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Narrow range of atmospheric pressure

Pressure is a force exerted by a substance that is in contact with another substance. Atmospheric pressure is pressure exerted by the mixture of gases (primarily nitrogen and oxygen) in the Earth’s atmosphere. Although you may not perceive it, atmospheric pressure is constantly pressing down on your body. This pressure keeps gases within your body, such as the gaseous nitrogen in body fluids, dissolved. If you were suddenly ejected from a space ship above Earth’s atmosphere, you would go from a situation of normal pressure to one of very low pressure. The pressure of the nitrogen gas in your blood would be much higher than the pressure of nitrogen in the space surrounding your body. As a result, the nitrogen gas in your blood would expand, forming bubbles that could block blood vessels and even cause cells to break apart.

Atmospheric pressure does more than just keep blood gases dissolved. Your ability to breathe—that is, to take in oxygen and release carbon dioxide—also depends upon a precise atmospheric pressure. Altitude sickness occurs in part because the atmosphere at high altitudes exerts less pressure, reducing the exchange of these gases, and causing shortness of breath, confusion, headache, lethargy, and nausea. Mountain climbers carry oxygen to reduce the effects of both low oxygen levels and low barometric pressure at higher altitudes ( [link] ).

Harsh conditions

This photo shows Mount Everest as seen from a distance. It is a large, pyramid-shaped, craggy peak with many smaller snow-covered peaks in the foreground. The peak of Mount Everest is partially occluded by clouds.
Climbers on Mount Everest must accommodate extreme cold, low oxygen levels, and low barometric pressure in an environment hostile to human life. (credit: Melanie Ko/flickr)

Homeostatic imbalances

Decompression sickness

Decompression sickness (DCS) is a condition in which gases dissolved in the blood or in other body tissues are no longer dissolved following a reduction in pressure on the body. This condition affects underwater divers who surface from a deep dive too quickly, and it can affect pilots flying at high altitudes in planes with unpressurized cabins. Divers often call this condition “the bends,” a reference to joint pain that is a symptom of DCS.

In all cases, DCS is brought about by a reduction in barometric pressure. At high altitude, barometric pressure is much less than on Earth’s surface because pressure is produced by the weight of the column of air above the body pressing down on the body. The very great pressures on divers in deep water are likewise from the weight of a column of water pressing down on the body. For divers, DCS occurs at normal barometric pressure (at sea level), but it is brought on by the relatively rapid decrease of pressure as divers rise from the high pressure conditions of deep water to the now low, by comparison, pressure at sea level. Not surprisingly, diving in deep mountain lakes, where barometric pressure at the surface of the lake is less than that at sea level is more likely to result in DCS than diving in water at sea level.

In DCS, gases dissolved in the blood (primarily nitrogen) come rapidly out of solution, forming bubbles in the blood and in other body tissues. This occurs because when pressure of a gas over a liquid is decreased, the amount of gas that can remain dissolved in the liquid also is decreased. It is air pressure that keeps your normal blood gases dissolved in the blood. When pressure is reduced, less gas remains dissolved. You have seen this in effect when you open a carbonated drink. Removing the seal of the bottle reduces the pressure of the gas over the liquid. This in turn causes bubbles as dissolved gases (in this case, carbon dioxide) come out of solution in the liquid.

The most common symptoms of DCS are pain in the joints, with headache and disturbances of vision occurring in 10 percent to 15 percent of cases. Left untreated, very severe DCS can result in death. Immediate treatment is with pure oxygen. The affected person is then moved into a hyperbaric chamber. A hyperbaric chamber is a reinforced, closed chamber that is pressurized to greater than atmospheric pressure. It treats DCS by repressurizing the body so that pressure can then be removed much more gradually. Because the hyperbaric chamber introduces oxygen to the body at high pressure, it increases the concentration of oxygen in the blood. This has the effect of replacing some of the nitrogen in the blood with oxygen, which is easier to tolerate out of solution.

The dynamic pressure of body fluids is also important to human survival. For example, blood pressure, which is the pressure exerted by blood as it flows within blood vessels, must be great enough to enable blood to reach all body tissues, and yet low enough to ensure that the delicate blood vessels can withstand the friction and force of the pulsating flow of pressurized blood.

