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135 Cards in this Set
- Front
- Back
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4 Mechanisms by which cells communicate with each other:
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-Direct contact
-Autocrine -Paracrine -Endocrine |
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How can cells directly contact each other and communicate?
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Through gap junctions which can exchange small molecules
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What does the Adenohypophysis develop from?
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An ectodermal upgrowth from the roof of the primitive mouth cavity.
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What is the upgrowth called?
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Rathke's pouch
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What do cells of the anterior wall of Rathke's pouch proliferate to form?
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Pars distalis
Pars tuberalis (around the infundibulum) |
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What do the cells of Rathke's pouch that proliferate less extensively form?
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Pars intermedia
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What are the colloid-filled cysts that remain in pars intermedia?
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Remnants of rathke's pouch
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What are the 3 components that make up the Neurohypophysis?
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-Pars nervosa
-Infundibular stalk -Median eminence |
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What does the median eminence contain?
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Neurosecretory cells extending from the hypothalamus into the posterior pituitary.
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What are the support cells in the pars nervosa that support the axons from the neurosecretory cells?
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Pituicytes
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Where are the cell bodies of the neurosecretory cells that extend axons into the pars nervosa?
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In the Paraventricular and Supraoptic nuclei in the hypothalamus.
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What happens when the cell bodies in the PVN and SO nuclei are stimulated physiologically?
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They secrete hormones into the pars nervosa.
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How do neurosecretory cells in the posterior hypothalamus cause secretion in the adenohypophysis?
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By secreting releasing factors into a primary capillary plexus
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What happens when releasing hormones stimulate the adenohypophysis?
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It releases its trophic hormones into another capillary plexus to go via the blood to target tissues.
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Are the islets of langerhans and parathyroid glands under pituitary control?
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No; just controlled via metabolism changes and calcium.
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What are the 5 cell types in the Adenohyphysis?
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1. Somatotrophs
2. Lactotrophs 3. Corticotrophs 4. Gonadotrophs 5. Thyrotrophs |
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What percent of the adenohypophyseal cell population are somatotrophs?
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50%
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What do somatotrophs secrete?
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Growth hormone
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What stimulates GH release?
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GhRH
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What inhibits GH release?
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Somatostatin
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What are the effects of GH on
-Adipocytes -Hepatocytes -Somatic cells -Chondrocytes and myoblasts |
Fat: increased lipolysis
Liver: IGF1 secretion Somatic cells: protein synthesis via IGF1 Cartilage: mitosis via IGF1 |
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What does GH hyposecretion lead to in children? What is the common cause of it?
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-Short stature
-Lack of GRH |
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What does GH hypersecretion lead to in children? Adults?
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Kids - gigantism
Adults - acromegaly |
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What are 2 other names for Lactotrophs?
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-Mammotrophs
-Acidophils |
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What % of the adenohypophyseal cells are Lactotrophs?
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10-25%
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What do lactotrophs secrete?
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Prolactin
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What stimulates and inhibits Prolactin secretion?
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-Suckling/pregnancy stimulates
-Dopamine inhibits |
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What can also stimulate Prolactin secretion?
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TRH
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What is the most common pituitary tumor?
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Prolactinoma
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What does Prolactinoma lead to?
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-Galactorrhea
-Gonadal dysfunction |
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Why are Corticotrophs basophilic?
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Because they're glycosylated
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What % of adenohypophyseal cells are Corticotrophs?
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15-20%
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What do corticotrophs secrete?
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ACTH
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What does ACTH hyposecretion cause?
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Secondary adrenal insuffiency
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What is a common cause of secondary adrenal insufficiency?
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Withdrawal of a patient from prolonged cortisone or prednisone therapy.
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What is Cushing's disease characterized by?
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ACTH hypersecretion
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What are the 4 main symptoms of Cushing's?
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-Truncal obesity
-Moon facies -Hypertension -Gonadal dysfunction |
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What do gonadotrophs secrete?
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Both LH and FSH
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What can cause impaired LH/FSH secretion in women?
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-Anorexia
-Obesity -Stress -Athletic training |
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What can an X-linked disorder causing defective GnRH secretion in males lead to?
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-Eunuchoid appearance
-Tall stature due to testosterone deficiency and failure of epiphyseal plates to close |
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What is the smallest percent of the adenohypophyseal cells?
