Thoracic Cavity lecture presentation

The Thoracic Cavity

Boundaries of and Structures Within

 Body Cavities

• Dorsal body cavity
• Ventral body cavity
• Thoracic
• 2 Pleural
• Mediastinum
• Divided by Diaphragm
• Abdominopelvic
• Abdominal
• Pelvic

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 Cavities

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

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

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
• 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
• Boundaries of Mediastinum
• Lateral
• parietal pleura of lungs
• Anterior
• ventral parietal pleura
• Posterior
• dorsal parietal pleura
• Superior
• dome of the neck
• Inferior
• diaphragmatic pleura

Respiratory Tract

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

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

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

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

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 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)

• 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

LUNGS

• Hilus- medial indentation
• Root of Lung = structures enter each lung
• 2 Pulmonary Veins = carries O 2-rich blood from each lung to heart
• 1 Pulmonary Artery = carries O 2-poor blood to each lung
• Primary Bronchus
• Nerve plexus

Lymph Vessels

• 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

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

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

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 àlow 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

Thoracic Cavity Capacity is Increased by:

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

Openings of Diaphragm

• Posterior àAnterior
• Aortic Hiatus
• Aorta
• Azygos vein
• Thoracic duct
• Esophageal Hiatus
• Esophagus
• Vagus nerves
• Caval Opening
• Inferior Vena Cava
• Right Phrenic Nerve

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

Veins of Thoracic Cavity

• Vena Cavae
• Azygos Vein
• “unpaired”
• right side of vertebral bodies (at level of T 12)
• runs superiorly
• empties into Sup. Vena Cava
• drains right posterior intercostal veins
• Connects to hemiazygos and accessory hemiazygos that drain left side

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

  download lecture presentation Thoracic Cavity
source by  faculty.ccri.edu