The endocrine system

Transcription

1 The endocrine system Overview I. Pituitary II. Adrenals III. Pancreas IV. Thyroid V. Parathyroids VI. Ovaries, testis fenestrated capillaries are general structures

2 Major human endocrine glands and some of their hormones Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings

3 Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings

4 Martini, Timmons Anatomia Umana, IV Ed. ACROMEGALY CRETINISM GOITER Addison s disease Cushing's syndrome

5 Hyperthyroidism, excessive secretion of thyroid hormones Can cause Graves disease in humans Copyright 2005 Pearson Education, Inc. publishing as Benjamin Cummings

6 The pituitary gland, hypophysis The master gland, a pea-sized body attached to the base of the brain, It lies within the pituitary fossa of the sphenoid bone, where it is covered superiorly by a circular diaphragma sellae of dura mater Neurohypophysis, the median eminence, infundibular stem and neural lobe or pars posterior Adenohypophysis pars anterior (pars distalis) and the pars intermedia. - Both include parts of the infundibulum-

7 The endocrine secretory activities of the pituitary gland

8 the pituitary gland (trichrome-stained). A, The endocrine cells of the adenohypophysis B, The neurohypophysis (right), with nerve fibres and pituicytes.

9 The pituitary gland development neurohypophysis (post. lobe) develops as outgrowth of diencephalon and forms: 1) pars nervosa (posterior lobe); 2) infundibulum

10 The pituitary gland development adenohypophysis (ant. lobe) develops from Ratcke s pouche (oral ectoderm) and forms: 1) pars distalis (posterior lobe); 2) pars tuberalis and pars intermedia

11 The pituitary gland vascularization Hypothalamo-hypophyseal portal system 1. primary capillary plexus (base of infundibulum/ hypothalamus) 2. veins to anterior lobe 3. secondary capillary plexus Function: transports neurohormones a. releasing hormones b. inhibiting hormones

12 The pituitary gland, adenohypophysis pars anterior (pars distalis) 1. Chromophobes & chromophils 2. Basophils a. gonadotrophic cells i) FSH, follicle-stimulating hormone promotes the formation of ova or sperm. ii) LH, luteinizing hormone stimulates ovulation in females and the synthesis of androgen in males. b. thyrotropic cells iii) TSH, thyroid-stimulating hormone. c. corticotrophic cells iv) ACTH, adrenocorticotropic hormone stimulating the adrenal cortex

13 The pituitary gland, adenohypophysis pars anterior (pars distalis) 3. Acidophils d. somatotropic cells v) GH, growth hormone stimulates growth e. mammotropic cells vi) PRL

14 The pituitary gland, neurohypophysis 1. pituicytes 2. neurosecretory cells 3. ~100,000 unmyelinated axons from hypothalamus

15 Neurohypophysis

16 Neurohypophysis vii) vasopressin / ADH, antidiuretic hormone a. contraction of smooth muscle in arteries b. increase reabsorption of H2O in collecting tubules viii) oxytocin a. contraction in pregnant uterus b. stimulates the ejection of milk into the ducts of the breasts.

17 Major calyces renal cortex renal pelvis calyces renal medulla ureter

18 Renal medulla

19 GLOMERULUS

20 Adrenals (suprarenal glands) ductless glands situated above the kidneys. Each consists of a core region (adrenal medulla) secreting epinephrine and norepinephrine, and an outer region ( adrenal cortex) secreting corticosteroids. A. Overview 1. adrenal cortex a. steroids 2. adrenal medulla a. E & NE 3. stroma a. capsule b. trabeculae c. reticular fibers 4. extensive capillary plexuses

21 Adrenal cortex zona glomerulosa a. 15% of adrenal cortex

22 Adrenal cortex zona glomerulosa b.clusters of cells c. mineralocorticoids (aldosterone) Function: increase DCT (distal convoluted tubule) absorption of Na+ DCT is a portion of kidney nephron between the loop of Henle and the collecting duct system.

23 Adrenal cortex zona fasciculata a. 65% of adrenal cortex b. cells in cords c. many lipid droplets in cytoplasm d. glucocorticoids (cortisol and corticosterone) Function: i) influence CHO metabolism; ii) suppress immune response CHO= carbohydrate

24 Adrenal cortex zona reticularis a. 7% of adrenal cortex b. irregular cords in network c. lipofuscin granules d. androgens Function: little effect vs. testicular hormones

25 Adrenal medulla 1. cells in cords 2. secrete epinephrine and norepinephrine (E & NE) 3. innervated by preganglionic sympathetic (myelinated) axons Look for: Preganglioni sympathetic fibers Blood vessels

26 adult suprarenal gland (adrenal gland) zona granulosa (ZG), zona fasciculata (ZF), zona reticularis (ZR), and the highly vascular medulla (M).

27 adrenal gland FC L G F R C M V

28 adrenal gland FC G 1 C F 2 R 3 M 4 V

29 zona granulosa (ZG) 1 FC ZG F

30 zona fasciculata (ZF) zona reticularis (ZR) 2 ZF c c ZR

31 Zona Fascicolata (ZF) S A B

32 Zona Reticularis (ZR) 3 sinusoid

33 Medulla (M) 4 * * * * *

34 Pancreatic endocrine tissue Cluster of cells in cords 1. network of fenestrated capillaries Islet of Langerhans

35 Pancreas islet vessels V * * * V V

36 Pancreas endocrine cells

37 Pancreatic endocrine tissue Cluster of cells in cords A cells: glucagon, incr. blood sugar B cells: insulin, decr. blood sugar D cells: somatostatin, produced in pituitary too: inhibits A & B cells E cells: unknown function [immunohistochemistry for glucagon cells] [immunohistochemistry for insulin cells]

38 Thyroid 1. anterior to larynx 2. two lobes connected by isthmus 3. well vascularized Follicle cells 1. squamous to columnar epithelium a. squamous = inactive b. columnar = active 2. colloid a. thyroxine / T4 b. triiodothyronine / T3 Function: stimulates rate of metabolism. Influenced by thyroidstimulating hormone (TSH) Parafollicular cells 1. calcitonin Function: decr. blood Ca++

39 human thyroid follicles ( * ) * * * * reticular connective tissue

40 human thyroid follicles CT colloidal thyroglobulin * calcitonin-secreting C cells follicular epithelium

41 thyroid colloid ( * ) * * *

42 Thyrocyte (T) and basal membrane (BM) T BM

43 calcitonin-secreting C cells C1 C2

44 Parathyroid The parathyroid glands are four or more small glands, about the size of a grain of rice, located on the posterior surface (back side) of the thyroid gland

45 Parathyroid

46 Parathyroid gland oxyphil cells chief cells (or a "zymogenic cell") release a precursor enzyme. Two types of chief cells: -gastric chief cell (or "peptic cell") is a cell in the stomach that releases pepsinogen, rennin and gastric lipase enzymes, which help digest triglycerides into free fatty acids and di- and monoglycerides. -the parathyroid chief cell of the parathyroid gland. It produces and secretes parathyroid hormone.

47 Parathyroid glands Parenchyma 1. oxyphil cells a. larger, polygonal cells unknown function

48 Parathyroid glands Parenchyma chief cells a. pale, acidophilic cytoplasm b. secretes parathyroid hormone Funcion: incr. blood Ca++ levels