FINALS TOPIC 1: Comparative Respiratory Anatomy: Structures, Defenses & Species Differences

What are the segments of the respiratory system?

Upper respiratory tract: nasal cavity, pharynx, larynx, and proximal trachea; remaining trachea, bronchi, bronchioles, and lungs.

What are the systems/divisions of the respiratory tract concerning immune defenses?

Conducting system - nose, trachea, and bronchi

Transitional system - bronchioles

Gas-exchange system - alveoli.

How does the conductive system defend against pathogens?

Mucus traps particles; cilia move mucus toward the pharynx; antibodies, lysozyme, and cytokines contribute.

What is the immune defense of the transitional system?

Club (Clara) cells and their secretions, antioxidants, lysozyme, and antibodies help protect the airway.

How does the gas-exchange system defend against pathogens?

Alveolar macrophages ingest inhaled particles and microbes; surfactant, opsonizing antibodies, and antioxidants assist.

Pulmonary intravascular macrophages help clear bloodborne material in species that have them.

How are particles trapped in the upper and middle respiratory passages?

Mucus traps inhaled particles by allowing them to stick to its surface.

How are trapped particles removed from the upper and middle respiratory passages?

Cilia carry mucus and trapped particles toward the pharynx; sneezing and coughing help clear the airways.

What is the difference between deposited and trapped particles in the respiratory passages?

Deposition is when a particle leaves the airstream and lands on an airway surface; trapping is when the deposited particle sticks to mucus.

What are the dorsal, lateral, and ventral boundaries of the nasal cavity?

Dorsal - nasal bone

Lateral - premaxilla rostrally (incisive bone) and maxilla caudally

Ventral - palatine bone.

What are the rostral and caudal boundaries of the nasal cavity?

Rostral - nostril or external naris; caudal - choanae or posterior nares.

What are the apertures of the pharynx?

Nasopharynx, oropharynx, and laryngopharynx.

What are the meatuses/air spaces in the nasal cavity?

Dorsal meatus, middle meatus, ventral meatus, and common meatus.

What separates the nasal cavity into left and right?

Nasal septum.

What is the common passageway for the digestive and respiratory tracts?

Pharynx.

What is the voicebox?

Larynx - a cartilaginous valve between the pharynx and trachea.

What is the slit-like opening at the proximal aspect of the larynx?

Rima glottidis - the slit between the vocal folds.

What is aspiration pneumonia?

Lung inflammation, often with infection, after foreign material is inhaled.

What is the windpipe?

Trachea - a cartilaginous and membranous tube extending from the larynx.

What are the concentric layers of the trachea?

Five layers: mucous membrane, muscular layer, fibroelastic layer, cartilaginous ring, and fascia propria.

What type of cartilage is found in tracheal rings?

Hyaline cartilage.

What is the “point of tracheal bifurcation?” (Trachea divider)

Carina - the internal ridge where the trachea divides.

What are the branches of the bronchi?

Trachea → right and left primary bronchi → secondary bronchi → tertiary bronchi → bronchioles → alveoli.

What is diffusion in the context of respiration?

Passive movement down a gradient across the air-blood barrier.

O2 moves from alveolar air into blood and CO2 moves from blood into alveolar air, each down its partial-pressure gradient

What is phonation?

Voice production as expelled air sets the vocal folds vibrating.

What is olfaction?

Sense of smell.

What are the chemoreceptive cells of the nasal epithelium?

Olfactory receptor neurons of the olfactory epithelium.

What is the olfactory nerve?

Cranial nerve I (CN I) formed by axons of olfactory receptor neurons form the ___ and reach the olfactory bulb

What are the pointed and wide portions of the lungs?

Apex - pointed portion

Base - broad portion facing the diaphragm.

What are the borders of the lungs?

Dorsal border faces the thoracic vertebrae

Ventral border faces the sternum.

What is the extra lobe of the right lung?

Accessory (intermediate) lobe.

What are the lobes of the right lung?

Four-lobe pattern: cranial (apical), middle (cardiac), caudal (diaphragmatic), and accessory (intermediate).

What are the lobes of the left lung?

Cranial and caudal lobes.

