Anatomy and Physiology Lecture Notes PDF

**IQARA COLLEGE OF NURSING SCIENCES DUTSE, JIGAWA STATE.** **SCHOOL OF NURSING** **ANATOMY AND PHYSIOLOGY LECTURE MATERIAL 4 SET 3 STUDENTS NURSES** **SECOND YEAR SECOND SEMESTER DECEMBER, 2024** **PREPARED BY YUSUF SALE, BSc. {ABU}.** - **THE RESPIRATORY SYSTEM** Most metabolic processes of...

**IQARA COLLEGE OF NURSING SCIENCES DUTSE, JIGAWA STATE.** **SCHOOL OF NURSING** **ANATOMY AND PHYSIOLOGY LECTURE MATERIAL 4 SET 3 STUDENTS NURSES** **SECOND YEAR SECOND SEMESTER DECEMBER, 2024** **PREPARED BY YUSUF SALE, BSc. {ABU}.** - **THE RESPIRATORY SYSTEM** Most metabolic processes of the body depend on ATP, and most ATP produc- tion requires oxygen and generates carbon dioxide as a waste product. The respiratory and cardiovascular systems collaborate to provide this oxygen and remove the carbon dioxide. Not only do these, the two systems have a close spatial relationship in the thoracic cavity, they also have such a close functional relationship that they are often considered jointly under the heading cardiopulmonary system. A disorder that affects the lungs has direct and pronounced effects on the heart, and vice versa. The respiratory system functions as an air distributor and a gas exchanger, so that oxygen can be supplied to and carbon dioxide removed from the body's cells. Because most of our trillions of cells lie too far from air to exchange gases directly with it, air must first exchange gases with blood, blood must circulate, and finally, blood and cells must exchange gases. These events require the functioning of two systems, namely, the respiratory system and the circulatory system as mentioned earlier. All parts of the respiratory system - except its microscopic-sized sacs called alveoli - function as air distributors. Only the alveoli and the tiny alveolar ducts that open into them serve as gas exchangers. In addition to air distribution and gas exchange, the respiratory system effectively filters, warms, and humidifies the air we breathe. Respiratory organs also help produce sounds, including speech used in communicating oral language. Special sensory epithelium in the respiratory tract makes the sense of smell (olfaction) possible. Furthermore, the respiratory system works closely with the urinary system to regulate the body's acid-base balance. Changes in the blood pH, in turn, trigger autonomic adjustments of the heart rate and blood pressure. Thus, the cardiovascular, respiratory, and urinary systems have an especially close physiological relationship. - **PHSIOLOGIC ANATOMY OF RESPIRATORY TRACT** Respiratory tract is the anatomical structure through which air moves in and out. It includes nose, pharynx, larynx, trachea, bronchi and lungs. The major organs of the respiratory system function primarily to provide oxygen to body tissues for cellular respiration, remove the waste product carbon dioxide, and help to maintain acid-base balance. Portions of the respiratory system are also used for other vital functions, such as straining that aid during childbirth or coughing. **FIGURE: Respiratory tract** - **DIVISION OF RESPIRATORY TRACT** Generally, respiratory tract is divided into two parts: 1\. Upper respiratory tract: that includes all the structures from nose up to vocal cords. That is, the respiratory organs in the head and neck region. 2\. Lower respiratory tract: which includes trachea, bronchi and lungs. That is, the respiratory organs in the thoracic region. NON-RESPIRATORY FUNCTIONS OF RESPIRATORY TRACT Besides primary function of gaseous exchange, the respiratory tract is involved in several non-respiratory functions of the body, particularly the lungs. These include: 1\. OLFACTION: Olfactory receptors present in the mucous membrane of nostril are responsible for olfactory sensation. 2\. VOCALIZATION: Along with other structures, larynx forms the speech apparatus. However, larynx alone plays major role in the process of vocaliza- tion. Therefore, it is called sound box. 3\. PREVENTION OF DUST PARTICLES: Dust particles, which enter the nostrils from air, are prevented from reaching the lungs by filtration action of the hairs in nasal mucous membrane. Small particles, which escape the hairs, are held by the mucus secreted by nasal mucous membrane. Those dust particles, which escape nasal hairs and nasal mucous membrane, are removed by the phagocytic action of macrophages in the alveoli. Particles, which escape the protective mechanisms in nose and alveoli are thrown out by cough reflex and sneezing reflex. 