📝 STANDARD DESCRIPTION:
Two lungs: Right (larger, ~58%) and Left (smaller, ~42% — heart pushes it).
OX Lobes:
- RIGHT LUNG (5 lobes): Cranial (split into Cranial part + Caudal part by cardiac notch), Middle, Caudal, Accessory.
- LEFT LUNG (3 lobes / 2 lobes seen): Cranial (split into Cranial part + Caudal part), Caudal. (Middle lobe absent on left.)
- Tracheal Bronchus goes to the cranial part of the cranial lobe of the RIGHT lung.
Surface: Strongly LOBULATED in ox/pig (visible 'tile' pattern); smooth in horse/dog.
Surfaces: Costal, Mediastinal, Diaphragmatic.
Hilus (Root) on mediastinal surface — where bronchus, pulmonary vessels, nerves enter.
Pleural sacs: Each lung in its own pleural sac (right & left don't communicate in ox = COMPLETE mediastinum).
📚 DETAILED DESCRIPTION:
THE LUNGS — ORGANS OF GAS EXCHANGE
The lungs are spongy, elastic organs that fill most of the thoracic cavity. They are the place where oxygen enters the blood and carbon dioxide leaves it.
SHAPE & GENERAL: Each lung is roughly cone-shaped: pointed cranial end (apex), flat dorsal back (base towards diaphragm). The right lung is larger because the heart sits more to the left.
SURFACES of each lung:
• Costal surface: Convex; faces the rib cage.
• Mediastinal surface: Concave/flat; faces the heart and other midline structures. Has the hilus (root) — the entry point for bronchus, pulmonary artery, pulmonary veins, bronchial vessels, nerves and lymphatics.
• Diaphragmatic surface: Hollow surface fitting against the dome of diaphragm.
LOBES OF THE OX LUNG (very important):
The cardiac notch on the cranial border separates the cranial lobe into 2 'parts'.
Right lung — 5 lobes:
1. Cranial lobe — split into cranial part (supplied by the special tracheal bronchus) and caudal part.
2. Middle lobe.
3. Caudal lobe (largest).
4. Accessory lobe (small medial lobe between the heart and diaphragm, fits into the plica venae cavae).
Left lung — usually 2 lobes (or 3 by some counts):
1. Cranial lobe — split into a small cranial part and a larger caudal part.
2. Caudal lobe.
(NO middle lobe on the left — the heart is in its place.)
BOVINE LUNG IS HEAVILY LOBULATED: The surface looks like a tile floor because of distinct interlobular connective tissue dividing the lung into small visible lobules. Same in pig. In horse and dog, the surface is smooth — lobules are not visible from outside.
BRONCHIAL TREE (in brief): Trachea → 2 principal bronchi → lobar bronchi → segmental bronchi → bronchioles → terminal bronchioles → respiratory bronchioles → alveolar ducts → ALVEOLI (the actual gas exchange sites).
BLOOD SUPPLY (dual):
• Pulmonary circulation: Pulmonary artery from right ventricle carries DEOXYGENATED blood to lungs for gas exchange. Pulmonary veins return OXYGENATED blood to left atrium.
• Bronchial circulation: Small bronchial arteries (from bronchoesophageal artery in ox) supply oxygenated blood to the lung tissue itself (the airway walls).
NERVE SUPPLY: Pulmonary plexus around the hilus, formed by vagal (constrict bronchi) and sympathetic (dilate bronchi) fibres.
// COMPARATIVE ANALYSIS
| HORSE |
Right lung 4 lobes (Cranial, Middle joined with Cranial, Caudal, Accessory). Left lung 2 lobes. Lobation NOT prominent — surface smooth. NO tracheal bronchus. |
| DOG |
Most lobulated arrangement clinically. Right: 4 lobes (Cranial, Middle, Caudal, Accessory). Left: 2 lobes (Cranial — split into cranial & caudal parts, and Caudal). Surface smooth. NO tracheal bronchus. |
| PIG |
Like ox — heavily lobulated surface; HAS tracheal bronchus. |
| FOWL |
Lungs are SMALL, FIXED to the ribs (don't expand). NOT lobed. Connected to a system of 9 air sacs that push air through lungs in one direction. Birds breathe with rib movement only — no diaphragm. |
CLINICAL RELEVANCE
Pneumonia in calves (right cranial lobe): Most cases involve the cranial part of the right cranial lobe — because the tracheal bronchus is short and wide, inhaled material drops directly into it.
Auscultation of lungs: Listen over lateral chest wall in the triangle behind the elbow up to about the 11th rib dorsally. Crackles = fluid; wheezes = airway narrowing.
