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Questions and Answers
What is pressure defined as?
What is pressure defined as?
In the equation P = ρgh, what does 'h' represent?
In the equation P = ρgh, what does 'h' represent?
What is the typical range for arterial blood pressure during systole?
What is the typical range for arterial blood pressure during systole?
What instrument is primarily used to measure blood pressure?
What instrument is primarily used to measure blood pressure?
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How would negative pressure in the lungs affect breathing?
How would negative pressure in the lungs affect breathing?
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How is atmospheric pressure quantified?
How is atmospheric pressure quantified?
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What is the function of the cerebral spinal fluid (CSF) in the brain?
What is the function of the cerebral spinal fluid (CSF) in the brain?
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Which of the following pressures is typically found in the middle ear?
Which of the following pressures is typically found in the middle ear?
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What happens to the volume of a gas if its absolute pressure is doubled?
What happens to the volume of a gas if its absolute pressure is doubled?
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What causes pressure equalization in the middle ear?
What causes pressure equalization in the middle ear?
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What can occur if the partial pressure of O2 at a depth of 30m exceeds safe levels?
What can occur if the partial pressure of O2 at a depth of 30m exceeds safe levels?
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What does Henry's law state regarding the solubility of gases in liquids?
What does Henry's law state regarding the solubility of gases in liquids?
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Which condition can hyperbaric oxygen therapy help treat?
Which condition can hyperbaric oxygen therapy help treat?
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What serious condition arises when cerebrospinal fluid (CSF) is trapped inside the skull due to a blocked aqueduct?
What serious condition arises when cerebrospinal fluid (CSF) is trapped inside the skull due to a blocked aqueduct?
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What is the normal range of skull circumference values indicating healthy newborns?
What is the normal range of skull circumference values indicating healthy newborns?
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Which method is used for qualitatively detecting hydrocephalus based on light scattering properties of CSF?
Which method is used for qualitatively detecting hydrocephalus based on light scattering properties of CSF?
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What is the target range for intraocular pressure (IOP) in normal eyes?
What is the target range for intraocular pressure (IOP) in normal eyes?
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What condition is caused by increased pressure within the eye, potentially leading to blindness?
What condition is caused by increased pressure within the eye, potentially leading to blindness?
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How does eating affect the pressure in the stomach?
How does eating affect the pressure in the stomach?
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Which instrument is specifically used to measure intraocular pressure?
Which instrument is specifically used to measure intraocular pressure?
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What happens if there is a blockage in the eye's drainage system?
What happens if there is a blockage in the eye's drainage system?
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What is the primary function of pressure in the gastrointestinal (GI) system?
What is the primary function of pressure in the gastrointestinal (GI) system?
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What causes an increase in gut pressure during digestion?
What causes an increase in gut pressure during digestion?
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What is the function of the pylorus in the digestive system?
What is the function of the pylorus in the digestive system?
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What can result from a blockage in the small or large intestine?
What can result from a blockage in the small or large intestine?
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What is a primary method of treatment for intestinal blockage?
What is a primary method of treatment for intestinal blockage?
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How does the surface area of a bone at a joint affect pressure?
How does the surface area of a bone at a joint affect pressure?
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What is the typical maximum volume of the bladder before voiding in adults?
What is the typical maximum volume of the bladder before voiding in adults?
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What pressure is typically reached during the micturition reflex?
What pressure is typically reached during the micturition reflex?
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Which technique provides information about bladder function through direct measurement?
Which technique provides information about bladder function through direct measurement?
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What reaction occurs in the bladder during pregnancy as the fetus exerts pressure?
What reaction occurs in the bladder during pregnancy as the fetus exerts pressure?
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What is a notable characteristic of the body in relation to pressure and gas cavities?
What is a notable characteristic of the body in relation to pressure and gas cavities?
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What pressure in cmH2O may men experience due to prostate obstruction of the urinary passage?
What pressure in cmH2O may men experience due to prostate obstruction of the urinary passage?
