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Objectives
1.
Overview
of the Respiratory system: Air moves
via this route: nasal cavities à nasopharynx à
pharynx àlarynx àvocal cords (space between is
glottis) à trachea à Bronchi?à
Bronchioles à Respiratory bronchioles à
Alveoli. Be able to recognize these
structures on a figure. See figures
10.1-3 in your text. Look at the
Anatomy Review on the CD. A verbal
overview of this rout.
2.
Where
is the site of Gas Exchange in the Lungs
3.
What factors influence gas exchange: transport Pigments,
temperature pH.
4.
Ventilation.
Describe the process of taking a breath. (How we inhale and exhale)
5.
How
does the body control ventilation and gas exchange?
6.
Describe
respiration in unusual environments: Decompression sickness, and Hypoxia, esp. CO
poisoning
7.
Can
you die form holding your breath? Explain the neural mechanisms that are
operating here.
8.
Know
how the following Diseases work. Asthma, Cystic Fibrosis,
Pneumonia, colds.
Figures 10.1 anatomy, 10.7 the lungs and its
membranes, 10.8 gas exchange10.9 respiratory cycles, 10.11 partial pressures,
10.12 transportation 10.13 regulation of breathing.
1. How does the body respond to altitude?
A. Aerobic metabolism requires oxygen, but at higher altitudes, the oxygen molecules are farther apart, requiring extra effort by the body to breathe.
B. The body responds with deeper and faster breathing plus the production of more red blood cells: nevertheless, ascents to the heights of places like Mount Everest are treacherous, due to a lack of oxygen.
2. An overview of the Respiratory system
A. Airways to the Lungs (breathing or ventilation)
1) The respiratory system brings in oxygen that each body cell requires and takes away carbon dioxide that every cell generates.
2) Through nasal cavities, air enters or leaves the respiratory system: hair and ciliated epithelium filter dust and particles. Blood vessels warm the air and mucus membranes moisten it.
a) The nasal cavities are separated by a septum of carriage and bone.
b) The paranasal sinuses lie just above the cavities and are linked to them by channels.
3)
Air moves via this route:
Nasal cavities à Nasopharynx à Pharynx àLarynx àVocal cords (space between is glottis) à trachea à Bronchi?à Bronchioles à Respiratory bronchioles à Alveoli.
a) The trachea leads form the larynx downward to branch into two bronchi, which are lined with cilia and mucus to trap bacteria and particles of dust.
b) The bronchi branch repeatedly into smaller bronchioles (including respiratory bronchioles), which lead ultimately to the dead-end alveoli.
B. Sites of Gas Exchange in the Lungs (external respiration between air and blood)
1) Human lungs are a pair of organs housed in the thoracic cavity under the rib cage above the diaphragm.
a) Each lung lies within a thin pleural membrane that is folded in a manner that forms a pleural sac leaving an intrapleural space filled with a lubricating intrapleural fluid.
b) Pleurisy is an inflammation of the pleural membranes, usually the consequence of a bacterial or viral infection.
2) Inside the lungs, respiratory bronchioles bear outpouchings of their walls called alveoli (usually clustered as alveolar sacs), which provide a tremendous surface area for gaseous exchange with the blood located in the dense capillary network surrounding each alveolar sac. Each alveolar sac is only one epithelial cell thick.
3. Factors that influence gas exchange
A. Partial Pressure Gradients (The wind moves from a high pressure area to a low pressure area)
1) Respiratory systems rely on the diffusion of gases down pressure gradients.
a) Air is 78% nitrogen, 21% oxygen, 0.04% carbon dioxide, and 0.96% other gases.
b) Partial pressures for each gas in the atmosphere can be calculated: for example, oxygen’s is 160mm Hg.
c) Oxygen and carbon dioxide diffuse down pressure gradients from areas of high partial pressure to areas of low partial pressure. (Oxygen is scarce in the body and carbon dioxide is in high concentrations in the body)
2) Diffusion will occur across a respiratory surface if it is thin and moist. (a must for breathing!)
