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Flashcards in Respiratory System Deck (109):

What is the main stimulus for erythropoiesis?



What are the sources of erythropoietin?

In adults, it is primarily the kidney (to a lesser degree the liver). In the foetus, it is the liver


What is the sequence of development of erythrocytes from a pluripotent stem cell? How long does this process take and at which point does mitotic division stop**?

Pluripotent stem cell ➡️ myeloid stem cell ➡️ rubriblast ➡️ prorubricyte ➡️ rubricyte ➡️ metarubricyte** ➡️ reticulocyte ➡️ erythrocyte

3-5 days


On a blood smear, what are some signs of regenerative or non-regenerative anaemia?

Regenerative: reticulocytosis, polychromasia, macrocytosis, anisocytosis, hypochromasia, increased Howell-jolly bodies, increased nRBCs, basophilic stippling esp. in ruminants (hyperchromic megacytic anaemia)

Non-regenerative: no reticulocytosis, minimal polychromasia (normocytic normochromic or hypochromic microcytic anaemia)


How do we assess for regenerative anaemia?

1. Reticulocytosis (most accurate)
2. Blood smear (polychromasia)
3. Macrocytosis and hypochromasia
4. Bone marrow evaluation (erythroid hyperplasia)
5. Serial monitoring of PCV/CBC to assess improvement (in horses)


What do the following terms mean?

1. Polychromasia
2. Macrocytosis
3. Anisocytosis
4. Hypochromasia

1. Presence of blue-tinted RBCs
2. Large immature RBCs
3. Varied RBC size
4. Low haemoglobin concentration


What are the two forms of reticulocytes in cats?

Aggregate (0.4% in health; 1% in dogs)
punctate (10%) -take longer to mature


How may we assess the degree of regeneration?

Absolute reticulocyte count (reticulocyte % x RBC count)

Corrected reticulocyte % (reticulocyte % x (patient Hct/ average species Hct))


What is the normal absolute reticulocyte count range?
What is the average species corrected reticulocyte percentage?

0-120 x 10^9/L

>1% in dogs and >0.4% in cats


What is the MCV, MCHC and RDW?

MCV= mean corpuscular volume
MCHC= mean corpuscular haemoglobin concentration
RDW= red cell distribution width


What are the responses to acute haemorrhage at the following stages:

Acute stage I (within hrs)
Acute stage II (3-5 days)

Peracute: no change in Hct or protein (hypovolaemia)

Acute I: decreased Hct and protein (blood dilution), activation of RAAS

Acute II: EPO produced and marrow stimulation, evidence of regeneration in blood, Hct and protein start to rise if haemorrhage controlled


Ghost cells are signs of ....?
Spherocytes are signs of...?

Intravascular haemolysis

Extravascular haemolysis


What are the stage I and stage II responses to acute haemolysis?

Stage I:
🔹Decreased Hct and normal protein
🔹No evidence of regen
🔹+/- haemolysed plasma and haemoglobinuria

Stage II:
🔹EPO produced
🔹Evidence of regen.
🔹+/- haemolysed plasma and haemoglobinuria
🔹Hyperbilirubinuria/ jaundice
🔹Hct starts to rise


What are some causes of intravascular haemolytic anaemia?

🔹Oxidative injury
🔹Zinc toxicosis
🔹Copper toxicosis
🔹Genetic disease


What are some causes of extravascular haemolytic anaemia?

🔹Infections (RBC parasites)
🔹Oxidative damage
🔹Genetic disease


What are the main functions of the respiratory system?

🔹Gas exchange
🔹Temperature control
🔹Acid-base regulation


The upper respiratory tract is comprised of....? The lower respiratory tract is comprised of....?

-external nose
-nasal vestibule
-paired nasal cavities
-paranasal sinuses
🔹Nasopharynx (with associated auditory tubes)
🔹Proximal trachea ( to level of thoracic inlet)


Dolicocephalic refers to.....? Mesaticephalic refers to....?

Long nose
Medium-length nose


The external nose varies between species. Describe.

Carnivores, small ruminants= nasal plate
Ox= nasolabial plate
Pig= rostral plate
Horse= no modified epithelium


How are nasal plates in dogs, ox and pigs are kept moist?

