The earliest gland to appear in the embryo is?

Appeared in: BSF Staff Nurse - 2015

Explanation

The thyroid gland is the first endocrine gland to appear in the embryo.
Its development begins around day 24 of gestation as a thickening of the endoderm on the floor of the primitive pharynx.
This point of origin, at the base of the tongue, is known as the foramen cecum.
The gland then descends to its final position in the anterior neck by the 7th week.

Option A: The pituitary gland begins its development from the ectoderm (Rathke's pouch) around the 4th to 5th week of gestation, which is after the thyroid gland has already started to form.
Option C: The adrenal gland develops later. The adrenal cortex begins to form during the 6th week from mesoderm, and the medulla develops from neural crest cells.
Option D: The ovary (gonad) is one of the later endocrine glands to develop, beginning its formation from the mesodermal genital ridge around the 7th to 8th week of gestation.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Embryological development of endocrine glands as background academic context rather than a clinical decision trigger.
Knowledge of thyroid embryology is vital for nurses to understand congenital anomalies. A midline neck mass in a child could be a thyroglossal duct cyst, a remnant of the gland's descent.
An ectopic thyroid, often found at the base of the tongue (lingual thyroid), occurs when the gland fails to descend. This may be the patient's only functioning thyroid tissue.
What if? If a newborn presents with signs of congenital hypothyroidism (e.g., poor feeding, prolonged jaundice) and a physical exam reveals a mass at the base of the tongue, the nurse should suspect a lingual thyroid and anticipate orders for thyroid function tests and imaging.

How to Approach the Question

This is a factual recall question testing knowledge of embryology.
Identify the core question, which asks for the 'earliest' gland to appear.
Systematically recall the developmental timelines for the four endocrine glands listed in the options.
Compare the initiation times: Thyroid (Day 24), Pituitary (Week 4-5), Adrenal (Week 6), and Ovary (Week 7-8).
Select the gland with the earliest appearance date, which is the thyroid gland.

Concept Tested & Keywords

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E6 Obstetrics Williams p. 28-48

Practise the full BSF Staff Nurse - 2015

Attempt every question from this paper in a timed mock, then review the full solution for each one.