The heart

Question 1

Describe the principal functions of a circulatory system and appreciate how the various components of such a system are structured to fulfil these functions

Answer 1

Transport
Nutrient
Waste
O2 and CO2
Heat
Hormones

Protective – carries WBC and Ig

Homeostasis – pH, ions, fluid volume

Pressure

Question 2

Outline the pulmonary circuit of the dual pump

Answer 2

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

Question 3

Outline the systemic circuit of the dual pump

Answer 3

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

Question 4

Outline the blood supply to the liver

Answer 4

Blood first travels through the digestive tract then to the liver through the hepatic portal vein

Question 5

Outline the blood supply to the kidneys

Answer 5

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

Question 6

Describe the necessity for a dual circulatory system in the adult mammal

Answer 6

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

Question 7

Describe the anatomical landmarks of the heart

Answer 7

Ventral border of the lungs
Cardiac notch (L>R)

Lungs laterally
Phrenic nerve runs along the heart

Thymus cranially
In young animals

Diaphragm caudally

Question 8

Describe the postion of the heart

Answer 8

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!

Question 9

Define the functional role of the heart in the mammalian circulatory system

Question 10

Define the major anatomical features of mammalian heart

Answer 10

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

Question 11

Describe how the right atrium ensures optimisation of the role it plays in the circulatory system

Answer 11

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

Question 12

Describe how the left atrium ensures optimisation of the role it plays in the circulatory system

Answer 12

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

Question 13

Describe how the right ventricle ensures optimisation of the role it plays in the circulatory system

Answer 13

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

Question 14

Describe how the left ventricle ensures optimisation of the role it plays in the circulatory system

Answer 14

Circular in section

Occupies all of apex

Prominent papillary muscles – muscle to which valves are attached

Aorta is central

Question 15

Describe the structure and function of the cardiac skeleton

Answer 15

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

Question 16

Describe the structure of the pericardium

Answer 16

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

Question 17

Describe the structure of the myocardium

Answer 17

Epicardium – visceral pericardium
Blood vessel adventitial layer

Myocardium – cardiomyocytes

Endocardium
Continuous with blood vessel lining

Question 18

Describe the function of the atrioventricular and semilunar valves

Answer 18

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

Question 19

List the cardiac valves and describe their features

Answer 19

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

Question 20

Describe the function of the semilunar valves

Answer 20

Right semilunar – pulmonic

Left semilunar – aortic

             Both have three cusps

Question 21

Describe the flow of blood through the adult mammalian heart

Answer 21

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.

Question 22

Describe the major differences in cardiovascular structure between mammals and non-mammalian species.

Question 23

Compare the structure and function of cardiomyocytes with skeletal muscle cells

Answer 23

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

Question 24

Describe structure and function of cardiomyocytes

Answer 24

Excitable cells
Functional (electrical) syncytium (contract instantaneously)

Structure facilitates fast Action Potential passage:
T-tubules
Sarcoplasmic reticulum

Revise sarcomere structure and function

Question 25

Explain the response to injury by cardiomyocytes.

Answer 25

Mass increase – training/overload
Myocyte hypertrophy
No increase in cell numbers

If damaged –regeneration???
Compare skeletal muscle

Question 26

Describe the structure of the semilunar and atrioventricular valves

Answer 26

Right semilunar – pulmonic

Left semilunar – aortic

             Both have three cusps

Question 27

Outline coronary circulation

Answer 27

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