3) The speed and extent of diffusion depends on the surface area present in the respiratory organs.
B. Transport Pigments.
1) Hemoglobin is the main transport pigment (a molecule that binds to and releases oxygen, it happens to be red so they call it a pigment)
2) Each molecule binds four molecules of oxygen in the lungs (high concentration) and releases them in the tissues where the oxygen partial pressure is low.
A. Ventilation has two phases:
1) To inhale (inspiration), the diaphragm contracts and flattens, muscles lift the rib cage upward and outward, the chest cavity volume increases, internal pressure decreases, air rushes in.
2) To exhale (expiration) the actions listed above are reversed: the elastic lung tissue recoils passively.
B. Lung volumes
1) About 500ml (a can of pop) of air (tidal volume) enters and leaves with each breath.
a) From a normal breath, a human can forcibly inhale 3,100 ml of air (inspiratory reserve volume) and forcible exhale 1,200 (expiratory reserve volume).
b) The maximum volume that can be moved in and out is called the vital capacity, 4800 ml for males, 3800 ml for females.
2) About 1,200 ml of residual air remains in the lungs and cannot be forced out.
C. Breathing and sound Production
1) The vocal cords, which lie on either side of the larynx wall, are elastic ligaments that vibrate when air passes out through the space between them called the glottis, which is closed off during swallowing to prevent choking by the epiglottis.
2) Laryngitis is an inflammation of the vocal cords, which interferes with their ability to vibrate properly.
5. Gas Exchange and Transport
A. Ventilation is not the same as respiration, which is the actual exchange of gases between the blood and cells
1) In external respiration, oxygen moves form the alveoli to the blood: carbon dioxide moves in the opposite direction.
2) In internal respiration, oxygen moves form the blood into tissues and vice versa for carbon dioxide.
B. Gas Exchange in Alveoli
1) Gas exchange in Alveoli
a) Each alveolus is only a single layer of epithelial cells through which gases can readily diffuse into interstitial fluid and blood capillaries.
b) The partial pressure gradients are sufficient to move oxygen in and carbon dioxide out of the blood, passively (oxygen has a higher pressure in the lungs than in the body, so it will diffuse towards the body).
c) Pulmonary surfactant is a secretion within the alveoli that reduces the surface tension to prevent collapse of the alveoli. (without it the lung would collapse)
C. Gas transport between blood and metabolically active tissues.
1) Blood (55% liquid) cannot carry sufficient dissolved oxygen and carbon dioxide that the body requires: hemoglobin (each molecule carries 4 oxygen’s) helps enhance its capacity.
2)
Oxygen Transport
a) Oxygen diffuses down a pressure gradient into the blood plasmaàto the red blood cellsà to the hemoglobin where it binds at a rate of four oxygen’s to one hemoglobin to make oxyhemoglobin.
b) Hemoglobin gives up it’s oxygen in tissues where partial pressure of oxygen is low, blood is warmer, and pH is lower: all three conditions occur in tissues with high metabolism.
3)
Carbon dioxide
Transport
a) Because carbon dioxide has a higher concentration in the body tissues, it diffuses into the blood.
b) Of the carbon dioxide in the body, Seven percent is dissolved in the plasma, 23% binds to hemoglobin (forming carbaminohemoglobin) and 70% is converted to bicarbonate , which is dissolved in the blood.
c) Bicarbonate and carbonic acid formation is enhanced by carbonic anhydrase, an enzyme located in the red blood cells.
6. Controls over gas Exchange. The nervous system regulates the rate and depth of breathing in order to maintain homeostasis of the concentrations of certain key variables (CO2 H+ and O2).
A. Gas exchange in the alveoli is most efficient when airflow equals the rate of blood flow.
B. Local chemical control.
1) When the rate of blood flow in the lungs is faster than the airflow, the bronchioles dilate to enhance the airflow and thus the rate of diffusion of the gases into the blood.
