25/4/2016. Physiology #01 Respiratory system Nayef Garaibeh Rawan Alwaten

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1 25/4/2016 Physiology #01 Respiratory system Nayef Garaibeh Rawan Alwaten

Respiratory System Introduction: - We breath while we are sleeping, talking, working and resting. - Respiratory diseases are abundant and very frequent.

2 Respiratory System Introduction: - We breath while we are sleeping, talking, working and resting. - Respiratory diseases are abundant and very frequent. They range from the simple ones like common cold, which causes congestion of the upper tract of respiration, or swelling because of a viral infection, to more serious respiratory diseases. - There are 2 types of respiration: 1. Inspiration: movement of air from atmosphere to lung 2. Expiration: movement of air from lungs to atmosphere. Each minute, we normally breath about 12 times per minute under rest conditions, and this rate is constant through all life. The good thing is the process of breathing consumes only 2 3 percent of total body energy. However, imagine a day when you have the flu or the common cold, your breathing isn't as easy as usual, just because of that congestion, you start spend more energy for breathing. Also other diseases of Respiratory System like bronchitis, bronchial asthma, and cancer are more serious and cause higher energy consumption {may spend 50 % of energy}. Anatomy of Respiratory system Conduction zone No Gas exchange Respiratory zone Gas exchange Nasal cavity Respiratory bronchioles Pharynx and larynx Duct of the alveolar sac Trachea which is divided to 2 bronchi Alveoli {which is the functional unit} of respiration Right bronchus Left bronchus Smaller & shorter bronchioles Terminal bronchioles {The air conducting. channel will end here} P a g e 1

3 Note: The major function of respiratory system is to conduct or to take oxygen from atmospheric air and take it to the tissues. It is also responsible of expelling out to get rid of the toxic carbon dioxide. Other functions of respiratory system involve homeostasis: 1. Vocalization done by the help of vocal cord. 2. Acid-base balance in our physiology If acid increases we expel carbon dioxide out If we want more acid we keep the carbon dioxide inside our body 3. Venous return: suction and negative pressure inside the chest help blood flow to go back to the heart and it's so important. 4. In the respiratory system there are some enzymes, hormones. Some modification of some substances occur in respiration to help the physiology of the human body. 5. Controls the water volume inside our body and the osmolarity by evaporation 6. Inside the respiratory system we have special cells for the immune system, that are capable of killing any invader coming inside the body by respiration. At the same time, they can also take care of any particle going through the alveoli 7. Respiratory system humid the air so dry air does not effect the alveoli. Now respiration divided in to steps: when we talk about the whole process of respiration,we will have two types of respiration, one of them is called external respiration and the other one is internal respiration. Internal respiration happens inside the cell mitochondria Also respiration will be divided into four steps: 1 st ventilation: to take the air from the atmospheric to inside the lungs and from inside and outside the lung, this is the 1st step which is ventilation. 2 nd step : related to the gases inside the lung crossing this membrane from the lung to blood and from blood to lung { gas diffusion }. 3 rd step: is the gas transport: taking oxygen by blood and hemoglobin and taking the carbon dioxide from the cell by the blood to the lungs. 4 th step: the gas diffusion step: between the blood and the cell or the tissue. P a g e 2

down to alveoli, the functional unit you will have this master piece of physiology huge network of capillaries surrounding the alveoli, If God hasn t created the alveolar structure and left the whole

