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