The Respiratory System Chapter 15 the Respiratory System
The Respiratory System Chapter 15 The Respiratory System
• Learning Objectives: When you have completed this chapter you should be able to:
Differentiate between internal, external, and cellular respiration.
List the secondary functions of the respiratory system. The Respiratory System
• List the components of the upper respiratory tract and describe their structure and functions.
• List the components of the lower respiratory tract and describe their structure and functions.
• Describe the events that occur during inspiration and expiration. The Respiratory System
• List the muscles involved in inspiration and expiration.
• Define the terms tidal volume, minute volume, and residual volume.
• Describe the processes of oxygen and carbon dioxide exchange between the alveoli and the blood. The Respiratory System
• Vocabulary Fundaments:
Be able to define, describe, or identify the terms on pages 361 and 362. The Respiratory System
• Respiration is the process of bringing oxygen to all body cells and carrying carbon dioxide in the opposite direction.
• Types: External respiration Internal respiration Cellular respiration The Respiratory System
• Secondary functions of the respiratory system:
Voice production Body temperature regulation Acid-base balance Smell The Respiratory System
• Voice production or “phonation” begins in the larynx.
• The vocal cords or vocal folds:
Stretch across the lumen of the larynx The folds vibrate as air passes over them This produces the basic sound of an animal’s voice The Respiratory System
• Body temperature regulation involves several body systems.
• The respiratory system utilizes superficial blood vessels lining the nasal passages.
Inhaled air is warmed.
Panting uses evaporation to cool.
The Respiratory System
• Acid-base balance is an essential homeostatic mechanism of the body.
• Normal acid-base is essential for normal chemical reactions in the body.
• The respiratory system regulates the amount of CO2 and O2 in blood. The more CO2 there is, the lower (more acid) the blood is. Normal blood pH = 7.4 (Range is 7.35 to 7.45) The Respiratory System
• The olfactory system is based on sensory epithelium in in the upper respiratory passages of the nose.
• The olfactory system is covered in the chapter on special senses. The Respiratory System
• The respiratory system is made up a series of specialized tubes that connect the lungs to the outside world.
• The upper respiratory tract consists of all the structures outside the lungs.
• The lower respiratory tract consists of all the structures in the lungs. The Respiratory System
• The upper respiratory tract is made up of:
Nostrils Nasal passages Pharynx Larynx Trachea
The Respiratory System
• The external openings of the respiratory passages are the nostrils, most properly known as the nares.
• The nasal passages lie between the nares and the pharynx.
• The midline of the passages is known as the nasal septum. The Respiratory System
• In the nasal passages turbinates, or nasal conchae, divide each passage into three main passageways:
Ventral nasal meatus Middle nasal meatus Dorsal nasal meatus The Respiratory System
• The nasal passages are lined with pseudostratified columnar epithelium, cilia, mucous, and blood vessels.
• The main function of the nasal passages is to “condition” inhaled air.
• Conditioning includes: Warming Humidifying Filtering The Respiratory System
• The sinuses are ciliated outpouchings of the nasal passages.
• The sinuses are names for the bones that house them.
Frontal sinus Maxillary sinus
The Respiratory System
• The pharynx, or throat, is the common passageway for the respiratory and digestive systems.
• The pharynx is divided at the rostral end by the soft palate:
Nasopharynx (respiratory portion) Oropharynx (digestive portion) • The pharynx opens at the caudal end into the larynx and the esophagus. The Respiratory System
• The larynx , or voice box, connects the pharynx with the trachea.
• The larynx is supported by the the hyoid bone or hyoid apparatus.
• The hyoid apparatus is made up of several cartilage segments: Epiglottis (1) Artenoid cartilages (2) Thyroid cartilage (1) Cricoid cartilage (1) The Respiratory System
• The vocal folds are attached to the artenoid cartilages which form the boundaries of the glottis.
• Muscles are attached to the cartilages to adjust tension on the folds.
• There is a set of false vocal, or vestibular, folds in nonruminant animals.
• The false vocal folds are a second set of connective tissue bands. The Respiratory System
• The Larynx:
Forms part of the upper respiratory system. Aids in voice production. Helps prevent the inhalation of foreign matter. Helps control the flow of air into the trachea. The Respiratory System
• The epiglottis is the most rostral of the cartilages.
• The epiglottis covers the larynx during swallowing.
• The epiglottis insures that air goes into the trachea and food goes into the esophagus.
The Respiratory System
• The trachea is a short, wide tube made up of fibrous tissue and smooth muscle held open by cartilage rings.
• The trachea extends from the larynx into the thoracic cavity where it divides into the right and left primary bronchi.
• C-shaped rings spaced along the length of the trachea prevent collapse during respiration.
• The trachea has a ciliated lining and a mucous layer.
The Respiratory System
• The lower respiratory system, also known as the bronchial tree, is made up of:
Bronchi Bronchioles Alveolar ducts Alveoli
The Respiratory System
• The autonomic nervous system (sympathetic and parasympathetic) controls the diameter of the bronchial tubes by constricting and relaxing smooth muscle fiber in their walls.
Bronchodilation
Bronchoconstriction The Respiratory System
• The alveoli are tiny, thin-walled sacs surrounded by capillaries.
• The sacs are lined with a think layer of fluid that contains a surfactant.
• External respiration takes place in the alveoli.
