Past exam questions

Question 1

Explain the difference between the thoracic cavity, pleural sacs and pleural cavity

Answer 1

The thoracic cavity is space enclosed caudally by diaphragm, laterally by internal thoracic wall, and dorsally by vertebrae. The thoracic cavity is lined by parietal pleura which forms the 2 pleural sacs, which join medially to form the mediastinum. The pleural sacs enclose the pleural cavity which contains the lungs

Question 2

In “roarers”, degeneration of the left recurrent laryngeal nerve leads to horses making a roaring sound during exercise. Briefly describe how degeneration of this nerve leads to this sound being produced. Make sure you mention important muscles, cartilages and other structures that may be involved in the process

Answer 2

L recurrent laryngeal nerve innervates muscles of L side of the larynx, including the dorsal cricoarytenoid muscle, the transverse arytenoid muscle, the lateral cricoarytenoid muscle and the thyroarytenoid muscle. The dorsal cricoarytenoid is only muscle that abducts vocal folds, unlike the rest of the muscles which adduct the vocal folds (or are classed as adductors). So when there is L recurrent laryngeal hemiplegia, L vocal fold cant be abducted as the muscle is paralysed, and L vocal fold remains in the larynx and flaps around as air rushes past it during exercise, creating a roaring sound.

Question 3

Briefly describe the blood/gas barrier in the lungs

Answer 3

blood gas barrier is area of gas exchange between alveoli and capillaries in the lungs. The capillaries carry deoxygenated blood to alveoli, and exchange the CO2 in blood for O2 which oxygenates blood that is carried out to circulation. The capillary wall has endothelial cells and a basal lamina. The alvelolar wall has type 1 cells. For gas exchange to occur, the gas must travel the short distance through all of these layers of the blood gas barrier.

Question 4

Briefly describe the changes that occur when a persistent right aortic arch is formed

Answer 4

Persistent R aortic arch occurs when R 4th arch develops into aorta instead of L 4th arch, and the L 4h arch forms the ductus arteriosis. The connection with the ductus arteriosis forms a constricting band across the oesophagus which leads to megaoesophagus

Question 5

Describe the differences in the bronchial drainage between a pig and a horse

Answer 5

In the horse, all bronchial blood drains via pulmonary vein to enter L atrium, while in pig some of bronchial blood drains back via pulmonary vein and enters the L atrium, while the rest drains into the bronchial veins and then into the azygous vein

Question 6

Describe the Retia mirabilia

Answer 6

Retia mirabilia are major blood vessels that abruptly split into several parallel vessels which may or may not reunite. They are important for concurrent heat exchange, reducing arterial pulse P, and allowing transfer of molecules between the arterial and venous circulation. An example is the glomerulus of the kidney

Question 7

Describe the Arteries arising from the aortic arch in the pig

Answer 7

brachiocephalic trunk arises from aortic arch, as does L subclavian artery. The brachiocephalic trunk becomes the bicarotid trunk (off which branches the 2 common carotids) and the R subclavian artery

Question 8

Describe the position of the sinoatrial node (SA node) in the heart

Answer 8

Located in the R atrial myocardium near junction of cranial vena cava. Innervated by the R vagal nerve and the sympathetic cardiac nerve fibres

Question 9

Briefly describe what is occurring during each phase of the cardiac cycle including which valves are open and closed

Answer 9

During phase 1 there is rapid ventricular filling and atrial contraction. The SL valves are shut but the AV valve is open, the ventricle fills passively and the atrium contracts to top up the ventricle. IN phase 2 (isovolumetric contraction) there is the start of ventricular systole. AV valve closes vue to ventricular contraction and the SL valves are closed. Ventricular pressure rises until ventricular P is greater than aortic P, so the SL valve opens. In phase 3 there is outflow of blood from the L ventricle to the aorta, the ventricular P drops and when the ventricular P is lower than the aortic P, the SL valve closes. In phase 4 there is isovolumetric relaxation and the start of ventricular diastole, and the AV valve and aortic valve are both shut. Pressure in the L ventricle decreases

Question 10

List TWO (2) effects that sympathetic nervous system activation has on the cardiovascular system in order to increase cardiac output?