4\. DEFENSE MECHANISM: Lungs play important role in the immunological defense system of the body. Defense functions of the lungs are performed by their own defenses and by the presence of various types of cells in mucous membrane lining the alveoli of lungs. These cells are leukocytes, macrophages, mast cells, natural killer cells and dendritic cells. 5\. MAINTENANCE OF WATER BALANCE: Respiratory tract plays a role in water loss mechanism. During expiration, water evaporates through the expired air and some amount of body water is lost by his process. 6\. REGULATION OF BODY TEMPERATURE: During expiration, along with water, heat is also lost from the body. Thus, respiratory tract plays a role in heat loss mechanism. 8\. ANTICOAGULANT FUNCTION: Mast cells in lungs secrete heparin. Heparin is an anticoagulant and it prevents the intravascular clotting. 9\. SECRETION OF ANGIOTENSINCONVERTING ENZYME: Endothelial cells of the pulmonary capillaries secrete the angiotensin converting enzyme (ACE). It converts the angiotensin I into active angiotensin II, which plays an important role in the regulation of ECF volume and blood pressure. **ROLES OF RESPIRATORY ORGANS** **1. THE NOSE** The nose has several functions: it warms, cleanses, and humidifies inhaled air; it detects odors in the airstream; and it serves as a resonating chamber that amplifies the voice. The major entrance and exit for the respiratory system is through the nose. When discussing the nose, it is helpful to divide it into two major sections: the external nose, and the nasal cavity or internal nose. - The external nose consists of the surface and skeletal structures that result in the outward appearance of the nose and contribute to its numerous functions. On either side, the nostrils are formed by the alae (a cartilaginous structure that forms the lateral side of each nostril opening). In other words, the external protruding part of the nose is supported and shaped by a frame- work of bone and cartilages. - **INTERNAL STRUCTURE OF THE NOSE** The nasal septum divides the nasal cavity into right and left chambers called nasal fossa. It is lined with stratified squamous epithelium (respiratory epithelium) and has guard hairs that block the inhalation of large particles. The olfactory mucosa lines the roof of the nasal fossa. The rest of the cavity is lined by ciliated pseudostratified respiratory mucosa. The cilia of the respiratory epithelium help remove the mucus and debris from the nasal cavity with a constant beating motion, sweeping materials towards the throat to be swallowed and digested. Interestingly, cold air slows the movement of the cilia, resulting in accumulation of mucus that may in turn lead to a runny nose during cold weather. This moist epithelium functions to warm and humidify incoming air. The nasal mucosa has an important defensive role, in which goblet cells and glands in the epithelium secrete a layer of mucus that traps inhaled particles, so that Bacteria are destroyed by lysozyme in the mucus. The palate separates the nasal cavity from the oral cavity and allows you to breathe while there is food in your mouth. Several bones that help form the walls of the nasal cavity have air-containing spaces called the paranasal sinuses, which serve to warm and humidify incoming air. Sinuses are lined with a mucosa. Each paranasal 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. **2. THE PHARYNX** The pharynx is a funnel tube of about 13cm long, formed by skeletal muscle and lined by mucous membrane that is continuous with that of the nasal cavities. The pharynx is divided into three major regions: the nasopharynx, the oropharynx, and the laryngopharynx. **The nasopharynx:** it serves only as an airway passage. Its superior end is demarcated by soft palate. Soft palate moves like a pendulum during swallowing, swinging upward to close off the nasopharynx to prevent ingested materials from entering the nasal cavity. In addition, auditory (Eustachian) tubes that connect to each middle ear cavity open into the nasopharynx. This connection is why colds often lead to ear infections. At the top of the nasopharynx are the pharyngeal tonsils (an aggregate of lymphoid tissue similar to a lymph node) contains a rich supply of lymphocytes that traps and destroys invading pathogens that enter during inhalation. The **oropharynx:** is a passageway for both air and food. The oropharynx is bordered superiorly by the nasopharynx and anteriorly by the oral cavity. As the nasopharynx becomes the oropharynx, the epithelium changes from pseudostratified ciliated columnar epithelium to stratified squamous epithelium. The oropharynx contains two distinct sets of tonsils, the palatine and lingual tonsils. Similar to the pharyngeal tonsil, 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:** is inferior to the oropharynx and posterior to the larynx. It continues the route for ingested material and air until its inferior end, where the digestive and respiratory systems diverge. The stratified squamous epithelium of the oropharynx is continuous with the laryngopharynx. Anteriorly, the laryngopharynx opens into the larynx, whereas posteriorly, it enters the esophagus. 