Beni-Suef National University General Zoology Lectures 5 & 6 PDF

Beni-Suef National University Faculty of Science General Zoology (Physiology) 1st Year Students 1st Semester, 2024-2025 Respiration and Lectures 5 Respiratory and 6 system Respiration aims to provide cells of...

Beni-Suef National University Faculty of Science General Zoology (Physiology) 1st Year Students 1st Semester, 2024-2025 Respiration and Lectures 5 Respiratory and 6 system Respiration aims to provide cells of organism with oxygen used in oxidation of glucose and fatty acids to produce energy and to get ride of carbon dioxide produced from these processes.  Different ways of respiration in animal kingdom 1. Direct exchange of gases between cells of the animal and environment. This way is found in Phyla: protozoa, porifera (sponges), coelentrata and platyhelminthes. 2. Direct exchange of gases between blood in peripheral blood vessels and environment. This way is found in phylum: annelida. 3. Respiration through spiracles leading to tracheas that are branched within the body into tracheoles as in arthropods like insects. These spiracles are covered with tracheal gills in nymph of mayfly as it lives in water. The respiration takes place though siphon at the end of the abdomin in the larvae of mosquitoes. 4. Exchange of gases through gills viz in fish. Exchange of gases take place between water currents and blood capillaries within the gills. 5. Exchange of gases through lungs viz in land vertebrates. Exchange of gases take place between air and blood capillaries within the lungs. 1 2 3 3 5 4 Respiration and respiratory system in humans Respiration is the exchange of oxygen and carbon dioxide between the atmosphere and the body cells, including inhalation and exhalation; diffusion of oxygen from alveoli to blood and of carbon dioxide from blood to alveoli; and transport of oxygen to and carbon dioxide from body cells. Types of respiration - External respiration: exchange of gases between air in the lungs and blood. - Internal respiration: exchange of gases between the body cells and blood. - Cellular respiration: the use of oxygen by the body cells in oxidation of food stuffs to produce energy.  Structure of respiratory system Nose Pharynx and Larynx Trachea Bronchi Lungs (bronchioles and alveoli) Parts of the respiratory system Number of alveoli in human lungs range from 600-700 million/two lungs which form a surface area of about 50-90 m2  Inspiration and Expiration Inspiration – Ribs are pushed to outside and upward by the contraction of external intercostal muscles. – Diaphragm contracts and moves downwards. – Thoracic cavity increases in size and lung space increases – Pressure gradient causes gas to flow into the lungs Expiration – External intercostal muscles and diaphragm relax and return to normal position decreasing the size of thoracic cavity and decreasing lung space. – Pressure gradient causes air to flow to outside.  LE 22-7a Rib cage gets Rib cage smaller as expands as rib muscles rib muscles Air Air relax contract inhaled exhaled Lung Diaphragm Diaphragm contracts Diaphragm relaxes (moves down) (moves up) Inhalation Exhalation Quiet inspiration - During deep expiration, internal intercostal muscles contract pulling ribs more inward. - Abdominal muscles also contract to press on viscera that cause more pushing of the relaxed diaphragm to upwards Pressure Changes during Inspiration (a) Prior to inspiration, the intrapulmonary pressure is 760 millimeters of mercury (mm Hg). (b) The intrapulmonary pressure decreases to about 757 mm Hg as the thoracic cavity enlarges, and atmospheric pressure forces air into the airways. Breathing During inspiration, the diaphragm and the external intercostal muscles contract. The diaphragm moves downwards increasing the volume of the thoracic (chest) cavity, and the external intercostal muscles pull the ribs up expanding the rib cage and further increasing this volume. In contrast to inspiration, during expiration the diaphragm and intercostal muscles relax. This returns the thoracic cavity to it's original volume, increasing the air pressure in the lungs, and forcing the air out. Gas Exchange Gas Exchange Systems Transport of O2 and CO2 in the blood Oxygen is transported in two forms 1- 98% bind with haemoglobin (Hb) to form oxyhaemoglobin. 2- 2% are physically dissolved in blood plasma. Carbon dioxide is transported in three forms: 1- Less than one third (about 25%) enter RBCs and combine with Hb to form carbaminohaemoglobin (carboxy Hb). 