Anatomy: Lower Respiratory Tract (3rd lecture) PDF

First year, Second semester, Anatomy subject.((4)). 3rd lecture Lower respiratory tract Pharynx: a passage that contains the intersection between the esophagus and the larynx,. Larynx: has a special flap of cartilage, the epiglottis, that opens to allow air to pa...

First year, Second semester, Anatomy subject.((4)). 3rd lecture Lower respiratory tract Pharynx: a passage that contains the intersection between the esophagus and the larynx,. Larynx: has a special flap of cartilage, the epiglottis, that opens to allow air to pass through but closes to prevent food from moving into the airway. Function: conduction, airway protection, sound production. Cartilages Unpaired (3): Cricoid, thyroid, and epiglottis Paired (3): Arytenoid, corniculate, and cuneiform Cavity structure Three parts: Vestibule, middle part, infraglottic cavity. Glottis: Vocal folds, rima glottidis larynx, air moves into the trachea and down to the intersection known as the carina that branches to form the right and left primary (main) bronchi. Each of these bronchi branches into a secondary (lobar). Bronchus; that branches into tertiary (segmental) bronchi, then divided in to smaller airways branches; called bronchioles, that eventually connect with tiny specialized structures; called alveoli that function in gas exchange. The trachea ( the windpipe), is a cartilaginous tube that connects the larynx to the bronchi of the lungs, allowing the passage of air. The trachea is fixed in its position over time. It is epithelium lined with column-shaped cells that have hair-like extensions called cilia, with scattered goblet cells that produce protective mucins The trachea; has an inner diameter of about 1.5 to 2 cm, and a length of about 10 to 11 cm , wider in males than females. The trachea begins at the lower edge of the cricoid cartilage of the larynx at the level of sixth cervical vertebra (C6), and ends at the carina, the point where the trachea branches into left and right main bronchi. at the level of the fourth thoracic vertebra (T4), although its position may change with breathing. The trachea is surrounded by 16–20 rings of hyaline cartilage; these 'rings' are 4 milli high in the adult, incomplete and C-shaped. Ligaments connect the rings. The trachealis muscle connects the ends of the incomplete rings and runs along the back wall of the trachea. Adventitia, which is the outermost layer of connective tissue that surrounds the hyaline cartilage contributes to the trachea's ability to bend and stretch with movement. Lungs: which are located in the thoracic cavity, are protected from physical damage by the rib cage. At the base of the lungs is a sheet of skeletal muscle called the diaphragm. The diaphragm separates the lungs from the stomach and intestines. The diaphragm is also the main muscle of respiration involved in breathing, and is controlled by the sympathetic nervous system. The lungs; Are the largest organs in the lower respiratory tract. The lungs are suspended within the pleural cavity of the thorax. The pleurae are two thin membranes, one cell layer thick, which surround the lungs. The inner (visceral pleura) covers the lungs and the outer (parietal pleura) lines the inner surface of the chest wall. The lungs: are divided into different lobes. The right lung is larger in size than the left, because of the heart's being situated to the left of the midline. The right lung has three lobes – upper, middle, and lower (or superior, middle, and inferior), and the left lung has two – upper and lower (or superior and inferior), plus a small tongue-shaped portion of the upper lobe known as the lingula. The alveoli: Are tiny air sacs in the lungs where gas exchange takes place. The mean number of alveoli in a human lung is 480 million. When the diaphragm contracts, a negative pressure is generated in the thorax and air rushes in to fill the cavity, sacs fill with air, When the diaphragm relaxes, a positive pressure is generated in the thorax and air rushes out of the alveoli expelling the carbon dioxide.  Alveoli Alveolar cells, Membrane: type 1 pneumocyte, thin membrane for gas exchange squamous alveolar cells, 2 pneumocyte, secrete pulmonary surfactant. Basement membrane, Capillary endothelium Respiratory membrane. Squamous alveolar cell, Basement membrane, Capillary endothelium.