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