Ox, pig: underlying glands
Dog: overflow from nasal cavity


The external nose has a nasal plate in ______, a nasolabial plate in _______ and a rostral plate in ________.

Carnivores and small ruminants


What is the nasal vestibule? How does it differ in horses?

A narrow passage from the nostril to the wider nasal cavity. The mucocutaneous junction within the vestibule is the site of opening of lateral nasal gland ducts (and the nasolacrimal duct in the horse).

In the horse, the vestibule is divided into a ventral (true nostril) and dorsal part (nasal diverticulum).


Nasal cavity:
What separates it from the oral cavity?
What limits it caudally?
It is divided into small passages by...?
How does it communicate with nasopharynx?

Hard palate
Ethmoid bone
Conchae (turbinate bones)


What is the alar cartilage?

Cartilage on lateral wing of nostril


The nasal conchae are also called nasal turbinate bones. There are three including...? Their main function is what?

1. Dorsal= single elongated scroll
2. Ventral= rostral part of nasal cavity= double scroll in most species (single in 🐴)
3. Ethmoidal= numerous fine scrolls attached to ethmoid bone and lateral and dorsal walls (supports olfactory mucosa)

Function is to increase SA for heat exchange, filtration, humidification and olfaction


The lateral nasal gland is only present in _____ and opens in the ?lateral/medial? Wall of nasal vestibule. The nasolacrimal duct has a distal opening in the nasal vestibule at the _______ in the 🐴 and _________ in the 🐶

Carnivores, lateral

Mucocutaneous junction

Ventral to alar fold


What are the functions of the paranasal sinuses?

🔹Lighten skull while allowing bony development
🔹Thermal and mechanical protection of soft tissues
🔹Resonance of voice


The frontal sinuses drain...?
The maxillary sinuses house the roots of the upper cheek teeth and communicate with the nasal cavity through...?

Ethmoid region (except in horse) and extend into corneal process in ruminants

Narrow nasomaxillary opening (except in 🐶🐱 where it is a wide opening called the maxillary recess)


In 🐴, the maxillary sinus is...?
The frontal sinus extends into the ______ and drains into the caudal ________. All sinuses drain into nasal cavity through narrow common nasomaxillary opening.

Divided into rostral and caudal sections.

Dorsal conchae (which is closed off from nasal cavity)

Caudal maxillary sinus


In the 🐴, what are the important landmarks to remember when wanting to gain surgical entry to the sinuses?

🔹Nasolacrimal duct (medial canthus to nasoincisive notch) - TO BE AVOIDED

1. Infraorbital foramen --> medial can thus
2. Facial crest
3. Infraorbital foramen --> rostral border of facial crest
4. Vertical line through medial canthus of eye


Birds have no soft palate and therefore no nasopharynx. True or false?

True! They instead have an elongated medial choana that closes during swallowing


What is the function of the nasal gland in birds?
The infraorbital sinus is a diverticulum enclosed by what?

Sodium secretion in marine birds.

Caudal concha


What is the function of the auditory (or eustachian) tubes?
They lead from the middle ear cavity to open where?

They allow equalisation of pressure between the middle ear cavity and the external environment.

Open into the lateral wall of the nasopharynx.


What is special about the auditory tubes in horses? Describe.

They have an out-pocketing called the guttural pouches. They are situated medial to the mandible (dorsally between skull and atlas; ventrally between pharynx and proximal oesophagus).


The guttural pouches are paired structures which meet in the midline ventrally. What muscle separates them dorsally?

What structure partially divides the pouches into lateral and medial compartments?

What nerves/vessels are closely associated with the guttural pouches?

Rectus capitis ventralis

Stylohyoid bone

Facial (CNVII), glossopharyngeal (CNIX), vagal (CNX), accessory (CNXI) and hypoglossal (CNXII) nerves. Also the sympathetic trunk, the internal carotid artery and the retropharyngeal lymph nodes.


Where do the guttural pouches drain?

Into the nasopharynx via the auditory tubes.


What are the boundaries of Viborg's triangle?

