Thoracic Cavity

The Thoracic Cavity Boundaries of and Structures Within

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Cavities • Dorsal body cavity • Ventral body cavity – Abdominopelvic • Abdominal • Pelvic

– Divided by Diaphragm – Thoracic • 2 Pleural • Mediastinum

Pg 614 www.smso.net

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 – Pericardial = surrounds heart, slightly modified – Peritoneal = surrounds some abdominal organs www.smso.net

Pleural Cavities • Pleural Cavities – – – –

Surround the lungs pleural fluid secreted by pleura holds layers together reduces friction of organs

• 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 www.smso.net

Pg 617

Mediastinum •DIVISIONS •Superior •Inferior •Anterior (ventral) •Posterior (dorsal) •Middle •BOUNDARIES •Lateral = parietal pleura of lungs •Anterior = ventral parietal pleura •Posterior = dorsal parietal pleura •Superior = dome of the neck •Inferior = diaphragmatic pleura www.smso.net

Pg 614

Respiratory Tract • Upper Respiratory Tract – Superior to Larynx

• Lower Respiratory Tract – – – – – –

Larynx Trachea Primary Bronchi Secondary Bronchi Rest of Bronchial Tree Lungs

Pg 583

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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

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Trachea

Pg 589 www.smso.net

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 www.smso.net

Pg 591

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 Pg 592

• Terminal bunches of Alveoli • Respiratory exchange chamber www.smso.net

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) www.smso.net

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 www.smso.net

LUNGS • Located in Pleural Compartments • Lateral to Mediastinum • Location – Apex posterior to clavicle – Base lays on Diaphragm – Costal Surface = Ant, Lat, Post surfaces contact ribs

• Hilus- medial indentation; structures enter each lung (root) – 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

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Pg 595

LUNGS (continued) • Left Lung = 2 lobes – – – –

Upper Lower Oblique Fissure Cardiac Notch

• Right Lung = 3 lobes Pg 599

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– – – – –

Upper Middle Lower Oblique fissure Horizontal fissure

Specific Location of Lungs • Right Lung – – – – –

• Left 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 www.smso.net

– 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

Lung Lobes • Lobes are anatomically + functionally separate • Lung lobes divided into Lobules – Functionally separate – Separated by dense CT – Vary in size

• Stroma = lung tissue www.smso.net – CT w/ numerous elastic fibers

Pg 599

Other Contents of Mediastinum •

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

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The Diaphragm • • • •

Skeletal Muscle Dome-shaped (relaxed) Flattens (contracts) Divides thoracic & abdominopelvic cavities • Attachments Superior View Pg 276

– O: Inferior Internal rib cage – I: Central tendon

• Innervated by right + left PHRENIC Nerves

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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 www.smso.net

Openings of Diaphragm • • • •

PosteriorAnterior 1 = Foramen for Aorta & Azygos Vein 2 = Esophageal Hiatus for Esophagus and Vagus nerve 3 = Foramen in Central Tendon for Inferior Vena Cava 3

1 2

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Vena Cava • Inferior Vena 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

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– 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 Mediastinum • Vena Cava • 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 www.smso.net

Pg 544

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 www.smso.net

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 www.smso.net

Lymphatic Ducts • Right Lymphatic Duct (variable) – Very short, empties into neck veins – Drains upper right quadrant

• Thoracic Duct – Drains 3/4 of body (all but top right quadrant) – 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) www.smso.net

Pg 564

Thymus Gland • • • •

Lymphatic Organ 2-lobed w/lobules Sits on heart and great vessels Immature lymphocytes mature into Tlymphocytes • Secretes Thymic Hormones: help Tlymphocytes gain immunocompetence • Decreases in size w/age • Functional tissue is replaced with fatty tissue Pg 570

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Location of Heart in Thorax • • • • • • •

Oblique Position Apex = Left of Midline (between ribs 5+6), Anterior to rest Base (posterior surface) sits on vertebral column Superior Right = 3rd Costal Cartilage joins Sternum Superior Left = 2nd Costal Cartilage joins Sternum Inferior Right = 6th Costal Cartilage Inferior Left = 5th Intercostal Space at Midclavicular line

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Location of Heart in Thorax

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Pg 501

The Heart • External Innervation

Pg 502 – Vagus (parasympathetic); C + T sympathetic chain ganglion

• Pericardium (3 layers) – 1) Outer-fibrous pericardium = dense CT – Serous pericardium • 2) parietal • 3) visceral (epicardium)

• Pericardial Cavity – between layers of serous pericardium – serous fluid www.smso.net – lubricate heart while beating = reduces friction