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The Respiratory System
Paola GuevaraDaniela Chang
Kevin Gomez
Function Gas Exchange - allowing oxygen from the air to enter the
blood and carbon dioxide from the blood to exit into the air.
Inspiration (inhalation) and Expiration (breathing out)
-air is conducted toward or away from the lungs by a series of cavities, tubes and openings.
Four Respiratory Events
When working with the cardiovascular system, these events occur:
1. Pulmonary ventilation (breathing) - the entrance and exit of air into and out of lungs.
2. External respiration - the exchange of gases ( O2+CO2) between air and blood.
3. Internal respiration - the exchange of gases between blood and tissue fluid.
4. Transport of gases - to and from the lungs and the tissues.
Respiratory Tract
The Nose- The only external portion of the respiratory system Nostrils - air enters the nose through these
external openings Nasal cavities - narrow canals separated from one
another by a septum composed of bone and cartilage
Nasal Conchae – bony ridges that project laterally into the nasal cavity.
They increase the surface area for moistening and warming air during inhalation & for trapping water droplets during exhalation.
Nose cont.
Paranasal Sinuses – air-filled spaces that reduce the weight of the skull & act as resonating chambers of the voice
The tear (lacrimal) glands drain into the nasal cavities by way of tear ducts. This is why Tearing produces a runny nose.
Pharynx
- A funnel-shaped passageway that connects the nasal and oral cavities to the larynx.
- Also known as the THROAT.
3 parts of the Pharynx
Nasopharynx – where the nasal cavities open posterior to the soft palate
Oropharynx – where the oral cavity joins the pharynx
Laryngopharynx – which opens into the larynx
Pharynx cont. Pharyngeal tonsil (adenoids) – helps
defend against infection- Since inhaled air passes directly over
this tissue, it is used as a defense for breathing.
In the pharynx, the air passage and the food passage cross because of:
-the Larynx, which receives air, and the Esophagus, which receives food.
Larynx
- Composed of pure cartilage- Serves as a passageway for air between
the pharynx and the trachea- Known as the VOICE BOX because it
houses the Vocal Cords
Vocal Cords – mucosal folds supported by elastic ligaments
Glottis – the slit between the vocal cords which causes an opening
Larynx cont.- Larynx is the Adam’s apple for
males- When air is expelled past the
vocal cords through the Glottis, the vocal cords vibrate, producing sound.
- Therefore, the voice ‘breaks’ in young males due to his inability to control the longer vocal cords.
Epiglottis – A flap of elastic cartilage that prevents food from passing through the glottis into the larynx.
- After food is swallowed, the Larynx moves upward against the Epiglottis
Trachea- Commonly known as the WINDPIPE- A tube connecting the Larynx to the primary
bronchi- Lies ventral to the esophagus
Held open by C-shaped rings- The open part of the C-shaped rings forms the
anterior wall of the esophagus, which allows it to expand when swallowing
Trachea cont. THE BRONCHIAL TREE- The trachea divides into right and left primary bronchi.- The primary bronchi then branch into secondary
bronchi: one for each lobe of the lung- The right lung has 3 lobes, so there are 3 secondary
bronchi- The left lung has 2 lobes, so there are 2 secondary
bronchi. The left lung only has 2
because it needs to leave room for the heart.
Bronchiole – smallest conducting airways
The Lungs
- pair, coned-shaped organs of the body- Each lobe of the lung is divided in Lobules
& each lobule has a bronchiole supplying many alveoli.
- Pulmonary arteries travel alongside the bronchi & Pulmonary arterioles parallel the bronchioles.
Pulmonary Capillaries – surround and cover each alveolus of the lung
Lungs cont. Pleurae – double layer of serous
membrane that each lung is enclosed by.- Visceral Pleura – surface of the lung- Parietal Pleura – lines the inside of the
thoracic cavity- The pleurae produce a
lubricating serous fluid that reduces friction and allows the two layers to slide across one another.
Lungs cont. THE ALVEOLI- With each inhalation, air passes by
way of the bronchial tree to the alveoli.
- Gas exchange occurs between the air in the alveoli & the blood in the capillaries.
- Oxygen diffuses across the alveolar and capillary walls to enter the bloodstream, while Carbon Dioxide diffuses from the blood across these walls to enter the alveoli.
- The alveoli must stay open to receive the inhaled air if gas exchange is to occur.
Lungs cont.
Normal alveoli are lined with surfactant-a film of lipoprotein that lowers surface tension to an acceptable level.
- in healthy lungs surface tension is high enough to help the lungs recoil yet low enough to prevent the alveoli from collapsing.
Infant respiratory distress syndrome- the lung collapse in newborn babies who lack surfactant film.
Lungs cont.
Gas exchange occurs very rapidly because of the Respiratory membrane
Respiratory membrane- consists of the juxtaposed alveolar epithelium and the capillary endothelium.
Throughout most lungs their basement membranes are fused.
Lungs cont. The blood that enters the pulmonary
capillaries spreads thin.
Red blood cells within the capillaries are pressed up against narrow capillary walls, and little plasma is present.
-this facilitates the speed of gas exchange as it becomes a flattened sheet of muscle (simultaneously, the external intercostal muscles contract and the rib cage moves up and out.
Mechanism of Breathing
Ventilation› The lungs lie within the sealed-off thoracic
cavity.› The lungs adhere to the thoracic wall by
the way of the plurae.*Intrapleural pressure- the pressure
between the pleurae.
› A continuous column extends from the pharynx to the alveoli of the lungs.
Mechanism of Breathing cont…
Inspiration› The active phase of ventilation; this is the
phase in which the diaphragm and the external intercoastal muscles contract.