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Study Notes
Pressure in the Body
- Pressure is defined as force per unit area
- Pressure under a liquid column (P) is calculated using the formula: P = pgh
- p = density of the liquid
- g = acceleration due to gravity
- h = height of the liquid column
Example Calculation
-
Finding the height of water that produces the same pressure as 120 mmHg
- Given: 120 mmHg , p water = 1 g/cm³ , p Hg = 13.6 g/cm³
- Calculated height of water = 163 cm
-
Atmospheric pressure calculation
- 1 atm = 760 mmHg = 76 cmHg
- Atmospheric pressure in N/m² = 1.01 x 10⁵ N/m²
Types of Pressure
- Gauge pressure: The excess pressure over atmospheric pressure
- Negative pressure: Any pressure lower than atmospheric pressure
- Example: Lung pressure during inspiration
Typical Pressure in the Normal Body
| Body Part | Typical Pressure (mmHg) |
|---|---|
| Arterial blood pressure, max (systole) | 100-140 |
| Arterial blood pressure, min (diastole) | 60-90 |
| Venous blood pressure | 3-7 |
| Middle ear pressure | Less than 1 |
| Eye pressure | 12-23 |
| CSF (cerebrospinal fluid) inside the brain | 5-12 |
Measurement of Pressure in the Body
- Instrument for measuring pressure is a manometer
- Sphygmomanometer: Common clinical instrument used for measuring pressure
Pressure Inside the Skull
- Brain contains approximately 150 cm³ of CSF (cerebrospinal fluid)
- CSF flows through connected openings (ventricles)
CSF Pressure Measurement Methods
- Crude method: Measuring skull circumference above the ears
- Normal values for newborns: 32–37 cm
- Trans-illumination: Qualitative method using light-scattering properties of CSF
Eye Pressure
- Normal eyes' pressure: 12–23 mmHg
- Glaucoma: Condition due to blocked drain system; increases pressure, damaging optic nerve; symptoms include tunnel vision and blindness
Measuring Eye Pressure
- Determining eye pressure by feeling
- Using a tonometer to measure eye pressure
Pressure inside the Eye
- Intraocular pressure (IOP) is measured using the formula:
- IOP = Load/area(1 + Rlens /Rcornea )
Pressure in the Digestive System
- Gastrointestinal (GI) system pressure is higher than atmospheric pressure
- Affects the proper flow of food
Digestive System Pressure Factors
- Eating increases stomach pressure due to volume increase
- Swallowed air during eating causes belching or burping
- Bacteria action generates gas (flatus) in the gut, increasing gut pressure
Pressure in the Gastrointestinal System
- Pylorus: valve prevents food reflux from the small intestine
- Blockage in the small or large intestine causes high pressure, causing organ damage or death; treatment with intubation and/or surgery
- Belts, girdles, or swimming can affect gut pressure
Pressure in the Skeleton
- Highest pressures in the body are in weight-bearing bones (joints)
- Knee joint pressure can exceed 10 atm
- Larger joint surface areas distribute force, thus lessening pressure; finger bones are flat and spread force over a greater area
Pressure in the Urinary Bladder
- Bladder pressure varies as bladder volume increases
- Adult bladder capacity before voiding: 500 ml
- Micturition reflex occurs at ~30 cm H₂O
Measuring Bladder Pressure
- Catheter with pressure sensor inserted into the bladder (urethra)
- Needle inserted through the abdominal wall directly into the bladder
Additional Pressures
- Coughing, straining, sitting, and fetal weight increase bladder pressure, causing frequent urination
- Normal voiding pressure: 20-40 cm H₂O
- Prostrate obstruction may increase pressure to over 100 cm H₂O
Diving Effects
- The human body is composed of incompressible solids and liquids
- Pressure changes do not significantly impact most parts of the body
- Gas cavities are affected by sudden pressure changes
Boyle's Law:
- Constant temperature, product of pressure and volume of a gas is constant. If pressure doubles, the volume is halved.
Middle Ear Pressure
- Middle ear pressure should equal external pressure for comfort
- Eustachian tube usually closed, and it's difficult to equalize pressure during swallowing, chewing, or yawning
- Pressure difference (120 mmHg) across the ear drum can damage it (ruptures) when diving
Hyperbaric Oxygen Therapy (HOT)
- HOT increases oxygen proportion, beneficial to tissues
- Treats gas gangrene (bacillus cannot survive in oxygen) and carbon monoxide poisoning
Henry's Law
- Amount of gas dissolved in a liquid is proportional to the partial pressure of that gas (in contact with the liquid)
Other Info
- The breathing air at depth is a higher partial pressure of O₂ than at sea level; may cause oxygen poisoning
- Breathing air at depth > 30 m is dangerous due to excess N₂ in the blood and tissue, resulting in nitrogen narcosis (intoxication)
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Description
Test your knowledge on the principles of pressure as they relate to physiology and medicine. This quiz covers essential concepts such as blood pressure, gas laws, and the functions of cerebrospinal fluid. Perfect for students studying human biology or health sciences.