2) When the airflow is great relative to the blood flow, oxygen levels rise in the lungs and cause the blood vessels to dilate increasing blood flow.
1) The nervous system adjusts the contraction rate of the diaphragm and chest wall muscles.
a) A portion of the reticular formation in the medulla (brain) coordinates the signals for exhalation and inhalation this area is called the respiratory center
(1) These signals are sent automatically every 4 to 5 seconds (12 times a minute).
(2) This rate is maintained even when one is unconscious.
b) The pons fine-tunes the rhythmic contractions.
2) When breathing is deep and rapid, stretch receptors in the alveoli send signals to the brain control centers, which respond by inhibiting contraction of the diaphragm and rib muscles.
3) The brain monitors input from carbon dioxide sensors in the bloodstream and from receptors sensitive to decreases in oxygen partial pressure (carotid bodies and aortic bodies).
7. Respiration in unusual environments
A. Decompression sickness
1) Divers must take tanks of compressed air when they go below water.
2) They must surface slowly to prevent nitrogen bubbles in the blood. The “bends” and must also guard against nitrogen narcosis, where excess nitrogen dissolved in blood because of high pressure causes a drugged like state. "Hey man which way is the surface?"
1) Hypoxia occurs when tissues do not receive enough oxygen.
2) At high altitudes, the partial pressure of oxygen is lower than at sea level, so that hyperventilation may occur in order to receive that amount of oxygen the body needs.
3) It is dangerous to be in a room with a running automobile, carbon monoxide combines with hemoglobin 200 times faster than does oxygen: CO poisoning can result.
8. Disorders of the respiratory system: any condition that reduces air flow or gas exchange.
1) Symptoms include coughing while exercising, shortness of breath, wheezing and a sense of tightness in the chest.
2) Triggered by viruses, air particles, allergies and smoke.
3) Drugs that dilate the bronchi usually restore normal breathing.
4) Attacks can be fatal.
1) smoking is a major cause.
2) damage is permanent and patients usually need oxygen.
1) is usually temporary.
1) is a leading cause of death because it usually is a complication of many serious illnesses.
2) Most can be treated with antibiotics.
1) An inherited condition in which a single defective gene causes the mucous producing cells in the lungs to produce a thick sticky mucus.
2) Suffers are more susceptible to pneumonia.
3) Currently with physical therapy and antibiotic treatments these individuals can live until their mid 20's.
Possible assignments:
things to think about
1. Why
is the best body position for public speaking and singing a standing position
2. The
air at high altitudes is sometimes described in everyday language as thin. How does this translate in technical terms?
3. What
are the functions of sinuses?
1. During inspiration air moves across which series of structures:
A. Alveoli, bronchioles, trachea, pharynx, nasal cavities
B. Bronchioles pharynx, nasal cavities, alveoli
2. In the blood, oxygen is carried mainly by
3. In a process called blood packing, athletes will train at high altitudes in places like Denver, and store some of their blood. When they perform their event at lower altitudes, they will give themselves a transfusion with the blood made at high altitudes. What is the reasoning for this?
4. When you exhale
A) automatic and controlled by tissues in the lungs
B) Is
purely conscious and controlled by the brain
C) Is
a combination of automatic and conscious controls with a rhythm set by the
pons.
Answers to Multiple choice. 1) C, 2) C, 3)B, 4)A, 5)C
Some interesting Web pages
http://home.sprynet.com/sprynet/holtrun/altitude.htm
What information did you learn about this site?
The article discussed that it is impossible to work out extraneously at high altitudes because of the lack of oxygen. The site told of an experiment that found athletes could perform the best when they lived at high altitude and trained at low altitudes. This was because when they trained at low altitudes they had an excess of red blood cells and oxygen increasing their athletic ability. The article also mentioned that when women athletes lived and trained at low altitudes, and competed at high altitudes, there was a trend for the women to become anemic because they lacked the needed iron to produce the extra red blood cells that the need at high altitudes.