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28 Cards in this Set
- Front
- Back
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Endocrine System
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*Communicate information (via hormones). The hormones are carried to their destinations via:
- connective tissue spaces - vascular tissue *Hypothalamus - coordinates most endocrine function *Three main classes: 1. steroids 2. small peptides, proteins, glycoproteins 3. amino acid analogues and derivatives |
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two main classes of hormone receptors
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1. Cell Surface Receptors:
- hormones cell impermeant (can't penetrate cell membrane) (ex: peptide hormones or catecholamines) - second messanger pathway (cAMP, IP3, DAG, calcium channels. These are small intracellular molecules that amplify the signal) 2. Intracellular receptors (target inside of cell): - mainly nuclear - hormones cell permeant (can easily penetrate both plasma and nuclear membranes)(steroids and thyroid hormones) - gene expression |
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Major Endocrine Organs
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*Pituitary gland (hypophysis)
*Pineal gland - both of these glands are in the brain *Thyroid gland *Parathyroid glands *Adrenal glands |
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Pituitary gland (hypophysis)
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- located under hypothalamus
- Two Components (it's bilobed): 1. Anterior (adenohypophysis) - portion of Pars Distalis - glandular - ectodermal (Rathke's pouch) 2. Posterior (neurohypophysis): - portion of Pars Nervosa - neural secretory - neuroectoderm (infundibulum) |
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Pituitary gland development
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-both of these portions come from distinct portions of the embryo
*Anterior - comes from ectoderm of pharynx (Rathke's pouch) *Posterior - comes from neuroectoderm (infundibulum) |
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Pituitary gland blood supply
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Two Sets:
1. Superior hypophyseal arteries: - from internal carotid and posterior communicating artery - two capillary beds (fenestrated): primary capillary plexus and secondary capillary plexus 2. Inferior hypophyseal arteries: - internal carotid arteries - supplies pars nervosa (most of the anterior lobe of the pituitary gland has no direct arterial supply) *break into 3 capillary beds which spread the hormones throughout the body |
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Hypothalamo-hypophyseal system (hypothalamus + pituitary)
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Three sites where hormones enter capillary beds:
1. Secretory neurons- hypothalamus 2. Dorsal/Ventral Medial and Infundibular 3. Pars distalis (anterior pituitary) |
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Anterior Pituitary Gland- Pars Distalis
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- cords of epithelial cells with interspersed capillaries
- cells arranged in cords with capillaries - these cells respond to signals from the hypothalamus and synthesize and secrete a number of pituitary hormones |
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Pars Distalis Cells
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Acidophils:
*Somatotrophs - growth hormones (GH) *Lactotrophs - prolactin (promotes mammary gland development; initiates milk formation) Basophils: *Corticotrophs - Adrenocorticotrophic hormone (ACTH) - Melanocyte-stimulating hormon (MSH) *Thyrotrophs - Thyroid-Stimulating Hormone (TSH) *Gondotrophs - FSH and LH - six main groups of hormones being produced by two classes |
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Pars Tubularis
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*funnel-shaped region
*the pars tubularis surrounds infundibulum (wraps around it- it is an extention of the anterior lobe) *highly vascularized (lots of capillaries) - Hypothalmohypopyseal system *cells are arranged in cords *secrete gonadotropins (FSH and LH- this is the site where these are produced) |
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Pars Intermedia
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*surrounds small cystic crypts that represent the residual lumen of Rathke's pouch (Rathe's rudiment)
*Parenchymal follicle cells *Unknown function? Rudiment? *Cortiocotroph cells - MSH produced? |
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Posterior Pituitary (neurohypophysis)
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Components:
1. Pars nervosa 2. Infundibulum -The posterior pituitary is NOT an endocrine gland - storage site (for neurosecretions) |
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Posterior Pituitary- Pars Nervosa
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*Neural lobe of pituitary gland
- 100K nonmyelinated neurosecretory axons and nerve endings - Unique axons (b/c they don't synapse with anything) *Herring bodies (vessels)- they are collections of neurosecretory granules (dilated portions of the axon near the terminals) *Pituicytes (like astrocytes; supportive cells of the posterior pituitary neurons) *Hormones (2): 1. Antidiuretic hormone (ADH)- H2O regulation 2. Oxytocin- stimulates mammary gland cells to eject milk and stimulates contraction of smooth muscle during pregnancy |
