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The branch of medicine concerned with the heart and its disorders. Electrical activation, blood flow, muscle function and valve mechanics provide complementary explanations of cardiac symptoms and measurements.

Disease of the heart muscle associated with structural or functional abnormalities. Different forms alter chamber size, wall thickness or relaxation, so the term identifies a broad class rather than one mechanical defect.

Carlo Matteucci investigated electric currents associated with muscle using sensitive galvanometers. Museo Galileo preserves an instrument marked for his muscle-current work in 1840: an astatic galvanometer with suspended needles, many turns of fine wire and a readable scale. The apparatus connects a weak electrical signal with a mechanical deflection, illustrating why instrument sensitivity and suppression of the background geomagnetic field mattered for early physiological measurements.^[ref]

Researcher in ion channel physiology. Saviane and collaborators used single-channel recordings and noise analysis to resolve the double-barreled behavior of a skeletal-muscle chloride channel and its alteration in myotonia congenita.^[ref]

The chest wall is the bony and soft-tissue envelope around the thorax, including the rib cage, sternum, thoracic part of the vertebral column, surrounding muscles and overlying tissues. It protects thoracic organs and participates in the mechanical expansion of the lungs. The respiratory diaphragm forms the lower partition of the thorax and acts with the chest-wall muscles during breathing.

Movement is central to its function. Contraction of the respiratory diaphragm and inspiratory intercostal muscles enlarges the thoracic space. Coupling through the pleura changes the pressure surrounding the lungs, allowing lung volume to increase and air to enter. OpenStax distinguishes the inward elastic recoil of the lungs from the opposing chest-wall tendency and discusses the ability of the thoracic wall to expand under pressure.^[ref]

Chest-wall compliance and lung compliance describe different elastic contributions. For an original small-change, static model, let $C_L$ and $C_W$ be their volume-change/pressure-change slopes. At shared volume change $\Delta V$, the pressure increments add:These are incremental elastic pressures around a specified equilibrium; their baseline values need not both be positive. The calculation assumes no airflow during the static comparison and omits airway resistance and active muscle-force changes.

With stipulated $C_L=C_W=0.20\mathrm{L}(\mathrm{cm}{\mathrm{H}}_2\mathrm{O}{)}^{-1}$, the combined slope is $0.10\mathrm{L}(\mathrm{cm}{\mathrm{H}}_2\mathrm{O}{)}^{-1}$. A 0.50 L increase therefore requires a 5 cm water pressure increment in this model, with 2.5 cm water assigned to each elastic contribution. These are explanatory values, not clinical reference limits.

A pressure-volume experiment must specify whether it measures the entire respiratory system or separates lung and chest-wall contributions. Pleural pressure and transpulmonary pressure provide different pressure references. Observing chest movement alone does not identify every elastic property or determine airflow: motion, pressure and flow are complementary measurements.

The coracoid process is an anterior projection from the scapula. It provides attachment for muscles and ligaments, including pectoralis minor. Its location supplies a recognizable landmark near several structures of the shoulder region.

Disease of the arteries supplying the heart muscle, commonly involving atherosclerotic narrowing. Limitation of blood supply can produce ischaemia, while the presence of a lesion and its immediate functional effect are separate questions.

Coronary atherosclerosis is atherosclerotic disease of the arteries supplying cardiac muscle. Its consequences can involve altered perfusion and plaque-associated events. The amount of narrowing and the tissue’s current oxygen demand are different determinants of whether supply is adequate.

Coronary blood flow perfuses the cardiac muscle through coronary vessels. Mechanical compression during contraction affects its timing, especially in the left ventricular wall. Consequently, coronary flow cannot be inferred from a static arterial pressure alone.

Disorder of the small vessels supplying the heart muscle. Impaired regulation of local flow can cause ischemia even when the major coronary arteries lack a large obstructing lesion.^[ref]

Movement between parts of the skull beyond ordinary lower-jaw rotation. joint surfaces, soft tissues, muscles and constraints elsewhere in the skull jointly determine realized movement.

