The Respiratory System

ANSC 309

what is the function of the respiratory system?

to move inspired air containing oxygen along the respiratory passages to the areas where gaseous exchange takes place and to move expired air containing carbon dioxide out of the body

what is the name for the areas where gaseous exchange takes place?

alveoli

what structures does the respiratory system consist of?

• nose and naval cavity

• pharynx

  • nasopharynx

• larynx

• trachea

• lungs

  • primary (mainstem) bronchi

  • lobar bronchi

  • bronchioles

  • alveoli

the nose comprises the:

• external nose

• nasal cavities (paired)

• paranasal sinuses (paired)

what are different factors of the nose that differ between certain species?

form and size of nostrils, their orientation. and the nature of the surrounding integument 

what is another name for nostrils?

nares

what are nares?

hairless and well demarcated from the skin of the face (with exception of the horse)

plate/planum

the region of skin around the nares

why is the plate moist to the touch?

because of the secretions of the underlying glands

the nasal plate of the dog and cat is divided by a median groove called the…

philtrum

depending on the species, the naming for the piece of skin around the ______ is different.

nares

what is the skin around the nares called in carnivores and small ruminants?

nasal plate/planum nasale

what is the piece of skin around the nares in cattle called?

nasolabial plate/planum nasolabiale

what is the piece of skin around the nares called in pigs?

rostral plate

horses have a blind sac of the nose called _______ _________

nasal diverticulum

what is the main function of nasal cartilage?

to support and shape the external nose

what is the function of alar cartilage?

(attached to the free edges of the septum) support the dorsal and lateral margins, and determine the form of the opening of the nostrils

what creates the right and left nasal cavities?

the rostral part of the nasal septum

the skin of the external nose meets with the _____ ________ in the ______ ________ at a sharply defined line

nasal mucosa; nasal vestibule

at the sharply defined line, in what animal is the orifice of the nasolacrimal duct on the vestibule floor?

horse

the sharply defined line opening is less easily found in other species. list 2 reasons why?

• because the tissues are less pliant (cattle)

• because it is placed more deeply (dog)

list the functions of the nasal cavity

• warms the air passing over the highly vascular mucosa

• humidifies the air by the vapors of tears and serous nasal secretions

• cleans the air of particles by interacting with the mucus

describe the makeup of the nasal septum

largely cartilaginous but is ossified in its most caudal part

conchae

on either side of the nasal septum and are scroll-like bones

what are the names of the spaces surrounding the dorsal and ventral conchae?

• dorsal meatus

• middle meatus

• ventral meatus

• common meatus

the ventral and common meatuses provide the principle airway leading to the ________

pharynx

what is the clinical relevance of the ventral and common meatuses leading to the pharynx?

a nasogastric tube passes through the wide space at the junction of the ventral and common meatuses

the paranasal sinuses are the ________ of the nasal cavoty

diverticula

how are paranasal sinuses developed?

postnatally by the separation of inner and outer tables of the skull bones

all species have what 2 sinus systems?

frontal and maxillary sinus systems

what structure forms the connection between the pharynx and the trachea?

larynx (it lies below the pharynx and behind the mouth)

what are the major, consistently present cartilages of the larynx?

• epiglottic cartilage

• thyroid cartilage

• cricoid cartilage

• arytenoid cartilages (paired)

what laryngeal cartilage is most rostral and covers the entrance of the larynx when the animal swallows?

epiglottic cartilage

describe the appearance of epiglottic cartilage

consists of a small stalk and a large leaflike blade

what laryngeal cartilage is the largest?

thyroid cartilage

what does thyroid cartilage consist of?

two lateral plates that fuse to a varying degree ventrally and form a major part of the laryngeal floor

describe the appearance of the cricoid cartilage

it is fashioned like a signet ring, consisting of an expanded dorsal “seal” and a narrower ventral arch

describe the appearance of arytenoid cartilage

paired and have a very irregular form best described as pyramidal

what is used to intubate an animal through the larynx?

endotracheal tube

steps of intubating with an endotracheal tube

• use laryngoscope

• use sterile lubricant

• avoid inserting too far (entering the carina or mainstem bronchi)

what two structures form a continuous system of tubes conducting air between the larynx and the smaller passages in the lungs?

trachea and bronchi

together, the trachea and bronchi are sometimes termed…

tracheobronchial tree

describe the location of the trachea

the trachea leads from the larynx through the neck, enters the mediastinum at the thoracic inlet, and continues to its terminal bifurcation dorsal to the heart

where does the bifurcation lie?

in the region of the fourth to sixth intercostal spaces

the two mainstem bronchi diverge from the ….. to quickly enter the corresponding lungs at their roots

line of the trachea

carina

the tracheal bifurcation which divides the left and right mainstem bronchi

in what animal(s) is there a separate tracheal bronchus that arises proximal to the tracheal bifurcation to enter the cranial lobe of the right lung?

in ruminants and pigs

what is the wall of the trachea composed of?

