14. CHARACTERISTIC PRESSURES IN THE BODY (PART 2)

Question 1

1. What is one way to directly measure pressure?

Answer 1

• with a Manometer

Question 2

2. What is the measured pressure in the Manometer corresponding with?

Answer 2

• the height of the fluid column
  PLUS
• the reference pressure

THEREFORE:
P = Preference + pgh

Question 3

3. When is the Manometer commonly used?

Answer 3

• it is commonly used to measure small and moderate pressure differences

Question 4

4. What does a Manometer usually contain?

Answer 4

• one or more fluids
• such as:
  - mercury
  - water
  - alcohol
  - oil

LOOKING AT THE IMAGE:
At point 1 and 2
- the pressures are equal
- this is due to Pascal’s Law
- there is a force existent due to the Pressure

Question 5

5. What is the most common way to measure blood pressure?

Answer 5

• with the use of a Sphygmomanometer

Question 6

6. What does a Sphygmomanometer consist of?

Answer 6

• a cuff
• a squeeze bulb
• a mater
• all of this measures the pressure in the cuff

Question 7

7. What are the two types of Pressure Gauges used in Sphygmomanometers?

Answer 7

1. Mercury Manometer
2. Aneroid Manometer

Question 8

8. How is pressure indicated in a Mercury manometer?

Answer 8

• the pressure is indicated by the height of the column of mercury inside the glass

Question 9

9. How is the pressure measured in an Aneroid Manometer?

Answer 9

• the pressure changes the shape of the sealed flexible container
• this causes the needle to move on the dial

Question 10

10. What can act as a crude pressure indicator?

Answer 10

• specific parts of the body

Question 11

11. Provide two examples where parts of the body act as Crude Pressure Indicators?

Answer 11

1. A PERSON IN AN AIRPLANE:
   - will feel the changes in atmospheric pressure
   - in their ears
2. THE SIZE OF THE VEINS AT THE BACK OF THE HAND:
   - as the hand is slightly raised above the level of the
   heart
   - these veins become smaller
   - this is due to a lower venous blood pressure
   - it is more difficult to pump the pressure up
   - the pressure will fluctuate

Question 12

12. in every heart beat cycle (1/s), what can be said about the variations in the blood pressure in the major arteries?

Answer 12

• the blood pressure in the major arteries varies
  between:
  - 120 mmHg (Systolic)
  - 80 mmHg (Diastolic)

Question 13

13. What happens when the pressure in the Aneroid Manometer cuff exceeds the Systolic Pressure?

Answer 13

• there is no blood flow to the lower arm
• there are no sounds that can be heard

Question 14

14. What happens when the pressure in the Aneroid Manometer cuff is lowered with the release bulb to just below the Systolic Pressure?

Answer 14

• there is now intermittent flow of blood
• the flow fluctuates
• sound is now produced

Question 15

15. What is the pattern of the blood flow when using an Aneroid Manometer?

Answer 15

1. Smooth
2. Turbulent
3. Transitional

Question 16

16. What does the intermittent flow produce because it is Turbulent?

Answer 16

• gurgling sounds
• these are called Korotkoff
• also known as K Sounds

Question 17

17. What happens to the K Sounds as the Aneroid Manometer cuff pressure is lowered?

Answer 17

• the K sounds become louder
• and then they become lower
• they continue to be heard until the cuff pressure
  decreases to the diastolic pressure

Question 18

18. What happens to the K Sounds as the blood flow is no longer interrupted?

Answer 18

• the K Sounds cease
• this is because the blood flow is no longer turbulent

Question 19

19. What denotes the Systolic and Diastolic Blood Pressures?

Answer 19

• the onset and the end of the K Sounds

Question 20

20. What does the Brain consist of?

Answer 20

• approximately 150 cm³ of Cerebrospinal Fluid (CSF)
• these are found in a series of interconnected openings
  (ventricles)

Question 21

21. What happens if there is a block in the ventricles at birth?

Answer 21

• the Cerebral Spinal Fluid is trapped inside the skull
• this increases the internal pressure
• this increased pressure causes the skull to enlarge
• a condition known as Hydrocephalus

Question 22

22. How can Hydrocephalus be detected?

Answer 22

• the Cerebral Spinal Fluid cannot be measured directly

THEREFORE:
- we measure the circumference of the skull
- just above the ears

Question 23

23. What is the function of the clear fluid in the eyeball?

Answer 23

• it transmits the light to the retina
• it is kept under a specific pressure
• it maintains the eyeball in a fixed shape and size

Question 24

24. What is the pressure range for the normal eye?

Answer 24

• it ranges from 1.6 to 3 kPa

Question 25

25. What happens if the pressure increases in the Eyeball?

Answer 25

- it can restrict the blood supply to the Retina - this will affect vision - this condition is called Glaucoma

Question 26

26. How is the pressure in the eye measured?

Answer 26

- with Tonometers - these measure the amount of indentation produced by a known force

Question 27

27. Which pressure is larger than the atmospheric pressure?

Answer 27

- the pressure is most of the gastrointestinal system

Question 28

28. What can be said about the Pressure in the Oesophagus?

Answer 28

- the pressure is coupled to the pressure between the lungs and the chest wall - this is known as Intrathoracic Pressure (this is usually less than Atmospheric Pressure)

Question 29

29. How is the Intrathoracic Pressure sometimes determined?

Answer 29

- by measuring the pressure in the Oesophagus

Question 30

30. What happens to the pressure in the stomach when we eat?

Answer 30

- the pressure in the stomach increases as the walls of the stomach are stretched - this is mostly due to the air being swallowed during eating

Question 31

31.What does air trapped in the stomach cause?

Answer 31

- burping - belching - this air can be seen on an X-Ray of the chest

Question 32

32. What generates gas in the gut?

Answer 32

- the bacterial action increases the pressure - this generates gas - gas is also known as flatus - external factors can affect gut pressures (such as belts)

Question 33

33. Where are the highest pressures in the body found?

Answer 33

- in the weight bearing joints - these pressures are called: STRESSES

Question 34

34. What is the stress on the Knee Joint when all the weight of one leg is placed on the Joint?

Answer 34

- it may be more than 10⁶ Pascals - this is equal to 10 atm (atmospheric pressures)

Question 35

35. What aspect of the joints prevents the stress that they experience from being even higher?

Answer 35

- the relatively large area

Question 36

36. What is one of the most noticeable Internal pressures in the body?

Answer 36

- the pressure in the bladder - this is a result of the accumulation of urine

Question 37

37. What is Cystometry?

Answer 37

- a clinical diagnostic procedure - it is used to measure the forces in the bladder

Question 38

38. What does a Cystometrogram plot?

Answer 38

- it plots the volume of the liquid against the intravesicular pressure

Question 39

39. When does bladder pressure increase?

Answer 39

- during coughing - during sneezing - during straining - during sitting up - during a stressful situation - during pregnancy - when the weight of the foetus over the bladder increases the pressure - this also causes frequent urination

Question 40

40. Read through Summary 1. Does everything make sense?

Answer 40

- yes

Question 41

41. Read through Summary 2. Does everything make sense?

Answer 41

- yes

Question 42

42. Read through Summary 3. Does everything make sense?

Answer 42

- yes

Question 43

43. Read through Summary 4. Does everything make sense?

Answer 43

- yes