Answer 10

Sympathetic input causes increased Ca and Na permeability which increases contractility and heart rate (increases SA node discharge), and it causes vasoconstriction

Question 11

The following ECG was obtained from a 10-year-old mixed breed dog with a history of collapsing episodes. Determine the heart rate, describe the trace and indicate whether you think the rhythm is normal or abnormal. What is your diagnosis for this patient?

Answer 11

HR= 40 bpm. This is low, I would consider this bradycardia. This is abnormal, I would say its a 3rd degree heart block and the periodic syncope also is consistent with presentation of 3rd degree

Question 12

What are the TWO (2) main determinants of blood flow through a blood vessel?

Answer 12

Blood viscosity, resistance of the vessel, P gradient along the vessel, pressure of blood flow. Probably the BP and the vascular resistance are the most important ones

Question 13

The mean arterial pressure is NOT the arithmetic mean of the systolic and diastolic blood pressures, why is this?

Answer 13

This is because more time is spent in diastole then systole

Question 14

Briefly describe the forces that determine fluid movement between the capillary lumen and the interstitial space?

Answer 14

Hydrostatic pressure → pushes fluid out
Osmotic pressure → draws fluid in due to proteins no readily diffusing (responsible for colloid oncotic pressure)
Endothelial permeability

Question 15

List and briefly describe the layers of the pericardium

Answer 15

The heart and origins of the major blood vessels are covered by the pericardium, a close-fitting serous membrane. It consists of two layers, an inner visceral pericardium attached directly to the surface of the heart and an outer parietal (fibrous) pericardium which is anchored to the base of the great vessels.
The visceral pericardium is also known as the epicardium and consists of a layer of mesothelial cells which secrete pericardial fluid. The parietal pericardium consists of an inner squamous mesothelium, a collagen and elastic fibrous layer and an outer mediastinal . It gives rise to the ligamentous fold that anchors the heart to its position in the thorax (sternopericardial ligament or phrenicopericardial ligament). The visceral and parietal pericardium are separated by the pericardial cavity which contains pericardial fluid

Question 16

Briefly describe two (2) major changes that occur in the foetal circulation at birth

Answer 16

A rise in left atrial pressure and fall in right atrial pressure causes septum 1 and septum 2 to be pushed tightly together forming a complete interatrial septum and preventing the flow of blood from the right atrium to the left atrium through the foramen ovale. This leaves a membranous fossa ovalis in the mature heart.
Closure of the ductus arteriosus also occurs soon after birth so that the lungs receive an adequate flow of deoxygenated blood from the pulmonary trunk. The first breath at birth increases oxygenated blood in the ductus. The proliferating connective tissue eventually closes permanently forming the ligamentum arteriosum.
The umbilical arteries and veins are also constricted at birth, leaving remnant ligaments within the bladder and liver

Question 17

Briefly describe the Terminal crest

Answer 17

An embryonic remnant of tissue ventral to the entrance of the cranial vena cava which has no functional significance

Question 18

Briefly describe the Endocardium

Answer 18

Innermost layer of the heart consisting of polygonal endothelial cells on a basement membrane supported by a subendothelial coat of fine collagenous and elastic fibres. This merges with a deeper subendocardial

Question 19

Briefly describe the Tunica media

Answer 19

The middle layer in the histological section of blood vessels. Consists of a mixture of smooth muscle cells, collagen and elastic fibres and fibroblasts. In large vessels the nervi vasorum and vasa vasorum are found in this layer

