1. Boundaries of and Structures Within
The Thoracic Cavity
Boundaries of and Structures Within

2. Body Cavities Dorsal body cavity Ventral body cavity Thoracic
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Dorsal body cavity
Ventral body cavity
Thoracic
2 Pleural
Mediastinum
Divided by Diaphragm
Abdominopelvic
Abdominal
Pelvic

3. 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

4. Pleural Cavities Surround the lungs
Pleural fluid secreted by pleural membranes
Holds layers together
Reduces friction of organs
Benefit of Compartmentalization
pg 159

5. 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

6. 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 238

7. Divisions 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

8. 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

9. Respiratory Tract Upper Respiratory Tract Lower Respiratory Tract
Superior to Larynx
Lower Respiratory Tract
Larynx
Trachea
Primary Bronchi
Secondary Bronchi
Rest of Bronchial Tree
Lungs
pg 992
pg 168

10. Trachea = windpipe Starts at Larynx and travels through mediastinum
Located Anterior to Esophagus
Trachea terminates into 2 primary bronchi entering lungs
Walls contain “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

11. Bronchial Tree Primary (main) Bronchi Secondary (lobar) 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

12. 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

13. 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

14. 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)

15. LUNGS (continued) pg 168 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
Middle
Oblique fissure
Horizontal fissure
pg 168

16. 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
Nerve plexus
– Lymph Vessels
pg 164

17. Lung 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

18. Esophagus pg 212 Esophagus Layers of Esophagus (deep to superficial)
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

19. 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

20. 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

21. Thoracic Cavity Capacity is Increased by:
Contraction of diaphragm
Intercostal muscles elevate ribs
Rib elevation causes the sternum to move anteriorly
pg 135

22. 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

23. Vena Cava Superior Vena Cava Inferior 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

24. 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

25. 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