• O2 and CO2 are exchanged between the alveoli and blood.
The Respiratory System
• The lungs are cone-shaped structures with a light, spongy consistency.
• The base of the lungs lies directly on the cranial surface of the diaphragm.
• The area between the lungs is the mediastinum.
The Respiratory System
• The lungs are divided into lobes.
• The lobes have the same basic structure among species:
Left lung: cranial, middle, caudal lobes
Right lung: cranial, middle, caudal, accessory lobes
The horse is the exception, with a left lobe, and a right lobe and accessory lobe.
The Respiratory System
• The hilus of the lung is a small well defined area on the medial side where bronchial tubes, nerves, blood vessels, and lymph vessels enter and leave the lungs. The Respiratory System
• In pulmonary circulation deoxygenated blood enters the lungs from the right side of the heart through the pulmonary arteries.
• The blood vessels follow the bronchial tree and quickly subdivide.
• These branching's form capillary networks abound the alveoli and O2 and CO2 are exchanges by simple diffusion. The Respiratory System
• The thoracic cavity is an area bounded by the thoracic vertebrae, the robs, the intercostal muscles, the diaphragm, and the sternum.
• The lungs, heart, large blood vessels, trachea, esophagus, lymphatic vessels, lymph nodes, nerves, and supporting tissues lie in the thorax.
The Respiratory System
• The mediastinum contains the heart, trachea, blood vessels, nerves, and lymphatic structures. The Respiratory System
• The diaphragm is a thin sheet of skeletal (voluntary) muscle, which forms the caudal boundary of the thorax.
• The diaphragm acts as a respiratory muscle.
• The diaphragm flattens when it contacts increasing the size of the thorax, and decreases the size of the thorax when it relaxes. The Respiratory System
• There is negative intrathoracic pressure in the thorax, or a partial vacuum.
• This allows the lungs to follow the movements of the thoracic wall and diaphragm. This results in inhalation and exhalation.
• This also aids in return of blood to the heart . The Respiratory System
• Inhalation, or inspiration, is the process of drawing air into the lungs.
• Inhalation results from the enlargement of the thoracic cavity.
• The lungs passively follow the movement of the thoracic walls.
• The diaphragm and external intercostal muscles are the main inspiratory muscles.
The Respiratory System
• Exhalation, or expiration, is the process of pushing air out of the lungs.
• Exhalation is the opposite of inhalation. In exhalation the size of the thorax is decreased, the lungs are compressed, and air is pushed out through the respiratory passageways.
• The internal intercostal and abdominal muscles are primary muscles of expiration.
The Respiratory System
• The common standardized parameters for describing the quantity of air involved in normal respiration are:
Tidal volume Minute volume Residual volume
The Respiratory System
• With inspiration the inhaled air is high in O2 and low in CO2.
• The blood entering the capillaries is low in O2 and high CO2.
• In the alveoli high levels of O2 in air diffuses into the blood where the level is lower, and high levels of CO2 in blood diffuses into air where the level is lower. The Respiratory System
• In exhalation the exhaled air is higher in CO2 and lower in O2. The Respiratory System
• The partial pressure of a mixture of a gasses is the sum of the pressures of each individual gas. – Dalton
• The pressure of each individual gas is the partial pressure. Partial pressures also apply to gasses dissolved in liquids.
• The partial pressures of O2 and CO2 in blood capillaries is the determined by the partial pressures of the gasses in alveolar air.
The Respiratory System
• Breathing is controlled by an area in the medulla oblongata of the brain stem. The respiratory center directs the timing and strength of respiratory muscle contraction.
• There are individual control centers for inspiration, expiration, and breath-holding.
• Breathing can be consciously controlled for brief periods of time. The Respiratory System
• The mechanical control of breathing operates through stretch receptors in the the lungs.
• This is a preset and automatic system.
Nerve impulses are sent to the respiratory center to indicate When the lungs are inflated to a certain point. The muscle contractions that produce inspiration are stopped. The muscle contractions that produce expiration are initiated. The Respiratory System
Another set of nerve impulses are sent when the lungs deflate to a certain point.
Expiration is stopped and the the process of inspiration begins.
• The net effect is normal, rhythmic, resting breathing baseline pattern. The Respiratory System
• The chemical control system for breathing affects the breathing pattern only when something is out of balance. This will help make necessary adjustments to maintain homeostasis.
• Chemical receptors in the carotid artery, the aorta, and the brain stem monitor the CO2, O2, and pH (H+) of the blood. The Respiratory System
• The blood levels of CO2 and the blood pH are usually linked.
• Increases of CO2 in the blood deceases the pH, makes the blood more acidotic, and triggers the respiratory center to increase the rate and depth of respiration. This decreases the CO2 in the blood, increase the O2, and makes the blood more alkalotic. The Respiratory System
• Decreased levels of CO2 in the blood increases the blood pH. The blood becomes more alkalotic.
• Decreased CO2 in the blood triggers the respiratory center to decrease the rate and depth of respiration.
• This is usually measured by arterial blood gasses or by the use of a capnograph.
The Respiratory System
• Oxygen variations in the blood are not as clear cut as with CO2.
• With a slight hypoxia the respiratory center will increase the rate and depth of respiration.
• With a severe hypoxia neurons of the respiratory center become so depressed that they cannot send impulses to the respiratory muscles. This can cause breathing to decrease or stop completely.