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The Thoracic CavityThe Thoracic Cavity

Boundaries of and Structures Within

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CavitiesCavities

• Dorsal body cavity• Ventral body cavity

– Abdominopelvic• Abdominal

• Pelvic

– Divided by Diaphragm

– Thoracic• 2 Pleural

• Mediastinum

Pg 614

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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

– Pericardial = surrounds heart, slightly modified

– Peritoneal = surrounds some abdominal organs

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Pleural CavitiesPleural 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 Pg 617

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MediastinumMediastinum

•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

Pg 614

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Respiratory TractRespiratory 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 = 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

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TracheaTrachea

Pg 589

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Bronchial TreeBronchial 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

Pg 591

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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 chamberPg 592

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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)

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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

– Gas exchange • Oxygen into blood

• Carbon Dioxide into alveoli

– Type II cells = cuboidal epithelial cells• Secrete fluid containing surfactant

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LUNGSLUNGS

• 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

Pg 595

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LUNGS (continued)LUNGS (continued)

• Left Lung = 2 lobes– Upper

– Lower

– Oblique Fissure

– Cardiac Notch

• Right Lung = 3 lobes – Upper

– Middle

– Lower

– Oblique fissure

– Horizontal fissure

Pg 599

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Specific Location of LungsSpecific Location of Lungs

• 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

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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– CT w/ numerous elastic fibers

Pg 599

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Other Contents of MediastinumOther 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 DiaphragmThe Diaphragm

• Skeletal Muscle• Dome-shaped (relaxed)• Flattens (contracts)• Divides thoracic &

abdominopelvic cavities• Attachments

– O: Inferior Internal rib cage

– I: Central tendon

• Innervated by right + left PHRENIC NervesPg 276

Superior View

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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

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Openings of DiaphragmOpenings of Diaphragm• PosteriorAnterior• 1 = Foramen for Aorta & Azygos Vein• 2 = Esophageal Hiatus for Esophagus and Vagus nerve• 3 = Foramen in Central Tendon for Inferior Vena Cava

1

2

3

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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

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Veins of MediastinumVeins 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

Pg 544

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The Lymphatic VesselsThe 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

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Lymphatic System…The Players: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

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Lymphatic DuctsLymphatic 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)

Pg 564

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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

tissuePg 570

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Location of Heart in ThoraxLocation 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 ThoraxLocation of Heart in Thorax

Pg 501

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The HeartThe Heart

• External Innervation– 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– lubricate heart while beating = reduces friction

Pg 502