Question 20

Briefly describe the Arteriolar-venous anastomosis

Answer 20

Allows blood to pass directly from an arteriole to a venule, bypassing the capillary bed and are present in tissues which vary in activity. Important in thermoregulation of structures such as rabbit ear, dog tongue, horse hoof

Question 21

briefly describe the anatomy of the trachea. Include the

microanatomy of the mucosa etc

Answer 21

Trachea is a non-collapsible tube which is continuous with the cricoid cartilage of the larynx
It is in 2 parts the cervical (which is in the neck) and the thoracic (which is in the thoracic cavity)
It is made of incomplete C shaped hyaline cartilaginous rings which are connected by fibro-elastic annular ligaments
The dorsal surface is free and is covered by the trachealis muscle
Mucosa:
Lined with pseudostratified columnar ciliated epithelium with goblet cells
Lamina propria thin and fibrous and the deeper layers have seromucous glands
The recurrent laryngeal nerve carries parasympathetic fibres which stimulate secretions
Submucosa- Rich in elastic fibres
Musculo Cartilaginous layer- made of hyaline cartilage, fibroelastic fibres and the trachealis muscle
Adventitia- made of loose areolar connective tissue

Question 22

Briefly describe the cartilages of the larynx of the dog and how they articulate with each other.

Answer 22

There are 4 main cartilages of the larynx; the epiglottis (elastic cartilage that forms the entrance to the larynx), the thyroid cartilage (forms a deep trough that is open dorsally, consists of 2 lamina and a body), cricoid cartilage (forms a full ring), and the paired arytenoid cartilages which have 4 main processes: the muscular process (for muscle attachment), vocal process (for vocal lig attachment), corniculate process and cuneiform process. There are 3 main articulations: the cricoarytenoid articulation (between cricoid and arytenoid cartilage), cricothyroid articulation (between the cricoid and thyroid cartilage), and the thyrohyoid articulation (between the thyroid and hyoid apparatus).

Question 23

Explain why and how the anatomy of the nasal cavity changes (or conditions) the nature of inspired air.

Answer 23

The air contains dust, bacteria etc. which is trapped in mucous and filtered by the action of the cilia of the pseudostratified columnar ciliated respiratory epithelium. The cilia sweeps the particles out of the nasal cavity. The air is warmed as it passes over the erectile venous plexuses in the submucosa, and this assists in thermoregulation and maintaining humidity, as warm air holds more moisture. The air is humidified to prevent drying out of the thin film of moisture that surrounds the alveoli, and is also used in olfaction where it is assisted by bowmans glands and nasal glands secretions (as odiferous molecules must be in solution to be detected).

Question 24

State briefly how the autonomic nervous system (ANS) responds to general hypoxia

Answer 24

When the peripheral chemoreceptors detect reduced blood o2 levels, there is release of catecholamines by the sympathetic NS which cause increased contractility, peripheral vasoconstriction, and tachycardia which aims to bring more o2 to the tissues

Question 25

Would you expect the V/Q to be lower or higher than normal in a patient with an airway obstruction?

Answer 25

Low V/Q occurs when ventilation is reduced (comparison- a high V/Q occurs when pulmonary blood flow is reduced)

Question 26

A decrease in blood pH will cause the oxygen dissociation curve to shift to the right.

(a) Will this cause more or less oxygen unloading at the tissue level?
(b) Would you expect carbon dioxide loading to increase or decrease at the tissue level?

Answer 26

a - More oxygen unloading; decreased Hb affinity for O2

b - increase of carbon dioxide loading

Question 27

(a) Which heart valves are closed during systole?
(b) Which heart valves are closed during diastole?
(c) When in the cardiac cycle would you be able to auscultate a murmur caused by an aortic valve regurgitation (insufficiency)? During systole or diastole?

