The respiratory system of the human consists of: 1- The nose 2- Pharynx 3- Larynx 4- Trachea 5- Bronchi 6- Lungs
TWO RESPIRATORY TRACT Upper respiratory tract: The upper respiratory tract consists of; the nose, pharynx (throat), and associated structures. Lower respiratory tract: The lower respiratory tract consists of the larynx, trachea, bronchi and The lower respiratory tract cons lungs.
Nose Structure : Nose has a basic framework of bone and cartilage attached to muscle and the outer skin lined with mucous membrane. The internal structure of the nose is connected to the pharynx by two openings called internal nares. Function : Air breathed in through the nose is warmed, moistened and filtered as it passes through the conchae, three bony projections which are lined with mucous membrane composed of cells which can trap particles of dust and germs. The filtered air flows through the internal nare into the pharynx.
The Respiratory Organs 1- Nose: The nose consists of an external portion and internal portion. The external portion is the part of the nose that projects outside of the face and consists of bone and cartilage covered by skin and lined by mucous membrane. The external nose has openings called external nacres or nostrils.
The internal portion Of the nose is a large cavity in the anterior- lower part of the skull, inferior to the cranium and above the mouth. Interiorly the internal nose merges with the external nose and posteriorly it communicates with the throat (pharynx) through two openings called internal nares. The inside of both the external and internal nose is divided into right and left sides by the nasal septum.
Physiological functions of the nose: The nose has special important functions: 1- Filter, warms, and moisturize inspired air. 2- Perform Olfactory (smell) function. 3- Modify speech, due to the presence of hollow resonating chambers.
Respiratory Organs….Cont. 2- Pharynx: It is a funnel shape wide muscular tube, situated posterior to the nasal cavity, oral cavity, and larynx, and anterior to the cervical vertebrae. It starts at the base of the skull and extends to the level of the cricoids cartilage (about 12 – 13 cm in length).
Respiratory Organs….Cont. The pharynx is divided into three parts. Nasal part : upper part (nasopharynx) Oral par : middle part (oropharynx) Laryngeal part : lower part (laryngopharynx) The pharynx functions as a passage way for air, food and provides a secondary chamber for speech.
Respiratory Organs….Cont. 3- Larynx The Larynx (voice box); is a short passageway that connects pharynx with the trachea. It lies in the midline of the neck. The wall of the larynx is composed of nine 9 pieces of cartilage, three of which are single and three are paired.
Respiratory Organs….Cont. The Epiglottis is the most important cartilage of all the cartilages of the Larynx. It is a large leaf shaped piece of cartilage lying on the top of the Larynx. The fixed part of the epiglottis is attached to the thyroid cartilage, and the free part is unattached and move downward, during swallowing, to close the larynx and prevent the passage of food into the trachea.
Respiratory Organs….Cont. 4- The Trachea. The trachea (The wind pipe) is a wide fibrocatrtilagenous tube, lies more or less in the midline of the lower part of the neck and in the superior mediastinum (different structures of the thorax) anterior to the esophagus. It is about 12 cm long and 2.5 cm in diameter and extends from the larynx downwards until it divides into: right and left primary bronchi.
Respiratory Organs….Cont. The trachea has a fibroblastic wall supported by a cartilaginous skeleton formed by C-shaped rings. These rings are about 16-20 in number. The mucous membrane of the carina is one of the most sensitive areas of the respiratory system to induce cough reflex. Function: Trachea forms a passage for air to travel from larynx to lungs. The inner wall of trachea traps particles of dust and microorganisms which are moved upwards and expelled from the respiratory tract.
5- The Bronchi Trachea ends by dividing at the level of the sternal angle into two primary bronchi: - The right primary bronchus - The left primary bronchus The right primary bronchus is more vertical, shorter and wider than the left primary bronchus, thus foreign objects like dust particles in the air are more likely to enter easily into the right lung than the left lung. So the infection of the right lung is more common than the left lung. Function: Bronchi help in gaseous exchange within lungs.
6- Lungs Structure: Lungs are cone-shaped and extend from the collar bone to the surface of the diaphragm. The mid-line of each lung contains a region known as the hilus, the area through which blood and lymphatic vessels, nerves and primary bronchi enter and leave. Each lung is divided into lobes, three in the right lung and two in the left, within which there are smaller divisions known as lobules. Function: Once the air reaches the alveoli, exchange of gases occur. Diffusion of gases takes place across the thin capillary and alveolar walls. Oxygen is passed into the capillaries for supply to body tissues and carbon dioxide is passed from the capillaries to the alveoli to be expelled from the body during exhalation.
Respiratory Organs….Cont. The pleural cavity is a small potential space between the two layers of pleura, which contains lubricant secreted by the membranes to prevent friction between the membranes and allows them to move easily during breathing. The lungs extend from the diaphragm to a point about 1.5-2 cm superior to the clavicles and anterior- posteriorly against the ribs and the vertebrae. The narrow superior portion of the lung is called the apex, with its concave base rests on the convex surface of the diaphragm.
