Chapter 19 Respiratory System

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Chapter 19 Respiratory System

• Air, Breathing and Other Important Things

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Respiratory System

• The function of the Respiratory system is gaseous
  exchange. It brings in O2 and rids the body of
  CO2.
• The process of Respiration is made up of several
  events
• Ventilation is the movement of gases into and out
  of the lungs.
• External Respiration is the exchange of gases
  between the lungs and the blood.
• Internal Respiration is the exchange of gases
  between the blood and the body cells.
• Cellular Respiration takes place as the body
  utilizes oxygen and produces carbon dioxide.

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Respiratory System

• Organs of the Respiratory System
• Nose this is the first and primary organ of air
  intake and output. The internal hairs exist to
  stop large particles from entering.
• Nasal Cavity The nasal cavity is divided into
  left and right portions by the nasal septum,
  which has bony and cartilaginous portions. It is
  also home to the nasal conchae (superior, middle,
  and inferior). These bony structures serve to
  turbulate the air as it enters the nasal cavity.
  This cavity is richly invested with
  pseudostratified ciliated epithelium that is
  richly invested with goblet cells. Mucous
  secreted by this tissue further serves to trap
  foreign particles, but also warms the incoming
  air and moisturizes it.
• Sinuses The sinuses are continuous with the
  nasal cavity, and are also lined with a mucous
  membrane. This mucous should drain into the
  nasal cavity and make its way to the stomach.
  The sinuses also reduce the weight of the skull.
  
• Pharynx this portion of the tract is divided
  into three regions described below. Parts of it
  are shared with the Digestive Tract.
• Nasopharynx
• Oropharynx
• Laryngopharynx

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Respiratory System

• Larynx The larynx houses the vocal cords
  (folds). The Epiglottis if found here. It is a
  flap of elastic cartilage that keeps the
  esophagus closed during breathing. The
  Epiglottis moves to cover the Trachea during
  swallowing of food or fluids. The Glottis is
  also found here it is an opening that allows for
  passage of air into the trachea.
• Trachea The trachea is also known as the
  windpipe. It is a flexible tube of that has
  C-shaped hyaline cartilage along most of its
  length. This cartilage serves to keep the
  trachea patent, thus maintaining the airway.
• Bronchial Tree This organ begins the branching
  that is responsible for ultimately getting oxygen
  down into the lung. The first branches are
  called the primary or mainstem bronchi.
  Filtration of air continues at this level and
  subsequent levels. Subsequent layers are
  numbered (secondary, tertiary, etc.). The
  smallest and terminal portion of this organ is
  called the Alveoli. This is the site of actual
  gaseous exchange and that exchange is
  accomplished via simple diffusion.
• Lungs The lungs are divided into lobes. The
  right lung has 3 lobes and the left lung has 2
  lobes. The lobes are sub-divided into lobules.
  Each lung has a hilus. This is the region on the
  medial aspect of the lung where the bronchi and
  the blood vessels enter and exit.

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Respiratory System

• Breathing Mechanisms
• The 2 major events of breathing are Inspiration
  and Expiration.
• Inspiration is an active process that requires
  the diaphragm to contract. The diaphragm is
  innervated by the Phrenic Nerves which arise from
  the Cervical Plexus. As the diaphragm contracts,
  it descends into the abdominal cavity, thereby
  decreasing the pressure in the thoracic cavity.
  This decrease in pressure in turns allows for the
  intake of air from the outside, where atmospheric
  pressure is usually higher.

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Respiratory System

• Expiration is a passive process caused by the
  relaxation of the diaphragm and the elastic
  recoil of the lungs. As the diaphragm relaxes
  and rises back into the thoracic cavity it causes
  an increase in the pressure in that cavity. This
  causes air to move out of the lungs.
• Surfactant is a lipoprotein secreted by the lungs
  in response to surface tension of water within
  the lung. Surfactant keeps the lungs from
  collapsing due to the moist inner surfaces coming
  into contact with each other. Lung collapse is
  called Atelectasis. Surfactant is secreted by
  simple cuboidal epithelium (Type II cells in the
  lungs).

