Upper Extremity Neurovasculature and Introduction to Muscles: Shoulder Girdle

Vocabulary practice flashcards covering upper extremity blood and lymphatic vasculature, peripheral and central nervous systems, muscle physiology, neuromuscular transmission, and shoulder girdle musculature.

Arteries

Blood vessels that carry oxygen-rich ($O_2$ rich) blood away from the heart to the capillaries.

Arterioles

Smaller arterial branches that transition directly into capillary beds.

Capillaries

Microscopic exchange vessels where the exchange of materials and gases ($O_2 \rightarrow CO_2$) occurs between the blood and tissues.

Venules

Small vessels that collect blood from capillaries and transition into veins.

Veins

Blood vessels that carry deoxygenated ($O_2$ poor) blood back toward the heart.

Anastomoses

Direct connections between blood vessels that provide collateral routes for blood flow.

Lymphatic Vessels

Vessels that drain excess tissue fluid and return it to the bloodstream to maintain blood volume and blood pressure, while defending the body against pathogens.

Superior Vena Cava (SVC)

One of the largest veins of the body; drains deoxygenated blood from the head, neck, and upper extremities into the right atrium.

Inferior Vena Cava (IVC)

One of the largest veins of the body; drains deoxygenated blood from the lower body (abdomen, pelvis, and lower extremities) into the right atrium.

Right Lymphatic Duct

Lymphatic vessel that drains lymph from the right upper limb, right side of the head, and thorax, emptying into the venous system at the junction of the right internal jugular and subclavian veins.

Thoracic Duct

Large lymphatic vessel that collects lymph from the rest of the body and empties into the venous system at the junction of the left internal jugular and subclavian veins.

Central Nervous System (CNS)

Division of the nervous system consisting of the brain and spinal cord; acts as the primary control center that interprets sensory input and dictates motor output.

Peripheral Nervous System (PNS)

Division of the nervous system consisting of cranial nerves, spinal nerves, and ganglia outside the central nervous system.

Neuron

The basic structural and functional unit of the nervous system; specialized to respond to stimuli, conduct electrochemical impulses, and release neurotransmitters.

Dendrites

Receptive branchings of a neuron that receive information from other cells and transmit electrical signals toward the cell body.

Axon

Long neuronal extension that generates and conducts nerve impulses away from the cell body toward other cells.

Astrocyte

The most abundant and versatile neuroglia in the CNS; supports and braces neurons, anchors neurons to nutrient supplies, determines capillary permeability, and controls the chemical environment.

Microglial Cells

Defensive glial cells in the CNS that monitor neuron health and transform into specialized macrophages to phagocytize microorganisms and neuronal debris.

Ependymal Cells

Glial cells lining the fluid-filled central cavities of the brain and spinal cord, forming a permeable barrier and utilizing cilia to circulate cerebrospinal fluid (CSF).

Oligodendrocytes

Supporting cells in the CNS with cytoplasmic processes that form insulating myelin sheaths around thicker nerve fibers.

Schwann Cells

Supporting glial cells that wrap around all nerve fibers in the PNS to form myelin sheaths; vital for the regeneration of damaged peripheral axons.

Satellite Cells

Supporting glial cells that surround neuron cell bodies within ganglia in the PNS, functioning similarly to CNS astrocytes.

Ventral Root

Spinal cord root containing motor (efferent) fibers arising from the ventral horn motor neurons to innervate skeletal muscles.

Dorsal Root

Spinal cord root containing sensory (afferent) fibers arising from neurons in the dorsal root ganglion that carry sensory information from periphery to spinal cord.

Cauda Equina

The collection of lumbar and sacral nerve roots extending inferiorly through the lower vertebral canal resembling a horse's tail.

Nerve Plexus

A complex, interlacing network of nerves formed exclusively by branching and recombining ventral rami of spinal nerves (except $T2-T12$).

Phrenic Nerve

Major nerve arising from the cervical plexus ($C3-C5$) that supplies both motor and sensory innervation to the diaphragm.

Brachial Plexus

Somatic nerve plexus formed by the ventral rami of spinal nerves $C5-T1$ that supplies motor and sensory innervation to the shoulder and upper limb.

Axillary Nerve

Terminal branch of the posterior cord of the brachial plexus; travels posterior to the surgical neck of the humerus to innervate the deltoid and teres minor muscles.

