Final Answer:
The psoas major muscle connects at the body of the vertebrae, beginning at the twelfth thoracic vertebra (T12).
Step-by-step explanation:
The psoas major muscle, a crucial component of the hip flexors, originates from the bodies of the lumbar vertebrae and the intervertebral discs. Specifically, its origin extends from the twelfth thoracic vertebra (T12) through the lumbar vertebrae, including the five lumbar vertebrae (L1-L5). The muscle then descends alongside the lumbar spine, eventually joining the iliacus muscle to form the iliopsoas muscle, which inserts into the lesser trochanter of the femur.
In anatomical terms, the numbering of the vertebrae follows a systematic pattern. The vertebrae in the spine are categorized into regions such as cervical (C1-C7), thoracic (T1-T12), lumbar (L1-L5), sacral (S1-S5), and coccygeal (Co1-Co4). Therefore, when identifying the starting point of the psoas major muscle, it's essential to pinpoint the specific vertebra within this classification.
The twelfth thoracic vertebra (T12) marks the beginning of the psoas major muscle's connection to the vertebral column. This anatomical knowledge is fundamental for understanding the muscle's function and its relevance in movements involving the hip joint.