4 Look at this beautiful picture of the alveolar sacs and the capillaries surrounding them. Now we have the lungs inside our chest and it is floating inside, the only attachment is with the visceral layer of Pleura, but the attachment to the chest is on the top of two lungs, but if we go down to alveoli, the functional unit you will have this master piece of physiology huge network of capillaries surrounding the alveoli, If God hasn t created the alveolar structure and left the whole lung as a balloon, then when we take the lung and expose it in front of and measure its surface area, we will find that it will be less than 1m 2. However, if alveolar structures were add it to a lung of the same volume and structure, but you add 300 millions of this functional unit, as we have 300 million in the both lungs, then when we expose them and take each alveoli and you open and spread it and put the upper one next to it and the 300 million the surface area you will get it 75 m 2, raising the surface area from less than 1m 2 to 75 m 2. Remember in that surface area we have the oxygen and carbon dioxide diffusion. Therefore, God gave us another physiological function to this part of anatomy to help give us as much oxygen as we need and take out as much carbon dioxide as necessary, this is the beauty of it. Not only the surface area, look how the capillaries hugging the alveoli because we want the capillaries as close to these alveoli to ease gas diffusion. Structure of Alveoli: Now in the alveoli, we will find a 1 layer of epithelial cell and it is called type 1 alveolar cell (type 1 pneumocyte). And in the alveoli we have another type of cell it is called type 2 alveolar cell (type2 pneumocyte) and very close to that epithelial cell we have a P a g e 3

5 basement membrane between epithelium and the capillaries, the capillary endothelial cells with pores, so, the oxygen will leave the alveoli outside to the basement membrane inside the endothelia to the capillaries. This membrane called respiratory membrane {the thickness of that membrane is not more than ½ micrometer} Now let s start with the first step of respiration which is ventilation, is inspiration and expiration. We have two types of ventilation The first type is the normal one (QUIET) in the resting condition and the other is the forceful one. MUSCELS OF RESPIRATION: we have 2 groups Inspiratory muscles: 1- major muscles of inspiration, I. diaphragm, the biggest one. A dome shaped muscle under the chest separating the abdominal cavity from the chest cavity. When it is contracts, it s pulled down, and when it relaxes, it s raised up to the chest area. So this is the movement of diaphragm. II. External intercostal muscles, those muscles are between the ribs of the chest, the direction of the muscle fibers is from posterior to interior (from up to down). So these muscles when they contract they will pull up the ribs and forward, when they are relaxed the ribs goes back. 2- Inspiratory accessory muscles, we use when we are not doing the normal quite breathing: I. Sternocleidomastoid II. The scalene muscles III. Serratus anterior All of them related to the upper part of the chest ribs and to the sternum. Expiratory muscles: 1- The internal intercostal, they are the same as external intercostal but their direction is from front to back and from down to up. So when they contract they depress the chest cavity 2- The abdominal muscles, which one of them is the abdominal rectus abdomens P a g e 4

6 Now when we breath normally we only use the diaphragm with very little utilization of the external intercostal. When the diaphragm pulls the chest down, it makes a suction force and the lungs will be filled with air. When you finish the inspiratory phase, which is about 2 seconds, you just relax your muscle fibers and they go up, pushing the air inside the lung out. This is the whole presses of inspiration and expiration during resting condition Remember inspiration happens by contracting muscle and the expiration without it. So in inspiration phase I use energy and in expiratory no need for energy(zero). Now lets talk about the forceful expiration. In normal expiration nothing happens, just relaxation of diaphragm. However, in the forceful expiration because I take more inside the lung so I need relax the inspiratory muscles, all that will help because the chest in depress and I will act the another force muscle contraction of the internal intercostal muscles and abdominal rectus, internal intercostal muscles, they will depress the chest from posterior interior dimension between spinal cord and sternum so by pushing I create positive pressure and the air will go, abdominal recti and abdominal muscle they are contracted and they will push the internal organ upward and they will even stretch the diaphragm farther more up by doing that movement you will push the lung from the bottom and you depress the air in the lung cavity they will go out. So this is the ventilation this the inspiration and expiration normal one and forceful one. Now this is the simple way to explain inspiration and expiration what is more than more complex there is biophysics in the movement of air. The biophysics has simple roles if you want the air to come from one area to anther area, you have the to change the pressure between these two areas, you have to create positive pressure in one side and less pressure in the other side, not necessarily negative, but less so the air will move from higher to lower pressure this is simple. Now, what happens in the lungs is that we have different pressures or what we call respiratory pressures what are those respiratory pressure? first if you want know how the lung located in the chest like that. So the lung will be inside the pleura and this visceral layer of pleura will be attached to the lung layer the partial layer pleura which the out side will be attached to the internal surfaces of the chest. P a g e 5

