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Questions and Answers
Which endocrine gland is directly associated with the regulation of metabolism?
Which endocrine gland is directly associated with the regulation of metabolism?
Which of the following glands is found in the brain and influences sleep patterns?
Which of the following glands is found in the brain and influences sleep patterns?
Which gland primarily controls the fight-or-flight response through hormone release?
Which gland primarily controls the fight-or-flight response through hormone release?
Which structure acts as a major regulatory link between the nervous and endocrine systems?
Which structure acts as a major regulatory link between the nervous and endocrine systems?
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Which gland is responsible for regulating calcium levels in the blood?
Which gland is responsible for regulating calcium levels in the blood?
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Which structure connects the two lobes of the thyroid gland?
Which structure connects the two lobes of the thyroid gland?
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What is the primary function of parafollicular cells in the thyroid tissue?
What is the primary function of parafollicular cells in the thyroid tissue?
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Approximately how much does the thyroid gland weigh in an adult?
Approximately how much does the thyroid gland weigh in an adult?
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Where are the parathyroid glands located?
Where are the parathyroid glands located?
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What are thyroid follicles filled with?
What are thyroid follicles filled with?
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What type of epithelium makes up the wall of thyroid follicles?
What type of epithelium makes up the wall of thyroid follicles?
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What percentage of the adrenal gland does the adrenal cortex comprise?
What percentage of the adrenal gland does the adrenal cortex comprise?
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During the embryonic development, into what two parts do the adrenal glands differentiate?
During the embryonic development, into what two parts do the adrenal glands differentiate?
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Which hormones are secreted by the zona glomerulosa?
Which hormones are secreted by the zona glomerulosa?
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What is the primary function of the hormones secreted by the adrenal medulla?
What is the primary function of the hormones secreted by the adrenal medulla?
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What is the largest zone of the adrenal cortex?
What is the largest zone of the adrenal cortex?
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Which hormone is secreted by alpha cells in the pancreatic islets?
Which hormone is secreted by alpha cells in the pancreatic islets?
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What is the function of beta cells in the pancreatic islets?
What is the function of beta cells in the pancreatic islets?
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Which of these hormones is NOT secreted by the adrenal medulla?
Which of these hormones is NOT secreted by the adrenal medulla?
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Where is the pineal gland located?
Where is the pineal gland located?
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Which substance does not have ducts or canals and is secreted directly into the bloodstream by the pancreas?
Which substance does not have ducts or canals and is secreted directly into the bloodstream by the pancreas?
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What triggers the increase in melatonin secretion by the pineal gland?
What triggers the increase in melatonin secretion by the pineal gland?
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Which cells in the pancreatic islets are responsible for somatostatin secretion?
Which cells in the pancreatic islets are responsible for somatostatin secretion?
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What is the primary function of the exocrine portion of the pancreas?
What is the primary function of the exocrine portion of the pancreas?
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What is the distinguishing feature of the pancreatic islets in hormone secretion?
What is the distinguishing feature of the pancreatic islets in hormone secretion?
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Which of the following hormones is not stored in the neurohypophysis?
Which of the following hormones is not stored in the neurohypophysis?
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Where are the cell bodies of the neurons that release hormones from the neurohypophysis located?
Where are the cell bodies of the neurons that release hormones from the neurohypophysis located?
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What is the main type of cells that surround neurons in the neurohypophysis?
What is the main type of cells that surround neurons in the neurohypophysis?
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How does arterial blood reach the anterior pituitary?
How does arterial blood reach the anterior pituitary?
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What directly inhibits the release of hormones from the anterior pituitary?
What directly inhibits the release of hormones from the anterior pituitary?
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What is transported along the hypothalamohypophyseal tract?
What is transported along the hypothalamohypophyseal tract?
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Which structure ensures that hormone release from the anterior pituitary is closely regulated?
Which structure ensures that hormone release from the anterior pituitary is closely regulated?
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Which hormones are stored and released by the neurohypophysis?
Which hormones are stored and released by the neurohypophysis?
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Where are the parathyroid glands located?
Where are the parathyroid glands located?
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What is the primary function of chief cells in the parathyroid gland?
What is the primary function of chief cells in the parathyroid gland?
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How are the secretory cells of the parathyroid glands arranged?
How are the secretory cells of the parathyroid glands arranged?
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Which characteristic is true of oxyphil cells in the parathyroid glands?
Which characteristic is true of oxyphil cells in the parathyroid glands?
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What is the approximate weight of a parathyroid gland?
What is the approximate weight of a parathyroid gland?
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Which of the following hormones is secreted by the adrenal medulla and accounts for the majority of its secretion?
Which of the following hormones is secreted by the adrenal medulla and accounts for the majority of its secretion?
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What type of tissue composes the adrenal medulla?
What type of tissue composes the adrenal medulla?
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What type of embryonic tissue do the cells of the adrenal medulla develop from?
What type of embryonic tissue do the cells of the adrenal medulla develop from?
