16

• What is the primary focus of Module 16?

  Histology of the Endocrine System
• What are students expected to reflect on regarding the endocrine system?

  The relevance of the endocrine system
• What is an endocrine gland?

  A ductless gland releasing secretions directly
• What are the three major types of hormones produced by endocrine glands?

  Steroids, proteins, and neurotransmitter substances
• How does the ultrastructure of endocrine cells relate to hormone production?

  It mirrors the type of hormone produced
• What characterizes steroid hormone-producing endocrine cells?

  Abundant smooth endoplasmic reticulum
• What is the appearance of the cytoplasm in steroid hormone-producing cells?

  Stains acidophilically
• What is the role of the rough endoplasmic reticulum in protein hormone-producing cells?

  It synthesizes hormones actively
• What are the two categories of cells in the pars distalis of the adenohypophysis?

  Chromophils and chromophobes

  
• How do chromophils and chromophobes differ in staining?

  Chromophils stain with eosin or hematoxylin
• What hormones are synthesized in the adenohypophysis?

  ACTH, TSH, LH, FSH, PRL, GH, MSH
• What does the neural lobe of the neurohypophysis contain?

  Unmyelinated axons and pituicytes
• What are Herring Bodies?

  Accumulations of neurosecretory material

  
• What hormones are stored and released by the posterior pituitary?

  Oxytocin and ADH
• What surrounds the thyroid gland?

  A true connective tissue capsule
• What is the structural unit of the thyroid gland?

  The follicle
• What hormones does the thyroid gland secrete?

  Thyroxine (T4) and triiodothyronine (T3)
• What characterizes the parathyroid gland's structure?

  Delicate connective tissue capsule with septa
• What are the three cell types in the parathyroid gland?

  Parathyroid cells, oxyphil cells, transition cells

  
• What hormone does the parathyroid gland secrete?

  Parathyroid hormone (PTH)
• What are the two parts of the adrenal glands?

  Cortex and medulla

  
• What does the adrenal cortex produce?

  Steroids
• What hormones are produced by the zona glomerulosa?

  Aldosterone and corticosterone

  
• What is the function of the zona fasciculata?

  Produces cortisone and cortisol
• What do chromaffin cells in the adrenal medulla produce?

  Catecholamines (epinephrine and norepinephrine)
• What is the structure of the pancreas?

  A composite gland with exocrine and endocrine functions

  
• What are the pancreatic islets also known as?

  Islets of Langerhans
• What hormone do beta cells in the pancreas produce?

  Insulin
• What does the pineal gland secrete?

  Melatonin
• What is a major identification feature of the pineal gland?

  Acervulus (corpora arenacea)
• What are the two cell types in the pineal gland?

  Pinealocytes and astrocytes
• How does the number of corpora arenacea change with age?

  It increases with age
• What are the effects of hormones secreted by the pituitary gland?

  • Growth Hormone (GH): Stimulates growth
  • Prolactin (PRL): Stimulates milk production
  • Thyroid Stimulating Hormone (TSH): Stimulates thyroid activity
  • Adrenocorticotropic Hormone (ACTH): Stimulates adrenal cortex
  • Follicle-Stimulating Hormone (FSH): Stimulates ovarian follicles
  • Luteinizing Hormone (LH): Stimulates ovulation
  • Antidiuretic Hormone (ADH): Regulates water balance
  • Oxytocin: Stimulates uterine contractions
  • Melanocyte-Stimulating Hormone (MSH): Stimulates melanin production
• What are the characteristics of endocrine glands?

  • Ductless glands
  • Release secretions directly into the bloodstream
  • Richly vascularized
  • Cells may have neural, epithelial, or epithelioid characteristics
• What are the histological characteristics of steroid hormone-producing cells?

  • Abundant smooth endoplasmic reticulum
  • Numerous mitochondria with tubular cristae
  • Lipid droplets in cytoplasm
  • Cytoplasm stains acidophilically
• What are the histological characteristics of protein hormone-producing cells?

  • Abundant rough endoplasmic reticulum and Golgi apparatus
  • Cytoplasm stains basophilic when synthesizing hormones
  • Membrane-bound secretory granules present
• What are the zones of the adrenal cortex and their functions?

  1. Zona glomerulosa: Produces aldosterone and corticosterone
  2. Zona fasciculata: Produces cortisone and cortisol
  3. Zona reticularis: Produces estrogen and testosterone

  
• What are the cell types in the parathyroid gland and their characteristics?

  • Parathyroid cells: Polyhedral shape, pale eosinophilic cytoplasm
  • Oxyphil cells: Larger, darker-staining nuclei, appear after childhood
  • Transitional cells: Intermediate characteristics, not easily distinguished

  
• What are the structural features of the thyroid gland?

  • Surrounded by a connective tissue capsule
  • Follicles with colloid-filled cavities
  • T thyrocytes are simple cuboidal epithelial cells

  
• What are the functions of the pancreas?

  • Endocrine: Produces insulin and glucagon
  • Exocrine: Produces digestive enzymes