Chapter 18
Respiratory System
Functions
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moves oxygen from the outside environment into the body – oxygen and
glucose later undergo a series of chemical reactions to release energy for the body
removes carbon dioxide and water vapor produced during respiration
Path of Air
1. Nose
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has 2 openings called nostrils through which air enters
air moves into the nasal cavity which is lined with blood vessels (heat the air),
mucus (moistens the air and traps dust/bacteria), and cilia (sweep the mucus into
the throat, where it is swallowed and destroyed by the stomach acid)
Note: some particles/bacteria never pass into the stomach but irritate the lining of
the nose/throat and make you sneeze to shoot them out
2. Pharynx (throat)
This is the only part of the respiratory system shared by another system (digestive)
3. The Trachea (windpipe)
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has rings of cartilage to strengthen it and keep it open
is lined with cilia and mucus to continue the cleaning and moistening of air
you cough particles that irritate the trachea lining sending harmful materials out
4. The Bronchi and Lungs
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Bronchi are passages that direct air to lungs – left one to the left lung, right to the
right lung
Inside the lungs, they divide into smaller and smaller tubes
At the end of the smallest tubes are the alveoli, which are tiny sacs surrounded by
capillaries for exchange of gases between air and blood (oxygen from alveolus to
blood, carbon dioxide from blood into alveolus). They provide a large surface
area so your lungs can absorb large amounts of oxygen.
Breathing (movement of air into and out of the lungs)
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The rate of breathing depends on body’s need of oxygen (when you exercise,
you need more oxygen, you breathe faster).
Breathing is controlled by the rib muscles and the diaphragm, a large, domeshaped muscle at the base of the lungs.
Inhaling or breathing in:
- rib muscles contract lifting chest wall up and out
- diaphragm contacts and moves in
- chest cavity is larger providing extra space for lungs to expand and have
room for air
- pressure of air inside the lungs decreases as the air occupies a larger space
- air rushes in because of the difference in air pressure
Exhaling or breathing out:
- rib muscles relax
- diaphragm relaxes
- chest cavity becomes smaller
- air is squeezed out of the lungs
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Speaking
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the larynx (voice box), made of cartilage, is in the top part of the trachea under
the epiglottis
two vocal cords, folds of connective tissue, stretch across the opening of the
larynx; have a slit like opening between them
when you speak:
- muscles make the vocal cords contract, narrowing the opening
- air from the lungs rushes through the opening
- movement of the vocal cords vibrates the air
- the vibration causes sound
when vocal cords contract and shorten, you speak in a higher voice; when they are
longer and relaxed, you speak in a lower voice
the length of the vocal cords changes during a person’s lifetime – during the teen
years, they grow longer in boys making them have deeper voices
Respiratory System Problems
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Problems related to smoking
- The tar (sticky dark substance) in tobacco smoke damages the cilia
resulting in a frequent cough and also causes cancer.
- The carbon monoxide (gas) in tobacco smoke binds to hemoglobin taking
the place of oxygen; breathing and heartbeat rates increase.
- The nicotine (drug) in tobacco smoke speeds up the activities of the
nervous system, heart and other organs and produces an addiction.
Long-term smoking will result in
chronic bronchitis: an irritation of the breathing passages which become
narrower and clogged with mucus. The mucus buildup limits the space for air
flow decreasing oxygen intake; so smokers can’t participate in vigorous sports.
emphysema: serious disease that destroys lung tissue preventing adequate
elimination of carbon dioxide; so the patient has shortness of breath
lung cancer: cancerous growths or tumors form in the lungs
fat build up in blood vessels
Passive Smoking
Involuntarily inhaling the smoke from other people’s cigarettes. cigars, or pipes
increasing their risks of heart disease and cancer.
Excretory System
Function
Collects wastes produced by the body and removes them out of the body maintaining
homeostasis
Kidneys
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your two kidneys are the major organs of excretory system eliminating urea
(produced by the breakdown of proteins), excess water, and other wastes. The
wastes are eliminated in urine produced by the nephrons of the kidneys which
filter your blood. The urine then passes into two narrow tubes, the ureters, which
carry it to the urinary bladder, a saclike muscular organ to store urine. When the
bladder is full enough, it stretches, and you feel the need to urinate. Urine passes
out of the body through a tube, the urethra. A chemical analysis of urine can be
useful in detecting medical problems such as diabetes (urine will have glucose) or
malfunctioning of kidney (urine will have protein).
Kidneys also maintain homeostasis by regulating the amount of water in body.
As urine is being formed, water passes from the tube back into the blood. How
much water is reabsorbed depends on conditions in and out of the body. If it is
hot, you sweat, and haven’t had much to drink, almost all the water in the tube
will be reabsorbed and you will excrete little urine. If it is cool and you have
drunk lots of water, less water will be reabsorbed and your body will produce
larger volume of urine.
Lungs – excrete water and carbon dioxide
Skin – excretes sweat
Liver – produces urea formed when proteins are broken down and recycles
part of hemoglobin from old blood cells into bile used in fat digestion
Large intestine – gets rid of undigested food