Human Biology Lecture 11: Respiratory System PDF

Human Biology Lecture 11: Respiratory System Functions: provide oxygen to body tissues by cellular respiration, remove the waste product carbon dioxide help to maintain acid-base balance. non-vital functions, such as sensing odors, speech production, and coughing Respiration: Cellular respiration is...

Human Biology Lecture 11: Respiratory System Functions: provide oxygen to body tissues by cellular respiration, remove the waste product carbon dioxide help to maintain acid-base balance. non-vital functions, such as sensing odors, speech production, and coughing Respiration: Cellular respiration is the release of energy from the breakdown of food in the presence of oxygen respiration is the process of gas exchange the release of carbon dioxide and the uptake of oxygen that occurs between RBCs and alveoli Breathing is the actual mechanical intake of air Respiratory system: Consists of a tube that divides into small branching tubes in the lungs: External nares → nasal cavity → nasaopharynx → laryngopharynx → larynx → trachea → primary bronchi → lungs (secondary bronchi → tertiary bronchi → bronchioles →alveolar sacs → alveoli). The Nose and its Adjacent Structures : ❖ major entrance and exit via the nostrils. ❖ separated into left and right sections by the nasal septum. ❖ The wall of the nasal cavity has three bony projections, the superior, middle, and inferior nasal conchae. ❖ Conchae serve to increase the surface area of the nasal cavity and to disrupt the flow of air as it enters the nose, causing air to bounce along the epithelium, where it is inflitered, warmed, and humidified. Sinuses : air-containing spaces within bones. warm and humidify incoming air. lined with a mucosa. Each sinus is named for its associated bone: frontal sinus, maxillary sinus, sphenoidal sinus, and ethmoidal sinus. The sinuses produce mucus and lighten the weight of the skull. Nasal cavity: ❖ Portions of the nasal cavities are lined with mucous membranes, containing sebaceous glands and hair follicles that serve to prevent the passage of large debris, such as dirt, through the nasal cavity. ❖ The epithelium contains goblet cells to produce mucus to trap debris. The Nose and its Adjacent Structures : Pharynx: ❖ A tube formed by skeletal muscle ❖ divided into three major regions: the nasopharynx, the oropharynx, and the laryngopharynx ❖ The nasopharynx is flanked by the conchae of the nasal cavity, and it serves only as an airway. ❖ A pharyngeal tonsil at the top of nasopharnyx, also called an adenoid, contains lymphocytes and is covered with ciliated epithelium that traps and destroys invading pathogens that enter during inhalation Pharynx: ❖ The uvula is a small teardrop-shaped structure located at the apex of the soft palate. ❖ Both the uvula and soft palate move like a pendulum during swallowing, swinging upward to close off the nasopharynx to prevent ingested materials from entering the nasal cavity. ❖ auditory (Eustachian) tubes that connect to each middle ear cavity open into the nasopharynx. This connection is why colds often lead to ear infections. Pharynx: ❖ The oropharynx is a passageway for both air and food. contains two distinct sets of tonsils, the palatine and lingual tonsils. ❖ the palatine and lingual tonsils are composed of lymphoid tissue, and trap and destroy pathogens entering the body through the oral or nasal cavities. ❖ The laryngopharynx continues the route for ingested material and air until its inferior end ❖ To the front , the laryngopharynx opens into the larynx, whereas to the back, it enters the esophagus. Pharynx: Larynx: ❖ ❖ ❖ ❖ connects the pharynx to the trachea helps regulate the volume of air that enters and leaves the lungs. formed by several pieces of cartilage The epiglottis, attached to the thyroid cartilage, is a very flexible piece of elastic cartilage that covers the opening of the trachea. Larynx: ❖ The glottis is composed of the vestibular folds, the true vocal cords, and the space between these folds ❖ The inner edges of the true vocal cords are free, allowing oscillation to produce sound. ❖ The size of the membranous folds of the true vocal cords differs between individuals, producing voices with different pitch ranges. ❖ Folds in males is larger than those in females, which create a deeper voice. Larynx: Trachea: ❖ extends from the larynx toward the lungs. ❖ formed by 16 to 20 stacked pieces of cartilage that are connected by connective tissue. ❖ The fibroelastic membrane of the trachea allows it to stretch and expand slightly during inhalation and exhalation, whereas the rings of cartilage provide structural support and prevent the trachea from collapsing. Bronchi and Bronchioles: ❖ The right and left primary bronchi branch off the trachea towards the right and left lungs. ❖ The primary bronchi further branch into the secondary and tertiary bronchi. ❖ A bronchiole branches from the tertiary bronchi. ❖ Bronchioles further branch until they become the tiny terminal bronchioles, which lead to the structures of gas exchange. Bronchi and Bronchioles: ❖ Only the primary bronchi are external to the lungs, ❖ the rest of the