Trachea-branches into to main bronchi at Tracheal bifurcation (Carina)

Bronchial Tree-airways from bronchi to alveoli

Bronchi>Bronchioles>Alveolar Duct>Alveolor Sac (collection of alveoli)

Smooth muscle surrounds passageways Sympathetic tone-

◦ Bronchial smooth muscle relaxes=Bronchodilation

Parasympathetic tone-◦ Partial smooth muscle contraction

=Bronchoconstriction

External Respiration occurs here◦ Where is internal respiration???◦ Exchange of oxygen and carbon

dioxide between air in lungs and blood

Thin- walled sacs-simple squamous epithelium

surrounded by capillaries- simple squamous epithelium

Lined with Surfactant-thin fluid layer◦ Helps reduce surface tension of the fluid

Surface Tension-attraction of water to each other◦ Helps prevent alveoli from collapsing◦ Premature infants

Irritants can cause bronchoconstriction Asthma patients can become overly

sensitive to irritants Cats-

◦ Mild-wheezing, coughing◦ Severe-dyspnea (difficulty breathing), cyanosis

(bluish gum color)◦ Treatment-bronchodiliators, anti-inflammatory

agents

Asthma Cat

Aerocat inhalers

2 Lungs◦ Apex-Cranial thorax◦ Base-Caudal thorax

Lies on the cranial surface of diaphragm◦ Lateral surface-against thorax wall◦ Space between lungs-mediastinum

Contains: Heart, large blood

vessels Nerves Trachea Esophagus Lymphatic vessels

and lymph nodes

Divided into lobes◦ Defined by major branches of bronchi-not grooves

on the outside◦ Cat, cow, dog, goat, pig, sheep:◦ Left lobe

Cranial and Caudal◦ Right lobe

Cranial, middle, caudal and accessory lobe◦ Horse-left lung, right lung, accessory lobe

Hilus-medial aspect of lungs◦ Where air, blood, lymph and nerves enter and exit

lungs◦ “Attachment”

Pulmonary (Lung) Circulation Pulmonary Artery-blood enters the lungs

◦ Low Oxygen, high Carbon Dioxide◦ Comes directly from the right side of the heart

Split to left and right pulmonary arteries, then follow bronchi

Pulmonary Capillaries Pulmonary Veins-blood exits the lungs

◦ High Oxygen, Low Carbon Dioxide◦ Returns to the left side of the heart

Nonfunctional No air within lungs until first breath after

birth First breath, surfactant covers alveoli to

prevent collapse Stillborn vs. Neonatal Death???

Dorsal-thoracic vertebrae Lateral-ribs, intercostal mm. Ventral-sternum Pleura-thin membrane, covers organs and

lines thoracic cavity◦ Visceral Pleura◦ Parietal Pleura

Pleural Fluid – lubricates surfaces◦ Smooth sliding during breathing

Caudal-Diaphragm◦ Skeletal muscle◦ Relaxed-Dome shaped◦ Contracted state-flattens

Enlarges thorax Inspiration

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