Respiratory Anatomy

Nasopharynx

pseudostratified epithelium, secretes mucous, tonsils screen for pathogens. (top of pharynx)

Oropharynx

middle pharynx; food and air meet, need stratified squamous epithelium for protection. more tonsils.

Laryngopharynx

lower pharynx; still stratified squamous. food and air split; food goes down esophagus

Larynx

provides protection with thick casing of hyaline cartilage; epiglottis opens during breathing to allow air through glottis; closes during swallowing. vocal folds vibrate in response to air movement and regulate pitch during speech

Trachea

series of pipes leads air to alveoli. pseudostratified epithelia with cilia; goblet cells to secrete mucous. C shaped rings of hyaline cartilage provide support and flexibility; expanding during inhalation and swallowing.

Bronchi

require cartilage for support, turn into bronchioles when cartilage is gone. terminal bronchioles lead into alveoli; simple squamous epithelium surrounded by pulmonary capillaries that increase surface area for maximum gas exchange.

alveoli

epithelial layer made mostly of simple squamous (type I pneumocytes with some type II cuboidal pneumocytes). macrophages live along epithelium to screen for pathogens. bronchioles split into alveolar ducts. branches of pulmonary artieries split into capillaries.

Diaphragm

dome shaped muscle that divides thoracic and abdominal cavities. contracts on inhale, relaxes on exhale. when contracting, dome caves in creating a vacuum that pulls lungs down with it, increasing lung volume.

inhaling or exhaling?

total atm pressure > total pressure in lungs = inhale

total atm pressure < total pressure in lungs = exhale

breathing faster or slower?

low O2 + low pH + high CO2 = faster

high O2 + high pH + low CO2 = slower

why is it better to be hypoxic than hypercapnic?

being hypercapnic makes pH too high and irreversibly denatures proteins, even if only too acidic for seconds. CO2 functions as carbonic acid and lowers pH

breathing mechanics

diaphragm contracts to increase thoracic volume → lungs expand → increase in volume produces decreased pressure in lungs → creates negative pressure gradient with atmosphere → air flows into lungs

breathing rate

controlled by brain regions in the pons and medulla

compliance

ability to stretch

Pressure

2 T (tension) / R (radius)

Surfactant

secreted by type II pneumocytes to break water surface tension and increase compliance of alveoli. wigthout surfactant, contortion and compression would greatly impact pressure within alveoli and risk collapse. If an alveola starts getting smaller/squeezed on and pressurized, surfactant gets more concentrated, lowers tension and lowers pressure to prevent collapse.

Partial pressure

pressure of individual gases that makes up total atmospheric pressure; in alveoli creates pressure gradient from low oxygen blood to alveoli, allowing gas to escape and reoxiginate blood