Human Anatomy Bony Thorax and Respiratory System

Bony Thorax

• Part of the skeletal system
• Provides protection for the organs involved in breathing and blood circulation
• Contains thoracic viscera: lungs and remaining thoracic organs housed in the mediastinum
• Components:
  • Sternum
  • 2 Clavicles
  • 2 Scapulae
  • 12 pairs of Ribs
  • 12 Thoracic Vertebrae

Landmarks

• Vertebra prominens (C7 spinous process): level of T1 body
• Jugular notch (Manubrial or Suprasternal notch): level of T2/T3
• Sternal Angle: level of T4/T5
• Xiphoid process (Ensiform): level of T9/T10

Respiratory System

• Purpose: gas exchange between air and blood
• 4 parts:
  • Pharynx
  • Trachea
  • Bronchi
  • Lungs
• Diaphragm: primary muscle of inspiration
  • Each half is called a hemidiaphragm

Upper Airway

• Hard Palate & Soft Palate: roof of oral cavity
  • Soft Palate: uvula, lower posterior portion
    • Boundary between nasopharynx & oropharynx
• Pharynx: passageway for food, fluid, & air
  • 3 divisions:
    • Nasopharynx: Houses the opening of the eustachian or auditory tube & pharyngeal tonsils
    • Oropharynx: Contains the palatine and lingual tonsils
    • Laryngopharynx: Extends from epiglottis & connects to esophagus
• Esophagus: posterior to larynx & trachea

Larynx (Voice Box)

• Cage-like, cartilaginous structure (1-1.5in)
• Organ of voice
• Suspended by Hyoid Bone
• Level of C3-C6
• Vocal Cords: Located within larynx; sounds are made as air passes between them
• Thyroid Cartilage:
  • Anterior wall of larynx
  • Level of C5
  • Anterior projection – palpated easily – Laryngeal Prominence (Adam's apple)
• Cricoid Cartilage:
  • Ring of cartilage that forms the inferior and posterior wall of the larynx
  • Attaches to trachea
• Epiglottis:
  • Resembles a leaf
  • Attaches to thyroid cartilage
  • Flips down and covers trachea during the act of swallowing

Trachea (windpipe)

• Connects larynx to bronchi tree
• Fibrous muscular tube
• 16-20 C-shaped rings of cartilage are embedded in the anterior wall: keeps airway open by preventing the trachea from collapsing during expiration
• Extends from (C6) to level of (T4/T5)
• Trachea divides: Carina @ T4/T5

Endocrine Glands

• Imaged with Respiratory System
• Thyroid Gland:
  • Located anteriorly just below thyroid cartilage
  • More radiosensitive than most body structures or organs
  • Stores and releases hormones to aid in metabolism: helps regulate growth and development in children; lowers calcium levels in the blood
• Parathyroid Glands:
  • Small round glands embedded in posterior surface of thyroid (2 on each side – 4 total)
  • Stores and secretes hormones that aid in specific blood function: increase calcium levels in the blood
• Thymus Gland
  • Disappears in adulthood
  • Inferior to thyroid gland & Anterior and superior to the heart
  • Large role in development of immune system
  • Thymic lymphocytes (T cells) – reject foreign material

Bronchial Tree – Primary Bronchi (Bronchus)

• Right and Left Primary Bronchi: AKA right and left main stem bronchi; split by carina
• Right Primary Bronchus: Wider, Shorter, and More Vertical than left; food particles or other foreign objects are more likely to enter and lodge in the right bronchus

Bronchial Tree – Secondary Bronchi

• Right Bronchus divides into 3 secondary bronchi
• Left Bronchus divides into 2 secondary bronchi

Mediastinum

• Structures:
  • Thymus gland
  • Heart & great vessels
  • Trachea
  • Esophagus
  • Coronary vessels
  • Azygos vein
  • Hemiazygos vein
  • Thoracic duct
  • Lymph nodes

Heart

• Heart and the roots of the great vessels are enclosed in a double-walled sac called the pericardial sac
• Located:
  • Posterior to the body of the sternum
  • Anterior to T5 to T8
  • Lies oblique in the mediastinum
  • 2/3 of the heart lies left of the median plane

Great Vessels (in the mediastinum)

• Inferior & superior vena cava
• Aorta: largest artery in the body
  • Ascending aorta: coming up out of the heart
  • Arch of the aorta: (3 arterial branches)
    • Brachiocephalic
    • Left common carotid
    • Left subclavian
  • Descending aorta: passes through diaphragm into abdomen (abdominal aorta)
• Large pulmonary arteries and veins: Return and supply blood to and from the lungs

Inferior Vena Cava

• Large vein that returns blood to the heart from the lower half of the body

Superior Vena Cava

• Large vein that returns blood to the heart from the upper half of the body

Coronary Vessels

• Coronary Arteries: Located around and inside the heart muscle
  • RCA (Right Coronary Artery): Supplies blood to right atrium and right ventricle; Branches supply the SA and AV nodes
  • LMCA (Left Main Coronary Artery): Supplies blood to left atrium and left ventricle; Branches supply 2/3 of the interventricular septum

Azygos & Hemiazygos Veins

• Azygos Vein:
  • Enters thorax through aortic hiatus
  • Enters superior vena cava at T4
• Hemiazygos Vein:
  • Arises from the left ascending lumbar vein
  • Joins the azygos vein at T9
• Posterior Intercostal veins join – this azygos system
• Azygos system is responsible for draining the thoracic wall and upper lumbar region

Blood Flow

• Vena Cava -> Right Atrium -> Tricuspid Valve -> Right Ventricle -> Pulmonary Valve -> Pulmonary Arteries -> Lungs -> Pulmonary Veins -> Left Atrium -> Bicuspid or Mitral Valve -> Left Ventricle -> Aortic Valve -> Aorta

3 Branches Off the Aortic Arch

• Brachiocephalic Artery
• Left Common Carotid Artery
• Left Subclavian Artery

Electrical Conductivity of the Heart

• Starts at SA node -> AV node -> Bundle of His -> Left and Right bundle branches -> Divide into the Purkinje fibers

Thoracic Duct

• Main lymphatic channel for the return of chyle to the venous system
• Chyle: made of lymph and fat droplets; Lymph: fluid carries fat and proteins to help fight germs & keep body fluid levels normal
• Enters thoracic cavity through aortic hiatus
• Located between the aorta and azygos vein, posterior to esophagus

Mediastinum Lymph Nodes

• Can become enlarged due to infections, cancer, and inflammatory diseases
• Clinical application: Enlarged lymph nodes can sometimes show up on chest x-rays and other imaging

Chest X-Ray

Quiz Me:

• Pleural Effusion: Fluid accumulation in the pleural space between the visceral and parietal pleura.
• Hemothorax: Blood accumulation in the pleural space between the visceral and parietal pleura.
• Pneumothorax: Air accumulation in the pleural space between the visceral and parietal pleura.
• Steps on how air gets from your nose through your lungs:
  • Nasal cavity -> Pharynx -> Trachea -> Bronchi -> Bronchioles -> Alveoli
• Which lung are you more likely to aspirate into?: Right lung, because the right bronchus is wider, shorter, and more vertical than the left, making it easier for foreign particles to lodge in.

Test your knowledge of the bony thorax and its role in the skeletal system, alongside the respiratory system's key components. This quiz covers important landmarks and structures essential for breathing and protecting thoracic organs. Challenge your understanding of human anatomy and its components related to airflow and organ positioning.