ANA 2 - MOD 7 - RESPIRATORY SYSTEM

Respiration

exchange of O2 and CO2 between atmosphere, blood, and cells

External Respiration

• gas exchange between the air in the lungs and the blood

Internal Respiration

• gas exchange between the blood and the tissues

VENTILATION

• the movement of air into and out of the lungs

• Upper Respiratory Tract

• external nose, nasal cavity,

  pharynx, larynx

Lower Respiratory Tract

• trachea, the bronchi and smaller

  bronchioles, and the lungs

Conducting zone

• exclusively for air movement and

  extends from the nose to the bronchioles

Respiratory zone

• within the lungs and is where gas

  exchange between air and blood takes place

Nose

• consists of the external nose and nasal cavity

External Nose

• hyaline cartilage plates, nasal bones, extensions of frontal and maxillary bone

Nasal Cavity

• passageway of air

External Nares (nostrils)

• external openings

Internal Nares/Choanae

• openings into the pharynx

Vestibule

• anterior part of nasal cavity, lined with

  stratified squamous with coarse hairs called vibrissae

Hard Palate

• formed by maxilla and palatine bone

• separates the nasal cavity from the oral cavity

Nasal septum

• partition dividing the nasal cavity into right and left parts
  

Cartilage

• Anterior to nasal septum?

Vomer and ethmoid bone

• Posterior to Nasal Septum

Conchae

• three bony ridges that modify the lateral walls of nasal cavity

Paranasal Sinuses

• contribute to the humidifying of the inspired air. They also reduce the weight of the skull.

Pharynx

• Common opening of both the digestive and the

respiratory systems

Nasopharynx

• located posterior to the choanae and superior to the soft palate; opens into two auditory tubes

Soft Palate

• an incomplete muscle and connective tissue partition separating the nasopharynx from the oropharynx

• prevents swallowed materials from entering the nasopharynx and nasal cavity

Uvula

• posterior extension of soft palate

Pharyngeal tonsils

• helps defend the body against infection

Oropharynx

• extends from the soft palate to the epiglottis

Laryngopharynx

• extends from the tip of the epiglottis to the esophagus and passes posterior to the larynx

Larynx

• “Voice box”

• Located between C4-C6.

• It is a passageway for air between the pharynx and the

  trachea

• Consists of an outer casing of nine cartilages connected

  to one another by muscles and ligaments

Arytenoid Cartilage

Corniculate Cartilage

Cuneiform Cartilage

What are the 3 Paired Cartilages?

Thyroid Cartilage (adam’s apple; largest)
Epiglottis Cartilage

Cricoid Cartilage

What are the 3 unpaired cartilage?

Vestibular folds

• false vocal cords

Vocal folds

• true vocal cords

Glottis

• opening between the vocal folds

Trachea

• “Windpipe”

• It consists of dense regular connective tissue and

  smooth muscle reinforced with 15–20 C-shaped pieces

  of hyaline cartilage.

• The posterior wall of the trachea is devoid of cartilage

• Esophagus lies immediately posterior to the cartilage free posterior wall

• Diameter of 12 mm and a length of 10–12 cm, descending from the larynx (C6)to the level of the level of carina (T4-T5)

Trachealis Muscle

• contraction of this smooth muscle narrows the diameter of trachea

Goblet Cells

Lined by pseudostratified ciliated columnar epithelium with numerous _____?

Main or primary Bronchi

The trachea divides to form two smaller tubes called _______ or _______?

Carina

• most inferior tracheal cartilage. Bifurcates the openings into the bronchi

o Sensitive to mechanical stimulation
o Can stimulate a powerful cough reflex

TRACHEOBRONCHIAL TREE

• Trachea divided into (R) main bronchus and (L) main bronchus

• Difference between two?
  • Approximately 16 generations of branching occur from the trachea to the terminal bronchioles
  • Main bronchi (primary bronchi) - lobar bronchi (secondary bronchi) - segmental bronchi (tertiary bronchi) - subsegmental bronchi - bronchioles - terminal bronchioles
  

Lungs

• The principal organs of respiration small, air-filled

  chambers where gas exchange between the air and blood takes place

• Conical in shape, with its base resting on the diaphragm and its apex extending to a point approximately 2.5 cm superior to the clavicle

• The lungs are attached to the mediastinum by the roots of the lungs – arrangement: pulmonary artery, superior and inferior pulmonary veins, main bronchus

Hilum

• is a region on the medial surface of the lung

• main bronchus, blood vessels, nerves, and lymphatic vessels, enter or exit the lung

Right Lung

Left Lung

Alveoli

• The terminal bronchioles divide to form respiratory

  bronchioles, which give rise to alveolar ducts, and end as two or three alveolar sacs which are chambers connected to two or more alveoli

• Small, air-filled chambers where gas exchange between the air and blood takes place

• Approximately 300 million alveoli are in the two lungs

• Contains elastic fibers – allow alveoli to expand during

  inspiration and recoil during expiration

• Lungs retain some air even not inflated, which gives

  them a spongy quality

• the epithelium of the alveoli and respiratory bronchioles

  is not ciliated - debris from the air removed by

  macrophages

Type I PNEUMOCYTES

Type II PNEUMOCYTES

Two types of cells from the alveolar wall?