Answer 27

a - Bicuspid/mitral & tricuspid Mitral & Tricuspid
b - Semi-lunar/pulmonic & aortic Pulmonic & Aortic
c - Diastole

Question 28

The process that will stop (arrest) bleeding is called

This process consists of three steps; name these

Answer 28

= Haemostasis

Vasoconstriction- narrowing of blood vessels via smooth muscle contraction
Platelet plug formation- platelets are fragments of a megakaryocyte and a heap of platelets come together to form a plug over the damaged endothelium and blocks the blood vessel
Coagulation- a complicated process of clotting, key steps are fibrinogen being converted to fibrin, which forms the clot

Question 29

The process that will stop (arrest) bleeding is called

This process consists of three steps; name these

Answer 29

= Haemostasis

Vasoconstriction- narrowing of blood vessels via smooth muscle contraction
Platelet plug formation- platelets are fragments of a megakaryocyte and a heap of platelets come together to form a plug over the damaged endothelium and blocks the blood vessel
Coagulation- a complicated process of clotting, key steps are fibrinogen being converted to fibrin, which forms the clot

Question 30

briefly describe the diaphragm

Answer 30

The diaphragm is the most important muscle involved in respiration and it is unpaired broad muscle
It forms the partition between the thoracic and abdominal cavity
It is made of 3 parts according to its attachments:
Lumbar part- this is the doral attachment and holds the crura which is the attachment to the lumbar vertebrae (the right crura is larger than the left)
Costal part- this is the lateral attachment and attached to the ribs or their
Sternal part- this is the ventral attachment and attaches just cranially to the xiphoid cartilage
There are 3 foramina in the diaphragm:
Aortic hiatus- most dorsal and is between the crura. It carried the aorta, right azygous vein and the cistern chyli
Oesophageal hiatus- in the muscular periphery and is dorsal and near the junction of the tendinous centre. Contains the oesophagus, vagus nerve trunks and the esophageal vessels
Caval foramen- is in the tendinous centre and towards the right and carried the caudal vena cava

Question 31

If the transmural pressure gradient was absent, what would you expect happen to the lungs and briefly state why?

Answer 31

If there was no transmural pressure gradient i.e. if the lungs weren’t ‘stuck on’ to the l sacs, then the lung would not be able to expand and therefore air would not be able to bet in. This is because without the transmural pressure gradient, the diaphragm and thoracic cage wouldn’t be able to contract and therefore expand the lungs resulting in there being no negative pressure created inside the lungs which would normally allow the air to be sucked inside

Question 32

If the airway was obstructed due to a disease (e.g. asthma), what would you expect to happen to your measure of expiratory reserve volume (ERV)?

Answer 32

Expiratory reserve volume (the max volume of air which can be expired in addition to tidal breathing) would decrease. This is because dynamic small airways closure occurs early, therefore trapping more air in the lungs and decreasing the volume of air that can be breathed out on expiration

Question 33

What are the major differences in the heart of a dog and the heart of a pig?

Answer 33

In a dog the right AV valve is bicuspid, where as in the pig it is tricuspid
In a dog the heart lies between the 3-6 intercostal spaces, whereas in the pig it lies between the 2-5 intercostal spaces
in a pig there is more fat associated with the heart
Dog has an ovoid shaped heart whereas the pig has a more pointed apex
In a dog the fibrous trigone is cartilaginous, whereas in a pig it is made of dense connective tissue
Dog has phrenicopericardial ligament whereas the pig has a sternopericardial ligament connecting the heart to the thorax

Question 34

Write brief notes on the following:

(a) Cardiac pump for venous return

Answer 34

Venous return is aided by 3 pumps:
Muscular pump- blood is moved by the action of locomotory muscles moving
Respiratory pump- blood is moves by the negative pressure in the thorax
Cardiac pump- a low positive blood pressure (approx 15mmhG) in the great veins aids blood returning to the heart

Question 35

briefly describe the structure of a large bronchus

Answer 35

The mucous membrane is in longitudinal folds
Epithelium- pseudostratified columnar ciliated with goblet cells
Lamina propria- made of loose connective tissue, has capillary network and has smooth muscle
Submucosa- elastic fibres, blood vessels, and seromucous bronchial glands
fibroelastic/cartilaginous layer- made out of cartilage connected by dense elastic tissue

Question 36

What is the plica venae cavae and what two structures does it contain?