› When the diaphragm is relaxed, it has a dome shape, during inspiration, it contracts and becomes a flattened sheet of muscle. Simultaneously, the external intercoastal muscles contract, and the rib cage moves upward and outward.
Mechanism of Breathing cont…
Lung volume increases Air pressure from the alveoli decreases
creating a partial vacuum Air flow continues until intrapulmonary
pressure equals atmospheric pressure **air comes into the lungs because
they are already open, air doesn’t force the lungs open
Mechanism of Breathing cont… Expiration
› Passive phase of ventilation, no muscular effort is required to bring it about.
› The diaphragm resumes its dome shape and the rib cage moves down and in.
› As the volume of the thoracic cavity decreases, the lungs are free to recoil.
› The air pressure within the alveoli(intrapulmonary pressure) increases above atmospheric pressure.
Mechanism of Breathing cont…
› Air flow continues until intrapulmonary pressure equals atmospheric pressure.
› The presence of surfactant lowers the surface tension within the alveoli.
› As the lungs recoil, pressure between the two layers of pleura decreases, this also helps the alveoli stay open.
Mechanism of Breathing cont…
Maximum inspiratory involves the accessory muscles of respiration:› Erector spinae muscles of the back,
pectoralis minor (chest), and scalene and sternocleidomastoid muscles of the anterior neck.
› Their combined efforts can help increase the size of the thoracic cavity larger, allowing the maximum expansion of the lungs.
Mechanism of Breathing cont…
Forced expiration› Contraction of the internal intercostal
muscles can for force the rib cage to move downward and inward.
› The abdominal wall muscles contract, they push on the viscera, which push against the diaphragm, and the increased pressure in the thoracic cavity helps to expel air.
Mechanism of Breathing cont…
Respiratory volumes
Tidal volume: when relaxed, only a small amount of air. Only about 500ml.
Vital capacity: the maximum volume of air that can be moved in plus the maximum volume that can be moved out during a single breath.
Inspiration reserve volume: volume of air beyond the tidal volume by 2,900 ml.
Dead-space air: passages not used for gas exchange.
Residual volume: the remaining air after a very deep exhalation
Respiratory volumes
Control of ventilation› Primary respiration center located in the
medulla ablongata of the brain.› it automatically sends out motor nerve
signals by way of the phrenic nerve to the diaphragm. Simultaneously, the intercostal nerves stimulate the external intercostal muscles of the ribcage; the thoracic and lung volume increase, and the person inhales.
Nervous Input
Input from the brain influence the rate and depth of respiration.› Input from cerebral cortex, limbic system,
hypothalamus, and other brain centers account for the fact that rate and depth increase if on is:
-Angry-Frightened-Upset
Nervous Input cont…
Depth of respiration decrease in the soundest stages of sleep.
Nervous control over respiration also helps to protect delicate lung tissue.
Yet, how exactly does our body know when to stop inhaling/exhaling?
Chemical Input
The respiratory center is directly sensitive to the levels of carbon dioxide and hydrogen ions.
The center, however, is not affected directly by low oxygen levels.
We have carotid and aortic bodies located in the carotid arteries and aorta, respectively.
Chemical Input cont…
When the concentration of oxygen decreases, these bodies communicate with the respiratory center, and the rate of breathing increases.
Gas Exchange and Transport
Gas exchange and transport are critical to homeostasis
External Respiration: the exchange of gases in the lungs.› Gases are exchanged between the air in
the alveoli and the blood in the pulmonary capillaries.
› Blood that enters the pulmonary capillaries is dark maroon because it is Oxygen-poor.
External Resp. cont…
Once inspiration has occurred, the alveoli have a higher concentration of oxygen than does blood entering the lungs.
Gases exert pressure, and the amount of pressure each gas exerts is its partial pressure.
Gas Exchange and Transport
Oxygen is transported to the tissues in a combination with hemoglobin as oxyhemoglobin (HbO2).
Carbon dioxide is mainly carried to the lungs within the plasma as the bicarbonate ion (HCO3-).
Hemoglobin combines with hydrogen ions and becomes reduced.› This helps maintain the pH level of blood
Respiration and Health
A number of illnesses are associated with the respiratory tract. These disorders can be divided into those that affect the upper respiratory tract and those that affect the lower respiratory tract.
Well known infections include that of the:› Nasal cavities, sinuses, throat, tonsils, and
larynx.› Infection can spread from nasopharynx to ears
Respiration and Health Cont…
The lower respiratory tract is subject to infections such as:
-Acute Bronchitis-Pneumonia-Pulmonary tuberculosis
Respiration and Health Cont…
In restrictive pulmonary disorders, the lungs lose their elasticity
In obstructive pulmonary disorders the bronchi do not effectively conduct air to and from the lungs
Smoking, which is associated with chronic bronchitis, can lead to lung cancer.
Effects of Aging
All aspects of respiration decline with age
The elderly often die from pulmonary infections
Homeostasis
The respiratory system carries on two main functions:› Gas exchange which is essential to the
process of cellular respiration› Maintenance of blood pH
› The respiratory system helps maintain blood pressure by converting angiotensin I to angiotensin II
Homeostasis
The Respiratory system works with other parts of the body› The cardiovascular system transports
gases› Breathing helps the systemic venous blood
return to the heart› Respiratory tract assists defense against
pathogens by keeping the react clean of debris.
› Tonsils are lymphatic tissue where antigens are presented to T cells.
Homeostasis
The nervous system maintains rhythmic ventilation, and the sensory organs for olfaction are located in the nasal cavities.
The respiratory center responds to the increased gas exchange needs of the muscular system when we exercise
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