Biomedical Science - Anatomy of the Respiratory System

main functions of the respiratory system

-allows continuous supply of oxygen to cells so they can carry out normal functions

-remove waste gas CO2

-provides sense of smell

-protects airways from harmful substances and pathogens

-produces sound

Upper respiratory tract includes

nasal cavity, pharynx, larynx

Nasal cavity

-nasal septum

-vestibule area (nostril) - stratified squamous epithelium, coarse hairs to trap particles

-rich blood supply under the surface warms the air on entering

-above vestibule - ciliated pseudostratified epithelial cells (respiratory epithelium) and goblet cells (secrete mucous) which are an immune barrier and humidify the air

-forms sound by acting as a resonance chamber to amplify the sound, some consonants are formed in the nasal cavity eg. m and n

paranasal sinuses

-air filled cavities in the skull and the bones around the nose lined with columnar pseudostratified ciliated epithelium and goblet cells:

frontal sinus, ethmoid sinus, maxillary sinus, sphenoid sinus

-source of moisture if nasal cavity becomes dry

-play a significant role in resonance, which is important for the quality and tone of the voice

-normal air flow is disrupted when sinuses get blocked eg. you have a cold, and this modifies sound

pharynx

-muscular tube

-lined with ciliated pseudostratified columnar epithelium with goblet cells (Also mucous glands)

-comprised of 3 parts (superior to inferior): nasopharynx, oropharynx, laryngopharynx

Sound: the pharynx directs air flow by changing the shape of the vocal tract, this influences the sounds made by the larynx

larynx

-connects pharynx with trachea

-lined with ciliated psuedostratified columnar epithelium, reinforced by cartilage

-contains the epiglottis which shuts off the larynx during swallowing

-contains the vocal folds (covered by stratified squamous epithelium)

generates sound for speech

air causes vocal folds to vibrate which creates sound waves

close during swallowing - an additional barrier against food/liquid entering the trachea

cells lining respiratory tract

lined with epithelial cells which form an immune barrier, secrete mucus and protect the tissues from the environment, is called the respiratory epithelium and is found throughout the respiratory tract

specialised cells

-the nasal cavity, trachea and bronchi are lined with ciliated epithelial cells

-these cells have hair like projections which beat in the coordinated way to remove debris and infectious particles from the lung

-the vocal chords are lined with stratified squamous epithelium, form strong layers of cells which protect the vocal cords from mechanical stress and friction

lungs

-where gaseous exchange takes place

-right lung has 3 lobes: superior, middle, inferior

-left lung only 2 lobes: superior and inferior

-cardiac notch allows space for the heart in the mediastinal cavity

-the bronchi and pulmonary arteries enter and pulmonary veins exit the lung at the hilum (on inner lung surface)

pleura

is a double-layered membrane surrounding each lung creating a cavity which is filled with pleural fluid

Visceral pleura

Inner layer attached directly to the lung surface - covers the lungs

Parietal pluera

Outer layer attached to the chest wall and diaphragm

Function of the Pleura

Lubrication: minimizes friction between the lung and chest wall during respiration

Surface tension: Helps maintain lung inflation by keeping the two pleural layers adhered together

Protection: Acts as a barrier to separate the lungs from

Pressure regulation: Maintains a negative pressure environment essential for lung expansion

Trachea

Flexible tube, 10 cm long, 1.5 - 2 cm wide

Lined by respiratory epithelium, interspersed by goblet cells (which secrete mucus)

Made of a stack of 16-20 incomplete rings (C- shape) of hyaline cartilage - open part faces posteriorly, to permit expansion of oesophagus during swallowing

The trachea ends at the carina bifurication, where it divides into R and L bronchi

Bronchi

contain cartilage and layer of smooth muscle, lined by respiratory epithelium and goblet cells

Bronchioles

have smooth muscle but less cartilage, rely on elastic tissue for support

epithelium becomes simple ciliated columnar, few mucous glands

goblet cells are replaced by Clara/club cells which produce a less viscous secretion

Terminal bronchioles

Smallest bronchioles

End of conducting zone

Ciliated simple cuboidal epithelium

Smooth muscle still present

Fewer goblet cells, more Clara cells

Respiratory bronchioles

First part of the respiratory zone

Simple cuboidal epithelium

Immune cells

Contain small outpouchings called alveoli

where oxygen and carbon dioxide are

exchanged between the air and the blood

Alveoli

walls are simple epithelium (type 1 and type 2 pneumocytes)

One cell thin - allows efficient gas exchange by diffusion

150 million alveoli per lung - huge surface area for diffusion

Extensive network of blood capillaries covers each alveoli to allow diffusion across a wide area of the lungs

external respiration

the exchange of oxygen and carbon dioxide between the lungs and air/environment

internal respiration

the exchange of oxygen and carbon dioxide between the blood and tissues at the cellular level

equation for cellular respiration

glucose + oxygen --> carbon dioxide + water + ATP