Respiratory Physiology Ventilation Gas exchange Oxygen uptake & utilization & removal of carbondioxide

From this study you should be able to: Describe the need to breath as a part of a metabolic process Describe the function of the respiratory conducting zone Describe pulmonary ventilation Briefly explain how surface tension arises & is stabilized Define lung volumes & lung capacities Explain gas movement during external & internal respiration Briefly describe neurological control of breathing with description of the stimulation of central chemoreceptor State the role of Haemoglobin in gas movement Explain how O 2 & CO 2 are carried in the blood

The Need to Breath  The Primary function of the respiratory system is to supply oxygen to the tissues of the body and to remove carbondioxide and to regulate acid base balance Oxygen helps us to release energy from food we eat Every cell in the body needs energy Glucose + Oxygen = Energy + Carbondioxide + water + Heat (ATP) From the atmosphere Waste products of energy production

Dealing with waste products Carbondioxide + water CO 2 plus H 2 O= COO + HHO H 2 CO 3 A weak acid substance CARBONIC ACID

Respiration Ventilation: Breathing. Gas exchange: Occurs between air and blood in the lungs. Occurs between blood and tissues. Oxygen (0 2 ) utilization: Cellular respiration and removal of carbondioxide

Respiratory System

9 The Larynx (voicebox) Extends from the level of the 4 th to the 6 th cervical vertebrae Attaches to hyoid bone superiorly Inferiorly is continuous with trachea (windpipe) Three functions: 1. Produces vocalizations (speech) 2. Provides an open airway (breathing) 3. Switching mechanism to route air and food into proper channels Closed during swallowing Open during breathing

10 Respiratory Mucosa Pseudostratified ciliated columnar epithelium Scattered goblet cells Underlying connective tissue lamina propria Mucous cells – secrete mucous Serous cells – secrete watery fluid with digestive enzymes, e.g. lysozyme Together all these produce a quart/day Dead junk is swallowed

Mucocilliary escalator

Covers most of the trachea, bronchi, bronchioles and nose- consists of goblet cells and ciliated columnar epithelium There is synchronous regular beating of cilia of the mucous membrane Wafts mucous and adhered particles (dust, bacteria etc) up towards the larynx Mucous is then expectorated or swallowed. Involved in non-specific immunity What happens in people who smoke?

The Pleura 2 layers- Visceral & Parietal. Intrapleural space -a film of fluid-secreted by the pleura & NO AIR The lungs remain in contact with the chest wall –allowing them to move with the thoracic cavity

Pleura

Pulmonary Ventilation: Inspiration and expiration

PRINCIPLE 1 Boyle’s Law Changes in intrapulmonary pressure occur as a result of changes in lung volume. (Pressure of gas is inversely proportional to its volume). Increase in lung volume decreases intrapulmonary (alveolar) pressure. Air goes in. Decrease in lung volume, raises intrapulmonary pressure above atmosphere. Air goes out.

Ventilation Breathing = “pulmonary ventilation” Pulmonary means related to the lungs Two phases Inspiration (inhalation) – air in Expiration (exhalation) – air out Mechanical forces cause the movement of air Gases always flow from higher pressure to lower 19

Quiet Inspiration - Process Contract your diaphragm, to achieve vertical expansion of your lungs. Contract your Intercostal Muscles, to increase thoracic volume laterally.

Muscles of respiration

Pressure changes on Quiet Inspiration Atmospheric pressure (at sea level) = 760 mmHg The chest expands (actively) Intrapulmonary press 757 mmHg so air moves into the lungs Pulmonary pressure rises by + 3 mm Hg.

Expiration Quiet expiration in healthy people is chiefly passive Inspiratory muscles relax Rib cage drops under force of gravity Relaxing diaphragm moves superiorly (up) Elastic fibers in lung recoil Volumes of thorax and lungs decrease simultaneously, increasing the pressure Air is forced out 23

Expiration Hold your breath- After stretching the lungs ( by contracting both diaphragm and thoracic muscles), the diaphragm and thoracic muscles relax & the thorax and lungs recoil The decrease in lung volume raises the pressure inside to above 763mmHg This is greater than atmospheric pressure- so air moves out of the lungs. Are your respiratory muscles getting tired?

Recap

Lung expansion

BOYLE’S LAW. THE RELATIONSHIP BETWEEN THE PRESSURE AND VOLUME OF GASES IS GIVEN BY BOYLE’S LAW. IT STATES THAT WHEN THE TEMPERATURE IS CONSTANT, THE PRESSURE OF A GAS VARIES INVERSELY WITH ITS VOLUME

Dead Space Air passes thro’ 150 ml of space before reaching the respiratory zone. Air is Warmed and humidified, Filters and cleaned: (Mucous traps particles ) Mucous moved by cilia to be expectorated.

