Structure of the Respiratory System

Yr11 ATAR Human Biology

Lungs

* Occupy chest cavity, except space taken up by heart
* The right lung has 3 lobes, left has 2
* **Pleura** is a membrane covering the inside of the lung and chest
* **Visceral pleura** covers the lungs
* **Parietal pleura** cover the chest
* **Pleural fluid** sits between the visceral and parietal pleurae and allows lungs to slide along when breathing while holding them against the inside of the chest wall

Larynx

Organ of voice

* Air passes through, going to and from the **lungs**
* Contains vocal cords that can vibrate to make the sound when air passes over
* Connects the pharynx to the trachea

Nose Cavity

As it passes over the mucous membrane, the air is filtered, warmed and moistened before it enters the **lungs**

* Contains projections that increase internal surface area.
* Contains smell receptors
* Acts as a resonating chamber for speech sounds
* Contain hair and mucus that trap dust

Pharynx

Joins mouth cavity to the **trachea** and oesophagus

* Air from the **nasal passage** passes through here
* Also called **throat**
* The region from the **nasal cavity** to the **larynx**

Trachnea

The tube that carries air to and from the **throat** to the **lungs**.

* also called the **windpipe**
* Made of C-shape cartilage rings that hold the structure open
* Has an epithelial lining that produces mucus to trap dust and debris
* lined with mucous membranes and cells with **cilia**.


* At the base, it splits into 2 branches, one per lung

Rib Cage

Form the framework of the chest

* During heavier breathing, movements become more important
* Are moved up and out by intercostal muscles during inspiration

Intercoastal Muscles

Muscles between **ribs**

* Move the **rib cage** upwards and outwards to increase the **lungs** and **chest cavity** volume when breathing in.

Diaphram

A muscle that separates the chest from the abdomen

* Contracts and flattens downwards thereby increasing the volume of the **chest cavity** when breathing in
* Mainly responsible for changes in chest volume during normal, quiet breathing

Avleoli

Tiny air sacs that make up most of the lungs.

* 1 cell thick
* Surrounded by a network of **capillaries**
* Where the gas exchange of O2 and CO2 between the air and blood occurs

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Bronchi

2 primary bronchi branch off the **trachea**, one per lung, they then divide into secondary and tertiary bronchi

* The primary bronchi take air into each lobe of the lung
* Bronchi have C-shape cartilage rings that hold the structure open, which get more spaced out as bronchi get smaller till they terminate
* Bronchi made of smooth muscle and elastin
* Has **cilia** and muscous

Bronchioles

Very fine tubes with walls of **smooth muscle**.

* Form when the tertiary bronchi divide
* Bronchioles continue to split into millions of terminal bronchioles which are before the alveoli
* Does not contain cartilage, but is made of smooth muscle and elastin that allow bronchioles to control airflow
* **Cilia** and mucus present

Epiglottis

A flap of tissue that, during swallowing, closes off the **trachea** so food and liquid cant enter the **lungs**.

* When inhaling, covers oesophagus
* When swallowing it covers the larynx

Cilia

Hair-like projection on the outside of a cell

* Beat rhythmically and move in a wave-like motion to move mucus and the particle trapped in the muscle upwards to the pharynx to be swallowed and digested