Head and Neck II Flashcards
When do pharyngeal arches begin developing?
Around 3rd week of gestation in domestic animals
What are invaginations of ectoderm formed between adjacent arches called?
Pharyngeal grooves or clefts
What produces pharyngeal pouches?
Endoderm of the expanding foregut evaginates between the arches
What does contact of cleft and pouches form?
Pharyngeal membranes
What makes up the pharygneal complex?
Pharyngeal Arches
Clefts
Pouches
What 3 things are associated with each pharyngeal arch?
Aortic arch artery
Muscle component
Branch of Cranial nerve
What is somitomere?
Give off myogenic cells, which are very migratory. Allow for muscle formation in face and pharynx
What do aortic arch arteris form from?
Mesoderm within each arch
What do aortic arch arteries form?
Vascular link to aortic sac and paired dorsal aortae
What do cranial-caudal body folding result in?
Cranial parts of dorsal aortae bending and forming aortic arches lateral to the foregut
Which aortic arch develops first?
Anterior - forms and then remaining develop sequentially
What is the second or hyoid arch?
Reichert’s cartilage - gives rise to stapes of middle ear. Bones of hyoid apparatus
What is third arch
Other bones of hyoid apparatus, stylopharyngeus muscle which dilates pharynx
What are 4th-6th arches?
Laryngeal cartilages
What doe endodermal epithelium of pouches differentiate into?
Components of lymphatic and endocrine system
In the late fetal period, what does second pouch contain?
Aggregate of tissue - palatine tonsil (lymphatic tissue)
From where do parathyroid glands develop?
Dorsal parts of the 3rd and 4th pouches
Slide 9
What occurs with caudal migration of thyroid?
Parathyroid IV glands become embeded into thyroid gland
Where are parathyroid III gland located?
Caudal to thyroid
What does Parathyroid hormone do?
Increases blood calcium levels
What is structure of thymus initially?
Two separate tubular structures
What occurs as separate tubular structures of thymus extend caudallY/
They eventually fuse in midline and become associated with pericardium
What does thymus produce?
Thymic hormones responsible for making competent T-lymphocytes involved in cellular immune responses
What is the 1st pouch?
Auditory (Eustachian) tubes of ear and tympanic cavities
What occurs in first pouch of horses?
A diverticula of auditory tubes lead to development of guttural pouches
What are guttural pouches?
Mucus secreting sacs that communicate with pahrynx
What is first cleft?
Ectoderm of cleft gives rise to epithelial lining of external auditory meatus
What forms cervical sinus?
Second arch extends caudally over 2nd and 3rd clefts. A transient structure lined by ectoderm then forms cervical sinus
Where does tongue develop?
Develops on floor of oral cavity from portion of 1st pharyngeal arch.
What are the 3 elevations that occur at the region of the 1st arch due to underlying mesoderm grwoth?
Two lateral lingual swellings
One tuberculum impar
What develops at 2nd pharyngeal arch with regards to tongue?
Copula
With regards to tongue what develops at 3rd and 4th arches?
Hypopharyngeal eminence forms
