Podcast
Questions and Answers
What is the primary hormone secreted by the chief cells of the parathyroid gland?
What is the primary hormone secreted by the chief cells of the parathyroid gland?
Which zone of the adrenal cortex produces mineralocorticoids?
Which zone of the adrenal cortex produces mineralocorticoids?
What hormones are secreted by the adrenal medulla?
What hormones are secreted by the adrenal medulla?
Which cells in the pancreas are responsible for producing insulin?
Which cells in the pancreas are responsible for producing insulin?
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What role do kidneys play in hormone production?
What role do kidneys play in hormone production?
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Which part of the pancreas has an exocrine function?
Which part of the pancreas has an exocrine function?
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What do cardiac muscles secrete to help decrease blood volume and blood pressure?
What do cardiac muscles secrete to help decrease blood volume and blood pressure?
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What is the primary role of hormones in the endocrine system?
What is the primary role of hormones in the endocrine system?
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What hormone does the liver convert cholecalciferol into?
What hormone does the liver convert cholecalciferol into?
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Where are the adrenal glands located?
Where are the adrenal glands located?
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Which gland is located inferior to the hypothalamus and connected by the infundibulum?
Which gland is located inferior to the hypothalamus and connected by the infundibulum?
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What is the unknown function of oxyphil cells in the parathyroid gland?
What is the unknown function of oxyphil cells in the parathyroid gland?
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What type of tissue primarily composes the posterior pituitary gland?
What type of tissue primarily composes the posterior pituitary gland?
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What connects the hypothalamus and the anterior pituitary gland?
What connects the hypothalamus and the anterior pituitary gland?
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Which hormone is NOT typically associated with the function of the thymus gland?
Which hormone is NOT typically associated with the function of the thymus gland?
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What is the role of the hypothalamus in relation to the endocrine system?
What is the role of the hypothalamus in relation to the endocrine system?
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What anatomical feature separates the right and left lobes of the thyroid gland?
What anatomical feature separates the right and left lobes of the thyroid gland?
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In which part of the pituitary does the majority of adenomas originate?
In which part of the pituitary does the majority of adenomas originate?
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What does the term 'endocrinology' refer to?
What does the term 'endocrinology' refer to?
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Which of the following statements about gap junctions is true?
Which of the following statements about gap junctions is true?
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Study Notes
Endocrine System Overview
- The endocrine system is composed of glands, tissues, and cells that secrete hormones
- Endocrinology is the study of the endocrine system, its diagnosis, and treatment of disorders
- Endocrine glands are organs that produce hormones
Mechanisms of Communication
- The body uses four main methods of communication between cells:
- Gap junctions: allow electrical currents to flow directly between cells
- Neurotransmitters: chemical messengers released by neurons to communicate with target cells
- Paracrines: chemical messengers that act locally on nearby cells
- Hormones: chemical messengers that travel through the bloodstream to distant target cells
Hypothalamus and Pituitary Gland
- The hypothalamus is the control center of the endocrine system, regulating the release of pituitary hormones
- Hypothalamus secretes releasing hormones (RH) and inhibiting hormones (IH). These regulate the anterior pituitary
- The pituitary gland is often called the "master gland." It's made of two parts: anterior and posterior.
- Anterior pituitary consists of three parts- the pars tuberalis, the pars intermedia and the pars distalis.
- The hypothalamo-hypophyseal tract connects the hypothalamus to the posterior pituitary
Posterior Pituitary (Neurohypophysis)
- The posterior pituitary is composed of nerve tissue, not a true gland
- Hypothalamic neurons secrete hormones that are stored in the neurohypophysis until released into the blood. These hormones released from the posterior pituitary include oxytocin and antidiuretic hormone (ADH).
Anterior Pituitary (Adenohypophysis)
- The anterior pituitary is linked to the hypothalamus by the hypophysial portal system.
- Hypothalamic hormones regulate anterior pituitary cells. These regulate the release of other hormones from the anterior pituitary.
Hypothalamus-Pituitary-Target Organs
- Various hypothalamic releasing hormones (TRH, GnRH, CRH, GHRH, etc.) trigger the release of hormones (PRL, TSH, ACTH, FSH, LH, and GH) from the anterior pituitary
- These regulate many target organs, including the liver, thyroid, gonads, adrenal cortex, and mammary gland.
Pituitary Gland Anatomy
- The pituitary gland (hypophysis) is located inferior to the hypothalamus, connected by the infundibulum
- It's housed in the sella turcica of the sphenoid bone
- It's divided into two parts: anterior (adenohypophysis) and posterior (neurohypophysis)
Pituitary Adenoma
- Pituitary adenomas are neoplasms of neuroendocrine epithelial cells
- Most originate in the adenohypophysis
- Adenomas are classified as microadenomas (<10mm) or macroadenomas (>10mm)
Thymus
- The thymus plays a role in the endocrine, lymphatic, and immune systems.
- Located in the mediastinum, superior to the heart
- Goes through involution after puberty.
- The gland produces hormones like thymopoietin, thymosin, and thymulin
Thyroid and Parathyroid Glands
- The thyroid gland is butterfly-shaped and located inferior to the larynx, anterior to trachea, with right and left lobes connected by an isthmus.
- Thyroid follicles, the main component of the gland, contain colloid (rich in iodine).
- Thyroid follicular cells surround the follicles and produce thyroid hormones.
- The parathyroid glands, usually four small glands on the posterior surface of the thyroid, contain chief cells (secrete PTH) and oxyphil cells (function unknown)
Adrenal Glands
- Adrenal glands sit atop the kidneys and are divided into two parts:
- Adrenal cortex: produces steroid hormones (mineralocorticoids, glucocorticoids, and gonadocorticoids)
- Adrenal medulla: produces epinephrine and norepinephrine
Pancreas
- The pancreas is located between the duodenum and spleen
- It has both exocrine (digestive enzymes) and endocrine (hormones) functions
- Pancreatic islets (islets of Langerhans) are small clusters of endocrine cells
- These release hormones (e.g., insulin, glucagon, somatostatin).
Other Tissues/Organs with Endocrine Functions
- Adipose tissue: secretes leptin and estrogens
- Heart: secretes atrial-natriuretic peptide and brain-natriuretic peptide
- Bone marrow: secretes thrombopoietin
- These are additional tissues/organs that produce hormones.
- Kidneys: Convert calcidiol to calcitriol, secrete renin which converts angiotensinogen to angiotensin I and produce ~85% of erythropoietin.
- Skin: keratinocytes convert cholesterol-like steroids into cholecalciferol using UV from sun
- Liver: produces numerous hormones, including converting cholecalciferol to calcidiol, secreting angiotensinogen, 15% erythropoietin, IGF-I and hepcidin
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