Pharynx and larynx, Biology

Assignment Help:

Pharynx:

Pharynx  is a funnel shaped tube about  13cm long that  starts at the internal nares and  extends to the  level of the cricoid cartilage. It  lies posterior  to the nasal  and oral cavities, superior to  larynx and just anterior to the cervical vertebrae.  Its walls are composed of skeletal muscles and  lined by mucous membrane. Three parts of pharynx are nasopharynx, oropharynx and  laryngopharynx. The nasopharynx  is posterior  to nasal cavity. The two  internal nares,  to  eustachian tubes and  the oropharynx are the openings of nasopharynx. Oropharynx  lies posterior  to oral cavity, extends from the  soft palate inferiorly to  the  level of hyoid bone, lined with non-keratinized stratified squamous epithelium. Two pairs of  tonsil are found  in oropharynx. Laryngopharyx begins at  the  layer of hyoid bone,  lined by  non-keratinized stratified squamous epithelium, opens into oesophagus posteriorly and the larynx anteriorly. Pharynx  serves as a passage way  for air,  food and drink, and provides resonating chamber for speech sounds. 

Larynx:

Larynx or voice box  is a short passage way that connects the  laryngopharynx with trachea. It lies in the midline of the neck anterior to oesophagus and corresponds with the levels of cervical 4 to 6 vertebrae. Its wall is  composed of nine pieces of cartilage-3 single-thyroid, epiglottis and cricoid and 3  in pairs- arytenoid, cuneiform and  comiculate cartilages. Arytenoid  influencerhe positions and tensions of vocal  folds. Thyroid cartilage, two  fused plates of hyaline cartilage to  form the  anterior wall of the  larynx giving a triangular shape. Epiglottis  is  large, leaf shaped having a stem which  is attached to  the anterior rim of  the  thyroid cartilage and hyoid bone and  a broad superior  'leaf' portion unattached and  free to move up and down. During swallowing epiglottis moves down and  forms a  lid over glottis closing the entrance to larynx to prevent the entry of food or drink. When small particles of food, drink or dust enter the larynx a cough reflex occurs to expel the material. 

Arytenoid cartilages are two  small structures situated on the upper surface of  the expanded signet portion of the cricoids cartilage. They give attachment  to the posterior  ends of the true vocal  cords. The true vocal cords are fibro elastic bands extending from the posterior aspects of the thyroid cartilage in front to the arytenoids cartilage behind. The false vocal cords are two loose folds of mucous membrane situated above the  true cords. Larynx is lined by mucous membrane which, except over the vocal cords,  is covered with ciliated columnar epithelium.  


Related Discussions:- Pharynx and larynx

Name of the terminal portion of the axon, Q. What is the name of the termin...

Q. What is the name of the terminal portion of the axon? The terminal portion of the axon is called as presynaptic membrane Through, this membrane neurotransmitters are release

Explain national nutritional anaemia prophylaxis programme, Explain Nationa...

Explain National Nutritional Anaemia Prophylaxis Programme? National Nutritional Anaemia Prophylaxis Programme addresses iron and folate deficiency anaemia (IDA). Preschoolers

St. jude medical valve--types of valves, St. Jude Medical Valve (SJM) :  ...

St. Jude Medical Valve (SJM) :  This is a low profile bi-leaflet valve, which was introduced in 1977. The leaflets and the housing are made of pyrolitic carbon. The currently

Define advantages and disadvantages of swab method, Define Advantages and D...

Define Advantages and Disadvantages of Swab Method? Advantages of Swab Method 1. Suitable for flexible, uneven and heavily contaminated surfaces. 2. Rapid, simple and ine

Initial and the final energy levels in catalyzed reactions, Q. Is there a d...

Q. Is there a difference between the initial and the final energy levels in non-catalyzed and catalyzed reactions? The catalysis does not modify the energetic state of reagents

Gonial apospory and somatic apospory, Gonial Apospory and Somatic Apospory ...

Gonial Apospory and Somatic Apospory Gonial Apospory There is no meiosis. The megaspore mother cell enlarges; a small vacuole appears above and below the nucleus. The c

Intra cranial mycotic aneurysms, The reported occurrence of ICMAs is 1.2 pe...

The reported occurrence of ICMAs is 1.2 per cent to 5 per cent of cases. Streptococci and S.aureus account for 50 per cent and 10 per cent of cases, respectively, and are seen with

What is low - density lipoprotein receptor pathway, Q. What is low - densit...

Q. What is low - density lipoprotein receptor pathway? Ans. The increasing cellular free cholesterol generated regulates the activities of two enzymes that are of crucial

Explain cholera, Cholera  The risk of infection with cholera is very lo...

Cholera  The risk of infection with cholera is very low in tourists. The parenteral vaccine licensed in the US is no longer available. One oral vaccine called Dukoral is availa

Write Your Message!

Captcha
Free Assignment Quote

Assured A++ Grade

Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!

All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd