Circulatory Structure

Question 1

what energy does the heart convert?

Answer 1

• chemical energy in the form of glucose (used in muscle contraction)
• to mechanical energy (to pump blood around the body)

Question 2

bulk flow

Answer 2

flow of blood to tissues after each pump

Question 3

Einstein’s diffusion constant equation

Answer 3

t ∝ x²

Question 4

infarct

Answer 4

formation of a dense wedge of dead tissue in the heart muscle from ischaemia (lack of oxygenated blood supply to the tissue)

Question 5

ischaemia

Answer 5

lack of blood supply to a tissue

Question 6

equivalent of pulmonary circuit in fish

Answer 6

branchial circuit (blood supply to gills)

Question 7

what does the aorta divide into?

Answer 7

• ascending and descending arteries
• descending arteries divide into thoracic and abdominal arteries

Question 8

what sac is the heart located within? what is it attached to?

Answer 8

• pericardial sac
• attached to diaphragm so that normal breathing tends to rock the heart

Question 9

thrombus

Answer 9

blood clot that forms within a blood vessel

Question 10

hypoxia

Answer 10

low partial pressures of oxygen in tissue

Question 11

necrosis

Answer 11

death of tissue due to insufficient blood supply

Question 12

arrhythmia

Answer 12

abnormal heart rhythm caused by problems in the heart’s conduction systems

Question 13

heart attack

Answer 13

blockage/complete lack of blood supply to heart tissue

Question 14

chronological stages of oxygen starvation in the heart

Answer 14

• thrombus
• ischaemia
• hypoxia
• necrosis
• arrhythmia
• heart attack

Question 15

layers of the heart wall

Answer 15

• epicardium
• myocardium
• endocardium

Question 16

epicardium and its roles

Answer 16

• thin layer of connective tissue covering the heart
• source of paracrine cues essential for cardiac growth, coronary vessel patterning, regenerative heart repair

Question 17

myocardium

Answer 17

the contractile machinery and cardiomyocytes forming the middle layer of the heart wall

Question 18

endocardium and its role

Answer 18

• internal layer formed by endothelial cells
• role in valve formation

Question 19

heart “skeleton”

Answer 19

• collagen forms a junction between the atria and the ventricles
• annulus fibrosus holds the cardiac valves

Question 20

chordae tendineae

Answer 20

• tendons which hold the AV valves in place and prevent them from being pushed backwards into the atria
• semilunar valves do not need them as they have three cup-like leaflets that snap close when blood flows backwards =

Question 21

three layers of blood vessels

Answer 21

• tunica intima
• tunica media
• tunica adventitia

excluding capillaries

Question 22

tunica intima structure and function

Answer 22

structure:
- inner lining of blood vessels
- thin layer of endothelial cells (type of epithelium)
- elastic connective tissue
- basement membrane

function: stretch and recoil to maintain blood flow and maintain shape of blood vessels

Question 23

tunica media structure and function

Answer 23

structure:
- middle layer of blood vessels
- densely, concentrically packed smooth muscle cells
- bands or fibres of elastic tissue

function: constrict and relax to maintain blood flow and pressure

Question 24

tunica adventitia structure and function

Answer 24

structure:
- outer layer of blood vessels
- collagenous extracellular matrix
- contains fibroblasts
- contains blood vessels and nerves

function: provide rigidity and prevent bursting

Question 25

capillary structure

Answer 25

- endothelium (tunica intima) - basement membrane

Question 26

artery structure

Answer 26

elastic artery: - thicker tunica intima (more elastin) - absorb large pressures - decrease pressure surges to prevent bursting smaller vessels further on muscular artery: - thinner tunica intima (less elastin) - thicker tunica media (more smooth muscle) - stronger force of contraction to maintain blood pressure

Question 27

two types of arteries

Answer 27

elastic arteries - conducting arteries (aorta and pulmonary arteries) muscular arteries - distributing arteries

Question 28

vein structure

Answer 28

- contain valves - thinner tunic intima, media and adventitia - less need for collagen and strong walls due to low blood pressure - less smooth muscle and elastin needed due to wide lumen and less resistance to blood flow

Question 29

arteriole vs venule structure

Answer 29

arterioles have a thicker tunica media for vasoconstriction and vasodilation (although venoconstriction does occur)

Question 30

respiratory pump

Answer 30

- aids venous return - diaphragm relaxes, thoracic pressure decreases, abdominal pressure increase, squeezes abdominal veins - maintaining venous return maintains cardiac output

Question 31

where does the oxygen supply for a fetus come from?

Answer 31

placenta

Question 32

P50

Answer 32

partial pressure of oxygen at which 50% of haemoglobin is saturated with oxygen

Question 33

what happens to the fetal oxygen-haemoglobin dissociation curve and therefor P50?

Answer 33

- fetal curve shifts to the left (from maternal curve) - P50 decreases

Question 34

fetal adaptations for oxygen supply

Answer 34

- fetal haemoglobin has as greater affinity for oxygen - preferential streaming

Question 35

preferential streaming

Answer 35

- fetus has shunts in circulation - blocks blood supply to organs that aren't currently in use to prioritise oxygen supply to the brain etc

Question 36

fetal shunts

Answer 36

- ductus venosus - foramen ovale - ductus arteriosus

Question 37

ductus venosus

Answer 37

shunts richly oxygenated blood coming from the placenta to the fetal heart, bypassing most of liver circulation

Question 38

foramen ovale

Answer 38

shunts blood from the right atrium to the left atrium, bypassing the lungs and ventricles

Question 39

ductus arteriosus

Answer 39

shunts blood from the pulmonary artery to the descending aorta

Question 40

how does the foramen ovale close?

Answer 40

- lungs expand once baby takes first breath - pulmonary blood flow increases - lowers right atrial pressure and raises left atrial pressure - flow of blood from left to right atrium is prevented by two flap-like valves - prolonged contact between foramen ovale valve and septum secundum valve creates fibrous connections between the two and permanent closure

Question 41

what does the ductus venosus and ductus arteriosus respond to?

Answer 41

dilator prostaglandins secreted by the placenta

Question 42

how do the ductus venosus and ductus arteriosus close?

Answer 42

- cut umbilical cord ends supply of dilator prostaglandins - constricted DV becomes ligamentum venosum - constricted DA becomes ligamentum arteriosum