The Thoracic Cavity

1
The Thoracic Cavity

• Boundaries of and Structures Within

2
Cavities
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• 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

• 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

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Pleural Cavities

• Surround the lungs
• Pleural fluid secreted by pleural membranes
• Holds layers together
• Reduces friction of organs
• Compartmentalization

pg 159
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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
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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 240
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Divisions of Mediastinum

• Superior (to heart)
• Contains thymus, cranial vena cava, trachea,
  esophagus
• Inferior
• Anterior (to heart)
• Contains thymus
• Posterior (to heart)
• Contains aorta, esophagus,
• trachea, bronchi,
• caudal vena cava
• Middle
• Contains heart pericardium

pg 177
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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
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Respiratory Tract

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

pg 992
pg 168
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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

Page 966
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Bronchial 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
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Bronchial Tree (continued)

• Bronchioles
• further divisions, lt 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

www.nlm.nih.gov/.../ency/imagepages/1103.htm
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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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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)

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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
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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
• Nerves
• Lymph Vessels

pg 164
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Lung Lobes

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

pg 178
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Esophagus

• 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
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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
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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

pg 136
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Thoracic Cavity Capacity is Increased by

• Contraction of diaphragm
• Intercostal muscles elevate ribs
• Rib elevation causes the sternum to move
  anteriorly

pg 135
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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
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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

• 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 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
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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

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Lymphatic SystemThe 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 Ducts

• Thoracic Duct
• Receives lymph from large trunks in abdomen and
  thorax
• Receives lymph from ducts of thoracic lymph nodes
• 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 154
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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