LEC 08-09: Muscular system (Cranial & Axial)

Vocabulary-style flashcards covering key muscles, muscle groups, and relevant anatomy from the lecture notes.

Somites

Segmented blocks of paraxial mesoderm that differentiate into ribs, vertebrae, dermis, body muscles, tendons, and ligaments.

Muscular system

The organ system comprising all muscles, responsible for movement, posture, and heat production.

Contraction

Muscle shortening that produces movement; muscles can pull but cannot push.

Origin

Attachment point of a muscle that remains relatively fixed during contraction.

Insertion

Attachment point of a muscle that moves toward the origin when the muscle contracts.

Agonist (Prime mover)

The primary muscle producing a specific movement.

Antagonist

Muscle that opposes or reverses a movement.

Synergist

Muscle that adds force to a movement or helps prevent unwanted movement.

Fixator

A synergist that immobilizes a bone or muscle’s origin to improve leverage.

Parallel fascicle arrangement

Fascicles run parallel to the long axis of the muscle (e.g., sartorius).

Fusiform fascicle arrangement

Spindle-shaped muscles with a central belly (e.g., biceps brachii).

Pennate fascicle arrangement

Fascicles attach obliquely to a central tendon, giving a featherlike pattern.

Unipennate

Fascicles insert into one side of a central tendon.

Bipennate

Fascicles insert from both sides of a central tendon.

Multipennate

Two or more tendons with oblique muscle fibers.

Convergent fascicles

Fascicles converge from a broad origin to a single tendon.

Circular fascicles

Fascicles arranged in concentric rings around an opening (sphincters).

Deltoid

Triangular-shaped shoulder muscle.

Rectus

Fibers run straight along the axis (Latin for straight).

Transversus

Fibers run at a right angles or across the axis (transverse).

Oblique

Fibers run at an angle to the axis.

Galea aponeurotica

Cranial aponeurosis connecting the frontal and occipital bellies of the scalp.

Epicranius (occipitofrontalis)

Bipartite scalp muscle consisting of the frontalis and occipitalis.

Frontalis

Frontal belly of the epicranius; raises the eyebrows.

Occipitalis

Occipital belly of the epicranius; pulls scalp backward.

Orbicularis oculi

Muscle surrounding the eye; closes eyelids.

Orbicularis oris

Muscle surrounding the mouth; closes and puckers lips.

Zygomaticus major

Smiling muscle that raises the corners of the mouth.

Masseter

Major jaw-raising (elevating) muscle; a prime mover of mastication.

Temporalis

Masticatory muscle that elevates and retracts the mandible.

Cranial nerve V (trigeminal)

Nerve that innervates the muscles of mastication.

Genioglossus

Extrinsic tongue muscle that protrudes the tongue.

Styloglossus

Extrinsic tongue muscle that elevates and retracts the tongue.

Hyoglossus

Extrinsic tongue muscle that depresses the tongue.

Cranial nerve XII (hypoglossal)

Nerve that innervates the tongue muscles.

Suprahyoid muscles

Group moving the hyoid/larynx during swallowing (digastric, stylohyoid, mylohyoid, geniohyoid).

Infrahyoid muscles

Sternohyoid, sternothyroid, omohyoid, thyrohyoid; depress the hyoid and larynx after swallowing.

Sternocleidomastoid

Major head flexor; also helps with head rotation.

Splenius capitis

Deep neck muscle that extends or rotates the head.

Semispinalis capitis

Deep back muscle aiding head extension.

Trapezius

Superficial back muscle involved in moving and stabilizing the scapula.

Erector spinae

Primary back-extensor muscle group consisting of spinalis, longissimus, and iliocostalis.

Spinalis/Longissimus/Iliocostalis

Subgroups of the erector spinae running along the spine.

Quadratus lumborum

Deep trunk muscle aiding lateral flexion of the spine.

External intercostals

Muscles between ribs that elevate the ribs during inspiration.

Internal intercostals

Muscles between ribs that aid in forced expiration.

Diaphragm

Primary muscle of inspiration; dome-shaped with a central tendon.

Serratus anterior

Protracts and stabilizes the scapula against the thoracic wall.

Linea alba

Fibrous line along the midline of the abdomen; site of tissue attachment.

Transversus abdominis

Deep abdominal muscle with horizontal fibers; supports abdomen.

Internal oblique

Muscle with diagonal fibers; flexes and rotates trunk.

External oblique

Superficial oblique muscle; fibers run downward and medially.

Rectus abdominis

Anterior abdominal muscle that flexes the trunk.

Inguinal ligament

Free inferior border of the external oblique aponeurosis; forms groin boundary.