2- About two thirds (about 67%) enter RBCs and form bicarbonate 3- 8% are physically dissolved in the blood plasma. Exchange of gases in the lungs  Gas Transport Each red blood cell contains 280 million hemoglobin molecules. Hemoglobin is folded protein with four iron-containing heme groups. Each heme unit binds with one oxygen unit. As a hemoglobin unit becomes oxygenated, its color changes to a brighter red. Collectively, this molecular color change is evident in the bright red color associated with arterial blood.  Gas Transport Oxygen transport Gas Transport CO2 transport Gas Transport  Nervous control of external respiration The dorsal respiratory group (DRG) is responsible for normal quiet inspiration. At usual blood gas levels, DRG generates action potentials spontaneously about 15 times per minute. The output from these is mainly to the diaphragm and external intercostal muscles and is responsible for inspiration during quiet breathing. The DRG can be considered the main respiratory pacemaker at rest. Dorsal Respiratory Group—Quiet inspiration Ventral Respiratory Group—Forceful inspiration and active expiration Pneumotaxic Center—Influences inspiration to shut off Apneustic Center—Prolongs inspiration Brainstem Respiratory Centers Guyton & Hall, Textbook of Medical Physiology, 10th ed., 2000, Saunders p. 475.  Control of Ventilation Respiratory control center – Receives neural and humoral input Feedback from muscles CO2 level in the blood – Regulates respiratory rate Control of Respiration DRG The dorsal respiratory group (DRG) is responsible for normal quiet inspiration. At usual blood gas levels, DRG generates action potentials spontaneously about 15 times per minute. The output from these is mainly to the diaphragm and external intercostal muscles and is responsible for inspiration during quiet breathing. The DRG can be considered the main respiratory pacemaker at rest.  Brainstem Respiratory Centers Dorsal Respiratory Group—Quiet inspiration Ventral Respiratory Group—Forceful inspiration and active expiration Pneumotaxic Center—Influences inspiration to shut off Apneustic Center—Prolongs inspiration Mehanoreceptors, Mechanoreceptors,  Brain Stem Respiratory Centers Neurons in the reticular formation of the medulla oblongata form the rhythmicity center: – Controls automatic breathing. – Consists of interacting neurons that fire either during inspiration (I neurons) or expiration (E neurons).  Rhythmicity Center I neurons located primarily in dorsal respiratory group (DRG): – Regulate activity of phrenic nerve. – Regulate the activity of external intercostal nerve Project to and stimulate spinal interneurons that innervate respiratory muscles. E neurons located in ventral respiratory group (VRG): – Passive process. Controls motor neurons to the internal intercostal muscles. Activity of E neurons inhibit I neurons. – Rhythmicity of I and E neurons may be due to pacemaker neurons. Brain Stem Respiratory Centers (continued) I neurons project to, and stimulate spinal motor neurons that innervate respiratory muscles. Expiration is a passive process that occurs when the I neurons are inhibited. Activity varies in a reciprocal way.  Pons Respiratory Centers Activities of medullary rhythmicity center is influenced by pons. Apneustic center: – Promotes inspiration by stimulating the I neurons in the medulla. Pneumotaxic center: – Antagonizes the apneustic center. – Inhibits inspiration. Chemoreceptor Control of Breathing Insert fig. 16.29  Respiratory volumes and capacities The measurement of air that comes in and out of the lungs is known as spirometry and the apparatus used is known as spirometer Tidal air volume (VT) (the volume of air that enters the lungs during normal inspiration or leaves the lungs during expiration)= 500 ml Complemental air volume (CV) (inspiratory reserve volume; IRV) (excess volume of air inhaled above tidal air volume during forceful respiration) or in other words, it is the additional amount of air entering the lungs during forced inspiration = 3000 ml Supplemental air volume (SV) (expiratory reserve volume; ERV) (excess volume of air exhaled above tidal air volume during forceful respiration) = 1000 -1200 ml. Residual air volume (RV) (the amount of air that remains in lungs after deep expiration) = 1200 ml Functional residual capacity (FRC) (the amount of air that remains in lungs after resting expiration) Total lung capacity (TLC) = VT + IRV + ERV +RV Vital capacity = VT + IRV + ERV Inspiratory capacity (IRC) = VT + IRV Expiratory capacity (ERC) = VT + ERV Respiratory volumes and capacities