The Thoracic Cavity

1. The Thoracic Cavity Boundaries of and Structures Within

2. Cavities • Dorsal body cavity • Ventral body cavity • Abdominopelvic • Abdominal • Pelvic • Divided by Diaphragm • Thoracic • 2 Pleural • Mediastinum www.newworldencyclopedia.org

3. Serous membrane = Serosa • Simple squamous epithelium + areolar connective tissue • 2 Layers • Outer layer = PARIETAL serosa • Inner layer = VISCERAL serosa • Between them = Serous Cavity containing Serous Fluid • Serous fluid is blood filtrate + secretions by 2 layers of membrane • Allows movement of organs with reduced friction • Types of Serous Membranes • Pleural = surrounds lungs • Pericardium = surrounds heart, slightly modified • Peritoneal = surrounds some abdominal organs

4. Pleural Cavities • Surround the lungs • Pleural fluid secreted by pleural membranes • Holds layers together • Reduces friction of organs • Compartmentalization pg 136

5. Pleural Cavities • 2 Layers • Parietal pleura (outer) • inner surface of thoracic wall • superior surface of diaphragm • lateral surface of mediastinum • Visceral pleura (inner) • root of lungs marks transition • external surface of lungs pg 137

6. Pleural Effusion Excess fluid in the pleural cavity More than 20X Usually less than 1 ml of fluid Pneumothorax Air located in pleural space Pleural Abnormalities www.rcjournal.com Pg 210 www.islamicboard.com

7. Divisions of Mediastinum • Superior (to heart) • Contains: thymus, cranial vena cava, trachea, esophagus • Inferior • Anterior (to heart) • Contains: thymus • Posterior (to heart) • Contains: aorta, esophagus, • trachea, bronchi, caudal vena cava • Middle • Contains: heart pg 153

8. Boundaries of Mediastinum • Lateral • parietal pleura of lungs • Anterior • ventral parietal pleura • Posterior • dorsal parietal pleura • Superior • dome of the neck • Inferior • diaphragmatic pleura pg 136

9. Respiratory Tract • Upper Respiratory Tract • Superior to Larynx • Lower Respiratory Tract • Larynx • Trachea • Primary Bronchi • Secondary Bronchi • Rest of Bronchial Tree • Lungs pg 944

10. Trachea = windpipe • Starts at Larynx and travels through mediastinum • Located Anterior to Esophagus • Trachea terminates into 2 primary bronchi entering lungs • Walls contain 16-20 “C” shaped rings Hyaline Cartilage • Trachealis Muscle (smooth muscle and soft CT) • Layers (deep to superficial) • Mucosa = Ciliated Psuedostratified Epithelium • Submucosa- contains seromucous glands • Adventitia – made of connective tissue, contains cartilage rings Pg 917

11. Bronchial Tree • Primary (main) Bronchi • Bifurcation of trachea • Basically the same structure • Cartilage plates replace rings • Posterior to pulmonary vessels • Right is wider, vertical, shorter • Secondary (lobar) Bronchi • Each primary bronchi divides • Same structure as primary bronchi • Right lung has 3, Left has 2 • Tertiary (segmental) Bronchi • Up to 23 divisions pg 145

12. Bronchial Tree (continued) • Bronchioles • further divisions, < 1 mm diameter • Terminal Bronchioles • further divisions, 0.5 mm diameter • Respiratory Zone • Respiratory Bronchioles • Alveolar Ducts • Alveolar Sacs • Terminal bunches of Alveoli • Respiratory exchange chamber

13. Respiratory Zone (continued) • Lining the Walls of Alveoli • Respiratory Membrane • Type I cells = simple squamous epithelial cells • Basal lamina and fine areolar CT • Covered with capillaries and elastic fibers • Gas exchange • Oxygen into blood • Carbon Dioxide into alveoli • Type II cells = cuboidal epithelial cells • Secrete fluid containing surfactant

14. Throughout Bronchial Tree • Psuedostratified columnar changes to simple columnar to simple cuboidal • Cartilage rings replaced by cartilage plates once bronchi enter the lungs • Smooth muscle and Elastic fibers remain important • In Bronchioles • Ciliated mucosa disappears, replaced by macrophages in alveoli • Cartilage disappears • Smooth muscle forms bands around smallest bronchi and bronchioles (not found around alveoli)

15. LUNGS (continued) • Located in Pleural Compartments • Lateral to Mediastinum • Location • Apex posterior to clavicle • Base lays on Diaphragm • Costal Surface = Ant, Lat, Post surfaces contact ribs • Left Lung = 2 lobes • Upper • Lower • Oblique Fissure • Cardiac Notch • Right Lung = 3 lobes • Upper • Middle • Lower • Oblique fissure • Horizontal fissure pg 145

16. LUNGS • Hilus- medial indentation • Root of Lung = structures enter each lung • 2 Pulmonary Veins = carries O2-rich blood from each lung to heart • 1 Pulmonary Artery = carries O2-poor blood to each lung • Primary Bronchus • Nerves – Lymph Vessels pg 141