The cricoid cartilage is the ring-shaped cartilage at the lower part of the larynx, above the trachea. Unlike the shield-shaped thyroid cartilage, it forms a complete cartilaginous ring, with a broader posterior plate. It helps support the airway and provides articulations and muscle attachments within the laryngeal framework.^[ref]

The ring geometry and its connections matter mechanically. Laryngeal muscles move connected cartilages to alter vocal-fold position and tension; those motions can change the opening through which air passes. A static anatomical ring therefore participates in an actively controlled valve and sound-producing assembly.

The deltoid muscle covers the shoulder with anterior, middle and posterior regions having different pulling directions. It contributes to arm elevation and position-dependent flexion or extension. Regional recruitment therefore matters when interpreting the force of the whole named muscle.

A descending motor pathway carries signals from more rostral neural centers toward brainstem or spinal circuits contributing to movement. Its effect depends on intervening interneurons and motor neurons. An anatomical projection is therefore not necessarily a direct command to one muscle.

Dilated cardiomyopathy is a form of cardiomyopathy involving enlargement of a ventricular chamber together with impaired pumping by the heart muscle. The left ventricle is a central site of the disorder, and other chambers can also be affected. Enlargement and pumping function are related but distinct observations; chamber size alone does not determine how much blood is expelled.^[ref]

A simple volume example makes that distinction quantitative. Let end-diastolic volume be $V_{\mathrm{ED}}$ and end-systolic volume be $V_{\mathrm{ES}}$. ThenHere SV is stroke volume and EF is ejection fraction. A stipulated chamber changing from $200$ to $150\mathrm{mL}$ ejects $50\mathrm{mL}$ with EF $25\%$. Another changing from $120$ to $60\mathrm{mL}$ ejects $60\mathrm{mL}$ with EF $50\%$. A larger filled volume need not produce a larger stroke volume. These are constructed mechanical examples, not diagnostic cutoffs or reference ranges.

Imaging can test several parts of this mechanism. Echocardiography follows chamber dimensions and contraction; cine magnetic resonance imaging can quantify volumes and longitudinal motion. In a primary study, Marcus Carlsson and colleagues compared twelve patients with dilated cardiomyopathy, twelve controls and twelve elite triathletes. Their analysis combined atrioventricular-plane displacement with anatomical area to investigate the longitudinal contribution to ventricular pumping.^[ref]

This experiment illustrates why the condition cannot be represented by one chamber diameter alone: geometry, motion and transported volume supply different information. Doppler echocardiography and its velocity-time integral provide complementary flow observations, while a clinical diagnosis also requires the surrounding evidence and cause of the myocardial abnormality.

Dysphagia means difficulty swallowing. It can involve preparation and transfer of material in the mouth, passage through the pharynx or movement down the oesophagus. These stages require coordinated muscle activity, sensation and neural control. Dysphagia names a functional difficulty rather than one unique disease or anatomical lesion. ^[ref]

Swallowing also protects the airway: food transport and temporary closure of the breathing passage must be coordinated. A delay in initiating the response and a mechanical obstruction can both disrupt swallowing through different mechanisms. Difficulty moving a bolus, pain during swallowing and entry into the airway are related observations but should not be treated as identical definitions.

Edward Frankland used calorimetry to compare the energy available from food with the work performed by muscle. His 1866 argument challenged the view that muscular work must chiefly consume the muscle's own substance. The comparison connected measured heats of oxidation with an energy balance for animal activity.^[ref]

Chemist whose 1866 calorimetric argument tested sources of muscular power.

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Recording electrical activity associated with muscle activation. Surface recording electrodes sample activity near the skin; electrode position and movement affect the signal.

Electrophysiology studies electrical properties and activity of biological cells and tissues. Recording membrane potential or current can connect ion transport to neural signaling, muscle activation and other functions. A measured voltage and the underlying ionic conductance are related but distinct quantities.

A cancer arising in the lining of the uterus. It is distinct from a uterine smooth-muscle tumor or a cervical cancer, making the tissue of origin important to classification.