Boundaries of and Structures Within The Thoracic Cavity Boundaries of and Structures Within

Body Cavities Dorsal body cavity Ventral body cavity Thoracic Remove frame      Dorsal body cavity Ventral body cavity Thoracic 2 Pleural Mediastinum Divided by Diaphragm Abdominopelvic Abdominal Pelvic www.newworldencyclopedia.org/entry/Body_cavity

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

Pleural Cavities Surround the lungs Pleural fluid secreted by pleural membranes Holds layers together Reduces friction of organs Benefit of Compartmentalization pg 159

Pleural Cavities 2 Layers Visceral pleura (inner) root of lungs marks transition external surface of lungs Parietal pleura (outer) inner surface of thoracic wall superior surface of diaphragm lateral surface of mediastinum pg 161

Pleural Abnormalities Pleural Effusion Excess fluid in the pleural cavity More than 20X Usually less than 1 ml of fluid Pneumothorax Air located in pleural space Pg 238

Divisions of Mediastinum Superior (to heart) Contains: thymus, cranial vena cava, trachea, esophagus, nerves Inferior Anterior (to heart) Contains: thymus Posterior (to heart) Contains: aorta, esophagus, trachea, bronchi, nerves, caudal vena cava, Middle Contains: heart + pericardium pg 177

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 159

Respiratory Tract Upper Respiratory Tract Lower Respiratory Tract Superior to Larynx Lower Respiratory Tract Larynx Trachea Primary Bronchi Secondary Bronchi Rest of Bronchial Tree Lungs pg 992 pg 168

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 966

Bronchial Tree Primary (main) Bronchi Secondary (lobar) Bronchi Bifurcation of trachea Basically the same structure Cartilage 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 168

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 Among alveoli are blood vessels, nerves, lymphatics www.nlm.nih.gov/.../ency/imagepages/1103.htm

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 Type II cells = cuboidal epithelial cells Secrete fluid containing surfactant Dust Cells (macrophages) Gas exchange Oxygen into blood Carbon Dioxide into alveoli

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)

LUNGS (continued) pg 168 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 Middle Oblique fissure Horizontal fissure pg 168

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 Nerve plexus – Lymph Vessels pg 164

Lung Lobes Lobes are anatomically + functionally separate Lung lobes divided into Lobules Functionally separate Separated by dense CT Vary in size Stroma = lung tissue Areolar CT Many elastic fibers pg 178

Esophagus pg 212 Esophagus Layers of Esophagus (deep to superficial) 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 212

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 136

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 136

Thoracic Cavity Capacity is Increased by: Contraction of diaphragm Intercostal muscles elevate ribs Rib elevation causes the sternum to move anteriorly pg 135

Openings of Diaphragm PosteriorAnterior Aortic Hiatus Aorta Azygos vein Thoracic duct Esophageal Hiatus Esophagus Vagus nerves Caval Opening Inferior Vena Cava Right Phrenic Nerve pg 157

Vena Cava Superior Vena Cava Inferior 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

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 153

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 Contains lobes and lobules Capsule Cortex Medulla pg 206