Endocrine glands and liver213 Practice

Endocrine glands – cells producing signal molecules

• Arrangement:

• discrete organs – (thyroid gland) • clusters of cells (gonads, pancreas)• singly distributed cells: DNES in GIT

• endocrine tissue, endocrine glands = epithelial tissue (glandular form)

• fenestrated capillaries

Hormones– chemical structure – 4 classes. Corresponding cell morphology

● Small peptides, proteins, glycoproteinyhypothalamus, hypophysis, thyroid gland, parathyroid

gland, pancreas, DNES● Amino acid derivates or analogues

hypothalamus (dopamin), medulla of adrenal gland, DNES (serotonin)

● Steroids: ovaries, testes, cortex of adrenal gland● T3/T4 (thyroxine) - thyroid gland

DNES(diffuse neuroendocrinne system)

• Regulation of GIT secretion, motility and water and electrolyte metabolism (gastrin, secretin, GIP, cholecystokinin, motilin, VIP, serotonin, somatostatin, glucagon, substance P, ghrelin)

Neuroendocrine cells in smal intestine

Thyroid gland

Thyroid gland

• Follicles - content of colloid (thyroglobulin) – structural unit of the thyroid gland

• Cubic cells -follicular – thyroxine (T4) and tri-iodotyrosine (T3)

• Function: T3/T4 stimulates the oxidative phosphorylation within mitochondria ( resorption in gut, lipid metabolism, growth of the body, development of CNS

• Parafollicular cells– calcitonin –decrease of Ca level in blood –storage into bone and release into urine.

Follicular and parafollicular cells (C)

Secretion of thyroxine

• Thyroglobulin synthesis (RER, Gc)• Absorption of iodide from blood – active

transport• Iodide activation and its bound to AA tyrosine

on thyroglobulin (within colloide)• Thyroglobulin resorption and its break-up

within lysosomes. Release of T3 and T4

Thyroid gland

Suprarenal glands

Suprarenal gland

Suprarenal gland

• Medulla:

• Epinephrin (80%)• Norepinephrin (20%)

• Reaction to stress – Increase of blood pressure, frequency of heart

Cells of cortex

• SER• Lipids droplets• Mito with tubular cristae• No secretory granules• Function – transcriptional

factors – receptor in cytoplasma – transported into the nucleus

Suprarenal gland - medulla

Pancreas

• Exocrine gland (serous) with endocrine gland (islets of Langerhans)

• Difference from parotid gland: no striated ducts, intercalated ducts are longer, presence of intraacinar cells

• Presence of islets of Langerhans

Pancreas

• Exocrine gland – acinar– enzymes for digestion

• Endocrine gland – islets of Langerhans – cords of cells- controls of glucose level in blood and function of GIT

Pankreas

● A-cells – glucagon● B-cells – insulin● D-cells –

somatostatin● F-cells –

pancreatic polypeptide

● D-cells – somatostatin

F-cells – pancreatic polypeptideB-cells – insulinD-cells – somatostatinF-cells – pancreatic polypeptide

Islet of Langerhans - insulin

Islet of Langerhans – B cell

Islet of Langerhans - glucagon

Islet of Langerhans - somatostatin

Liver

Hepatic lobule - polygonal mass of hepatocytes, separated by connective tissue. Central vein in the centre of lobule Portal lobule – portal

trias in the centre(bile duct, vein, and artery)

Hepatic acinus: Heterogenity in the

enzyme content It depends on

oxygen saturation and concentration of nutriens in the blood

Structure

Plates formed from hepatocytes – radial disposition – spongy-like structure

Limiting plate – on the lobular periphery Hepatic sinusoids – discontinuous capillaries Kupffer cells (phagocytes)

Hepatocytes

Vascular space (baso-lateral) – brush border, space of Disse between hepatocyte and endothelial cell

Bile canaliculus – apical surface – microvilli and tight junctions – between two hepatocytes – prevent the return of bile back to blood

Hepatocyte function

Proteosynthesis – blood proteins (except for immunoglobulins): RER, GA

Metabolism of glucose: Glycogen (SER) Metabolism of lipids: SER and RER, GA Metabolism of xenobiotics: SER (microsomal

fraction) - cytochrome P450, peroxisomes (peroxidase)

Bile ducts

Bile canaliculus Bile ductiles (Hering´s) bile ducts – simple cuboidal

epithelium Interlobular bile ducts and wider – simple columnar

epithelium

Liver• Hepatocytes - histochemical

demonstration of ceruloplasmin • Hepatocytes: PAS

reaction - glycogen