Respiratory system

Structure and Functions of the Respiratory System

By the end of this session students are expected to be able to:

• Define the Respiratory System
• Explain the Structure and Function of the Upper Respiratory Tract

Explain the Structure and Function of the Lower Respiratory Tract

What is respiratory system?

Definition of Respiratory System

The respiratory tract is the part of the anatomy that is responsible with the process of respiration in human body

Primarily, oxygen is absorbed from the atmosphere into the body and carbon dioxide is expelled from the body The respiratory system may be divided into the upper respiratory tract and the lower respiratory tract.

What are the structures and functions of upper respiratory system?

Structure and Functions of the Upper Respiratory System

Respiratory system

The organs of the upper respiratory system are located outside of the thorax and consists of the nose, pharynx and larynx

Nose

Is made up of bone and cartilage covered with skin, and lined with hairs within the nostrils. The hairs help to block dusts entry The two nasal cavities are within the skull, separated by the nasal septum, which is a bony plate made of the ethmoid bone and vomer The nasal mucosa is ciliated epithelium with goblet cells which produce mucus The mucus produced help to trap bacteria and particles from the air There are three shelve like bones called conchae project from the lateral wall of each nasal cavity In the upper nasal cavities are the olfactory receptors, which detect vaporized chemicals that have been inhaled

Paranasal sinuses:

Are air cavities in the maxillae, frontal, sphenoid, and ethmoid bones Are lined with ciliated epithelium, and the mucus produced drains into the nasal cavities.

The functions of the paranasal sinuses are to lighten the skull and provide more vibrating air for the voice.

Paranasal sinuses

Functions of the nose

• Respiration (breathing)

The nose humidify, warm, filter and clean the air Reception and elimination of secretions from the nasal mucosa, paranasal sinuses, and nasolacrimal ducts Olfaction (smelling) – is the organ of sense of smell It aids speech- this is enhanced by the presence of paranasal sinuses

Pharynx

It is a muscular tube posterior to the nasal and oral cavities and anterior to the cervical vertebrae.

• It is divided into nasopharynx, oropharynx and laryngopharynx.

Nasopharynx lies behind the nasal cavity.

 It is continuous with lining of the nose and consists of ciliated columnar epithelium and the intermediate layer is fibrous tissue.

Oropharynx lies behind the oral cavity.

 It is lined with stratified squamous epithelium which is continuous with lining of the mouth and oesophagus.

Laryngopharynx also known as the hypopharynx, this is also lined with moist stratified squamous epithelium.

Functions of the pharynx

• Passageway for air and food
• Warming and humidifying air
• Protection
• Taste
• Facilitates Hearing (through eustachian tube)

The pharynx is also important in vocalization and Speech

Larynx

The larynx houses the vocal folds, and is situated just below the pharynx between the root of the tongue and upper end of the trachea.

The larynx consists of cartilages attaches to each other by ligaments and membranes.

The framework of the larynx is formed by nine cartilages (e.g. thyroid, epiglottis) connected to one another by muscles, ligaments and membranes.

The epiglottisis the uppermost cartilage. During swallowing, the larynx is elevated, and the epiglottis closes over the top to prevent entry of saliva and food to the larynx

Functions of the larynx

• Speaking (speech)
•  Sound production is primarily done by the focal folds
• Respiration (is the air passageway between pharynx and the trachea)

Swallowing

 The epiglottis and vestibular folds prevent swallowed material from moving into the larynx

What are the structures and functions of lower respiratory system?

Structure and Functions of the Lower Respiratory System

Respiratory system

The organs of the lower respiratory system are located inside of the thorax and consists of the trachea, bronchial tree and lungs Trachea

The trachea is about 4 to 5 inches ( about 15cm) long and extends from the larynx to the primary bronchi.

The wall of the trachea contains 16 to 20 C-shaped pieces of cartilage, which keep the trachea open.

The gaps in these incomplete cartilage rings are posterior, to permit the expansion of the oesophagus when food is swallowed.

The mucosa of the trachea is ciliated epithelium with goblet cells.

. The differences btw left and right lungs

• The differences btw left and right lungs are:

1.Right lung has 3 lobes where as left lung has 2 loves 2.Right lung has two fissures (horizota&oblique fissures) where as left lung has only one oblique fissure

• Left lung has cardiac notch where as Right lung do not have

Bronchial Tree

Are the branches of trachea that enters the lungs (primary/principal bronchi) Their structures are like those of trachea, with C-shaped cartilages and ciliated epithelium Within the lungs, the primary bronchus branches to secondary bronchi that forms lobes of each lungs (three in right lung, two in the left lung) The further branching of the bronchial tube is called bronchial tree The smallest branches are called bronchioles( made of elastic and are clinically important in asthma Bronchioles have no cartilages and the smallest ones terminate in clusters of alveoli, the air sacs of the lungs.

Lungs and pleural membranes

Lungs are conical in shape and are located on either side of the heart in the chest cavity and are encircled and protected by the rib cage The base of each lung rests on the diaphragm below; the apex (superior tip) is at the level of the clavicle.

On the medial surface of each lung there is an indentation called the hilus, where the primary bronchus and the pulmonary artery and veins enter the lung.

The pleural membranes are the serous membranes of the thoracic cavity.

The parietal pleura line the chest wall, and the visceral pleura are on the surface of the lungs (adhere to lung).

Between the pleural membranes is serous fluid, which prevents friction and keeps the two membranes together during breathing.

Respiratory system

The lung root is a collection of structures that suspends the lung from the mediastinum. Each root contains a bronchus, pulmonary artery, two pulmonary veins, bronchial vessels, pulmonary plexus of nerves and lymphatic vessels.

All these structures enter or leave the lung via the hilum – a wedge shaped area on its mediastinal surface.

Root and Hilum

hilus

Respiratory system

Apex – The blunt superior end of the lung. It projects upwards, above the level of the 1st rib and into the floor of the neck.

• Base – The inferior surface of the lung, which sits on the diaphragm.

Lobes (two or three) – These are separated by fissures within the lung.

Surfaces (three) – These correspond to the area of the thorax that they face. They are named costal, mediastinal and diaphragmatic.

Borders (three) – The edges of the lungs, named the anterior, inferior and posterior borders.

Alveoli

• Are the air sacs of the lungs

Is where there is oxygen carbon dioxide exchange In the spaces between clusters of alveoli is elastic connective tissue, which is important for exhalation.

Within the alveoli are macrophages that phagocytose pathogens or other foreign material that may not have been swept out by the ciliated epithelium of the bronchial tree

Respiratory system is responsible with exchange of gases (oxygen and carbon dioxide) in human body

• Respiratory system is lined with mucus and cilia for trapping microorganisms and dusts
• Alveoli are functional units of lungs where exchange of gases takes place

Key Points

What are the functions of respiratory system?

• What is the main function of the alveoli?
• What are the functions of upper respiratory system?
• What are the structures of lower respiratory system?

Evaluation