3\. **THE LARYNX** The larynx is a cartilaginous structure (a chamber of 4cm long) inferior to the laryngopharynx that connects the pharynx to the trachea and helps regulate the volume of air that enters and leaves the lungs. Its primary function is to keep food and drink out of the airway, but it has evolved the additional role of producing sound. The structure of the larynx is formed by several pieces of cartilage. Three large cartilage pieces---the thyroid cartilage, epiglottis, and cricoid cartilage---form the major structure of the larynx. The superior opening of the larynx- the glottis is guarded by a flap of tissue called the **epiglottis.** During swallowing, muscles of the larynx pull the larynx upward toward the epiglottis, the tongue pushes the epiglottis downward to meet it, and the epiglottis directs food and drink into the esophagus dorsal to the airway. 4\. **THE TRACHEA AND BRONCHI** The trachea (windpipe) is a rigid tube, about 12cm long and 2.5cm diameter that extends from the larynx toward the lungs. It lying anterior to the esophagus. The trachea is formed by several C-shaped pieces of hyaline cartilage that are connected by dense connective tissue. The trachealis muscle and elastic connective tissue together form the fibroelastic membrane on the tracheal surfaces. The membrane allows the trachea to stretch and expand slightly during inhalation and exhalation, whereas the rings of cartilages provide structural support and prevent the trachea from collapsing. The trachealis muscle can contract or relax to adjust tracheal airflow, and also allows room for the esophagus to expand as swallowed food passes by. The trachea is lined with pseudostratified ciliated columnar epithelium, which is continuous with the larynx. The esophagus borders the trachea posteriorly. At its inferior end, the trachea branches into the right and left primary bronchi, which supply the lungs. **5. THE LUNGS** - **GROSS FEATURES:** Each lung is a somewhat conical organ with a broad, concave base resting on the diaphragm and a blunt peak called the apex projecting slightly superior to the clavicle. The broad costal surface is pressed against the rib cage, and the smaller concave mediastinal surface faces medially. The lungs do not fill the entire rib cage. Inferior to the lungs and diaphragm, much of the space within the rib cage is occupied by the liver, spleen, and stomach. The lung receives the bronchus, blood vessels, lymphatic vessels, and nerves through its hilum in the mediastinal surface. These structures entering the hilum constitute the root of the lung. Because the heart tilts to the left, the left lung is a little smaller than the right and has an indentation called the cardiac notch to accommodate the heart. The left lung has a superior lobe and an inferior lobe with a deep fissure between them; while the right lung by contrast has three lobes---superior, middle, and inferior separated by two fissures. - **HISTOLOGICAL FEATURES:** **THE PLEURA:** Each lung is enclosed by a bilayered serous membrane called pleura or pleural sac. Pleura has two layers namely inner visceral and outer parietal layers. Visceral layer is attached firmly to the surface of the lungs. At hilum, it is continuous with parietal layer, which is attached to the wall of thoracic cavity. - Intrapleural Space: Intrapleural space or pleural cavity is the narrow space in between the two layers of pleura. - Intrapleural Fluid: Intrapleural space contains a thin film of serous fluid called intrapleural fluid, which is secreted by the visceral layer of the pleura. - Functions of intrapleural fluid: 1\. It functions as the lubricant to prevent friction between two layers of pleura 2\. It is involved in creating the negative pressure called intrapleural pressure within intrapleural space. - Pleural Cavity in Abnormal Conditions: In some pathological conditions, the pleural cavity expands with accumulation of air (pneumothorax), water (hydrothorax), blood (hemothorax) or pus (pyothorax). - **THE TRACHEOBRONCHIAL TREE** Trachea and bronchi are together called tracheobronchial tree. This is a highly