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107 Cards in this Set
- Front
- Back
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What is the best way to approach the study of organs?
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Study the layers first. Learn the cells characteristic to each layer/region. Finally, study additional features to the layers
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What is the parenchyma of the organ?
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the specialized cells of the organ
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What is the stroma of the organ?
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the supporting cells of the organ
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Where is the pituitary gland?
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midline, inferior to the brain
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What is the name of the depression the pituitary gland is in?
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sella turcica
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What part of the brain is the pituitary gland attached to?
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the hypothalamus
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What is a key role of the pituitary gland?
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to integrate the endocrine and nervous systems
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What controls the secretion of pituitary hormones?
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Hormones released from the hypothalamus neurons
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What do the hormones secreted from the pituitary do?
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regulate other endocrine cells
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Where are hormones from the hypothalamus released from?>
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The pituitary gland
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Name the 2 regions of the pituitary gland
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Neurohypophysis and Adenohypophysis
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What does the neurohypophysis develop from?
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an outgrowth of the diencephalon
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Describe the histology of the neurohypophysis
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nerve-like
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Name the 2 parts of the neurohypophysis
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infundibulum and the pars nervosa
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Name the 2 subdivisions of the infundibulum
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median eminence and the infundibular stalk
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Describe how the median eminence and the infundibular stalk relate to one another
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Median eminence is continuous with the hypothalamus, the infundibular stalk is continuous with the median eminence
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Describe the histology of the adenohypophysis
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endocrine-like
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How does the adenohypophysis develop?
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As an invagination of the ectoderm lining the roof of the stomodeum
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What is Rathke's Pouch?
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The invagination of ectoderm that will create the adenohypophysis
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Name the three structures that make up the adenohypophysis
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Pars distalis, pars intermedia, and pars tuberalis
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Describe the fate of Rathke's Pouch
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remains canalized and is called Rathke's Cleft. In adults, it can also be reduced to several cysts
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How does the pars distalis form?
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the anterior side of Rathke's pouch proliferates
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How and where does the pars intermedia form?
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The cells adjacent to the pars nervosa differentiate to form pars intermedia
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Describe the formation of the pars tuberalis
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Form a necklace-type structure wrapping around the infundibulum at the superior aspect of the adenohypophysis
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Describe the capsule of the pituitary
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Dense connective tissue that is continuous with the dura mater of the brain
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Describe the connective tissue composition within the pituitary gland
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very little connective tissue
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Which two regions of the adenohypophysis have similar histological structures?
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Pars distalis and the pars tuberalis
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Which aspect of the adenohypophysis is the most important?
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pars distalis
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What are chromophils?
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cells that have secretory granules that readily take up stain
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What are chromophobes?
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Cells that do not take up stain due to a lack of secretory granules
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Name 2 groups that the chromophils are subdivided into
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acidophils and basophils
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How are cells of the adenohypophysis currently named?
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according to the hormon they secrete
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Where are acidophils generally located within the pars distalis?
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lateral
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Where are thyrotrophs and corticotrophs typically located within the pars distalis?
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medially
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Name the 2 types of acidophils located in the pituitary
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somatotrophs and lactotrophs
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Describe the derivation of somatotrophs and lactotrophs
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Thought to be derived from a common precursor
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What are mammosomatrophs?
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Cells which secrete hormones from both somatotrophs and lactotrophs (growth hormone and prolactin)
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What do somatotrophs secrete?
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Growth Hormone
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Describe the regulation of growth hormone secretion from the pituitary
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Growth hormone releasing factor stimulates it, somatostatin inhibits it
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What is the most common cell of the adenohypophysis?
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somatotrophs
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What do lactotrophs secrete?
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prolactin
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Describe the regulation of prolactin secretion from lactotrophs
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inhibited by dopamine
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What cells are lactotrophs frequently associated with?
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gonadotrophs
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Describe the effect of pregnancy on lactotrophs
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they increase in size and number during pregnancy
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What causes lactotrophs to increase in size and number during pregnancy?
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Increasing circulation of estrogens
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Describe the effect on lactotrophs after weaning
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most lactotrophs undergo apoptosis, but some cells remain behind
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Compare the size of pituitary glands in women compared to men
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They tend to be larger in women (mainly multiparous women) than in men due to lactotroph development during pregnancy
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How is dopamine delivered to the pituitary
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via the infundibular stalk
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Describe the effect on lactotrophs if infundibular stalk damage occurs
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lactotrophs will undergo hyperplasia and hyperprolactinemia
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How do lactotrophs differ from all other cells in the pituitary?
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When infundibular stalk damage occurs, the secretion of these cells go up. Infundibular stalk damage results in a decline in secretion by all other cells
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What is the common link between all 4 types of basophils located within the adenohypophysis?
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all 4 basophils, the hormone secreted (or the precursor to the hormone secreted) consists of a glycoprotein containing sulfated carbohydrate chain
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Name 3 types of basophils located in the adenohypophysis
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gonadotrophs, corticotrophs, thyrotrophs
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What do gonadotrophs secrete?
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follicle stimulating hormone and luteinizing hormone
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Describe the pattern of FSH and LH secretion from the gonadotrophs
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concentration varies from cell to cell as well as depending on the reproducting status of the individual
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What is the role of FSH in females?
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stimulates growth and development of the follicle
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What is the role of LH in the female?
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stimulates ovulation and development of the corpus luteum
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What is the role of FSH in males?
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stimulate the activity of Sertoli cells
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What is the role of LH in males?