Answer 36

Plica venae cavae are located between the accessory and caudal lobes of the R lung, and they are found in the caudal mediastinum. They contain the R phrenic nn and the caudal vena cava

Question 37

Give any example of a situation where the VD might increase

Answer 37

Obstruction in bronchioles, mucus in airways or the alveoli

Question 38

briefly describe the histological structure of a conducting artery

Answer 38

Conducting arteries are large arteries with a wide lumen and carry large volumes of blood around the body (ie. aorta)
Tunica intima- all elements present (endothelium, subendothelial layer and internal elastic lamina)
Tunina media- predominantly has elastic fibres
Tunica adventitia- no external elastic lamina and blends with surrounding tissue

Question 39

Describe the structures of the heart that may be passed by a red blood cell as it passes between pulmonary vein and the aorta

Answer 39

Pulmonary veins
Left atrium
Pectinate muscles + left auricle
Inter-atrial septum 
Mitral valve (left atrioventricular valve) + cusps 
Papillary muscles
Chordae tendineae
Left ventricle
Trabeculae carnae
Trabeculae septomarginalis
Ventricular septum
Aortic valve
Aorta

Question 40

Draw a labelled diagram showing the structure of typical respiratory mucosa

Answer 40

Respiratory mucosa has pseudostratified columnar ciliated epithelium with goblet cells, in the paranasal sinuses the epithelium may be more cuboidal/squamous and contain fewer goblet cells than in the nasal cavity proper. The lamina propria and submucosa consists of loose connective tissue blending with periosteum/perichondrium, and contains leukocytes and deep erectile venous plexuses. Also simple branched tubuloacinar mixed nasal glands

Question 41

Briefly describe the visceral pleura of the dog

Answer 41

The visceral pleura surrounds the lungs inside the pleural cavity. It is made from a serous layer (simple squamous epithelium) and a subserous layer (loose CT with elastic fibres and fat). Serous membranes secrete a serous fluid.

Question 42

List the lobes of the lung of the pig

Answer 42

RIght lung has 4 lobes: cranial , middle, accessory, and caudal; the bronchus supplying the cranial lobe is the tracheal bronchus and branches off the trachea prior to bifurcation. The left lung has 2 lobes: cranial lobe (with caudal and cranial parts), and a caudal lobe.

Question 43

briefly describe the guttural pouch of the horse

Answer 43

They are an extension of the eustachian tube (which connects the middle ear with the nasopharynx), which extends ventrally to occupy the space between the base of the cranium, atlas and pharynx
They are lined by pseudostratified columnar ciliated epithelium with goblet cells which produce a small amount of mucous secretions
The pouch is divided into left and right by the septum and then into lateral and medial pouches. The stylohyoid bones divided them into lateral and media
They are closely associated with the maxillary v., carotid a., cranial nerves and the parotid and submandibular salivary glands
It communicate with the pharynx via the pharyngeal orifice, which drains excess fluid when the horse has its head down

Question 44

List the waveforms that make up a normal cardiac cycle on an electrocardiogram (ECG) trace and name the part of the cardiac cycle that each waveform represents

Answer 44

P wave- atrial depolarisation 
QRS segment- ventricular depolarisation
Q- Early ventricular depol 
R- Ventricular depol 
S- Late ventricular depol 
T- Ventricular repolarisation

Question 45

Describe the relationship between plasma, interstitial fluid and lymph

Answer 45

Plasma is found in capillaries/blood vessels and this will move out of blood vessels into the interstitial space, this is where the fluid is termed interstitial fluid
The interstitial fluid is then moved into lymphatic vessels and is termed lymph