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Flashcards in Exam 2 Embryology Deck (27)
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Which pharyngeal arche(s) of the head and neck are rudimentary?

5th (we only refer to arches 1,2,3,4 and 6)


The 6th pharyngeal arch becomes incorporated into the...

4th arch



Refers to the germ layer derivatives of the pharyngeal components.

Clefts= Ectoderm
Arches= Mesoderm
Pouches= Endoderm


Derivatives of the Pharyngeal Arches and Their Innervation

At the restaurant of the golden ARCHES, children tend to:

(1st arch) CHEW- Muscles of mastication- 5th cranial nerve (V2 and V3- anterior digastric, tensors, etc.)

(2nd arch) SMILE- Muscles of facial expression (buccinators, posterior belly digastric, stylohyoid, etc.)- 7th cranial nerve

(3rd arch) STYLISH- stylopharyngeous muscle- 9th cranial nerve

(4th arch) SWALLOW- pharynx muscles (levator palitine, cricothyroid, constrictors)- 10th cranial nerve

(6th arch) SPEAK- larynx muscle- 10th cranial nerve


Pharyngeal Pouches

Ear, Tonsils, Bottom To Top

(1) Tympanic (middle ear) cavity; Auditory (Eustachian) tube
(2) Palatine tonsils; Tonsililar fossa
(3) Inferior parathyroid gland; Thymus
(4) Superior parathyroid gland


Fate of the Pharyngeal Clefts

1ST CLEFT: External auditory meatus

2ND, 3RD and 4TH CLEFTS: Supposed to be obliterated via the 2nd and 4th growing towards each other.


What occurs if the 2-4th pharyngeal clefts are not properly obliterated?

Branchial cyst will form on the neck. Found on the side of the neck


Thyroglossal cyst

Occur if the thyroid is not properly pulled to neck midline. Found along the midline of the neck and near tongue


Which of the aortic arches are not present at birth (or do we not care about?)

1st, 2nd, and 5th


Derivatives of the Aortic Arches (3-6)

(3) Common carotid and first part of internal carotid arteries

(4-left side) Arch of the aorta from the left common carotid to the left subclavian arteries

(4-right side) Right subclavian artery

(6-left side) Left pulmonary artery and ductus arteriosus (sometimes recurrent laryngeal goes over this)

(6-right side) Right pulmonary artery


The heart comes out of which germ layer?

Mesoderm. Sinuses (Oblique and Transverse) are the spaces which remain after development.


What embryological area develops into the smooth part of the ventricles?

Bulbus Cordis


What embryological area develops into the rough part of the ventricles?

The "ventricle" portion


What embryological area develops into the coronary sinuses?

Sinus venosus


Ventral mesentery develops into what?

It is only in the foregut.

It develops into the falciform ligament of the liver, as well as the lesser omentum.


Dorsal mesentery is found where?

It is found embryological in the posterior body wall and covers the entire length of the gut.


Organs which start in the midline and then rotate?

Stomach, Spleen, Liver


What is the axis of rotation in the midgut?

SMA (270 degree counter clockwise rotation.


Physiological hernia

Some of the guttube leaves the abdominal cavity to allow for space for it to grow (happens at 6-10 weeks). It then comes back when the cavity is larger. If it doesn't come back, bay is born with a hernia.


Another words for hindgut



Embryologically, the stomach begins as...

A dilation of the foregut


In what way does the stomach eventually rotate?

90 degrees, and clockwise on the longitudinal axis


Urorectal septum divides the _____ to give the ______ posteriorly and the _____ anteriorly.

-Rectum [anorectal canal](posteriorly)
-Urogenital sinus (which goes on to give the urinary bladder(anterior)


Embryological derivation of the bladder

Most of the bladder comes from the hindgut component of the ENDODERM (urogenital sinus), except for the TRIGONE which has MESODERMAL origin, because it is the opening of the two ureters and urethra which are mesodermic (just like the kidneys).


The name of the original "3rd kidney"

Pronephros. Found at the Posterior Superior portion of the fetus.


Where is the kidney located at the beginning of development?

Pelvis. It then ascends


What does the kidney begin as?

Ureteric bud