The muscle labeled A is the
[ Select ]
Iliopsoas
tibialis posterior
Tensor Fascia Latae
rectus femoris
sartorius
popliteus
gastrocnemius
gracilis
, and B is the
[ Select ]
pectineus
Iliopsoas
adductor longus
gracilis
sartorius
vastus medialis
.

Question

The muscle labeled A is the 
[ Select ]
Iliopsoas
tibialis posterior
Tensor Fascia Latae
rectus femoris
sartorius
popliteus
gastrocnemius
gracilis
 , and B is the 
[ Select ]
pectineus
Iliopsoas
adductor longus
gracilis
sartorius
vastus medialis
 .

BlackTom AI · Accepted Answer

To begin, we examine which muscles are being referred to by the labels A and B based on their anatomical positions and primary actions.
Option set for A includes several hip and thigh muscles. The Iliopsoas is the main hip flexor, located anteriorly in the thigh/hip region, and it acts to flex the thigh at the hip joint. This makes it the most plausible candidate for a label A that is describing a primary hip flexor muscle.
Options such as tibialis posterior, which is a deep muscle of the posterior leg specialized in foot inversion and plantar flexion, or gastrocnemius, which crosses the knee and ankle and mainly contributes to plantar flexion of the foot, do not align with a straightforward hip- Flexor role. Rectus femoris spans both hip and knee joints but is a large knee extensor and hip flexor; however, given typical labeling in many diagrams, the Iliopsoas remains the cleaner and more primary choice for a direct hip flexor label.
The remaining options on A’s list (sartorius, popliteus, gracilis, etc.) are involved in hip/knee actions but are either not the primary hip flexors or have more specific secondary roles, making them less likely as the intended label for a primary hip flexor.
Moving to B, the correct choice is pectineus. The pectineus is a short, flat, triangular muscle on the upper anterior thigh near the medial aspect, contributing to hip flexion and, importantly, hip adduction. Among the listed B options, pectineus best matches a muscle that is commonly highlighted in the medial compartment/adductor region and is distinct from the other candidates like Iliopsoas (a primary hip flexor already used for A), adductor longus (also an adductor but typically more medial and deeper in the thigh), gracilis (a long strap-like muscle running medially with some hip adduction and knee flexion), sartorius (the longest muscle running obliquely across the thigh), and vastus medialis (a component of the quadriceps primarily extending the knee).
Now, consider why the other B options are less appropriate: Iliopsoas repeats the A answer, which would be redundant and anatomically unlikely for B in a two-label diagram; adductor longus is a strong hip adductor but is not as proximally located in the anterior region as pectineus for a paired anterior-medial labeling; gracilis and sartorius are more distal and functionally distinct (gracilis adds medial rotation and knee flexion; sartorius spans across the thigh and is known for its “tailor’s” action rather than a primary adductor/flexor grouping in this context); vastus medialis is a knee extensor, not a primary hip muscle.
In summary:
- A is Iliopsoas because it is the principal hip flexor located anteriorly and commonly used as the canonical example of a hip flexor in anatomy labeling.
- B is pectineus because it lies in the medial/upper thigh region and contributes to hip flexion and adduction, fitting a distinct second muscle in a paired labeling task.
If you were to doubt the other options, you’d be relying on less direct roles (foot/ankle actions for tibialis posterior, knee-dominant actions for vastus medialis or gastrocnemius), or confusing the primary movers in the hip region with muscles whose main actions do not center on hip flexion or medial thigh adduction as a primary function.

2025FA-HES-207-001 A. Exam #3B - no lockdown

The muscle labeled A is the [ Select ] Iliopsoas tibialis posterior Tensor Fascia Latae rectus femoris sartorius popliteus gastrocnemius gracilis , and B is the [ Select ] pectineus Iliopsoas adductor longus gracilis sartorius vastus medialis .

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