Diaphragma
The diaphragm is a dome-shaped sheet of muscle and tendon that forms the partition between the thoracic and abdominal cavities. It has sternal, costal, and lumbar (crural) parts and inserts into a strong central tendon. Contraction flattens the dome, increases thoracic volume, and draws air into the lungs (inspiration). It is also involved in the abdominal press used for defecation, urination, and parturition. Innervation is via the phrenic nerve (primarily C5–C7). In the horse at the canter and gallop there is usually a 1:1 locomotor-respiratory coupling: the horse typically takes one breath per stride. Movement of the abdominal viscera (a proposed "visceral piston"), back flexion and abdominal-muscle contraction have all been suggested to help link breathing to the stride; equine studies disagree on how much the visceral piston contributes. This is why respiratory disease so profoundly limits performance. The diaphragm contains openings for the aorta, esophagus, and caudal vena cava.
Origin: Sternal part: xiphoid process. Costal part: medial surfaces of ribs 8-18 and their costal cartilages. Lumbar part (crura): ventral surfaces of L1-L4 vertebrae
Insertion: Central tendon (centrum tendineum) — a strong aponeurosis at the dome
Action: Primary muscle of inspiration; contraction flattens the dome, increasing thoracic volume and drawing air into the lungs; also involved in abdominal press (defecation, urination, parturition)
Innervation: Phrenic nerve (C5-C7)
Diaphragmatic hernia (congenital or traumatic) allows abdominal organs into the chest; it most often causes colic, and respiratory compromise is less frequent. Phrenic-nerve damage is rare but devastating. The diaphragm is evaluated indirectly via respiratory pattern, auscultation, and imaging.
## Overview Diaphragmatic hernia is a rupture of the diaphragm allowing abdominal viscera to enter the thoracic cavity. Clinical signs are primarily those of acute colic, with or without respiratory
## Overview Synchronous diaphragmatic flutter, or thumps, is involuntary rhythmic contraction of the diaphragm synchronized with the heartbeat. It is often associated with low blood calcium or other
In horses with severe equine asthma (RAO/heaves), airway obstruction increases the effort needed to breathe, particularly during expiration. The classic 'heave line' along the abdomen reflects increas
Labored breathing at rest, especially after trauma or colic surgery, needs immediate veterinary attention. A horse that cannot keep up at the canter or gallop may have a respiratory limitation that involves diaphragmatic function indirectly.
## Overview Diaphragmatic hernia is a rupture of the diaphragm allowing abdominal viscera to enter the thoracic cavity. Clinical signs are primarily those of acute colic, with or without respiratory compromise. Diagnosis relies on imaging or surgical exploration, and treatment is surgical repair. ## Causes Trauma or congenital defect. ## Diagnosis Radiographs, ultrasound, or findings at colic surgery. ## Treatment Surgical reduction of herniated organs and closure of the diaphragmatic rent when feasible. ## Recovery and Prognosis Guarded to poor. ## Prevention Trauma avoidance. Signs include: respiratory distress; colic; decreased lung sounds on one side; acute or chronic presentation
## Overview Synchronous diaphragmatic flutter, or thumps, is involuntary rhythmic contraction of the diaphragm synchronized with the heartbeat. It is often associated with low blood calcium or other electrolyte imbalances, classically in endurance horses after prolonged exercise and heavy sweating. Visible flank twitching matches the heart rate. It can accompany electrolyte disturbances or other illness and needs veterinary assessment; treatment depends on the cause. ## Causes Hypocalcemia and electrolyte losses from sweating, or other causes of low calcium. ## Diagnosis Observation of flank twitching synchronous with the heartbeat, plus blood electrolyte measurement. ## Treatment Intravenous calcium and fluids when indicated by the veterinarian. Rest. Response depends on the underlying cause. ## Recovery and Prognosis Often good with prompt treatment, but outcome depends on any underlying disease. ## Prevention Electrolyte supplementation during prolonged exercise and attention to calcium balance. Signs include: visible rhythmic flank twitching synchronized with the heartbeat; occurs during or after prolonged exercise; indicates electrolyte depletion
In horses with severe equine asthma (RAO/heaves), airway obstruction increases the effort needed to breathe, particularly during expiration. The classic 'heave line' along the abdomen reflects increased abdominal (expiratory) effort, with hypertrophy of the external abdominal oblique muscles. Signs include: Increased abdominal effort during expiration (double lift); heave line visible along the costal arch; exercise intolerance; chronic cough; nasal discharge; worse in dusty environments.
Diaphragmatic hernia (congenital or traumatic) allows abdominal organs into the chest; it most often causes colic, and respiratory compromise is less frequent. Phrenic-nerve damage is rare but devastating. The diaphragm is evaluated indirectly via respiratory pattern, auscultation, and imaging.
Labored breathing at rest, especially after trauma or colic surgery, needs immediate veterinary attention. A horse that cannot keep up at the canter or gallop may have a respiratory limitation that involves diaphragmatic function indirectly.
See the Diaphragm on our interactive 3D horse model. Open 3D Model