49 Questions
Which endocrine gland is directly associated with the regulation of metabolism?
Thyroid gland
Which of the following glands is found in the brain and influences sleep patterns?
Pineal gland
Which gland primarily controls the fight-or-flight response through hormone release?
Adrenal gland
Which structure acts as a major regulatory link between the nervous and endocrine systems?
Hypothalamus
Which gland is responsible for regulating calcium levels in the blood?
Parathyroid gland
Which structure connects the two lobes of the thyroid gland?
Isthmus
What is the primary function of parafollicular cells in the thyroid tissue?
Secretion of calcitonin
Approximately how much does the thyroid gland weigh in an adult?
30 grams
Where are the parathyroid glands located?
On the posterior surface of the thyroid gland
What are thyroid follicles filled with?
Thyroid colloid
What type of epithelium makes up the wall of thyroid follicles?
Simple cuboidal glandular epithelium
What percentage of the adrenal gland does the adrenal cortex comprise?
80-90%
During the embryonic development, into what two parts do the adrenal glands differentiate?
Outer cortex and inner medulla
Which hormones are secreted by the zona glomerulosa?
Mineralocorticoids
What is the primary function of the hormones secreted by the adrenal medulla?
Responding to stress
What is the largest zone of the adrenal cortex?
Zona fasciculata
Which hormone is secreted by alpha cells in the pancreatic islets?
Glucagon
What is the function of beta cells in the pancreatic islets?
Secrete insulin
Which of these hormones is NOT secreted by the adrenal medulla?
Aldosterone
Where is the pineal gland located?
Near the roof of the ventricle, attached to the thalamus
Which substance does not have ducts or canals and is secreted directly into the bloodstream by the pancreas?
Hormones from the islets cells
What triggers the increase in melatonin secretion by the pineal gland?
Decreased nerve impulses from the eyes in the dark
Which cells in the pancreatic islets are responsible for somatostatin secretion?
Delta cells
What is the primary function of the exocrine portion of the pancreas?
Secrete digestive enzymes
What is the distinguishing feature of the pancreatic islets in hormone secretion?
They secrete hormones directly into the bloodstream
Which of the following hormones is not stored in the neurohypophysis?
Follicle-stimulating hormone (FSH)
Where are the cell bodies of the neurons that release hormones from the neurohypophysis located?
Supraoptic and paraventricular nuclei of the hypothalamus
What is the main type of cells that surround neurons in the neurohypophysis?
Pituicytes
How does arterial blood reach the anterior pituitary?
Through a capillary bed in the hypothalamus
What directly inhibits the release of hormones from the anterior pituitary?
Inhibiting hormones from the hypothalamus
What is transported along the hypothalamohypophyseal tract?
Posterior pituitary hormones
Which structure ensures that hormone release from the anterior pituitary is closely regulated?
Hypothalamus
Which hormones are stored and released by the neurohypophysis?
Antidiuretic hormone (ADH) and Oxytocin (OT)
Where are the parathyroid glands located?
Embedded in the posterior surface of each lobe of the thyroid gland
What is the primary function of chief cells in the parathyroid gland?
To produce parathyroid hormone (PTH)
How are the secretory cells of the parathyroid glands arranged?
Tightly packed and closely associated with capillary networks
Which characteristic is true of oxyphil cells in the parathyroid glands?
Their function is unknown
What is the approximate weight of a parathyroid gland?
0.04g
Which of the following hormones is secreted by the adrenal medulla and accounts for the majority of its secretion?
Epinephrine
What type of tissue composes the adrenal medulla?
Neurosecretory tissue
What type of embryonic tissue do the cells of the adrenal medulla develop from?
Neural crest tissue
Which of the following accurately describes the zona reticularis of the adrenal cortex?
It produces small amounts of weak androgens.
What is the primary function of the pancreas in terms of its dual nature?
Functions as both an exocrine and endocrine gland
How is the adrenal medulla innervated?
By sympathetic preganglionic fibers
Which group of cells in the adenohypophysis is responsible for the secretion of thyroid stimulating hormone (TSH)?
Thyrotrophs
Where is the pituitary gland located?
In the sphenoid bone
Which hormone is NOT secreted by somatotrophs, corticotrophs, thyrotrophs, lactotrophs, or gonadotrophs in the adenohypophysis?
Insulin
What structure connects the pituitary gland to the hypothalamus?
Infundibulum
Which type of cells in the adenohypophysis secrete prolactin (PRL)?
Lactotrophs
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
Learn about the structure and composition of the thyroid gland, its location in the neck, and its vascular properties.
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