Respiratory System

Cellular Respiration Most cells utilize cellular respiration to convert the chemical energy stored in nutrient macromolecules to the chemical energy utilized by cells  ATP This process is an oxidation reaction  a steady supply of oxygen is required to combust glucose to carbon dioxide and water

Cellular Respiration

Respiratory systems support cellular respiration by facilitating gas exchange of oxygen and carbon dioxide between the organism and the environment

Evolution of Respiratory Systems 1.Simple Diffusion – gases are exchanged across the moist exterior surface of the organism’s body e.g. single cell organisms; sponges; cnidaria; and worms 2.Gills – large surface areas that are richly supplied with blood capillaries are in close contact with water containing dissolved gases e.g. some mollusks and crustacea; and fish

Evolution of Respiratory Systems 3.Book Lungs – a series of moist, page-like membranes within a chamber of the organism that facilitate gas exchange e.g. spiders and scorpions 4.Tracheae – system of highly branched tubes that extend from the exterior surface of the organism to every cell in its’ body e.g. insects

Book Lungs

Evolution of Respiratory Systems 5.Lungs – chambers containing moist, delicate respiratory surfaces that are protected within the body e.g. amphibia through to mammals

Human Respiratory System Four distinct stages in respiration: 1.Breathing – entrance and exit of air into and out of lungs 2.External respiration – gas exchange between air and blood 3.Internal respiration – gas exchange between blood and body cells 4.Cellular respiration – in body cells

Human Respiratory System The human respiratory system consists of two distinct parts: 1.Conducting portion – a series of passageways that carry air by bulk flow into the gas exchange portion 2.Gas exchange portion – membraneous sacs where gases are exchanged between air in sacs and blood in capillaries

Conducting Portion Purpose – to carry air to the respiratory membranes in the lungs 1.Nose  Nasal cavity  Pharynx, or Mouth  Oral cavity  Pharynx (common chamber) 2.Pharynx  Larynx (contain vocal cords) 3.Larynx  Trachea (rings of cartilage) 4.Trachea  Left or Right Bronchus 5.Bronchus  Bronchioles 6.Bronchioles  Alveoli (singular : alveolus)

The Lungs Paired, cone shaped organs that lie on either side of the heart in the thoracic cavity Right lung has 3 lobes, the left lung has 2 lobes (allowing room for the heart) Bronchus, bronchioles and alveoli are contained in each lung

Conducting Portion As air travels through the conducting portion, it is: 1.Warmed 2.Moistened 3.Filtered by mucus and cilia (tiny hairs) that line the conducting portion

Gas Exchange Portion - Alveolus Each lung contains approximately 300 million alveoli Individual alveoli are tiny – 0.2 mm diameter – but collectively the alveoli provide 70 square meters of surface area for gas exchange This surface area is the size of a tennis court, and is 40x the surface area of your skin

Alveolus The alveoli cluster together at the end of a bronchiole like a cluster of grapes The cluster of alveoli are surrounded by an intricate network of blood capillaries Because the alveolus is only one cell layer thick, and the blood capillary is one cell layer thick, gases are able to move by diffusion between our blood and the air we breathe in This diffusion of gases is facilitated by a thin layer of water that coats the interior surface of each alveolus

Gas Exchange: External Respiration 1.High CO 2 / low O 2 blood is pumped from the right ventricle of the heart, through the pulmonary arteries, to the capillaries that surround each alveolus 2.The air in the alveoli is high in oxygen, so oxygen moves by diffusion into the blood of the alveolar capillaries 3.The blood in the lung capillaries is high in carbon dioxide, so carbon dioxide moves by diffusion into the alveoli sacs 4.High O 2 / low CO 2 blood leaves the alveolar capillaries, through the pulmonary vein, to the left atrium of the heart

Gas Exchange: Internal Respiration 1.The left ventricle pumps high O 2 / low CO 2 blood along the aorta and arteries to the capillaries that are in contact with individual cells 2.The blood in the body capillaries has more oxygen than the body cells, so oxygen diffuses from the blood into the body cells 3.The body cells have more carbon dioxide than the blood, so carbon dioxide diffuses from the body cells into the blood in the body capillaries 4.High CO 2 / low O 2 blood leaves the body capillaries, travels through veins and the vena cava to the right atrium

