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The structure indicated is the quadratus femoris muscle.
The quadratus femoris muscle is one of the muscles of the gluteal region. The muscles in the gluteal region are divided into a superficial and deep group. There are four muscles of the superficial group:
There are 5 muscles in the deep group:
The deep muscles of the thigh are much smaller than the superficial group of muscles and generally serve to laterally rotate the femur at the hip joint.
The quadratus femoris muscle is the most inferiorly located muscle in the deep gluteal region of muscles and is named according to its approximately rectangular shape.
Origin: Lateral margin of obturator ring (above ischial tuberosity)
Insertion: Quadrate tubercle and intertrochanteric crest of proximal posterior femur
Action: Lateral rotation of hip. Assists with adduction of hip
Innervation: Nerve to quadratus femoris
Learn more about the anatomy of the thigh and gluteal muscles in this tutorial.
The structure indicated is the pisiform bone of the hand.
There are three groups of bones in the hand:
The carpal bones are separated into two rows:
The pisiform bone is one of four bones in the proximal row of carpals (scaphoid, lunate, triquetral, pisiform). The pisiform bone is a tiny sesamoid bone located in the tendon of the flexor carpi ulnaris muscle. It articulates with the palmar surface of the triquetral bone.
Learn more about the anatomy of the bones of the hand in this tutorial.
The structure indicated is the first dorsal interosseous muscle of the hand.
The dorsal interossei belong to the intrinsic group of muscles which act on the hand. The intrinsic muscles include the following muscles/groups:
All the intrinsic muscles of the hand, except the thenar muscles and the lateral two lumbrical muscles are innervated by the deep branch of the ulnar nerve. The thenar muscles and the lateral two lumbrical muscles are innervated by the median nerve. A useful mnemonic for remembering this is MEATLOAF. “MEAT” refers to the Median nerve, and LOAF refers to the muscles which it innervates: Lateral two lumbricals, Opponens pollicis, Abductor pollicis brevis, Flexor pollicis brevis.
The interosseous muscles, as the name suggests are located between (inter-) the metacarpal bones (-osseus). There are 4 bipennate dorsal interossei located between the adjacent shafts of the metacarpal bones and insert onto the bases of the proximal phalanges and the extensor hoods. The dorsal interossei serve to abduct the fingers away from the central axis of the middle finger. The first interosseous muscle inserts onto the base laterally on the index finger.
The palmar interossei in contrast are unipennate in structure and function to adduct the fingers towards the central axis of the middle finger. A useful mnemonic for remembering this function is PAD and DAB: Palmar interossei AD-duct, Dorsal interossei AB-duct.
Learn more about the anatomy of the hand muscles in this tutorial.
The structure indicated is the first metatarsal bone of the foot.
The foot contains three groups of bones:
There are 7 tarsal bones, and 5 metatarsals. The metatarsals are numbered from 1 to 5 from medial to lateral, with the first metatarsal belonging to that of the great toe (hallux) and the 5th metatarsal belonging to that of the little toe.
The metatarsals consist of the following parts:
Learn more about the anatomy of the bones of the foot in this anatomy tutorial.
The structure indicated is the talus bone of the foot.
The foot contains three groups of bones:
The talus is one of seven tarsal bones. There are three groups of tarsal bones:
There are two bones in the proximal group of tarsal bones: the talus and the calcaneus. The calcaneus is the largest tarsal bone and forms the heel through its posterior projection. The talus articulates with the medial malleolus of the tibia and the lateral malleolus of the fibula to form the ankle joint. In addition, it articulates with two other tarsal bones: the calcaneus inferiorly, and the navicular anteriorly.
The talus consists of the following main components:
Learn more about the bones of the foot in this anatomy tutorial.