Chapter review

Humans cannot survive for more than a few minutes without oxygen, for more than several days without water, and for more than several weeks without carbohydrates, lipids, proteins, vitamins, and minerals. Although the body can respond to high temperatures by sweating and to low temperatures by shivering and increased fuel consumption, long-term exposure to extreme heat and cold is not compatible with survival. The body requires a precise atmospheric pressure to maintain its gases in solution and to facilitate respiration—the intake of oxygen and the release of carbon dioxide. Humans also require blood pressure high enough to ensure that blood reaches all body tissues but low enough to avoid damage to blood vessels.

Questions & Answers

The major digestive gland
Jasamin Reply
The neck is _____ to the navel.
Duchess Reply
connected
FAITH
connected
Fartun
.
Rachna
cranial
Sarah
the function of pancreatic juice is
Elastus
Describe the sequence of injuries that may occur if the extended, weight-bearing knee receives a very strong blow to the lateral side of the knee.
Dondon Reply
what is anotomy and waht is phesiology
chanbasha Reply
anatomy is classified the origin physiology is functional of origin
oHo
classified origin functional of origin
Sheryl
Anatomy is the origin of the human body Physiology is the function of the human body
Rose
Differentiate between pharmacist and apothecary
adanoor Reply
What is metatarsal
Ndotenyin Reply
bone of the foot is known as metatarsal
Patrick
yes 👆 right
Sneha
metatarsal (foot bone).....👍
Rishi
what is the meaning for cadavers
Malar
yes metatarsal are foot bone
Rakiya
the term "mental" pertain to which of the following a. chin b.navel c. ear d. nose e. skull
cris Reply
a
Lina
chin
Sneha
hi
Mohamed
skull
Monica
skull
Peter
chin
Kelly
skull
Juma
skull
Gul
skull
Laraib
skull
anwaar
skull
Nirmala
skull
Tessmol
chin
Derrick
mental chin nerve
Katarzyna
e. skull
Jennifer
skull
prince
e. skull
Natasha
It's not skull but chin
mwango
the skull
Rakiya
what are the three many components of the lymphatic system?
Milica Reply
those are...... organ, tissue and blood capillary or vessals
Juma
anatomical terms and use them appropriatly in the language of anatomy of anterior body landmarks
Teody Reply
what is human anatomy?
rascal Reply
lts stady structured human body's
Sa
what is the study of how the body functions?
Bright
What is human anatomy
Sherifat
human antomy is the body of structure
Malar
is the study of human body
Rakiya
what is abdomipelvic cavity?
david Reply
Includes all organs within the abdomen(stomach,intestines) and those from the pelvic region hence the name... abdomipelvic
Maureen
where can we find the short bones
Chidi Reply
Carpal bones are examples of short bones
Dara
what is blood supply
Chidi
on upper limb and lower limb
Juma
carpal bones
Priya
during pregnancy which would more increase size the mothers abdominal or pelvic cavity?
Nurmalyn Reply
pelvic cavity I think
Priya
What is anatomical position
Nwoye
pelvic
Maureen
@ Nwoye... when standing erect, feet parallel, arms hanging at the sides with palms facing forward
Maureen
The pelvic cavity
Rakiya
pelvic
Malar
define the main directional terms of the body
cris Reply
during physical exercise respiratory rate increace two student are discussing the mechanisms involved. student A claim they are positive feedback and student B claim negative feedback do you agree with student A or B and why
cris
what is the physiology of circulation
Chidi
please I mean the physiology of criculation
Chidi
blood flow refers to the movement of blood through the vessels from arteries to the capillaries and then to the veins
Laraib
the heart&the lungs
Rakiya
during pregnancy, which would more size the mother's abdominal or pelvic cavity? explain
cris Reply
list and define the three plane of devision of the body
cris
complete the following statements using correct directional terms for human being. 1. the navel is________to the nose 2. the heart is______to the breastbone(sternum) 3 the ankle is______to the knee 4 the ear is______to the eyes.
cris
1. superior 2. posterior 3. superior 4. lateral
Mnm
anterior fuerior
Chidi
inferior medial posterior lateral we
Susan

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Source:  OpenStax, Anatomy & Physiology. OpenStax CNX. Feb 04, 2016 Download for free at http://legacy.cnx.org/content/col11496/1.8
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