Chemistry of Gas Exchange Oxygen <5% of oxygen travels in blood as a dissolved gas >95% of oxygen travels in blood attached to hemoglobin (oxyhemoglobin) Carbon Dioxide 10% of carbon dioxide travels in blood as dissolved gas 20% of carbon dioxide travels in blood attached to hemoglobin (carbaminohemoglobin) 70% of carbon dioxide reacts with water in blood plasma to form the bicarbonate ion (HCO 3 - )

Hemoglobin Hemoglobin preferentially binds oxygen over carbon dioxide (but oddly, binds carbon monoxide preferentially over oxygen!) 1 hemoglobin molecule is able to bind 4 oxygen molecules Because of hemoglobin our blood can carry 70x more oxygen than it would as a dissolved gas in plasma

Bicarbonate Ion CO 2 + H 2 0  H 2 CO 3 (carbonic acid) H 2 CO 3  H + + HCO 3 - This reaction is catalyzed by carbonic anhydrase embedded in the capillary walls This reaction is reversible

External Respiration 1.HbCO 2  Hb+ CO 2 (g)↑ carbaminohemoglobin 2.H + +HCO 3 -  H 2 CO 3 3.H 2 CO 3  H 2 O+CO 2 (g)↑ 4.Hb+O 2(g)↓  HbO 2 deoxyhemoglobinoxyhemoglobin 5.HHb  Hb+ H + reduced hemoglobin

O2O2 Hb HHb HbCO 2

Internal Respiration 1.HbO 2  Hb+O 2 2.Hb+CO 2  HbCO 2 3.CO 2 +H 2 O  H 2 CO 3 4.H 2 CO 3  H + +HCO Hb+H +  HHb

HbCO 2 Hb HHb

Binding Capacity of Hemoglobin pH and temperature affect the binding capacity of hemoglobin Cooler temperature (37 C) and higher pH (7.40) of lungs raises oxygen binding capacity of hemoglobin to 98% Warmer temperature (38 C) and lower pH (7.38) of body cells lowers the oxygen binding capacity of hemoglobin to 60%

Binding Capacity of Hemoglobin This is important as the hemoglobin/RBC in the lung capillaries want to be able to bind as much oxygen as possible from the air in the alveoli The hemoglobin/RBC in the body capillaries want to be able to release oxygen to the body cells and pick up carbon dioxide from the body cells

Mechanics of Breathing Breathing is the entrance and exit of into and out of the lungs Exhalation= Expiration= air exiting the lungs Inhalation= Inspiration= air entering the lungs Breathing is a biomechanical process

Features of Thoracic Cavity For breathing to occur, the thoracic cavity must be air-tight: 1.The interior of the thoracic cavity is lined with an air- tight membrane called the parietal pleura 2.Each lung is surrounded with an air-tight membrane called the visceral pleura 3.The space between the two pleura (interpleural cavity) contains a lubricant 4.The muscular diaphragm seals the bottom of the thoracic cavity

Thoracic Cavity

Inhalation 1.Diaphragm contracts and drops down 2.Intercostal muscles in the rib cage contract and push up and out 3.The thoracic cavity increases in volume 4.Pressure in the lungs decreases 5.Air rushes into the lungs

Inhalation

Exhalation 1.Diaphragm relaxes and moves up 2.Intercostal muscles in the rib cage relax and move down and in 3.The thoracic cavity decreases in volume 4.Pressure in the lungs increases 5.Air rushes out of the lungs

Exhalation

Stimuli for Breathing: Inhalation Primary stimuli: rising CO 2 and H + ion levels trigger the respiratory center in the medulla oblongata of the brain  nerve impulse is sent along intercostal nerve to contract intercostal muscles and along phrenic nerve to contract diaphragm

Stimuli for Breathing: Inhalation Secondary stimuli: decreasing O 2 levels trigger chemoreceptors in carotid bodies of carotid arteries and aortic bodies of aorta  nerve impulse to respiratory center of medulla oblongata

Stimuli for Breathing: Exhalation Primary stimulus: as air moves into the lungs during inhalation, the alveoli sacs expand  this stimulates stretch receptors around the alveoli  initiates a nerve impulse sent to the respiratory center to turn off inhalation nerve impulse