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Thyrotrophs
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What does krippendorf say inhibits TSH secretion?
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Somatostatin
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What does hypothyroidism lead to in infants? Adults?
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Infants = cretinism
Adults = myxedema (hashimotos) |
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What does increased TSH in hypothyroidism lead to?
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Goiter
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What does Hyperthyroidism lead to?
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-Goiter
-Exophthalmopathy -Dermopathy |
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What are the secretory products of the neurohypophysis?
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-Oxytocin
-ADH |
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What is the type of neuron that secretes Oxytocin/ADH?
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Magnocellular
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Is oxytocin only secreted by the posterior pit?
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No it's also secreted by uterus, placenta, testis, epididymus, etc.
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What stimulates Oxytocin secretion?
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-Suckling
-Parturition -Stress |
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What 3 cells does oxytocin affect?
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-Uterine smooth muscle cells
-Myoepithelial cells -Prostate gland |
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What does oxytocin do to uterine smooth muscle and myoepithelial cells in the lactiferous ducts?
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Contracts them
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What does oxytocin do to the prostate?
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Causes expulsion of prostatic secretions at ejaculation
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What is ADH secretion regulated by?
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Osmoreceptors in regions of the hypothalamus that do not have a bloodbrain barrier.
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When is ADH secretion increased?
Decreased? |
Increased in nausea
Decreased in alcohol consumption |
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What 2 cells does ADH act on?
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-Nephron collecting duct epithelium
-Vascular smooth muscle |
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What patients have ADH hyposecretion (central)?
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Diabetes inspidus patients
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What do patients with Diabetes insipidus urinate?
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Insipid amounts of dilute pee
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What do patients with ADH hypersecretion (siADH) urinate?
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Concentrate urine
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What does the thyroid gland develop from?
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A downgrowth of endoderm lining the floor of the pharynx
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What is the site of origin of the thyroid indicated by?
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Foramen cecum
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What extends from foramen cecum to the target final site of the thyroid?
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Thyroglossal duct
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What does the adult thyroid consist of?
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2 lobules + an Isthmus
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What are the parafollicular cells of the thyroid formed from?
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Neural crest
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What divides the thyroid into lobules?
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A thin connective tissue capsule which makes septations in it.
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What do thyroid lobules consist of?
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Several thyroid follicles
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What is a thyroid follicle composed of?
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-Simple layer of epithelial cells
-Colloid filled space |
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What type of epithelial cells are follicular cells?
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They range from squamous when inactive to columnar when active.
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What is colloid?
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The extracellularly stored secretion of follicular cells
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What does colloid consist of?
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Mostly thyroglobulin
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Are there many parafollicular cells?
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No only a few
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Do parafollicular cells contact colloid?
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No
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What do parafollicular cells look like compared to follicular cells?
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-Large
-Pale-staining |
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What do parafollicular cells secrete?
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Calcitonin
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What does calcitonin do?
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Inhibits bone resorption by osteoclasts to reduce blood calcium levels.
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Which side of a follicular cell of a thyroid follicle is apical?
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The colloid side is apical
The outside is basal |
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How are follicular cells linked? At what side?
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-Via junctional complexes
-At the apical side |
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What does TSH do when it binds its receptor?
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Stimulates Thyroglobulin gene transcription and Thyroperoxidase synthesis
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Where is the thyroglobulin mRNA translated?
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In the RER
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What happens to Thyroglobulin during transport from the RER to the golgi?
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It is glycosylated
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What happens to Thyroglobulin at the Golgi?
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It is packaged into vesicles for exocytosis into the colloid.
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How does Iodide get into follicular cells?
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By active transport via Na/I symporter at the basal membrane.
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What has to happen to iodide before it gets used?
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Oxidation to iodine
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What oxidizes iodide? Where? What is the product?
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Thyroid peroxidase; in the follicular cell. Product is Iodine
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What happens to Iodine?
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It is spit out into the colloid.
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What happens to Iodine in the colloid?
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Another molecule of Thyroid peroxidase puts iodine onto thyroglobulin.
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How does thyroid hormone on thyroglobulin get from the colloid to circulatory system when stimulated by TSH?
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By pinocytosis of colloid containing thyroglobulin back into the follicular cell.
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What happens to the bite taken up?
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It fuses with lysosomes which release enzymes to degrade thyroglobulin and release T3/T4
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How do T3/T4 get from the follicular cell into the blood?
