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The pharynx

The pharynx    (throat) is involved in both digestion and respiration. It receives food and air from the mouth, and air from the nasal cavities. When food enters the pharynx, involuntary muscle contractions close off the air passageways.

A short tube of skeletal muscle lined with a mucous membrane, the pharynx runs from the posterior oral and nasal cavities to the opening of the esophagus and larynx. It has three subdivisions. The most superior, the nasopharynx, is involved only in breathing and speech. The other two subdivisions, the oropharynx    and the laryngopharynx    , are used for both breathing and digestion. The oropharynx begins inferior to the nasopharynx and is continuous below with the laryngopharynx ( [link] ). The inferior border of the laryngopharynx connects to the esophagus, whereas the anterior portion connects to the larynx, allowing air to flow into the bronchial tree.

Pharynx

This diagram shows the cross-section of a human face and highlights the location of the pharynx, which runs from the nostrils to the esophagus and the larynx.
The pharynx runs from the nostrils to the esophagus and the larynx.

Histologically, the wall of the oropharynx is similar to that of the oral cavity. The mucosa includes a stratified squamous epithelium that is endowed with mucus-producing glands. During swallowing, the elevator skeletal muscles of the pharynx contract, raising and expanding the pharynx to receive the bolus of food. Once received, these muscles relax and the constrictor muscles of the pharynx contract, forcing the bolus into the esophagus and initiating peristalsis.

Usually during swallowing, the soft palate and uvula rise reflexively to close off the entrance to the nasopharynx. At the same time, the larynx is pulled superiorly and the cartilaginous epiglottis, its most superior structure, folds inferiorly, covering the glottis (the opening to the larynx); this process effectively blocks access to the trachea and bronchi. When the food “goes down the wrong way,” it goes into the trachea. When food enters the trachea, the reaction is to cough, which usually forces the food up and out of the trachea, and back into the pharynx.

The esophagus

The esophagus    is a muscular tube that connects the pharynx to the stomach. It is approximately 25.4 cm (10 in) in length, located posterior to the trachea, and remains in a collapsed form when not engaged in swallowing. As you can see in [link] , the esophagus runs a mainly straight route through the mediastinum of the thorax. To enter the abdomen, the esophagus penetrates the diaphragm through an opening called the esophageal hiatus.

Passage of food through the esophagus

The upper esophageal sphincter    , which is continuous with the inferior pharyngeal constrictor, controls the movement of food from the pharynx into the esophagus. The upper two-thirds of the esophagus consists of both smooth and skeletal muscle fibers, with the latter fading out in the bottom third of the esophagus. Rhythmic waves of peristalsis, which begin in the upper esophagus, propel the bolus of food toward the stomach. Meanwhile, secretions from the esophageal mucosa lubricate the esophagus and food. Food passes from the esophagus into the stomach at the lower esophageal sphincter    (also called the gastroesophageal or cardiac sphincter). Recall that sphincters are muscles that surround tubes and serve as valves, closing the tube when the sphincters contract and opening it when they relax. The lower esophageal sphincter relaxes to let food pass into the stomach, and then contracts to prevent stomach acids from backing up into the esophagus. Surrounding this sphincter is the muscular diaphragm, which helps close off the sphincter when no food is being swallowed. When the lower esophageal sphincter does not completely close, the stomach’s contents can reflux (that is, back up into the esophagus), causing heartburn or gastroesophageal reflux disease (GERD).

Questions & Answers

Muscle of mastication
JIMOH Reply
difference between seminiferous tubules and ejaculatory duct
Muhammad Reply
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Musibi
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Kity
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Agemo Reply
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Karan Reply
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sonugora Reply
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sonugora Reply
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Ambika Reply
life circle of RBC and the life circle of WBC.
Yemi Reply
RBC 120days
Zeph
RBC 120days and WBC 10-12days
sai
what is cardiac vascular system
Hari
what is anatomy?
Md Reply
what is manipulated
Ambika
anatomy is the branch of medical science which deal with the gross structure of body or organ
Ambika
note shoulder joint
jagadeesh
what is cardiovascular system
Hari
what is manipulated
Ambika
anatomical position
Ambika
?
Ambika
Scapula
sonugora
Study of internal structures
sonugora
the system of heart and vessels
Manar
what is collar Bone?
jagadeesh
positive feedback mechanism
Sirimala Reply
what is immunology
Riya Reply
immunology is a branch of medicine that study's the body immune system
SAMUEL
Immunology This is the study of specific and non-specific resistance of the body against infection i.e. the study of the immune response of a host to a foreign substance, which includes study of various reactions which are induced in the body by introduction of a substance.
Kaluki
what is role of elimination need like fluid and also stools
Munmun Reply
bone
Vijay
what is joint pain
Vijay
is the physical suffering caused by illness or injury of the joint
malulu
pls can someone describe shock,types ,pathophysiology and treatment
Isaac
this is what I'm thinking "After taking out everything the body needs, the bowel then expels the leftover waste."
isaiah
I think elimination also helps in the continuation of the digestive system because if the unwanted fluids and stools does not come out of the system it can create a problem in the digestive. system resulting in diseases.
Martha
shock is a condition whereby the circulating system is unable to get enough blood and oxygen to vital organs like the brain,heart,eye,kidney and others.
Martha
causing depression of those organs.
Martha
there are 2 classification of shock. primary shock: this occurs immediately after injury due emotional stimulus or pain.example hearing a bad news,sudden obstruction of airway.sudden heart attack. secondary shock :it occurs when primary shock is delayed
Martha
types of shock syncope (faint) oligaemic or hyppvovaemic shock. Anaphylactic shock. neurogenic/ physical shock septic sock catdiogenic shock.
Martha
What is the difference between dna duplication and chromosomes duplication?
to help you identify the human body parts to help you live a healthy life the study of Anatomy helps one to work in any health sector
sophia Reply
okay.
what is the function of the mitochondrial in the cell
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Source:  OpenStax, Anatomy & Physiology. OpenStax CNX. Feb 04, 2016 Download for free at http://legacy.cnx.org/content/col11496/1.8
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