GENERAL CHARACTERISTICS OF RESPIRATORY SYSTEM
primary function |
oxygenate blood, excrete CO2 |
secondary functions |
- olfaction |
- phonation |
- temperature regulation |
|
structural evolution |
→ deny particulate matter |
→ maximize surface area for gas exchange |
→ warm and humidify air |
COMPONENTS MAMMALIAN RESPIRATORY SYSTEM
conducting component |
- nose, nasal cavity, nasopharynx |
- larynx |
- trachea, bronchi, bronchioles |
|
respiratory component |
- respiratory bronchioles |
- alveolar ducts and alveolar sacs |
- alveoli |
|
pumping mechanism |
- diagram |
- rib cage |
- neurological control |
conducting component - NOSE
consists of |
- external nose |
- nasal cavities |
- paranasal sinuses |
supported by bone and cartilage |
lined by mucous membrane |
nose - EXTERNAL NOSE
specific to each species |
affected by |
- shape of supporting lateral nasal cartilages |
- skin type around nose |
supported by lateral nasal cartilages |
- dorsal and ventral |
- may have accessory cartilage |
- extensions of nasal septum |
nose - EXTERNAL NOSE
dog, cat, sheep, goat |
- cartilage complete laterally |
- thick, hairless skin or planum nasale confined to area around nostrils |
- well-defined philtrum |
|
pig |
- cartilage complete laterally |
- extra support by rostral bone medially |
- planum rostrale continuous with upper lip |
- small philtrum |
|
ox |
- cartilage complete laterally |
- planum nasolabiale continuous with upper lip |
- no philtrum |
|
horse |
- small cartilage laterally |
- extra alar cartilage supports dorsal, ventral, medial |
- nothing laterally → nostrils can stretch |
- horse must breath by nose |
- normal skin around nostrils |
nose - EXTERNAL NOSE
provide moisture for nose |
in ruminant and pig - glands in planum |
in carnivores (no gland in planum) |
- lateral nasal glands |
- glands in septum |
- lachrymal glands |
NASAL CAVITY
nasal septum |
perpendicular plate |
- caudal |
- continuous with cribriform plate (both ethmoid bone) |
cartilaginous nasal septum |
- rostral |
- supported by vomer |
have nasal conchae (turbinate bones) |
- thin complex, bony scrolls projecting from inside of lateral wall |
- types: dorsal, (middle), ventral, ethmoidal |
nasal cavity - NASAL CONCHAE
dorsal nasal concha |
- enlongated, sightly curled scroll |
ventral nasal concha |
- tightly folded series of scrolls |
- more extensive than dorsal nasal concha |
|
mucosal folds |
- rostral to conchae |
- straight fold is rostral extension of dorsal concha |
- alar fold is rostral extension of ventral concha |
bulbous enlargement - divert air and increase evaporation |
supported by alar cartilage in horse |
|
ethmoidal conchae |
- series of folding plates |
- caudal part of nasal cavity |
- linked with ethmoid bone |
- extend up into frontal sinuses |
nasal cavity - NASAL MEATUSES
spaces between roof and floor nasal cavity, and dorsal and ventral conchae |
3 meatuses |
- dorsal nasal meatus |
- middle nasal meatus |
- ventral nasal meatus |
in horse, common meatus between conchae and septum
nasal cavity - ASSOCIATED STRUCTURES
INCISIVE DUCTS (nasopalatine duct) |
- paired |
- connect oral and nasal cavities |
- nasal opening - floor nasal cavity at canine level |
- oral opening - incisive papilla - caudal to upper central incisors |
|
VOMERONASAL ORGAN |
- paired blind sacs run caudally from incisive ducts to level P 2-4 |
- cartilage support |
function of ducts |
- epithelium both respiratory and olfactory |
- pheromones and flehmen |
- taste and smell |
|
LATERAL NASAL GLAND |
- serous gland, microscopic (not exist in ox) |
- near nasomaxillary opening; duct opens into middle meatus near end straight fold |
- humidify inhaled air; may aid function for vomeronasal organ |
- humidify nose |
- thermoregulatory support |
|
NASOLACRIMAL DUCT |
- from medial canthus eye into nasal cavity |