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Respiratory System

• Respiratory Volumes
• The lungs will hold about 5800 ml of gas volume.
  This is often called Total Volume or Total Lung
  Capacity. This number can be divided into
  categories
• Tidal Volume about 500 ml of gases moved into
  and then out of the lungs during normal
  breathing.
• Inspiratory Reserve about 3000 ml of gas that
  can be forcibly inhaled over normal breathing.
• Expiratory Reserve about 1100 ml of gas that
  can be forcibly exhaled after normal breathing.
• Inspiratory Capacity about 3500 ml of air that
  can be inhaled after a normal exhalation.
• Vital Capacity about 4600 ml of air that can be
  exhaled after taking a maximal inhalation.
• Residual Volume about 1200 ml of gas that
  remains in the lungs at all times.

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Respiratory System

• Non-respiratory Air Movements
• Most of these air movements are a result of a
  reflex, although they may also be initiated
  voluntarily. Many of them are used to the clear
  the respiratory passages.
• Coughing this involves a rapid push of air from
  the lungs thru the partially closed glottis.
• Sneezing this involves a rapid push of air from
  the lungs thru the nasal passages.
• Laughing/Crying in these a person takes a
  breath and releases it in a series of short
  expirations.
• Yawning this reflex is often thought to help
  maintain alertness.

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Respiratory System

• Control of breathing is goverened by the
  Respiratory Center in the brainstem. It controls
  both the rate and depth of breathing.
• Hyperventilation is a situation where a person
  breathes too fast (greater than 20 ventilations
  per minute). This increases blood O2 and
  decreases CO2.

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Respiratory System

• Gas Exchange
• The Alveoli are the all important site of gaseous
  exchange. Without these microscopic air sacs
  functioning properly death is usually very swift
  in coming. Each alveolus consists of a tiny
  space surrounded by a thin wall that separates it
  from adjacent alveoli. This wall is primarily
  made up of simple squamous epithelium (Type I
  cells).
• Thus the Respiratory Membrane is made up of two
  layers of epithelium separated by a basement
  membrane.

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Respiratory System

• Movement of gases thru the respiratory membrane
  is accomplished via simple diffusion. Blood
  entering the capillary layer of the lungs in low
  in oxygen and rich in carbon dioxide. As blood
  passes thru the capillary layer it comes in very
  close proximity to the alveolus. This proximity
  allows for the rapid diffusion of carbon dioxide
  out of the blood stream into the alveolar space,
  and for the diffusion of oxygen out of the
  alveolar space into the blood stream.
• Once oxygen is in the blood stream it binds with
  hemoglobin on a RBC and is take to the awaiting
  body cells for use. Once the carbon dioxide is
  in the alveolar space, it makes its way out of
  the body via the respiratory tract.

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Respiratory System

• Oxygen transport is accomplished in hemoglobin
  because oxygen binds easily to the iron in the
  globular protein. About 98 of all oxygen is
  transported this way. The rest is dissolved in
  plasma.
• Once oxygen is so bound to the hemoglobin
  molecule, the new combined substance is called
  Oxyhemoglobin. Each hemoglobin molecule can
  carry up to four oxygen molecules.
• The bond between oxygen and hemoglobin is
  relatively unstable and break easily when oxygen
  enters an area where it is able to easily diffuse
  out of the blood stream.

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• Carbon Dioxide Transport is accomplished in one
  of three forms
• Dissolved in plasma. Only about 7 or so is
  transported in this form.
• Bound to hemoglobin as Carbaminohemoglobin. CO2
  binds with the amine groups on the hemoglobin,
  thus CO2 and O2 do not compete for binding sites.
  About 15 to 25 of CO2 is transported in this
  way.
• As a Bicarbonate ion. Bicarbonate ion
  dissociates in water to form carbonic acid. This
  is an important mechanism in the transport of
  this gas as it plays a role in the buffer system
  of the blood.

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• Smoking of any kind is bad for your health.
  Cigarette smoking is particularly BAD as it is
  simultaneously addictive and destructive and
  corruptive.
• The addictive properties of cigarettes (and some
  other forms of tobacco) are fairly well
  documented. Very few people dispute this other
  than those who make a living from the sale of
  tobacco products.
• The destructive properties of smoking can be most
  clearly seen in the lungs where tissue is
  literally lost in the making of several types of
  C.O.P.D.s.
• The corruptive properties lie in the formation of
  cancerous cells.
• Please note this last item!!! The diseases and
  degenerative conditions seen in a smoker (i.e.
  metastatic lung cancer and emphysema) are RARELY
  ever seen in non-smokers. Most people will live
  their entire life and not be at any significant
  risk of these diseases. This statement is made
  not out of personal opinion or preference, but
  from what is broadly considered to be very basic
  and simple science.

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