The Respiratory System

Functions of the Respiratory System Gas exchanger Air goes to blood Blood goes to cells Air distributor Other functions Humidification Filtering Phonation Warming Control of pH Olfaction

Respiratory System Primary function – Gas exchange: to obtain oxygen and remove carbon dioxide. Cells require oxygen to break down nutrients to release energy and produce ATP = Cellular Respiration Cells must excrete carbon dioxide that results from cellular respiration.

Cellular Respiration - Review C6H12O6 (aq) + 6 O2 (g) → 6 CO2 (g) + 6 H2O (l) Without O2, a cell can only undergo fermentation, resulting in a net gain of only 2 ATP for the cell. Why would this be a problem? The result of cellular respiration is carbon dioxide and water. This carbon dioxide enters the blood stream and there it has various functions, including: Regulation of blood pH Haldane Effect Bohr Effect Autoregulation of blood supply to tissues

Cellular Respiration Therefore it is incredibly important that cellular respiration takes place, in a timely manner, throughout the body. When O2 levels are limited, cellular respiration activity slows down and the body reverts to fermentation. What are the results of fermentation? The respiratory system allows for gas exchange between the air and blood in the body to occur, resulting in an intake of oxygen from the atmosphere.

Introduction to Respiration Respiration – gas exchange between atmosphere and cells. Ventilation – movement of air into and out of lungs. Gas exchange between blood and air in lungs = external respiration. Gas transport in blood between lungs and body cells. Gas exchange between blood and cells = internal respiration. Cellular respiration – process of oxygen utilization and carbon dioxide production at the cellular level.

Organs Involved Upper Respiratory Tract Lower Repsiratory Tract Nose Nasopharynx Oropharynx Laryngopharynx Larynx Lower Repsiratory Tract 1. Trachea 2. Bronchial Tree 3. Lungs

The Nose Protrudes from face Openings called nares Ala are cartilage rings or flares at nares Floor made of palatine and maxilla Roof formed by ethmoid Septum made of cartilage and bone (perpendicular plate of ethmoid and vomer) Lined with mucosa Meatuses formed cavities

Functions of the Nose Passageway – filters, warms, moistens and chemically examines air Smell Phonation Paranasal sinuses – air filled spaces that reduce weight of skull and affect quality of voice.

The Nose Nostrils (nares) – are where air enters and leaves nasal cavity. Nasal cavity – hollow space behind nose Nasal conchae – bones that divide nasal passageway. These support the nasal cavity and increase surface area. Why is this important? Help in nasal congestion in response to climatic changes and needs of the body. Mucous membrane – epithelium rich in mucous-secreting goblet cells that trap dust and other particles. How would this aid the respiratory system?

Pharynx (throat) Made of muscle and mucous lining into 3 divisions Nasopharynx – posterior nares to soft palate Oropharynx – soft palate to hyoid bone; adenoid tonsils Laryngopharynx – hyoid bone to esophagus; palatine and lingual tonsils

The Larynx Enlargement in airway. Houses vocal cords. Upper end of trachea 3-6th cervical vertebrae Made of 9 pieces of cartilage in shape of box. Thyroid muscle – called “Adam’s apple” Glottis – opening between vocal cords. Triangular slit. Present during normal breathing. Muscles close glottis when eating or drinking. Why would this be important? Prevent food and liquid from entering trachea.

The Larynx Epiglottis – lid. Muscle that allows air into larynx. Closes during eating. Why? Arytenoids – hold vocal cords Vocal cords – fibroelastic bands stretched across hollow interior Males is larger with less fat Function to produce voice (pitch determined by length and tension in cords) Changing the shape of the pharynx and oral cavity and using the tongue and lips transform sounds waves to words.

The Trachea “Windpipe” – flexible tube lined with ciliated mucous membrane tissue. Made of smooth muscle Contains “C” shaped rings of cartilage 4.5 inches long Provides passageway to and from lungs Splits into left and right bronchi.

Bronchi Made similar to trachea but complete rings Branched into primary, secondary bronchi, bronchioles, alveolar ducts, alveoli Provide passageways and alveoli provide gas exchange surface

Bronchial tree Branched airways leading from the trachea to the air sacs in the lungs. Left and right bronchi, divide into primary, secondary… Bronchioles – terminal bronchioles, smaller tubes. Lack cartilage. Alveoli – air sacs in lungs connected to the capillary network. Provide large surface area. Why is the large surface area important for alveoli? O2 diffuses through cell walls into blood Co2 diffuses through blood into cell walls.

Alveoli Alveolar ducts are very thin ducts that connect the terminal bronchioles to the alveolar sacs. Alveoli lie within the capillary network. Two adult lungs have about 300 million alveoli, providing a surface area nearly half the size of a tennis court.

Lungs 3 lobes in Rt. Lung and 2 in the left. Therefore R lung larger than the left. Root of lung consists of primary bronchus and pulmonary arteries and veins Function is to provide rapid exchange of gases. Lobes connected to lymphatic system, blood vessels, air passages, nerves, and connective tissue.

Respiratory Mucosa Lining of entire respiratory system Makes mucous (sputum) Mucous will help clean and filter Make about 125 mL daily Moves about 1 to 2 cm per minute from lower respiratory tract to oropharynx Swallow or spit out

Quiz Time! Very short quiz over anatomy and some functions of the respiratory system.