Caudal border of mandible
Sternocephalicus tendon
Linguofacial vein


What are the bones and cartilages of the hyoid apparatus?

🔹Tympanohyoid cartilage
🔹Stylohyoid bone
🔹Epihyoid bone
🔹Ceratohyoid bone
🔹Basihyoid bone (with lingual extension in the horse)
🔹Thyrohyoid bone


What are the laryngeal cartilages (from most rostral to caudal)?

Epiglottis, thyroid, arytenoid and cricoid


What muscle comprises the vocal fold?

Vocalis muscle


What are the extrinsic (4) and intrinsic (5) muscles of the larynx?

🔹Pharyngeal constrictors

🔹Cricoarytenoideus dorsalis
🔹Cricoarytenoideus lateralis
🔹Arytenoideus transversus


Describe the innervation of the larynx.

1. Vagus nerve
-sensory to larynx
-motor to INTRINSIC muscles

2. Cranial laryngeal nerve
-sensory to mucosa cranial to vocal folds
-motor to cricothyroideus

3. Caudal laryngeal nerve (from recurrent laryngeal n.)
-sensory to mucosa caudal to vocal folds
-motor to all INTRINSIC muscles (except cricothyroideus)


The larynx in birds is not used for vocalisation. It occupies the (1)___________ on the floor of the pharynx and is supported by the cricoid and (2)__________ cartilages (but no (3)_______). The bird also has no vocal folds.

1. Laryngeal mound
2. Arytenoid
3. Epiglottis


The trachea bifurcated at the level of which vertebrae?

Its cartilage rings are composed of what type of cartilage?

4-5th thoracic vertebrae


What is the smooth involuntary muscle forming the roof of the trachea? How does this differ among species?

What is the carina?

Trachealis muscle. Attaches on the lumen surface in horses and ox but on the outer surface in dogs.

Carina is the cartilaginous ridge at the tracheal bifurcation


What is the sequence of airway branching from the trachea?
What is a bronchopulmonary segment and a pulmonary acinar?

Trachea ➡️ principal bronchus ➡️ lobar (secondary bronchus) ➡️ segmental (tertiary) bronchus ➡️ small bronchus ➡️ bronchioles ➡️ terminal bronchiole ➡️ respiratory bronchiole (with alveoli) ➡️ alveolar duct ➡️ alveolar sacs

BP segment= segmental bronchus and the lung tissue it ventilates
Pulmonary acinus= resp bronchioles and the lung tissue it ventilates


The lower airways develop as an outgrowth from the _____1________ forming a _______2_________. In sheep, this occurs on embryonic day ___3____

Embryonic foregut
Laryngotracheal groove
Day 17


What are some examples of congenital defects that may occur during airway development?

1. Tracheo-oesophageal fistulas (failure of separation of caudal laryngotracheal groove from foregut)

2. Tracheal hypoplasia (abnormal narrowing of trachea due to defect in growth of cartilages)

3. Accessory lungs


How does the trachea differ in birds? What side of the neck is it palpable on? Where does it bifurcate?

It has complete overlapping cartilaginous rings. Palpable on the right side. Bifurcated dorsal to the base of the heart


What is the syrinx? Where is it located? What is the pessulus?

Vocal organ of the bird located at the bifurcation of the trachea. The bronchial openings of the syrinx are separated by vertical wedge-shaped cartilage called the pessulus.


Describe the bronchi in birds 🐦(4 main points)

🔹2 principal bronchi
🔹Secondary bronchi (40-50) branch off through the lung at regular intervals
🔹About 400-500 tertiary bronchi called parabronchi arise from each secondary bronchus. They anastomose with each other.
🔹Loops from walls of parabronchi through lung tissue and back to parabronchi form air capillaries


Avian air sacs are connected by secondary bronchi to the lungs and principal bronchi. They are the space for expansion of respiratory tract. Describe their divisions.

