The heart Flashcards
Describe the principal functions of a circulatory system and appreciate how the various components of such a system are structured to fulfil these functions
Transport
Nutrient
Waste
O2 and CO2
Heat
Hormones
Protective – carries WBC and Ig
Homeostasis – pH, ions, fluid volume
Pressure
Outline the pulmonary circuit of the dual pump
Deoxy blood leaves the right ventricle into the pulmonary artery
Travels through arterioles and then the capillaries
Oxy blood from the capillaries is then taken back to the left atrium
Outline the systemic circuit of the dual pump
Oxy blood leaves the left ventricle through the aorta
Travels through the arteries then the arterioles and then the capillaries
The deoxy blood is taken to the systemic veins (inc vena cava) by the venules into the right atrium
Outline the blood supply to the liver
Blood first travels through the digestive tract then to the liver through the hepatic portal vein
Outline the blood supply to the kidneys
Afferent arterioles bring blood to glomerulus and then efferent articles leave the glomerulus. After leaving the nephron these efferent arterioles condense to eventually fomr the renal vein
Describe the necessity for a dual circulatory system in the adult mammal
Blood taken to the lungs requires less pressure so that Haemoglobin able to bind to sufficient O2 molecules.
In order to supply sufficient blood to the rest of the body the blood from the LHS has a higher pressure
Describe the anatomical landmarks of the heart
Ventral border of the lungs
Cardiac notch (L>R)
Lungs laterally
Phrenic nerve runs along the heart
Thymus cranially
In young animals
Diaphragm caudally
Describe the postion of the heart
Lies in mediastinum
Divides L and R pleural cavities
60% is to L of median plane
Lateral projection is ribs 3 – 6
Base is dorsal
Apex sits in sternum - costochondral junction 6
Right ventricle is CRANIAL to left ventricle!
Define the functional role of the heart in the mammalian circulatory system
Define the major anatomical features of mammalian heart
Atria form base
Blind appendages attached to atria which are called auricles
Coronary groove
Identifies junction between atria and ventricles where the main trunks of coronary vessels run (supply to the heart)
Ventricles
Paraconal groove cranially
Subspinous groove caudally
Surface markers of the interventricular septum
Describe how the right atrium ensures optimisation of the role it plays in the circulatory system
Cranial and caudal vena cava
Intervenous tubercule (roof of vena cava) - Which guides blood returning in the vena cava down to the RA
Sino-atrial node (pacemaker of heart)
Coronary sinus (termination of coronary vein delivering deoxy blood from cardiac supply to RA)
Azygous vein – R or L
Fossa ovalis (foramen ovale)
the scar from the hole between L and R A which allowed blood to flow through both atria
Describe how the left atrium ensures optimisation of the role it plays in the circulatory system
Dorsal and caudal
Under tracheal bifurcation
Pulmonary veins enter
In groups into 2 or 3 sites
In septal wall is scar of valve of f.ovale
Describe how the right ventricle ensures optimisation of the role it plays in the circulatory system
Crescentic in section
Wraps round LV cranial and to the right
Pulmonary artery is cranial and L of aorta!
Trabecula septomarginalis (strip of muscle which runs across right ventricle)
connects septum – outer wall
Describe how the left ventricle ensures optimisation of the role it plays in the circulatory system
Circular in section
Occupies all of apex
Prominent papillary muscles – muscle to which valves are attached
Aorta is central
Describe the structure and function of the cardiac skeleton
Fibrous cardiac skeleton separates atria and ventricles and provides support to the heart valves.
It insulates the ventricles from the atria so the only way electrical signals can pass is though av node
In some species such as cow you can find bony structures known as the ossa cordis
Describe the structure of the pericardium
Pericardium
Sac surrounding heart consisting of a visceral and parietal layer
Visceral layer = epicardium
Parietal layer contiguous with Blood vessels adventitial layer
Sternopericardial ligament holding heart in place
Phrenico-pericardial ligament holding the heart in place
>Both prevent distension
Describe the structure of the myocardium
Epicardium – visceral pericardium
Blood vessel adventitial layer
Myocardium – cardiomyocytes
Endocardium
Continuous with blood vessel lining
Describe the function of the atrioventricular and semilunar valves
When ventricle relaxes the pressure in atria exceeds pressure in ventricles so av valves open and blood flows into the two ventricles (ventricular diastole)
Ventricle contracts so pressure in there goes up. Once exceeds pressure in atria the av valves will shut.
Pressure will continue to rise in ventricles until semilunar valves open and blood flows through arteries
As they empty the pressure falls- once pressure in the ventricles is lower than artery the semilunar valves shut. Closure of valves result in heart sounds
List the cardiac valves and describe their features
Right AV – Tricuspid
(literally “3 cusps”, 3 in people, but actually usually 2 in our species)
Left AV – Mitral (2 cusps)
Valve leaflets are attached to Chordae tendinae which attach to papillary muscles
Prevent valve cusp prolapsing into the atrium
Describe the function of the semilunar valves
Right semilunar – pulmonic
Left semilunar – aortic
Both have three cusps
Describe the flow of blood through the adult mammalian heart
Heart contracts (systole), pushing out the blood and pumping it through the body; this is followed by a relaxation phase (diastole), where the heart fills with blood. The atria contract at the same time, forcing blood through the atrioventricular valves into the ventricles. Following a brief delay, the ventricles contract at the same time forcing blood through the semilunar valves into the aorta and the artery transporting blood to the lungs (via the pulmonary artery). Closing of the semilunar valves produces a monosyllabic “dup” sound.
Describe the major differences in cardiovascular structure between mammals and non-mammalian species.
Compare the structure and function of cardiomyocytes with skeletal muscle cells
Large, cylindrical cell
Striated (myofibrils) – like skeletal m
Short, branched fibres
Lots of mitochondria
Nuclei central in heart muscles in cells unlike in skeletal where they are positioned at the end of the cells
Myocardium cells have intimate attachments between themselves known as intercalated discs.
These ensure cells are firmly attached together by using desmosomes which anchor them together and gap junctions which allow electrical activity to pass through cells quickly
Describe structure and function of cardiomyocytes
Excitable cells
Functional (electrical) syncytium (contract instantaneously)
Structure facilitates fast Action Potential passage:
T-tubules
Sarcoplasmic reticulum
Revise sarcomere structure and function
Explain the response to injury by cardiomyocytes.
Mass increase – training/overload
Myocyte hypertrophy
No increase in cell numbers
If damaged –regeneration???
Compare skeletal muscle
Describe the structure of the semilunar and atrioventricular valves
Right semilunar – pulmonic
Left semilunar – aortic
Both have three cusps
Outline coronary circulation
L and R coronary arteries
L > R as more to supply
Arise from coronary sinus
above aortic valve (when aortic valve shuts blood is forced down these arteries, creating perfusion of the myocardium)
Perfusion only during ventricular diastole
Great cardiac vein drain into RA – coronary sinus