Breathing Mechanisms Inspiration – inhalation Atmospheric pressure, due to weight of air, is the force that moves air into lungs. At sea level, the atmospheric pressure is sufficient to support a column of mercury about 760 mm high in a tube. Therefore, normal air pressure = 760 mmHg. Normal, resting inspiration – if pressure inside lungs and alveoli decreases, atmospheric pressure will push outside air in.

Normal, quiet Inspiration Diaphragm contraction (result of impulse from phrenic nerves)  diaphragm moving down. Increase in vertical diameter of thorax Increase in transverse diameter of thorax Alveoli air pressure decreases about 2-3 mmHg less than atmospheric pressure. Expansion of lungs – cohesion of visceral and parietal pleuras Air enters lungs = inspiration.

Normal, quiet Expiration Expiration – exhalation Force comes from elastic recoil of tissues and surface tension (attraction of H2O molecules that make it difficult for alveoli to inflate) Passive process Relaxation of inspiratory muscles Decrease in size of thorax – elastic recoil of lung tissue Increase in intrathoracic pressure Decrease in size of lungs Increase in alveolar pressure from about -3mm of Hg to +3 or +4 mm Hg (Pressure and volume in inverse relationship) Air moves out of lungs – expiration

Respiratory Volumes Respiratory Cycle – 1 inspiration and following expiration. Tidal Volume – volume that enters during 1 resp. cycle Resting Tidal volume – about 500 mL of air. Inspiratory reserve volume (IRV) – During forced inspiration, air in addition to resting tidal volume can enter lungs. This maxes out at about 3,000 mL of air. Expiratory reserve volume (ERV) – lungs can forcefully expel about 1,100 mL more than resting tidal volume. Residual volume – amount always in lungs = 1,200 mL.

Respiratory Volumes Because of the residual volume, new air inhaled mixes with old air in the lungs. This is very important as it prevents the concentration of O2 and CO2 in the lungs from fluctuating much during respiration. Why would this be important? CH3CH2OH(g) + O2(g) -> HC2H3O2(g) + H2O(l) Ethyl alcohol and oxygen to acetic acid and water. The breathalyzer. No way around it!

Respiratory Capacities When two or more volumes are combined. Vital Capacity – tidal volume + ERV + IRV = 4,600 mL. Maximum air during deepest breath possible. Inspiratory Capacity – Tidal volume + IRV = 3,500 mL. Maximum amount a person can inhale after resting expiration. Functional residual capacity – ERV + Residual volume = 2,300 mL. Volume of air in lungs after resting exp. Total lung capacity – vital capacity + residual volume = 5,800 mL. Varies with age, sex and body size.

The didgeridoo Wind instrument developed by Aborigines in Australia over 1,500 years ago. Often considered world’s oldest wind instrument. Termite-bored branches are often used to make these instruments. Vibrations produced by the player’s lips and the strength of the vocal tract influence the timbre of the sound. The technique of circular breathing can help.

Gas Exchange Respiratory membrane – walls of alveoli exchange gas between blood and air. Gases diffuse from regions of high pressure to regions of low pressure. Air = 78% N, 21% O, 0.04% CO2 Partial pressure – amount of pressure each gas contributes to its concentration. O2 = 160 mmHG (21% of 760 mmHg) Gas diffuses into liquid - O2 into blood. Another example: CO2 into coca cola.

Gas Exchange Follow partial pressure gradients. Each gas diffuses between blood and its surroundings from areas of higher partial pressure to areas of lower partial pressure until the partial pressures in the two regions reach equilibrium. PO2is alveoli is 105 mm of Hg while in the blood it is only 40 mmHg. Thus O2 diffuses from the alveolar air into the blood. PCO2 is 45 mmHg in blood but only 40 mmHg in alveolar air. Therefore CO2 diffuses from the blood into the alveoli.

Oxygen Transport

Oxygen Transport 98% of O2 binds with iron group of hemoglobin. 2% dissolves in plasma. In lungs, combines with hemoglobin  oxyhemoglobin. This is an unstable bond and as PO2 decreases, oxygen releases and diffuses into cell to be used in cellular respiration. More O2 is released from oxyhemoglobin when [CO2] is high, when blood pH is low, and when blood temperature is high. When might these conditions occur? Exercise, when more O2 is released to the muscles.

Carbon Dioxide Transport Tissues have relatively high PCO2 to blood, so CO2 rapidly diffuses into blood. Blood transports CO2 to lungs as CO2 in plasma, bonded to hemoglobin, or as bicarbonate ion (HCO3-) CO2 bonds with the amino group of hemoglobin forming carbaminohemoglobin, which decomposes in areas of low PCO2 releasing carbon dioxide. Do you think it’s possible for both O2 and CO2 to be bound to hemoglobin at the same time? Yes! CO2 binds to the amino group while O2 binds to the iron group of hemoglobin. Some exceptions…

Bohr Shift At lower pH (more acidic environment), hemoglobin will bind to oxygen with less affinity = Bohr Shift That is, oxygen is more likely to be released from oxyhemoglobin in a more acidic environment. In RBCs carbonic acid (H2CO3) dissociates into protons (H+) and bicarbonate ions (HCO3-). Since CO2 is in direct equilibrium with the concentration of protons in the blood, increasing CO2 levels leads to a decreases in pH  Bohr Shift.

Haldane Effect Related to the Bohr Shift is the Haldane Effect, which is the phenomenon in which oxygenated blood has a reduced capacity for hemoglobin to carry carbon dioxide and vice versa.

Quiz Time! A short quiz over physiology and gas exchange in the respiratory system