Musculocutaneous Nerve

Major terminal branch of the lateral cord that innervates the anterior arm flexor muscles (biceps brachii, brachialis, coracobrachialis) and provides cutaneous sensation to the lateral forearm.

Median Nerve

Peripheral nerve formed by medial and lateral cords that travels anteriorly down the arm to innervate most forearm flexors, forearm pronators, and $5$ intrinsic hand muscles of the lateral palm.

Ulnar Nerve

Peripheral nerve arising from the medial cord that courses posterior to the medial epicondyle to innervate flexor carpi ulnaris, medial flexor digitorum profundus, and most intrinsic hand muscles.

Radial Nerve

The largest branch of the brachial plexus and direct continuation of the posterior cord; wraps around the humerus in the radial groove to innervate the extensor muscles of the upper limb.

Long Thoracic Nerve

Branch of the brachial plexus arising from ventral roots $C5, C6, C7, (C8)$ that innervates the serratus anterior muscle.

Dorsal Scapular Nerve

Nerve arising from $C4-C5$ nerve roots that provides motor innervation to rhomboid major, rhomboid minor, and levator scapulae.

Suprascapular Nerve

Nerve arising from the upper trunk ($C4-C6$) of the brachial plexus that innervates the supraspinatus and infraspinatus muscles.

Epimysium

Dense connective tissue sheath forming the outer covering around an entire skeletal muscle belly.

Perimysium

Layer of fibrous connective tissue that gathers muscle fibers into bundles called fascicles.

Endomysium

Delicate sheath of connective tissue surrounding each individual skeletal muscle fiber.

Tendon

A tough band of dense regular connective tissue connecting muscle to bone.

Aponeurosis

A broad, flat sheet of dense connective tissue that attaches skeletal muscles to other muscles or to bone.

Motor Unit

A single somatic motor neuron and all the skeletal muscle fibers that it innervates.

Neuromuscular Junction

The specific anatomical synapse where an axon terminal of a motor neuron makes functional contact with the sarcolemma of a muscle fiber.

Acetylcholine (ACh)

Neurotransmitter released from motor axon terminals into the synaptic cleft to initiate muscle depolarization and contraction.

Depolarization

The decrease in membrane potential where the interior of the cell becomes more positive due to the rapid influx of sodium ($Na^+$) ions.

Sarcoplasmic Reticulum (SR)

Specialized endoplasmic reticulum in muscle fibers that stores and releases calcium ($Ca^{2+}$) ions in response to an electrical action potential.

Sarcomere

The basic contractile functional unit of a myofibril, delineated between two successive Z discs and composed of actin and myosin filaments.

Cross-Bridge

The attachment of an energized myosin head to an exposed binding site on an actin filament during muscle contraction.

Concentric Contraction

An isotonic contraction during which the muscle actively shortens and its origin and insertion move closer together.

Eccentric Contraction

An isotonic contraction where a muscle actively generates force while lengthening, decelerating body parts with gravity.

Agonist (Prime Mover)

The muscle that bears the primary responsibility for producing a specific anatomical movement.

Antagonist

A muscle that opposes or reverses the action of another muscle.

Trapezius

Large superficial posterior muscle divided into upper, middle, and lower fibers that elevates, depresses, adducts, and upwardly rotates the scapula; innervated by cranial nerve XI and $C2-C4$.

Rhomboid Major

Muscle originating on the spinous processes of $T2-T5$ and inserting on the medial border of the scapula that adducts, elevates, and downwardly rotates the scapula; innervated by the dorsal scapular nerve ($C4-C5$).

Rhomboid Minor

Muscle originating on the spinous processes of $C7-T1$ and inserting on the upper medial border of the scapula that adducts, elevates, and downwardly rotates the scapula; innervated by the dorsal scapular nerve ($C4-C5$).

Levator Scapulae

Muscle originating from transverse processes of $C1-C4$ and inserting on the superior medial border of the scapula that elevates and downwardly rotates the scapula.

Serratus Anterior

Muscle originating from the external surfaces of ribs $1-8/9$ and inserting on the anterior surface of the medial scapular border; abducts and upwardly rotates the scapula while holding it against the thorax.

Pectoralis Minor

Anterior thoracic muscle originating from ribs $3-5$ and inserting onto the coracoid process of the scapula; acts to depress, abduct, downwardly rotate, and anteriorly tilt the scapula.