lecture presentation #4
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The Thoracic CavityThe Thoracic Cavity
Boundaries of and Structures Within
Body CavitiesBody Cavities
• Dorsal body cavity• Ventral body cavity
– Thoracic• 2 Pleural
• Mediastinum
– Divided by Diaphragm
– Abdominopelvic• Abdominal
• Pelvic
www.newworldencyclopedia.org/entry/Body_cavity
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Serous membrane = Serosa 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 CavitiesPleural Cavities
• Surround the lungs• Pleural fluid secreted by pleural
membranes– Holds layers together
– Reduces friction of organs
• Benefit of Compartmentalization
pg 159
Pleural CavitiesPleural 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 AbnormalitiesPleural 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 MediastinumDivisions 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 MediastinumBoundaries 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 TractRespiratory Tract
• Upper Respiratory Tract– Superior to Larynx
• Lower Respiratory Tract– Larynx
– Trachea
– Primary Bronchi
– Secondary Bronchi
– Rest of Bronchial Tree
– Lungspg 168
pg 992
Trachea = windpipeTrachea = 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 TreeBronchial Tree
• Primary (main) 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)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)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 TreeThroughout 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)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 168
LUNGSLUNGS
• 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 LobesLung 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
EsophagusEsophagus• 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 212
The DiaphragmThe 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 Nervespg 136
Action of the DiaphragmAction 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 (highlow 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: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 DiaphragmOpenings of Diaphragm
• PosteriorAnterior• Aortic Hiatus
– Aorta– Azygos vein– Thoracic duct
• Esophageal Hiatus – Esophagus– Vagus nerves
• Caval Opening– Inferior Vena Cava– Right Phrenic Nerve pg 157
Vena CavaVena Cava
• 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
Veins of Thoracic CavityVeins 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 GlandThymus 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
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