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Which of the following accurately describes the zona reticularis of the adrenal cortex?
Which of the following accurately describes the zona reticularis of the adrenal cortex?
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What is the primary function of the pancreas in terms of its dual nature?
What is the primary function of the pancreas in terms of its dual nature?
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How is the adrenal medulla innervated?
How is the adrenal medulla innervated?
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Which group of cells in the adenohypophysis is responsible for the secretion of thyroid stimulating hormone (TSH)?
Which group of cells in the adenohypophysis is responsible for the secretion of thyroid stimulating hormone (TSH)?
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Where is the pituitary gland located?
Where is the pituitary gland located?
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Which hormone is NOT secreted by somatotrophs, corticotrophs, thyrotrophs, lactotrophs, or gonadotrophs in the adenohypophysis?
Which hormone is NOT secreted by somatotrophs, corticotrophs, thyrotrophs, lactotrophs, or gonadotrophs in the adenohypophysis?
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What structure connects the pituitary gland to the hypothalamus?
What structure connects the pituitary gland to the hypothalamus?
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Which type of cells in the adenohypophysis secrete prolactin (PRL)?
Which type of cells in the adenohypophysis secrete prolactin (PRL)?
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Study Notes
Thyroid Gland
- Located in the neck, on the anterior and lateral surfaces of the trachea, just below the larynx
- Composed of two lobes connected by an isthmus, with a weight of around 30 grams in an adult
- Highly vascular gland surrounded by a fibrous capsule
Thyroid Tissue
- Composed of tiny structural units called follicles, which are the site of synthesis of thyroid hormones
- Each follicle is a small hollow sphere with a wall of simple cuboidal glandular epithelium
- The interior of the follicle is filled with a thick fluid called thyroid colloid
- The colloid is produced by the cuboidal cells of the follicle wall and contains protein-iodine complexes known as thyroglobulins, the precursors of thyroid hormones
- Parafollicular cells (C-cells) are located between the follicles and secrete the hormone calcitonin
Parathyroid Glands
- Four small, oval glands located on the posterior surface of the thyroid gland
- Each gland weighs around 40 mg (0.04 grams)
- Composed of a thin brown parenchyma packed with secretory cells
- Produce parathyroid hormone, which regulates calcium levels in the blood
Pancreas
- Endocrine portion consists of groups of cells closely associated with blood vessels
- Cells are grouped in clusters or islets, called pancreatic islets (islets of Langerhans)
- Three main types of cells in the pancreatic islets:
- Alpha or A cells: secrete glucagon
- Beta or B cells: secrete insulin
- Delta or D cells: secrete somatostatin (GHIH) by hypothalamus
Pineal Gland
- Small, cone-shaped structure, reddish brown in color, located deep between the cerebral hemispheres
- Attached to the upper portion of the thalamus near the roof of the ventricle
- Secrete the hormone melatonin in response to light and darkness
Thymus Gland
- Discussed in the lymphatic system (unit 8)
Ovaries and Testes
- Structures are described in the reproductive system (unit 15)
Endocrine System
- Composed of endocrine glands located throughout the body
- Glands are commonly called ductless glands because the hormones they release pass directly into the bloodstream
- Major endocrine glands include:
- Hypothalamus
- Pituitary gland
- Pineal gland
- Parathyroid gland
- Thyroid gland
- Thymus
- Kidney
- Adrenal gland
- Pancreas
- Testis (in male)
- Ovary (in female)
Anterior Pituitary
- Supplied with arterial blood indirectly through the pituitary portal system
- Blood provides oxygen and nutrients and also transports releasing and inhibiting hormones from the hypothalamus
- Release of anterior pituitary hormones is stimulated by releasing hormones and suppressed by inhibiting hormones from the hypothalamus
Neurohypophysis (Posterior Pituitary)
- Serves as a storage and release site for two hormones: ADH and Oxytocin
- Consists of nerve cells (neurons) surrounded by supporting cells called pituicytes
- Hormones are synthesized in the nerve cell bodies in the supraoptic and paraventricular nuclei of the hypothalamus and transported along the axon
Adrenal Glands
- Two small, flattened pyramidal shaped glands situated on the upper pole of each kidney
- Each gland weighs about 3.5 to 5 grams and is yellowish in color
- Divided into two structurally and functionally distinct parts: cortex and medulla
- Adrenal cortex is subdivided into three zones: zona glomerulosa, zona fasciculata, and zona reticularis
- Adrenal medulla secretes hormones called catecholamines, such as epinephrine (adrenaline), norepinephrine (noradrenaline), and dopamine
Parathyroid Glands (Anatomy)
- Four small parathyroid glands, two embedded in the posterior surface of each lobe of the thyroid gland
- Each gland weighs about 40mg (0.04g) and is surrounded by a thin capsule of connective tissue
- Body of the gland consists of many tightly packed secretory cells, spherical in shape, and closely associated with capillary networks
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Description
Learn about the structure and composition of the thyroid gland, its location in the neck, and its vascular properties.