Physiology of respiration The main purpose of respiration is to supply oxygen to and remove carbon dioxide from different tissues of the body. Respiration is divided in to four basic functional events: Pulmonary ventilation Diffusion of gases: oxygen and carbon dioxide between the alveoli and blood. Transport of gases: oxygen and carbon dioxide in blood and body fluids to and from cells. Regulation of ventilation.
Alveoli: The alveoli are sac-shaped bodies present inside the lungs. These grape-like bodies are found only in lungs of mammals and present at the end of alveolar ducts. The alveoli functions as an interface for exchange of oxygen and carbon dioxide between the lungs and capillaries that connect with rest of the body.alveoli functions
Inspired and Expired Air Comparison Gas + % Inspired Air Expired AirAlteration Nitrogen78%76% No real change. Oxygen20.8%15.3% Reduced by about a quarter Carbon Dioxide 0.04%4.2% Increased by about a hundred and five times Water Vapour 1.2%6.1% Increased about five times Note: a lot of water is lost from the body each day due to breathing.
Pulmonary ventilation Is the inflow and outflow of air between the atmosphere and the alveoli of the lungs. In the pulmonary ventilation an important factor called the pressure gradient plays an important role. Air moves into the lungs, when the pressure inside the lungs is less than that of the atmospheric pressure. Air moves out of the lungs, when the pressure in the lungs is greater than the atmospheric pressure.
Different pressures involved in respiration are: Interpleural pressure or pleural pressure. This is the pressure inside the pleural cavity. It may be defined as the negative pressure in the pleural space required to prevent the collapse of the lungs.
Interalveolar pressure (alveolar pressure) This is the pressure inside the alveoli. The alveolar pressure changes during both inspiration and expiration. The normal alveolar pressure is equal to the atmospheric pressure, which is 760 mmHg. Transpulmonary pressure: Is the difference between the alveolar and pleural pres sure.
Mechanism of Pulmonary Ventilation Inspiration : Just prior inspiration, the air pressure inside the lungs equal to the pressure of the atmosphere which is equal to 760 mm Hg. During inspiration the alveolar pressure becomes lower than the atmospheric pressure about 758mm Hg, so air moves from the atmosphere to the lungs. This condition is achieved by increasing the volume (size) of the lungs.
Mechanism of inspiration Inspiration- Diaphragm and intercostal muscles contract. The diaphragm moves downwards. The intercostals muscles make the rib cage move upwards. These two processes increase the volume of the thoracic cavity and also reduce the air pressure to below atmospheric pressure allowing air to rush into the airways then into the alveoli.
Expiration Is the process of releasing out the alveolar air containing excess of CO2. When expiration starts, alveolar pressure is increased more than that of the atmospheric to become about 762 mm Hg, so the air moves from the alveoli outwards to the atmosphere.
Mechanism of expiration: Expiration is the opposite of inspiration as in the diaphragm and intercostal muscles relax, this allows the diaphragm to move upwards and the intercostal muscles let the rib cage relax to its resting state. The volume within the thoracic cavity now decreases. This decrease in volume now causes an increase in pressure above atmospheric pressure which forces air out up the airway.
Factors affecting compliance. 1- Elasticity of lungs: Increased elasticity of the lungs tissue results in high compliance, and vice versa. 2- Surface tension: If surface tension within a lung is high, it decrease its compliance, and the lung tissue would resist expansion. 3- Surfactant: Surfactant is secreted by type II alveolar epithelial cells. It decreases surface tension so that the compliance of the lungs is increased.
Case of adult respiratory distress syndrome (ARDS): Adult respiratory distress syndrome, is a serious pulmonary destructive disease, that might be due to: Systemic disorders, septicemia (the presence of pathogenic organisms in the bloodstream, leading to sepsis), uremia (nitrogenous waste products associated with the kidney). Aspiration of irritant substances: Vomits, hydrocarbons Inhaled toxics chemicals, like chlorine, ammonia, nitrogen oxide, and smoke Pneumonia: viral, bacterial and fungal Blood disorders: disseminated intravascular coagulation (leads to the formation of small blood clots inside the blood vessels throughout the body) thrombocytopenic purpura, and blood product transfusion. Lungs emboli, air, fat, amniotic fluid Lungs trauma Drugs, barbiturates and thiazides (diuretic)
Mechanism of cough: The cough reflex is a protective mechanism of the respiratory system. It is initiated when any foreign matter reaches the cough sensitive area. Afferent impulses are sent to the medulla via the vagus nerve. About 2 to 2.5 liters of air is inspired, the epiglottis closes, the vocal cord shut lightly to entrap the air within the lungs, and then the abdominal muscles contract forcefully. This causes the pressure in the lungs to rise as high as 100 mm Hg. The vocal cord and epiglottis then open suddenly so the air under pressure in the lungs explodes outwards with a velocity of 75-100 miles an hour.
QUESTIONS: When your answer is correct, we will give you a reward! 1. What is the two main purpose of respiratory system? 2. How many lobe’s in our right lungs? 3. How many pieces of cartilage in our larynx? 4. What is the most important cartilage of larynx? 5. What is the report all about?