What are the parts of the cranial lobe?

Cranial and caudal parts; older naming describes these as apical and cardiac.

What surfaces of the lung face the ribs?

Costal surface.

What surface of the lung faces the mediastinum?

Mediastinal surface.

What surface of the lung lies between lobes?

Interlobar surface.

What surface of the lung faces the diaphragm?

Diaphragmatic surface.

What is the diaphragm?

A broad, unpaired respiratory muscle that separates the thoracic and abdominal cavities.

What are the parts of the diaphragm?

Pars costalis – attaches to ribs and costal cartilages.

Pars sternalis – at the xiphoid region.

Pars lumbalis – forms the right and left crura

lecture levels are right L1–L5 and left L1–L2 (species variation applies).

What is the caval foramen?

Hiatus venae cavae.

What structures pass through the aortic hiatus?

Aorta, azygos vein, and lymphatic passage at the cisterna chyli-thoracic duct connection.

What structures pass through the esophageal hiatus?

Esophagus, vagal trunks, and esophageal branch of the gastric artery.

What are the regions of the mediastinum?

Precardial – cranial to the heart.

Cardial – at heart level.

Postcardial – caudal to the heart.

What structures pass through the mediastinum?

Trachea, esophagus, major vessels, aorta, azygos vein, thoracic duct, phrenic, vagus, sympathetic, recurrent laryngeal, cardiac and pulmonary nerves, thymus, and lymph nodes.

What is the mediastinum?

The central thoracic compartment between the right and left pleural sacs.

What is the serous lining of the thorax?

Pleura.

What is the serous lining of the abdomen?

Peritoneum.

What regulates air volume in respiration?

Larynx.

What prevents aspiration of foreign bodies?

the epiglottis (larynx) helps cover the laryngeal entrance during swallowing.

What are the paired laryngeal cartilages?

Arytenoid, corniculate, and cuneiform.

What are the unpaired laryngeal cartilages?

Epiglottic, cricoid, and thyroid.

The entrance to the larynx, bounded in front by epiglottis, behind by arytenoids, and laterally by ary-epiglottic folds.

aditus laryngis

Bounded laterally by ventricular folds, and has a lateral ventricle which leads into the laryngeal saccule.

vestibule of the larynx

What part of the larynx is continuous with the trachea?

Posterior compartment.

What are the extrinsic muscles of the larynx?

Sternothyrohyoid, thyrohyoid, and hyoepiglottic.

Which laryngeal muscle tenses the vocal cords?

Cricothyroid.

Which laryngeal muscle dilates the rima?

Dorsal cricoarytenoid.

Which laryngeal muscle closes the rima?

Lateral cricoarytenoid.

Which laryngeal muscle assists in closing the rima?

Transverse arytenoid.

Which laryngeal muscle closes the rima and loosens the vocal cord?

Vocal muscle (vocalis).

What structures enter/leave the lungs at the hilus?

Bronchus, pulmonary artery and veins, bronchial artery, pulmonary nerves, and lymphatic vessels.

What are the types of lungs based on development of secondary lobules?

Type 1 (well developed), Type 2 (poorly demarcated or absent), Type 3 (incompletely developed).

What are the characteristics of a fetal lung?

Unaerated, smaller, pale gray, firm, and noncrepitant.

What are the characteristics of a normal lung?

Aerated, pink, soft, spongy, and crepitant.

What are the characteristics of lungs in cattle, ox, sheep, pig, and dog?

Cattle/ox and sheep – deep interlobar fissures, distinct lobation, and a tracheal bronchus supplying the right cranial lobe.

Pig – similar pattern; left cranial parts separated by a shallow cardiac notch, distinct fissure marks off caudal lobe, and a tracheal bronchus is present.

Dog – four right lobes, very deep fissures extending toward the root, and subdivided left cranial lobe.

What are the lines of reflections of the parietal pleura?

Vertebral reflection – near vertebrae, costal pleura turns ventrally to become mediastinal pleura.

Sternal reflection – near sternum, costal pleura turns dorsally to become mediastinal pleura.

Diaphragmatic reflection – parietal pleura reflects onto the diaphragm.