9The Lower Respiratory Tract The TRACHEA begins at the level of C6 superiorly.Directly superior to the beginning of the trachea is the LARYNX (vocal cords).The trachea bifurcates into the BRONCHI at the sternal angle (T4 or T5) when supine (laying on the back) or T7 when standing.
10The trachea is composed of 16-20 cartilagenous rings (hyaline cartilage). These rings are flexible but keep the trachea open.Each ring is open in the back (allows flexibility)
11The rings are approximately 1 The rings are approximately 1.5 inches in diameter and held together by connective tissue.The connective tissue is dense CT.Air can pass through the tube without resistance.
12The trachea must be able to filter debris (dust or dirt) The trachea must be able to filter debris (dust or dirt). Coughing occurs when such debris enters the trachea.This coughing is due to the CILIATED EPITHELIUM which lines the trachea.
13Histology of the trachea Ciliated epitheliumcartilage
14The LarynxThe LARYNX (voice box) is a modified portion of the trachea.It is superior to the trachea.There are cartilaginous rings that are connected by dense connective tissue forming a tube.
15The TYROID CARTILAGE is shaped like a shield when viewed from the anterior surface. This is the ADAM’S APPLE. This is not a complete ring.On the posterior side of the thyroid cartilage, the CRICOID CARTILAGE extends superiorly to where the thyroid cartilage would be. This cartilage is sometimes called the SIGNET RING CARTILAGE.
16It has a narrow band across the anterior side. It is superficial to the thyroid cartilage posteriorly where it is connected by the CRICOTHYROID LIGAMENT (dense connective tissue).Inferiorly, the cricoid is attached to the first ring to the trachea by dense CT.
17The EPIGLOTTIS is a spade shade cartilage that is important during swallowing. It tips inferiorly to seal off the glottis and prevents food from entering the trachea.The ARYTENOID CARTILAGE is below the epiglottis at the entrance to the GLOTTIS.The GLOTTIS is a passageway into the trachea. The thyroid cartilage forms the walls of the glottis. The arytenoid cartilage extends inferiorly into the glottis.
18The arytenoid cartilages anchor the vocal cords. The true vocal cords are located inferiorly inside the glottis.As air passes over the vocal cords they flutter, producing sound from the vibration.Pitch can be changed by tightening or loosening the cords.In humans, the tongue is used to make sense of the sounds (make words). You cannot talk if your tongue is not functioning.There are folds covering part of the epiglottis called FALSE VOCAL CORDS.
23Step 2The skin incision is made with a Colorado Needle mounted on an electric knife (Bovie). A steel blade scalpel is as good and is preferred by many surgeons.
24Step 3After incising the subcutaneous tissue and platysma, the strap muscles are separated in the midline.The strap muscles is a name given to the four infrahyoid muscles that lie in front of the larynx. They are the sternohyoid, sternothyroid, thyrohyoid and the omohyoid.
25Step 4The isthmus of the thyroid gland is either retracted or divided in the midline. (In this picture, the isthmus has been divided and retracted laterally, along with the strap muscles.) The anterior tracheal wall is divided between the third and fourth tracheal rings. A clamp is used to widen the tracheal opening. The endotracheal tube is seen inside the tracheal lumen
28Normal vocal cords as they appear through a 90 degree telescope Normal vocal cords as they appear through a 90 degree telescope. The cords are partially opened and the opening into the trachea can be seen between them.
29One may compare this person at a high and a low pitch, demonstrating the elongation of the vocal cords that takes place to raise pitch by contracting the Cricothyroid muscles
33Wider, shorter, and more vertical than the left tracheaRight Primary BronchusLeft primary bronchusBoth primary bronchi have the same anatomic structure as the trachea.
34The primary bronchi divide to form SECONDARY BRONCHI (lobar bronchi). There is one secondary bronchus for each lobe of the lungs.There are 2 lobes on the left lung.There are 3 lobes on the right lung.These also have the same anatomy as the trachea.
35The secondary bronchi branch to form TERTIARY BRONCHI. They continue to branch.As they get smaller, they lose their cartilage.When they lose their cartilage, they are called BRONCHIOLES which are microscopic.
39There are air sacs, where gas exchange occurs. Walls of the alveoli are highly vascularized.The alveoli are the terminal branches of the BRONCHIAL TREE. This arrangement allows for a drastic increase in surface area.
40The LungsThe right lung starts 1” above rib 1 and crosses the clavicle at about the medial 1/3 of it. It progresses inferiorly to costal cartilage 6 (midsternally). At the midaxillary region, it is at rib 8 and rib 10 at the vertebral border.
41The right lung has 3 lobes (4 in the cat). The left lung starts about 1” above rib 1 and crosses deep to the manubrioclavicular joint. There it goes to the left and continues inferiorly to rib 6.The left lung has an indentation called the CARDIAC NOTCH. This area provides room for the HEART.
42Lung size varies from individual to individual. The left lung has 2 lobes (3 in the cat).The lobes are anatomically and functionally separate. Thus, they are independent of each other.
43There is a deep fissure between the lobes There is a deep fissure between the lobes. The lobes overlap each other like shingles.The OBLIQUE FISSURE on each lobe begins posteriorly across from the root of the spine of the scapula at T3. They come around laterally and inferiorly in an oblique path and eventually reach rib 6 on both sides.
44On the right side, there is also a TRANSVERSE FISSURE which follows rib 4 anteriorly. It joins the oblique fissure midaxillary.On the posterior surface, one can see only 2 lobes on each lung. On the anterior surface, you can see the third lobe on the right lung.
46The lobes are further divided into LOBULES The lobes are further divided into LOBULES. These cannot be separated as easily as the lobes can.They are functionally separate.They are also anatomically partitioned to allow removal of a lobule while keeping the functionality of the rest of the lung.
49Gaseous exchange relies on simple diffusion Gaseous exchange relies on simple diffusion. In order to provide sufficient oxygen and to get rid of sufficient carbon dioxide there must bea large surface area for gaseous exchangea very short diffusion path between alveolar air and bloodconcentration gradients for oxygen and carbon dioxide between alveolar air and blood.
51Intercostal Muscles External Intercostals O: Inferior border of rib above I: Superior border of rib belowFibers run OBLIQUE (down and forward)Aid in Inspiration (lift ribcage, increase dimensions)Internal IntercostalsO: Superior border of rib above I: Inferior border of rib belowFibers run at RIGHT ANGLES to external intercostalsAid in expiration (depress ribcage, decrease dimensions)Innermost IntercostalsAttachments similar to Internal Intercostals, Attach ribsFibers run Anterior/Posterior
52Neurovascular Bundle of Intercostals VAN (vein, artery, nerve)Intercostal veinIntercostal arteryIntercostal nerveSit in Subcostal GrooveBetween Internal Intercostal and Innermost intercostal muscles
54During inspiration the diaphragm moves downward allowing air to enter the respiratory tract. The external intercostals contract along with the pectoral muscles.During Expiration, the diaphragm moves upward forcing air out the lungs. The internal intercostals contract.