bronchial tree is embedded in lung tissues. ❖ diameters of the tubes from primary bronchi to tertiary bronchi are large, so that support with cartilage rings is necessary. ❖ diameter at the bronchioles is down to 1 mm where the tubes do not need cartilage rings for support. This structure is composed of cuboidal cells where diffusion is also not possible. Bronchi and Bronchioles: ❖ from the alveolar duct to the alveoli, the lining tissue becomes simple squamous epithelium where gas exchange is possible. ❖ There are more than 1000 terminal bronchioles in each lung. ❖ smooth muscle can change the size of the tubing to increase or decrease air flow through it. Alveoli: ❖ A network of capillaries surrounds each alveolus. ❖ An alveolus have elastic walls that allow the alveolus to stretch during air intake, which greatly increases the surface area available for gas exchange. ❖ Alveoli are connected to their neighbors by alveolar pores, which help maintain equal air pressure throughout the alveoli and lung. ❖ Oxygen diffuses into the blood. ❖ Carbon dioxide in the blood diffuses into the alveolus. Lung: ❖ Cone – shaped organs located in the thoracic cavity. ❖ Thoracic cavity is lined with parietal pleura, while the surface of lungs is covered with visceral pleura. ❖ pleural cavity between the two pleural membranes filled with plural fluid to minimize friction between the tissues and to provide surface tension in the pleural cavity. ❖ surfactant secreted by the lungs also facilitate the surface tension. Lung: Gas exchange: ❖ gases present as a mixture of different types of molecules. ❖ The atmosphere consists of oxygen, nitrogen, carbon dioxide, and other gaseous molecules, this gaseous mixture exerts a certain pressure referred to as atmospheric pressure ❖ Partial pressure (Px) is the pressure of a single type of gas in a mixture of gases. ❖ Total pressure is the sum of all the partial pressures of a gaseous mixture. Gas exchange: ❖ The Gas law states that gas molecules always diffuse from a higher pressure area to a lower pressure area. ❖ The Boyle's law states that pressure and volume are inversely related (with the temperature remains constant), where pressure will increase in a smaller volume of gases, and pressure decreases in a larger volume of gases Inspiration (Inhalation) ❖ An active process where nerve impulses from medulla oblongata cause the contraction of diaphragm and external intercostals muscles. ❖ As these muscles contract, thoracic volume increases which decreases the pressure within the lung (intraalveolar pressure) ❖ When intraalveolar pressure falls below the atmospheric pressure (758 mmHg versus 760 mmHg, respectively), gases move from the environment into lungs Expiration (exhalation) ❖ a passive process where elastic tissues of the lungs and diaphragm recoil to their original position. ❖ as the diaphragm and external intercostals muscles relax and recoil, thoracic volume decreases which raises the intra alveolar pressure ❖ when intraalveolar pressure is risen above the atmospheric pressure (762 mmHg versus 760 mmHg, respectively), gases move from the lungs into the environment Gas exchange: ❖ Gases (particularly O2 and CO2 always diffuse from high pressure to low pressure. ❖ the directions of diffusion during gas exchange in the lungs and in body tissues are based on the differences in partial pressure of these gases. the greater the partial pressure difference between the two areas, the more rapid is the movement of gases Gas exchange: ❖ 98% of O2 is transported by binding to hemoglobin in erythrocytes as oxyhemoglobin (oxy-Hb) ❖ The resulting oxyhemoglobin is relatively unstable and releases its O2 in regions where Po2 is low. ❖ The efficiency of oxy-Hb releasing O2 to tissue cells during internal respiration is shown on the O2 -Hb dissociation curve which shows sigmoid shape Terms: Anoxia: absence or a deficiency of O2 within tissues. Dyspnea: difficulty in breathing. Hypoxia: diminished availability of O2 in the tissues. Tachypnea: rapid, shallow breathing. Respiratory System Disorder: Asthma ❖ affects the lungs in adults and children. ❖ a chronic disease characterized by inflammation and fluid accumulation of the airway, and bronchospasms ( constriction of the bronchioles), which can inhibit air from entering the lungs. ❖ excessive mucus secretion can occur, which further contributes to blockage of the airway. ❖ Respiratory System Disorder: Asthma ❖ Bronchospasms occur periodically and lead to an asthma attack. Asthma ❖ An attack may be triggered by environmental factors such as dust, pollen, pet hair, or dander, changes in the weather, mold, tobacco smoke, and respiratory infections, or by exercise and stress. ❖ Symptoms of an asthma attack involve coughing, shortness of breath, wheezing, and tightness of the chest. Asthma Respiratory Rate: ❖ the total number of breaths each minute. ❖ important indicator of disease, may increase or decrease during disease condition. ❖ controlled by the respiratory center located within the brain, which responds primarily to changes in carbon dioxide, oxygen, and pH levels in the blood. ❖ the normal rate of adults 12 to 18 breaths per minute.