Venous Circulation

Question 1

Explain the functions of veins

Answer 1

1. Forward function, change their capacitance to maintain cardiac filling & cardiac output
2. Backward function, drain the capillariesat lowest pressure as their resustance is minimal.

Question 2

Explain the functional characteristics of veins

Answer 2

1. Veins are large capauciatnce vessels act as blood reservoir, accomodate 60% of blood
2. Veins can accomodate inc in volume with minimal inc in pressure
3. More filling of veins causes stretch & marked inc in pressure and they become as stiff as arteries
4. Veins can tolerate high pressure without blow
5. Sympathetic innervation is less to veins than arteries

Question 3

GR: Veins can inc in volume without inc in pressure, describe the shape progression

Answer 3

Because they have reserve in their shape

They are normally flattened except at periphery, then become elliptical then oval then circular with inc filling

Question 4

GR; The behaviour of veins in becoming stiff as art when subjected to marked filling is protective

Answer 4

Mobilizqtion of blood towards heart

Inc capillary hydrostatic pressure and inc filtration from capillaries to minimize circulatiry overload

Question 5

GR: Veins can tolerate high pressure

Mention a surgical app

Answer 5

Because collagen, the principal component in their walls is extremely strong
They are used as arterial grafts

Question 6

Describe the role of sympathetic on veins

Answer 6

Venoconstriction:
A. Shift of the pressure/volume relation to the left
B. Decreased capacitance of veins with more mobilization of blood towards heart

Question 7

Mention the components of venous pressure

Answer 7

Mean circulatory pressure

The added pressure due to activity of the heart

Question 8

Define CVP

Answer 8

It is the pressure in right atrium & big veins in the thorax = zero.

Question 9

Define MSFP

Answer 9

It reoresents the degree of filling of the heart and all vessels with blood, it depends on the volume of blood in relation to CV capacitance, can be measured in any vessel when heart is stopped, noemally abou 7 mmHg.

Question 10

Mention the values of pressure in differenet components of venous system

Answer 10

1. Venules, 10-12 mmHg
2. Small veins, 8-10 mmHg
3. Veins, 6-8 mmHg
4. Vena cava, 0-2 mmHg

Question 11

The speed of blood in venae cavae is …..

Answer 11

25 cm/sec

Question 12

The reference point is a circular line at level of .,,,.

Answer 12

4th sternocostal joint

Question 13

What happens when pressure at the reference point is increased?

Answer 13

Inc vent filling & force of contraction, more blood is pumped out, which leads to dec pressure at this point.

Question 14

GR: The big veins of thorax are not collapsed while neck veins are collapsed

Answer 14

Because the intrathoracic pressure is -ve while the pressure in neck veins is zero so they are collapsed by the atmospheric pressure.

Question 15

GR: although venous sinuses of skull have -ve pressure they are not collapsed

Answer 15

Because the skull doesn’t transmit atmospheric pressure to them and their walls are made of tough fibrous tissue which keep them patent.

Question 16

Define HIP

Answer 16

It is a subdiaphragmatic point (2-3 inches below the opening if IVC in diaphragm) which doesn’t change on changing position. The level of this point represents the level at which the force of gravity is balanced by antigravity forces.

Question 17

HIP is shifted downwards/upwards in which cases?

Answer 17

D, when gravity overrides antig mechanisms as in block of alpha adrenergic receptors or blood loss in hemorrhage.
U, opposite, as in inc BV, venomotor tone, applying external pressure on body as in water immersion.

Question 18

GR: Filling pressure is decreased on standing from supine position

Answer 18

As the heart is located above HIP leading dec cardiac filling & CO about 30%.

Question 19

Mention Vis-A-Fronto factors

Answer 19

Thoracoabdominal pump

Cardiac suction

Question 20

Describe thoracoabdominal pump

Answer 20

CVP is decreased by more -ve intrathoracic pressure during inspiration & -ve pressure breathing
Opposite occurs in expiration & +ve pressure breathing

Question 21

Mention conditions in which cardiac suction efficiency is inc/dec (VR)

Answer 21

Inc, during rapid ejection & increased cardiac activity by symp
Dec, congestive heart failure

Question 22

Describe the effect of pressure gradient on VR

Answer 22

Constructed capillaries & dilated arterioles inc pressure gradient (PVP), & vice versa due to pooling of blood in tissues.

Question 23

Without muscle contraction, on dependency ….. of blood is dislocated to vessels below level of heart, BP in LL becomes …., but this is lowered by muscle pump to …..

Answer 23

70%
90 mmHg
17 mmHg

Question 24

What is the function of venous valves?

Answer 24

They are not an antigravity mechanism, they only ensure heart ward flow of blood, without them muscle pump is ineffective.

Question 25

Venoconsriction starts within …. & is fullfilled within …. of standing, during this time ….. is the main mechanism of VR.

Answer 25

7 sec 2-3 min Muscle pump

Question 26

What is the aim of arteriolar VC on standing?

Answer 26

Dec blood inflow into the distensible veins from the arterial side to limit the pooling of blood into them.

Question 27

Decsribe benefits & harms of resistance exercise

Answer 27

Imrove muscle strength & bone density | Cause sharp increase in systolic & diastolic BP, could prove harmful to individuals with heart & vascular disease

Question 28

Mention mechanisms of inc in HR

Answer 28

``` Psychic stimuli Dec vagal tone on heart Inc sympathetic tone on heart Adrenaline Proprioceptive impulses from exercising Inc body temperature Bainbridge refkex due to inc VR ```

Question 29

GR: increased cardiac output during aerobic exercise

Answer 29

Due to inc HR & INC CO due to inc preload, inotropy (due to psychic stimuli, inc symp discharge, ipdec vagal tone, inc CA) & dec afterload (due to dec TPR).

Question 30

What is the effect of aerobic exercise of ABP

Answer 30

SBP show great inc DBP is not changed or slighly dec due to VD of skelltal ms BV due to local metabolites MAP is slightly inc while PP is inreased

Question 31

Mention effect of aerobic exercise on different circukation

Answer 31

Coronary, pulmonary & skeletal muscle show increased blood flow Cerebral flow is unchanged Splanchnic blood flow decreases

Question 32

Describe the benefits of exercise on CV health

Answer 32

1. Decreased HR during rest & during exercise it is inc to lesser extent than sedentary person 2. Inc stroke volume in rest & exercise 3. Physiological cardiac hypertrophy, protect from cardiac fibrosis/death & cell death 4. Antiatherogenic & antihypertensive 5. Improve HR & SV reserve 6. Decrease incidence & severity of heart attacks 7. Improve coronary perfusion by better production of NO & Prostacyclin

Question 33

Describe acute & chronic effects on TPR (aerobic exercise)

Answer 33

Decreased in both

Question 34

Describe chronic effects of exercise on BP

Answer 34

Decreases below pre-exercise values and remain decreased upto 12 hrs after exercise session