Analogy

• Respiratory system


  Biological system consisting of specific organs and structures used for gas exchange in humans
• Organs of Respiratory System

  • Nose and nasal cavity
  • Pharynx
  • Larynx
  • Trachea
  • Two bronchi
  • Bronchioles
  • Two Lungs
• Nose and nasal cavity


  • Main route of air entry
  • Two cavities divided by a septum
  • Anteriorly consist of hyaline cartilage
  • Roof formed by ethmoid bone
  • Floor formed by roof of the mouth
  • Medial wall formed by the septum
  • Lateral wall formed by the maxilla
• Respiratory functions of the nose

  • Warming
  • Filtering and cleaning
  • Humidification
• Pharynx


  Part of the throat that is behind the mouth and nasal cavity and above the esophagus and the larynx
• Pharynx


  • Length - 12-14cm (extends from the base of the skull to the level of 6th cervical vertebra)
  • Superiorly - Base of the skull
  • Inferiorly - Continuous with the esophagus
  • Anteriorly - Incomplete wall because of the nose, mouth and larynx opening
  • Posteriorly - Areolar tissue & first 6 vertebra
• Parts of the pharynx

  • Nasopharynx
  • Oropharynx
  • Laryngopharynx
• Nasopharynx


  • Nasal part of the pharynx lies behind the nose
• Oropharynx


  • Oral part of the pharynx lies behind the mouth
• Laryngopharynx


  • Laryngeal part of the pharynx extends from the oropharynx
• Layers of the pharynx

  • Mucous membrane lining
  • Fibrous tissue
  • Smooth muscle
• Blood supply of the pharynx

  • Facial artery
  • Facial vein
  • Internal jugular veins
• Nerve supply of the pharynx

  • Vagus nerve
  • Glossopharyngeal nerve
• Functions of the pharynx

  • Passageway for air and food
  • Warming and humidifying
  • Taste
  • Hearing
  • Protection
  • Speech
• Larynx


  • Extends from the root of the tongue
  • Lies in front of the laryngopharynx at the level of 3rd, 4th, 5th and 6th cervical vertebra
  • Until puberty there is little difference in size between sexes, then it grows larger in males
  • Superiorly - Hyoid bone & roof of the tongue
  • Inferiorly - Continuous with the trachea
  • Anteriorly - Muscles of the neck
  • Posteriorly - Laryngopharynx and 3rd to 6th cervical vertebra
• Main cartilages of the larynx

  • 1 thyroid cartilage
  • 1 cricoid cartilage
  • 2 arytenoid cartilages
  • 1 epiglottis
• Thyroid cartilage


  • Most prominent, consists of 2 flat pieces of hyaline cartilage fused anteriorly forming the Adam's apple
• Cricoid cartilage


  • Lies below the thyroid cartilage, composed of hyaline cartilage
• Arytenoid cartilages


  • Two roughly pyramid-shaped hyaline cartilages situated on top of the broad part of the cricoid cartilage
• Epiglottis


  • A leaf-shaped fibroelastic cartilage attached to the inner surface of the anterior wall of the thyroid cartilage
• Blood and nerve supply of the larynx

  • Superior and inferior laryngeal arteries
  • Thyroid veins
  • Superior laryngeal nerves
• Functions of the larynx

  • Production of sound
  • Speech
  • Protection of the lower respiratory tract
  • Passageway for air
  • Humidifying
  • Filtering
  • Warming
• Trachea

  • Continuation of the larynx, extends downwards to about the level of T-5 where it divides into right & left primary bronchi
  • Length - 10-11cm
• Trachea relations


  • Superiorly - the larynx
  • Inferiorly - the right & left bronchi
  • Anteriorly - upper part - the thyroid gland, lower part - the arch of aorta & the sternum
  • Posteriorly - the oesophagus
  • Laterally - the lungs
• Trachea structure


  • Fibrous & elastic tissue
  • Smooth muscle
  • Ciliated columnar epithelium
  • Held open by 16-20 incomplete cartilage rings (C-shaped)
• Trachea blood and nerve supply

  • Inferior thyroid artery
  • Bronchial artery
  • Inferior thyroid veins
  • Laryngeal nerve
• Trachea functions


  • Support and patency
  • Mucociliary escalator
  • Cough reflex
  • Warming
  • Humidifying
  • Filtering
• Right bronchus


  • Wider, shorter and more vertical than the left bronchus
  • Length - 2.5cm
  • Divides into 3 branches after entering the right lung, one to each lobe
• Left bronchus


  • Narrower than the right
  • Length - 5cm
  • Divides into 2 branches after entering the left lung, one to each lobe
• Bronchi and bronchioles structure

  • Composed of the same tissues as the trachea
  • Lined with ciliated columnar epithelium
  • Gradual change to non-ciliated cuboidal-shaped cells in the distal bronchioles
• Bronchi and bronchioles blood and nerve supply

  • Bronchial arteries
  • Bronchial veins
  • Vagus nerve
  • Lymph drainage - Thoracic duct
• Bronchi and bronchioles functions

  • Control of air entry
  • Warming & humidifying
  • Support & patency
  • Removal of particulate matter
  • Cough reflex
• Respiratory bronchioles and alveoli

  • Each lobule supplied with air by a terminal bronchiole
  • Terminal bronchioles further subdivide into respiratory bronchioles, alveolar ducts and alveoli
  • About 150 million alveoli in the adult lung
  • Gas exchange occurs in these structures
  • Walls become thinner as airways divide and become smaller
  • Distal respiratory passages supported by loose network of elastic connective tissue
• Respiratory bronchioles and alveoli functions

  • External respiration - exchange of gases by diffusion between the alveoli and the blood
  • Defence against microbes - protective cells within the lung tissue
  • Exchange of gases
• Lungs


  • Two lungs, one on each side
  • Shape - cone
  • Weight - 600-700g
  • Length - 20-24cm
  • Colour - pinkish
  • Right lung has 3 lobes, left lung has 2 lobes
  • Lobes separated by fissures
  • Area between the lungs is the mediastinum
• Lung surfaces


  • Apex
  • Base
  • Costal surface
  • Medial surface
• Pleura


  • Closed sac of serous membrane, one for each lung
  • Contains small amount of serous fluid
  • Consists of visceral pleura (adherent to the lung) and parietal pleura (adherent to the chest wall and diaphragm)
  • Pleural cavity between the two layers allows them to glide over each other during breathing
• Right lung


  • Divided into 3 lobes - upper, middle, lower
  • Separated by 2 fissures - oblique and horizontal
• Left lung


  • Divided into 2 lobes - upper and lower
  • Separated by the oblique fissure
  • Mediastinal surface has a large cardiac impression where the heart sits
• Lung blood supply


  • Bronchial arteries
  • Pulmonary capillaries