Lung Volumes Tidal volume Volume of gas inspired/expired in an unforced breath Inspiratory reserve volume The maximum volume of air that can be inspired during forced breathing Expiratory reserve volume The maximum volume of gas that can be expired during forced breathing Residual volume The volume of gas remaining in the lungs after a maximum expiration

Lung Capacities Total lung capacity The total amount of gas in the lungs after a maximum inspiration Vital capacity The maximum amount of gas that can be expired after a maximum inspiration Inspiratory capacity The maximum amount of gas that can be inspired after a normal tidal expiration Functional residual capacity The amount of gas remaining in the lungs after a normal tidal expiration Peak Expiratory Flow Rate The maximum flow at the outset of forced expiration

Spirometry In obstructive lung disease, the FEV1 is reduced due to obstruction to air escape due to obstruction to air escape Thus, the FEV1/FVC ratio will be reduced.. A diagnosis of airflow obstruction can be made if the FEV1/FVC < 0.7 (i.e. 70%) and FEV1 < 80% predicted. (NICE 2004)

Respiratory Zone Where gas is exchanged between air and blood. Gas exchange occurs by diffusion.

Alveoli Clustered like a honeycomb. 300 million air sacs. Large surface area (60 – 80 m 2 ). Each alveolus is 1 cell thick. 2 types of cell: Alveolar type I: Structural cells. Alveolar type II: Secrete surfactant.

Lung alveoli and capillaries

Production of surfactant

Surface Tension a property of the surface of a liquid that allows it to resist an external force H 2 0 molecules at the surface are attracted to other H 2 0 molecules by attractive forces. What could happen to alveoli if this was not corrected? en.wikipedia.org/wiki/File:Amenbo_06f5520sx.jpg

Surfactant- reduces surface tension A phospholipid produced by alveolar type II cells. Function: Lowers surface tension. Think of a detergent Reduces attractive forces between H 2 0 molecules. As alveoli radius decreases, surfactant’s ability to lower surface tension increases- so the alveolus does not collapse

Principle 2 Gases move from an area of high concentration to an area of low concentration This movement is termed diffusion ( a passive process) Gas movement relies on concentration gradients

Diffusion of gases If I set off a stink bomb in the lecture theatre, those unfortunate to be near the front (an area of high concentration) would smell it. After a while the gases would attempt to fill the whole lecture theatre- the gases would diffuse from an area of high concentration to an area of low concentration (e.g. the back of the lecture theatre) when this occurs the molecules would be so far apart that no one would smell it.

Principle 3 Gas Exchange: Dalton’s Law Total pressure of a gas mixture is = to the sum of the pressures that each gas in the mixture would exert independently. Think of being in a crowded lift Now think of Partial Pressure

43 Diffusion Gradients of Respiratory Gases at Sea Level Total H 2 O O CO N Partial pressure (mmHg) % in Dry Alveolar Venous Gasdry air air air blood NB. CO 2 is ~20x more soluble than O 2 in blood => large amounts move into & out of the blood down a relatively small diffusion gradient.

44 PO 2 and PCO 2 in Blood

46 There are many diseases of the respiratory system, including asthma, cystic fibrosis, COPD (chronic obstructive pulmonary disease – with chronic bronchitis and/or emphysema) and epiglottitis example: normalemphysema

External Respiration

Haemoglobin and 0 2 Transport Each haemoglobin has 4 protein chains and 4 hemes. Each heme has 1 atom iron that can combine with an 0 2 molecule.

C0 2 transported in the blood: HC0 3 - (70%). Dissolved C0 2 (10%). Carbaminohemoglobin (20%). CO 2 is ~20x more soluble than O 2 in blood. There for large amounts of CO 2 move into & out of the blood more easity C0 2 Transport

Internal Respiration

Recap-Blood P 02 & P C02 P 02 in systemic veins is about 40 mm Hg. P C02 in systemic veins is 46 mm Hg. After gas exchange, Arterial blood P0 2 is normally about 100 mm Hg & P C02 is 40mm Hg

52 Peripheral chemoreceptors regulating respiration Aortic bodies * On aorta Send sensory information to medulla via vagus nerves Carotid bodies + At fork of common carotid artery * +

Regulation of Breathing Neurons in the medulla oblongata forms the rhythmicity center: Controls automatic breathing. Brain stem respiratory centers: Medulla. Pons.

Chemoreceptor Control C 02 + H 2 O H + cannot cross the blood brain barrier. C0 2 can cross the blood brain barrier and will form Carbonic acid & then H+ H+H+ H 2 C0 3 HC0 3 What is this?Bicarbonate H+ is the trigger for the chemoreceptors This is Carbonic acid

Clinical relevance point 1 Haemoglobin production controlled by erythropoietin. (Produced re P 02 delivery to kidneys). Loading/unloading of gas on Hb depends on: Hb level & capacity in the blood Enzymes: ↑ 2,3 DPG - increases unloading of O2 Temp: ↑Heat increases unloading of O2 Acid/base: ↓pH increases unloading of O2 This enzyme is produced when Hb is low

ANY QUESTIONS?

Questions What are the three functions of the respiratory system? In order, list all of the components of the respiratory system What is the function of epiglottis? What is the function of the cilia in the trachea? What surrounds the trachea and helps to keep it open? What is the role of surfactant in the lungs? What is the composition of air in %. Which law governs movement of gases in out of the lungs? A) Boyles law or b) process of diffusion Where are the chemo-receptors situated? How does the respiratory system respond to increase in CO 2 in the blood? In what form, can carbondioxide be carried in the blood? – see slide no 49 for answer In what form can Oxygen be carried in the blood? – see slide no 49 for answer What is the name of chemical produced by the kidneys which stimulates production of Red Blood Cells from Red Marrow?