Two-Jointed Muscles

Question 1

What are 2 jointed muscles ?

Answer 1

• also known as biarticular muscles
• muscles that cross/act on 2 joints rather than just one
• able to exert force & control movements at both ends

Question 2

What are 7 examples of two-jointed muscles?

Answer 2

• the hamstrings group (biceps femoris/semimembranosus/semitendinosus)
• biceps/triceps brachii
• gastrocnemius
• Rectus femoris

Question 3

What is the origin/insertion/innervation/joint crossed/main action of the biceps femoris ?

Answer 3

• O: has 2 heads, long head (Ischial tubersoity), short head (linea aspera)
• I: head of fibula
• Inn: sciatic nerve
• Jt crossed: hip & knee joint
• MA: hip extension, knee flexion, & lateral rotation of a flexed knee

Question 4

What is the origin/insertion/innervation/joint crossed/main action of the semimembranosus?

Answer 4

• O: ischial tuberosity
• I: Posteromedial tibial condyle
• Inn: sciatic nerve
• jt crossed: hip & knee joint
• MA: hip extension, knee flexion, & medial rotation of a flexed knee

Question 5

What is the origin/insertion/innervation/joint crossed/main action of the semitendinosus?

Answer 5

• O: ischial tuberosity
• I: medial surface of proximal tibia
• Inn: sciatic nerve
• jt crossed: hip & knee joint
• MA: hip extension, knee flexion, medial rotation of a flexed knee

Question 6

What is the origin/insertion/innervation/joint crossed/main action of the Rectus femoris?

Answer 6

• O: has 2 heads - straight (AIIS), curved (superior acetabulum)
• I: tibial tuberosity
• Inn: femoral nerve
• jt crossed: hip & knee joint
• MA: knee extension, hip flexion

Question 7

What is the origin/insertion/innervation/joint crossed/main action of the gastrocnemius ?

Answer 7

• O: medial/lateral femoral condyles
• I: posterior calcaneus
• Inn: tibial nerve
• jt crossed: knee & ankle joint
• MA: ankle plantar-flexion or knee flexion

Question 8

What is the origin/insertion/innervation/joint crossed/main action of the biceps brachii?

Answer 8

• O: has 2 heads - long head (supraglenoid tubercle of scapula), short head (coracoid process of scapula)
• I: radial tuberosity
• Inn: Musculocutaneous nerve
• jt crossed: glenohumeral & elbow joint
• MA: elbow & shoulder flexion, forearm supination

Question 9

What is the origin/insertion/innervation/joint crossed/main action of the triceps brachii?

Answer 9

• O: has 3 heads - long head (infraglenoid tubercle of scapula), lateral head (greater tubercle of posterior humerus), medial head (deep, halfway down posterior humerus shaft)
• I: olecranon process of ulna
• Inn: radial nerve
• Jt crossed: shoulder & elbow joint
• MA: elbow extension & shoulder extension (long head only)