respiratory tract

lab practical

nasal cavity

1. Nasopharynx, oropharynx, laryngopharynx

   1. Stratified squamous epithelium

2. Cribriform plate of ethmoid bone

   1. Houses olfactory bulb

3. Nasal septum

4. Uvula

   1. Produces mucus and saliva to keep throat moist

5. Nasal conchae → superior, middle, inferior

   1. Warms and moisturizes air

6. Pharyngeal, palatine, and lingual tonsils

   1. Lymphatic nodules and tissue of the immune system

7. Eustachian tube connects middle ear to nasopharynx

8. Paranasal sinuses

   1. Four paired air-filled spaces that surround nasal cavity

   2. Named after the bones in which they are located

trachea structure

1. Larynx (voice box)

2. Epiglottis prevents aspiring food; made up of elastic cartilage

3. thyroid membrane and ligament connects hyoid bone to thyroid cartilage

4. thyroid cartilage is part of anterior part of larynx (hyaline cartilage)

5. cricoid cartilage (hyaline cartilage)

6. tracheal rings (hyaline cartilage)

7. primary, secondary, and tertiary bronchi

8. pseudostratified ciliated columnar epithelium secretes mucus → traps debris, preventing entry into lower respiratory tract

trachea histology

• Facing lumen → ciliated pseudostratified columnar epithelium

  • Goblet cells secrete mucus

• Lamina propria of the mucosa: contains areolar loose CT

• Anterior trachea → rings of hyaline cartilage

• Posterior trachea → smooth trachealis muscle

• Inferior to trachea: esophagus

lung tissue histology

muscles of inspiration

• Muscles of Inspiration: 

  • External intercostal muscles contract → elevates ribs and moves sternum out

  • Diaphragm moves down → increase space in thoracic cavity

muscles of expiration

• Muscles of Expiration: 

  • External intercostals relax → everything moves back in

  • Diaphragm moves up → decrease space in thoracic cavity

tidal volume (TV)

amount of air inhaled or exhaled with each breath under resting conditions

inspiratory reserve volume (IRV)

amount of air that can be forcefully inhaled after a normal tidal volume inhalation

• Purposefully taking a deep breath

expiratory reserve volume

amount of air that can be forcefully exhaled after a normal tidal volume exhalation

• Purposefully exhaling

vital capacity (VC)

maximum amount of air that can be exhaled after a maximal inspiration

vital capacity (VC) equation

• VC = TV + IRV + ERV

  • vital capacity = tidal volume + internal reserve volume + external reserve volume

boyle’s law

• Boyle's Law: P/KV

  • Intra-alveolar pressure is inversely proportional to volume if temperature remains constant (K)

end of expiration

alveolar pressure is equal to atmospheric pressure → no air movement

end of inspiration

alveolar pressure is equal to atmospheric pressure → no air movement

during inspiration

increased thoracic volume results in increased alveolar volume

• Results in decreased alveolar pressure

• Atmospheric pressure greater than alveolar pressure → air can move into the lungs

during expiration

decreased thoracic volume results in decreased alveolar volume

• Results in increased alveolar pressure

• Alveolar pressure greater than atmospheric pressure → air can move out of the lungs

alveolar walls

respiratory membrane layers

• Respiratory membrane is the point at which the capillaries meet the alveolar sacs

• Layers

  • Layer of liquid lining alveolus containing pulmonary surfactant → reduces surface tension

  • Alveolar epithelium composed of simple squamous

  • Basement membrane of epithelium

  • Thin interstitial space between basement membrane and capillary basement membrane

  • Basement membrane of the capillary endothelium

  • Capillary endothelium composed of simple squamous

what type of cells are suited for gas exchange

Simple squamous

what type of cells are suited for fluid exchange

simple cuboidal

type 1 pneumocytes

thin squamous epithelial cells

• Form 90% of surface of alveoli

type 2 pneumocytes

secretory cells

• Produces surfactant that minimizes surface tension at the alveolar air-liquid interface

• Optimizes mechanics of breathing

• Avoid alveolar collapse at the end of expiration

alveolar macrophage (dust cells)

protection against bacteria

• Primary phagocytes of innate immune system

chemical control of respiration

• In the brain stem, there is an area that controls respiration by responding to hydrogen ions

  • Problem: hydrogen ions cannot get through the blood brain barrier, but CO2 can

  • CO2 dissolves in cerebrospinal fluid (mainly water) → combines to form H2CO3

    • Immediately dissociates to form hydrogen and bicarbonate ions

  • Hydrogen ions sensed by the chemosensitive sensory area of the medulla → stimulate the inspiratory center to increase respiration

  • Bicarbonate ions will be broken down to release CO2 during expiration