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By the end of this section, you will be able to:
  • List the structures that make up the respiratory system
  • Describe how the respiratory system processes oxygen and CO 2
  • Compare and contrast the functions of upper respiratory tract with the lower respiratory tract

The major organs of the respiratory system function primarily to provide oxygen to body tissues for cellular respiration, remove the waste product carbon dioxide, and help to maintain acid-base balance. Portions of the respiratory system are also used for non-vital functions, such as sensing odors, speech production, and coughing ( [link] ).

Major respiratory structures

This figure shows the upper half of the human body. The major organs in the respiratory system are labeled.
The major respiratory structures span the nasal cavity to the diaphragm.

The nose and its adjacent structures

The major entrance and exit for the respiratory system is through the nose, via the nostrils. The inhaled air enters into the nasal cavity, which is separated into left and right sections by the nasal septum. The wall of the nasal cavity has three bony projections, called the superior, middle, and inferior nasal conchae. Conchae serve to increase the surface area of the nasal cavity and to disrupt the flow of air as it enters the nose, causing air to bounce along the epithelium, where it is filtered, warmed, and humidified. Air exits the nasal cavities and moves into the pharynx.

Several bones that help form the walls of the nasal cavity have air-containing spaces called the sinuses, which serve to warm and humidify incoming air. Sinuses are lined with a mucosa. Each sinus is named for its associated bone: frontal sinus, maxillary sinus, sphenoidal sinus, and ethmoidal sinus. The sinuses produce mucus and lighten the weight of the skull.

Portions of the nasal cavities are lined with mucous membranes, containing sebaceous glands and hair follicles that serve to prevent the passage of large debris, such as dirt, through the nasal cavity.

The conchae and sinuses are lined by respiratory epithelium    composed of pseudostratified ciliated columnar epithelium ( [link] ). The epithelium contains goblet cells, one of the specialized, columnar epithelial cells that produce mucus to trap debris. The cilia of the respiratory epithelium help remove the mucus and debris from the nasal cavity with a constant beating motion, sweeping materials towards the throat to be swallowed. Interestingly, cold air slows the movement of the cilia, resulting in accumulation of mucus that may in turn lead to a runny nose during cold weather. This moist epithelium functions to warm and humidify incoming air. Capillaries located just beneath the nasal epithelium warm the incoming air.

Pseudostratified ciliated columnar epithelium

This figure shows a micrograph of pseudostratified epithelium.
Respiratory epithelium is pseudostratified ciliated columnar epithelium. Seromucous glands provide lubricating mucus. LM × 680. (Micrograph provided by the Regents of University of Michigan Medical School © 2012)

Pharynx

The pharynx    is a tube formed by skeletal muscle and lined by mucous membrane that is continuous with that of the nasal cavities. The pharynx is divided into three major regions: the nasopharynx, the oropharynx, and the laryngopharynx ( [link] ).

Questions & Answers

Definition of respiration
Muhsin Reply
where does digestion begins
Achiri Reply
in the mouth
EZEKIEL
what are the functions of follicle stimulating harmones?
Rashima Reply
stimulates the follicle to release the mature ovum into the oviduct
Davonte
what are the functions of Endocrine and pituitary gland
Chinaza
what's biology?
Egbodo Reply
Biology is the study of living organisms, divided into many specialized field that cover their morphology, physiology,anatomy, behaviour,origin and distribution.
Lisah
biology is the study of life.
Alfreda
1-chemical level 2-cellular level 3-organ system level 4-tissue level 5-organism level 6-molecules
Dennis Reply
when cell are dead in any part of the body what happen to that place
Dennis Reply
describe the Krebs cycle
Lian Reply
the sequence of reactions by which most living cells generate energy during the process of aerobic respiration. It takes place in the mitochondria, consuming oxygen, producing carbon dioxide and water as waste products, and converting ADP to energy
shea
thanks
Lian
Andy is 1.0 m tall and weighs 45kg Bmi= weight / Height (squared) what's his bmi? Is it high or low?
zafirah Reply
where did our atmosphere came from
Thomas Reply
Our atmospher came from outer space.
R0se
Do mitotic and mitosis mean same?
Abhishek Reply
yes
momo
what are some mechanisms for regulating electrolytes and fluid in the body?
Anita
how do it move
Jaheim Reply
what is biology fall under
Twayne Reply
what is life?
Suliman Reply
define unit membran model?
Suliman
define unit membran model?
Suliman
different between human being and animals
Habeeb Reply
what is fat soluble drugs
Acho Reply
drugs that dissolve mostly in fatty tissues
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Source:  OpenStax, Human biology. OpenStax CNX. Dec 01, 2015 Download for free at http://legacy.cnx.org/content/col11903/1.3
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