The Trachea and Lungs PDF

ANATOMY OF RESPIRATORY SYSTEM The trachea and Lungs By: Dr. Shahnaz Sabetkam Assistant Professor of Anatomical Sciences Kyrenia University  Trachea A flexible, slightly rigid tubular organ often ref...

ANATOMY OF RESPIRATORY SYSTEM The trachea and Lungs By: Dr. Shahnaz Sabetkam Assistant Professor of Anatomical Sciences Kyrenia University  Trachea A flexible, slightly rigid tubular organ often referred to as the “windpipe.” Extends through the mediastinum immediately anterior to the esophagus inferior to the larynx superior to the primary bronchi of the lungs. Anterior and lateral walls of the trachea are supported by 15 to 20 C-shaped tracheal cartilages. cartilage rings reinforce and provide some rigidity to the tracheal wall to ensure that the trachea remains open (patent) at all times cartilage rings are connected by elastic sheets called anular ligaments 3  Trachea At the level of the sternal angle, the trachea bifurcates into two smaller tubes, called the right and left primary bronchi. Each primary bronchus projects laterally toward each lung. The most inferior tracheal cartilage separates the primary bronchi at their origin and forms an internal ridge called the carina. 25-4  Carina Carina is the cartilaginous projection of the last tracheal ring and lies between the orifices of the main bronchi. Carina is quite sensitive to irritation (cough reflex).  Trachea Extends from the inferior end of larynx C6 to T4-T5 Terminates by dividing into right and left main bronchi Division is called ‘tracheal bifurcation’ at the level of T4 is the inner projection  Trachea Trachea is formed of tracheal rings which are incomplete posteriorly Posterior parts of the tracheal rings are closed by smooth muscle called the trachealis muscle Trachea is enclosed with a fibroelastic membrane This membrane thickens between the tracheal rings to form anular ligaments (tracheal ligaments) between the adjacent rings Trachea Pars cervicalis Pars thoracica Posterior to the trachea is the esophagus  Bronchi ✓ Tubes that branch off trachea and enter into lungs ✓ Ciliated ✓ Branches: Primary bronchi— secondary bronchi—tertiary bronchi—bronchioles ✓ Bronchioles branch into microscopic alveolar ducts. ✓ Terminate into alveolar sacs ✓ Gas exchange with blood occurs in sacs.  Bronchi Tree A highly branched system air-conducting passages originate from the left and right primary bronchi. Progressively branch into narrower tubes as they diverge throughout the lungs before terminating in terminal bronchioles. Primary bronchi Incomplete rings of hyaline cartilage ensure that they remain open. Right primary bronchus shorter, wider, and more vertically oriented than the left primary bronchus. Foreign particles are more likely to lodge in the right primary bronchus. 2 5-  Bronchi Tree Primary bronchi E to lodge in nter the hilum of each lung Also entering hilum: pulmonary vessels lymphatic vessels nerves. Secondary bronchi (or lobar bronchi) Branch of primary bronchus left lung: two lobes two secondary bronchi right lung three lobes three secondary bronchi. Tertiary bronchi (or segmental bronchi) Branch of secondary bronchi left lung is supplied by 8 to 10 tertiary bronchi. right lung is supplied by 10 tertiary bronchi supply a part of the lung called a bronchopulmonary segment. 25-10  ,Main Lobar bronchus bronchus Segmental bronchus Branching of the bronchial tree Bronchi Tree Trachea Principal bronchus Lobar bronchi (secondary bronchi) Segmental bronchi (tertiary bronchi) Terminal bronchiol Respiratory bronchiol Alveolar duct Alveolar sac Alveolus ✓ Each main bronchus enters the root of a lung and passes through the hilum into the lung itself. ✓ The right main bronchus is wider and takes a more vertical course through the root and hilum than the left main bronchus. ✓ Therefore, inhaled foreign bodies tend to lodge more frequently on the right side than on the left. ✓ The main bronchus divides within the lung into lobar bronchi (secondary bronchi), each of which supplies a lobe. ✓ On the right side, the lobar bronchus to the superior lobe originates within the root of the lung. ✓ The lobar bronchi further divide into segmental bronchi (tertiary bronchi), which supply bronchopulmonary segments. ✓ Within each bronchopulmonary segment, the segmental bronchi give rise to multiple generations of divisions and, ultimately, to bronchioles, which further subdivide and supply the respiratory surfaces. ✓ The walls of the bronchi are held open by discontinuous elongated plates of cartilage, but these are not present in bronchioles. 13  Conducting and respiratory zones The airway undergoes about 16 generations of branching between trachea and respiratory bronchioles. This is a situation where each generation of branches has a lower flow resistance than the previous one. The basic functional unit of the lung is an acinus (pl. acini) - a group of alveoli served by a single terminal bronchiole. Each alveolus is a thin walled sac that is densely surrounded by pulmonary capillaries. Trachea