The Mammalian Respiratory System Introduction to Respiration
Respiration • Refers to all parts of the process that supplies oxygento body cells and rids the bodyof carbon dioxide • In mammals, respiration can be subdivided into the following: • Breathing • External respiration • Internal respiration • Cellular respiration
Breathing • Can be further divided into • Inspiration: the act of taking air into the lungs • Expiration: the act of breathing out
Internal & External Respiration • The mechanism of the internal and external respiration depends on diffusion theory indicating that the substance diffuses from the area with high density to the lower one
External Respiration • The exchange of oxygen and carbon dioxide between air and blood
Internal Respiration • The exchange of oxygen and carbon dioxide between blood and the cells of the surrounding tissue
Cellular Respiration • The complex series of chemical reactions that take place mainly in the mitochondria of cells
The Respiratory Tract • Involved in the process of respiration • Further divided into two parts:1. The upper respiratory tract2. The lower respiratory tract • The upper and lower respiratory tracts make up our whole respiratory system and work in a synchronizing pattern to make it possible to breathe.
The Upper Respiratory Tract • The upper respiratory tract refers to the following parts of the respiratory system: • The nasal passages • Glottis • Pharynx • Larynx • Trachea
The Lower Respiratory Tract • The lower respiratory tract refers to the following parts of the respiratory system: • Larynx (voice box) • Trachea (wind pipe) • bronchial tubes • Bronchioles • lungs
The Upper Respiratory Tract Mammalian Respiratory System
The Nasal Passages • The air first enters the nostrils • In humans and many other animals, it can also enter via the mouth • Air is conducted into the hollow nasal passages • The nasal chambers are protected by turbinates
Turbinates • Thin bones • Hang suspended from the nasal chambers • Their presence increases the surface area of these chambers • Turbines covered with a thin membrane that secret mucus • Mucus helps moisten the air • Turbinates and linings of the nasal chambers are supplied with capillaries • This helps to warm the incoming air and to increase the air humidity • The warming and moistening helps to protect the lung tissues
Pharynx • The air then passes through the pharynx • The pharynx is part of the digestive system and respiratory system of many organisms • Section of the alimentary canal • Connects the mouth and nasal cavity to the larynx and esophagous
Pharynx • So the pharynx is a common channel that conducts both air and food. • Because of these two functions, the pharynx must open to allow air and food to pass through, and at the same time, it must be able to squeeze the food down into the oesophagus. • The pharynx performs these functions simultaneously at mealtimes.
Glottis • The opening of the trachea • The passageway conducting air to the lungs • The area where the vocal cords are located
Epiglottis • The glottis opening is protected by epiglottis • Flap-like structure attached to the root of the tongue • helps to prevent food from entering the trachea
Larynx • Biologically, the larynx evolved as a valve to protect the airway and lungs. • Thus, it is positioned where the airway and the esophagus separate. • Also know as “voice box” • Contains the two folded structures of the vocal cords (vocal folds) Larynx
Vocal fold vs. Vocal cord • ‘Vocal fold’ is the modern term for ‘vocal cord.’ • ‘Vocal cord’ suggests a band or string suspended in the air that vibrates when it is plucked or struck. • However, the vocal fold is a part of a muscle on the side of the larynx, covered with special tissues that can vibrate at a high speed.
Vocal Folds • The vocal folds are a pair of tissue that stretch across the top of the trachea • The vocal folds, together with the muscles and cartilages that support them, are known as the larynx • Voice is produced by vibration of the vocal folds.
Vocal Folds • When we breathe normally, there is a large gap between the two folds • When we prepare to speak, muscles around the larynx contract, bringing the folds closer together • The passage of air through this narrow space causes the folds to vibrate producing a sound
Pitch and Sound • The pitch of the sound can be changed by both:
Glottis • You can change the pitch of the sound you make by expanding or tightening the glottis • The tighter the glottis, the higher the sound
Vocal Folds • In addition to opening and closing, the vocal folds are able to lengthen and shorten • The pitch of the sound varies with the length of the vocal folds • A long fold produces a low sound • A shorter fold produces a higher sound • At puberty, the vocal folds of males grow quickly • The vocal folds in men tend to be longer than in women, therefore men have a deeper voice
Trachea • After passing through the larynx, air goes down the trachea • Flexible tube, in mammals, called the ‘wind pipe’ • Supported by semicircular cartilage rings • These rings prevent the trachea from collapsing • Rings arranged in a way that do not interfere with the passage of food down the esophagus
The upper respiratory tract • The nasal and other passages of the upper respiratory tract are lined with ciliated cells that secrete mucus
Ciliated cells • The mucus traps foreign particles such as dust and bacteria • Cilia help these foreign materials to move back into the nose and throat where they can be expelled by coughing or sneezing
The Lower Respiratory Tract Mammalian Respiratory System
The Lower Respiratory Tract • The trachea branches into two smaller passageways called bronchi (singular= bronchus) • One bronchus enters each lung • Each bronchus subdivides many times to produce bronchioles • Bronchioles are a network of finer tubes • Like the trachea and nasal passages, the bronchi and bronchioles are also lined with ciliated cells
The Lower Respiratory Tract • Each bronchiole ends in a grape-like cluster of tiny sacs called alveoli (singular= alveolus)
Alveoli • Alveoli are always kept moist • Actual gas exchange of gases takes place in alveoli • The walls ofeach sac is onecell thick and is adjacent to a network of tinycapillaries
Alveoli • The network of capillaries are the site for gas exchange of oxygen and carbon dioxide • Most gas exchange takes place through simple diffusion • 30% of gas exchange is through facilitated diffusion • This allows blood to take up oxygen more quickly than would otherwise
Capillary Network • Bronchioles and alveoli are kept in a permanent position by elastic connective tissue • Alveoli are lined with a film that contains lipoprotein, which helps alveoli from collapsing O2 rich blood CO2 rich blood
Gas Exchange • The carbon dioxide and oxygen concentration in the lung capillary blood is higher and lower than in the air of the pulmonary alveoli • so the carbon dioxide diffuses from the blood to the pulmonary alveoli and the oxygen diffuses from pulmonary alveoli to the blood. In Blood: Low [O2] High [CO2] In Alveoli: high [O2] Low [CO2]
Gas Exchange • The condition between the body tissue is just reverse • The carbon dioxide and oxygen concentration in the blood is respectively lower and higher than in the body tissues • So the carbon dioxide diffuses from the body tissue to the blood and the oxygen diffuses from the blood to the body tissues. In Body cells and tissues: Low [O2] High [CO2] In Blood: High [O2] Low [CO2]
Lungs • Each lung is divided into lobes • The right lung has three lobes • The left lung has only two lobes • A lobe is made up of a number of lobules, each with its own bronchiole. Right Lung Left Lung
Pleura Lubricating fluid • The lungs are enveloped in layers of tissue called pleura (singular= pleuron) • Pleura is a flexible membrane containing the lungs and • Allowing the lungs to expand during inspiration and contract during expiration • Each pleuron is made up of two layers separated by a thin film of lubricating fluid
Pleurisy • Condition occurs when the pleura become inflamed • Often caused by certain respiratory conditions • Typically as a secondary infection related to pneumonia or other thoracic diseases • Pleurisy is not a disease, but rather a chest pain caused by the lung and chest wall rubbing against each other. • Can be extremely painful • Environmental factors such as asbestos in the air can also cause pleurisy.