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stimulates synthesis of testosterone
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Describe the regulation pattern of gonadotrophs
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stimulated by gonadotropin releasing hormone
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Describe the location/staining/shape the gonadotroph
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located scattered throughout the pars distalis, stains intensely basophilic, and they are ovoid
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What do thyrotrophs secrete
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thyrotropin
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What is another name for thyrotropin
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thyrotropin stimulating hormone
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What is the function of TSH?
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stimulates synthesis and secretion of thyroxine and triiodothyronine by the thyroid gland
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Describe the regulation pattern of TSH
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stimulated by thyrotropin releasing hormone from the hypothalamus
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Where are thyrotrophs typically located within the adenohypophysis?
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anteromedial
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Describe the staining pattern/shape of thyrotrophs
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large angular cells with intensely-staining small granules
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What do corticotrophs secrete?
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ACTH (adrenocorticotropic hormone)
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What is the function of ACTH?
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regulates the activity of the cortex of the adrenal gland
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What hormones does ACTH indirectly regulate synthesis and secretion of?
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glucocorticoids, mineralocorticoids, and adrenal androgens
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Describe the long-term effects of ACTH stimulation on the adrenal gland cortex
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hypertrophy, hyperplasia, and enzyme synthesis
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Describe the effect on the adrenal gland of ACTH deficiency
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atrophy of the parts that synthesize adrenal androgens and glucocorticoids
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How is ACTH synthesized?
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by cleavage of a glycosylated precursor (POMC)
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Describe the role of POMC
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contains several biologically active peptides which can be fragmented in a variety of ways to create a variety of hormones
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Describe the regulation pattern of corticotrophs
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stimulated by corticotropin releasing hormone.
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Where is corticotropin releasing hormone located and what does it do?
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synthesize by the hypothalamic neurons and it stimulates synthesis of POMC and secretion of ACTH from corticotrophs
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Describe the location/shape of corticotrophs in the adenohypophysis
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located at the medial aspect of the pars distalis. Tend to be large and triangular or ovoid
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What are chromophobes
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cells which do not contain secretory granules
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Describe the cellular composition of the pars intermedia
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consists of stellate/follicular cells as well as a few basophils
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What is the primary basophil of the pars intermedia
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melanotrophs
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What do melanotrophs secrete?
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melanocyte stimulating hormone
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What is the precursor to melanocyte stimulating hormone?
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POMC
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How are melanotrophs and corticotrophs different?
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melanotrophs require a second protease to cleave the POMC precursor into smaller fragments
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Describe the histological appearance of melanotrophs
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similar to corticotrophs and often confused as such
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Name the most common cells of the adenohypophysis
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somatotrophs
lactotrophs thyrotrophs gonadotrophs corticotrophs melanotrophs chromophobes |
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How are neurohormons secreted from the brain?
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Via the neurohypophysis (crosses the blood-brain barrier)
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What are pituicytes?
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glial cells associated with the unmyelinated axons of the neurohypophysis
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Describe the key components of the neurohypophysis
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-unmyelinated axons of the hypothalamic neurons
-pituicytes |
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How can the nuclei in the neurohypophysis be classified as pituicyte or neuron?
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will always be pituictye since the cell bodies of the hypothalamic neurons are located in the hypothalamus
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Name the two types of neurons which project from the hypothalamus to the neurohypophysis
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large neurons and small neurons
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What do large neurons secrete in the neurohypophysis?
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oxytocin and vasopressin
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What do the small neurons from the hypothalamus secrete in the neurohypophysis?
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releasing or inhibiting factors for the adenohypophysis cells
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Other than size alone, how do large and small neurons from the hypothalamus differ?
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Cell body location within the hypothalamus, and where their axons terminate in the pars distalis
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What do large neurons from the hypothalamus secrete?
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oxytocin and vasopressin
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Where do the axons from the large neurons in the hypothalamus terminate?
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In the pars nervosa
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How are the precursors to oxytocin and vasopressin synthesized?
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by ribosomes attached to the RER of the magnocellular neurons in the hypothalamus. These then go through the Golgi, and become packaged into vesicles destined for the nerve terminals in the pars nervosa
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What are Herring bodies?
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Aggregates of vesicles containing precursors to oxytocin and vasopressin in the axons destined for the nerve terminal/capillary junction
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What do the small neurons from the hypothalamus secrete?
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inhibiting, releasing factors
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Where do the axons from the small neurons from the hypothalamus terminate?
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on the infundibular stalk and the median eminence
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Describe the primary blood source of the pars distalis
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venous blood from the infundibulum
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What is the hypophyseal portal system?
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The blood system that allows the neurohormones to enter the pars distalis and cross the blood-brain barrier
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What are the 2 sets of arteries that supply the pituitary gland?
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the inferior hypophyseal artery and the superior hypophyseal artery
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Describe the supply pattern of the inferior hypophyseal artery
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Feeds the pars nervosa and the pars intermedia. Secretes vasopressin and oxytocin here
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Describe the supply pattern of the superior hypophyseal artery
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Supplies the median eminence and the infundibular stalk. Releasing/inhibiting factors released here
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How does the pars distalis get the neurohormones from the hypothalamus?
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the blood from the superior hypophyseal artery collects into the hypophyseal portal veins in the pars tuberalis and drains to the pars distalis
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Describe the venous drainage of the pars nervosa and the pars distalis
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Both drain to veins which draing to large venous sinuses adjacent to the capsule of the pituitary
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Describe the feeback control of the pituitary hormones
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Effector organs send feedback signals to either the pituitary or the hypothalamus that certain hormones are/are not needed
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How does feedback inhibition change the pituitary
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Changes the appearance and functionality of certain cells
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