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By the end of this section, you will be able to:
  • Discuss the role of oxygen and nutrients in maintaining human survival
  • Explain why extreme heat and extreme cold threaten human survival
  • Explain how the pressure exerted by gases and fluids influences human survival

Humans have been adapting to life on Earth for at least the past 200,000 years. Earth and its atmosphere have provided us with air to breathe, water to drink, and food to eat, but these are not the only requirements for survival. Although you may rarely think about it, you also cannot live outside of a certain range of temperature and pressure that the surface of our planet and its atmosphere provides. The next sections explore these four requirements of life.

Oxygen

Atmospheric air is only about 20 percent oxygen, but that oxygen is a key component of the chemical reactions that keep the body alive, including the reactions that produce ATP. Brain cells are especially sensitive to lack of oxygen because of their requirement for a high-and-steady production of ATP. Brain damage is likely within five minutes without oxygen, and death is likely within ten minutes.

Nutrients

A nutrient    is a substance in foods and beverages that is essential to human survival. The three basic classes of nutrients are water, the energy-yielding and body-building nutrients, and the micronutrients (vitamins and minerals).

The most critical nutrient is water. Depending on the environmental temperature and our state of health, we may be able to survive for only a few days without water. The body’s functional chemicals are dissolved and transported in water, and the chemical reactions of life take place in water. Moreover, water is the largest component of cells, blood, and the fluid between cells, and water makes up about 70 percent of an adult’s body mass. Water also helps regulate our internal temperature and cushions, protects, and lubricates joints and many other body structures.

The energy-yielding nutrients are primarily carbohydrates and lipids, while proteins mainly supply the amino acids that are the building blocks of the body itself. You ingest these in plant and animal foods and beverages, and the digestive system breaks them down into molecules small enough to be absorbed. The breakdown products of carbohydrates and lipids can then be used in the metabolic processes that convert them to ATP. Although you might feel as if you are starving after missing a single meal, you can survive without consuming the energy-yielding nutrients for at least several weeks.

Water and the energy-yielding nutrients are also referred to as macronutrients because the body needs them in large amounts. In contrast, micronutrients are vitamins and minerals. These elements and compounds participate in many essential chemical reactions and processes, such as nerve impulses, and some, such as calcium, also contribute to the body’s structure. Your body can store some of the micronutrients in its tissues, and draw on those reserves if you fail to consume them in your diet for a few days or weeks. Some others micronutrients, such as vitamin C and most of the B vitamins, are water-soluble and cannot be stored, so you need to consume them every day or two.

Questions & Answers

The diagram of the human body
Rasheedat Reply
what is agriculture?
Maror Reply
Is a branch of sciences that deal with the study of plant and it species
Lucky
what's the functional unit of the kideny
Oyebode Reply
urinary tubule
Adebayo
what are surfaces of prostate
Lorna Reply
functions of physiologist
moses Reply
pathophysiology of pneumonia
Jane Reply
what is anatomy
Ejiofor Reply
The study of the body parts
Joyce
Study of structure of living things eg humans
Nasreen
how many bones do the human being has
Grace
An adult has 206 bones.
Lydia
study of the function of the body parts
Monday
physiology
Lydia
definition of community case of desase ?in malaria,thyphus, cholera,
Yisihak
Yes In children is 270 But adult is 206
Chy
physiology is the study of functions of body structures
Juliet
describe the distinctive functional types of lymphocytes
Juliet
what's anatomy
Fetia Reply
it is the scientific study of human body structures.
Ahmad
It is the study of human structure
Phillip
is the study of human structure
ayodele
Can someone identify to me the types of sciatic nerves
John
What's ovulation ?
godknows Reply
Ovulation is the release of eggs from the ovaries. In women, this event occurs when the ovarian follicles rupture and release the secondary oocyte ovarian cells.
Nasriya
Ovulation is the release of eggs from ovaries
Malina
how long vagina is
Antony Reply
approximately 10 cm
Edrick
Muscle is a connective tissue
Benard Reply
sure?
Deds
you're right intramuscular connective tissue formed by the 3 layers of the muscle
Deds
hi tanks
Abdulhaq
Hi , please good night how was everyone, please am first year mbbs
Mercy
I like to share with...?”
Sengiyumva
hi
Hawah
hello
Adejumo
what muscles
Rukayya Reply
what is anatomy
Ayomide Reply
is the study of body parts
zaituni
Anatomy is a science that deals with the study of human parts and animals.
godknows
Anatomy is the study of the branch of biology concerned with the structure of the organisms and their parts
Malina
what is a kidney
Sailuba Reply
The kidney is an organ whose function is primarily for excretion of extra fluids as wastes.
Nasriya
Yeah your collect
Isack
and ions e.g potassium, sodium, phosphates etc
Meshack
yes nasriya
Bpagan
what is physiology
Rukayya
hello all🤚🤚
Rukayya
i think its the study of all of the processes in a living thing and how they relate to eachother.
Kory
Hello scholars
am
hi friends what is heart
aminu
heart is hollow muscular organ responsible bumping of blood our body
Caisho
what is muscle and the type
aminu
muscles is acontractile tissue found in animals
Caisho
types of muscle are three smooth muscle cardiac muscle and skeletal muscle
Caisho
what is the difference between microscopic and macroscopic
Sofeme Reply
Microscopic mean the use of microscope during investigation of sample & macroscopic means observing by using eyes (physically)
Isack

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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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