Cardiovascular system Flashcards
Describe the gross topography of dogs rib structure (13)
- 13 thoracic vertebrae
- Each V articulate with 2 ribs = 13 pairs
- Intercostal muscles between each rib
- Heart sits between ribs 3 and 6
- Dorsal = thorasic spine which is bounded ventrally by sternum
- Dog has 8 sternebra from cranial manubrium to xiphoid process caudal
- Cranial aspect= thoracic inlet, caudal = diaphragm
- Costochondral junction = where bone meets cartilage
- First 9 ribs articulate with sternebra
- ribs 10-12 articulate with one another = costal arch
- rib 13 is floating
Where to the lungs sit in reference to the heart
dorsally and laterally
What is Pleura
Serous membrane that lines everything in the thorax- forms a potential space between 2 layers which contains a negative pressure which holds the lung against the diaphragm and chest wall
What are the different types of pleura?
- Visceral pleura- serous membrane that lines the surface of lungs = inner membrane of cavity
- Parietal pleura- lines everything else: diaphragmatic, costal lines ribs,
- Mediastinal pleura = lines chest cavity in area between the lungs
What does the mediastinum contain?
Middle of thorax have everything in in except from lungs. space between both lungs in thoracic cavity, defined on either side by mediastinal pleura- heart is within mediastinum
What is the pericardium
Membrane that surrounds heart = an invaginated sac of serous membrane containing the heart:
- visceral pericardium = on heart wall = indistinguishable
- Parietal pericardium = bag around heart
Name the different valves in the and describe positions
- AV valves inbetween atria and ventricles - LHS = mitral valve RHS = tricuspid
- Semilunar valves. LHS = aortic. RHS = pulmonic
What are the sounds “lup” and “dup” referring to?
lup = START OF SYSTOLE. AV close (tricuspid and mitral), blood rebounds within ventrucles and accelarates within aorta
2. Dup = END OF SYSTOLE semilunar valves (aortic and pulmonic) close and blood decelerates in blood vessels
How many ribs does a normal dog have
13 pairs
What is the name of the most caudal sternabra
Xiphoid Process
What is the manubrium
the most cranial sternebra
What is the costochondral junction
Between bone and cartilage of rib
What are the layers of the heart?
- inner endocardium
- Myocardium
- Outer Epicardium
A dog presents with signs of heart failure and muffled heart sounds. A cardiac ultrasound shows fluid collecting in the sac around the heart. What is the outer layer of this sac referred to as?
Parietal Pericardium
In order to drain fluid from the pleural cavity, a drain must be advanced through the skin and muscle of the body wall and which membrane?
Parietal pleura.
parietal = not on organ, specifically costal pleura
Bacteria in the bloodstream travelling through the heart from a dental infection may colonise the heart valves causing serious disease. Which layer is infected first?
Endocardium - most inside
This initiates the normal cardiac impulse.
Sinoatrial node
Blockage of this would delay conduction of the impulse only to the left ventricle.
AND which could delay to ventricles
a) left bundle branch
b) bundle of his, AVN and left bundle branch
Damage to the proximal interventricular septum could damage this part of the pathway.
proximal = top = bundle of his
Describe the electrical pathway of AP in heart
Sinoatrial node (RA) generates impulses. Atria contract. Impulses pause at non-conducting tissue (anulous fibrosis surrounding valves) and AV node (interatrial septum close to tricuspid valve). Allows ventricles to fill. AP travels down Bundle of His to apex. AP travels through purkinje fibres, ventricles contract upwards.
What is the function of valves?
ensure blood flows in the correct direction: close to prevent backflow
What are the valves in the heart supported by?
Annulus fibrosis, a fibrous skeleton which also serves as an electrical insulation between atria and ventricules
presented with a heart murmur that has long gaps between beats is this systolic or diastolic?
Systolic
When listening to the heart what bit is diastolic and what systolic?
Between beats = diastolic
Beats = systolic
Describe route taken by blood through heart adn why?
LA receives O blood from lungs via pulmonary vein, through to LV: atrioventricular (MITRAL) valve. Delivers to rest of body via aorta. RA receives DO blood from rest of body via vena cava, through to RV through right atrioventricular (TRICUSPID) valve. Delivers to lungs via pulm artery.
Left and right separated by interatrial septum, LRV by interventricular septum.
Moves due to pressur changes. valves = no backflow
What is the structure of the Mitral and tricuspid valves
- Mitral = 2 main cusps
- Tri = most species 3 cusps but dogs = 2 main with several small commissural cusps at the free edge
- Muscular projections on the ventricle walls called papillary muscles are attached to chordae tendinae (fibrous muscles) attached to free edge of valve, hold it in place, anchoring to prevent prolapse
- supported by annulus fibrosis whcih also serves as an electrical insulation between atria and ventricles
Structure and function of semilunar valves
- made up of 3 cusps
- supported by annulus fibrosis
- function = prevent arteriol blood flowing back into V during diastole
What does incompetence mean in reference to valves and what does this result in?
- failure to close properly = blood regurgitation as it flows in wrong direction which could lead to congestion and heart failure
What does it mean if valves are stenotic? what could this result in?
narrowed.
Result in blood unable to pass through as easily, leading to increased work on heart and pressure in chambers
What stops AV valves folding back into atria?
becuase of chordae tendinae which anchor free edge of valve- allow to close then tight which stop it from pushing backwards
What would happen if the valve didn’t close?
blood would flow back into atrium = reduced blood output and pressure in atrium increases = backwards heart failure
What is collateral circulation?
When arteries have side branches
What is an inter arterial anastomoses?
joining between arteries
What would happen if there was blockage in an end artery
Lead to infarction and necrosis (death) of the tissue
How can the volume of blood reaching a cap bed vary?
- Pre capillary sphincter zone = pre cap arterioles that contract to decrease blood blow and relax to increase it
- Arteriovenous anastomoses = joining between an artery and vein = bypass capillary bed completely
- Thoroughfare channel = pre cap arteriole sends blood through one cap = minimal exchange
Why do tumours often spread to the lung?
as all blood that goes through lungs must pass through a capillary. Not really any arteriovenus anastomoses in lungs so blood in lungs can’t bypass cap bed so easy for tumour cells to get stuck
Give 4 examples of when we take thoracic radiographs
- Respiratory disease
- Cardiovascular disease
- staging of neoplasia (presence or formation of new, abnormal growth of tissue)
- Trauma
When examining lungs what position do you want the animal and why?
Ventrodorsal - lungs closer to plate therefore more accurately represented in terms of size and shape (further away = more magnified)
When examining heart what position?
Dorsoventral as heart is ventral to the lungs
If want to look at right hand lung what position of animal and why?
Left lateral recumbency as when on LHS left lung will be collapsed