17. Right Lung 1” above Rib 1 Crosses Costal Cartilage 6 Midclavicular at Rib 6 Midaxillary at Rib 8 Vertebral Border at Rib 10 Inferior border 2 rib widths above diaphragm Left Lung 1” above Rib 1 Deep to Manubroclavicular joint Midsternally to Rib 4 Jogs to left, continues to Rib 6 Midaxillary Rib 8 Vertebral Border at Rib 10 Specific Location of Lungs

18. Lung Lobes • Lobes are anatomically + functionally separate • Lung lobes divided into Lobules • Functionally separate • Separated by dense CT • Vary in size • Stroma = lung tissue • CT • Many elastic fibers pg 155

19. Esophagus • Esophagus • Pharynx to Stomach • Passes thru diaphragm at esophageal hiatus • Anterior to vertebrae, Posterior to trachea • Layers of Esophagus (deep to superficial) • Mucosa • Stratified squamous epithelium • Lamina propria (loose CT) • Muscularis mucosae • Submucosa • Loose connective tissue • Secretes mucus • Muscularis Externa • Circular/Longitudinal layers • Skeletal m, Mix, then Smooth m • Adventitia • Fibrous CT pg 139

20. The Diaphragm • Skeletal Muscle • Dome-shaped (relaxed) • Flattens (contracts) • Divides thoracic & abdominopelvic cavities • Attachments • O: Inferior Internal rib cage, Lumbar vertebrae (by crura) • I: Central tendon • Innervated by right + left PHRENIC Nerves pg 114

21. Action of the Diaphragm • Primary muscle of respiration (involuntary) • Contraction during inspiration • Increases volume of thoracic cavity • Decreases pressure of thoracic cavity • Air moves into lungs (highlow pressure) • Forced contraction (voluntary) • Used for defecation, urination, labor • Decreases volume of abdominal cavity • Increases pressure in abdominal cavity • Pushes on abdominal organs to move contents out pg 114

22. Thoracic Cavity Capacity is Increased by: • Contraction of diaphragm • Intercostal muscles elevate ribs • Rib elevation causes the sternum to move anteriorly pg 113

23. Openings of Diaphragm • PosteriorAnterior • Aortic Hiatus • Aorta • Azygos vein • Thoracic duct • Esophageal Hiatus • Esophagus • Vagus nerve • Caval Opening • Inferior Vena Cava • Right Phrenic Nerves pg 134

24. Superior Vena Cava in Superior mediastinum, right side Receives blood from regions above diaphragm Formed from Rt + Lft Brachiocephalic Veins cranially Azygos Vein empties into it just superior to heart Empties into Right Atrium Inferior Vena Cava in Inferior mediastinum (right side), runs through abdomen Returns blood to heart from regions below diaphragm Formed from Rt + Lft Common Iliac Veins Empties into Right Atrium Widest blood vessel in body Vena Cava

25. Veins of Thoracic Cavity • Vena Cavae • Azygos Vein • “unpaired” • right side of vertebral bodies (at level of T12) • runs superiorly • empties into Sup. Vena Cava • drains right posterior intercostal veins • Connects to hemiazygos and accessory hemiazygos that drain left side pg 131

26. The Lymphatic Vessels • Function: to collect excess tissue fluid collecting at arteriole end of capillary beds, and return leaked blood proteins to blood (maintain osmotic pressure needed to take up water into bloodstream) • Lymph is moved through vessels • Pulse of nearby arteries • Contraction of surrounding skeletal muscle • Regular movement of body (wiggling legs) • Muscle in Tunica Media • Lacteals-lymphatic capillaries w/unique function • In mucosa of small intestine, receive digested fat from intestine • Fatty lymph becomes milky = Chyle • Chyle goes to bloodstream

27. Lymphatic System…The Players: • Lymph- clear fluid from loose CT at capillaries • Contains small molecules of blood plasma, water, various ions, nutrient molecules, respiratory gases • Lymphatic capillaries (near blood capillaries)  • Lymph collecting vessels (small, 3 tunicas, # valves) • Lymph nodes (sit along collecting vessels)-clean lymph of pathogens, they are NOT glands • Lymphatic trunks(convergence large collecting vessels) • Lymphatic ducts empty into veins of neck

28. Lymphatic Ducts • Thoracic Duct • Receives lymph from large trunks in abdomen and thorax • Receives lymph from ducts of thoracic lymph nodes • Along vertebral bodies • Contain valves to ensure 1-way flow of lymph to lymph nodes • Drains into left Brachiocephalic Vein (or subclavian or int. jugular veins) pg 132, 150

29. Thymus Gland • Lymphatic Organ • 2-lobed w/lobules • Sits on heart and great vessels • Immature lymphocytes mature into T-lymphocytes • Secretes Thymic Hormones: help T-lymphocytes gain immunocompetence • Decreases in size w/age • Functional tissue is replaced with fatty tissue pg 183

30. Increases in size during childhood Decreases in size during adulthood Contains lobes and lobules Capsule Cortex Medulla Thymus Gland