branched system of air tubes extending from the primary bronchus to large number of terminal bronchioles and forms part of air passage. Two primary bronchi arise from the trachea and enters the hilum of its respective lung. The right bronchus is slightly wider and more vertical than the left; consequently, aspirated (inhaled) foreign objects lodge in the right bronchus more often than in the left. - Components of tracheobronchial tree: 1\. Trachea bifurcates into two main or primary bronchi called right and left bronchi 2\. Each primary bronchus enters the lungs and divides into secondary bronchi. After entering the hilum, the primary bronchus branches into one secondary (lobar) bronchus for each pulmonary lobe. Thus, there are two secondary bronchi in the left lung and three in the right. 3\. Secondary bronchi divide into tertiary (Segmental) bronchi. The portion of the lung supplied by each tertiary bronchus is called a bronchopulmonary segment. 4\. Tertiary bronchi divide several times with reduction in length and diameter into many generations of bronchioles 5\. When the diameter of bronchiole becomes 1 mm or less, it is called terminal bronchiole. 6\. Terminal bronchiole continues or divides into respiratory bronchioles, which have a diameter of 0.5 mm, and mark the beginning of the respiratory division. - **THE RESPIRATORY UNIT** The respiratory unit forms the terminal portion of respiratory tract. Respiratory unit is defined as the structural and functional unit of the lung. Exchange of gases occurs only in this part of the respiratory tract. - STRUCTURE OF RESPIRATORY UNIT: Respiratory unit starts from the respiratory bronchioles. Each respiratory bronchiole divides into alveolar ducts. Each alveolar duct enters an enlarged structure called the alveolar sac. Space inside the alveolar sac is called antrum. Alveolar sac consists of a cluster of alveoli. Few alveoli are present in the wall of alveolar duct also. Thus, respiratory unit includes: 1\. Respiratory bronchioles 2\. Alveolar ducts 3\. Alveolar sacs 4\. Antrum 5\. Alveoli. Each alveolus is like a pouch with the diameter of about 0.3 mm. It is lined by epithelial cells. All branches of the respiratory division are defined by the presence of alveoli. The respiratory bronchioles, each divide into many elongated thin-walled passages called alveolar ducts that end in alveolar sacs. The epithelium of the bronchial tree is pseudostratified columnar in the bronchi, simple cuboidal in the bronchioles, and simple squamous in the alveolar ducts, sacs, and alveoli. - ALVEOLAR CELLS OR PNEUMOCYTES Alveolar epithelium consists of alveolar cells or pneumocytes, which are of two types, namely type I alveolar cells and type II alveolar cells. - Type I alveolar cells: Type I alveolar cells are the squamous epithelial cells forming about 95% of the total number of cells. These cells form the site of gaseous exchange between the alveolus and blood. - Type II alveolar cells: Type II alveolar cells are cuboidal in nature and form about 5% of alveolar cells. These cells are also called granular pneumocytes. Type II alveolar cells secrete alveolar fluid and surfactant. - **RESPIRATORY MEMBRANE** Respiratory membrane is the membranous structure through which the exchange of gases occurs. Respiratory membrane separates air in the alveoli from the blood in capillary. It is formed by the **alveolar** **membrane** and **capillary membrane.** Therefore, the membrane of RBCs is in close contact with capillary wall. This facilitates quick exchange of oxygen and carbon dioxide between the blood and alveoli. In spite of having many layers, respiratory membrane is very thin with an average thickness of 0.5 μ **CLINICAL CORRELATION** - **ASTHMA:** Asthma is common condition that affects the lungs in both adults and children. Asthma is the most frequent cause of hospitalization in children. Asthma is a chronic disease characterized by inflammation and edema of the airway, and bronchospasms (constriction of the bronchioles), which can inhibit air from entering the lungs. In addition, excessive mucus secretion can occur, which further contributes to airway occlusion. Cells of the immune system, such as eosinophils and mononuclear cells, may also be involved in infiltrating the walls of the bronchi and bronchioles. Bronchospasms occur periodically and lead to an "asthma attack." An attack may be triggered by environmental factors such as dust, changes in the weather, tobacco smoke, respiratory infections, or by exercise and stress. Symptoms of an asthma attack involve coughing, shortness of breath and tightness of the chest.