Steroid and Thyroid Hormones Transport Quiz
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Questions and Answers

What is the dual embryologic origin of the hypophysis (pituitary gland)?

  • Mesodermal and neural
  • Ectodermal and endodermal
  • Epithelial and neural (correct)
  • Endodermal and mesodermal

    • Which part of the brain forms the neural portion (neurohypophysis) of the hypophysis?

  • Hypothalamus (correct)
  • Cerebellum
  • Midbrain
  • Medulla oblongata

    • What is the name of the neural stalk that connects the neurohypophysis to the hypothalamus?

  • Pars nervosa
  • Pars tuberalis
  • Infundibulum (correct)
  • Median eminence

    • Which part of the adenohypophysis (anterior pituitary) is the largest?

    <p>Pars distalis</p> Signup and view all the answers

    What is the purpose of the hypothalamo-hypophyseal portal system?

    <p>To carry releasing and inhibiting hormones from the hypothalamus to the adenohypophysis</p> Signup and view all the answers

    What is the function of the pituicytes in the neurohypophysis?

    <p>To provide structural support for the axons</p> Signup and view all the answers

    What is the function of the superior hypophyseal arteries?

    <p>They form a primary capillary plexus in the median eminence</p> Signup and view all the answers

    Where do the secretory neurons in the hypothalamus terminate?

    <p>On the capillary plexus in the median eminence</p> Signup and view all the answers

    What is the purpose of the hypothalmo-hypophyseal tract?

    <p>To transport hormones from the hypothalamus to the posterior pituitary</p> Signup and view all the answers

    Where are the neurons that synthesize oxytocin and antidiuretic hormone (ADH) located?

    <p>In the supraoptic and paraventricular nuclei of the hypothalamus</p> Signup and view all the answers

    What is the function of the Herring bodies in the neurohypophysis?

    <p>They store the hormones synthesized by the hypothalamic neurons</p> Signup and view all the answers

    How do hydrophobic steroid and thyroid hormones enter target cells?

    <p>By diffusing through the cell membranes</p> Signup and view all the answers

    What is the role of transport proteins in the circulation of hydrophobic hormones?

    <p>Aid in hormone circulation but prevent diffusion into cells</p> Signup and view all the answers

    Where do hydrophobic steroid and thyroid hormones primarily activate receptors in target cells?

    <p>Nucleus</p> Signup and view all the answers

    What happens to hydrophobic hormones after circulating on transport proteins?

    <p>They diffuse through cell membranes to activate receptors</p> Signup and view all the answers

    Why can hydrophobic steroid and thyroid hormones diffuse through cell membranes?

    <p>As they are lipid-soluble molecules</p> Signup and view all the answers

    What is the mechanism of transmission for direct chemical messengers?

    <p>Direct movement through gap junctions</p> Signup and view all the answers

    Which of the following is an example of a synaptic neurotransmitter?

    <p>Acetylcholine</p> Signup and view all the answers

    What is the mechanism of transmission for paracrine chemical messengers?

    <p>Diffusion through extracellular fluid to nearby cells</p> Signup and view all the answers

    Which of the following is an example of an autocrine chemical messenger?

    <p>Cytokine interleukin-1</p> Signup and view all the answers

    What is the mechanism of transmission for endocrine chemical messengers?

    <p>Carried in the bloodstream to distant cells</p> Signup and view all the answers

    Which characteristic of endocrine hormones is mentioned in the text?

    <p>They are carried in the bloodstream to target cells</p> Signup and view all the answers

    What is the main function of somatotrophs?

    <p>Produce somatotropin for growth hormone</p> Signup and view all the answers

    Which hormone inhibits the release of growth hormone from somatotrophs?

    <p>Somatostatin</p> Signup and view all the answers

    What is the role of FSH in females?

    <p>Induces ovulation and corpus luteum formation</p> Signup and view all the answers

    What does prolactin primarily stimulate?

    <p>Milk production after parturition</p> Signup and view all the answers

    Which hormone is responsible for the production of testosterone in males?

    <p>Luteinizing hormone (LH)</p> Signup and view all the answers

    What is the main function of corticotrophs?

    <p>Regulate adrenal cortex functions</p> Signup and view all the answers

    Study Notes

    Embryologic Development of Hypophysis (Pituitary Gland)

    • The hypophysis (pituitary gland) has a dual embryologic origin, consisting of both epithelial and neural portions.
    • The epithelial portion develops from the pharyngeal roof and Rathke's pouch.
    • The pouch detaches and becomes the cellular portion, the adenohypophysis.
    • The downgrowth of the brain forms the neural portion, the neurohypophysis.
    • The neurohypophysis remains attached to the hypothalamus by a neural stalk, called the infundibulum.
    • Neurons in the hypothalamus control the release of hormones from the adenohypophysis.

    Subdivision of Hypophysis

    Adenohypophysis (Anterior Pituitary)

    • Pars distalis is the largest part.
    • Pars intermedia is a remnant of the pouch and is rudimentary in humans.
    • Pars tuberalis surrounds the neural stalk.

    Neurohypophysis (Posterior Pituitary)

    • Median eminence is located at the base of the hypothalamus.
    • Infundibulum is the neural stalk that connects the neurohypophysis to the hypothalamus.
    • Pars nervosa is the largest portion and consists of unmyelinated axons and pituicytes.

    Vascular and Neural Connections of Hypophysis

    • The connection between the hypothalamus of the brain and the adenohypophysis is vascular, forming the hypothalamohypophyseal portal system.
    • This system carries releasing and inhibiting hormones from the ventromedial, arcuate, preoptic, and paraventricular nuclei to bind at specific receptors in cells of the pars distalis.
    • Superior hypophyseal arteries form a fenestrated primary capillary plexus in the median eminence.
    • Secretory neurons in the hypothalamus terminate on the capillary plexus and release hormones.
    • Small venules connect to a secondary capillary plexus in the adenohypophysis, forming a portal system.

    Cells and Hormones of Adenohypophysis

    • There are three cell types based on stains: acidophils, basophils, and chromophobes.
    • Acidophils:
    • Somatotrophs secrete somatotropin (growth hormone) for cell metabolism and general body growth.
    • Mammotrophs produce prolactin that stimulates mammary gland development during pregnancy and maintains milk production after parturition.
    • Basophils:
    • Thyrotrophs release thyroid-stimulating hormone (TSH) that stimulates the thyroid gland to produce thyroxin and triiodothyronine.
    • Gonadotrophs secrete follicle-stimulating hormone (FSH) and luteinizing hormone (LH).
    • Corticotrophs secrete adrenocorticotropic hormone (ACTH) to regulate adrenal cortex functions.

    Neurohypophysis

    • Does not have any secretory cells; secretory neurons are located in the hypothalamus of the brain.
    • Releases two hormones from axon terminals: oxytocin and antidiuretic hormone (ADH).

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    Test your knowledge on how hydrophobic steroid and thyroid hormones circulate on transport proteins and activate cytoplasmic receptors in target cells.

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