📝 STANDARD DESCRIPTION:
Position: In middle mediastinum, from 3rd to 6th rib, slightly LEFT of midline (60% left).
Shape: Cone-shaped — BASE (top, where vessels enter) and APEX (bottom).
Chambers: 4 — Right & Left Atria (top); Right & Left Ventricles (bottom).
Surface Grooves:
- Coronary groove (around base) — separates atria from ventricles.
- Right & Left longitudinal grooves — mark the position of interventricular septum.
Valves (4):
- Right AV (Tricuspid)
- Left AV (Bicuspid/Mitral)
- Pulmonary semilunar
- Aortic semilunar
Heart Bones (Ossa cordis) in Ox: Two bones in fibrous skeleton at base of aorta — characteristic of ruminants.
Coverings: Pericardium (Fibrous + Serous: parietal + visceral layers).
📚 DETAILED DESCRIPTION:
THE PUMP OF THE BODY — HEART
The heart is a muscular pump, the size of the animal's clenched fist (in ox about the size of a football). It lies in the middle mediastinum of the chest, enclosed in a tough sac called the pericardium.
POSITION (OX):
• Cranial limit: 3rd rib
• Caudal limit: 6th rib
• Slightly tilted: about 60% lies to the LEFT of midline, 40% to the right.
• The base (broad top, with great vessels entering/leaving) faces upward & forward.
• The apex (pointed lower end) faces downward & backward, near the sternum at the level of the 5th-6th costochondral junction.
FOUR CHAMBERS:
• Right Atrium: Receives deoxygenated blood from cranial and caudal vena cavae and the coronary sinus.
• Right Ventricle: Pumps blood to the lungs via the pulmonary trunk.
• Left Atrium: Receives oxygenated blood from the pulmonary veins (4-6 of them).
• Left Ventricle: Pumps blood to the whole body via the aorta. Wall is THICKEST (3× right ventricle).
SURFACE GROOVES (FAT-FILLED):
• Coronary (atrioventricular) groove: Encircles the heart between atria and ventricles. Carries the main coronary vessels.
• Paraconal interventricular groove (left longitudinal): On the left/cranial surface; marks position of interventricular septum.
• Subsinuosal interventricular groove (right longitudinal): On the right/caudal surface.
FOUR VALVES — keep blood moving in one direction:
• Right AV valve (Tricuspid) — between right atrium and right ventricle (3 cusps).
• Left AV valve (Bicuspid/Mitral) — between left atrium and left ventricle (2 cusps).
• Pulmonary semilunar valve — at start of pulmonary trunk.
• Aortic semilunar valve — at start of aorta.
OSSA CORDIS (BONES OF HEART): In adult ruminants there are two small bones (right and left os cordis) in the fibrous skeleton of the heart at the base of the aorta. Their job is to support the heart valves under high pressure. They are a unique ruminant feature (and develop with age in old animals).
PERICARDIUM:
• Outer fibrous pericardium — tough, anchors heart to sternum and diaphragm.
• Inner serous pericardium — has a parietal layer (lining the fibrous pericardium) and a visceral layer (= epicardium, on heart surface). Between them is a tiny amount of fluid for smooth sliding.
// COMPARATIVE ANALYSIS
| HORSE |
Larger and more rounded; left longitudinal groove only (no right). NO ossa cordis (cartilage instead). |
| DOG |
Almost ovoid; apex more pointed. No ossa cordis. |
| PIG |
Similar to ox but smaller; ossa cordis usually absent. |
| FOWL |
Right AV valve is a single MUSCULAR FLAP (not membranous). No coronary sinus. 4 chambers but architecture different. |
CLINICAL RELEVANCE
Traumatic Reticulopericarditis ('Hardware Disease', cattle): A swallowed nail or wire pierces the reticulum (forward part of stomach) and travels through the diaphragm into the pericardium → infection of the heart sac → fluid accumulation → heart failure.
Cardiac auscultation: Best heard on the LEFT side, low on chest, in the 3rd-5th intercostal space.
