the heart Flashcards
what are the functions of the circulatory system
transport:
- nutrients
- waste
- O2 and CO2
- heat
- hormones
protective - carries WBC and Ig
homeostasis - pH, ions, fluid volume
pressure
describe the different pumps of the circulatory system
Pulmonary circuit (to lungs)
pulmonary artery –> arterioles –> capillaries –> pulmonary veins back to heart
systemic circuit
aorta –> arteries –> arterioles –> capillaries (exchange) –> venules –> systemic veins back to heart
equal volumes go through each circuit
describe the landmarks of the heart
ventral border: ventral border of the lungs//sternum
laterally: lungs (phrenic nerve)
cranially: thymus in young animals
caudally: diaphragm
describe the position of the heart
- lies in the mediastinum
- divides L and R pleural cavities
- 60% is to L of plane (bc left side of heart has greater musculature
- on rads: lateral projection is between ribs 3-6
- base is dorsal
- apex sits in sternum costalchondral junction 6
- right ventrical is CRANIAL to left
describe the structure of the heart
- atria form base (have blind appendages called auricles)
- coronarhy groove sits in main trunks of coronary vein (divides atria from ventricles)
- ventricles have paraconal groove cranially and subsinuosal groove caudally
what does the black arrow indicate
paraconal groove
what do the arrows indicate
what is the pericardium? describe the layers
sac surrounding the heart
inner - visceral layer (surface of heart)
- = epicardium
outer parietal layer
- contiguous with BC adventitial layer
no significant lumen
pericardium has 2 ligaments: sterno-pericardial ligament and phrenico-pericardo ligaments to prevent distension
list the structures found in the right atrium
- cranial and caudal vena cava (intervenous tubercle directs blood down to vena cava
- sino-atrial node
- coronary sinus (where deoxygenated blood from heart enters)
- azygous vein (R or L)
- Fossa ovalis (foramen ovale) = withing the wall of right atrium, connects L and R atria in fetus in order to shunt blood away from lungs, residual in adults, not functional
describe the position of the left atrium
- dorsal and caudal
- under tracheal bifurcation
- pulmonary veins enter (in groups of 2 or 3 sites)
- in septal wall is scar tissue of valve of foramen ovale (leftover from fetal circ. system)
describe the structure of the right ventricle
- crescentric in section (wraps around left ventricle)wraps around left ventricle cranial and to the right
- pulmonary artery is cranial and left of aorta
- there is a band of muscle running across right ventricle called trabecula septomarginalis –> will see on U/S as circular/linear structure, dont mistake for mass
describe the structure of the left ventricle
- circular in section
- occupies all of apex (only ventricle that goes all the way down to tip of apex, trace to find which side is which)
- prominent papillary muscles
- aorta in central
- walls are thick
list the cardiac valves and their locations. what control them
- right AV (atrium/ventricle) = tricuspid (only 2 cusps in animals but can be 3 in people)
- Left AV = mitral (2 cusps)
ventricular to artery:
- right semilunar = pulmonic (from right ventricle to pulonary artery)
- left semilunar (left ventricle to aorta)
- each have 3 cusps
- both prevent back flow down into ventricles
what is the function of the coronary artery and where does it branch from
- supplies blood to heart muscle
- branches from aorta
what do A, B, C, D and E indicate
A. when the ventricles have relaxed sufficiently the ventricular pressures become lower than the atrial pressures and the AV valves open. blood then flows passively into the ventricles
B. the atria contract and force more blood into the ventricles
C. the ventricles start to contract causing the ventricular pressures ton increase. the AV vlves then close
D. the pressures within the ventricles increase further and exceed pressure eithin the outgoing arteries. the valves leading to the arteries open and blood flows into the aorta and the pulmonary artery. the content of the heart is thereby halved
E. the ventricles relax and the pressures within them become lower than the in the outgoing arteries. the valves to the arteries then close when the ventricular pressures fall below the atrial pressures, the AV valves open again and a new cardiac cycle begins
describe the fibrous cardiac skeleton
- separates atria and ventricles
- insulation (AV bundle)
- cows can have bones (ossa cordis)
describe the structure of the myocardium
- epicardium –> visceral pericardium = blood vessel adventitial layer
- myocardium - cardiomyocytes
- endocardium (continuous with blood vessel lining)
describe cardiomyocytes
- large cylindrical cells
- striated (myofibrils) like skeletal mm
- short, branched fibres
- lots of mitochondra
- smaller than skeletal muscle
- central nuclei
- have intercalated discs
- excitable cells
- functional electrical syncitium
- structure facilitates fast AP passage (t-tubules and sarcoplasmic reticulum
