Copyright © 2014 John Wiley & Sons, Inc. All rights reserved. CHAPTER 23 The Respiratory System

Copyright © 2014 John Wiley & Sons, Inc. All rights reserved.

CHAPTER 23The Respiratory System


Respiration is the exchange of gases between the atmosphere, blood, and cells

The combination of 3 processes is required for respiration to occur Ventilation (breathing) External (pulmonary) respiration Internal (tissue) respiration

The cardiovascular system assists the respiratory system by transporting gases

Breathing and Respiration


Structurally, the components of the respiratory system are divided into 2 parts:

1. Upper respiratory system

2. Lower respiratory system

Functionally, the components of the respiratory system are divided into 2 zones:

3. Conducting zone

4. Respiratory zone

Structures of the Respiratory System


Structures of the Respiratory System


The upper respiratory system consists of the nose, pharynx, and associated structures

The lower respiratory system consists of the larynx, trachea, bronchi, and lungs

Respiratory System Anatomy


Overview: Nose, Pharynx, Larynx, and Trachea


The external portion of the nose is made of cartilage and skin and is lined with mucous membrane

Cartilaginous Framework of the Nose


The bony framework of the nose is formed by the frontal, nasal, and maxillary bones

Internal Anatomy of the Nose


The nose is the only part of the respiratory system that is visible externally and is the route for air entry into the respiratory system.

Air is drawn in via the nostrils or external nares and enters the large nasal cavity, which is divided into two by the nasal septum.

The nasal cavity is partitioned from the oral cavity directly below it by the palate.

Nose

Like the rest of the respiratory tract, the nose is lined with mucosal epithelium (stratified squamous and pseudostratified ciliated columnar)

It also contains glands that secrete a thick, sticky mucus that helps to moisten the tract.

Just below the surface of the epithelium is a rich network of blood vessels that warm the nasal cavities.

Nosebleeds are fairly common because the blood vessels are so superficial.

Nose

Copyright © 2014 ohn Wiley & Sons, Inc. All rights reserved.


The nerve endings responsible for smell (olfaction) are found in the nasal mucosa at the back of the nasal cavities.

Any obstruction of the nasal passages and surrounding sinuses, for example caused by oedema of the tissues produced by the common cold, will affect these nerve endings.

Typically the symptoms of an upper respiratory tract infection, or ‘head cold’ involve the airways above the trachea.

Nose


Four cavities - the paranasal sinuses - surround and drain into the nasal cavity.

Their mucosal lining is continuous with that of the nose and this means that sinus infections (sinusitis) are common during a cold when the nasal mucosa is inflamed.

The hollow sinuses

• help lighten the skull

• act as a resonating chamber for sounds,

• help to produce mucus for the respiratory tract.

Paranasal sinuses


Nasal Conchae and Meatuses


Three shell-like structures, the conchae or turbinates, protrude into each side of the nasal cavity and increase the surface area over which air flows on its way to the lungs

As air is drawn in, the turbinates cause it to swirl around within the nasal cavity and this is useful in a number of ways:

- It allows extra time for the incoming air to be warmed and humidified,

- The swirling action forces the air into frequent contact with the nasal mucosa and large foreign particles become trapped;

- The eddy currents that are created then carry olfactory stimuli to the olfactory receptors in the nose, allowing us to smell.

- Warmed, humidified air passes from the nasal cavities through the internal nares into the pharynx, a structure shared by the respiratory and digestive systems.

Nasal Conchae


The pharynx functions as a passageway for air and food, provides a resonating chamber for speech sounds, and houses the tonsils, which participate in immunological reactions against foreign invaders

Pharynx


The mucosal epithelium (stratified squamous) in the oropharynx is thicker than elsewhere in the respiratory tract as it has to protect the tissues from any abrasive and chemical trauma caused by food.

Two eustachian or auditory tubes connect the middle ears with the nasopharynx and allow pressure in the middle and outer ear to equalise. The mucosal lining of the nasopharynx, eustachian tubes and middle ear is continuous and middle ear infections can occur when the nasopharynx is inflamed.

The oropharynx can be entered from the mouth as well as from the nasopharynx, while the lower portion, the laryngopharynx, divides into the oesophagus which carries food to the stomach and the larynx through which air passes to the lungs.

Pharynx


Masses of lymphoid tissue that act as a line of defense

Adenoids – single tonsil located posteriorly in the nasopharynx

Palatine tonsils – paired; located posteriorly in the orophayrnx

Lingual tonsils – pair of tonsils under the tongue

Tonsils


The larynx (voice box) is a passageway that connects the pharynx and trachea

Larynx


The larynx contains vocal folds, which produce sound when they vibrate. Pseusdostratified ciliated columnar epithelium

Larynx


The trachea extends from the larynx to the primary bronchi, 16 – 20 C- shaped rings of cartilage keep it open. Lined by pseusdostratified ciliated columnar epithelium

Trachea


At the superior border of the 5th thoracic vertebrae, the trachea branches into a right primary bronchus which enters the right lung and a left primary bronchus which enters the left lung

Bronchi


Upon entering the lungs, the primary bronchi further divide to form smaller and smaller diameter branches

The terminal bronchioles are the end of the conducting zone

Bronchi


The lungs are paired organs in the thoracic cavity

Lungs


The lungs are enclosed and protected by the pleural membrane

Lungs


Lobes and Fissures of the Lungs


When the conducting zone ends at the terminal bronchioles where the epithelium has changed gradually from psuedostratifed ciliated columnar epithelium to simple cuboidal epthelium.

The terminal brochioles end in the respiratory brochioles, which are lined by simple squamous epithelium, and the respiratory zone begins

The respiratory zone terminates at the alveoli, the “air sacs” found within the lungs

Alveoli


Alveoli are sac-like structures

Alveoli in a Lobule of a Lung


There are 2 kinds of alveolar cells, Type I and Type II

Alveolus


The respiratory membrane is composed of: 1. A layer of type I and type II alveolar cells and

associated alveolar macrophages that constitutes the alveolar wall

2. The capillary endothelium

Respiratory Membrane


Blood enters the lungs via the pulmonary arteries (pulmonary circulation) and the bronchial arteries (systemic circulation)

Blood exits the lungs via the pulmonary veins and the bronchial veins

Ventilation-perfusion coupling Vasoconstriction in response to hypoxia diverts

blood from poorly ventilated areas to well ventilated areas

Blood Supply to the Lungs


In pulmonary ventilation, air flows between the atmosphere and the alveoli of the lungs because of alternating pressure differences created by contraction and relaxation of respiratory muscles

Inhalation Exhalation

Pulmonary Ventilation


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Copyright © 2014 John Wiley & Sons, Inc. All rights reserved. CHAPTER 23 The Respiratory System