Cardiovascular system Flashcards
How is the thorax bound laterally?
The ribcage
How is the thorax bounded dorsally and ventrally?
Bound dorsally by the spine, and ventrally by the sternum
How is the thorax bound cranially and caudally?
Bound cranially by the thoracic inlet and caudally by the diaphragm
What is the difference between the parietal pleura and the visceral pleura?
The visceral pleura lies on the surface of the lung and then folds back out from the root of the lungs to make the parietal pleura. The parietal pleura is made up of the diaphragmatic pleura, the costal pleura on the ribs and the mediastinal pleural around the midline.
Describe where the lungs sit in the thorax
Dorsal and cranial to the heart
Describe the lobes of the lungs
The left and right lung are split up into lobes, which can then be further split into lobules (differences of species).
The left lung has a cranial and caudal lobe.
The right lung has 4 lobes- cranial, caudal, middle and accessory.
Horses lack the middle lobe.
How can pig lungs be diffferentiated?
Less notable lobes of the lungs, surface appears marbled.
How does the heart sit in the thorax?
Ventrally to the lungs, between the left and right lobes.
The base of the heart sits cranially and dorsally to the apex.
Sits on the midline of the thorax, with the apex tilted slightly towards the left.
What is the sternum made up from? What is the name of the first and last sternebrae?
Sternum is made of 8 sternebrae.
The first sternebrae is the manubrium
The last sternebrae is the xyphoid process
What is the pericardium?
An invaginated sac of the serous membrane surrounding the heart.
What three layers made up the heart wall?
Inner layer- endocardium
Muscular layer- myocardium
Outer layer- epicardium
Describe the route blood takes through the heart
Deoxygenated blood enters the right atrium through the vena cava.
Blood passed into the right ventricle through the right atrioventricular valves.
Pumped out of the heart, through the semilunar calves, into the pulmonary artery.
Oxygenated blood enters the left atrium through the pulmonary vein.
Blood passes through the left atrioventricular valve into the left ventricle.
Blood is pumped at a high pressure through the semilunar valves and into the aorta.
Describe the structure of the atrioventricular valves
Tricuspid on the right, mitral on the left.
Valves are made of fibrous cusps.
The cusp is held in place by the cordae tendineae, which are connected to the papillary muscles and then the ventricle wall.
Define systole and diastole
Systole is contraction, diastole is relaxation. Chambers fill during diastole, and are emptied during systole.
What are the normal heart sounds, and what are they caused by?
S1 (lub)- AV valves shut, so blood rebounds in ventricles
S2 (dub)- SL valves shut, blood in vessels slow
Define the three abnormal heart sounds and their causes
S3 (gallops)- turbulence in left ventricle NORMAL IN HORSES
S4 (gallops)- stiff ventricular wall causing increased atrial contraction (to push the blood in) NORMAL IN HORSES
Murmurs- generated by turbulence in the blood flow
Outline the basic electrical pathway through the heart
Impulse generated by SAN in right atrial wall
Impulse travels across atria, causing atrial contraction
Impulse passes through AVN in the distal interatrial septum (AVN is only electrical conduction between atria and ventricles, as separated by annulus fibrosis)
AVN conducts slowly to allow the atria contraction time
Impulse travels from AVN down the Bundle of His, which branches off left and right into purkinje fibres to supply the ventricular muscles.
Describe the structure of the semilunar valves
Made of 3 semilunar shaped cusps, thicker towards the middle for contact areas
How do pressure changes impact valves? What happens to the valves during: Isovolumic relaxation Diastole Isovolumic contraction Systole
Pressure differences make valves open or close.
Isovolumic relaxation- ventricle pressure falls below atrial pressure, so AV valve opens
Diastole- ventricle fills and pressure rises so AV valve closes
Isovolumic contraction- pressure in ventricle rises above that of the artery, so SL valve opens
Systole- ventricle empties, so lower pressure than artery and so SL valve closes
What arteries are found nearest to the heart? What features do they have?
Large elastic arteries
Able to withstand the high pressure from the heart as able to stretch and recoil