• inner mucosa

• middle cartilaginous layer

• outer adventitia (in the neck) or serosa (in the thorax)

in the trachea, the cartilaginous coat is composed of numerous strips of cartilage that are bent to form ________, that are incomplete dorsally

rings

what is the function of the cartilage rings?

to help prevent collapse of the trachea

what are the edges of the strips of the tracheal cartilaginous rings connected to each other by?

sheets of rather elastic connective tissue

the smooth tracheal muscle bridges the gap within the ring in most species, but is placed externally in what anima

collapsing trachea

a relatively common disorder of the trachea resulting from weakened cartilage of the tracheal rings in canines

common clinical signs of collapsing trachea?

• persistent, dry, harsh cough (goose honk)

• cough may worsen with excitement, with pressure on the trachea, such as from a collar, during hot or humid weather, or immediately after eating or drinking

the structure of the larger bronchi is identical to that of the ________

trachea

with further divisions of the bronchi, the cartilage rings are gradually replaced by irregular plaques, and they finally disappear to mark the transition into __________

bronchioles

pleura

serous membranes that cover the lungs and line the walls of the thorax

the pleura forms the left and right sacs that enclose the …

pleural cavities (each consist of visceral and parietal parts, depending on their location)

mediastinum

the median partition in the thorax within which the heart and other thoracic organs are situated (space between the right and left sacs)

visceral/pulmonary plura

the part of the pleura that clothes the lung directly

the pulmonary pleura is reflected around, and behind, the root of the lung to become continuous with the ________ _______

mediastinal plura

the mediastinal pleura is continuous with the ______ and _________ pleura

costal and diaphragmatic

the mediastinal, costal, and diaphragmatic pleura together are called the …

parietal pleura

the right and left lungs are enclosed into their respective pleural sacs and are free except at the _______

roots

what are the roots of the lungs attached to?

the mediastinum

what do lungs do when squeezed and when placed in water? why?

crepitate (make a crackling sound) when squeezed

float when placed in water

they do this because of their soft, spongy texture, and they have residual air in them, even when collapsed

which lung is always larger?

right lung

what are the features of each lung?

• an apex toward the thoracic inlet

• a wide, concave base facing the diaphragm

• a convex costal surface fitted against the lateral chest wall

• the ventral part is indented over the heart (cardiac notch)

how is the root of the lung formed?

by the bunching together of the mainstem bronchus and the pulmonary artery, veins, lymphatics, and nerve

where does the root of the lung sit comparatively to the heart?

sits dorsal to the heart

what is the clinical relevance of the heart being directly beneath the bronchi?

cardiomegaly — enlarged heart compresses the trachea and bronchi against the dorsal thoracic wall resulting in coughing

what are the lobes of the left lung?

• cranial lobe

  • cranial part

  • caudal part

• caudal lobe

what are the lobes of the right lung?

• cranial lobe

• middle lobe

  • horse lacks middle lobe

• caudal lobe

• accessory lobe

in most species one or more ________ extend into the substance toward the root, dividing each lung into parts

fissures

when are fissure lines clinically relevant?

when assessing the chest cavity for pleural fluid in the thoracic cavity

what is the identification of lungs of individual species most conveniently based on?

the degrees of lobation and lobulation

describe the degree of lobation in horses

show almost no lobation and very inconspicuous lobulation externally

describe the degree of lobation in ruminants and pigs

conspicuously lobated and lobulated

describe the degree of lobation in carnivores

very deeply fissured into lobes but show little external evidence of lobulation

bronchiole

narrow — less than 1 mm in diameter — and pass through several generations

where do the bronchioles terminate at?

alveoli

(true/false) the alveoli is the only place where gaseous exchange takes place

true

how is carbon dioxide formed in the body before expired?

formed by the tissues during metabolism