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

Show effects of hypertension, Q. Show effects of Hypertension? Hyperten...

Q. Show effects of Hypertension? Hypertension can be damaging due to two effects: 1. Increased work load on the heart, and 2. Effect of hypertension on arteries The in

Explain the objectives of congenital heart disease, Explain the Objectives ...

Explain the Objectives of Congenital Heart Disease ? After reading this unit, you should be able to: 1 Comprehenced the epidemiologic significance of congenital heart disease (

Express krebs cycle photosystem ii, Calvin cycle electron transport chain g...

Calvin cycle electron transport chain glycolysis Kreb's cycle photosystem II.

Define the antigen-presenting cells of the immune system, Q. What are the a...

Q. What are the antigen-presenting cells of the immune system? The antigen-presenting cells of the immune system also known as APC cells are cells that do digestion and phagocy

Explain kingdom monera, Kingdom Monera The monerians are structurally t...

Kingdom Monera The monerians are structurally the simplest of all living things. They have apparently changed little since they first appeared on the earth. Their structure is

Explain dna replication, Q. As a result of the DNA replication two DNA mole...

Q. As a result of the DNA replication two DNA molecules come into existence. Why is it not correct to assert that the two "new" DNA molecules are created? What is the name given to

Define the osazone test or phenylhydrazine reaction, Define the Osazone Tes...

Define the Osazone Test or Phenylhydrazine Reaction? Compounds with -CO-CHOH group form crystalline osazones with phenyl hydrazine. These osazones have characteristic shapes an

Define factorial method to calculate nitrogen requirements, Define Factoria...

Define Factorial method to Calculate Nitrogen Requirements? The nitrogen requirements have been calculated by a factorial method suggested by different expert groups, described

What are the centrioles, Q. Into which periods is mitosis has divided? ...

Q. Into which periods is mitosis has divided? Mitosis is divided into four periods: metaphase, prophase, telophase and anaphase. Q. What are the centrioles and in which typ

What are the transposable elements, Transposable elements are able to move ...

Transposable elements are able to move around the genome by precise or imprecise excision events. What is meant by imprecise excision? A. Imprecise excision refers to a transpo

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