Type I pneumocytes

• are thin squamous epithelial cells that form 90% of the alveolar surface; where most of the gas exchange between alveolar air and the blood takes place

Type II pneumocytes

• produce surfactant, which makes it easier for the alveoli to expand during inspiration

RESPIRATORY MEMBRANE

• It is where gas exchange between the air and blood takes place

• It is formed mainly by the alveolar walls and surrounding pulmonary capillaries

The respiratory membrane is very thin to facilitate diffusion of gases. It consists of several layers:

1. A thin layer of fluid lining the alveolus

2. The alveolar epithelium composed of simple squamous

   epithelium

3. The basement membrane of the alveolar epithelium

4. A thin interstitial space

5. The basement membrane of the capillary endothelium

6. The capillary endothelium, composed of simple

   squamous epithelium

1. Thickness of the membrane – increases as a result of

   edema in the interstitial space in the alveoli

2. Surface area of the membrane – usually decreases in

   emphysema

3. Diffusion coefficient of the gas – depends on gas

   solubility membrane

4. Partial pressure difference of gas between two sides of the membrane

Factors affecting rate of gas diffusion

Diaphragm

• The ______ is dome-shaped, and the base of the

  dome attaches to the inner circumference of the inferior thoracic cage

Central Tendon

• Located at the top of the dome is a flat sheet of

  connective tissue called the ___________

Diaphragm

• Contraction of the ______ results in inferior movement of the central tendon resulting to a normal quiet inspiration

Inferior

• Contraction of the diaphragm results in _____ movement of the central tendon resulting to a normal quiet inspiration

Two-Thirds

• Responsible for approximately _______ of the increase in thoracic volume during inspiration

INSPIRATION

EXPIRATION

Lung Pleura

• each lung is surrounded by a separate pleural cavity formed by the pleural serous membranes

Parietal Pleura

• covers the inner thoracic wall, the superior surface of the diaphragm, and the mediastinum
  

Visceral Pleura

• covers the surface of the lung. At the hilum, the parietal pleura is continuous with the visceral pleura
  

Pleural Fluid

• acts as lubricant, holds the parietal and visceral membranes together

Pleural Pressure

• Is the pressure in the pleural cavity, the thin space

  between the lung pleura and the chest wall pleura

• When pleural pressure is less than intra-alveolar pressure,

  the alveoli tend to expand.

• In a normal individual, the alveoli are always expanded. This is because there is a negative pleural pressure that is lower than intra-alveolar pressure

Pleural Pressure

• amount of suction required to hold the lungs open is -5 cm H2O

Inspiration

• pressure of -7.5 cm H2O expansion of chest cage
  

Expiration

• Reversed

• Goes back to -5 cm H2O

Alveolar Pressure

• Pressure of air inside the lung alveoli when no air flows in and out of the lungs

• Pressure is equal to the atmospheric pressure of 0 cm H2O

Inspiration

• alveolar pressure falls below atmospheric pressure (-1 cm H2O) enough to pull 0.5l of air in the lungs

Expiration

• alveolar pressure rises to +1 cm H2O forces inspired air to expel

Recoil Pressure

• the difference between intra-alveolar pressure and

  pleural pressure

• measure of elastic forces of the lungs at each instant of respiration, called the _________

Compliance of Lungs

• extent to which lungs will expand for each unit increase

  in transpulmonary pressure

• Total compliance: 200 mm of air/cm of transpulmonary

  pressure (every 1 cm of H2O increase in transpulmonary

  pressure, lung volume increases)

• Determined by:

• elastic forces of lung tissue (elastin and collagen)

• elastic forces cause by surface tension of fluid lining inside the alveolar walls

Surfactant

• surface active agent in water – greatly reduces surface tension of water

• secreted type II alveolar epithelial cells

• complex mixture of phospholipids, proteins, and ion

• Produced as early as 6 to 7 months of gestation

• Most important components:

o Dipalmitoyl phosphatidylcholine o surface apoproteins
o calcium ions

• The smaller the alveolus, the greater the alveolar pressure caused by the surface tension

Pump-Handle Motion

• Forward and upward movement of the sternum and upper ribs (Ribs 1-6)

• Increase in AP dimension
  

Bucket Handle Motion

• elevation and outward turning of the lateral (midshaft) portions of the ribs (Ribs 7-10)

• Increase in lateral dimension

Caliper Motion

• lower ribs (8-12) flare and open outward

• Increase in subcostal angle

Piston Action

• central tendon of the diaphragm descends as the muscle contracts

• Increase in vertical dimension

Automatic Breathing

• by medullary respiratory center in the

• brainstem, which is responsible for the rhythmicity of breathing
  

Voluntary Respiration

• by cerebral cortex, which sends

• impulses directly to the motor neurons of respiratory muscles.
  

Respiratory Center

• Reticular formation

• Sets and controls the rate and rhythm of breathing

• If the pons act alone, breathing is stronger and more effective

Pneumotaxic Center (Pontine respiratory group)

• Located dorsally in the upper pons

• Inhibits inspiration; “switches off” the inspiratory ramp signal to control the filling phase

• Controls rate and depth of breathing

• Controlled by nucleus parabrachialis/nucleus proprius

Apneustic Center

• Located in the lower pons

• Prolongs inspiration: reverts switching off of the inspiratory ramp

Major Respiratory Control

• Automatic respiratory center – Sets the inherent rhythmicity of breathing

• If the medulla acts alone, breathing is weak and irregular

Dorsal Respiratory Group

• Located dorsally in the medulla
  “Rhythm generator”

• Plays a fundamental role in causing inspiration Controlled by nucleus of tractus solitarius (solitary tract)

Ventral Respiratory Group

• Located in the ventrolateral part of the medulla

• Controls expiration > inspiration

• Controlled by nucleus ambiguus

Central Chemoreceptors

• sensitive changes either in Carbon Dioxide or Hydrogen ion levels or arterial blood

Peripheral Chemoreceptors

• Sensitive to partial pressure of oxygen in the arterial blood

Effects of Carbon Dioxide

• Small increase in CO2 triggers large increase in rate and depth of ventilation

• Chemoreceptors activity: medulla>carotid and aortic

  bodies

Effects of Oxygen

• Measured as PaO2 (partial pressure of oxygen)

• Chemoreceptors in carotid and aortic bodies

• small changes in Po2 do not cause changes in

  respiratory rate.

Hering-Breuer Reflex

• limits the degree to which inspiration proceeds and

  prevents over inflation of the lungs

• It depends on stretch receptors in the walls of the

  bronchi and bronchioles of the lungs

• The action potentials have an inhibitory influence on the respiratory center and result in expiration

• In adults, the reflex is important only when the tidal

  volume is large, such as during exercise.

Dead Space

• The part of the respiratory system where gas exchange does not take place

Anatomical Dead Space

• 150ml

• Formed by the nasal cavity, pharynx, larynx,

  trachea, bronchi, bronchioles, and terminal

  bronchioles.
  

Physiological dead space

• anatomical dead space plus the volume of any alveoli in which gas exchange is less than normal (under perfused or malfunctioning)

Ventilation/Perfusion Ratio

• Equal amounts of air (ventilation) and blood (perfusion) needs to be in the same place at the same time for gas exchange to occur

0.8 mL

Normal Value of Ventilation/Perfusion Ratio?

Dead Space

• well ventilated, decreased perfusion (high V/Q)

Shunt

• well perfusion, decreased ventilation (low)

• No ventilation, but blood flow continues.

Sneeze and Cough Reflex

• Both reflexes dislodge foreign matter or irritating material from the respiratory passages

SNEEZE REFLEX

• occurs in the nasal passages

• the soft palate is depressed, so that air is directed primarily through the nasal passages, although a considerable amount passes through the oral cavity. The rapidly flowing air dislodges particulate matter from the nasal passages and can propel it a considerable distance from the nose.

Photic sneeze reflex

• 17-25% of population

• stimulated by exposure to bright light, such as the

  sun.
  

COUGH REFLEX

• Approximately 2.5 L of air are inspired

• The vestibular and vocal folds close tightly to trap the inspired air in the lungsàthe abdominal muscles contract to force the abdominal contents up against the diaphragm and the muscles of expiration contract forcefully.àthe pressure in the lungs increases to 100 mm Hg or moreàthe vestibular and vocal folds open suddenly, the soft palate is elevatedàair rushes from the lungs and out the oral cavity at a high velocity, carrying foreign particles with it

  o A forced expiration against a closed glottis

Minute Ventilation

• is the total amount of air moved into and out of the respiratory system each minute

• It is equal to the tidal volume times the respiratory

  rate (RR X TV)

• minute ventilation averages approximately 6 L/min