Muscles

Long Head of Triceps Brachii

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Long Head of Triceps Brachii The structure indicated is the long head of the triceps brachii. The triceps brachii is the sole muscle in the posterior compartment of the arm. As the name suggests, the triceps brachii has three heads: Long head Medial head Lateral head These three heads converge to insert on the olecranon of the ulna. Origin: Long head – infraglenoid tubercle of scapula Medial head – posteriorly on the shaft of the humerus below the radial groove Lateral head – posteriorly on the humerus, above the radial groove Insertion: Olecranon of the ulna Action: Extension of the forearm …

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Triceps Brachii - Long Head

Sternocleidomastoid Muscle

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Sternocleidomastoid Muscle The muscle shown in the image is the sternocleidomastoid muscle. Origin: manubrium and medial aspect of clavicle Insertion: mastoid process of the temporal bone, superior nuchal line Innervation: motor innervation via the accessory nerve (Cranial nerve 11), sensory innervation from the cervical plexus Blood Supply: Superior thyroid artery and occipital artery Action: If the muscle contracts on one side, then cervical rotation to the opposite side occurs whilst cervical lateral flexion occurs on the same side. With bilateral contraction, cervical flexion occurs and the manubrium is elevated – in this way it assists inspiration, and is one of the accessory muscles of …

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sternocleidomastoid

Masseter

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Masseter The muscle highlighted is the masseter. This muscle is one of the muscles of mastication. The muscles of mastication include: Masseter Temporalis Medial pterygoid Lateral pterygoid The masseter is rectangular in shape and consists of a superficial part and a deep part. Origin: zygomatic arch and maxillary process of the zygomatic bone Insertion: lateral surface of ramus of mandible Innervation: masseteric nerve – a branch of the mandibular nerve (V3) Blood supply: masseteric artery To learn more about the muscles of mastication, check out this tutorial!

Masseter

Biceps Brachii

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Biceps Brachii The biceps brachii is a muscle in the anterior compartment of the arm. It has two heads, the long head and the short head. It is one of three muscles in the anterior compartment of the arm, the other two muscles being the brachialis and the coracobrachialis, which lie deep to it. The biceps muscle receives innervation via the musculocutaneous nerve and it functions mainly to supinate the forearm and flex the elbow. Despite being a relatively small muscle, the biceps brachii is one of the most highly trained muscles in the gym, along with the pectoral muscles …

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Biceps Brachii

Pectoralis Major

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Pectoralis Major The pectoralis major is one of the muscles in the pectoral region of the thorax. The other muscles in this region include the pectoralis minor and the subclavius. The pectoralis minor lies underneath the pectoralis major, and is a much smaller muscle – hence the name. The subclavius, as the name suggests, is located under (“sub”) the clavicle (“clavius”), attaching at one end to the bottom of the clavicle. And at the other to the first rib. The pectoralis major muscle has a few actions at the shoulder joint: flexion adduction medial rotation There are two main parts …

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Pectoralis Major Muscle

Vastus Medialis

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Vastus Medialis The vastus medialis is one of the muscles that makes up the quadriceps femoris, and is contained in the anterior compartment of the thigh. It is responsible for the tear-drop shape that is visible on the medial aspect of the thigh in trained athletes and footballers. The four muscles that make up the quadriceps femoris are the: –         Rectus femoris –         Vastus lateralis –         Vastus medialis –         Vastus intermedius   Learn more about the muscles of the anterior compartment in this tutorial. Click here to visualise and interact with these muscles.

Vastus Medialis

Arrector Pili

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Arrector Pili The arrector pili muscles are small smooth muscles which attach to hair follicles. When these muscles contract, they make your hair stand on end – a phenomenon which may better known to you as “goosebumps”. These muscles are not under conscious control, but are innervated by the sympathetic component of the autonomic nervous system. Find out more about the autonomic nervous system in this tutorial.

Arrector Pili