Histology of endocrine system


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Histology of endocrine system

  1. 1. Assoc. Prof. Dr. Karim Al-Jashamy IMS/MSU 2010
  2. 2. The Endocrine System  Controls many body functions • exerts control by releasing special chemical substances into the blood called hormones • Hormones affect other endocrine glands or body systems • Derives its name from the fact that various glands release hormones directly into the blood, which in turn transports the hormones to target tissues, no need to ducts
  3. 3.  Uses chemical signals for cell to cell communication.  Coordinates the function of cells  Response to an endocrine signal occurs within minutes to hours  Exocrine glands - transport their hormones to target tissues via ducts.
  4. 4. Pituitary Gland(hypophysis)  Located at the base of the skull  Anterior and Posterior lobes  Portal connection from the hypothalamus
  5. 5. Flow of Blood to Anterior Pituitary  Controlling hormones enter blood  Travel through portal veins  Enter anterior pituitary at capillaries
  6. 6. Hypophysis = Pituitary Gland Compound gland – 2 parts from different embryonic sources Epithelial part – pouch pinched off from roof of mouth Neural part – from downgrowth brain floor (diencephalon)
  7. 7. Pars Distalis (anterior Lobe) Parenchyma: anastomosing cords of epithelial cells Chromophobe cells: smaller than chromophil cells; may be inactive form Chromophil cells: Cytoplasm granular; more distinct than chromophobe cells 2 types of chromophil cells: acidophil (alpha cells); basophil (beta cells) Acidophils: specific, spherical granules of uniform size Basophils: appreciably larger; fewer granules
  8. 8. Pars Tuberalis Cell groups & cords Cells finely granular Cysts with colloid not uncommon in this part Pars Intermedia Narrow, definite region but ill defined in humans Cysts common; filled with colloid or hyaline material
  9. 9. Neurohypophysis Distinct cell type: pituicyte Resemble neuroglia cells 4 subtypes: many contain fatty droplets, granules, pigment Unmyelinated nerve fibers from the hypothalamus majority end in pars nervosa
  10. 10.  The pars distalis (A) and the pars intermedia (B) of the adenohypophysis (anterior pituitary) and the pars nervosa (C) of the neurohypophysis (posterior pituitary) can be observed.  The pars distalis secretes Growth Hormone (GH), Thyroid-stimulating hormone (TSH), Adrenocorticotrophic hormone (ACTH), Follicle- stimulating hormone (FSH), Lutenizing hormone (LH),and Prolactin.  The pars intermedia secretes Melanocyte-stimulating hormone (MSH).  The pars nervosa stores ADH and Oxytocin which were secreted by the hypothalamus.
  11. 11. At higher magnifications the dark staining chromophils ( A) and the very light staining chromophobes (B) are easily distinguished NEUROHYPOTHYSIS - PARS NERVOSA This region of the pituitary is non secretory. Its cells are neuroglial-like pituicytes (C).
  12. 12. pars intermedia A = pars distalis of adenohypophysis c= colloid vesicle in pars intermedia b = basophils I = pars intermedia col = colloid vesicles N = pars nervosa of neurohypophysis
  13. 13. pars intermedia a = acidophil b = basophil bv = blood vessel c = chromophobe 1 = cell cluster consisting of chromophobes 2 = cell cluster consisting mainly of acidophils asterisk = connective tissue between cell clusters a = acidophils b = basophils bv = blood vessel
  14. 14. Thyroid Gland
  15. 15. Thyroid Gland • Fibro-elastic capsule – delicate septa & trabeculae. • Septa mark off lobules. • Lobules not completely separated • Stroma: areolar & reticular C.T. – highly vascular • Follicle – closed, single-layered epithelial sac (50 – 500 μ dia.) • Size dependent on amount of stored secretion •~ 20 million follicles in thyroid gland •Epithelium: simple cuboidal (cell height uniform) •Cytoplasm finely granular; basophilic (pale) •Blood vessels & lymphatics: intimate plexuses around follicles. Arterio- venus anatomoses common •Thyroxin: in veins & lymphatics (most in veins)
  16. 16. Colloid fills follicle Rich in nucleoproteins Contains: thryoglobulin & enzymes
  17. 17. Follicle = sac of stored hormone (colloid) surrounded by follicle cells that produced it – T3 & T4 • Inactive cells are short between cells called parafollicular cells produce calcitonin
  18. 18. Formation, Storage and Release of Thyroid Hormones • Thyroid hormones are synthesized from iodine and tyrosine within a large glycoprotein molecule called thyroglobulin (TGB) and are transported in the blood by plasma proteins mostly thyroxine-binding globulin (TBG).
  19. 19. Actions of Hormones from Thyroid Gland T3 & T4 – thyroid hormones  responsible for our metabolic rate, synthesis of protein, breakdown of fats, use of glucose for ATP production Calcitonin  responsible for building of bone & stops reabsorption of bone (lowers blood levels of Calcium)
  20. 20. Parathyroid Humans: 4 brownish glands, 2 attached to back of each thyroid lobe Glands are ovoid Size of an apple seed
  21. 21. Framework • Delicate fibro-elastic capsule • Septa divide each gland incompletely (lobules) • Invasion of septa begins after birth; continues with age
  22. 22. Adrenal Glands
  23. 23. zona thin, outermost zone glomerulosa zona Cortex thick, middle zone fasiculata zona thin, inner zone reticularis Medulla catecholamines (epinephrine and norepinephrine)
  24. 24. The outermost zone is the zona glomerulosa. Cells within this zone tend to be columnar in shape and are arranged in irregular cords. cells adjacent to the capsule are arranged in quite regular “ The zona fasiculata is the middle and largest of the three zones in the cortex. Cells in the fasiculata are polyhedral and usually have a foamy appearance due to abundant lipid droplets. They also are arranged in distinctively straight cords that radiate toward the medulla. The innermost zone of the cortex is the zona reticularis. Cells within this zone are arranged in cords that project in many different directions and anastomose with one another.