You are a helpful, respectful, and honest assistant. Always answer as helpfully as possible, while being safe. Your answers should not include any harmful, unethical, racist, sexist, toxic, dangerous, or illegal content. Please ensure that your responses are socially unbiased and positive in nature. If a question does not make any sense or is not factually coherent, explain why instead of answering something not correct. If you don't know the answer to a question, please don't share false information.
What is Which of the following develops from the third pharyngeal pouch? and explain in detail?
Ans. b (Inferior parathyroids). (Ref. Human Embryology by JB singh, 7th ed., p 112)Branchial (Pharyngeal) pouch derivatives include:First pouch derivatives--middle ear cavity, Eustachian tube, mastoid air cells.Second pouch derivatives--epithelial lining of palatine tonsil.Third pouch (dorsal wings)--inferior parathyroidsThird pouch (ventral wings)--thymusFourth pouch derivatives--superior parathyroids.Also remember:Branchial/ pharyngeal apparatus: Consist of1. Branchial clefts (derived from ectoderm)2. Branchial arches (derived from mesoderm and neural crests)3. Branchial pouches (derived from endoderm).BRANCHIAL ARCHESFirst arch derivatives# Meckel's cartilage: Mandible, malleus, incus, sphenomandibular ligament.# Muscles: Muscles of mastication (temporalis, masseter, lateral and medial pterygoids), Tensor Tympani, Tensor veli Palatini, Mylohyoid, Anterior-belly of digastric.# Nerve of first arch: Mandibular nerve (post-trematic) and chorda tympani (pretrematic).Second arch derivatives# Reichert's cartilage: Stapes, Styloid, Smaller (lesser) horn & superior half of hyoid, Stylohyoid ligament (Hint--4'S').# Muscles: muscles of facial expression, Stapedius, Stylohyoid, posterior belly of digastric.Third arch derivatives# Cartilage. Greater horn of hyoid, lower half of hyoid.# Muscle: Stylopharyngeus# Nerve of third arch: Glossopharyngeal nerve.Fourth arch derivatives# Cartilages: thyroid, cricoid, arvtenoids, corniculate, cuneiform.# Muscles : Most pharyngeal constrictors, circothyroid, and levator veli palatini.# Nerve of Fourth arch: Superior laryngeal branch of vagus nerve. Fifth arch# Fifth arch Makes no major development contributions.Sixth arch derivatives# Muscles: all intrinsic muscles of larynx except cricothyroid.# Nerve of sixth arch: Recurrent laryngeal branch of vagus nerve.BRANCHIAL CLEFT DERIVATIVES# First cleft develops into external auditory meatus# Second to Fourth clefts form temporary cervical sinuses, which are obliterated by proliferation of second arch mesenchyme.# Persistent cervical sinus can lead to a branchial cyst in the neck.Educational points:Treacher Collins syndrome is first arch syndrome - mandibulofacial dysplasia - caused by autosomal dominant gene - resulting in malar hypoplasia with down-slanting palpebral fissures - defects in the lower eyelids - deformed external ears- and sometimes abnormalities of the middle and internal ears.Third and fourth pouch syndrome or DiGeorge' syndrome or CATCH syndrome:# Cleft palate,# Abnormal facies# Thymic aplasia T cell deficiency# Ca++ deficiency &# Heart defects