1. Cranial group
-Cervical (unpaired, within/adj to cerv/thor vertebrae)
-Clavicular (unpaired, thoracic inlet, sternum, humeri)
-Cranial (paired, bw stern also ribs, heart and liver)
-Cervicocephalic (strong fliers, over head and neck)
2. Caudal group
-Caudal thoracic (paired, bw body wall and and viscera)
-Abdominal (paired, caudodorsal abd cavity, vertebral and pelvic bones)


What type of epithelium lines the respiratory tract?
What parts of the respiratory tract have goblet cells?
What parts have mucous glands?
What parts have Club cells?
What parts have cartilage?

Trachea --> segmental bronchi = pseudostratified columnar
Bronchiole= columnar/cuboidal
Respiratory bronchiole= cuboidal
🔹Goblet cells
Trachea -->bronchiole
🔹Mucous glands
Trachea, bronchus, segmental bronchi
🔹Club cells
Bronchiole and respiratory bronchiole
Trachea-->segmental bronchi


What region of the nasal cavity will you find the olfactory mucosa?
What cells constitute the olfactory epithelium?

Caudodorsal region

Olfactory cells (cell bodies of olfactory nerve (CNI)),
sustentacular (support) cells,
basal cells (stem cells)


What are brush cells and where are they found in the airways?

Sensory receptors associated with trigeminal nerve. Have thick microvilli.

Found in nasal epithelium


What are the four primary defence mechanisms of the respiratory system?

1. Lumenal epithelium (secretes cytokines and mediators on activation and allows dendritic processes to sample lumen particles)
2. Mucociliary clearance (3 functional compartments incl. unidirectionally beating epithelial cilia, airway surface liquid layer, and protective mucus layer)
3. Specialised small airway defence cells (Club cells)
4. Sneeze/ cough reflex


What class of drugs increase mucociliary clearance?

Beta-2 agonists


What are Club cells?

Non-ciliated secretory bronchiolar epithelial cells with the following functions:
🔹Stem cell
🔹Club cell secretory protein and surfactant-like liquid
🔹Secrete glycosaminoglycans, proteins and part of IgA antibodies
🔹Engulf airborne toxins


How does the sneeze reflex differ from the cough reflex?

1. Irritant receptors in nasal airways (cff. larynx, trachea, pharynx and bronchi)
2. Stimulate trigeminal nerve CN V (cff. vagal afferent nerves)
3. Deep inspiration
4. Brief closure of the glottis
5. Contraction of respiratory muscles
6. Abrupt forced blast of air directed through nasal passages (cff. mouth)


What is the sternopericardial ligament and the plica venae cavae?

Folds of pleura attaching the heart to the sternum

Fold of pleura suspending caudal vena cava


What are the main muscles of ventilation? What is their innervation?

-external intercostal and scalenus (draw ribs cranially and laterally)

-normally passive
-forced expiration is by internal intercostals and abdominal muscles

- diaphragm innervated by phrenic nerve (5th to 5th cervical nerves)
- intercostal nerves


What are the steps involved in inspiration and expiration?

Contraction of diaphragm-->expansion of thorax--> drop in pressure in pleural cavity (754mm Hg)-->lung expansion and drop in intra-alveolar pressure--> airflow down pressure gradient into lungs

Relaxation of inspiratory muscles--> decrease in thoracic and lung volume-->increased intra-alveolar pressure--> airflow down pressure gradient out of lungs


What is atelectasis?

Airflow into thorax resulting in loss of partial vacuum and lung collapse


Where does the cardiac notch occur?

At about the 3rd-5th intercostal space


The apex of the lungs lies adjacent to...?
What composes the root of the lung?

Thoracic inlet

Principal bronchus, pulmonary artery, veins and nerves wrapped together in pleural covering (location of the tracheobronchial lymph nodes)


How do we define lung lobes? How many are there in a dog and horse?

Lung lobes are subdivided into lobules also known as .....? The connective tissue septa dividing these lobules differ among species. Explain.

Structures supplied by a secondary (lobar) bronchus.

🐶 2 left, 4 right
🐴 2 left, 3 right

Bronchopulmonary segments.

Thick in ruminants, thin and incomplete in horses, almost non-existent in dogs.


In ruminants and pigs, the cranial lobe of the right lung is ventilated by what?

In what species is the middle lobe not present?

What other lobes comprise the right lung?