- drains eye to prevent weeping; humidify nose and nasal cavity |
- often blocked brachiocephalic breeds |
in horse - no oral opening
nose - PARANASAL SINUSES
GENERAL CHARACTERISTICS |
- air-filled spaces inside bones connected to nasal cavity |
- lined by mucoperiosteum |
- named after bones where they lie |
|
FUNCTIONS |
- lighten skull |
- insulate nervous centers |
- protect eyes, nasal passages and cranial cavity |
- absorb shock |
- amplify voice |
- increase area olfactory membrane |
|
CLASSIFICATION |
- all species: frontal and maxillary sinuses |
- vary in size, shape and other sinuses |
- openings into nasal cavity narrow |
→ blocked by mucosal swelling |
→ prevent drainage |
paranasal sinuses
MAXILLARY SINUS |
- largest |
- communicate with middle meatus via nasomaxillary opening |
- some species have diverticula into |
• hard palate – palatine sinus |
• sphenoid bone – sphenoid sinus |
• medial aspect orbit – lacrimal sinus |
• nasal conchae – conchal sinus |
|
FRONTAL SINUS |
- opens into ethmoidal meatus (horse - opens into caudal maxillary sinus) |
paranasal sinuses - SPECIES
conducting component - NASAL CAVITY - microanatomy
both 2 regions have different mucosae |
RESPIRATORY REGION |
- paranasal sinuses |
- part of dorsal, all ventral conchae |
- lateral, dorsal, ventral nasal wall and part of septum |
OLFACTORY REGION |
- ethmoturbinates |
- part of dorsal conchae |
- part of nasal septum |
- vomeronasal organ |
nasal cavity - RESPIRATORY MUCOSA
EPITHELIUM |
- ciliated pseudostratified columnar with goblet cells |
- in paranasal sinuses - more cuboidal to squamous, less glands and goblet cells |
LAMINA PROPRIA and SUBMUCOSA |
- loose connective tissue blends with periosteum, perichondrium |
- leukocytes (eosinophils and lymphocytes) |
- simple branched tubuloacinar mixed nasal glands (less in sinuses) |
- erectile venous plexuses with sphincters |
nasal cavity - OLFACTORY MUCOSA
EPITHELIUM |
- yellowish pigmentation |
- 3 cell types |
sensory (olfactory) cells - bipolar neurons, thickness, long, non-motile cilia |
sustentacular (supporting) cells - slender, many microvilli (no cilia) |
basal cells - spherical |
nasal cavity - FUNCTIONS
olfactory |
respiratory |
- filter (dust, bacteria) |
- adjust temperature and humidity |
conducting component - NASOPHARYNX
- air from nasal cavity to nasopharynx via choanae (internal nares) |
- choanae separated by vomer and dorsal to palatine bone (hard palate) |
- connected to middle ear by audiotory (Eustachian) tube |
cartilaginous through open ventrally |
keep middle air at surrounding pressure |
horse: massive paired evagination ventrally, the gutteral pouches
conducting component - LARYNX
- short musculo-cartilaginous tube (a bunch of articulating cartilages held together by muscles, ligaments and membranes) |
- connects nasopharynx with trachea |
- supported by hyoid apparatus |
larynx - HYOID APPARATUS
pair bones |
- thyrohyoid bone (articulate with thyroid cartilage) |
- basihyoid (unpaired, lie transversely) |
- keratohyoid bone |
- epihyoid bone |
- stylohyoid bone |
- tympanohyoid cartilage |
larynx - FUNCTION
respiration |
- maintain air pathway |
- regulate airflow to lungs |
deglutition |
- prevent aspiration of food, saliva, etc. |
support olfaction - direct air through nasal passage |
intrathoracic pressure regulation - act as a valve |
phonation - vocal folds |
larynx - CARTILAGES
many articulating cartilages with ligaments and muscles |
4 main cartilages and 1 minor |
- epiglottis (elastic cartilage) |
- thyroid (hyaline cartilage, 2 lamina and central body, open dorsally) |
- cricoid (hyaline cartilage, complete ring) |
- arytenoids (paired, hyaline cartilage) |
• muscular process - lateral, crest shaped |
• cuneiform process - elastic cartilage, part of epiglottis in horse, absent pig and ruminants (= wedge shaped) |
