Embryology Flashcards
Products of the second pharyngeal arch are…
Stapes and stapedius Styloid process and stylohyoid Stylohyoid ligament Lesser horn Superior part of hyoid bone Muscles of facial expression Posterior belly digastric (Facial nerve)
Products of the first pharyngeal arch are…
Meckel's cartilage Mandible Malleus and Incus SphenoMandibular ligament Anterior ligament of malleus Lingula Muscles of mastication Two tensor muscles (tymp and palati) MM of ant. 2/3 tongue Maxillary artery Mylohyoid and ant. belly digastric (Maxillary br. of Trigeminal nerve)
Products of the third pharyngeal arch are….
Greater horn and inferior of hyoid bone
Stylopharyngeus
(Glossopharyngeal nerve)
Products of the fourth and sixth pharyngeal arches are…
Thyroid Cricoid Epiglottic and arytenoid cartilages Intrinsic muscles of the larynx Muscles of the pharynx Levator palati (Vagus nerve)
Lateral derivatives of the first pharyngeal arch are…
Auditory tube
Tympanic membrane
Mastoid antrum
Lateral derivatives of the second pharyngeal arch are…
Tympanic cavity
Tonsillar crypts
Supratonsillar fossa
Lateral derivatives of the third pharyngeal pouch are…
Inferior parathyroid gland
Thymic rudiments
Each gives a lobe to the thymus
Lateral derivatives of the fourth pharyngeal pouch are…
Superior parathyroid glands
Lateral derivatives of the fifth pharyngeal pouch are…
Ultimobranchial body which donate para follicular (C) cells to the thyroid which produce calcitonin.
What pouches give rise to the tongue?
Buds from the first, third, and fourth arches form the storms of the tongue.
(Hypoglossal nerve)
What are the remnants of the Müllerian ducts in a male?
Disappears in the male except at either end:
Upper end persists as appendix testis
Lower end persists as prostatic utricle.
What does the mesonephric (Wolffian) duct form in the male?
The Wolffian duct forms the epididymis and vas.
What does the metanephros contribute to male genitalia?
The metanephros tubules persist and attach to the testis creating vasa efferentia. These drain products of the tested into the mesonephric duct. Some are blind ending and form vasa abberentia, the appendix of the epididymis is an example of this.
What does the mesonephric (Wolffian) contribute to in female genitalia?
The mesonephric duct and tubules usually disappear in the female. Remnant can be found in the mesosalpinx as the epoophoron and in the base of the broad ligament as the paroophoron.
What do the Mullerian ducts contribute to in the female?
The fuse at their caudal ends to form the uterus and continue to reach the dorsal wall of the urogenital sinus thereby forming the upper part of the vagina. Their cranial ends persist as uterine tubes.
Which major fetal veins persist in the term fetus?
Left umbilical
Right vitelline
Right cardinal
What are the 4 sources from which the diaphragm develops?
- Septum transversum (central tendon)
- 3rd, 4th, 5th cervical myotomes
- Pleuroperitoneal membranes
- Oesophageal mesentery.
Describe the development of the foramen ovale:
The primary septum grows downwards towards the endocardial cushions, but does not fuse. The gap remaining is the primary foramen. Before the ostium primum can be obliterated, the ostium secondum is formed. Now, the septum secundum grows down, though does not enclose the ostium secundum entirely. This gap is the foramen ovale.
What is the fate of the sinus venosus?
The right horn becomes incorporated into the right atrium, forming its smooth part and accounting for the SVC and IVC draining into it. The rest of the sinus venosus persists as the coronary sinus, with the left horn being represented by the oblique vein of the left atrium.
What is the fate of the truncus arteriosus?
This becomes divided by two internal swellings, the right and left bulbar ridges, which meet to form the aorticopulmonary septum. The septum spirals down, turning 180* to join the posterior endocardial cushion to form the membranous part of the IV septum.
From where does the SA node develop?
Sinus venosus tissue
From where do the AV node and bundle arise?
The original atrial tissue.
What is the Tetralogy of Fallot?
What is the cause?
- Pulmonary stenosis
- Over-riding aorta
- Defect in membranous IV septum
- RV hypertrophy.
Due to unequal division of the Truncus Arteriosus.
What is the fate of the 3rd branchial arch artery?
The 3rd remains as the common and internal carotid arteries.
What is the fate of the 4th branchial arch artery?
The 4th on the right contributes to the subclavian, on the left to the arch of the aorta.
Which branchial arch artery persists as the ligamentum arteriosum?
The 6th branchial arch artery on the left. On the right, the dorsal part of the 6th disappears.
Describe the course and cause of a non-recurrent right laryngeal nerve:
Commonly caused by failure of the brachiocephalic trunk to arise from the normal location (arises instead from left of the the common carotid).
Occurs in 1% of people. Hazard during thyroidectomy.
What is the incidence and cause of a cleft lip?
Cleft lips occur in 1 in 1000 births. They are caused by failure of fusion of the maxillary and medial nasal prominences.
What is the incidence and cause of a cleft palate?
Cleft palate occurs in 1 in 2500 births. It may be partial or complete and is caused by failure of the two palatal processes to unite. It may cause a bifid uvula or complete cleft palate.
