• Inserts into the ulnar tuberosity
• Functions include flexion of the elbow

Muscle Compartments

Anterior Compartment

• Contains muscles: biceps, brachialis, and coracobrachialis
• Functions include flexion of the elbow, forearm supination, and shoulder flexion
• Supplied by the musculocutaneous nerve

Posterior Compartment

• Contains muscles: triceps and anconeus
• Functions include extension of the elbow and locking of the elbow joint
• Supplied by the radial nerve

Muscles of the Anterior Compartment of Thigh

• The anterior compartment of thigh contains six muscles: sartorius, quadriceps femoris, rectus femoris, vastus lateralis, vastus medialis, and vastus intermedius
• These muscles act on the hip and knee joints
• Psoas major and iliacus muscles from the posterior abdominal wall act on the hip joint
• Sartorius and rectus femoris act on both the hip and knee joints
• Vastus muscles act on the knee joint

Quadriceps Femoris Muscle

• Consists of four muscles: rectus femoris, vastus lateralis, vastus medialis, and vastus intermedius
• Rectus femoris has two heads: straight head and reflected head
• Innervated by the femoral nerve (L2, L3, L4)
• Functions: flexes the thigh at the hip joint and extends the leg at the knee joint

Sartorius Muscle

• Originates from the anterior superior iliac spine
• Inserts into the medial surface of the tibia just inferomedial to the tibial tuberosity
• Innervated by the femoral nerve (L2, L3)
• Functions: flexes the thigh at the hip joint and extends the leg at the knee joint

Quadriceps Injury

• Includes avulsion of the muscles, proximal musculotendinous tears, and quadriceps tendon disruption
• Proximal injuries of the rectus femoris muscle occur frequently in professional athletes
• Quadriceps tendon disruption is a devastating injury that requires surgical reattachment

Patellar Ligament

• Functionally a continuation of the quadriceps femoris tendon below the patella
• Attached above to the apex and margins of the patella and below to the tibial tuberosity

Medial Compartment of Thigh

• Contains six muscles: gracilis, pectineus, adductor longus, adductor magnus, obturator externus, and brevis
• Adductor magnus is the largest and deepest muscle in the medial compartment
• Functions: adducts the thigh at the hip joint and extends the leg at the knee joint

Posterior Compartment of Thigh

• Contains three muscles: biceps femoris, semitendinosus, and semimembranosus (hamstrings)
• Hamstrings act on both the hip and knee joints
• Functions: extend the thigh at the hip joint and flex the leg at the knee joint

Hamstring Injuries

• Include tendon avulsion at the ischial tuberosity, and intermuscular, musculotendinous, and myofascial disruptions within the muscle bellies

• Caused by water skiing, track and field events, football, and soccer injuries, and rapid sprint injuries### Femoral Artery

• The femoral artery is the continuation of the external iliac artery.

• It begins at the level of the inguinal ligament.

Muscles of the Medial Compartment of Thigh

• Gracilis muscle:
  • Originates from the external surface of the pubis, inferior pubic ramus, and ramus of the ischium.
  • Inserts into the medial surface of the proximal shaft of the tibia.
  • Innervated by the obturator nerve (L2, L3).
  • Functions: adducts thigh at the hip joint and flexes the leg at the knee joint.
• Pectineus muscle:
  • Originates from the pectineal line (pecten pubis) and adjacent bone of the pelvis.
  • Inserts into the oblique line extending from the base of the lesser trochanter to the linea aspera on the posterior surface of the proximal femur.
  • Innervated by the femoral nerve (L2, L3).
  • Functions: adducts and flexes the thigh at the hip joint.
• Adductor longus muscle:
  • Originates from the external surface of the body of the pubis (triangular depression inferior to the pubic crest and lateral to the pubic symphysis).
  • Inserts into the linea aspera on the middle one-third of the shaft of the femur.
  • Innervated by the obturator nerve (L2, L3, L4).
  • Functions: adducts and medially rotates the thigh at the hip joint.
• Adductor brevis muscle:
  • Originates from the external surface of the body of the pubis and inferior pubic ramus.
  • Inserts into the posterior surface of the proximal femur and upper one-third of the linea aspera.
  • Innervated by the obturator nerve (L2, L3).
  • Functions: adducts the thigh at the hip joint.
• Adductor magnus muscle:
  • Adductor part: originates from the ischiopubic ramus and inserts into the posterior surface of the proximal femur, linea aspera, and medial supracondylar line.
  • Innervated by the obturator nerve (L2, L3, L4).
  • Functions: adducts and medially rotates the thigh at the hip joint.
  • Hamstring part: originates from the ischial tuberosity and inserts into the adductor tubercle and medial supracondylar line.
  • Innervated by the sciatic nerve (tibial division) (L2, L3, L4).
  • Functions: adducts and medially rotates the thigh at the hip joint.
• Obturator externus muscle:
  • Originates from the external surface of the obturator membrane and adjacent bone.
  • Inserts into the trochanteric fossa.
  • Innervated by the obturator nerve (posterior division) (L3, L4).
  • Functions: laterally rotates the thigh at the hip joint.

Muscles of the Posterior Compartment of Thigh

• Biceps femoris muscle:
  • Long head: originates from the inferomedial part of the upper area of the ischial tuberosity.
  • Short head: originates from the lateral lip of the linea aspera.
  • Inserts into the head of the fibula.
  • Innervated by the sciatic nerve (L5, S1, S2).
  • Functions: flexes the leg at the knee joint and extends the thigh at the hip joint.
• Semitendinosus muscle:
  • Originates from the inferomedial part of the upper area of the ischial tuberosity.
  • Inserts into the medial surface of the proximal tibia.
  • Innervated by the sciatic nerve (L5, S1, S2).
  • Functions: flexes the leg at the knee joint and extends the thigh at the hip joint.
• Semimembranosus muscle:
  • Originates from the superolateral impression on the ischial tuberosity.
  • Inserts into the groove and adjacent bone on the medial and posterior surface of the medial tibial condyle.
  • Innervated by the sciatic nerve (L5, S1, S2).
  • Functions: flexes the leg at the knee joint and extends the thigh at the hip joint.

Femoral Artery and Its Branches

• The femoral artery gives rise to several branches, including:
  • Superficial epigastric artery
  • Superficial external iliac artery
  • Superficial external pudendal artery
  • Deep external pudendal artery
  • Deep artery of the thigh
  • Medial circumflex femoral artery
  • Lateral circumflex femoral artery
  • First, second, and third perforating arteries
  • Adductor magnus muscle
  • Adductor hiatus

Deep Artery of the Thigh

• The deep artery of the thigh arises from the femoral artery and passes through the adductor hiatus.
• It gives rise to several branches, including:
  • Medial circumflex femoral artery
  • Lateral circumflex femoral artery
  • First, second, and third perforating arteries
  • Terminal end of the deep artery of the thigh
  • Popliteal artery

This quiz covers the basics of arm muscles, including the biceps and triceps, their locations, compositions, origins, insertions, and functions.