7 in between visceral and parietal layer we have very small space {potential spaces intrapleural space} and it is filled with slight amount of fluid, after delivery of the human, the lymphatic system of that new born will have a suction of the fluid from the pleura and since you know that the pleural space is closed so this is one of respiratory pressure we call it intra-pleural pressure: The value of this pressure -5 cm H 2 O inside the lung we have Intra-alveolar pressure. Intra-alveoli pressure (the pressure inside the alveoli) might be 0, +1, -1 when it's zero!! when the glottis is open and no breathing the pressure in alveoli equal to atmospheric pressure. Let me explain What's the meaning of zero pressure? On the sea level we have atmospheric pressure is = 760mmHg and inside your body you have the same pressure, if it increase more than 760 you will have positive, if you have a pressure less than 760 you will have negative pressure. So the zero pressure inside alveoli = 760 mmhg In order to do inspiration we should make the pressure in the alveoli less than pressure in atmosphere, so air will move from high to low pressure { inspiratory phase done by help of diaphragm or by external intercostal muscles or by accessory mussels we will create that suction around the lungs and we will create a negative pressure inside the lung } During expiration, I have the opposite I want to expel the air from inside the lung to out so I need positive pressure which means more than 760. Now there are another 3rd pressure called trans-pulmonary pressure, this one is not pressure you can go and measure it Trans-pulmonary pressure = Intra-alveoli pressure - Intra-plural pressure, so I measure the Intra-alveoli pressure of any time of the respiratory phase I give the number I measure the Intra-plural pressure, I give the number I subtracted the intra-plural pressure from Intra-alveoli pressure,i give the trans-pulmonary pressure The important of this pressure, will give you an idea about how much volume occur inside your lungs. if I have more volume I will have more trans-pulmonary pressure, less volume,, less trans-pulmonary pressure P a g e 6

8 . what happens during these phases? this is an inspiration, I start to inspire end this is the expiration let's take the real one, this is the real one and this scalene is the volume of air inspire and expire when you start inspire you will get more volume of air inside your lungs normally it's about half litter (quit breathing) when you expire you expire that half litter out so it was zero, half litter,from half litter to zero.now let's go to the alveolar spaces measure the Intra-alveoli pressure during those 2 phases, during inspiration as I said no air flow glottis open so the pressure inside alveoli zero, when I start to inspire I will create a suction with a negative pressure inside the alveoli and it will start to go down below zero so zero negative and until I reach about -1 here almost the middle way in the inspiration phase but after this point Intra-alveoli pressure start to increase from -1 to zero by the end of inspiration when you take half litter the glottis is open you stop breathing no air flow so Intra-alveoli pressure is zero so that slope the change of Intra-alveoli pressure - then up to the zero during expiration from zero to +1 then back to the zero so this is the care straight the changes of Intra-alveoli pressure during respiration - Intra-pulmonary pressure I told you after delivery we have the suction, the suction creates -5 inside the pleura, during inspiration when you make the respiratory movement you will increase the chest cavity and you will go down with the diaphragm you create move suction inside the pleura, and this move section it will create move negative pressure from -5 it goes down to -8 or -7.5 by the end of inspiration we will have more negative Intra-pulmonary pressure inside the pleura. During expiration you will expel that negative out, you will push it back and you will get back to the -5. So this are important to remember the way by which respiratory pressure are change during the in and out. P a g e 7

9 Edited by: Hamza Al-yassin P a g e 8

The Respiratory System

Essentials of Human Anatomy & Physiology Elaine N. Marieb Seventh Edition Chapter 13 The Respiratory System Slides 13.1 13.30 Lecture Slides in PowerPoint by Jerry L. Cook Organs of the Respiratory system