• corniculate process - elastic cartilage, horn shaped, dorsal |
• vocal process - attachment vocal ligaments |
- interarytenoid (hyaline cartilage, carnivores and pigs) |
larynx - ARTICULATIONS
3 articulations |
- cricothyroid - simple rotation around transverse axis |
- cricoarytenoid |
• rotation around transverse and sagittal axes |
• slide to bring arytenoids closer or further |
- thyrohyoid - simple transverse axis |
larynx - LIGAMENTS
7 ligaments (intrinsic and extrinsic) |
- cricothyroid |
- cricotracheal |
- vocal |
- transverse arytenoid |
- thyroepiglottic |
- hyoepiglottic |
- vestibular |
larynx - WALL OF THE LARYNX
PAIRED MUCOSAL FOLDS |
vestibular fold |
- from arytenoid to epiglottis |
- enclose cuneiform process, vestibular ligament and ventricular muscle |
- absent in ruminants |
vocal fold |
- from vocal process of arytenoid to body thyroid |
- more medial than vestibular fold and encloses vocal ligament |
- glottis have space between them |
aryepiglottic fold |
- lateral margin of epiglottis to arytenoid (dog and horse) |
- lateral margin of epiglottis to cricoid (cat) |
- lies dorsal to arytenoid and cricoid (pig and ruminant) |
- forms boundary of laryngeal entrance |
|
LATERAL VENTRICLE (SACCULE) |
- deep blind-ending pocket lateral wall larynx |
- only in dog, pig, horse |
- entrance between vocal and vestibular folds (between split vocal ligament in pig) |
|
(MEDIAN VENTRICLE) - pig, horse; base epiglottis |
|
LARYNGEAL MUCOSA |
- stratified squamous epithelium - rostral to vocal folds |
- pseudostratified columnar ciliated epithelium caudally |
larynx - ARTICULATIONS
4 sections |
ADITUS LARYNGIS |
- entrance |
- aryepiglotic fold, epiglottis, corniculate process |
VESTIBULE |
- from aditus to vocal folds |
- vestibular folds and lateral ventricle |
RIMA GLOTTIDIS |
- vocal folds and vocal process |
INFRAGLOTTIC CAVITY |
- continuous with trachea |
larynx - MUSCLES
INTRINSIC MUSCLES |
- control movement of cartilages relative to each other |
- close or open glottis by abducting or adducting vocal folds |
- all attach to processes of arytenoids and rotate them to tension vocal folds (except for cricothyroid muscle) |
|
Abductors - open glottis |
dorsal cricoarytenoid muscle |
- dorsal cricoid to muscular process of arytenoid |
- abduct ventral edge arytenoid, draw vocal fold ventrally |
|
Abductors - close glottis |
cricothyroid muscle |
- from lat surface cricoid to lat surface thyroid |
- draw thyroid and cricoid closer → tense vocal folds without abduction |
lateral cricoarytenoid muscle |
- from lateral rostral border cricoid to muscular process of arytenoid |
- draw vent edge arytenoid ventrally and medially, adducting vocal cords |
transverse arytenoid muscle |
- from muscular process of arytenoid, passes dorsally to other arytenoid |
- fine tunes other muscles |
thyroarytenoid muscle |
- from epiglottis and thyroid (internal midline) to muscular process arytenoid |
- in dog and horse, divided into ventricularis rostrally and vocalis caudally |
- caudal part associate with vocal ligament to form basis vocal fold |
- adduct arytenoids |
larynx - MUSCLES
EXTRINSIC MUSCLES |
- control movement of larynx relative to whole body |
- connect with hyoid bones, pharynx, sternum |
|
move larynx rostrally |
- thyrohyoid muscle |
• origin: hyoid apparatus |
• insertion: thyroid cartilage |
- hyoepiglottic muscle |
• origin: hyoid apparatus |
• insertion: epiglottis |
- geniohyoid muscle (with stylohyoid, mylohyoid, stylopharyngeus, palatopharyngeus) |
• not attach directly to larynx |
• anchor hyoid apparatus rostrally |
- rostral movement - important in swallowing (deglutition) |
|
move larynx caudally |
- **sternothyroid muscle (with sternohyoid; omohyoid in horses) |
- important in strenuous exercise |
larynx - INNERVATION