Tracheal bronchus


Caudal lobe and accessory lobe


There are two networks of lymphatic drainage in the respiratory system. What are these called and what do they drain?

Superficial network: drains subpleural tissue into vessel at hilus of lung

Deep network: drains deeper tissue via vessels running along airways from level of bronchioles.

Both sets merge at hilus--> tracheobronchial lymph nodes--> cranial mediastinal lymph nodes--> tracheal lymphatic vessels or thoracic duct


Where does the innervation of the lungs arise? What does the efferent and afferent supply control?

From the pulmonary plexus within the mediastinum.

Efferent: regulates activity of bronchial glands
Afferent: responsible for reflex coughing and reflex modification of breathing


What are the consequences of local hypoventilation and local hyperventilation?

-increased PCO2--> bronchiole dilation--> increased airflow
-decreased PO2--> hypoxic pulm. vasoconst.--> reduced blood flow

-decreased PCO2--> bronchiole constr.--> decreased airflow
-increased PO2--> vasodilation--> increased blood flow


What are the two cell types comprising the alveoli and how do they differ in structure and function?

Type I: flattened, bm, terminally differentiated, gas diffusion
Type II: cuboidal, cytoplasmic granules w/ surfactant, can divide


What comprises the blood-brain barrier?
How thick is it?

🔹alveolar fluid
🔹type I alveolar epithelial cell
🔹epithelial cell basement membrane (+/- interstitium)
🔹bm of capillary endothelium
🔹capillary endothelial cell

0.2-2 micrometers thick


Pulmonary macrophages can be found where?

-alveolar space


What is the total pressure of atmospheric air? What are the partial pressures of the three main gases?

760 mmHg
O2= 160 mmHg
CO2= 0.3 mmHG
N2= 593 mmHg


How does the partial pressure of O2 and CO2 change along the respiratory tract?

O2: 160-->146-->100-->40
CO2: 0.3-->0.27-->40-->46


What is the formula for the rate of gas diffusion through tissues?

DR= (PD x A x DC) / T

PD= partial pressure gradient across tissue barrier
A= SA available for diffusion
DC= diffusion coefficient
T= thickness of tissue barrier


What happens if your diffusion reserve is exhausted?

Hypoxaemia without hypocapnia


How much O2 is carried via Hb in the blood?



Explain the oxygen-haemoglobin saturation curve.

It illustrates the percentage of Hb bound to oxygen at different blood PO2 pressures. It is a sigmoid curve because the affinity of a particular heme group for oxygen is influenced by oxygenation of other heme groups.


What is the Bohr effect/shift?

A right shift ( and hence decreased oxygen affinity)in the oxygen-Hb saturation curve due to an increase in CO2 tension


What is the Haldane effect?

The increased affinity of reduced Hb for CO2


What are the two reactions CO2 can undergo in the erythrocyte?

1. Join with H2O to form H2CO3 and then HCO3- and H+.
2. Join with Hb to form carbaminohaemoglobin and H+


Briefly explain the difference between respiratory acidosis and alkalosis.

Resp. acidosis: increased PCO2 in the blood
Resp. alkalosis: decreased PCO2 in the blood


If there is a metabolic acidosis/alkalosis, would we expect pH and [HCO3-] to move in the same or opposite direction?

Same direction. They would move in the opposite direction if change was respiratory in origin


There are 5 aggregations of neuronal cell bodies involved in the control of ventilation. Name them and identify where they can be found.

1. Apneustic centre- pons
2. Pneumotaxic centre- pons
3. Dorsal respiratory group- medulla oblongata
4. Ventral respiratory group- medulla oblongata
5. Pre-Bötzinger complex- medulla oblongata


What is the role of the dorsal respiratory group in controlling ventilation. From where does it receive its input?

It stimulates inspiratory spinal motor neurone innervating the diaphragm. It happens in response to pacemaker activity arising in the pre-Bötzinger complex.

It receives input from:
-Pneumotaxic and apneustic centres
-Stretch receptors in smooth muscle of airways
-Mechanoreceptors in airways
-Chemoreceptors (peripheral and central)


What is the role of the apneustic and pneumotaxic centre?