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By diffusion
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How do T3/T4 circulate in plasma?
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Bound to TBG
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How is free hormone transported into target cells?
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By diffusion or carriers
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What happens to T4 at targets?
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It's converted into T3
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What does T3 do?
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Binds its receptor in the nucleus and then binds HRE to turn on DNA.
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What is the effect of T3?
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Stimulation of O2 consumption and Heat production by stimulation of Na/K ATPase in all cells except 3.
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What Na/K ATPase is not stimulated by T3's effects?
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That in
-Brain -Spleen -Testes |
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What are Propothyouracile, Methimazole, and Carbimazole?
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Thyroid peroxidase inhibitors used to treat hyperthyroidism
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What do excess iodide and lithium inhibit?
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Thyroglobulin proteolysis
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How would Propothyouracil affect the morphology of follicular cells?
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It would make them squamous
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How would high TSH affect the morphology of follicular cells?
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It would make them cuboidal
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What is hypothyroidism in infants? Adults?
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Infants - cretinism
Adults - myxedema |
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What is cretinism?
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Mental retardation, short stature, and puffy face and hands.
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What is myxedema?
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Chronic fatigue
Constipation Puffy face and hands |
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Treatment for hypothyroidism?
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Levothyroxine
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What is levothyroxine?
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T4
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What is hyperthyroidism?
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Graves disease
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What happens if you remove the parathyroid glands?
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1. Blood calcium decreases
2. You go into tetany 3. You die |
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How many parathyroid glands are there?
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Usually 4
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What are the 2 types of cells in PT glands? Which are more numerous? Which are bigger?
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Chief cells - more
Oxyphil cells - bigger |
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What do Chief cells secrete?
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PTH
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What do oxyphil cells secrete?
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Don't know
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What do oxyphil cells look like?
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Eosinophilic
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What regulates PTH synthesis and secretion?
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Calcium receptors
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What increases PTH secretion?
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Lack of Calcium binding its receptor.
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Why doesn't calcium binding its receptor on the parathyroids increase vesicular exocytosis of PTH?
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Because stimulus-secretion coupling in the parathyroid cells occurs via Mg2+
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What inhibits PTH gene transcription?
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High levels of vit D
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What does PTH do to bone?
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Stimulates resorption to increase blood calcium
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What does PTH do to kidney?
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Increases calcium reabsorption
Decreases phosphate reabsorption Increases Vit D activation |
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What is the result of Vit D activity?
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Increased intestinal calcium reabsorption
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What are the 4 zones of the adrenal medullae? What does each secrete?
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1. Zona glomerulosa, Aldo
2. Zona fasciculata, glucocorts 3. Zona reticularis, DHEA and glucocorticoids 4. Medulla - catecholamines |
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What do the cells in the zona glomerulosa look like?
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Clusters of small cells with little cytoplasm
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What do the glomerulosa cells secrete?
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Mineralcorticoids (aldosterone)
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What regulates secretion of the mineralcorticoids?
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The renin angiotensin system
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What is hyposecretion of aldosterone?
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Addison's disease
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What does Addison's disease lead to?
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-Hyponatremia
-Hyperkalemia -Dehydration -Hypotension |
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What does the cell arrangement in the zona fasciculata look like?
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-Arranged in long straight cords
-Separated by sinusoidal capillaries |
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What do the cells in the zona fasciculata secrete?
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DHEA + Cortisol
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What is secreted from the Zona reticularis?
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DHEA and Cortisol
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What regulates secretion of DHEA and cortisol?
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CRH and ACTH system
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What causes CAH?
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Lack of 21 hydroxylase
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What results from CAH?
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-Virilism in girls
-Increased ACTH -Hypertrophy of the adrenals |
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What do the cells in the Zona Reticularis look like?
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They are small with abundant lipofuscin granules
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What are the cells in the Adrenal Medullae?
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Pale staining chromaffin cells that are modified neurons
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What catecholamines are secreted from the medulla?
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-Epi
-Norepi |
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What exactly stimulates the secretion of Epi/Norepi from the medulla?
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The release of ACh from preganglionic sympathetic neurons
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What is Pheochromocytoma?
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A tumor of the adrenal medulla
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What are symptoms of Pheochromocytoma?
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-hypertension
-headache -sweating -palpitations -tachycardia |