2 nerves, both branches of vagus nerve |
cranial laryngeal nerve |
- external cranial laryngeal nerve (motor to cricothyroid muscle) |
- internal cranial laryngeal nerve |
caudal laryngeal nerve (recurrent larygeal nerve) |
- motor to all intrinsic muscles (except cricothyroid) |
- different paths in LnR sides |
|
damage/degenerate left recurrent laryngeal nerve |
→ left laryngeal paralysis |
- problem for dorsal cricoarytenoid muscle (only abductor) |
→ can't abduct left vocal cord during exercise → |
→ make noise or 'roaring' |
- graded and surgical correction |
• ‘tie-back’ operation (prosthetic larygoplasty) |
• nerve grafting using omohyoideus |
• lateral ventriculectomy reduces roaring sound |
larynx - BLOOD SUPPLY
2 arteries |
cranial thyroid artery |
- from common carotid artery |
cranial larygeal artery |
- either from common carotid artery or external carotid artery |
conducting component - TRACHEA
from larynx to principal bronchi |
non-collapsible, supported by cartilage |
2 parts |
cervical |
- two third of esophagus (upper part) located dorsal to trachea, one third of esophagus (lower part) shifts to left side caudal |
- go along with many nerves and vessels |
thoracic |
- dorsal to cranial vena cava |
- divide into 2 branches to base heart at 4th-6th inter costal space |
trachea - STRUCTURE
tracheal cartilages |
- hyaline |
- C-shape, open dorsally |
annular ligaments |
- fibro- elastic connections between cartilages |
trachealis muscle |
- dorsal aspect (gap in rings) |
- smooth |
- external to ring carnivores; internal others |
trachea - MICROANATOMY
mucosa |
- pseudostratified columnar ciliated epithelium with goblet cells |
- lamina propria of loose, vascular connective tissue |
- longitudinal folds |
submucosa |
- seromucous tracheal glands |
musculo-cartilaginous layer |
adventitia |
trachea - ROLE
rigid tube for air passes through (can collapse cause pathology) |
flexible and extensible |
- flexible cartilage; incomplete cartilage rings |
- longitudinal mucosa fold; elastic tissue in submucosa |
trap and remove fine particles |
RESPIRATORY COMPONENT
lungs |
pleura - thin membrane corver lungs and lining thoracic cavity |
in thoracic cavity |
- thoracic inlet |
- thoracic wall |
- diaphragm |
different to thoracic cage
respiratory component - PLEURA
serous membrane |
- serous layer |
• simple squamous epithelium |
• thin lamina propria |
serous fluid/exudate |
- lubrication |
lines thoracic cavity, form pleural sacs (R > L) |
- come together medially, form mẹdiastinum |
- push medially, bound by connective tissue |
- contain trachea, oesophagus, heart, vessels, etc. |
pleural cavity in each sac |
|
lungs bud from trachea, push out into pleura → enveloped by pulmonary visceral pleura |
form walls of pleural sacs (parietal pleura) |
- costal pleura |
- diaphragmatic pleura |
- mediastinal pleura |
lungs expand to fill pleural cavities |
pleural space |
- narrow space between visceral pleura and parietal pleura |
- contains pleural fluid |
visceral pleura - cover lungs
parietal pleura - line pleural cavity
pleura - FUNCTION PLEURAL SPACE AND FLUID
make lungs stick to inside of thoracic cavity |
- slight vacuum in pleural space |
- inborn surface tension of fluid |
seal → avoid thoracic wall movement during lung expansion |
lubrication for lung movement against inside thoracic wall |
pleura - MEDIASTINUM
partition |
- 2 serous membranes |
- connective tissue |
contains all thoracic structures (except lungs, caudal vena cava and right phrenic nerve) |
3 parts |
- cranial mediastinum (pre-cardiac) |
- middle mediastinum (cardiac) |
- caudal mediastinum (post-cardiac) |
|
|
conducting component - NASAL CAVITY - microanatomy
both 2 regions have different mucosae |
RESPIRATORY REGION |
- part of dorsal, all ventral conchae |
conducting component - NASAL CAVITY - microanatomy
|