Both fine tune output from medullary centres. Pneumotaxic centre terminates inspiration, apneustic centre prevents the inspiratory neutrons from being switched off.


What is the Hering-Breuer reflex?

The inhibition of firing of inspiratory neurons to prevent over-inflation of lungs.


What are the three classes of bronchodilators? How do they work?

1. B2 adrenoceptor agonists: increase adenylyl cyclise--> increased cAMP--> increased PKA--> inactive MLCK--> bronchodilation

2. Phosphodiesterase inhibitors: prevent breakdown of cAMP to AMP

3. Muscarinic receptor antagonists: prevent parasympathetic bronchoconstriction


How do corticosteroids work?

They bind to a receptor and travel to the nucleus where they downgrade transcription of inflammatory mediators.


Besides bronchodilators and corticosteroids, what are some other drugs used in airway disease?

1. Sodium cromoglycate (anti-inflammatory, mast cell suppressant)
2. Antitussives (cough suppressants, opioids, anti-histamines)
3. Mucolytics/expectorants: decrease viscosity of mucus and increase serous secretion in airways (bromhexine/ bisolvon)


Which of these is NOT a limitation of pulse oximetry? (There may be more than one correct answer).
A. Hypoxaemia
B. Vasoconstriction
C. Sampling difficulty
D. Sensitivity to ambient light
E. Invasive

C and E


How does capnography work? What is the normal CO2 range?

It measured the expired CO2 and plots this against time and thus indicates the adequacy of ventilation.

35-45 mmHg


Explain the normal capnograph shape.

4 phases:
I. Inspiratory baseline
II. Expiratory upstroke
III. Alveolar plateau
0. Inspiratory downstroke


What methods can be used to sample the respiratory system?

Bronchoalveolar lavage
Trans-tracheal wash
Truecut biopsy


With chronic exposure to the cold, how is basal metabolic rate increased?

Via thyroxine and the increased activity of catecholamines on fat.


What is the carotid rete?

Network of anastomosing capillaries formed by the carotid artery and bathed in venous sinus that drains the nasal cavity —> blood cooling


In what ways is heat loss by convection reduced?

Piloerection, increased fur covering, reduced surface area


How many kcal of energy does one litre of water take to become water vapour?



Sweating is under the control of...?

Sympathetic cholinergic nerve fibres


How is panting different from hyperventilating?

Panting is the movement of small tidal volumes over the respiratory dead space. They are only ventilating dead space.


What is the area of the brain that controls and coordinates heat loss and heat preservation?

Anterior hypothalamus


What is hyperthermia and what are the four main types?

Any elevation in core body temperature above the accepted normal range.

1. Fever
2. Heat stroke
3. Exercise induced
4. Malignant


How is fever brought about? (Why?)

Initiated by exogenous pyrogens ➡️ activate endogenous pyrogens ➡️ enter hypothalamus ➡️ endothelial cells produce PGE2 and other arachidonic acid metabolites that reset the body’s set point.

(Why? Increased temp enhances leukocyte activity. Many viruses are heat sensitive)


What is malignant hyperthermia?

Rapid/ relentless progressive increase in body temperature due to disturbed intracellular calcium metabolism


What are the different temperature ranges that classify hypothermia as either primary or secondary?

Primary (secondary):
Mild= 32-37 (36.7-37.7)
Mod= 28-32 (35.5-36.7)
Severe= <28 (33-35.5)
Critical= (<32)


What alterations occur to the cardiovascular system with hypothermia?

Initially: increased HR and BP due to catecholamine release
Then...alpha1receptors lose affinity for noradrenaline—> decreased contractility

Left-shift, hypotension, lower CO

Platelet sequestration in spleen and liver. Platelet aggravation is impaired and the clotting cascade is altered


What alterations to the respiratory system happen with hypothermia?

Decreased CO2 production —> decreased TV and RR


When interpreting a blood gas, what are the normal values for the following?

pH: 7.41
pCO2: 37
SBE: -5 to 1
HCO3: 22

pH: 7.39
pCO2: 31
SBE: -8 to -2
HCO3: 18