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Adrenal Gland
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*Superior to the Kidney
*3 regions: - capsule (outer dense CT) - cortex (steroid secreting portion) - medulla (catecholiamine-secreting portion) - a lot of blood vessels running into adrenal gland all over - vein drains medulla |
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Adrenal Cortex
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*Three Regions:
- Zona Glomerulosa - Zona Fasciculate - Zona Reticularis |
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Zona Glomerulosa
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-15% of cortical volume; most distal
*the cells of glomerulosa secrete mineralocorticoids (regulate Na and K homeostasis and water balance) - secretes aldosterone |
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Zona Fasciculata
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-65%; middle
*cells in fasciculata are large and polyhedral arranged in long cords and have high lipid content *spongiocytes (in fasci.)- make glucocorticoids (regulate glucose and fatty acid metabolism) - ACTH regulates secretion of the zona fasciculata |
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Zona Reticularis
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-7%; next to medulla
*reticularis cells are smaller, stain darker, arranged in random cords, make androgens |
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Adrenal Gland- Medulla
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*Chromaffin cells (irregular short cords):
- numerous granules - sympathetic nerve endings - modified nerve cells - two hormonal products: epinephrine (80%) norepinephrine (NE-producing cells have larger and darker staining granules than E-producing cells) |
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Adrenal Gland- development
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*Embryologically distinct:
- Cortex --> Mesodermal cells - Medulla --> Neuroectodermal *Fetal Cortex makes up 70% during gestation |
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Adrenal Gland- vascularization
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*Three patterns:
- Capsular capillaries (supply the capsule) - Fenestrated cortical sinusoid capillaries (supply the cortex) - Medullary arterioles (traverse the cortex and bring arterial blood to the: *medullary capillary sinusoids) *Medulla- dual supply *Central Meduallary vein *Sponge effect- smooth muscle assoc. with these veins contracts and pushes blood out of adrenal gland (so there's a surge of hormone release. ex: adrenaline rush by this squeezing of adrenal gland) *blood supply: from arteries directly into medulla or from cortex |
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Adrenal Disorders
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*Cushings- adrenal hyperfunction; increase in glucocortocoids
*Addison's- hypofunction of adrenal hormones; weight loss; fatigue; darkening of skin |
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Pineal Gland
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*Involved in both endocrine and neuroendocrine
*Neural development (from neuroectoderm) *Two parenchymal cell types: 1. Pinealocyte (clustered cells; often have cytoplasmic extentions (secretory-types cells)) 2. Interstitial (glial) cells- supportive cells *Brain Sand (corpora arenacea)- clumps of calcium carbonate; clumps increase with aging *Secrete melatonin (regulates reproductive function in mammals) *Daily rhythm |
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Thyroid Gland
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*Bilobed
*Thin CT capsule with trabeculae *Produce thyroxine (T4) and triiodothyronine (T3)- hormones involved in growth and development *Follicle- functional unit - simple epithelium - contains colloid (gelatinous substance; precursor for hormones) *Highly vascularized |
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Thyroid Gland- Cell Types
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*Simple epithelium:
- Follicle cell- can store them (regulate T3 and T4) - Parafollicle cell- in between follicles; involved in production of hormone calcitonin |
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Thyroid Diseases
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*Hyperthyroidism- hypothermia; dry skin; puffy skin; bulging eyes
- Graves Disease (excessive amts of thyroid hormones released) *Hypothyroidism: - Hashimoto's disease (autoimmune disease; low levels of circulating thyroid hormone stimulate release of excessive amounts of TSH, which causes hypertrophy of the thyroid) |
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Parathyroid
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*4 small glands- located on thyroid
*Derived from pharyngeal pouch *Capsule *Cells in cords *Adipose with age *Parathyroid Hormone: osteoclast stimulation |
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Parathyroid Cell Types
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- Chief (secretory granules)- help regulate calcium by secreting PTH
- Oxyphil- larger cells but small number of them; they get replaced by adipose tissue over time. |
